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Sample records for crystalline silicate zeolite

  1. Process for the exchange of crystalline zeolites

    SciTech Connect

    Lim, J.; Brady, M.; Humphries, A.

    1984-07-10

    This invention relates to exchanging the sodium contained in a crystalline zeolite by partially removing sodium by exchange with another cation, partially drying the exchanged zeolite and re-exchanging the dried zeolite.

  2. Final report on the safety assessment of aluminum silicate, calcium silicate, magnesium aluminum silicate, magnesium silicate, magnesium trisilicate, sodium magnesium silicate, zirconium silicate, attapulgite, bentonite, Fuller's earth, hectorite, kaolin, lithium magnesium silicate, lithium magnesium sodium silicate, montmorillonite, pyrophyllite, and zeolite.

    PubMed

    Elmore, Amy R

    2003-01-01

    This report reviews the safety of Aluminum, Calcium, Lithium Magnesium, Lithium Magnesium Sodium, Magnesium Aluminum, Magnesium, Sodium Magnesium, and Zirconium Silicates, Magnesium Trisilicate, Attapulgite, Bentonite, Fuller's Earth, Hectorite, Kaolin, Montmorillonite, Pyrophyllite, and Zeolite as used in cosmetic formulations. The common aspect of all these claylike ingredients is that they contain silicon, oxygen, and one or more metals. Many silicates occur naturally and are mined; yet others are produced synthetically. Typical cosmetic uses of silicates include abrasive, opacifying agent, viscosity-increasing agent, anticaking agent, emulsion stabilizer, binder, and suspending agent. Clay silicates (silicates containing water in their structure) primarily function as adsorbents, opacifiers, and viscosity-increasing agents. Pyrophyllite is also used as a colorant. The International Agency for Research on Cancer has ruled Attapulgite fibers >5 microm as possibly carcinogenic to humans, but fibers <5 microm were not classified as to their carcinogenicity to humans. Likewise, Clinoptilolite, Phillipsite, Mordenite, Nonfibrous Japanese Zeolite, and synthetic Zeolites were not classified as to their carcinogenicity to humans. These ingredients are not significantly toxic in oral acute or short-term oral or parenteral toxicity studies in animals. Inhalation toxicity, however, is readily demonstrated in animals. Particle size, fibrogenicity, concentration, and mineral composition had the greatest effect on toxicity. Larger particle size and longer and wider fibers cause more adverse effects. Magnesium Aluminum Silicate was a weak primary skin irritant in rabbits and had no cumulative skin irritation in guinea pigs. No gross effects were reported in any of these studies. Sodium Magnesium Silicate had no primary skin irritation in rabbits and had no cumulative skin irritation in guinea pigs. Hectorite was nonirritating to the skin of rabbits in a Draize primary skin irritation study. Magnesium Aluminum Silicate and Sodium Magnesium Silicate caused minimal eye irritation in a Draize eye irritation test. Bentonite caused severe iritis after injection into the anterior chamber of the eyes of rabbits and when injected intralamellarly, widespread corneal infiltrates and retrocorneal membranes were recorded. In a primary eye irritation study in rabbits, Hectorite was moderately irritating without washing and practically nonirritating to the eye with a washout. Rats tolerated a single dose of Zeolite A without any adverse reaction in the eye. Calcium Silicate had no discernible effect on nidation or on maternal or fetal survival in rabbits. Magnesium Aluminum Silicate had neither a teratogenic nor adverse effects on the mouse fetus. Female rats receiving a 20% Kaolin diet exhibited maternal anemia but no significant reduction in birth weight of the pups was recorded. Type A Zeolite produced no adverse effects on the dam, embryo, or fetus in either rats or rabbits at any dose level. Clinoptilolite had no effect on female rat reproductive performance. These ingredients were not genotoxic in the Ames bacterial test system. In primary hepatocyte cultures, the addition of Attapulgite had no significant unscheduled DNA synthesis. Attapulgite did cause significant increases in unscheduled DNA synthesis in rat pleural mesothelial cells, but no significant increase in sister chromosome exchanges were seen. Zeolite particles (<10 microm) produced statistically significant increase in the percentage of aberrant metaphases in human peripheral blood lymphocytes and cells collected by peritoneal lavage from exposed mice. Topical application of Magnesium Aluminum Silicate to human skin daily for 1 week produced no adverse effects. Occupational exposure to mineral dusts has been studied extensively. Fibrosis and pneumoconiosis have been documented in workers involved in the mining and processing of Aluminum Silicate, Calcium Silicate, Zirconium Silicate, Fuller's Earth, Kaolin, Montmorillonite, Pyrophyllite, and Zeolite. The Cosmetic Ingredient Review (CIR. The Cosmetic Ingredient Review (CIR) Expert Panel concluded that the extensive pulmonary damage in humans was the result of direct occupational inhalation of the dusts and noted that lesions seen in animals were affected by particle size, fiber length, and concentration. The Panel considers that most of the formulations are not respirable and of the preparations that are respirable, the concentration of the ingredient is very low. Even so, the Panel considered that any spray containing these solids should be formulated to minimize their inhalation. With this admonition to the cosmetics industry, the CIR Expert Panel concluded that these ingredients are safe as currently used in cosmetic formulations. The Panel did note that the cosmetic ingredient, Talc, is a hydrated magnesium silicate. Because it has a unique crystalline structure that differs from ingredients addressed in this safety assessment, Talc is not included in this report. PMID:12851164

  3. Multiple episodes of zeolite deposition in fractured silicic tuff

    SciTech Connect

    Carlos, B.A.; Chipera, S.J.; Snow, M.G.

    1995-04-01

    Fractures in silicic tuffs above the water table at Yucca Mountain, Nevada, USA contain two morphologies of heulandite with different compositions. Tabular heulandite is zoned, with Sr-rich cores and Mg-rich rims. Later prismatic heulandite is nearly the same composition as the more magnesian rims. Heulandite and stellerite may occur between layers of calcite, and calcite occurs locally between generations of heulandite. Thermodynamic modeling, using estimated thermodynamic data and observed chemical compositions for heulandite and stellerite, shows that stellerite is the favored zeolite unless Ca concentrations are reduced or Mg and/or Sr concentrations are significantly elevated above current Yucca Mountain waters.

  4. The identification of crystalline olivine in cometary silicates

    NASA Astrophysics Data System (ADS)

    Campins, H.; Ryan, E. V.

    1989-06-01

    An intermediate-resolution spectrum of the 8-13 micron region in comet Halley is obtained which shows a prominent silicate emission feature with structure not observed before in other comets or in interstellar silicates. The presence of a strong 11.3 micron peak reported by Bregman and coworkers is confirmed, and evidence is found for additional structure in the band. By comparison with spectra of interplanetary dust particles and laboratory silicates, it is concluded that small crystalline olivine particles are a major component of the silicates in this comet; other silicates (e.g., amorphous or hydrated) must also be present. The identification of crystalline olivine in this part of the spectrum is supported by the observation of four peaks in 20-50 micron airborne spectra of this comet which have also been attributed to olivine.

  5. Properties of cometary crystalline silicate before and after perihelion passage

    NASA Astrophysics Data System (ADS)

    Ootsubo, Takafumi

    2013-01-01

    Crystalline silicate is sometimes observed in comets as an 11.3-micron resonant emission feature, and may be used for probing the early solar nebula. Because the formation of the crystalline silicate requires high temperature, they are thought to be born from amorphous silicate at the inner region, and then transported toward the outer regions where comets were born. This transportation can produce the difference in the crystalline fraction in the cometary silicate dust between two dynamical types of comets, Oort-cloud comets (OCs) and Ecliptic comets (ECs), due to the different heliocentric distances of their birth places. The study of peak wavelengths in crystalline features is important to investigate the conditions of the crystalline silicate formation as well. Thus far, we don't have enough OC samples, while we have observed several ECs. Fortunately, we can observe three comets in this semester. In particular, C/2012 S1 (ISON) is a bright sungrazing comet, and we might expect possible splitting and exposing of pristine materials inside the nucleus after its perihelion passage. Observations at pre- and post-perihelion provide us precious information on the dust evolution of the comet. The comet C/2012 S1 (ISON), along with two other comets, is an unparalleled target for this study.

  6. Studies on crystalline microporous vanadium silicates

    SciTech Connect

    Reddy, K.R.; Ramaswamy, A.V.; Ratnasamy, P. )

    1993-09-01

    The synthesis and catalytic properties of V-NCL-1, a novel vanadium silicate, large-pore molecular sieve in various oxidation reactions, are described. The reactions include the oxidation of n-octane, cyclohexane, toluene, trimethylbenzenes, and naphthalene. In the as-synthesized form, most of the vanadium in V-NCL-1 is present as atomically dispersed and isolated V[sup 4+] located in framework positions, though not necessarily in tetrahedral coordination. On calcination in air, the vanadium ions are oxidized to the pentavalent state. In addition, part of the vanadium leaves lattice locations and forms nonframework clusters. When the oxidized sample is reduced, V[sup 4+] ions are formed again. The three-dimensional silicate structure of the molecular sieve is intact during all these treatments. Due to the presence of large pores, V-NCL-1 is able to oxidize bulky molecules such as mesitylene and naphthalene. Unlike their titanium analogs, vanadium silicates are able to oxyfunctionalize the primary carbon atoms in alkanes and the side chains in alkylaromatics. 18 refs., 7 figs., 9 tabs.

  7. Application of thermodynamics to silicate crystalline solutions

    NASA Technical Reports Server (NTRS)

    Saxena, S. K.

    1972-01-01

    A review of thermodynamic relations is presented, describing Guggenheim's regular solution models, the simple mixture, the zeroth approximation, and the quasi-chemical model. The possibilities of retrieving useful thermodynamic quantities from phase equilibrium studies are discussed. Such quantities include the activity-composition relations and the free energy of mixing in crystalline solutions. Theory and results of the study of partitioning of elements in coexisting minerals are briefly reviewed. A thermodynamic study of the intercrystalline and intracrystalline ion exchange relations gives useful information on the thermodynamic behavior of the crystalline solutions involved. Such information is necessary for the solution of most petrogenic problems and for geothermometry. Thermodynamic quantities for tungstates (CaWO4-SrWO4) are calculated.

  8. Crystalline silicates and hydrocarbon-conversion processes employing same

    SciTech Connect

    Kouwenhoven, H.W.; Stork, W.H.

    1980-12-09

    Novel crystalline silicates which in dehydrated form have the composition in terms of moles of the oxides: (1.0 +- 3)(R)2/no.(AFe/sub 2/O/sub 3/.BAl/sub 2/O/sub 3/ . CGa/sub 2/O/sub 3/ . Y(DSiO/sub 2/ . EGeO/sub 2/)), wherein R one or more mono- or bivalent cations and A, B, C, D, E, Y and N are as defined hereinafter are disclosed. The thermally stable silicates are suitably employed as extracting agents, drying agents, ion exchange agents, catalysts and catalyst carriers.

  9. Point atomic multipole moments for simulation of electrostatic potential and field in all-siliceous zeolites.

    PubMed

    Larin, Alexander V

    2011-08-01

    Calibration method of atomic multipole moments (AMMs) is presented with respect to geometries of all-siliceous zeolite models obtained with X-ray diffraction (XRD) methods. Mulliken atomic charges and AMMs are calculated for all-siliceous types possessing small size elementary unit cells at the hybrid density functional theory (DFT) (B3LYP) and general gradient approximation (GGA) Perdew-Burke-Ernzerhof (PBE) levels and then used to fit the dependences versus geometry variables for the Mulliken charges and versus special coordinate for the AMMs. Fitted and exact charges and AMMs are used to compute electrostatic potential (EP) and electric field (EF) for all-siliceous zeolites with CRYSTAL. A possibility of application of the point AMMs to quantum mechanical/molecular mechanics computations or classic simulation of physical adsorption is evaluated. The considered models expand over wide range of structural parameters and could be applied even to amorphous all-siliceous systems. PMID:21598280

  10. Aluminum coordination and active sites on aluminas, Y zeolites and pillared layered silicates

    SciTech Connect

    Fripiat, J.J.

    1991-01-01

    Our work has been deployed in four directions, namely, (1) Study of the distribution of aluminum within three possible kinds of coordination shells: four-fold (IV), five-fold (V), and six-fold (VI), in aluminas and dealuminated zeolites by high-resolution solid state NMR or magic angle NMR. Besides the classical one pulse spectra, nutation spectra have been studied. (2) Study of the electron deficient sites by electron paramagnetic resonance (EPR) of probe molecules on aluminas and decationated zeolites. Electron deficient sites are considered as Lewis sites. (3) Study of the model isomerization reaction 1 butene {yields} 2 cis or trans butene on the aluminas characterized in 1 and 2. (4) Synthesis of a silicate lattice in which silicon has been partially replaced by aluminum. The chosen silicate is that of the zeolite (fibrous) sepiolite. It has been characterized as indicated in 1 and 2.

  11. Formation of Polycyclic Organic Molecules on Crystalline Silicate Grains

    NASA Astrophysics Data System (ADS)

    Hammonds, Mark; Tian, Ming; Liu, Bing-Si; Wang, Na; Cheung, Allan S.-C.; Sarre, Peter

    2015-08-01

    The pathways through which complex organic molecules are manufactured from simple chemical species are of key importance to the understanding of the evolution of organic material in the cosmos, and consequently the formation of prebiotic molecules. This work presents laboratory studies on the formation of polycyclic aromatic hydrocarbons (PAHs) over heated crystalline silicates from an acetylene feedstock. A rich variety of molecular species are formed and detected using time-of-flight mass spectrometry. Implications are discussed into formation and evolution of complex organic material in circumstellar environments.

  12. INTERSTELLAR SILICATE DUST IN THE z = 0.89 ABSORBER TOWARD PKS 1830-211: CRYSTALLINE SILICATES AT HIGH REDSHIFT?

    SciTech Connect

    Aller, Monique C.; Kulkarni, Varsha P.; Som, Debopam; York, Donald G.; Welty, Daniel E.; Vladilo, Giovanni

    2012-03-20

    We present evidence of a >10{sigma} detection of the 10 {mu}m silicate dust absorption feature in the spectrum of the gravitationally lensed quasar PKS 1830-211, produced by a foreground absorption system at redshift 0.886. We have examined more than 100 optical depth templates, derived from both observations of Galactic and extragalactic sources and laboratory measurements, in order to constrain the chemical structure of the silicate dust. We find that the best fit to the observed absorption profile is produced by laboratory crystalline olivine, with a corresponding peak optical depth of {tau}{sub 10} = 0.27 {+-} 0.05. The fit is slightly improved upon by including small contributions from additional materials, such as silica, enstatite, or serpentine, which suggests that the dust composition may consist of a blend of crystalline silicates. Combining templates for amorphous and crystalline silicates, we find that the fraction of crystalline silicates needs to be at least 95%. Given the rarity of extragalactic sources with such a high degree of silicate crystallinity, we also explore the possibility that the observed spectral features are produced by amorphous silicates in combination with other molecular or atomic transitions, or by foreground source contamination. While we cannot rule out these latter possibilities, they lead to much poorer profile fits than for the crystalline olivine templates. If the presence of crystalline interstellar silicates in this distant galaxy is real, it would be highly unusual, given that the Milky Way interstellar matter contains essentially only amorphous silicates. It is possible that the z = 0.886 absorber toward PKS 1830-211, well known for its high molecular content, has a unique star-forming environment that enables crystalline silicates to form and prevail.

  13. Zeolites

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Zeolites are crystalline aluminosilicates that have complex framework structures. However, there are several features of zeolite crystals that make unequivocal structure determinations difficult. The acquisition of reliable structural information on zeolites is greatly facilitated by the availability of high-quality specimens. For structure determinations by conventional diffraction techniques, large single-crystal specimens are essential. Alternatively, structural determinations by powder profile refinement methods relax the constraints on crystal size, but still require materials with a high degree of crystalline perfection. Studies conducted at CAMMP (Center for Advanced Microgravity Materials Processing) have demonstrated that microgravity processing can produce larger crystal sizes and fewer structural defects relative to terrestrial crystal growth. Principal Investigator: Dr. Albert Sacco

  14. Process for converting silicon dioxide containing waste flue dust to crystalline zeolitic molecular sieves of type A

    SciTech Connect

    Achenbach, K.; Turk, G.

    1982-01-12

    Silicon dioxide containing waste flue dust from the production of silicon metal and silicon alloys is converted to crystalline zeolite molecular sieves of type A. The process involves: (1) dissolving the flue dust in alkali metal hydroxide solution with the formation of alkali metal silicate solution having a module (SiO/sub 2/:Me/sub 2/IO) in the range of 2.0:1 to 3.5:1 at a temperature of 60/sup 0/-100/sup 0/ C; (2) purifying the thus obtained alkali metal silicate solution from organic constituents by treatment with activated carbon and/or an oxidizing agent and separating the non-decomposable residue from the solution; and, (3) reacting alkali metal aluminate solution present at room temperature with the diluted, purified alkali metal silicate solution with a module (SiO2:Na2O) of 2.0:1 to 5:1 obtained by steps (1) and (2) and subsequent crystallizing the reaction mixture ((2.0-4.4)Na/sub 2/O:Al/sub 2/O/sub 3/; (1.3-1.8)SiO/sub 2/:(90-120)H/sub 2/O) at a temperature of 90/sup 0/-95/sup 0/ C for a period of 6-12 hours, subsequently filtering, washing to ph of about 10-11 and drying to recover a crystalline, zeolitic molecular sieve of type a having a degree of whiteness according to berger (A. Berger, die farbe 8 nr. 4/6 (1959) pages 187-202) at 460 mu in the range of 90-95%.

  15. Synthesis of Silicate Zeolite Analogues Using Organic Sulfonium Compounds as Structure-Directing Agents.

    PubMed

    Jo, Changbum; Lee, Sungjune; Cho, Sung June; Ryoo, Ryong

    2015-10-19

    A microporous crystalline silica zeolite of the MEL structure type and three other zeolite analogues composed of germanosilicate frameworks were synthesized using tributylsulfonium, triphenylsulfonium, or tri(para-tolyl)sulfonium as the structure-directing agent. The germanosilicates thus obtained had ISV, ITT, or a new zeolite structure depending on the synthesis conditions. The structure of the new germanosilicate was solved using X-ray powder diffraction data with the aid of a charge-flipping method. The solution indicated a crystal structure belonging to the P63/mmc space group with cell parameters of a=16.2003? and c=21.8579?. After calcination, the new germanosilicate material exhibited two types of accessible micropores with diameters of 0.61 and 0.78?nm. PMID:26302889

  16. Iridium Complexes and Clusters in Dealuminated Zeolite HY: Distribution between Crystalline and Impurity Amorphous Regions

    SciTech Connect

    Martinez-Macias, Claudia; Xu, Pinghong; Hwang, Son-Jong; Lu, Jing; Chen, Cong-Yan; Browning, Nigel D.; Gates, Bruce C.

    2014-07-08

    Dealuminated zeolite HY was used to support Ir(CO)2 complexes formed from Ir(CO)2(C5H7O2). Infrared and X-ray absorption spectra and atomic-resolution electron microscopy images identify these complexes, and the images and 27Al NMR spectra identify impurity amorphous regions in the zeolite where the iridium is more susceptible to aggregation than in the crystalline regions. The results indicate a significant stability limitation of metal in amorphous impurity regions of zeolites.

  17. Amphiphilic organosilane-directed synthesis of crystalline zeolite with tunable mesoporosity.

    PubMed

    Choi, Minkee; Cho, Hae Sung; Srivastava, Rajendra; Venkatesan, Chithravel; Choi, Dae-Heung; Ryoo, Ryong

    2006-09-01

    Zeolites are a family of crystalline aluminosilicate materials widely used as shape-selective catalysts, ion exchange materials, and adsorbents for organic compounds. In the present work, zeolites were synthesized by adding a rationally designed amphiphilic organosilane surfactant to conventional alkaline zeolite synthesis mixtures. The zeolite products were characterized by a complementary combination of X-ray diffraction (XRD), nitrogen sorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The analyses show that the present method is suitable as a direct synthesis route to highly mesoporous zeolites. The mesopore diameters could be uniformly tailored, similar to ordered mesoporous silica with amorphous frameworks. The mesoporous zeolite exhibited a narrow, small-angle XRD peak, which is characteristic of the short-range correlation between mesopores, similar to disordered wormhole-like mesoporous materials. The XRD patterns and electron micrographs of the samples taken during crystallization clearly showed the evolution of the mesoporous structure concomitantly to the crystallization of zeolite frameworks. The synthesis of the crystalline aluminosilicate materials with tunable mesoporosity and strong acidity has potentially important technological implications for catalytic reactions of large molecules, whereas conventional mesoporous materials lack hydrothermal stability and acidity. PMID:16892049

  18. Calcium-aluminum-silicate-hydrate "cement" phases and rare Ca-zeolite association at Colle Fabbri, Central Italy

    NASA Astrophysics Data System (ADS)

    Stoppa, F.; Scordari, F.; Mesto, E.; Sharygin, V.; Bortolozzi, G.

    2010-06-01

    Very high temperature, Ca-rich alkaline magma intruded an argillite formation at Colle Fabbri, Central Italy, producing cordierite-tridymite metamorphism in the country rocks. An intense Ba-rich sulphate-carbonate-alkaline hydrothermal plume produced a zone of mineralization several meters thick around the igneous body. Reaction of hydrothermal fluids with country rocks formed calcium-silicate-hydrate (CSH), i.e., tobermorite-afwillite-jennite; calcium-aluminum-silicate-hydrate (CASH) "cement" phases - i.e., thaumasite, strtlingite and an ettringite-like phase and several different species of zeolites: chabazite-Ca, willhendersonite, gismon-dine, three phases bearing Ca with the same or perhaps lower symmetry of phillipsite-Ca, levyne-Ca and the Ca-rich analogue of merlinoite. In addition, apophyllite-(KF) and/or apophyllite-(KOH), Ca-Ba-carbonates, portlandite and sulphates were present. A new polymorph from the pyrrhotite group, containing three layers of sphalerite-type structure in the unit cell, is reported for the first time. Such a complex association is unique. Most of these minerals are specifically related to hydration processes of: (1) pyrometamorphic metacarbonate/metapelitic rocks (natural analogues of cement clinkers); (2) mineralization between intrusive stocks and slates; and (3) high-calcium, alkaline igneous rocks such as melilitites and foidites as well as carbonatites. The Colle Fabbri outcrop offers an opportunity to study in situ complex crystalline overgrowth and specific crystal chemistry in mineral phases formed in igneous to hydrothermal conditions.

  19. Iron silicates, iron-modulated zeolite catalysts, and molecular models thereof.

    PubMed

    Pinkert, Denise; Limberg, Christian

    2014-07-21

    Iron centres incorporated in silicate frameworks or located in their pores have been shown to possess unique catalytic properties. As compared to aluminosilicates this area of zeolite chemistry is much younger and in the first part of this review the findings made so far are summarised. Molecular model compounds may help to understand the formation, corrosion and reactivity of such materials or to even develop new ones. Hence, the subsequent parts deal with molecular iron siloxides, the number of which is still quite limited, and their behaviour also in relation to the iron-modified zeolites is outlined. At first, compounds based on an incompletely condensed cubic silsequioxane are discussed, before iron(III) complexes of more basic siloxide ligands with varying steric demands are described. Finally, recent developments based on branched polydentate siloxides are presented. PMID:24939619

  20. Highly crystalline Zeolite-A from flyash of bituminous and lignite coal combustion.

    PubMed

    Rayalu, S S; Udhoji, J S; Munshi, K N; Hasan, M Z

    2001-11-16

    Flyash is being generated in voluminous amounts by large scale coal combustion process. It poses a serious threat to thermal power industries specifically, in India, wherein the percent of utilisation of flyash is very poor (3-5%). In view of this problem, newer methods of its disposal and utilisation are being explored. The synthesis of zeolite from flyash appears to be one of the most promising alternatives as it has emphasis on value addition to waste material. Flyashes originating from different sources of coal differ in their characteristics and have implications in this work on Zeolite-A production. These factors have been thoroughly investigated and the conditions favourable for formation of Zeolite-A have been delineated. The reactivity of flyash towards zeolite formation is directly dependent on the SiO(2)/Al(2)O(3) ratio, Fe(2)O(3) and CaO content. Amongst the flyashes investigated, so far the sub-bituminous coal based flyash with SiO(2)/Al(2)O(3) ratio of 3.47 appears to be a suitable substrate for Zeolite-A synthesis. These zeolites have been characterised with respect to XRD crystallinity, calcium binding capacity (CBC) and sorption capacity, wherein the crystallinity ranges from 50 to 100%, the CBC ranges from 290 to 560meq/100g and sorption capacity ranges from 16.6 to 23.8%. PMID:11606244

  1. Feasible conversion of solid waste bauxite tailings into highly crystalline 4A zeolite with valuable application

    SciTech Connect

    Ma, Dongyang; Wang, Zhendong; Guo, Min; Zhang, Mei; Liu, Jingbo

    2014-11-15

    Highlights: • Concept to convert waste to valuable product is carried out in this study. • An industrially feasible and cost-effective approach was developed and optimized. • Highly crystalline and well-defined zeolite was produced under moderate conditions. • The zeolite derived from the bauxite tailings displayed high ion exchange capacity. • Bauxite tailings have potential application in heavy metal ions adsorbent. - Abstract: Bauxite tailings are a major type of solid wastes generated in the flotation process. The waste by-products caused significant environmental impact. To lessen this hazardous effect from poisonous mine tailings, a feasible and cost-effective solution was conceived and implemented. Our approach focused on reutilization of the bauxite tailings by converting it to 4A zeolite for reuse in diverse applications. Three steps were involved in the bauxite conversion: wet-chemistry, alkali fusion, and crystallization to remove impurities and to prepare porous 4A zeolite. It was found that the cubic 4A zeolite was single phase, in high purity, with high crystallinity and well-defined structure. Importantly, the 4A zeolite displayed maximum calcium ion exchange capacity averaged at 296 mg CaCO{sub 3}/g, comparable to commercially-available zeolite (310 mg CaCO{sub 3}/g) exchange capacity. Base on the optimal synthesis condition, the reaction yield of zeolite 4A from bauxite tailings achieved to about 38.43%, hence, this study will provide a new paradigm for remediation of bauxite tailings, further mitigating the environmental and health care concerns, particularly in the mainland of PR China.

  2. Defect sites in highly siliceous HZSM-5 zeolites: A study performed by alumination and IR spectroscopy

    SciTech Connect

    Yamagishi, Kouji; Namba, Seitaro; Yashima, Tatsuaki )

    1991-01-24

    The concentration of oxygen atoms on defect sites in a highly siliceous HZSM-5 type zeolite was estimated by the {sup 18}O-exchange reaction between C{sup 18}O{sub 2} and the zeolite. The concentration of oxygen atoms on defect sites could be controlled by means of changes of the gel composition and of the use of various silica sources in the hydrothermal synthesis. The relationship between the concentration of oxygen atoms on defect sites in a highly siliceous HZSM-5 and the concentration of aluminum introduced into the framework of the HZSM-5 by an alumination was examined. The concentration of the framework aluminum was the same as one-fourth that of the oxygen atoms on defect sites. These results suggest that the defect sites into which aluminum atoms are introduced tetrahedrally can be identified with hydroxyl nests that consist of four silanol groups. The existence of hydroxyl nests could be confirmed by IR spectroscopy. From the {sup 18}O-exchange reaction and IR measurements, the authors conclude that the sharp band at 3,740 cm{sup {minus}1} can be attributed to both isolated SiOH groups on the external surface and intracrystalline isolated SiOH groups and that the broad band at 3,505 cm{sup {minus}1} can be attributed to the SiOH groups in hydroxyl nests.

  3. [Aluminum coordination and active sites on aluminas, Y-zeolites and pillared layered silicates]. Progress report

    SciTech Connect

    Fripiat, J.J.

    1994-02-01

    This report is organized in four sections. In the first the authors will outline structural features which are common to all fine grained alumina, as well as to non-framework alumina in zeolites. This section will be followed by a study of the surface vs. bulk coordination of aluminum. The third section will deal with measurement of the number of acid sites and the scaling of their strength. The fourth and last section will describe three model reactions: the isomerization of 1-butene and of 2 cis-butene; the isomerization and disproportionation of oxtho-xylene; and the transformation of trichloroethane into vinyl chloride followed by the polymerization of the vinyl chloride. The relationship between chemical activity and selectivity and what is known of the local structure of the active catalytic sites will be underlined. Other kinds of zeolites besides Y zeolite have been studied. Instead of the aluminum pillared silicates they found it more interesting to study the substitution of silicon by aluminum in a layered structure containing a permanent porosity (aluminated sepiolite).

  4. A SPITZER INFRARED SPECTROGRAPH DETECTION OF CRYSTALLINE SILICATES IN A PROTOSTELLAR ENVELOPE

    SciTech Connect

    Poteet, Charles A.; Megeath, S. Thomas; Fischer, William J.; Bjorkman, Jon E.; Watson, Dan M.; Remming, Ian S.; McClure, Melissa K.; Calvet, Nuria; Hartmann, Lee; Tobin, John J.; Sargent, Benjamin A.; Muzerolle, James; Furlan, Elise; Allen, Lori E.; Ali, Babar

    2011-06-01

    We present the Spitzer Space Telescope Infrared Spectrograph spectrum of the Orion A protostar HOPS-68. The mid-infrared spectrum reveals crystalline substructure at 11.1, 16.1, 18.8, 23.6, 27.9, and 33.6 {mu}m superimposed on the broad 9.7 and 18 {mu}m amorphous silicate features; the substructure is well matched by the presence of the olivine end-member forsterite (Mg{sub 2}SiO{sub 4}). Crystalline silicates are often observed as infrared emission features around the circumstellar disks of Herbig Ae/Be stars and T Tauri stars. However, this is the first unambiguous detection of crystalline silicate absorption in a cold, infalling, protostellar envelope. We estimate the crystalline mass fraction along the line of sight by first assuming that the crystalline silicates are located in a cold absorbing screen and secondly by utilizing radiative transfer models. The resulting crystalline mass fractions of 0.14 and 0.17, respectively, are significantly greater than the upper limit found in the interstellar medium ({approx}<0.02-0.05). We propose that the amorphous silicates were annealed within the hot inner disk and/or envelope regions and subsequently transported outward into the envelope by entrainment in a protostellar outflow.

  5. Feasible conversion of solid waste bauxite tailings into highly crystalline 4A zeolite with valuable application.

    PubMed

    Ma, Dongyang; Wang, Zhendong; Guo, Min; Zhang, Mei; Liu, Jingbo

    2014-11-01

    Bauxite tailings are a major type of solid wastes generated in the flotation process. The waste by-products caused significant environmental impact. To lessen this hazardous effect from poisonous mine tailings, a feasible and cost-effective solution was conceived and implemented. Our approach focused on reutilization of the bauxite tailings by converting it to 4A zeolite for reuse in diverse applications. Three steps were involved in the bauxite conversion: wet-chemistry, alkali fusion, and crystallization to remove impurities and to prepare porous 4A zeolite. It was found that the cubic 4A zeolite was single phase, in high purity, with high crystallinity and well-defined structure. Importantly, the 4A zeolite displayed maximum calcium ion exchange capacity averaged at 296 mg CaCO3/g, comparable to commercially-available zeolite (310 mg CaCO3/g) exchange capacity. Base on the optimal synthesis condition, the reaction yield of zeolite 4A from bauxite tailings achieved to about 38.43%, hence, this study will provide a new paradigm for remediation of bauxite tailings, further mitigating the environmental and health care concerns, particularly in the mainland of PR China. PMID:25153822

  6. Aluminum coordination and active sites on aluminas, Y zeolites and pillared silicates

    SciTech Connect

    Fripiat, J.J.

    1992-01-01

    Effort was continued to characterize the nature of the Al species responsible for Lewis acidity in zeolites and in aluminas by NMR. While numerous techniques have been successful for scaling the acid strength of Broensted sites, the situation is not satisfactory for the Lewis acid sites. Initial rate of dehydrochlorination of 1,1,1-trichloroethane is sensitive to strength of Lewis acid sites. N-Butene isomerization has been extended to the new aluminas obtained from nano-sized precursors. O-Xylene isomerization was carried out in a recirculation reactor on H-mordenite samples containing Lewis or Broensted acid sites; effects of H[sub 2] and NO were also investigated. Cracking of methylcyclohexane and 3-methylpentane was investigated by EPR on H-mordenite. Sepiolite, a Mg silicate with zeolitic channels, had Al substituted for Si; the negative charge is balanced by, say, VO[sup 2+]. Transformation of ethanol into butadiene on this dual-function catalyst appears to result from a Prins reaction between acetaldeyde formed on the redox sites and ethylene resulting from dehydration of ethanol on Lewis sites.

  7. Cooked GEMS - Insights into the Hot Origins of Crystalline Silicates in Circumstellar Disks and the Cold Origins of GEMS

    NASA Technical Reports Server (NTRS)

    Brownlee, D. E.; Joswiak, D. J.; Bradley, J. P.; Matrajt, G.; Wooden, D. H.

    2005-01-01

    The comparison of interstellar, circumstellar and primitive solar nebula silicates has led to a significant conundrum in the understanding of the nature of solid materials that begin the planet forming processes. Crystalline silicates are found in circumstellar regions around young stars and also evolved stars ejecting particles into the interstellar medium (ISM) but they are not seen in the interstellar medium itself, the source material for star and planet formation. Crystalline silicates are minor to major components of all known early solar system materials that have been examined as meteorites or interplanetary dust samples. The strong presence of Mg-rich crystalline silicates in Oort cloud comets and their minor presence in some Kuiper belt comets is also indicated by 11.2 m peak in approx. 10 microns "silicate" infrared feature. This evidence strongly indicates that Mg-rich crystalline silicates were abundant components of the solar nebula disk out to at least 10 AU, and present out to 30 AU.

  8. Highly mesoporous single-crystalline zeolite beta synthesized using a nonsurfactant cationic polymer as a dual-function template.

    PubMed

    Zhu, Jie; Zhu, Yihan; Zhu, Liangkui; Rigutto, Marcello; van der Made, Alexander; Yang, Chengguang; Pan, Shuxiang; Wang, Liang; Zhu, Longfeng; Jin, Yinying; Sun, Qi; Wu, Qinming; Meng, Xiangju; Zhang, Daliang; Han, Yu; Li, Jixue; Chu, Yueying; Zheng, Anmin; Qiu, Shilun; Zheng, Xiaoming; Xiao, Feng-Shou

    2014-02-12

    Mesoporous zeolites are useful solid catalysts for conversion of bulky molecules because they offer fast mass transfer along with size and shape selectivity. We report here the successful synthesis of mesoporous aluminosilicate zeolite Beta from a commercial cationic polymer that acts as a dual-function template to generate zeolitic micropores and mesopores simultaneously. This is the first demonstration of a single nonsurfactant polymer acting as such a template. Using high-resolution electron microscopy and tomography, we discovered that the resulting material (Beta-MS) has abundant and highly interconnected mesopores. More importantly, we demonstrated using a three-dimensional electron diffraction technique that each Beta-MS particle is a single crystal, whereas most previously reported mesoporous zeolites are comprised of nanosized zeolitic grains with random orientations. The use of nonsurfactant templates is essential to gaining single-crystalline mesoporous zeolites. The single-crystalline nature endows Beta-MS with better hydrothermal stability compared with surfactant-derived mesoporous zeolite Beta. Beta-MS also exhibited remarkably higher catalytic activity than did conventional zeolite Beta in acid-catalyzed reactions involving large molecules. PMID:24450997

  9. Discrete dipole approximation models of chrystalline forsterite: Applications to cometary crystalline silicates

    NASA Astrophysics Data System (ADS)

    Lindsay, Sean Stephen

    The shape, size, and composition of crystalline silicates observed in comet comae and external proto-planetary disks are indicative of the formation and evolution of the dust grains during the processes of planetary formation. In this dissertation, I present the 3 -- 40 mum absorption efficiencies( Qabs) of irregularly shaped forsterite crystals computed with the discrete dipole approximation (DDA) code DDSCAT developed by Draine and Flatau and run on the NASA Advanced Supercomputing facility Pleiades. An investigation of grain shapes ranging from spheroidal to irregular indicate that the strong spectral features from forsterite are sensitive to grain shape and are potentially degenerate with the effects of crystal solid state composition (Mg-content). The 10, 11, 18, 23, and 33.5 mum features are found to be the most crystal shape sensitive and should be avoided in determining Mg-content. The distinct spectral features for the three shape classes are connected with crystal formation environment using a condensation experiment by (Kobatake et al., 2008). The condensation experiment demonstrates that condensed forsterite crystal shapes are dependent on the condensation environmental temperature. I generate DDSCAT target analog shapes to the condensed crystal shapes. These analog shapes are represented by the three shape classes: 1) equant, 2) a, c-columns, and 3) b-shortened platelets. Each of these shape classes exhibit distinct spectral features that can be used to interpret grain shape characteristics from 8 --- 40 mum spectroscopy of astronomical objects containing crystalline silicates. Synthetic spectral energy distributions (SEDs) of the coma of Hale-Bopp at rh = 2.8 AU are generated by thermally modeling the flux contributions of 5 mineral species present in comets. The synthetic SEDs are constrained using a chi2- minimization technique. The mineral species are amorphous carbon, amorphous pyroxene, amorphous olivine, crystalline enstatite, and crystalline forsterite. Using the DDSCAT computed absorption efficiencies for a large variety of forsterite crystal shapes, which are computed for 66 grain sizes between 0.1 -- 5.0 mum, the flux contribution of irregularly shaped forsterite is computed. The forsterite flux contribution is then summed with the amorphous and crystalline enstatite contributions to generate the total synthetic SED. The DDSCAT forsterite grain shape synthetic SEDs reveal that the crystalline silicates in the coma of Hale-Bopp are irregular in shape with two distinct shape characteristics related to specific formation mechanisms: 1) equant grains with sharp ( ≲ 90°) angles between the faces, edges, and vertices that formed as high temperature condensates in the inner 1 -- 3 AU radial region of the Solar System's protoplanetary disk; and 2) c-shortened platelet shapes that likely formed from collisional processing of the crystals. The 8 -- 40 mum silicate spectral features of Hale-Bopp's coma are compared to the silicate spectral features of the comae of 17P/Holmes during 2007 outburst and 9P/Tempel 1 during the Deep Impact experiment to show that the silicate features with crystalline resonances are remarkably similar. The similarity in silicate spectral features suggests that the grain populations in the comae of these comets are similar in shape, size, and compositon. However, Hale-Bopp is a nearly isotropic comet (NIC) that dynamically came from the Oort cloud, and 17P and 9P are ecliptic comets (ECs) that dynamically came from the Scattered Disk. The different dynamical source regions yet similar silicate (amorphous and crystalline) grain populations suggest that ECs and NICs innately have similar grains and that the typically weaker silicate features of ECs are an effect of the surface grains becoming compacted with numerous perihelion passages. Hence, the differences in silicate between ECs and NICs are the result of grain structure and not grain composition. (Abstract shortened by UMI.)

  10. High Silicate Crystalline-to-Amorphous Ratios in Comets C/2001 Q4 (NEAT) and Hale-Bopp

    NASA Technical Reports Server (NTRS)

    Wooden, D. H.; Harker, D. E.; Wodward, C. E.

    2004-01-01

    Crystalline silicates, by their apparent absence in the ISM, are dust grains that experienced high temperatures in the solar nebula. Mg-rich crystalline silicates formed either by condensation from hot nebular gases (1450 K) or by the annealing of Mg-rich amorphous silicates (approximately 1000 K) in shocks in the 5-10AU region or by radial transport into and out of the hot inner zones, e.g., T(sub d) greater than 1000K at r(sub h) less than 5AU, 10(exp -6) -10(exp -5) solar mass per year, alpha = 10(exp -4) of the early solar nebula. Mg-rich crystalline silicates are found in interplanetary dust particles (IDPs) and produce IR spectral features in many Oort cloud comets. In May 2004, we discovered strong crystalline silicate features in the dynamically new Oort cloud comet C/2001 Q4 (NEAT). Thermal emission modeling of comets Q4 and C/1995 O1 (Hale-Bopp) demonstrate that both these comets have similar, high silicate crystalline-toamorphous ratios of 2.4 and 2.1, respectively, indicating that these icy planetesimals aggregated from similar reservoirs of material or that crystalline silicates were widely distributed within the comet-forming zone. This argues for efficient annealing mechanisms and radial mixing.

  11. Antimicrobial effects of silver zeolite, silver zirconium phosphate silicate and silver zirconium phosphate against oral microorganisms

    PubMed Central

    Saengmee-anupharb, Sirikamon; Srikhirin, Toemsak; Thaweboon, Boonyanit; Thaweboon, Sroisiri; Amornsakchai, Taweechai; Dechkunakorn, Surachai; Suddhasthira, Theeralaksna; Kamaguchi, Arihide

    2013-01-01

    Objective To evaluate the antimicrobial activities of silver inorganic materials, including silver zeolite (AgZ), silver zirconium phosphate silicate (AgZrPSi) and silver zirconium phosphate (AgZrP), against oral microorganisms. In line with this objective, the morphology and structure of each type of silver based powders were also investigated. Methods The antimicrobial activities of AgZ, AgZrPSi and AgZrP were tested against Streptococcus mutans, Lactobacillus casei, Candida albicans and Staphylococcus aureus using disk diffusion assay as a screening test. The minimum inhibitory concentration (MIC) and minimum lethal concentration (MLC) were determined using the modified membrane method. Scanning electron microscope and X-ray diffraction were used to investigate the morphology and structure of these silver materials. Results All forms of silver inorganic materials could inhibit the growth of all test microorganisms. The MIC of AgZ, AgZrPSi and AgZrP was 10.0 g/L whereas MLC ranged between 10.060.0 g/L. In terms of morphology and structure, AgZrPSi and AgZrP had smaller sized particles (1.53.0 m) and more uniformly shaped than AgZ. Conclusions Silver inorganic materials in the form of AgZ, AgZrPSi and AgZrP had antimicrobial effects against all test oral microorganisms and those activities may be influenced by the crystal structure of carriers. These results suggest that these silver materials may be useful metals applied to oral hygiene products to provide antimicrobial activity against oral infection. PMID:23570016

  12. Combined experimental and computational NMR study of crystalline and amorphous zeolitic imidazolate frameworks.

    PubMed

    Baxter, Emma F; Bennett, Thomas D; Mellot-Draznieks, Caroline; Gervais, Christel; Blanc, Frédéric; Cheetham, Anthony K

    2015-10-14

    Zeolitic imidazolate frameworks (ZIFs) have attracted great interest in recent years due to their high chemical and thermal stability with promising applications in gas storage and separations. We investigate the structures of three different crystalline ZIFs - ZIF-4, ZIF-8, ZIF-zni - and their amorphous counterparts using high field (13)C and (15)N CP MAS NMR. The high field (20 T) allows for the observation of all crystallographically independent carbon and nitrogen atoms in the crystalline ZIFs. Combining our experimental results with density functional theory calculations enabled the assignment of all chemical shifts. The crystalline spectra reveal the potential of high field NMR to distinguish between two ZIF polymorphs, ZIF-4 and ZIF-zni, with identical [Zn(C3H3N2)2] chemical compositions. (13)C and (15)N CP MAS NMR data obtained for the amorphous ZIFs clearly showed signal broadening upon amorphization, confirming the retention of chemical composition and the structural similarity of amorphous ZIF-4 and ZIF-zni. In the case of amorphous ZIF-8, we present evidence for the partial de-coordination of the 2-methyl imidazole linker. PMID:26351979

  13. On the metallicity dependence of crystalline silicates in oxygen-rich asymptotic giant branch stars and red supergiants

    NASA Astrophysics Data System (ADS)

    Jones, O. C.; Kemper, F.; Sargent, B. A.; McDonald, I.; Gielen, C.; Woods, Paul M.; Sloan, G. C.; Boyer, M. L.; Zijlstra, A. A.; Clayton, G. C.; Kraemer, K. E.; Srinivasan, S.; Ruffle, P. M. E.

    2012-12-01

    We investigate the occurrence of crystalline silicates in oxygen-rich evolved stars across a range of metallicities and mass-loss rates. It has been suggested that the crystalline silicate feature strength increases with increasing mass-loss rate, implying a correlation between lattice structure and wind density. To test this, we analyse Spitzer Infrared Spectrograph and Infrared Space Observatory Short Wavelength Spectrometer spectra of 217 oxygen-rich asymptotic giant branch and 98 red supergiants in the Milky Way, the Large and Small Magellanic Clouds, and Galactic globular clusters. These encompass a range of spectral morphologies from the spectrally rich which exhibit a wealth of crystalline and amorphous silicate features to 'naked' (dust-free) stars. We combine spectroscopic and photometric observations with the GRAMS grid of radiative transfer models to derive (dust) mass-loss rates and temperature. We then measure the strength of the crystalline silicate bands at 23, 28 and 33 ?m. We detect crystalline silicates in stars with dust mass-loss rates which span over 3 dex, down to rates of 10-9 M? yr-1. Detections of crystalline silicates are more prevalent in higher mass-loss rate objects, though the highest mass-loss rate objects do not show the 23-?m feature, possibly due to the low temperature of the forsterite grains or it may indicate that the 23-?m band is going into absorption due to high column density. Furthermore, we detect a change in the crystalline silicate mineralogy with metallicity, with enstatite seen increasingly at low metallicity.

  14. Applications of high resolution NMR to geochemistry: crystalline, glass, and molten silicates

    SciTech Connect

    Schneider, E.

    1985-11-01

    The nuclear spin interactions and the associated quantum mechanical dynamics which are present in solid state NMR are introduced. A brief overview of aluminosilicate structure is presented and crystalline structure is then reviewed, with emphasis on the contributions made by /sup 29/Si NMR spectroscopy. The local structure of glass aluminosilicates as observed by NMR, is presented with analysis of the information content of /sup 29/Si spectra. A high-temperature (to 1300/sup 0/C) NMR spectroscopic investigation of the local environment and dynamics of molecular motion in molten aluminosilicates is described. A comparison is made of silicate liquid, glass, and crystalline local structure. The atomic and molecular motions present in a melt are investigated through relaxation time (T/sub 1/ and T/sub 2/) measurements as a function of composition and temperature for /sup 23/Na and /sup 29/Si.

  15. A memory diffusion model for molecular anisotropic diffusion in siliceous ?-zeolite.

    PubMed

    Ji, Xiangfei; An, Zhuanzhuan; Yang, Xiaofeng

    2016-01-01

    A memory diffusion model of molecules on ?-zeolite is proposed. In the model, molecular diffusion in ?-zeolites is treated as jumping from one adsorption site to its neighbors and the jumping probability is a compound probability which includes that provided by the transitional state theory as well as that derived from the information about which direction the target molecule comes from. The proposed approach reveals that the diffusivities along two crystal axes on ?-zeolite are correlated. The model is tested by molecular dynamics simulations on diffusion of benzene and other simple molecules in ?-zeolites. The results show that the molecules with larger diameters fit the prediction much better and that the "memory effects" are important in all cases. PMID:26781666

  16. Aluminum coordination and active sites on aluminas, Y zeolites and pillared layered silicates. Progress report, June 1, 1990--January 31, 1992

    SciTech Connect

    Fripiat, J.J.

    1991-12-31

    Our work has been deployed in four directions, namely, (1) Study of the distribution of aluminum within three possible kinds of coordination shells: four-fold (IV), five-fold (V), and six-fold (VI), in aluminas and dealuminated zeolites by high-resolution solid state NMR or magic angle NMR. Besides the classical one pulse spectra, nutation spectra have been studied. (2) Study of the electron deficient sites by electron paramagnetic resonance (EPR) of probe molecules on aluminas and decationated zeolites. Electron deficient sites are considered as Lewis sites. (3) Study of the model isomerization reaction 1 butene {yields} 2 cis or trans butene on the aluminas characterized in 1 and 2. (4) Synthesis of a silicate lattice in which silicon has been partially replaced by aluminum. The chosen silicate is that of the zeolite (fibrous) sepiolite. It has been characterized as indicated in 1 and 2.

  17. Zeolite materials prepared using silicate waste from template synthesis of ordered mesoporous carbon.

    PubMed

    Kim, Yun Kyung; Rajesh, Kizhakke Palleeri; Yu, Jong-Sung

    2013-09-15

    Significant amount of silica waste is generated in the preparation of porous carbon materials using template synthesis. Industrial production of such porous carbon not only creates waste chemicals, but also poses significant environmental concerns and high waste treatment cost. Recycling is proposed as the best solution for tackling such chemical wastes. In this study, etched silica waste released from template synthesis of mesoporous carbon is recycled to produce precious functional microporous zeolite materials. The solid silica template is etched out with NaOH solution to produce silica-free mesoporous carbon. The collected silica waste is recycled to generate zeolites such as LTA and MFI type silica materials. The formation of zeolites is confirmed by FT-IR, XRD, (29)Si NMR, (27)Al NMR, and SEM. This straight forward green chemistry route not only recycles the waste chemicals, but also decreases environmental pollution for better improvement of our living. PMID:23792927

  18. Aluminum coordination and active sites on aluminas, Y zeolites and pillared silicates. Progress report, January 31, 1992--January 31, 1993

    SciTech Connect

    Fripiat, J.J.

    1992-12-31

    Effort was continued to characterize the nature of the Al species responsible for Lewis acidity in zeolites and in aluminas by NMR. While numerous techniques have been successful for scaling the acid strength of Broensted sites, the situation is not satisfactory for the Lewis acid sites. Initial rate of dehydrochlorination of 1,1,1-trichloroethane is sensitive to strength of Lewis acid sites. N-Butene isomerization has been extended to the new aluminas obtained from nano-sized precursors. O-Xylene isomerization was carried out in a recirculation reactor on H-mordenite samples containing Lewis or Broensted acid sites; effects of H{sub 2} and NO were also investigated. Cracking of methylcyclohexane and 3-methylpentane was investigated by EPR on H-mordenite. Sepiolite, a Mg silicate with zeolitic channels, had Al substituted for Si; the negative charge is balanced by, say, VO{sup 2+}. Transformation of ethanol into butadiene on this dual-function catalyst appears to result from a Prins reaction between acetaldeyde formed on the redox sites and ethylene resulting from dehydration of ethanol on Lewis sites.

  19. Crystalline Silicates in Comets: Modeling Irregularly-Shaped Forsterite Crystals and Its Implications on Condensation Conditions

    NASA Technical Reports Server (NTRS)

    Wooden, Diane H.; Lindsay, Sean S.

    2011-01-01

    Crystalline silicates in comets are a product of the condensation in the hot inner regions (T > or approx. equals 1400 K [1]) of our proto-planetary disk or annealing at somewhat lower temperatures (T > or approx. equals 1000-1200 K) [2, 3, 4] in shocks coupled with disk evolutionary processes that include radial transport of crystals from their formation locations out to the cold outer regions where comet nuclei formed. The grain shape of forsterite (crystals) could be indicative of their formation pathways at high temperatures through vapor-solid condensation or at lower temperatures through vapor-liquid-solid formation and growth [5, 6, 7]. Experiments demonstrate that crystals that formed from a rapidly cooled highly supersaturated silicate vapor are characterized by bulky, platy, columnar/needle and droplet shapes for values of temperature and supersaturation, T and sigma, of 1000-1450 C and < 97, 700-1000 C and 97-161, 580-820 C and 131-230, and <500 C and > 230, respectively [7]. The experimental columnar/needle shapes, which form by vapor-liquid-solid at lower temperatures (<820 C), are extended stacks of plates, where the extension is not correlated with an axial direction: columnar/needles may be extended in the c-axis or a-axis direction, can change directions, and/or are off-kilter or a bit askew extending in a combination of the a- and c-axis direction.

  20. Crystalline Mg2SiO4 and amorphous Mg-bearing silicate grain formation by coalescence and growth

    NASA Astrophysics Data System (ADS)

    Kamitsuji, K.; Suzuki, H.; Kimura, Y.; Sato, T.; Saito, Y.; Kaito, C.

    2005-01-01

    A novel method for producing MgO and SiO2 smokes was developed. Mg-bearing silicate grain formation using the coalescence and growth of MgO and SiO2 grains was carried out in our laboratory. It becomes evident that single and poly crystalline Mg2SiO4 (forsterite) and amorphous Mg-bearing silicate grains can be produced by the coalescence and growth of MgO and SiO2 grains. This result suggests that the observed crystalline Mg2SiO4 grains and amorphous Mg-bearing silicate particles in Red Super Giant (RSG), Asymptotic Giant Branch (AGB), post-AGB and planetary nebula (PNe) could be produced by the coalescence and growth of MgO and SiO2 grains.

  1. Discrimination of zeolites and beryllium containing silicates using portable Raman spectroscometric equipment with near-infrared excitation

    NASA Astrophysics Data System (ADS)

    Jehlička, J.; Vandenabeele, P.; Edwards, H. G. M.

    2012-02-01

    In this paper Raman spectra were obtained for a series of zeolites (thomsonite, stilbite, natrolite) and beryllium containing silicates (beryl, chrysoberyl, euclase, phenacite, bavenite, milarite) using a portable Raman specrometer with a 785 nm laser excitation to show the possibility to apply this setting for unambiguous detection and discrimination of these silicate minerals. Obtained spectra contain the most intense Raman bands at the same positions ±2-4 cm -1 as reported in the literature. The use of these bands permits the unambiguous identification of these phases. Data show the possibility to discriminate individual species of similar whitish color and aspect. Measurements showed an excellent correspondence of Raman bands obtained using the portable system and a laboratory Raman microspectrometer (with the same excitation laser wavelenght). However, for several minerals of these groups (chrysoberyl, bertrandite, chiavennite) Raman spectra were not of sufficient quality to permit unambiguous identification. The reasons are discussed. Raman spectrum of chiavennite CaMnBe 2Si 5O 13(OH) 2·2(H 2O) - a transformation product occurring together with bavenite on the surface of beryl crystals was obtained for the first time using the laboratory Raman spectrometer.

  2. Discrimination of zeolites and beryllium containing silicates using portable Raman spectroscometric equipment with near-infrared excitation.

    PubMed

    Jehlička, J; Vandenabeele, P; Edwards, H G M

    2012-02-01

    In this paper Raman spectra were obtained for a series of zeolites (thomsonite, stilbite, natrolite) and beryllium containing silicates (beryl, chrysoberyl, euclase, phenacite, bavenite, milarite) using a portable Raman specrometer with a 785 nm laser excitation to show the possibility to apply this setting for unambiguous detection and discrimination of these silicate minerals. Obtained spectra contain the most intense Raman bands at the same positions ±2-4 cm(-1) as reported in the literature. The use of these bands permits the unambiguous identification of these phases. Data show the possibility to discriminate individual species of similar whitish color and aspect. Measurements showed an excellent correspondence of Raman bands obtained using the portable system and a laboratory Raman microspectrometer (with the same excitation laser wavelenght). However, for several minerals of these groups (chrysoberyl, bertrandite, chiavennite) Raman spectra were not of sufficient quality to permit unambiguous identification. The reasons are discussed. Raman spectrum of chiavennite CaMnBe(2)Si(5)O(13)(OH)(2)·2(H(2)O) - a transformation product occurring together with bavenite on the surface of beryl crystals was obtained for the first time using the laboratory Raman spectrometer. PMID:22099060

  3. Absorption at 11 μm in the interstellar medium and embedded sources: evidence for crystalline silicates

    NASA Astrophysics Data System (ADS)

    Wright, Christopher M.; Do Duy, Tho; Lawson, Warrick

    2016-04-01

    An absorption feature is occasionally reported around 11 μm in astronomical spectra, including those of forming stars. Candidate carriers include water ice, polycyclic aromatic hydrocarbons, silicon carbide, crystalline silicates or even carbonates. All are known constituents of cosmic dust in one or more types of environments, though not necessarily together. In this paper, we present new ground-based 8-13 μm spectra of one evolved star, several embedded young stellar objects and a background source lying behind a large column of the interstellar medium (ISM) towards the Galactic Centre. Our observations, obtained at a spectral resolution of ˜100, are compared with previous lower resolution data, as well as data obtained with the Infrared Space Observatory (ISO) on these and other targets. By presenting a subset of a larger sample, our aim is to establish the reality of the feature and subsequently speculate on its carrier. All evidence points towards crystalline silicate. For instance, the 11 μm band profile is well matched with the emissivity of crystalline olivine. Furthermore, the apparent association of the absorption feature with a sharp polarization signature in the spectrum of two previously reported cases suggests a carrier with a relatively high band strength compared to amorphous silicates. If true, this would either set back the evolutionary stage in which silicates are crystallized, either to the embedded phase or even before within the ISM, or else the silicates ejected from the outflows of evolved stars retain some of their crystalline identity during their long residence in the ISM.

  4. Endotoxin removal using a synthetic adsorbent of crystalline calcium silicate hydrate.

    PubMed

    Zhang, John P; Wang, Qun; Smith, Timothy R; Hurst, William E; Sulpizio, Thomas

    2005-01-01

    A synthetic adsorbent of crystalline calcium silicate hydrate, the product LRA by Advanced Minerals Corp., has been studied for endotoxin removal from aqueous solutions. This adsorbent removes endotoxin effectively, and the removal is greatly enhanced by the presence of an electrolyte such as NaCl, Tris-HCl, or Na2HPO4. It has an endotoxin removal capacity as high as 6 million endotoxin units (EU) per gram. Its endotoxin removal kinetics is fast, and for instance, over 99.9% endotoxin in a 5000 EU/mL solution was removed by mixing for 2 min at an adsorbent usage of 10 g/L. Using the chromatographic column method to treat a 5000 EU/mL solution, an endotoxin log-reduction factor of 6.2 was achieved with a single pass. This adsorbent also demonstrated significantly better performance when compared to many commonly used endotoxin removal agents, such as ActiClean Etox Endotoxin Removal Resin, Affi-Prep Polymyxin Support, Detroxi-Gel Endotoxin Removing Gel, Q Sepharose Fast Flow Media, and Sigma Endotoxin Removal Solution. Furthermore, it demonstrated a high selective removal of endotoxin from a solution of lambda DNA. This adsorbent provides opportunities for developing disposable, scaleable, and cost-effective methods for endotoxin reduction in many biotechnological and pharmaceutical processes. PMID:16080705

  5. A vibrational spectroscopic study of the silicate mineral harmotome--(Ba,Na,K)1-2(Si,Al)8O16?6H2O--a natural zeolite.

    PubMed

    Frost, Ray L; Lpez, Andrs; Wang, Lina; Romano, Antnio Wilson; Scholz, Ricardo

    2015-02-25

    The mineral harmotome (Ba,Na,K)1-2(Si,Al)8O16?6H2O is a crystalline sodium calcium silicate which has the potential to be used in plaster boards and other industrial applications. It is a natural zeolite with catalytic potential. Raman bands at 1020 and 1102 cm(-1) are assigned to the SiO stretching vibrations of three dimensional siloxane units. Raman bands at 428, 470 and 491 cm(-1) are assigned to OSiO bending modes. The broad Raman bands at around 699, 728, 768 cm(-1) are attributed to water librational modes. Intense Raman bands in the 3100 to 3800 cm(-1) spectral range are assigned to OH stretching vibrations of water in harmotome. Infrared spectra are in harmony with the Raman spectra. A sharp infrared band at 3731 cm(-1) is assigned to the OH stretching vibration of SiOH units. Raman spectroscopy with complimentary infrared spectroscopy enables the characterization of the silicate mineral harmotome. PMID:25203212

  6. A comparative study of the continuum and emission characteristics of comet dust. 1: Are the silicates in Comet Halley and Kohoutek amorphous or crystalline

    NASA Technical Reports Server (NTRS)

    Nansheng, Zhao; Greenberg, J. Mayo; Hage, J. I.

    1989-01-01

    A continuum emission was subtracted from the 10 micron emission observed towards comets Halley and Kohoutek. The 10 micron excess emissions were compared with BN absorption and laboratory amorphous silicates. The results show that cometary silicates are predominantly amorphous which is consistent with the interstellar dust model of comets. It is concluded that cometary silicates are predominantly similar to interstellar silicates. For a periodic comet like Comet Halley, it is to be expected that some of the silicate may have been heated enough to convert to crystalline form. But apparently, this is only a small fraction of the total. A comparison of Comet Halley silicates with a combination of the crystalline forms observed in interplanetary dust particles (IPDs) seemed reasonable at first sight (Walker 1988, Brownlee 1988). But, if true, it would imply that the total silicate mass in Comet Halley dust is lower than that given by mass spectrometry data of Kissel and Krueger (1987). They estimated m sub org/m sub sil = 0.5 while using crystalline silicate to produce the 10 micron emission would give m sub org/m sub sil = 5 (Greenberg et al. 1988). This is a factor of 10 too high.

  7. Petrologic Constraints on Amorphous and Crystalline Magnesium Silicates: Dust Formation and Evolution in Selected Herbig Ae/Be Systems

    NASA Astrophysics Data System (ADS)

    Rietmeijer, Frans J. M.; Nuth, Joseph A.

    2013-07-01

    The Infrared Space Observatory, Spitzer Space Telescope, and Herschel Space Observatory surveys provided a wealth of data on the Mg-silicate minerals (forsterite, enstatite), silica, and "amorphous silicates with olivine and pyroxene stoichiometry" around Herbig Ae/Be stars. These incredible findings do not resonate with the mainstream Earth Sciences because of (1) disconnecting "astronomical nomenclature" and the long existing mineralogical and petrologic terminology of minerals and amorphous materials, and (2) the fact that Earth scientists (formerly geologists) are bound by the "Principle of Actualism" that was put forward by James Hutton (1726-1797). This principle takes a process-oriented approach to understanding mineral and rock formation and evolution. This paper will (1) review and summarize the results of laboratory-based vapor phase condensation and thermal annealing experiments, (2) present the pathways of magnesiosilica condensates to Mg-silicate mineral (forsterite, enstatite) formation and processing, and (3) present mineralogical and petrologic implications of the properties and compositions of the infrared-observed crystalline and amorphous dust for the state of circumstellar disk evolution. That is, the IR-observation of smectite layer silicates in HD142527 suggests the break-up of asteroid-like parent bodies that had experienced aqueous alteration. We discuss the persistence of amorphous dust around some young stars and an ultrafast amorphous to crystalline dust transition in HD 163296 that leads to forsterite grains with numerous silica inclusions. These dust evolution processes to form forsterite, enstatite tridymite could occur due to amorphous magnesiosilica dust precursors with a serpentine- or smectite-dehydroxylate composition.

  8. PETROLOGIC CONSTRAINTS ON AMORPHOUS AND CRYSTALLINE MAGNESIUM SILICATES: DUST FORMATION AND EVOLUTION IN SELECTED HERBIG Ae/Be SYSTEMS

    SciTech Connect

    Rietmeijer, Frans J. M.; Nuth, Joseph A.

    2013-07-01

    The Infrared Space Observatory, Spitzer Space Telescope, and Herschel Space Observatory surveys provided a wealth of data on the Mg-silicate minerals (forsterite, enstatite), silica, and ''amorphous silicates with olivine and pyroxene stoichiometry'' around Herbig Ae/Be stars. These incredible findings do not resonate with the mainstream Earth Sciences because of (1) disconnecting ''astronomical nomenclature'' and the long existing mineralogical and petrologic terminology of minerals and amorphous materials, and (2) the fact that Earth scientists (formerly geologists) are bound by the ''Principle of Actualism'' that was put forward by James Hutton (1726-1797). This principle takes a process-oriented approach to understanding mineral and rock formation and evolution. This paper will (1) review and summarize the results of laboratory-based vapor phase condensation and thermal annealing experiments, (2) present the pathways of magnesiosilica condensates to Mg-silicate mineral (forsterite, enstatite) formation and processing, and (3) present mineralogical and petrologic implications of the properties and compositions of the infrared-observed crystalline and amorphous dust for the state of circumstellar disk evolution. That is, the IR-observation of smectite layer silicates in HD142527 suggests the break-up of asteroid-like parent bodies that had experienced aqueous alteration. We discuss the persistence of amorphous dust around some young stars and an ultrafast amorphous to crystalline dust transition in HD 163296 that leads to forsterite grains with numerous silica inclusions. These dust evolution processes to form forsterite, enstatite {+-} tridymite could occur due to amorphous magnesiosilica dust precursors with a serpentine- or smectite-dehydroxylate composition.

  9. Pure, single phase, high crystalline, chamfered-edge zeolite 4A synthesized from coal fly ash for use as a builder in detergents.

    PubMed

    Hui, K S; Chao, C Y H

    2006-09-01

    Single phase chamfered-edge zeolite 4A samples in pure form with a high crystallinity were synthesized by applying step-change of synthesis temperature during hydrothermal treatment of coal fly ash. The calcium binding capacity of these zeolite 4A samples (prepared from coal fly ash) and the commercial detergent grade zeolite 4A were tested for usage as a detergent builder. The results show that these zeolite 4A samples behaved similarly as the commercial one in removing calcium ions during the washing cycle. Moreover, from the leaching tests (evaluation of toxicological safety), the results show that these zeolite 4A samples leached the same elements (Sb, As, Se and Tl) as the commercial one with the concentrations in the same order of magnitude. This shows that the toxicological effect of the coal fly ash converted zeolite 4A was not worse than that of the commercial sample. Finally, economic and environmental aspects of converting coal fly ash to useful products were discussed. PMID:16621273

  10. Review of the thermal stability and cation exchange properties of the zeolite minerals clinoptilolite, mordenite, and analcime; applications to radioactive waste isolation in silicic tuff

    SciTech Connect

    Smyth, J.R.; Caporuscio, F.A.

    1981-06-01

    Silicic tuffs of the southern Great Basin and basalts of the Columbia River Plateau are under investigation as potential host rocks for high- and intermediate-level radioactive wastes. Nonwelded and partially welded tuffs may contain major amounts (> 50%) of the zeolite minerals clinoptilolite, mordenite, and analcime. Densely welded tuffs and some basalt flows may contain clinoptilolite as fracture filling that limits the permeability of these rocks. The cation exchange properties of these zeolite minerals allow them to pose a formidable natural barrier to the migration of cationic species of various radionuclides in aqueous solutions. However, these minerals are unstable at elevated temperatures and at low water-vapor pressures and may break down either by reversible dehydration or by irreversible mineralogical reactions. All the breakdown reactions occurring at increased temperature involve a net volume reduction and evolution of fluids. Thus, they may provide a pathway (shrinkage fractures) and a driving force (fluid pressure) for release of radionuclides to the biosphere. These reactions may be avoided by keeping zeolite-bearing horizons saturated with water and below about 85{sup 0}C. This may restrict allowable gross thermal loadings in waste repositories in volcanic rocks.

  11. Characterization of the structural and electronic properties of crystalline lithium silicates

    SciTech Connect

    Du, Jincheng; Corrales, Louis R.

    2006-10-14

    Structures of several lithium silicate crystals were fully optimized by minimizing the total energy with respect to atom position and lattice parameters using density functional theory (DFT) calculations within the generalized gradient approximation (GGA). Electronic density of states and atomic charges were calculated on the optimized structures. The relative stability of two forms of lithium disilicate determined from density functional theory calculations agree well with experimental results. Partial electronic density of states of different elements and crystallographical sites were determined. The results show bridging and non-bridging oxygen (oxygen ions that bond to two or one silicon ions, respectively) have distinguishable contributions to the oxygen 2s and upper valence bands. Hirshfeld and Bader population analysis were performed to obtain atomic charges of the crystals. Combining the understanding of the silicate crystal chemistry, we found that the Hirshfeld method correctly predicts relative charges of bridging and non-bridging oxygen ions thus provide additional evidence that the Hirshfeld charges better represent the bond ionicity of the silicon-oxygen bonds.

  12. Lyotropic liquid crystalline L3 phase silicated nanoporous monolithic composites and their production

    DOEpatents

    McGrath, Kathryn M.; Dabbs, Daniel M.; Aksay, Ilhan A.; Gruner, Sol M.

    2003-10-28

    A mesoporous ceramic material is provided having a pore size diameter in the range of about 10-100 nanometers produced by templating with a ceramic precursor a lyotropic liquid crystalline L.sub.3 phase consisting of a three-dimensional, random, nonperiodic network packing of a multiple connected continuous membrane. A preferred process for producing the inesoporous ceramic material includes producing a template of a lyotropic liquid crystalline L.sub.3 phase by mixing a surfactant, a co-surfactant and hydrochloric acid, coating the template with an inorganic ceramic precursor by adding to the L.sub.3 phase tetramethoxysilane (TMOS) or tetraethoxysilane (TEOS) and then converting the coated template to a ceramic by removing any remaining liquids.

  13. Synthesis strategies in the search for hierarchical zeolites.

    PubMed

    Serrano, D P; Escola, J M; Pizarro, P

    2013-05-01

    Great interest has arisen in the past years in the development of hierarchical zeolites, having at least two levels of porosities. Hierarchical zeolites show an enhanced accessibility, leading to improved catalytic activity in reactions suffering from steric and/or diffusional limitations. Moreover, the secondary porosity offers an ideal space for the deposition of additional active phases and for functionalization with organic moieties. However, the secondary surface represents a discontinuity of the crystalline framework, with a low connectivity and a high concentration of silanols. Consequently, hierarchical zeolites exhibit a less "zeolitic behaviour" than conventional ones in terms of acidity, hydrophobic/hydrophilic character, confinement effects, shape-selectivity and hydrothermal stability. Nevertheless, this secondary surface is far from being amorphous, which provides hierarchical zeolites with a set of novel features. A wide variety of innovative strategies have been developed for generating a secondary porosity in zeolites. In the present review, the different synthetic routes leading to hierarchical zeolites have been classified into five categories: removal of framework atoms, surfactant-assisted procedures, hard-templating, zeolitization of preformed solids and organosilane-based methods. Significant advances have been achieved recently in several of these alternatives. These include desilication, due to its versatility, dual templating with polyquaternary ammonium surfactants and framework reorganization by treatment with surfactant-containing basic solutions. In the last two cases, the materials so prepared show both mesoscopic ordering and zeolitic lattice planes. Likewise, interesting results have been obtained with the incorporation of different types of organosilanes into the zeolite crystallization gels, taking advantage of their high affinity for silicate and aluminosilicate species. Crystallization of organofunctionalized species favours the formation of organic-inorganic composites that, upon calcination, are transformed into hierarchical zeolites. However, in spite of this impressive progress in novel strategies for the preparation of hierarchical zeolites, significant challenges are still ahead. The overall one is the development of methods that are versatile in terms of zeolite structures and compositions, capable of tuning the secondary porosity properties, and being scaled up in a cost-effective way. Recent works have demonstrated that it is possible to scale-up easily the synthesis of hierarchical zeolites by desilication. Economic aspects may become a significant bottleneck for the commercial application of hierarchical zeolites since most of the synthesis strategies so far developed imply the use of more expensive procedures and reagents compared to conventional zeolites. Nevertheless, the use of hierarchical zeolites as efficient catalysts for the production of high value-added compounds could greatly compensate these increased manufacturing costs. PMID:23138888

  14. Synthesis of zeolite Li-ABW from fly ash by fusion method.

    PubMed

    Yao, Z T; Xia, M S; Ye, Y; Zhang, L

    2009-10-30

    The zeolite Li-ABW was synthesized by fusion method using fly ash as raw material. It comprised alkaline fusion followed by hydrothermal treatment in LiOH x H2O medium. Crystallinity of zeolite as high as 97.8% was attained under the following conditions: LiOH x H2O concentration, 3M; hydrothermal temperature, 180 degrees C; the corresponding aging time, 12 h. The content of Li-ABW increased at the expense of lithium aluminum silicate or quartz with an increase of LiOH x H2O concentration. With increasing hydrothermal temperature and aging time, the soluble species re-crystallized and crystalline phase transformation between different zeolites was observed. Scanning electron microscopy (SEM) observation revealed that the obtained zeolite Li-ABW was a rod-like crystal. The pore size distribution curve indicated the presence of mesopores. PMID:19493616

  15. Permeability Change of Crystalline Silicate Mineral-Packed Bed Column by Highly Alkaline Plume

    SciTech Connect

    Hideo Usui; Yuichi Niibori; Hitoshi Mimura; Osamu Tochiyama

    2007-07-01

    For the construction of the geological disposal system, the use of the cementitious material may change the permeability of the natural barrier around the repository. Cementitious materials may alter the pH of ground water to highly alkaline. Also, the potential permeability change of the natural barrier is one of the notable factors for performance assessments of geological disposal systems. In the high pH region, the solubility of silica is very high compared to that in the natural pH (around 8). Therefore, highly alkaline groundwater would dissolve and alter a part of rock surface. Usui et al. (2005) reported that the change of mineral pore structure due to chemical reaction is the key factor to consider the change of the permeability [5-6]. Moreover, such a change of the pore structure was considered to be the result of the spatial heterogeneity of chemical composition. Since such spatial heterogeneity exists also in the sedimentary rocks consisting of crystalline minerals such as quartz and feldspar, we need to examine natural rock, in order to obtain more reliable understanding about the change of permeability induced by highly alkaline groundwater (plume). In this study, silica sand as crystalline mineral was packed in the column, and the effect of dissolution induced by the highly alkaline plume on the permeability-change was examined. The silica sand particles mainly consist of SiO{sub 2} and include Al{sub 2}O{sub 3}, FeO, and K{sub 2}O. The volumetric flow rate and the pressure difference between the inlet and outlet of the column were measured, and the permeability was calculated. At the same time, the concentrations of elements in the fluid were measured by ICP-AES. The experimental result showed that permeability decreased gradually, although the silica sand was continuously dissolved in the column. The behavior of the permeability is considered to be the result from the rearrangement of the particles, or precipitation of secondary mineral. In the column test using the silica sand as packed mineral, the flow-path seems to be clogged by the rearrangement of the particles rather than the increase of the pore space between the particles. (authors)

  16. A simple and general route for the preparation of pure and high crystalline nanosized lanthanide silicates with the structure of apatite at low temperature

    SciTech Connect

    Ferdov, Stanislav; Rauwel, Protima; Lin, Zhi; Ferreira, Rute A. Sa; Lopes, Augusto

    2010-11-15

    Rare earth silicates with the structure of apatite are attracting considerable interest since they show oxygen ion conductivities higher than that of yttria-stabilized zirconia (YSZ) at moderate temperature. Based on the hydrothermal synthesis we presented a simple one step process for the direct preparation of the pure and the high crystalline nanosized rare earth silicates with the structure of apatite under a mild condition (230 {sup o}C). Since the preparation of the high crystalline silicon based rare earth apatites is performed at high temperature previously and accompanied by subsequent process of grinding, results of this work provide a promising alternative of the existing methodology. Furthermore, due to the relatively low temperature of the preparation of these materials, high doping of monovalent cation can be done, which was not achieved before. -- Graphical abstract: A simple one step process for the preparation of the rare earth silicates with the structure of apatite under a mild condition (230 {sup o}C) is presented. The process is based on the hydrothermal synthesis and the obtained powder materials are pure, high crystalline and with nanosize. Display Omitted

  17. Towards a full understanding of the nature of Ni(ii) species and hydroxyl groups over highly siliceous HZSM-5 zeolite supported nickel catalysts prepared by a deposition-precipitation method.

    PubMed

    Chen, Bao-Hui; Chao, Zi-Sheng; He, Hao; Huang, Chen; Liu, Ya-Juan; Yi, Wen-Jun; Wei, Xue-Ling; An, Jun-Fang

    2016-02-14

    Highly siliceous HZSM-5 zeolite supported nickel catalysts prepared by a deposition-precipitation (D-P) method were characterized by Fourier transform infrared (FT-IR), hydrogen temperature programmed reduction (H2-TPR), X-ray diffraction (XRD), N2-absorption/desorption, field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and (27)Al magic-angle nuclear magnetic resonance (MAS NMR) techniques. The results showed that the D-P of nickel species occurred predominantly on the internal surface of highly siliceous HZSM-5 zeolite, in which the internal silanol groups located on the hydroxylated mesopores or nanocavities played a key role. During the D-P process, nickel hydroxide was first deposited-precipitated via olation/polymerization of neutral hydroxoaqua nickel species over the HZSM-5 zeolite. With the progress of the D-P process, 1 : 1 nickel phyllosilicate was formed over the HZSM-5 via the hetero-condensation/polymerization between charged hydroxoaqua nickel species and monomer silicic species generated due to the partial dissolution of the HZSM-5 framework. The 1 : 1 nickel phyllosilicate could also be generated via the hydrolytic adsorption of hydroxoaqua nickel species and their subsequent olation condensation. After calcination, the deposited-precipitated nickel hydroxide was decomposed into nickel oxide, while the 1 : 1 nickel phyllosilicate was transformed into 2 : 1 nickel phyllosilicate. According to the above mechanism, Ni(ii) species were present both in the form of nickel oxide and 2 : 1 nickel phyllosilicate, which were mutually separated from each other, being highly dispersed over HZSM-5 zeolite. PMID:26745008

  18. Rapid synthesis of beta zeolites

    SciTech Connect

    Fan, Wei; Chang, Chun -Chih; Dornath, Paul; Wang, Zhuopeng

    2015-08-18

    The invention provides methods for rapidly synthesizing heteroatom containing zeolites including Sn-Beta, Si-Beta, Ti-Beta, Zr-Beta and Fe-Beta. The methods for synthesizing heteroatom zeolites include using well-crystalline zeolite crystals as seeds and using a fluoride-free, caustic medium in a seeded dry-gel conversion method. The Beta zeolite catalysts made by the methods of the invention catalyze both isomerization and dehydration reactions.

  19. IRAS 15099-5856: REMARKABLE MID-INFRARED SOURCE WITH PROMINENT CRYSTALLINE SILICATE EMISSION EMBEDDED IN THE SUPERNOVA REMNANT MSH15-52

    SciTech Connect

    Koo, Bon-Chul; Kim, Hyun-Jeong; Im, Myungshin; McKee, Christopher F.; Suh, Kyung-Won; Moon, Dae-Sik; Lee, Ho-Gyu; Onaka, Takashi; Burton, Michael G.; Hiramatsu, Masaaki; Bessell, Michael S.; Gaensler, B. M.; Lee, Jae-Joon; Jeong, Woong-Seob; Tatematsu, Ken'ichi; Kawabe, Ryohei; Ezawa, Hajime; Kohno, Kotaro; Wilson, Grant; Yun, Min S.

    2011-05-01

    We report new mid-infrared (MIR) observations of the remarkable object IRAS 15099-5856 using the space telescopes AKARI and Spitzer, which demonstrate the presence of prominent crystalline silicate emission in this bright source. IRAS 15099-5856 has a complex morphology with a bright central compact source (IRS1) surrounded by knots, spurs, and several extended ({approx}4') arc-like filaments. The source is seen only at {>=}10 {mu}m. The Spitzer mid-infrared spectrum of IRS1 shows prominent emission features from Mg-rich crystalline silicates, strong [Ne II] 12.81 {mu}m, and several other faint ionic lines. We model the MIR spectrum as thermal emission from dust and compare with the Herbig Be star HD 100546 and the luminous blue variable R71, which show very similar MIR spectra. Molecular line observations reveal two molecular clouds around the source, but no associated dense molecular cores. We suggest that IRS1 is heated by UV radiation from the adjacent O star Muzzio 10 and that its crystalline silicates most likely originated in a mass outflow from the progenitor of the supernova remnant (SNR) MSH 15-52. IRS1, which is embedded in the SNR, could have been shielded from the SN blast wave if the progenitor was in a close binary system with Muzzio 10. If MSH 15-52 is a remnant of Type Ib/c supernova (SN Ib/c), as has been previously proposed, this would confirm the binary model for SN Ib/c. IRS1 and the associated structures may be the relics of massive star death, as shaped by the supernova explosion, the pulsar wind, and the intense ionizing radiation of the embedded O star.

  20. Zeolite exposure and associated pneumoconiosis

    SciTech Connect

    Casey, K.R.; Shigeoka, J.W.; Rom, W.N.; Moatamed, F.

    1985-06-01

    Naturally occurring zeolite minerals are aluminum silicates widespread in the earth's crust. Several of these minerals have fibrous forms and have been implicated as a possible cause of benign and malignant diseases of the lung and pleura in Turkey. This report describes a patient, living in an area of Nevada rich in zeolites, who presented with idiopathic pleural thickening and pulmonary fibrosis associated with extensive pulmonary deposition of zeolites.

  1. A vibrational spectroscopic study of the silicate mineral analcime - Na2(Al4SiO4O12)2H2O - A natural zeolite

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; Lpez, Andrs; Theiss, Frederick L.; Romano, Antnio Wilson; Scholz, Ricardo

    2014-12-01

    We have studied the mineral analcime using a combination of scanning electron microscopy with energy dispersive spectroscopy and vibrational spectroscopy. The mineral analcime Na2(Al4SiO4O12)2H2O is a crystalline sodium silicate. Chemical analysis shows the mineral contains a range of elements including Na, Al, Fe2+ and Si. The mineral is characterized by intense Raman bands observed at 1052, 1096 and 1125 cm-1. The infrared bands are broad; nevertheless bands may be resolved at 1006 and 1119 cm-1. These bands are assigned to SiO stretching vibrational modes. Intense Raman band at 484 cm-1 is attributed to OSiO bending modes. Raman bands observed at 2501, 3542, 3558 and 3600 cm-1 are assigned to the stretching vibrations of water. Low intensity infrared bands are noted at 3373, 3529 and 3608 cm-1. The observation of multiple water bands indicate that water is involved in the structure of analcime with differing hydrogen bond strengths. This concept is supported by the number of bands in the water bending region. Vibrational spectroscopy assists with the characterization of the mineral analcime.

  2. Cesium titanium silicate and method of making

    DOEpatents

    Balmer, Mari L.

    1997-01-01

    The invention is the new material, a ternary compound of cesium, silica, and titania, together with a method of making the ternary compound, cesium titanium silicate pollucite. More specifically, the invention is Cs.sub.2 Ti.sub.2 Si.sub.4 O.sub.13 pollucite which is a new crystalline phase representing a novel class of Ti-containing zeolites. Compositions contain relatively high Cs.sub.2 O and TiO.sub.2 loadings and are durable glass and ceramic materials. The amount of TiO.sub.2 and Cs.sub.2 that can be incorporated into these glasses and crystalline ceramics far exceeds the limits set for the borosilicate high level waste glass.

  3. Cesium titanium silicate and method of making

    DOEpatents

    Balmer, M.L.

    1997-01-07

    The invention is the new material, a ternary compound of cesium, silica, and titania, together with a method of making the ternary compound, cesium titanium silicate pollucite. More specifically, the invention is Cs{sub 2}Ti{sub 2}Si{sub 4}O{sub 13} pollucite which is a new crystalline phase representing a novel class of Ti-containing zeolites. Compositions contain relatively high Cs{sub 2}O and TiO{sub 2} loadings and are durable glass and ceramic materials. The amount of TiO{sub 2} and Cs{sub 2} that can be incorporated into these glasses and crystalline ceramics far exceeds the limits set for the borosilicate high level waste glass. 10 figs.

  4. Radiation effects and annealing kinetics in crystalline silicates, phosphates and complex Nb-Ta-Ti oxides. FInal Report

    SciTech Connect

    Ewing, R.C.

    1987-08-10

    Interaction of heavy particles (alpha-recoil nuclei, fission fragments, implanted ions) with ceramics is complex because they have a wide range of structure types, complex compositions and chemical bonding is variable. Radiation damage can produce diverse results, but most commonly, crystalline periodic materials become either polycrystalline or aperiodic (metamict state). We studied the transition from crystalline to aperiodic state in natural materials that have been damaged by alpha recoil nuclei in the U and Th decay series and in synthetic, analogous structure types which have been amorphized by ion implantation. Transition from crystalline to aperiodic was followed by analysis of XRD, high resolution TEM, and EXAFS/XANE spectroscopy. Use of these techniques with increasing dose provided data on an increasing finer scale as the damage process progressed.

  5. Zeolite with trimodal porosity by desilication of zeolite nanocrystals aggregate

    SciTech Connect

    Wang Yuxin; Liu Kaituo; Graduate School of the Chinese Academy of Sciences, Beijing 100049 ; He Tao; Wu Jinhu; Fang Yunming

    2012-10-15

    Zeolite with trimodal porosity can be synthesized by desilication of zeolite nanocrystal aggregate. In the desilication process, the originally existed intercrystalline mesopores of zeolite nanocrystal aggregate were enlarged into large mesopore, and the new small intracrystalline mesopore channel was created, thus the Zeolite with trimodal porosity was formed. The structure of resulted zeolite, both on aggregate and mesopore level can be fine tuned by the desilication degree. - Graphical abstract: The Si from the edges and boundary of nanocrystals was first removed resulted the surface roughness and enlarges of the originally existed intercrystalline mesopores. As the degree of alkali-treatment increasing, the Si species inside zeolite nanocrystals was also removed, leading to further enlarges the intercrystalline mesopores and the formation of small intracrystalline mesopores. In case the alkali-treatment is serve enough to completely dissolve the bridges between zeolite nanocrystals, zeolite nanocrystals were exfoliated from the aggregate. Highlights: Black-Right-Pointing-Pointer Zeolite with trimodal porosity by desilication of zeolite nanocrystals aggregate. Black-Right-Pointing-Pointer The original intercrystalline mesopores were enlarged into large mesopore. Black-Right-Pointing-Pointer The new intracrystalline mesopores were created as the inside Si extracted out. Black-Right-Pointing-Pointer The aggregate structure, crystallinity and acidity of parent zeolite remained. Black-Right-Pointing-Pointer Desilication is start on the edges then in the inner part of zeolite.

  6. Spectroscopic analysis of Eu{sup 3+} -and Eu{sup 3+}:Yb{sup 3+}-doped yttrium silicate crystalline powders prepared by combustion synthesis

    SciTech Connect

    Rakov, Nikifor; Amaral, Dayanne F.; Guimaraes, Renato B.; Maciel, Glauco S.

    2010-10-15

    Yttrium silicate powders doped with Eu{sup 3+} and codoped with Eu{sup 3+} and Yb{sup 3+} were prepared by combustion synthesis. The x-ray powder diffraction data showed the presence of Y{sub 2}SiO{sub 5} and Y{sub 2}Si{sub 2}O{sub 7} crystalline phases. Singly doped (1 wt %) sample illuminated with ultraviolet light ({lambda}=256 nm) showed the characteristic red luminescence corresponding to {sup 5}D{sub 0}{yields}{sup 7}F{sub J} transitions of Eu{sup 3+}. The Judd-Ofelt intensity parameters were calculated from experimental data and the radiative and nonradiative relaxation rates were estimated. The results showed that the nonradiative relaxation rate is smaller in yttrium silicate compared to yttrium oxide powder, a reference material, prepared under similar conditions. Codoped samples were exposed to near-infrared laser excitation ({lambda}=975 nm) and the red luminescence of Eu{sup 3+} was also observed. In this case, the luminescence is achieved due to a cooperative upconversion (CUC) process involving energy transfer (ET) from pairs of ytterbium ions to europium ions. The ET rate was estimated by fitting a rate equation model with the dynamics of CUC red emission.

  7. Lack of Evidence of In-Situ Decay of Aluminum-26 in a FeO-Poor Ferromagnesian Crystalline Silicate Particle, Pyxie, from Comet Wild 2

    NASA Technical Reports Server (NTRS)

    Nakashima, D.; Ushikubo, T.; Weisberg, M. K.; Zolensky, M. E.; Ebel, D. S.; Kita, N. T.

    2014-01-01

    One of the important discoveries from the Stardust mission is the observation of crystalline silicate particles that resemble Ca, Al-rich inclusions (CAIs) and chondrules in carbonaceous chondrites], which suggests radial transport of high temperature solids from the inner to the outer solar nebula regions and capture by accreting cometary objects. The Al-Mg isotope analyses of CAI-like and type II chondrule-like particles revealed no excess of Mg-26 derived from in-situ decay of Al-26 (Tau)(sub 1/2) = 0.705Myr; ), suggesting late formation of these particles. However, the number of Wild 2 particles analyzed for Al-Mg isotopes is still limited (n = 3). In order to better understand the timing of the formation of Wild 2 particles and possible radial transport in the protoplanetary disk, we performed SIMS (Secondary Ion Mass Spectrometer) Al-Mg isotope analyses of plagioclase in a FeO-poor ferromagnesian Wild 2 particle, which is the most abundant type among crystalline Wild 2 particles.

  8. Raman spectroscopic study of the synthesis of zeolite Y

    SciTech Connect

    Dutta, P.K.; Shieh, D.C.; Puri, M.

    1987-04-23

    The formation of zeolite Y from colloidal silica and soluble silicate species was investigated by Raman spectroscopy. The role of aging of the reactant mixture was studied. During the nucleation period, the solid amorphous phase consists of predominantly six-membered aluminosilicate rings, which act as building blocks for the formation of zeolite Y. It is essential to have polymeric, highly condensed silicate units as a reactant if zeolite Y crystallization is to take place.

  9. Crystalline Membranes

    NASA Technical Reports Server (NTRS)

    Tsapatsis, Michael (Inventor); Lai, Zhiping (Inventor)

    2008-01-01

    In certain aspects, the invention features methods for forming crystalline membranes (e.g., a membrane of a framework material, such as a zeolite) by inducing secondary growth in a layer of oriented seed crystals. The rate of growth of the seed crystals in the plane of the substrate is controlled to be comparable to the rate of growth out of the plane. As a result, a crystalline membrane can form a substantially continuous layer including grains of uniform crystallographic orientation that extend through the depth of the layer.

  10. Constructing Hierarchical Porous Zeolites via Kinetic Regulation.

    PubMed

    Ding, Kunlun; Corma, Avelino; Maci-Agull, Juan Antonio; Hu, Jerry G; Krmer, Stephan; Stair, Peter C; Stucky, Galen D

    2015-09-01

    Zeolites are crystalline inorganic solids with microporous structures, having widespread applications in the fields of catalysis, separation, adsorption, microelectronics, and medical diagnosis. A major drawback of zeolites is the mass transfer limitation due to the small size of the micropores (less than 1 nm). Numerous efforts have been dedicated to integrating mesopores with the microporous zeolite structures by using templating and/or destructive approaches. Here we provide a new strategy for hierarchical pore size zeolite synthesis, without using supramolecular or hard templates. The branching epitaxial growth behavior, as a result of aluminum-zoning, contributes to the formation of the hierarchical porous zeolite structures. PMID:26322625

  11. Synthesis and testing of nanosized zeolite Y

    NASA Astrophysics Data System (ADS)

    Karami, Davood

    This work focuses on the synthesis and testing of nanosized zeolite Y. The synthesis formulations of faujasite-type structure of zeolite Y prepared in nanosized form are described. The synthetic zeolite Y is the most widely employed for the preparation of fluid catalytic cracking (FCC) catalysts. The synthesis of zeolite Y is very complicated process. The mean particle size of zeolite Y is 1800 nm. The major challenge of this work involved reducing this average particle size to less than 500 nm. The preliminary experiments were conducted to obtain the pure zeolite Y using the soluble silicates as a silica source. This was achieved by applying the experimental design approach to study the effects of many parameters. The ageing time turned out to be the most significant variable affecting product purity. Based on the preliminary results, a detailed investigation was carried out to determine the effects of silica-alumina precursor preparations on zeolite Y synthesis. Aluminosilicate precursors were prepared by gelling and precipitation of soluble silicate. The as-prepared precursors were used for the hydrothermal synthesis of zeolite Y. The procedure of the precipitation of soluble silicate yielded pure zeolite Y at the conventional synthesis conditions. The extent of purity of zeolite Y depends on the surface areas of aluminosilicate precursors. A novel approach to zeolite Y synthesis was employed for the preparation of the pure nanosized zeolite Y. This was achieved by applying the method of impregnation of precipitated silica. This novel method of impregnation for zeolite Y preparation allows eliminating the vigorous agitation step required for the preparation of a homogeneous silica solution, thereby simplifying the synthesis of zeolite Y in one single vessel. In case of the synthesis of nanosized zeolite Y, the effect of varying the organic templates on the formation of nanosized particles of zeolite Y was investigated, while all other reaction parameters were kept constant. The extent to which the nanosized zeolite Y was formed depended on the types and amount of the organic templates as well as the ageing duration. The activity testing of four FCC catalysts prepared by using CREY (Calcined Rare Earth ion-exchanged) zeolites with different particle sizes was carried out in a fluidized bench-scale batch riser simulator reactor. The starting zeolites NaY of different particle sizes were subjected to two cycles of ion exchange treatment. The particle size of the supported zeolites was varied between 150 and 1800 nm. The preparation of FCC catalysts was conducted by mixing the CREY zeolite with silica-alumina matrix and silica sol binder. Each catalyst contained 25% zeolite. The results of catalytic cracking demonstrated the significant effect of size reduction of the starting zeolite Y on catalytic performance of FCC catalyst. Keywords. Zeolite NaY, Faujasite, Nanosized particles, Nanozeolite, Nanotechnology, Synthesis, Crystallization, Seeding, Ageing, Precipitated silica, Sylopol silica, Fumed silica, Silica sol, Soluble silicates, Alumina, SAR or SiO2/Al2O3 Ratios, Sodium hydroxide, Sodium aluminate, Organic templates, TMAOH, Surfactant (CTAB), Ammonium Sulfate, BET surface area, BJH Pore Size Distribution, Zetasizer Particle Size Distribution, Powder XRD, 27Al Solid-State NMR, Catalytic Impregnation, CREY Zeolite, Silica-Alumina Matrix, Ion Exchange, FCC Catalyst, Catalytic cracking, Riser SimulatorRTM, Steaming, Zeolite HY, Utrastable Zeolite Y (USY)

  12. Effect of different glasses in glass bonded zeolite

    SciTech Connect

    Lewis, M.A.; Ackerman, J.P.; Verma, S.

    1995-05-01

    A mineral waste form has been developed for chloride waste salt generated during the pyrochemical treatment of spent nuclear fuel. The waste form consists of salt-occluded zeolite powders bound within a glass matrix. The zeolite contains the salt and immobilizes the fission products. The zeolite powders are hot pressed to form a mechanically stable, durable glass bonded zeolite. Further development of glass bonded zeolite as a waste form requires an understanding of the interaction between the glass and the zeolite. Properties of the glass that enhance binding and durability of the glass bonded zeolite need to be identified. Three types of glass, boroaluminosilicate, soda-lime silicate, and high silica glasses, have a range of properties and are now being investigated. Each glass was hot pressed by itself and with an equal amount of zeolite. MCC-1 leach tests were run on both. Soda-lime silicate and high silica glasses did not give a durable glass bonded zeolite. Boroaluminosilicate glasses rich in alkaline earths did bind the zeolite and gave a durable glass bonded zeolite. Scanning electron micrographs suggest that the boroaluminosilicate glasses wetted the zeolite powders better than the other glasses. Development of the glass bonded zeolite as a waste form for chloride waste salt is continuing.

  13. Synthesis of hierarchical micro/mesoporous structures via solid-aqueous interface growth: zeolitic imidazolate framework-8 on siliceous mesocellular foams for enhanced pervaporation of water/ethanol mixtures.

    PubMed

    Sue, Yu-Chain; Wu, Jhe-Wei; Chung, Shao-En; Kang, Chao-Hsiang; Tung, Kuo-Lun; Wu, Kevin C-W; Shieh, Fa-Kuen

    2014-04-01

    A new hierarchical micro/mesoporous composite is synthesized via direct growth of microporous zeolitic imidazolate framework-8 (ZIF-8) on siliceous mesocellular foams (MCF). Depending on different synthetic conditions, ZIF-8 with two different particle sizes, i.e., ZIF-8 microparticles and ZIF-8 nanoparticles, were successfully formed on the external surface of amine-functionalized MCF (denoted as microZIF-8@MCF and nanoZIF-8@MCF, respectively). The synthesized hierarchical micro/mesoporous ZIF-8@MCF structures were characterized with several spectroscopic techniques including X-ray diffraction (XRD), solid-state NMR, and FT-IR and electron microscopic techniques (scanning electron microscope, SEM, and transmission electron microscopy, TEM). In addition, the pervaporation measurements of the liquid water/ethanol mixture show that nanoZIF-8@MCF/PVA (poly(vinyl alcohol) mixed-matrix membrane exhibits enhanced performance both on the permeability and separation factor. Compared to conventional routes for chemical etching, this study demonstrates a promising and simple strategy for synthesizing novel hierarchical porous composites exhibiting both advantages of mesoporous materials and microporous materials, which is expected to be useful for gas adsorption, separation, and catalysis. PMID:24625412

  14. Sonochemical synthesis of zeolite NaP from clinoptilolite.

    PubMed

    Behin, Jamshid; Kazemian, Hossein; Rohani, Sohrab

    2016-01-01

    In the present work, natural clinoptilolite was converted to zeolite NaP using ultrasonic energy, in which the transformation time shortened remarkably. The effect of post-synthesis treatment using conventional hydrothermal was also investigated. The synthesized powders were characterized by XRD, TGA/DTA, SEM, and PSD analysis. The results showed that, increasing the sonication time (energy) has no significant effect on the product's morphology. The crystallinity of the synthesized samples increased slightly with increasing sonication time, but their yield remained relatively unchanged. Furthermore, post-synthesis hydrothermal treatment showed very little influence on properties of the final product. Because the ultrasonic irradiation creates acoustic cavitation cracks on the surface structure of clinoptilolite particulates and increases the concentration of soluble alumino-silicate species, which favors the prevailing super-saturation, crystallization and crystal growth of zeolite NaP happen faster. The particles of zeolite NaP synthesized by ultrasonic irradiation consist of small crystallites of uniform size. PMID:26341462

  15. Design of Microporous Material HUS-10 with Tunable Hydrophilicity, Molecular Sieving, and CO2 Adsorption Ability Derived from Interlayer Silylation of Layered Silicate HUS-2.

    PubMed

    Tsunoji, Nao; Yuki, Sota; Oumi, Yasunori; Sekikawa, Miyuki; Sasaki, Yukichi; Sadakane, Masahiro; Sano, Tsuneji

    2015-11-01

    The attractive properties of zeolites, which make them suitable for numerous applications for the energy and chemical industries and for life sciences, are derived from their crystalline framework structures. Herein, we describe the rational synthesis of a microporous material, HUS-10, utilizing a layered silicate precursor, HUS-2, as a structural building unit. For the ordered micropores to be formed, interlayer pillars that supported the original silicate layer of HUS-2 were immobilized through the interlayer silylation of silanol groups with trichloromethylsilane and a subsequent dehydration-condensation reaction of the hydroxyl groups on the preintroduced tetrahedral units. An actual molecular sieving ability, enabling the adsorption of molecules smaller than ethane, was confirmed in the ordered micropores of HUS-10. The hydrophilic adsorption could also be controlled by changing the number of methyl and hydroxyl groups in the immobilized interlayer pillars. In addition, when the adsorption behaviors of CO2, CH4, and N2 on HUS-10 were compared to those on siliceous MFI and CDO zeolites with approximately the same pore diameter, the CO2 adsorption capacity of HUS-10 was comparable. Conversely, because of the adsorption inhibition of CH4 and N2, HUS-10 exhibited larger CO2/CH4 and CO2/N2 adsorption ratios relative to those of MFI and CDO zeolites. These results reveal that the unique microporous framework structure presented by the rational structural design using the layered silicate precursor HUS-2 has the potential to separate CO2 from gas mixtures. PMID:26479449

  16. Vapor Phase Transport Synthesis of Zeolites from Sol-Gel Precursors

    SciTech Connect

    THOMA,STEVEN G.; NENOFF,TINA M.

    2000-07-14

    A study of zeolite crystallization from sol-gel precursors using the vapor phase transport synthesis method has been performed. Zeolites (ZSM-5, ZSM-48, Zeolite P, and Sodalite) were crystallized by contacting vapor phase organic or organic-water mixtures with dried sodium silicate and dried sodium alumino-silicate gels. For each precursor gel, a ternary phase system of vapor phase organic reactant molecules was explored. The vapor phase reactant mixtures ranged from pure ethylene diamene, triethylamine, or water, to an equimolar mixture of each. In addition, a series of gels with varied physical and chemical properties were crystallized using the same vapor phase solvent mixture for each gel. The precursor gels and the crystalline products were analyzed via Scanning Electron Microscopy, Electron Dispersive Spectroscopy, X-ray mapping, X-ray powder diffraction, nitrogen surface area, Fourier Transform Infrared Spectroscopy, and thermal analyses. The product phase and purity as a function of the solvent mixture, precursor gel structure, and precursor gel chemistry is discussed.

  17. Ionic Liquid assisted Synthesis of Zeolite-TON

    PubMed Central

    Tian, Yuyang; McPherson, Matthew J; Wheatley, Paul S; Morris, Russell E

    2014-01-01

    An ionic liquid assisted strategy for the synthesis of zeolitic material is reported. This strategy is a solid state synthetic method and the ionic liquid is employed as structure directing agent. A TON-type zeolite, which contains one-dimensional 10-member-ring, is successfully synthesized with the assistance of the ionic liquid, 1-ethyl-3-methylimidazolium bromide. This finding improves our understanding about the challenge of ionothermally synthesizing siliceous and aluminosilicate zeolites. PMID:26213423

  18. Mesostructured zeolites: bridging the gap between zeolites and MCM-41.

    PubMed

    Prasomsri, Teerawit; Jiao, Wenqian; Weng, Steve Z; Garcia Martinez, Javier

    2015-05-28

    Surfactant-templating is one of the most versatile and useful techniques to implement mesoporous systems into solid materials. Various strategies based on various interactions between surfactants and solid precursors have been explored to produce new structures. Zeolites are invaluable as size- and shape-selective solid acid catalysts. Nevertheless, their micropores impose limitations on the mass transport of bulky feed and/or product molecules. Many studies have attempted to address this by utilizing surfactant-assisting technology to alleviate the diffusion constraints. However, most efforts have failed due to micro/mesopore phase separation. Recently, a new technique combining the uses of cationic surfactants and mild basic solutions was introduced to synthesise mesostructured zeolites. These materials sustain the unique characteristics of zeolites (i.e., strong acidity, crystallinity, microporosity, and hydrothermal stability), including tunable mesopore sizes and degrees of mesoporosity. The mesostructured zeolites are now commercially available through Rive Technology, and show superior performance in VGO cracking. This feature article provides an overview of recent explorations in the introduction of mesoporosity into zeolites using surfactant-templating techniques. Various porous materials, preparation methods, physical and catalytic properties of mesostructured zeolites will be discussed. PMID:25866848

  19. Growth of zeolite crystals in the microgravity environment of space

    NASA Technical Reports Server (NTRS)

    Sacco, A., Jr.; Sand, L. B.; Collette, D.; Dieselman, K.; Crowley, J.; Feitelberg, A.

    1986-01-01

    Zeolites are hydrated, crystalline aluminosilicates with alkali and alkaling earth metals substituted into cation vacancies. Typically zeolite crystals are 3 to 8 microns. Larger cyrstals are desirable. Large zeolite crystals were produced (100 to 200 microns); however, they have taken restrictively long times to grow. It was proposed if the rate of nucleation or in some other way the number of nuclei can be lowered, fewer, larger crystals will be formed. The microgravity environment of space may provide an ideal condition to achieve rapid growth of large zeolite crystals. The objective of the project is to establish if large zeolite crystals can be formed rapidly in space.

  20. Early age hydration and pozzolanic reaction in natural zeolite blended cements: Reaction kinetics and products by in situ synchrotron X-ray powder diffraction

    SciTech Connect

    Snellings, R.; Mertens, G.; Cizer, O.; Elsen, J.

    2010-12-15

    The in situ early-age hydration and pozzolanic reaction in cements blended with natural zeolites were investigated by time-resolved synchrotron X-ray powder diffraction with Rietveld quantitative phase analysis. Chabazite and Na-, K-, and Ca-exchanged clinoptilolite materials were mixed with Portland cement in a 3:7 weight ratio and hydrated in situ at 40 {sup o}C. The evolution of phase contents showed that the addition of natural zeolites accelerates the onset of C{sub 3}S hydration and precipitation of CH and AFt. Kinetic analysis of the consumption of C{sub 3}S indicates that the enveloping C-S-H layer is thinner and/or less dense in the presence of alkali-exchanged clinoptilolite pozzolans. The zeolite pozzolanic activity is interpreted to depend on the zeolite exchangeable cation content and on the crystallinity. The addition of natural zeolites alters the structural evolution of the C-S-H product. Longer silicate chains and a lower C/S ratio are deduced from the evolution of the C-S-H b-cell parameter.

  1. Reclaiming silver from silver zeolite

    SciTech Connect

    Reimann, G.A.

    1991-10-01

    Silver zeolite is used to capture radioiodines from air cleaning systems in some nuclear facilities at the Idaho National Engineering Laboratory. It may become radioactively contaminated and/or poisoned by hydrocarbon vapors, which diminishes its capacity for iodine. Silver zeolite contains up to 38 wt% silver. A pyrometallurgical process was developed to reclaim the silver before disposing of the unserviceable zeolite as a radioactive waste. A flux was formulated to convert the refractory aluminosilicate zeolite structure into a low-melting fluid slag, with Na{sub 2}O added as NAOH instead of Na{sub 2}CO{sub 3} to avoid severe foaming due to CO{sub 2} evolution. A propane-fired furnace was built to smelt 45 kg charges at 1300C in a carbon-bonded silicon carbide crucible. A total of 218 kg (7000 tr oz) of silver was reclaimed from 1050 kg of unserviceable zeolite. Silver recoveries of 97% were achieved, and the radioisotopes were fixed as stable silicates in a vitreous slag that was disposed of as a low level waste. Recovered silver was refined using oxygen and cast into 100 tr oz bars assaying 99.8+% silver and showing no radioactive contamination.

  2. Reclaiming silver from silver zeolite

    SciTech Connect

    Reimann, G.A.

    1991-10-01

    Silver zeolite is used to capture radioiodines from air cleaning systems in some nuclear facilities at the Idaho National Engineering Laboratory. It may become radioactively contaminated and/or poisoned by hydrocarbon vapors, which diminishes its capacity for iodine. Silver zeolite contains up to 38 wt% silver. A pyrometallurgical process was developed to reclaim the silver before disposing of the unserviceable zeolite as a radioactive waste. A flux was formulated to convert the refractory aluminosilicate zeolite structure into a low-melting fluid slag, with Na[sub 2]O added as NAOH instead of Na[sub 2]CO[sub 3] to avoid severe foaming due to CO[sub 2] evolution. A propane-fired furnace was built to smelt 45 kg charges at 1300C in a carbon-bonded silicon carbide crucible. A total of 218 kg (7000 tr oz) of silver was reclaimed from 1050 kg of unserviceable zeolite. Silver recoveries of 97% were achieved, and the radioisotopes were fixed as stable silicates in a vitreous slag that was disposed of as a low level waste. Recovered silver was refined using oxygen and cast into 100 tr oz bars assaying 99.8+% silver and showing no radioactive contamination.

  3. Zeolite-like liquid crystals

    NASA Astrophysics Data System (ADS)

    Poppe, Silvio; Lehmann, Anne; Scholte, Alexander; Prehm, Marko; Zeng, Xiangbing; Ungar, Goran; Tschierske, Carsten

    2015-10-01

    Zeolites represent inorganic solid-state materials with porous structures of fascinating complexity. Recently, significant progress was made by reticular synthesis of related organic solid-state materials, such as metal-organic or covalent organic frameworks. Herein we go a step further and report the first example of a fluid honeycomb mimicking a zeolitic framework. In this unique self-assembled liquid crystalline structure, transverse-lying ?-conjugated rod-like molecules form pentagonal channels, encircling larger octagonal channels, a structural motif also found in some zeolites. Additional bundles of coaxial molecules penetrate the centres of the larger channels, unreachable by chains attached to the honeycomb framework. This creates a unique fluid hybrid structure combining positive and negative anisotropies, providing the potential for tuning the directionality of anisotropic optical, electrical and magnetic properties. This work also demonstrates a new approach to complex soft-matter self-assembly, by using frustration between space filling and the entropic penalty of chain extension.

  4. Preparation and characterization of zeolitic membrane

    SciTech Connect

    Shuanshi Fan; Chunhua Li; Jinqu Wang

    1994-12-31

    Zeolites with less than 10 {angstrom} pores are desirable membrane materials, due to their crystallinity, resistance to high temperature, and chemical inertness. Although several works have been done on them, zeolitic membranes have not been developed so perfect at present. In this paper, the authors reported the preparation and some properties of an asymmetric zeolitic membrane synthesized by hydrothermal process on the intermediate layer which was made on a porous ceramic support, meanwhile the results of separation of ethanol-water mixture on pervaporation were discussed.

  5. Properties of Zeolite A Obtained from Powdered Laundry Detergent: An Undergraduate Chemistry Experiment

    NASA Astrophysics Data System (ADS)

    Lindquist, David A.; Smoot, Alison L.

    1997-05-01

    Zeolites, crystalline porous aluminosilicates, are valued for their ability to absorb ions and molecules as well as function as catalysts. A number of laboratory experiments using zeolites filtered from a suspension of powdered laundry detergent are described. The various experiments illustrate the myriad uses of zeolites as desiccants, ion exchange materials, and catalysts.

  6. Understanding silicate hydration from quantitative analyses of hydrating tricalcium silicates.

    PubMed

    Pustovgar, Elizaveta; Sangodkar, Rahul P; Andreev, Andrey S; Palacios, Marta; Chmelka, Bradley F; Flatt, Robert J; d'Espinose de Lacaillerie, Jean-Baptiste

    2016-01-01

    Silicate hydration is prevalent in natural and technological processes, such as, mineral weathering, glass alteration, zeolite syntheses and cement hydration. Tricalcium silicate (Ca3SiO5), the main constituent of Portland cement, is amongst the most reactive silicates in water. Despite its widespread industrial use, the reaction of Ca3SiO5 with water to form calcium-silicate-hydrates (C-S-H) still hosts many open questions. Here, we show that solid-state nuclear magnetic resonance measurements of (29)Si-enriched triclinic Ca3SiO5 enable the quantitative monitoring of the hydration process in terms of transient local molecular composition, extent of silicate hydration and polymerization. This provides insights on the relative influence of surface hydroxylation and hydrate precipitation on the hydration rate. When the rate drops, the amount of hydroxylated Ca3SiO5 decreases, thus demonstrating the partial passivation of the surface during the deceleration stage. Moreover, the relative quantities of monomers, dimers, pentamers and octamers in the C-S-H structure are measured. PMID:27009966

  7. Characteristic of fly ash derived-zeolite and its catalytic performance for fast pyrolysis of Jatropha waste.

    PubMed

    Vichaphund, S; Aht-Ong, D; Sricharoenchaikul, V; Atong, D

    2014-01-01

    Fly ash from pulp and paper industries was used as a raw material for synthesizing zeolite catalyst. Main compositions of fly ash consisted of 41 wt%SiO2, 20 wt%Al2O3, 14 wt%CaO, and 8 wt% Fe2O3. High content of silica and alumina indicated that this fly ash has potential uses for zeolite synthesis. Fly ash was mixed with 1-3 M NaOH solution. Sodium silicate acting as silica source was added into the solution to obtain the initial SiO2/Al2O3 molar ratio of 23.9. The mixtures were then crystallized at 160 degrees C for 24 and 72 h. Zeolites synthesized after a long synthesis time of 72 h showed superior properties in terms of high crystallinity, less impurity, and small particle size. The catalytic activities of fly ash-derived zeolites were investigated via fast pyrolysis of Jatropha wastes using analytical pyrolysis-gas chromatograph/mass spectrometer (GC/MS). Pyrolysis temperature was set at 500 degrees C with Jatropha wastes to catalyst ratio of 1:1, 1:5, and 1:10. Results showed that higher amounts of catalyst have a positive effect on enhancing aromatic hydrocarbons as well as decreasing in the oxygenated and N-containing compounds. Zeolite Socony Mobil-5 (ZSM-5) treated with 3 M NaOH at 72 h showed the highest hydrocarbon yield of 97.4%. The formation of hydrocarbon led to the high heating value of bio-oils. In addition, the presence of ZSM-5 derived from fly ash contributed to reduce the undesirable oxygenated compounds such as aldehydes, acids, and ketones which cause poor quality of bio-oil to only 0.8% while suppressed N-compounds to 1.7%. Overall, the ZSM-5 synthesized from fly ash proved to be an effective catalyst for catalytic fast pyrolysis application. PMID:25145178

  8. Selectivity of zeolite catalysts of hydrocracking of paraffin hydrocarbons

    SciTech Connect

    Shakun, A.N.; Il'icheva, L.F.; Nikitina, N.L.; Nefedov, B.K.; Konoval'chikov, L.D.; Alekseeva, T.V.

    1988-09-20

    The selectivity of catalysts of hydrocracking based on three types of zeolites: HKE, HM, and HTsVM was studied in comparable conditions and it was found that in rigorous conditions of conducting the process (longer contact time, deeper conversion of the normal paraffin), the contribution of nonselective hydrocracking which takes place on the external crystalline surface of the zeolites becomes marked on all of the catalysts. Incorporation of a hydrogenating component in the zeolite-containing catalyst results in an increase in nonselective hydrocracking on the external crystalline surface of the zeolites, and addition of significant amounts of molybdenum oxide also results in a decrease in the total conversion of the n-paraffin. The contribution of nonselective hydrocracking decreases with an increase in the intracrystalline activity of the zeolite.

  9. Thermodynamic modeling of natural zeolite stability

    SciTech Connect

    Chipera, S.J.; Bish, D.L.

    1997-06-01

    Zeolites occur in a variety of geologic environments and are used in numerous agricultural, commercial, and environmental applications. It is desirable to understand their stability both to predict future stability and to evaluate the geochemical conditions resulting in their formation. The use of estimated thermodynamic data for measured zeolite compositions allows thermodynamic modeling of stability relationships among zeolites in different geologic environments (diagenetic, saline and alkaline lakes, acid rock hydrothermal, basic rock, deep sea sediments). This modeling shows that the relative cation abundances in both the aqueous and solid phases, the aqueous silica activity, and temperature are important factors in determining the stable zeolite species. Siliceous zeolites (e.g., clinoptilolite, mordenite, erionite) present in saline and alkaline lakes or diagenetic deposits formed at elevated silica activities. Aluminous zeolites (e.g., natrolite, mesolite/scolecite, thomsonite) formed in basic rocks in association with reduced silica activities. Likewise, phillipsite formation is favored by reduced aqueous silica activities. The presence of erionite, chabazite, and phillipsite are indicative of environments with elevated potassium concentrations. Elevated temperature, calcic water conditions, and reduced silica activity help to enhance the laumontite and wairakite stability fields. Analcime stability increases with increased temperature and aqueous Na concentration, and/or with decreased silica activity.

  10. Conversion of rice husk ash to zeolite beta.

    PubMed

    Prasetyoko, Didik; Ramli, Zainab; Endud, Salasiah; Hamdan, Halimaton; Sulikowski, Bogdan

    2006-01-01

    White rice husk ash (RHA), an agriculture waste containing crystalline tridymite and alpha-cristobalite, was used as a silica source for zeolite Beta synthesis. The crystallization of zeolite Beta from RHA at 150 degrees C in the presence of tetraethylammonium hydroxide was monitored by XRD, FTIR and (29)Si MAS NMR techniques. It was found that zeolite Beta started to form after 12h and the complete crystallization of zeolite Beta phase was achieved after 2d. XRD, (29)Si MAS NMR and solid yield studies indicate that the transformation mechanism of silica present in RHA to zeolite Beta involves dissolution of the ash, formation of an amorphous aluminosilicate after 6h of crystallization, followed by dissolution in the mother liquor and final transformation to pure zeolite Beta crystals. PMID:16274981

  11. Synthesis and catalytic applications of combined zeolitic/mesoporous materials

    PubMed Central

    Vernimmen, Jarian; Cool, Pegie

    2011-01-01

    Summary In the last decade, research concerning nanoporous siliceous materials has been focused on mesoporous materials with intrinsic zeolitic features. These materials are thought to be superior, because they are able to combine (i) the enhanced diffusion and accessibility for larger molecules and viscous fluids typical of mesoporous materials with (ii) the remarkable stability, catalytic activity and selectivity of zeolites. This review gives an overview of the state of the art concerning combined zeolitic/mesoporous materials. Focus is put on the synthesis and the applications of the combined zeolitic/mesoporous materials. The different synthesis approaches and formation mechanisms leading to these materials are comprehensively discussed and compared. Moreover, Ti-containing nanoporous materials as redox catalysts are discussed to illustrate a potential implementation of combined zeolitic/mesoporous materials. PMID:22259762

  12. Health implications of natural fibrous zeolites for the Intermountain west

    SciTech Connect

    Rom, W.N.; Casey, K.R.; Parry, W.T.; Mjaatvedt, C.H.; Moatamed, F.

    1983-02-01

    Fibrous zeolites have recently been implicated in an endemic outbreak of malignant pleural mesothelioma in several villages in Cappadocia in central Turkey. The possible association between fibrous zeolites and mesothelioma and the potential biological activity of fibrous erionite from the United States are reviewed. The zeolite minerals comprise a group of over forty hydrated aluminum silicates. More than 300 probable deposits of various natural zeolites are located in 25 states in the United States. Reserves of perhaps 10 trillion tons are present in the western United States; about 120 million tons are deposited near the surface. Several zeolites, including erionite and mordenite, may occur with a fibrous habit. Fibrous erionite is found in several well-defined deposits in Arizona, Nevada, Oregon, and Utah, where it occurs as thin, pure beds within sedimentary tuff sequences, or as outcrops in desert valleys of the Intermountain region. (JMT)

  13. Physical, chemical and catalytic properties of high modules Y zeolite obtained by direct synthesis compared with ultrastable Y zeolite

    SciTech Connect

    Levinbuk, M.I.; Melnikov, V.B.; Pavlov, M.L.

    1996-10-01

    Industrial preparation of Y zeolites is widely spread throughout the world. However, unlike the zeolites of pentasil (ZSM) series, their catalytic activity and selectivity are controlled by molar SiO{sub 2}; Al{sub 2}O{sub 3} ratio, which is varied by the method of post synthesis modification and not by direct synthesis. Zeolites obtain in such a way (hydrothermal - USY or chemical treatments-LZ-210) with the modulus above 5.5 are called ultrastable. Defects of ultrastable zeolites are: partial distortions of the crystalline framework, appearance of the aluminum in the sample beyond the framework, and the higher cost of zeolite product at expense of construction and operating charges. These additional expenses are due to the necessity of special blocks for modification of NaY zeolite with modulus 4.5-5.0 synthesized by traditional methods.

  14. Effects of ultrasonic treatment on zeolite NaA synthesized from by-product silica.

    PubMed

    Vai?iukynien?, Danut?; Kantautas, Aras; Vaitkevi?ius, Vitoldas; Jakevi?ius, Leonas; Rudionis, ymantas; Pakevi?ius, Mantas

    2015-11-01

    The synthesis of zeolite NaA from silica by-product was carried out in the presence of 20 kHz ultrasound at room temperature. Zeolites obtained in this type of synthesis were compared to zeolites obtained by performing conventional static syntheses under similar conditions. The sonication effects on zeolite NaA synthesis were characterized by phase identification, crystallinity etc. The effects of different parameters such as crystallization time and initial materials preparation methods on the crystallinity and morphology of the synthesized zeolites were investigated. The final products were characterized by XRD and FT-IR. It was possible to obtain crystalline zeolite NaA from by-product silica in the presence of ultrasound. PMID:26186874

  15. Factors that Determine Zeolite Stability in Hot Liquid Water.

    PubMed

    Zhang, Lu; Chen, Kuizhi; Chen, Banghao; White, Jeffery L; Resasco, Daniel E

    2015-09-16

    The susceptibility of zeolites to hot liquid water may hamper their full utilization in aqueous phase processes, such as those involved in biomass conversion and upgrading reactions. Interactions of zeolites with water strongly depend on the presence of hydrophilic moieties including Brnsted acid sites (BAS), extraframework cations, and silanol defects, which facilitate wetting of the surface. However, it is not clear which of these moieties are responsible for the susceptibility of zeolites to liquid water. Previous studies have offered contradictory explanations because the role of each of these characteristics has not been investigated independently. In this work, a systematic comparison has been attempted by relating crystallinity losses to the variation of each of the five zeolite characteristics that may influence their stability in liquid water, including number of BAS, Si-O-Si bonds, framework type, silanol defects, and extraframework Al. In this study, we have systematically monitored the crystallinity changes of a series of HY, H-ZSM-5, and H-? zeolite samples with varying Si/Al ratio, density of BAS, zeolite structure, and density of silanol defects upon exposure to liquid water at 200 C. The results of this comparison unambiguously indicate that the density of silanol defects plays the most crucial role in determining susceptibility of zeolites to hot liquid water. By functionalizing the silanol defects with organosilanes, the hydrophobicity of defective zeolite is increased and the tolerance to hot liquid water is significantly enhanced. PMID:26301890

  16. Microwave heating in the hydrogen peroxide oxidation of benzene on zeolite catalysts

    PubMed

    Radoiu; Calinescu; Chipurici; Martin

    2000-01-01

    In this paper benzene hydroxylation with hydrogen peroxide (H2O2) in the presence of the titan-silicates-zeolites was studied. The initial catalyst, HZSM-5 zeolite type was treated to obtain both cobalt- and titan-silicates--zeolite. These improved catalysts were also used for oxidation. To obtain reaction temperature heating was made by conventional techniques and by microwave treatment. From this research it was concluded that reaction temperature is a very important parameter to keep a proper equilibrium between the decomposition rate of hydrogen peroxide and the oxidation rate of aromatic compound. It was also found that microwaves affect the reaction selectivity. PMID:10935194

  17. Novel long-term immobilization method for radioactive iodine-129 using a zeolite/apatite composite sintered body.

    PubMed

    Watanabe, Yujiro; Ikoma, Toshiyuki; Yamada, Hirohisa; Suetsugu, Yasushi; Komatsu, Yu; Stevens, Geoffrey W; Moriyoshi, Yusuke; Tanaka, Junzo

    2009-07-01

    The amount of radioactive iodine generated from nuclear power plants is expected to increase with the proliferation of nuclear energy production, and long-term immobilization methods for such radioactive elements need to be developed to make nuclear energy sustainable. The standard immobilization method of radioactive elements, vitrification, is not very effective for radioactive iodine-129 because of the low solubility of iodine in silicate melts, its very high volatility at standard vitrification process temperatures, and its instability in the alkaline environment of deep geological layers below 300 m. We have developed a novel three-phase ceramic composite produced by a sintering process. Iodine adsorbed onto Ca-type zeolite A was covered with a hydroxyapatite nanolayer through the exchange reaction of ammonium with calcium. Clusters of iodine of 30 nm within the zeolite structure were found to be thermally stable up to 1253 K because of the partial blockage of the alpha-cage apertures by ammonium ions and the partial change from a crystalline phase to an amorphous phase at 473 K. No gasification of iodine molecules was found to occur during the sintering process. The outer phase was highly crystalline hydroxyfluorapatite in which the hydroxyapatite nanolayer plays an important role for successful sintering. The elution of iodine in low-dioxygen water, similar to that found within the Earth's crust, was investigated and was found to occur only in the surface layer of the sintered body. PMID:20355964

  18. Zeolite coatings on metal alloys for corrosion resistance, hydrophilicity, and microbiocidal activity

    NASA Astrophysics Data System (ADS)

    Beving, Derek Eugene

    The recent advent of polycrystalline zeolite coatings on metal alloys has heralded a paradigm shift in zeolitic application and function as well as their requisite synthesis. The prevailing paradigm for zeolite utilization and employment was through the exploitation of their uniform microporosity. We have demonstrated the utility of the non-porous as-synthesized form of high-silica-zeolite (HSZ) MFI coatings on aluminum alloys for corrosion resistance. A single chemical formulation was able to generate excellent corrosion-resistant HSZ MFI coatings on all aluminum alloys studied. Functional zeolite coatings have traditionally been synthesized as coatings comprised of single zeolite species. We have successfully generated functional zeolite hybrid coatings comprised of disparate zeolite species with controlled composition. A three-layer zeolite coating was developed to apply a low-silica-zeolite (LSZ), zeolite Y (ZY), to aluminum substrates. The middle layer was a zeolite hybrid coating of ZY crystals embedded within a MFI matrix. The mixed zeolite middle layer allowed for the adhesion of the single species HSZ MFI bottom layer to the single species LSZ ZY, top layer. A two-layer hydrophilic and antimicrobial hybrid zeolite coating on aluminum alloys was also developed. The base layer was a HSZ MFI coating and the top layer consisted of zeolite A (ZA) crystals embedded within a matrix of HSZ MFI. The ZA crystals are still present at the surface of the hybrid layer, as such; their hydrophilicity is accessible and can be exploited for their hydrophilic and antimicrobial potential. The great utility of the zeolite hybrid layer is realized with the formation of single-layer hybrid coatings on metal alloys. The hybrid coating is made of mixed inorganic crystalline species imbedded in a matrix of HSZ MFI. The inorganic species used is not limited to zeolite types; other inorganic crystalline species can be used. We have generated hybrid coatings made from LSZ ZY and HSZ MR, and hybrid coatings made from hydrotalcite, an inorganic crystalline species distinctly different from zeolite, and HSZ MFI. The single layer hybrid coatings have great utility and their function and application can be easily tuned by changing the zeolite or crystalline inorganic species used to generate them.

  19. ZEOLITES: EFFECTIVE WATER PURIFIERS

    EPA Science Inventory

    Zeolites are known for their adsorption, ion exchange and catalytic properties. Various natural zeolites are used as odor and moisture adsorbents and water softeners. Due to their acidic nature, synthetic zeolites are commonly employed as solid acid catalysts in petrochemical ind...

  20. Zeolite-like liquid crystals.

    PubMed

    Poppe, Silvio; Lehmann, Anne; Scholte, Alexander; Prehm, Marko; Zeng, Xiangbing; Ungar, Goran; Tschierske, Carsten

    2015-01-01

    Zeolites represent inorganic solid-state materials with porous structures of fascinating complexity. Recently, significant progress was made by reticular synthesis of related organic solid-state materials, such as metal-organic or covalent organic frameworks. Herein we go a step further and report the first example of a fluid honeycomb mimicking a zeolitic framework. In this unique self-assembled liquid crystalline structure, transverse-lying ?-conjugated rod-like molecules form pentagonal channels, encircling larger octagonal channels, a structural motif also found in some zeolites. Additional bundles of coaxial molecules penetrate the centres of the larger channels, unreachable by chains attached to the honeycomb framework. This creates a unique fluid hybrid structure combining positive and negative anisotropies, providing the potential for tuning the directionality of anisotropic optical, electrical and magnetic properties. This work also demonstrates a new approach to complex soft-matter self-assembly, by using frustration between space filling and the entropic penalty of chain extension. PMID:26486751

  1. Zeolite-like liquid crystals

    PubMed Central

    Poppe, Silvio; Lehmann, Anne; Scholte, Alexander; Prehm, Marko; Zeng, Xiangbing; Ungar, Goran; Tschierske, Carsten

    2015-01-01

    Zeolites represent inorganic solid-state materials with porous structures of fascinating complexity. Recently, significant progress was made by reticular synthesis of related organic solid-state materials, such as metal-organic or covalent organic frameworks. Herein we go a step further and report the first example of a fluid honeycomb mimicking a zeolitic framework. In this unique self-assembled liquid crystalline structure, transverse-lying π-conjugated rod-like molecules form pentagonal channels, encircling larger octagonal channels, a structural motif also found in some zeolites. Additional bundles of coaxial molecules penetrate the centres of the larger channels, unreachable by chains attached to the honeycomb framework. This creates a unique fluid hybrid structure combining positive and negative anisotropies, providing the potential for tuning the directionality of anisotropic optical, electrical and magnetic properties. This work also demonstrates a new approach to complex soft-matter self-assembly, by using frustration between space filling and the entropic penalty of chain extension. PMID:26486751

  2. Improved Catalysts for Heavy Oil Upgrading Based on Zeolite Y Nanoparticles Encapsulated Stable Nanoporous Host

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2007-09-30

    The objective of this project is to synthesize nanocrystals of highly acidic zeolite Y nanoclusters, encapsulate them within the channels of mesoporous (nanoporous) silicates or nanoporous organosilicates, and evaluate the 'zeolite Y/Nanoporous host' composites as catalysts for the upgrading of heavy petroleum feedstocks. In comparison to conventionally-used zeolite Y catalysts of micron size particles, the nanocrystals (< 100 nm particle size) which contain shorter path lengths, are expected to allow faster diffusion of large hydrocarbon substrates and the catalysis products within and out of the zeolite's channels and cages (<1 nm size). This is expected to significantly reduce deactivation of the catalyst and to prolong their period of reactivity. Encapsulating zeolite Y nanocrystals within the nanoporous materials is expected to protect its external surfaces and pore entrances from being blocked by large hydrocarbon substrates, since these substrates will initially be converted to small molecules by the nanoporous host (a catalyst in its own right). The project consisted of four major tasks as follows: (1) synthesis of the nanoparticles of zeolite Y (of various chemical compositions) using various techniques such as the addition of organic additives to conventional zeolite Y synthesis mixtures to suppress zeolite Y crystal growth; (2) synthesis of nanoporous silicate host materials of up to 30 nm pore diameter, using poly (alkylene oxide) copolymers which when removed will yield a mesoporous material; (3) synthesis of zeolite Y/Nanoporous Host composite materials as potential catalysts; and (4) evaluation of the catalyst for the upgrading of heavy petroleum feedstocks.

  3. Zeolite catalysis: technology

    SciTech Connect

    Heinemann, H.

    1980-07-01

    Zeolites have been used as catalysts in industry since the early nineteen sixties. The great majority of commercial applications employ one of three zeolite types: zeolite Y; Mordenite; ZSM-5. By far the largest use of zeolites is in catalytic cracking, and to a lesser extent in hydrocracking. This paper reviews the rapid development of zeolite catalysis and its application in industries such as: the production of gasoline by catalytic cracking of petroleum; isomerization of C/sub 5/ and C/sub 6/ paraffin hydrocarbons; alkylation of aromatics with olefins; xylene isomerization; and conversion of methanol to gasoline.

  4. Silanization-Based Zeolite Crystallization: Participation Degree and Pathway.

    PubMed

    Yan, Yueer; Azhati, Arepati; Guo, Xiao; Zhang, Yahong; Tang, Yi

    2015-08-17

    A clear and deep understanding of zeolite crystallization with the addition of organosilane is desirable for the reasonable design and preparation of hierarchical zeolites. Herein, the effects of different organosilanes on zeolite crystallization were systematically studied. It was found that organosilane plays the role of an inhibitor in the silanization-based zeolite preparation, and this inhibition effect was determined by its participation degree. An organosilane with a high participation degree can result in the prolongation of nucleation and growth periods of zeolite as well as the variation of product properties. More importantly, a dynamic participation pathway of organosilane is proposed, that is, the growth of zeolite is accompanied by the continuous removal of organosilane, leading to an increase of product crystallinity as well as the decrease of mesoporosity. This study gives a new insight into the role that organosilane plays in zeolite crystallization, which will help to direct the rational selection of organosilane and design of crystallization condition for the optimal synthesis of hierarchical zeolites. PMID:26173899

  5. Effect of silicate modulus and metakaolin incorporation on the carbonation of alkali silicate-activated slags

    SciTech Connect

    Bernal, Susan A.; Mejia de Gutierrez, Ruby; Provis, John L.; Rose, Volker

    2010-06-15

    Accelerated carbonation is induced in pastes and mortars produced from alkali silicate-activated granulated blast furnace slag (GBFS)-metakaolin (MK) blends, by exposure to CO{sub 2}-rich gas atmospheres. Uncarbonated specimens show compressive strengths of up to 63 MPa after 28 days of curing when GBFS is used as the sole binder, and this decreases by 40-50% upon complete carbonation. The final strength of carbonated samples is largely independent of the extent of metakaolin incorporation up to 20%. Increasing the metakaolin content of the binder leads to a reduction in mechanical strength, more rapid carbonation, and an increase in capillary sorptivity. A higher susceptibility to carbonation is identified when activation is carried out with a lower solution modulus (SiO{sub 2}/Na{sub 2}O ratio) in metakaolin-free samples, but this trend is reversed when metakaolin is added due to the formation of secondary aluminosilicate phases. High-energy synchrotron X-ray diffractometry of uncarbonated paste samples shows that the main reaction products in alkali-activated GBFS/MK blends are C-S-H gels, and aluminosilicates with a zeolitic (gismondine) structure. The main crystalline carbonation products are calcite in all samples and trona only in samples containing no metakaolin, with carbonation taking place in the C-S-H gels of all samples, and involving the free Na{sup +} present in the pore solution of the metakaolin-free samples. Samples containing metakaolin do not appear to have the same availability of Na{sup +} for carbonation, indicating that this is more effectively bound in the presence of a secondary aluminosilicate gel phase. It is clear that claims of exceptional carbonation resistance in alkali-activated binders are not universally true, but by developing a fuller mechanistic understanding of this process, it will certainly be possible to improve performance in this area.

  6. The recyclable synthesis of hierarchical zeolite SAPO-34 with excellent MTO catalytic performance.

    PubMed

    Xi, Dongyang; Sun, Qiming; Chen, Xiaoxin; Wang, Ning; Yu, Jihong

    2015-08-01

    A facile and green route has been developed for the synthesis of hierarchical zeolite catalysts by recycling of waste mother-liquors. After three recycles of mother-liquors, the obtained hierarchical SAPO-34 zeolites retain high crystallinity, texture properties, and acidity, as well as excellent MTO catalytic performance as compared to the initially prepared catalysts. PMID:26121259

  7. Hydrocarbon zeolite catalyst employed in hydrocracking process

    SciTech Connect

    Ward, J.W.

    1987-05-12

    A hydrocracking process is described which comprises contacting a hydrocarbon feedstock under hydrocracking conditions with hydrogen in the presence of a catalyst comprising at least one hydrogenation component, a crystalline aluminosilicate zeolite having catalytic activity for cracking hydrocarbons, and a dispersion of silica-alumina in a matrix consisting essentially of alumina, wherein the catalyst comprises particles in the shape of a three-leaf clover.

  8. Biological and therapeutic effects of ortho-silicic acid and some ortho-silicic acid-releasing compounds: New perspectives for therapy

    PubMed Central

    2013-01-01

    Silicon (Si) is the most abundant element present in the Earth's crust besides oxygen. However, the exact biological roles of silicon remain unknown. Moreover, the ortho-silicic acid (H4SiO4), as a major form of bioavailable silicon for both humans and animals, has not been given adequate attention so far. Silicon has already been associated with bone mineralization, collagen synthesis, skin, hair and nails health atherosclerosis, Alzheimer disease, immune system enhancement, and with some other disorders or pharmacological effects. Beside the ortho-silicic acid and its stabilized formulations such as choline chloride-stabilized ortho-silicic acid and sodium or potassium silicates (e.g. M2SiO3; M= Na,K), the most important sources that release ortho-silicic acid as a bioavailable form of silicon are: colloidal silicic acid (hydrated silica gel), silica gel (amorphous silicon dioxide), and zeolites. Although all these compounds are characterized by substantial water insolubility, they release small, but significant, equilibrium concentration of ortho-silicic acid (H4SiO4) in contact with water and physiological fluids. Even though certain pharmacological effects of these compounds might be attributed to specific structural characteristics that result in profound adsorption and absorption properties, they all exhibit similar pharmacological profiles readily comparable to ortho-silicic acid effects. The most unusual ortho-silicic acid-releasing agents are certain types of zeolites, a class of aluminosilicates with well described ion(cation)-exchange properties. Numerous biological activities of some types of zeolites documented so far might probably be attributable to the ortho-silicic acid-releasing property. In this review, we therefore discuss biological and potential therapeutic effects of ortho-silicic acid and ortho-silicic acid -releasing silicon compounds as its major natural sources. PMID:23298332

  9. Zeolite thin films: from computer chips to space stations.

    PubMed

    Lew, Christopher M; Cai, Rui; Yan, Yushan

    2010-02-16

    Zeolites are a class of crystalline oxides that have uniform and molecular-sized pores (3-12 A in diameter). Although natural zeolites were first discovered in 1756, significant commercial development did not begin until the 1950s when synthetic zeolites with high purity and controlled chemical composition became available. Since then, major commercial applications of zeolites have been limited to catalysis, adsorption, and ion exchange, all using zeolites in powder form. Although researchers have widely investigated zeolite thin films within the last 15 years, most of these studies were motivated by the potential application of these materials as separation membranes and membrane reactors. In the last decade, we have recognized and demonstrated that zeolite thin films can have new, diverse, and economically significant applications that others had not previously considered. In this Account, we highlight our work on the development of zeolite thin films as low-dielectric constant (low-k) insulators for future generation computer chips, environmentally benign corrosion-resistant coatings for aerospace alloys, and hydrophilic and microbiocidal coatings for gravity-independent water separation in space stations. Although these three applications might not seem directly related, they all rely on the ability to fine-tune important macroscopic properties of zeolites by changing their ratio of silicon to aluminum. For example, pure-silica zeolites (PSZs, Si/Al = infinity) are hydrophobic, acid stable, and have no ion exchange capacity, while low-silica zeolites (LSZs, Si/Al < 2) are hydrophilic, acid soluble, and have a high ion exchange capacity. These new thin films also take advantage of some unique properties of zeolites that have not been exploited before, such as a higher elastic modulus, hardness, and heat conductivity than those of amorphous porous silicas, and microbiocidal capabilities derived from their ion exchange capacities. Finally, we briefly discuss our more recent work on polycrystalline zeolite thin films as promising biocompatible coatings and environmentally benign wear-resistant and antifouling coatings. When zeolites are incorporated into polymer thin films in the form of nanocrystals, we also show that the resultant composite membranes can significantly improve the performance of reverse osmosis membranes for sea water desalination and proton exchange membrane fuel cells. These diverse applications of zeolites have the potential to initiate new industries while revolutionizing existing ones with a potential economic impact that could extend into the hundreds of billions of dollars. We have licensed several of these inventions to companies with millions of dollars invested in their commercial development. We expect that other related technologies will be licensed in the near future. PMID:20158246

  10. Synthesis of 'unfeasible' zeolites.

    PubMed

    Mazur, Michal; Wheatley, Paul S; Navarro, Marta; Roth, Wieslaw J; Poloij, Miroslav; Mayoral, Alvaro; Eliov, Pavla; Nachtigall, Petr; ?ejka, Ji?; Morris, Russell E

    2016-01-01

    Zeolites are porous aluminosilicate materials that have found applications in many different technologies. However, although simulations suggest that there are millions of possible zeolite topologies, only a little over 200 zeolite frameworks of all compositions are currently known, of which about 50 are pure silica materials. This is known as the zeolite conundrum-why have so few of all the possible structures been made? Several criteria have been formulated to explain why most zeolites are unfeasible synthesis targets. Here we demonstrate the synthesis of two such 'unfeasible' zeolites, IPC-9 and IPC-10, through the assembly-disassembly-organization-reassembly mechanism. These new high-silica zeolites have rare characteristics, such as windows that comprise odd-membered rings. Their synthesis opens up the possibility of preparing other zeolites that have not been accessible by traditional solvothermal synthetic methods. We envisage that these findings may lead to a step change in the number and types of zeolites available for future applications. PMID:26673264

  11. Delaminated zeolites: Combining the benefits of zeolites and mesoporous materials for catalytic uses

    SciTech Connect

    Corma, A.; Fornes, V.; Martinez-Triguero, J.; Pergher, S.B.

    1999-08-15

    The delamination of the layered precursor of the MCM-22 zeolite (MWW structure) affords monolayers of a crystalline aluminosilicate with more than 700 m{sup 2}/g of a well defined external surface formed by cups of 0.7 x 0.7 nm. In this layered structure the circular 10-member-ring microporous system is preserved. The resultant material presents the strong acidity and stability characteristic of the zeolites but, at the same time, offers the high accessibility to large molecules characteristic of the amorphous aluminosilicates. The cracking behavior during the process of small and large molecules has been compared with that of the zeolite MCM-22 and pillared laminar precursor MCM-36.

  12. Growth of large zeolite crystals in space

    NASA Technical Reports Server (NTRS)

    Sacco, A., Jr.; Dixon, A.; Thompson, R.; Scott, G.; Ditr, J.

    1988-01-01

    Synthesis studies performed using close analogs of triethanolamine (TEA) have shown that all three hydroxyl groups and the amine group in this molecule are necessary to provide nucleation suppression. Studies using C-13 nuclear magnetic resonance (NMR) revealed that the hydroxyl ions and the amine group are involved in the formation of an aluminum complex. It was also shown that silicate species fo not interact this way with TEA in an alkaline solution. These results suggest that successful aluminum complexation leads to nucleation in zeolite-A crystallization.

  13. Effect of reaction mixture composition and silica source on size distribution of zeolite X crystals

    NASA Astrophysics Data System (ADS)

    Tekin, Rumeysa; Bac, Nurcan; Warzywoda, Juliusz; Sacco, Albert

    2015-02-01

    Zeolite X crystals were synthesized by hydrothermal crystallization from gels with different compositions. The syntheses were performed at 95 C using different silica sources such as sodium metasilicate anhydrous, sodium metasilicate pentahydrate, silicate solution and Cab-O-Sil. Triethanolamine was used in some syntheses in order to grow large crystals. Zeolite X crystals with diameters in the range of 1-220 ?m were obtained, and Cab-O-Sil in concert with triethanolamine yielded the largest crystals.

  14. Zeolite synthesis from fly ash and cement kiln dust

    SciTech Connect

    Grutzeck, M.W.

    1996-12-31

    Zeolites added to portland cement paste normally undergo a pozzolanic reaction. However, if the composition of the cement is modified by blending it with fly ash, the calcium silicate hydrate (C-S-H) that forms has a low CaO/SiO{sub 2} ratio which allows it to coexist with a zeolite. In fact, if one adds alkali to the system, it then becomes possible to nucleate and grow a zeolitic phase with C-S-H. Normally zeolites that form from fly ash and NaOH include NaP-1 and analcime. But when the fly ash and NaOH are mixed with cement kiln dust, cancrinite-like phases and tobermorite form instead. This implies that a zeolite-containing monolith could be produced that would exhibit both the cation-exchange and adsorptive properties of zeolites while retaining the characteristic strength and ease of use attributable to cement based materials. These composites show promise as a new class of inexpensive cation exchange and/or chemical adsorbents that can be used for large scale applications.

  15. Rapid crystallization of faujasitic zeolites: mechanism and application to zeolite membrane growth on polymer supports.

    PubMed

    Severance, Michael; Wang, Bo; Ramasubramanian, Kartik; Zhao, Lin; Ho, W S Winston; Dutta, Prabir K

    2014-06-17

    Zeolites are microporous, crystalline aluminosilicates with the framework made up of T-O-T (T = Si, Al) bonds and enclosed cages and channels of molecular dimensions. Influencing and manipulating the nucleation and growth characteristics of zeolites can lead to novel frameworks and morphologies, as well as decreased crystallization time. In this study, we show that manipulating the supersaturation during synthesis of zeolite X/Y (FAU) via dehydration led to extensive nucleation. Controlled addition of water to this nucleated state promotes the transport of nutrients, with a 4-fold increase in the rate of crystal growth, as compared to conventional hydrothermal process. Structural signature of the nucleated state was obtained by electron microscopy, NMR, and Raman spectroscopy. This extensively intermediate nucleated state was isolated and used as the starting material for zeolite membrane synthesis on porous polymer supports, with membrane formation occurring within an hour. With this time frame for growth, it becomes practical to fabricate zeolite/polymer membranes using roll-to-roll technology, thus making possible new commercial applications. PMID:24758695

  16. Thermodynamics of rock forming crystalline solutions

    NASA Technical Reports Server (NTRS)

    Saxena, S. K.

    1971-01-01

    Analysis of phase diagrams and cation distributions within crystalline solutions as means of obtaining thermodynamic data on rock forming crystalline solutions is discussed along with some aspects of partitioning of elements in coexisting phases. Crystalline solutions, components in a silicate mineral, and chemical potentials of these components were defined. Examples were given for calculating thermodynamic mixing functions in the CaW04-SrW04, olivine-chloride solution, and orthopyroxene systems.

  17. EFFECT OF QUARTZ/MULLITE BLEND CERAMIC ADDITIVE ON IMPROVING RESISTANCE TO ACID OF SODIUM SILICATE-ACTIVATED SLAG CEMENT. CELCIUS BRINE.

    SciTech Connect

    SUGAMA, T.; BROTHERS, L.E.; VAN DE PUTTE, T.R.

    2006-06-01

    We evaluated the usefulness of manufactured quartz/mullite blend (MQMB) ceramic powder in increasing the resistance to acid of sodium silicate-activated slag (SSAS) cementitious material for geothermal wells. A 15-day exposure to 90{sup o} CO{sub 2}-laden H{sub 2}SO{sub 4} revealed that the MQMB had high potential as an acid-resistant additive for SSAS cement. Two factors, the appropriate ratio of slag/MQMB and the autoclave temperature, contributed to better performance of MQMB-modified SSAS cement in abating its acid erosion. The most effective slag/MQMB ratio in minimizing the loss in weight by acid erosion was 70/30 by weight. For autoclave temperature, the loss in weight of 100 C autoclaved cement was a less than 2%, but at 300 C it was even lower. Before exposure to acid, the cement autoclaved at 100 C was essentially amorphous; increasing the temperature to 200 C led to the formation of crystalline analcime in the zeolitic mineral family during reactions between the mullite in MQMB and the Na from sodium silicate. In addition, at 300 C, crystal of calcium silicate hydrate (1) (CSH) was generated in reactions between the quartz in MQMB and the activated slag. These two crystalline phases (CSH and analcime) were responsible for densifying the autoclaved cement, conveying improved compressive strength and minimizing water permeability. The CSH was susceptible to reactions with H{sub 2}SO{sub 4}, forming two corrosion products, bassanite and ionized monosilicic acid. However, the uptake of ionized monosilicic acid by Mg dissociated from the activated slag resulted in the formation of lizardite as magnesium silicate hydrate. On the other hand, the analcime was barely susceptible to acid if at all. Thus, the excellent acid resistance of MQMB-modified SSAS cement was due to the combined phases of lizardite and analcime.

  18. Sodium clusters in zeolites

    NASA Astrophysics Data System (ADS)

    Grobet, P. J.; Martens, L. R. M.; Vermeiren, W. J. M.; Huybrechts, D. R. C.; Jacobs, P. A.

    1989-03-01

    The method of loading sodium clusters in zeolites, consisting of the controlled thermal decomposition of physisorbed sodium azide, is discussed. The influence of the azide loading, the azide decomposition rate and the sintering process on the amount of ionic and metallic sodium clusters in zeolite Y was followed by ESR. The method is compared to other metal deposition techniques.

  19. Dispersible Exfoliated Zeolite Nanosheets and Their Application as a Selective Membrane

    SciTech Connect

    Varoon, Kumar; Zhang, Xueyi; Elyassi, Bahman; Brewer, Damien D.; Gettel, Melissa; Kumar, Sandeep; Lee, J. Alex; Maheshwari, Sundeep; Mittal, Anudha; Sung, Chun-Yi; Cococcioni, Matteo; Francis, Lorraine F.; McCormick, Alon V.; Mkhoyan, K. Andre; Tsapatsis, Michael

    2011-10-06

    Thin zeolite films are attractive for a wide range of applications, including molecular sieve membranes, catalytic membrane reactors, permeation barriers, and low-dielectric-constant materials. Synthesis of thin zeolite films using high-aspect-ratio zeolite nanosheets is desirable because of the packing and processing advantages of the nanosheets over isotropic zeolite nanoparticles. Attempts to obtain a dispersed suspension of zeolite nanosheets via exfoliation of their lamellar precursors have been hampered because of their structure deterioration and morphological damage (fragmentation, curling, and aggregation). We demonstrated the synthesis and structure determination of highly crystalline nanosheets of zeolite frameworks MWW and MFI. The purity and morphological integrity of these nanosheets allow them to pack well on porous supports, facilitating the fabrication of molecular sieve membranes.

  20. Fly ash from a Mexican mineral coal. II. Source of W zeolite and its effectiveness in arsenic (V) adsorption.

    PubMed

    Medina, Adriana; Gamero, Prcoro; Almanza, Jos Manuel; Vargas, Alfredo; Montoya, Ascencin; Vargas, Gregorio; Izquierdo, Mara

    2010-09-15

    Coal-fired plants in Coahuila (Mexico) produce highly reactive fly ash (MFA), which is used in a one-step process as a raw material in producing zeolite. We explored two routes in the synthesis of zeolite: (a) direct MFA zeolitization, which resulted in the formation of W zeolite with KOH and analcime with NaOH and (b) a MFA fusion route, which resulted in the formation of zeolite W or chabazite with KOH and zeolite X or P with NaOH. No residual crystalline phases were present. When LiOH was employed, ABW zeolite with quartz and mullite were obtained. For both zeolitization routes, the nature of the alkali (KOH, NaOH, LiOH), the alkali/MFA ratio (0.23-1.46), and the crystallization temperature and time (90-175 degrees C; 8-24 h) were evaluated. Additionally, the effect of temperature and time on MFA fusion was studied. W zeolite was obtained by both zeolitization methods. The direct route is preferred because it is a straightforward method using soft reaction conditions that results in a high yield of low cost zeolites with large crystal agglomerates. It was demonstrated that aluminum modified W zeolite has the ability to remove 99% of the arsenic (V) from an aqueous solution of Na(2)HAsO(4).7H(2)O originally containing 740 ppb. PMID:20537461

  1. Influence of crystallite size on cation conductivity in faujasitic zeolites.

    PubMed

    Severance, Michael; Zheng, Yangong; Heck, Elizabeth; Dutta, Prabir K

    2013-12-19

    The influence of particle size on the ionic conductivity of ceramic materials is an active area of research, and novel effects are observed as particles approach the nanoscale in size. Zeolites are crystalline aluminosilicates with ion-exchangeable cations that are responsible for ionic conductivity at high temperatures. In this paper, we present systematic results for the first time of ionic conductivity in alkali metal ion-exchanged faujasitic zeolites with morphologies ranging from a zeolite membrane, micrometer-sized, submicrometer, and nanoparticles of zeolite. Using impedance spectroscopy in the range of 10 MHz to 0.1 Hz, we have obtained the activation energy (E(act)) of cation motion with these various morphologies in the temperature range of 525-625 °C. Overall, the E(act) decreases with Si/Al ratio. Surface modification of the zeolite particles was carried out with a silylating agent, which upon high temperature calcination should lead to the formation of a monolayer Si-O-Si film on the particle surface. This surface modification had minimal influence on the E(act) of micrometer-sized zeolites. However, E(act) increased rapidly as the zeolite particle approached the nanoscale. These observations led us to propose that, for the high-temperature, low-frequency (10(4)-10(5) Hz), long-range ionic conduction in zeolites, cation hopping across grain boundaries is relevant to ion transport, especially as the size of the crystallite approaches the nanoscale. Intergrain boundaries are more defective in the nanosized zeolite and contribute to the higher E(act). PMID:24041267

  2. Diagram of Zeolite Crystals

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Center for Advanced Microgravity Materials Processing (CAMMP) in Cambridge, MA, a NASA-sponsored Commercial Space Center, is working to improve zeolite materials for storing hydrogen fuel. CAMMP is also applying zeolites to detergents, optical cables, gas and vapor detection for environmental monitoring and control, and chemical production techniques that significantly reduce by-products that are hazardous to the environment. Depicted here is one of the many here complex geometric shapes which make them highly absorbent. Zeolite experiments have also been conducted aboard the International Space Station

  3. Zeolites: Exploring Molecular Channels

    SciTech Connect

    Arslan, Ilke; Derewinski, Mirek

    2015-05-22

    Synthetic zeolites contain microscopic channels, sort of like a sponge. They have many uses, such as helping laundry detergent lather, absorbing liquid in kitty litter, and as catalysts to produce fuel. Of the hundreds of types of zeolites, only about 15 are used for catalysis. PNNL catalysis scientists Ilke Arslan and Mirek Derewinksi are studying these zeolites to understand what make them special. By exploring the mystery of these microscopic channels, their fundamental findings will help design better catalysts for applications such as biofuel production.

  4. Hierarchical zeolites from class F coal fly ash

    NASA Astrophysics Data System (ADS)

    Chitta, Pallavi

    Fly ash, a coal combustion byproduct is classified as types class C and class F. Class C fly ash is traditionally recycled for concrete applications and Class F fly ash often disposed in landfills. Class F poses an environmental hazard due to disposal and leaching of heavy metals into ground water and is important to be recycled in order to mitigate the environmental challenges. A major recycling option is to reuse the fly ash as a low-cost raw material for the production of crystalline zeolites, which serve as catalysts, detergents and adsorbents in the chemical industry. Most of the prior literature of fly ash conversion to zeolites does not focus on creating high zeolite surface area zeolites specifically with hierarchical pore structure, which are very important properties in developing a heterogeneous catalyst for catalysis applications. This research work aids in the development of an economical process for the synthesis of high surface area hierarchical zeolites from class F coal fly ash. In this work, synthesis of zeolites from fly ash using classic hydrothermal treatment approach and fusion pretreatment approach were examined. The fusion pretreatment method led to higher extent of dissolution of silica from quartz and mullite phases, which in turn led to higher surface area and pore size of the zeolite. A qualitative kinetic model developed here attributes the difference in silica content to Si/Al ratio of the beginning fraction of fly ash. At near ambient crystallization temperatures and longer crystallization times, the zeolite formed is a hierarchical faujasite with high surface area of at least 360 m2/g. This work enables the large scale recycling of class F coal fly ash to produce zeolites and mitigate environmental concerns. Design of experiments was used to predict surface area and pore sizes of zeolites - thus obviating the need for intense experimentation. The hierarchical zeolite catalyst supports tested for CO2 conversion, yielded hydrocarbons up to C9, a performance attesting the hierarchal pore structure. The preliminary techno-economic feasibility assessment demonstrates a net energy saving of 75% and cost saving of 63% compared to the commercial zeolite manufacturing process.

  5. ZEOLITE CHARACTERIZATION TESTING

    SciTech Connect

    Jacobs, W; Herbert Nigg, H

    2007-09-13

    The Savannah River Site isolates tritium from its process streams for eventual recycling. This is done by catalyzing the formation of tritiated water (from process streams) and then sorbing that water on a 3A zeolite (molsieve) bed. The tritium is recovered by regenerating the saturated bed into a Mg-based water cracking unit. The process described has been in use for about 15 years. Recently chloride stress corrosion cracking (SCC) was noted in the system piping. This has resulted in the need to replace the corroded piping and associated molecular sieve beds. The source of chlorine has been debated and one possible source is the zeolite itself. Since new materials are being purchased for recently fabricated beds, a more comprehensive analysis protocol for characterizing zeolite has been developed. Tests on archived samples indicate the potential for mobile chloride species to be generated in the zeolite beds.

  6. Composite zeolite membranes

    DOEpatents

    Nenoff, Tina M.; Thoma, Steven G.; Ashley, Carol S.; Reed, Scott T.

    2002-01-01

    A new class of composite zeolite membranes and synthesis techniques therefor has been invented. These membranes are essentially defect-free, and exhibit large levels of transmembrane flux and of chemical and isotopic selectivity.

  7. Hydrothermal synthesis of ytterbium silicate nanoparticles.

    PubMed

    Chen, Hongfei; Gao, Yanfeng; Liu, Yun; Luo, Hongjie

    2010-02-15

    A simple, low-cost hydrothermal method was developed to synthesize 20-nm-diameter single-crystalline ytterbium silicate (Yb(2)Si(2)O(7) and Yb(2)SiO(5)) nanoparticles at 200 degrees C. This is nearly 1000 degrees C lower than that for the typical sol-gel route to ytterbium silicate powders. Obtained powders showed very low thermal conductivity, a suitable thermal expansion coefficient, and excellent thermal/structural stability, suggesting a potential application to environmental and thermal barrier coatings. Special focus was placed on assessing the hydrothermal reaction mechanism for particle formation. PMID:20085266

  8. Sol-gel synthesis and luminescence of unexpected microrod crystalline Ca 5La 5(SiO 4) 3(PO 4) 3O 2:Dy 3+ phosphors employing different silicate sources

    NASA Astrophysics Data System (ADS)

    Yan, Bing; Huang, Honghua

    2007-08-01

    Ca5La5(SiO4)3(PO4)3O2 doped with Dy3+ were synthesized by sol-gel technology with hybrid precursor employed four different silicate sources, 3-aminopropyl-trimethoxysilane (APMS), 3-aminopropyl-triethoxysilane (APES), 3-aminopropyl-methyl-diethoxysilane (APMES) and tetraethoxysilane (TEOS), respectively. The SEM diagraphs show that there exist some novel unexpected morphological structures of microrod owing to the crosslinking reagents than TEOS as silicate source for their amphipathy template effect. X-ray pictures confirm that Ca5La5(SiO4)3(PO4)3O2:Dy3+ compound is formed by a pure apatitic phase. The Dy3+ ions could emit white light in Ca5La5(SiO4)3(PO4)3O2 compound, and the ratio of Y/B is 1.1, when the Dy3+ doped concentration is 1.0 mol%.

  9. Zeolite A imidazolate frameworks.

    PubMed

    Hayashi, Hideki; Ct, Adrien P; Furukawa, Hiroyasu; O'Keeffe, Michael; Yaghi, Omar M

    2007-07-01

    Faujasite (FAU) and zeolite A (LTA) are technologically important porous zeolites (aluminosilicates) because of their extensive use in petroleum cracking and water softening. Introducing organic units and transition metals into the backbone of these types of zeolite allows us to expand their pore structures, enhance their functionality and access new applications. The invention of metal-organic frameworks and zeolitic imidazolate frameworks (ZIFs) has provided materials based on simple zeolite structures where only one type of cage is present. However, so far, no metal-organic analogues based on FAU or LTA topologies exist owing to the difficulty imposed by the presence of two types of large cage (super- and beta-cages for FAU, alpha- and beta-cages for LTA). Here, we have identified a strategy to produce an LTA imidazolate framework in which both the link geometry and link-link interactions play a decisive structure-directing role. We describe the synthesis and crystal structures of three porous ZIFs that are expanded analogues of zeolite A; their cage walls are functionalized, and their metal ions can be changed without changing the underlying LTA topology. Hydrogen, methane, carbon dioxide and argon gas adsorption isotherms are reported and the selectivity of this material for carbon dioxide over methane is demonstrated. PMID:17529969

  10. Zeolite A imidazolate frameworks

    NASA Astrophysics Data System (ADS)

    Hayashi, Hideki; Ct, Adrien P.; Furukawa, Hiroyasu; O'Keeffe, Michael; Yaghi, Omar M.

    2007-07-01

    Faujasite (FAU) and zeolite A (LTA) are technologically important porous zeolites (aluminosilicates) because of their extensive use in petroleum cracking and water softening. Introducing organic units and transition metals into the backbone of these types of zeolite allows us to expand their pore structures, enhance their functionality and access new applications. The invention of metal-organic frameworks and zeolitic imidazolate frameworks (ZIFs) has provided materials based on simple zeolite structures where only one type of cage is present. However, so far, no metal-organic analogues based on FAU or LTA topologies exist owing to the difficulty imposed by the presence of two types of large cage (super- and ?-cages for FAU, ?- and ?-cages for LTA). Here, we have identified a strategy to produce an LTA imidazolate framework in which both the link geometry and link-link interactions play a decisive structure-directing role. We describe the synthesis and crystal structures of three porous ZIFs that are expanded analogues of zeolite A; their cage walls are functionalized, and their metal ions can be changed without changing the underlying LTA topology. Hydrogen, methane, carbon dioxide and argon gas adsorption isotherms are reported and the selectivity of this material for carbon dioxide over methane is demonstrated.

  11. Hydraulic conductivity of compacted zeolites.

    PubMed

    Oren, A Hakan; Ozdamar, Tu?e

    2013-06-01

    Hydraulic conductivities of compacted zeolites were investigated as a function of compaction water content and zeolite particle size. Initially, the compaction characteristics of zeolites were determined. The compaction test results showed that maximum dry unit weight (?(dmax)) of fine zeolite was greater than that of granular zeolites. The ?(dmax) of compacted zeolites was between 1.01 and 1.17 Mg m(-3) and optimum water content (w(opt)) was between 38% and 53%. Regardless of zeolite particle size, compacted zeolites had low ?(dmax) and high w(opt) when compared with compacted natural soils. Then, hydraulic conductivity tests were run on compacted zeolites. The hydraulic conductivity values were within the range of 2.0 10(-3) cm s(-1) to 1.1 10(-7) cm s(-1). Hydraulic conductivity of all compacted zeolites decreased almost 50 times as the water content increased. It is noteworthy that hydraulic conductivity of compacted zeolite was strongly dependent on the zeolite particle size. The hydraulic conductivity decreased almost three orders of magnitude up to 39% fine content; then, it remained almost unchanged beyond 39%. Only one report was found in the literature on the hydraulic conductivity of compacted zeolite, which is in agreement with the findings of this study. PMID:23460541

  12. Structural analysis of hierarchically organized zeolites

    NASA Astrophysics Data System (ADS)

    Mitchell, Sharon; Pinar, Ana B.; Kenvin, Jeffrey; Crivelli, Paolo; Krger, Jrg; Prez-Ramrez, Javier

    2015-10-01

    Advances in materials synthesis bring about many opportunities for technological applications, but are often accompanied by unprecedented complexity. This is clearly illustrated by the case of hierarchically organized zeolite catalysts, a class of crystalline microporous solids that has been revolutionized by the engineering of multilevel pore architectures, which combine unique chemical functionality with efficient molecular transport. Three key attributes, the crystal, the pore and the active site structure, can be expected to dominate the design process. This review examines the adequacy of the palette of techniques applied to characterize these distinguishing features and their catalytic impact.

  13. Silicon substituted y zeolite composition lz-210

    SciTech Connect

    Skeels, G.W.; Breck, D.W.

    1987-12-08

    A crystalline zeolitic aluminosilicate is described having at least some of its original framework aluminum atoms replaced by extraneous silicon atoms and having a mole ratio of oxides in the anhydrous state of wherein M is a cation having a valence of ''n''; ''x'' has a value greater than 6.0; has a X-ray powder diffraction pattern having at least the d-spacings of Table A; and has extraneous silicon atoms in the crystal lattice in the form of framework SiO/sub 4/ tetrahedra.

  14. Structural analysis of hierarchically organized zeolites

    PubMed Central

    Mitchell, Sharon; Pinar, Ana B.; Kenvin, Jeffrey; Crivelli, Paolo; Kärger, Jörg; Pérez-Ramírez, Javier

    2015-01-01

    Advances in materials synthesis bring about many opportunities for technological applications, but are often accompanied by unprecedented complexity. This is clearly illustrated by the case of hierarchically organized zeolite catalysts, a class of crystalline microporous solids that has been revolutionized by the engineering of multilevel pore architectures, which combine unique chemical functionality with efficient molecular transport. Three key attributes, the crystal, the pore and the active site structure, can be expected to dominate the design process. This review examines the adequacy of the palette of techniques applied to characterize these distinguishing features and their catalytic impact. PMID:26482337

  15. Structural analysis of hierarchically organized zeolites.

    PubMed

    Mitchell, Sharon; Pinar, Ana B; Kenvin, Jeffrey; Crivelli, Paolo; Krger, Jrg; Prez-Ramrez, Javier

    2015-01-01

    Advances in materials synthesis bring about many opportunities for technological applications, but are often accompanied by unprecedented complexity. This is clearly illustrated by the case of hierarchically organized zeolite catalysts, a class of crystalline microporous solids that has been revolutionized by the engineering of multilevel pore architectures, which combine unique chemical functionality with efficient molecular transport. Three key attributes, the crystal, the pore and the active site structure, can be expected to dominate the design process. This review examines the adequacy of the palette of techniques applied to characterize these distinguishing features and their catalytic impact. PMID:26482337

  16. Preparation of functionalized zeolitic frameworks

    DOEpatents

    Yaghi, Omar M.; Hayashi, Hideki; Banerjee, Rahul; Park, Kyo Sung; Wang, Bo; Cote, Adrien P.

    2014-08-19

    The disclosure provides zeolitic frameworks for gas separation, gas storage, catalysis and sensors. More particularly the disclosure provides zeolitic frameworks (ZIFs). The ZIF of the disclosure comprises any number of transition metals or a homogenous transition metal composition.

  17. Preparation of functionalized zeolitic frameworks

    DOEpatents

    Yaghi, Omar M; Hayashi, Hideki; Banerjee, Rahul; Park, Kyo Sung; Wang, Bo; Cote, Adrien P

    2012-11-20

    The disclosure provides zeolitic frameworks for gas separation, gas storage, catalysis and sensors. More particularly the disclosure provides zeolitic frameworks (ZIFs). The ZIF of the disclosure comprises any number of transition metals or a homogenous transition metal composition.

  18. Preparation of functionalized zeolitic frameworks

    DOEpatents

    Yaghi, Omar M; Furukawa, Hiroyasu; Wang, Bo

    2013-07-09

    The disclosure provides zeolitic frameworks for gas separation, gas storage, catalysis and sensors. More particularly the disclosure provides zeolitic frameworks (ZIFs). The ZIF of the disclosure comprises any number of transition metals or a homogenous transition metal composition.

  19. A Highly Ion-Selective Zeolite Flake Layer on Porous Membranes for Flow Battery Applications.

    PubMed

    Yuan, Zhizhang; Zhu, Xiangxue; Li, Mingrun; Lu, Wenjing; Li, Xianfeng; Zhang, Huamin

    2016-02-01

    Zeolites are crystalline microporous aluminosilicates with periodic arrangements of cages and well-defined channels, which make them very suitable for separating ions of different sizes, and thus also for use in battery applications. Herein, an ultra-thin ZSM-35 zeolite flake was introduced onto a poly(ether sulfone) based porous membrane. The pore size of the zeolite (ca. 0.5?nm) is intermediary between that of hydrated vanadium ions (>0.6?nm) and protons (<0.24?nm). The resultant membrane can thus be used to perfectly separate vanadium ions and protons, making this technology useful in vanadium flow batteries (VFB). A VFB with a zeolite-coated membrane exhibits a columbic efficiency of >99?% and an energy efficiency of >81?% at 200?mA?cm(-2) , which is by far the highest value ever reported. These convincing results indicate that zeolite-coated membranes are promising in battery applications. PMID:26822866

  20. Phosphorus Equilibria Among Mafic Silicate Phases

    NASA Technical Reports Server (NTRS)

    Berlin, Jana; Xirouchakis, Dimitris

    2002-01-01

    Phosphorus incorporation in major rock-forming silicate minerals has the following implications: (1) Reactions between phosphorus-hosting major silicates and accessory phosphates, which are also major trace element carriers, may control the stability of the latter and thus may affect the amount of phosphorus and other trace elements released to the coexisting melt or fluid phase. (2) Less of a phosphate mineral is needed to account for the bulk phosphorus of planetaty mantles. (3) During partial melting of mantle mineral assemblages or equilibrium fractional crystallization of basaltic magmas, and in the absence or prior to saturation with a phosphate mineral, silicate melts may become enriched in phosphorus, especially in the geochemically important low melt fraction regime, Although the small differences in the ionic radii of IVp5+, IVSi4+, and IV Al3+ makes phosphoms incorporation into crystalline silicates perhaps unsurprising, isostructural silicate and phosphate crystalline solids do not readily form solutions, e.g., (Fe, Mg)2SiO4 vs. LiMgPO4, SiO)2 VS. AlPO4. Nonetheless, there are reports of, poorly characterized silico-phosphate phases in angrites , 2-4 wt% P2O5 in olivine and pyroxene grains in pallasites and reduced terestrial basalts which are little understood but potentially useful, and up to 17 wt% P2O5 in olivine from ancient slags. However, such enrichments are rare and only underscore the likelihood of phosphoms incorporation in silicate minerals. The mechanisms that allow phosphorus to enter major rock-forming silicate minerals (e.g., Oliv, Px, Gt) remain little understood and the relevant data base is limited. Nonetheless, old and new high-pressure (5-10 GPa) experimental data suggest that P2O5 wt% decreases from silica-poor to silica-rich compositions or from orthosilicate to chain silicate structures (garnet > olivine > orthopyroxene) which implies that phosphorus incorporation in silicates is perhaps more structure-than site-specific. The data also indicate that DXVliQP2O5 decrease in the same order, but DOVLiQP2O5 and DOpx/LiQP205 are likely constant, respectively equal to 0.08(3) and 0.007(4), in contrast, DG1ILiQP205 increases from 0.15(3) to 0.36(10) as garnet becomes majoritic, thus silica-enriched, and may also depend on liquid composition (SiO2, P2O5 and Na2O wt%).

  1. Energetic Processing of Interstellar Silicate Grains by Cosmic Rays

    SciTech Connect

    Bringa, E M; Kucheyev, S O; Loeffler, M J; Baragiola, R A; Tielens, A G Q M; Dai, Z R; Graham, G; Bajt, S; Bradley, J; Dukes, C A; Felter, T E; Torres, D F; van Breugel, W

    2007-03-28

    While a significant fraction of silicate dust in stellar winds has a crystalline structure, in the interstellar medium nearly all of it is amorphous. One possible explanation for this observation is the amorphization of crystalline silicates by relatively 'low' energy, heavy ion cosmic rays. Here we present the results of multiple laboratory experiments showing that single-crystal synthetic forsterite (Mg{sub 2}SiO{sub 4}) amorphizes when irradiated by 10 MeV Xe{sup ++} ions at large enough fluences. Using modeling, we extrapolate these results to show that 0.1-5.0 GeV heavy ion cosmic rays can rapidly ({approx}70 Million yrs) amorphize crystalline silicate grains ejected by stars into the interstellar medium.

  2. Zeolite-Dye Microlasers

    NASA Astrophysics Data System (ADS)

    Vietze, U.; Krauß, O.; Laeri, F.; Ihlein, G.; Schüth, F.; Limburg, B.; Abraham, M.

    1998-11-01

    We present a new class of micro lasers based on nanoporous molecular sieve host-guest systems. Organic dye guest molecules of 1-ethyl-4-[4-( p-dimethylaminophenyl)-1,3-butadienyl]-pyridinium Perchlorat were inserted into the 0.73-nm-wide channel pores of a zeolite AlPO 4-5 host. The zeolitic microcrystal compounds were hydrothermally synthesized according to a particular host-guest chemical process. The dye molecules are found not only to be aligned along the host channel axis, but to be oriented as well. Single mode laser emission at 687 nm was obtained from a whispering gallery mode oscillating in a 8-μm-diameter monolithic microresonator, in which the field is confined by total internal reflection at the natural hexagonal boundaries inside the zeolitic microcrystals.

  3. Mimicking high-silica zeolites: highly stable germanium- and tin-rich zeolite-type chalcogenides.

    PubMed

    Lin, Qipu; Bu, Xianhui; Mao, Chengyu; Zhao, Xiang; Sasan, Koroush; Feng, Pingyun

    2015-05-20

    High-silica zeolites, as exemplified by ZSM-5, with excellent chemical and thermal stability, have generated a revolution in industrial catalysis. In contrast, prior to this work, high-silica-zeolite-like chalcogenides based on germanium/tin remained unknown, even after decades of research. Here six crystalline high-germanium or high-tin zeolite-type sulfides and selenides with four different topologies are reported. Their unprecedented framework compositions give these materials much improved thermal and chemical stability with high surface area (Langmuir surface area of 782 m(2)/g(-1)) comparable to or better than zeolites. Among them, highly stable CPM-120-ZnGeS allows for ion exchange with diverse metal or complex cations, resulting in fine-tuning in porosity, fast ion conductivity, and photoelectric response. Being among the most porous crystalline chalcogenides, CPM-120-ZnGeS (exchanged with Cs(+) ions) also shows reversible adsorption with high capacity and affinity for CO2 (98 and 73 cm(3) g(-1) at 273 and 298 K, respectively, isosteric heat of adsorption = 40.05 kJ mol(-1)). Moreover, CPM-120-ZnGeS could also function as a robust photocatalyst for water reduction to generate H2. The overall activity of H2 production from water, in the presence of Na2S-Na2SO3 as a hole scavenger, was 200 ?mol h(-1)/(0.10 g). Such catalytic activity remained undiminished under illumination by UV light for as long as measured (200 h), demonstrating excellent resistance to photocorrosion even under intense UV radiation. PMID:25950820

  4. Topotactic condensation of layer silicates with ferrierite-type layers forming porous tectosilicates.

    PubMed

    Marler, B; Wang, Y; Song, J; Gies, H

    2014-07-21

    Five different hydrous layer silicates (HLSs) containing fer layers (ferrierite-type layers) were obtained by hydrothermal syntheses from mixtures of silicic acid, water and tetraalkylammonium/tetraalkylphosphonium hydroxides. The organic cations had been added as structure directing agents (SDA). A characteristic feature of the structures is the presence of strong to medium strong hydrogen bonds between the terminal silanol/siloxy groups of neighbouring layers. The five-layered silicates differ chemically only with respect to the organic cations. Structurally, they differ with respect to the arrangement of the fer layers relative to each other, which is distinct for every SDA-fer-layer system. RUB-20 (containing tetramethylammonium) and RUB-40 (tetramethylphosphonium) are monoclinic with stacking sequence AAA and shift vectors between successive layers 1a0 + 0b0 + 0.19c0 and 1a0 + 0b0 + 0.24c0, respectively. RUB-36 (diethyldimethylammonium), RUB-38 (methyltriethylammonium) and RUB-48 (trimethylisopropylammonium) are orthorhombic with stacking sequence ABAB and shift vectors 0.5a0 + 0b0 0.36c0, 0.5a0 + 0b0 + 0.5c0 and 0.5a0 + 0b0 0.39c0, respectively. Unprecedented among the HLSs, two monoclinic materials are made up of fer layers which possess a significant amount of ordered defects within the layer. The ordered defects involve one particular Si-O-Si bridge which is, to a fraction of ca. 50%, hydrolyzed to form nests of two ?Si-OH groups. When heated to 500-600 C in air, the HLSs condense to form framework silicates. Although all layered precursors were moderately to well ordered, the resulting framework structures were of quite different crystallinity. The orthorhombic materials RUB-36, -38 and -48, general formula SDA4Si36O72(OH)4, which possess very strong hydrogen bonds (d[OO] ? 2.4 ), transform into a fairly or well ordered CDO-type silica zeolite RUB-37. The monoclinic materials RUB-20 and -40, general formula SDA2Si18O36(OH)2OH, possessing medium strong hydrogen bonds (d[OO] ? 2.65 ) are transformed into poorly ordered framework silicates. Some rules of thumb can be established concerning the successful zeolite synthesis via a topotactic condensation of layered precursors. Favourably, the precursor (i) possesses already a well ordered structure without defects, (ii) contains strong inter-layer hydrogen bonds and does not contain strong intra-layer hydrogen bonds and (iii) contains a suitable cation. The nature of the organic cation (size, geometry, flexibility, thermal stability) plays a key role in the formation of a microporous tectosilicate with well ordered structure. RUB-36 which meets these criteria yields a well ordered condensation product (RUB-37). PMID:24875843

  5. Mg/Fe FRACTIONATION IN CIRCUMSTELLAR SILICATE DUST INVOLVED IN CRYSTALLIZATION

    SciTech Connect

    Murata, K.; Takakura, T.; Chihara, H.; Koike, C.; Tsuchiyama, A.

    2009-05-10

    Infrared astronomical observations of oxygen-rich young and evolved stars show that only magnesium-rich crystalline silicates exist in circumstellar regions, and iron, one of the most important dust-forming elements, is extremely depleted. The compositional characteristic of circumstellar crystalline silicates is fundamentally different from that of primitive extraterrestrial materials in our solar system, such as chondritic meteorites and interplanetary dust particles. Amorphous silicates are ubiquitous and abundant in space, and are a promising carrier of iron. However, since the first detection of crystalline silicates, there has been an unsolved inconsistency due to differing compositions of coexisting crystalline and amorphous phases, considering that amorphous silicates have been expected to be precursors of these crystals. Here we show the first experimental evidence that Fe-depleted olivine can be formed by crystallization via thermal heating of FeO-bearing amorphous silicates under subsolidus conditions. Mg/Fe fractionation involved in crystallization makes possible to coexist Mg-rich crystalline silicates with Fe-bearing amorphous silicates around stars.

  6. Silicate volcanism on Io

    NASA Technical Reports Server (NTRS)

    Carr, M. H.

    1986-01-01

    This paper is mainly concerned with the nature of volcanic eruptions on Io, taking into account questions regarding the presence of silicates or sulfur as principal component. Attention is given to the generation of silicate magma, the viscous dissipation in the melt zone, thermal anomalies at eruption sites, and Ionian volcanism. According to the information available about Io, it appears that its volcanism and hence its surface materials are dominantly silicic. Several percent of volatile materials such as sulfur, but also including sodium- and potassium-rich materials, may also be present. The volatile materials at the surface are continually vaporized and melted as a result of the high rates of silicate volcanism.

  7. Optical Properties of Astronomical Silicates in the Far-infrared

    NASA Technical Reports Server (NTRS)

    Rinehart, Stephen A,; Benford, Dominic J.; Dwek, Eli; Henry, Ross M.; Nuth, Joseph A., III; Silverberg, Robert f.; Wollack, Edward J.

    2008-01-01

    Correct interpretation of a vast array of astronomical data relies heavily on understanding the properties of silicate dust as a function of wavelength, temperature, and crystallinity. We introduce the QPASI-T (Optical Properties of Astronomical Silicates with Infrared Techniques) project to address the need for high fidelity optical characterization data on the various forms of astronomical dust. We use two spectrometers to provide extinction data for silicate samples across a wide wavelength range (from the near infrared to the millimeter). New experiments are in development that will provide complementary information on the emissivity of our samples, allowing us to complete the optical characterization of these dust materials. In this paper, we present initial results from several materials including amorphous iron silicate, magnesium silicate and silica smokes, over a wide range of temperatures, and discuss the design and operation of our new experiments.

  8. Monodispersed Ultrafine Zeolite Crystal Particles by Microwave Hydrothermal Synthesis

    SciTech Connect

    Hu, Michael Z.; Harris, Michael Tyrone; Khatri, Lubna

    2008-01-01

    Microwave hydrothermal synthesis of zeolites is reviewed. Monodispersed ultrafine crystal particles of zeolite (Silicalite-1) have been synthesized in batch reactor vessels by microwave irradiation heating of aqueous basic silicate precursor solutions with tetra propyl ammonium hydroxide as the templating molecule. The effects of major process parameters (such as synthesis temperature, microwave heating rate, volume ratio (i.e., the volume of the initial synthesis solution over the total volume of the reactor vessel), and synthesis time on the zeolite particle characteristics are studied using a computer-controlled microwave reactor system that allows real-time monitoring and control of reaction medium temperature. The changes in the morphology, size and crystal structure of the particles are investigated using scanning electron microscope, dynamic light scattering, X-ray diffraction, and BET surface analysis. We have found that the synthesis temperature, volume ratio, and heating rate play a significant role in controlling the particle size, uniformity, and morphology. Microwave processing has generated new morphologies of zeolite particles (i.e., uniform block-shaped particles that contain mixed gel-nanocrystallites and agglomerated crystal particles) that could not be made by a conventional hydrothermal process. At higher synthesis temperature and lower volume ratio, irregular block-shaped particles were produced, whereas increasing the volume ratio promoted the formation of monodispersed single-crystal particles with uniform shape. Our results clearly demonstrate that faster microwave heating is advantageous to enhance the zeolite crystallization kinetics and produces larger-size crystal particles in shorter time. In addition, zeolite crystallization mechanisms, depending on the microwave heating rate, were also discussed.

  9. Synthesis, deposition and characterization of magnesium hydroxide nanostructures on zeolite 4A

    SciTech Connect

    Koh, Pei-Yoong; Yan, Jing; Ward, Jason; Koros, William J.; Teja, Amyn S.; Xu, Bo

    2011-03-15

    Research highlights: {yields} Reports a simple precipitation-growth method to produce nanostructures of Mg(OH){sub 2} on the surface of zeolite 4A. {yields} Able to control the growth of the nanostructures by manipulating the experimental procedure. {yields} Able to deposit Mg(OH){sub 2} onto specific sites namely bridging hydroxyl protons (SiOHAl) on the surface of zeolite 4A. -- Abstract: The precipitation and self-assembly of magnesium hydroxide Mg(OH){sub 2} nanopetals on dispersed zeolite 4A particles was investigated. Mg(OH){sub 2}/zeolite nanocomposites were produced from magnesium chloride solutions and characterized via X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transform infrared analysis (FTIR), and solid state NMR. It was determined that Mg(OH){sub 2} interacted with bridging hydroxyl protons (SiOHAl) on the zeolite surface, but not with silanol or aluminol groups. NMR analysis showed that 13% of the tetrahedral Al sites on the zeolite were converted to octahedral Al. The zeolite structure and crystallinity remained intact after treatment, and no dealumination reactions were detected. This suggests that the deposition-precipitation process at ambient conditions is a facile method for controlling Mg(OH){sub 2} nanostructures on zeolites.

  10. Association of Indigo with Zeolites for Improved Color Stabilization

    NASA Astrophysics Data System (ADS)

    Dejoie, Catherine; Martinetto, Pauline; Dooryhe, Eric; van Elslande, Elsa; Blanc, Sylvie; Bordat, Patrice; Brown, Ross; Porcher, Florence; Anne, Michel

    2010-10-01

    The durability of an organic colour and its resistance against external chemical agents and exposure to light can be significantly enhanced by hybridizing the natural dye with a mineral. In search for stable natural pigments, the present work focuses on the association of indigo blue with several zeolitic matrices (LTA zeolite, mordenite, MFI zeolite). The manufacturing of the hybrid pigment is tested under varying oxidising conditions, using Raman and UV-visible spectrometric techniques. Blending indigo with MFI is shown to yield the most stable composite in all of our artificial indigo pigments. In absence of defects and substituted cations such as aluminum in the framework of the MFI zeolite matrix, we show that matching the pore size with the dimensions of the guest indigo molecule is the key factor. The evidence for the high colour stability of indigo@MFI opens a new path for modeling the stability of indigo in various alumino-silicate substrates such as in the historical Maya Blue pigment.

  11. IMPROVED CATALYSTS FOR HEAVY OIL UPGRADING BASED ON ZEOLITE Y NANOPARTICLES ENCAPSULATED IN STABLE NANOPOROUS HOSTS

    SciTech Connect

    Conrad Ingram

    2003-09-03

    The focus of this project is to improve the catalytic performance of zeolite Y for petroleum hydrocracking by synthesizing nanoparticles of the zeolite ({approx}20-25 nm) inside nanoporous silicate or aluminosilicate hosts. The encapsulated zeolite nanoparticles are expected to possess reduced diffusional path lengths, hence hydrocarbon substrates will diffuse in, are converted and the products quickly diffused out. This is expected to prevent over-reaction and the blocking of the zeolite pores and active sites will be minimized. In this phase of the project, procedures for the synthesis of ordered nanoporous silica, such as SBA-15, using block copolymers and nonionic surfactant were successful reproduced. Expansion of the pores sizes of the nanoporous silica using trimethylbenzene is suggested based on shift in the major X-Ray Diffraction peak in the products to lower 2 angles compared with the parent SBA-15 material. The synthesis of ordered nanoporous materials with aluminum incorporated in the predominantly silicate framework was attempted but is not yet successful, and the procedures needs will be repeated and modified as necessary. Nanoparticles of zeolite Y of particle sizes in the range 40 nm to 120 nm were synthesized in the presence of TMAOH as the particle size controlling additive.

  12. Formation of Magnesium Silicates is Limited around Evolved Stars

    NASA Astrophysics Data System (ADS)

    Kimura, Yuki; Nuth, J. A., III

    2009-05-01

    Laboratory experiments suggest that magnesium silicide (Mg2Si) grains could be produced in the hydrogen dominant gas outflow from evolved stars in addition to amorphous oxide minerals. Astronomical observations have shown the existence of abundant silicate grains around evolved stars and we have long realized that most of the silicate grains are amorphous, based on the observed infrared features. Only high mass loss stars show the feature attributed to magnesium-rich crystalline silicate about 10-20 % respect to total silicates, so far. The lower degree of crystallinity observed in silicates formed in outflows of lower mass-loss-rate stars might be caused by the formation of magnesium silicide in this relatively hydrogen-rich environment. As a result of predominant distribution of magnesium into the silicide, the composition of interstellar amorphous silicates could be magnesium poor compared with silicon. Indeed, the chemical composition of isotopically anomalous GEMS (glass with embedded metal and sulfides) is magnesium poor with respect to a forsteritic composition (Floss et al. 2006; Keller & Messenger 2007). Infrared observations suggest that there is little or no crystalline forsterite in interstellar environments while there is an abundance of crystalline forsterite in our Solar System. If the forsterite is a result of the oxidation of interstellar magnesium silicide, then it is clear both why crystalline forsterite is stoichiometric olivine and why the chemical composition of isotopically anomalous GEMS is magnesium poor with respect to a forsteritic composition. In addition, it may also explain why the chemical composition of olivine is iron poor. Unfortunately, magnesium silicide has never been detected via astronomical observation or in the analysis of primitive meteorites. I would suggest that future analysis of meteorites and theoretical calculations could confirm the possibility of the formation of magnesium silicide grains around evolved stars.

  13. Synthesis of new zeolite structures.

    PubMed

    Li, Jiyang; Corma, Avelino; Yu, Jihong

    2015-10-21

    The search for new zeolites is of continuous interest in the field of zeolite science because of their widespread application in catalysis and adsorption-separation. To this end, considerable efforts have been devoted to the preparation of new zeolites with novel porous architectures and compositions. Taking account of the key factors governing the formation of zeolites (e.g., guest species, framework elements, construction processes, etc.), several synthetic strategies have been developed recently. These allow the discovery of many new zeolites with unprecedented structural features, such as hierarchical pores, odd-ring numbers (11-, 15-rings), extra-large pores (16-, 18-, 20-, 28-, and 30-rings), chiral pores, and extremely complex framework topologies, etc. In this review, we will present the advances in the synthesis of new zeolite structures in the last decade, which are achieved by utilization of the synthetic strategies based on pre-designed structure-directing agents, heteroatom substitution, and topotactic transformations. PMID:25740693

  14. Zeolite crystal growth in space

    NASA Technical Reports Server (NTRS)

    Sacco, Albert, Jr.; Thompson, Robert W.; Dixon, Anthony G.

    1991-01-01

    The growth of large, uniform zeolite crystals in high yield in space can have a major impact on the chemical process industry. Large zeolite crystals will be used to improve basic understanding of adsorption and catalytic mechanisms, and to make zeolite membranes. To grow large zeolites in microgravity, it is necessary to control the nucleation event and fluid motion, and to enhance nutrient transfer. Data is presented that suggests nucleation can be controlled using chemical compounds (e.g., Triethanolamine, for zeolite A), while not adversely effecting growth rate. A three-zone furnace has been designed to perform multiple syntheses concurrently. The operating range of the furnace is 295 K to 473 K. Teflon-lined autoclaves (10 ml liquid volume) have been designed to minimize contamination, reduce wall nucleation, and control mixing of pre-gel solutions on orbit. Zeolite synthesis experiments will be performed on USML-1 in 1992.

  15. Pyrolytic Synthesis of Carbon Nanotubes from Sucrose on a Mesoporous Silicate

    NASA Technical Reports Server (NTRS)

    Abdel-Fattah, Tarek; Siochi, Mia; Crooks, Roy

    2005-01-01

    Multiwall carbon nanotubes were synthesized from sucrose by a pyrolytic technique using mesoporous MCM-41 silicate templates without transition metal catalysts. The Nanotubes were examined in the carbon/silicate composite and after dissolution of the silicate. High resolution transmission electron microscopy study of the multiwall nanotubes showed them to be 15 nm in diameter, 200 nm in length and close-ended. There was variation in crystallinity with some nanotubes showing disordered wall structures.

  16. Effects of crystalline structures and surface functional groups on the adsorption of haloacetic acids by inorganic materials.

    PubMed

    Punyapalakul, Patiparn; Soonglerdsongpha, Suwat; Kanlayaprasit, Chutima; Ngamcharussrivichai, Chawalit; Khaodhiar, Sutha

    2009-11-15

    The effects of the crystalline structure and surface functional groups of porous inorganic materials on the adsorption of dichloroacetic acid (DCAA) were evaluated by using hexagonal mesoporous silicates (HMS), two surface functional group (3-aminopropyltriethoxy- and 3-mercaptopropyl-) modified HMSs, faujasite Y zeolite and activated alumina as adsorbents, and compared with powdered activated carbon (PAC). Selective adsorption of HAA(5) group was studied by comparing single and multiple-solute solution, including effect of common electrolytes in tap water. Adsorption capacities were significantly affected by the crystalline structure. Hydrogen bonding is suggested to be the most important attractive force. Decreasing the pH lower than the pH(zpc) increased the DCAA adsorption capacities of these adsorbents due to electrostatic interaction and hydrogen bonding caused by protonation of the hydronium ion. Adsorption capacities of HAA(5) on HMS did not relate to molecular structure of HAA(5). Common electrolytes did not affect the adsorption capacities and selectivity of HMS for HAA5, while they affected those of PAC. PMID:19592162

  17. SO2 REMOVAL FROM FLUE GASES USING UTILITY SYNTHESIZED ZEOLITES

    SciTech Connect

    MICHAEL GRUTZECK

    1998-10-31

    It is well known that natural and synthetic zeolites (molecular sieves) can adsorb gaseous SO2 from flue gas and do it more efficiently than lime based scrubbing materials. Unfortunately their cost ($500-$800 per ton) has deterred their use in this capacity. It is also known that zeolites are easy to synthesize from a variety of natural and man-made materials. The overall objective of the current work has been to evaluate the feasibility of having a utility synthesize its own zeolites, on-site, from fly ash and other recycled materials and then use these zeolites to adsorb SO2 from their flue gases. Work to date has shown that the efficiency of the capture process is related to the degree of crystallinity and the type of zeolite that forms in the samples. Normally, those samples cured at 150C contained a greater proportion of zeolite and as such were more SO2 adsorptive than their low-temperature counterparts. However, in order for the project to be successful, on site synthesis must remain an option, i.e. _100C synthesis. In light of this, the experimental focus now has two aspects. First, compositions of the starting materials are being altered by blending the current suite of fly ashes with other fly ashes, ground glass cullet and silica fume to promote the formation and growth of well crystallized and highly adsorptive zeolites. Second, greater degrees of reaction at significantly lower temperatures are being promote by ball milling the fly ash prior to use, by the use of more concentrated caustic solutions, and by the addition of zeolite seeds to the reactants. In all cases studies will focus on the effect of structure type and degree of conversion on SO2 adsorption. Future work will concentrate on the study of the effect of weathering on the suitability of converting fly ash into zeolites. This is an especially important study, considering the acres of fly ash now in storage throughout the country.

  18. SO2 REMOVAL FROM FLUE GASES USING UTILITY SYNTHESIZED ZEOLITES

    SciTech Connect

    Michael Grutzeck

    1999-04-30

    It is well known that natural and synthetic zeolites (molecular sieves) can adsorb gaseous SO{sub 2} from flue gas and do it more efficiently than lime based scrubbing materials. Unfortunately their cost ($500-$800 per ton) has deterred their use in this capacity. It is also known that zeolites are easy to synthesize from a variety of natural and man-made materials. The overall objective of the current work has been to evaluate the feasibility of having a utility synthesize its own zeolites, on-site, from fly ash and other recycled materials and then use these zeolites to adsorb SO{sub 2} from their flue gases. Work to date has shown that the efficiency of the capture process is related to the degree of crystallinity and the type of zeolite that forms in the samples. Normally, those samples cured at 150 C contained a greater proportion of zeolite and as such were more SO{sub 2} adsorptive than their low-temperature counterparts. However, in order for the project to be successful, on site synthesis must remain an option, i.e. 100 C synthesis. In light of this, the experimental focus now has two aspects. First, compositions of the starting materials are being altered by blending the current suite of fly ashes with ground glass cullet and silica fume to promote the formation and growth of well crystallized and highly adsorptive zeolites. Second, greater degrees of reaction at significantly lower temperatures are being promote by ball milling the fly ash prior to use, by the use of more concentrated caustic solutions, and by the addition of zeolite seeds to the reactants. In all cases studies will focus on the effect of structure type and degree of conversion on SO{sub 2} adsorption. Future work will concentrate on the study of the effect of weathering on the suitability of converting fly ash into zeolites. This is an especially important study, considering the acres of fly ash now in storage throughout the US.

  19. Effect of ultrasound energy on the zeolitization of chemical extracts from fused coal fly ash.

    PubMed

    Bukhari, Syed Salman; Rohani, Sohrab; Kazemian, Hossein

    2016-01-01

    This paper investigates the effects of ultrasound (UTS) energy at different temperatures on the zeolitization of aluminosilicate constituents of coal fly ash. UTS energy irradiated directly into the reaction mixture utilizing a probe immersed into the reaction mixture, unlike previously reported works that have used UTS baths. Controlled synthesis was also conducted at constant stirring and at the same temperatures using conventional heating. The precursor reaction solution was obtained by first fusing the coal fly ash with sodium hydroxide at 550°C followed by dissolution in water and filtration. The synthesized samples were characterized by XRF, XRD, SEM and TGA. The crystallinity of crystals produced with UTS assisted conversion compared to conventional conversion at 85°C was twice as high. UTS energy also reduced the induction time from 60 min to 40 min and from 80 min to 60 min for reaction temperatures of 95°C and 85°C, respectively. Prolonging the UTS irradiation at 95°C resulted in the conversion of zeolite-A crystals to hydroxysodalite, which is a more stable zeolitic phase. It was found that at 85°C coupled with ultrasound energy produced the best crystalline structure with a pure single phase of zeolite-A. It has been shown that crystallization using UTS energy can produce zeolitic crystals at lower temperatures and within 1h, dramatically cutting the synthesis time of zeolite. PMID:26384882

  20. Density functional modelling of silicate and aluminosilicate dimerisation solution chemistry.

    PubMed

    White, Claire E; Provis, John L; Kearley, Gordon J; Riley, Daniel P; van Deventer, Jannie S J

    2011-02-14

    Common throughout sol-gel chemistry, including zeolite synthesis, aluminosilicate glass formation and geopolymerisation, is the process of inorganic oxide polymerisation and deprotonation. In this investigation, some of the fundamental reactions occurring during zeolite synthesis and geopolymerisation at high pH are investigated using density functional theory (DFT), and are compared with: (i) existing values reported in the literature, and (ii) new and previously published DFT-derived data for similar silicate reactions at near-neutral pH. From the results it is seen that the energetics of deprotonation and dimerisation reactions depend greatly on the pH value, and these results correlate well with existing experimental values and trends. Hence, this investigation exemplifies that an accurate replication of the solution environment is crucial for obtaining useful theoretical results for species dissolved in non-ideal environments. PMID:21180742

  1. A theoretical study of Cu clusters in siliceous erionite

    NASA Astrophysics Data System (ADS)

    Antnez-Garca, Joel; Galvn, D. H.; Posada-Amarillas, A.; Petranovskii, Vitalii

    2014-02-01

    In terms of periodic density functional theory method, we present a theoretical study of the structure and electronic properties of different composites, obtained by the inclusion of distinct Cux (x=2,4,6,8) clusters within the C1 cage of siliceous erionite-zeolite. Results shows that for a periodic distribution of Cux clusters on zeolite, the hosting of those is trough electrostatic confinement which is governed by framework oxygen atoms located at particular equivalent sites. However, when the permanency of a cluster in a C1 cage is compromised, the cluster-cluster long range Coulomb interactions could rise to keep it inside. In addition, results also show that the electronic properties of free Cux clusters are largely transferred to the formed composite.

  2. Molecular Chemistry in a Zeolite: Genesis of a Zeolite Y-Supported Ruthenium Complex Catalyst

    SciTech Connect

    Ogino, I.; Gates, B.C.

    2009-05-22

    Dealuminated zeolite Y was used as a crystalline support for a mononuclear ruthenium complex synthesized from cis-Ru(acac){sub 2}(C{sub 2}H{sub 4}){sub 2}. Infrared (IR) and extended X-ray absorption fine structure spectra indicated that the surface species were mononuclear ruthenium complexes, Ru(acac)(C{sub 2}H{sub 4}){sub 2}{sup 2+}, tightly bonded to the surface by two Ru-O bonds at Al{sup 3+} sites of the zeolite. The maximum loading of the anchored ruthenium complexes was one complex per two Al{sup 3+} sites; at higher loadings, some of the cis-Ru(acac){sub 2}(C{sub 2}H{sub 4}){sub 2} was physisorbed. In the presence of ethylene and H{sub 2}, the surface-bound species entered into a catalytic cycle for ethylene dimerization and operated stably. IR data showed that at the start of the catalytic reaction, the acac ligand of the Ru(acac)(C{sub 2}H{sub 4}){sub 2}{sup 2+} species was dissociated and captured by an Al{sup 3+} site. Ethylene dimerization proceeded 600 times faster with a cofeed of ethylene and H{sub 2} than without H{sub 2}. These results provide evidence of the importance of the cooperation of the Al{sup 3+} sites in the zeolite and the H{sub 2} in the feed for the genesis of the catalytically active species. The results presented here demonstrate the usefulness of dealuminated zeolite Y as a nearly uniform support that allows precise synthesis of supported catalysts and detailed elucidation of their structures.

  3. Study of ethylene adsorption on zeolite NaY modified with group I metal ions

    NASA Astrophysics Data System (ADS)

    Sue-aok, Niramai; Srithanratana, Tipaporn; Rangsriwatananon, Kunwadee; Hengrasmee, Sunantha

    2010-04-01

    The adsorption of ethylene by zeolite NaY and zeolite NaY modified by cation exchange with potassium, rubidium, and cesium ions was studied. Cation exchanges were carried out using KNO 3, RbNO 3, and CsNO 3 in the concentration ranges of 0.2-10 mM. XRD patterns and specific surface areas illustrated that modification of NaY zeolite by very dilute solutions containing K +, Rb + and Cs + did not lead to significant changes in the crystallinity. Analysis of metals content (ICP-OES) showed that Cs + can replace Na + better than Rb + and K +. Particle analysis indicated slight decreases in surface area but pore volumes and pore diameters remained unchanged. Ethylene adsorption isotherms indicated that Na-Y zeolite which was modified by 5.0 mM KNO 3, 0.5 mM RbNO 3 and 1.0 mM CsNO 3 could adsorb ethylene better than zeolite Na-Y. K-NaY zeolite adsorbed up to 102.45 cm 3/g ethylene, while Rb-NaY and Cs-NaY zeolites adsorbed up to 98.50 cm 3/g and 90.15 cm 3/g ethylene, respectively. Ethylene adsorption capacities depended on number of adsorption sites and surface interactions.

  4. Hierarchical zeolites: enhanced utilisation of microporous crystals in catalysis by advances in materials design.

    PubMed

    Prez-Ramrez, Javier; Christensen, Claus H; Egeblad, Kresten; Christensen, Christina H; Groen, Johan C

    2008-11-01

    The introduction of synthetic zeolites has led to a paradigm shift in catalysis, separations, and adsorption processes, due to their unique properties such as crystallinity, high-surface area, acidity, ion-exchange capacity, and shape-selective character. However, the sole presence of micropores in these materials often imposes intracrystalline diffusion limitations, rendering low utilisation of the zeolite active volume in catalysed reactions. This critical review examines recent advances in the rapidly evolving area of zeolites with improved accessibility and molecular transport. Strategies to enhance catalyst effectiveness essentially comprise the synthesis of zeolites with wide pores and/or with short diffusion length. Available approaches are reviewed according to the principle, versatility, effectiveness, and degree of reality for practical implementation, establishing a firm link between the properties of the resulting materials and the catalytic function. We particularly dwell on the exciting field of hierarchical zeolites, which couple in a single material the catalytic power of micropores and the facilitated access and improved transport consequence of a complementary mesopore network. The carbon templating and desilication routes as examples of bottom-up and top-down methods, respectively, are reviewed in more detail to illustrate the benefits of hierarchical zeolites. Despite encircling the zeolite field, this review stimulates intuition into the design of related porous solids (116 references). PMID:18949124

  5. Temperature dependent thermal conductivity of pure silica MEL and MFI zeolite thin films

    NASA Astrophysics Data System (ADS)

    Fang, Jin; Huang, Yi; Lew, Christopher M.; Yan, Yushan; Pilon, Laurent

    2012-03-01

    This paper reports the temperature dependent cross-plane thermal conductivity of pure silica zeolite (PSZ) MFI and MEL thin films measured using the 3? method between 30 and 315 K. PSZ MFI thin films were b-oriented, fully crystalline, and had a 33% microporosity. PSZ MEL thin films consisted of MEL nanoparticles embedded in a nonuniform and porous silica matrix. They featured porosity, relative crystallinity, and particle size ranging from 40% to 59%, 23% to 47%, and 55 to 80 nm, respectively. Despite their crystallinity, MFI films had smaller thermal conductivity than that of amorphous silica due to strong phonon scattering by micropores. In addition, the effects of increased relative crystallinity and particle size on thermal conductivity of MEL thin films were compensated by the simultaneous increase in porosity. Finally, thermal conductivity of MFI zeolite was predicted and discussed using the Callaway model based on the Debye approximation.

  6. Adamantanes from petroleum, with zeolites

    SciTech Connect

    Rollmann, L.D.; Green, L.A.; Bradway, R.A.

    1995-12-31

    Experiments with zeolite Beta and zeolite {Upsilon} demonstrate that adamantane and methyl adamantanes can be isolated very effectively from modern refinery streams by mild hydrocracking over Pt- and Pd-containing large pore zeolites. Yield depends importantly on individual refinery crude source and process configuration. Heavy crudes and refineries with conventional hydrocracking and FCC feed hydrotreater facilities are particularly desirable, and an ideal feed for adamantane isolation in such a situation is the 150{degrees}-250{degrees}C fraction of the hydrocracker (HDC) recycle stream. When Pt- or Pd-containing zeolite Beta was used with such a stream, temperatures of some 250{degrees}C and pressures below 3.5 mPa (500 psig) sufficed to remove selectively well over 90% of the non-adamantane hydrocarbon, with little conversion of adamantanes. High selectivity for adamantanes is attributed in large part to size-selective exclusion of these molecules from the pores of zeolite Beta.

  7. Zeolite formation from coal fly ash and its adsorption potential.

    PubMed

    Ruen-ngam, Duangkamol; Rungsuk, Doungmanee; Apiratikul, Ronbanchob; Pavasant, Prasert

    2009-10-01

    The possibility in converting coal fly ash (CFA) to zeolite was evaluated. CFA samples from the local power plant in Prachinburi province, Thailand, were collected during a 3-month time span to account for the inconsistency of the CFA quality, and it was evident that the deviation of the quality of the raw material did not have significant effects on the synthesis. The zeolite product was found to be type X. The most suitable weight ratio of sodium hydroxide (NaOH) to CFA was approximately 2.25, because this gave reasonably high zeolite yield with good cation exchange capacity (CEC). The silica (Si)-to-aluminum (Al) molar ratio of 4.06 yielded the highest crystallinity level for zeolite X at 79% with a CEC of 240 meq/100 g and a surface area of 325 m2/g. Optimal crystallization temperature and time were 90 degrees C and 4 hr, respectively, which gave the highest CEC of approximately 305 meq/100 g. Yields obtained from all experiments were in the range of 50-72%. PMID:19842322

  8. Calibration analysis of zeolites by laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Horňáčková, M.; Grolmusová, Z.; Horňáček, M.; Rakovský, J.; Hudec, P.; Veis, P.

    2012-08-01

    Laser induced breakdown spectroscopy was used for calibration analysis of different types of microporous crystalline aluminosilicates with exactly ordered structure — zeolites. The LIBS plasma was generated using a Q-switched Nd:YAG laser operating at the wavelength of 532 nm and providing laser pulses of 4 ns duration. Plasma emission was analysed by echelle type emission spectrometer, providing wide spectral range 200-950 nm. The spectrometer was equipped with intensified CCD camera providing rapid spectral acquisition (gating time from 5 ns). The optimum experimental conditions (time delay, gate width and laser pulse energy) have been determined for reliable use of LIBS for quantitative analysis. Samples of different molar ratios of Si/Al were used to create the calibration curves. Calibration curves for different types of zeolites (mordenite, type Y and ZSM-5) were constructed. Molar ratios of Si/Al for samples used for calibration were determined by classical wet chemical analysis and were in the range 5.3-51.8 for mordenite, 2.3-12.8 for type Y and 14-600 for ZSM-5. Zeolites with these molar ratios of Si/Al are usually used as catalysts in alkylation reactions. Laser induced breakdown spectroscopy is a suitable method for analysis of molar ratio Si/Al in zeolites, because it is simple, fast, and does not require sample preparation compared with classical wet chemical analysis which are time consuming, require difficult sample preparation and manipulation with strong acids and bases.

  9. Zeolite formation from coal fly ash and its adsorption potential

    SciTech Connect

    Duangkamol Ruen-ngam; Doungmanee Rungsuk; Ronbanchob Apiratikul; Prasert Pavasant

    2009-10-15

    The possibility in converting coal fly ash (CFA) to zeolite was evaluated. CFA samples from the local power plant in Prachinburi province, Thailand, were collected during a 3-month time span to account for the inconsistency of the CFA quality, and it was evident that the deviation of the quality of the raw material did not have significant effects on the synthesis. The zeolite product was found to be type X. The most suitable weight ratio of sodium hydroxide (NaOH) to CFA was approximately 2.25, because this gave reasonably high zeolite yield with good cation exchange capacity (CEC). The silica (Si)-to-aluminum (Al) molar ratio of 4.06 yielded the highest crystallinity level for zeolite X at 79% with a CEC of 240 meq/100 g and a surface area of 325 m{sup 2}/g. Optimal crystallization temperature and time were 90{sup o}C and 4 hr, respectively, which gave the highest CEC of approximately 305 meq/100 g. Yields obtained from all experiments were in the range of 50-72%. 29 refs., 5 tabs., 7 figs.

  10. Synthesis of Foam-Shaped Nanoporous Zeolite Material: A Simple Template-Based Method

    ERIC Educational Resources Information Center

    Saini, Vipin K.; Pires, Joao

    2012-01-01

    Nanoporous zeolite foam is an interesting crystalline material with an open-cell microcellular structure, similar to polyurethane foam (PUF). The aluminosilicate structure of this material has a large surface area, extended porosity, and mechanical strength. Owing to these properties, this material is suitable for industrial applications such as

  11. Synthesis of Foam-Shaped Nanoporous Zeolite Material: A Simple Template-Based Method

    ERIC Educational Resources Information Center

    Saini, Vipin K.; Pires, Joao

    2012-01-01

    Nanoporous zeolite foam is an interesting crystalline material with an open-cell microcellular structure, similar to polyurethane foam (PUF). The aluminosilicate structure of this material has a large surface area, extended porosity, and mechanical strength. Owing to these properties, this material is suitable for industrial applications such as…

  12. Ultrafast synthesis of nano-sized zeolite SAPO-34 with excellent MTO catalytic performance.

    PubMed

    Sun, Qiming; Wang, Ning; Guo, Guanqi; Yu, Jihong

    2015-11-01

    Nano-sized SAPO-34 zeolites with high crystallinity are obtained in 10 minutes by fast heating the reaction gel in a stainless steel tubular reactor combined with the seed-assisted method, which show outstanding performance in methanol-to-olefin (MTO) reaction. PMID:26412585

  13. Solid-state radioluminescent zeolite-containing composition and light sources

    DOEpatents

    Clough, Roger L. (Albuquerque, NM); Gill, John T. (Miamisburg, OH); Hawkins, Daniel B. (Fairbanks, AK); Renschler, Clifford L. (Tijeras, NM); Shepodd, Timothy J. (Livermore, CA); Smith, Henry M. (Overland Park, KS)

    1992-01-01

    A new type of RL light source consisting of a zeolite crystalline material, the intralattice spaces of which a tritiated compound and a luminophore are sorbed, and which material is optionally further dispersed in a refractive index-matched polymer matrix.

  14. X-ray photoelectron spectroscopic investigation of nanocrystalline calcium silicate hydrates synthesised by reactive milling

    SciTech Connect

    Black, Leon . E-mail: l.black@shu.ac.uk; Garbev, Krassimir; Beuchle, Guenter; Stemmermann, Peter; Schild, Dieter

    2006-06-15

    X-ray photoelectron spectroscopy (XPS) has been used to analyse a series of mechanochemically synthesised, nanocrystalline calcium silicate hydrates (C-S-H). The samples, with Ca/Si ratios of 0.2 to 1.5, showed structural features of C-S-H(I). XPS analysis revealed changes in the extent of silicate polymerisation. Si 2p, Ca 2p and O 1s spectra showed that, unlike for the crystalline calcium silicate hydrate phases studied previously, there was no evidence of silicate sheets (Q{sup 3}) at low Ca/Si ratios. Si 2p and O 1s spectra indicated silicate depolymerisation, expressed by decreasing silicate chain length, with increasing C/S. In all spectra, peak narrowing was observed with increasing Ca/Si, indicating increased structural ordering. The rapid changes of the slope of FWHM of Si 2p, {delta} {sub Ca-Si} and {delta} {sub NBO-BO} as function of C/S ratio indicated a possible miscibility gap in the C-S-H-solid solution series between C/S 5/6 and 1. The modified Auger parameter ({alpha}') of nanocrystalline C-S-H decreased with increasing silicate polymerisation, a trend already observed studying crystalline C-S-H. Absolute values of {alpha}' were shifted about - 0.7 eV with respect to crystalline phases of equal C/S ratio, due to reduced crystallinity.

  15. European Microgravity Facilities for ZEOLITE Experiments on the International Space Station

    NASA Astrophysics Data System (ADS)

    Pletser, V.; Minster, O.; Kremer, S.; Kirschhock, C.; Martens, J.; Jacobs, P.

    2002-01-01

    Synthetic zeolites are complex porous silicates. Zeolites are applied as catalysts, adsorbents and sensors. Whereas the traditional applications are situated in the petrochemical area, zeolite catalysis and related zeolite-based technologies have a growing impact on the economics and sustainability of products and processes in a growing number of industrial sectors, including environmental protection and nanotechnology. A Sounding Rocket microgravity experiment led to significant insight in the physical aggregation patterns of zeolitic nanoscopic particles and the occurrence of self-organisation phenomena when undisturbed by convection. The opportunity of performing longer microgravity duration experiments on zeolite structures was recently offered in the frame of a Taxi-Flight to the ISS in November 2002 organized by Belgium and ESA. Two facilities are currently under development for this flight. One of them will use the Microgravity Science Glovebox (MSG) in the US Lab. Destiny to achieve thermal induced self-organization of different types of Zeosil nanoslabs by heating and cooling. The other facility will be flown on the ISS Russian segment and will allow to form Zeogrids at ambient temperature. On the other hand, the European Space Agency (ESA) is studying the possibility of developing a dedicated insert for zeolite experiments to be used with the optical and diagnostic platform of the Protein Crystallisation Diagnostic Facility (PCDF), that will fly integrated in the European Drawer Rack on the Columbus Laboratory starting in 2004. This paper will present the approach followed by ESA to prepare and support zeolite investigations in microgravity and will present the design concept of these three facilities.

  16. Hydrothermal alteration and zeolitization of the Fohberg phonolite, Kaiserstuhl Volcanic Complex, Germany

    NASA Astrophysics Data System (ADS)

    Weisenberger, Tobias Bjrn; Sprgin, Simon; Lahaye, Yann

    2014-11-01

    The subvolcanic Fohberg phonolite (Kaiserstuhl Volcanic Complex, Germany) is an economic zeolite deposit, formed by hydrothermal alteration of primary magmatic minerals. It is mined due to the high (>40 wt%) zeolite content, which accounts for the remarkable zeolitic physicochemical properties of the ground rock. New mineralogical and geochemical studies are carried out (a) to evaluate the manifestation of hydrothermal alteration, and (b) to constrain the physical and chemical properties of the fluids, which promoted hydrothermal replacement. The alkaline intrusion is characterized by the primary mineralogy: feldspathoid minerals, K-feldspar, aegirine-augite, wollastonite, and andradite. The rare-earth elements-phase gtzenite is formed during the late-stage magmatic crystallization. Fluid-induced re-equilibration of feldspathoid minerals and wollastonite caused breakdown to a set of secondary phases. Feldspathoid minerals are totally replaced by various zeolite species, calcite, and barite. Wollastonite breakdown results in the formation of various zeolites, calcite, pectolite, sepiolite, and quartz. Zeolites are formed during subsolidus hydrothermal alteration (<150 C) under alkaline conditions. A sequence of Ca-Na-dominated zeolite species (gonnardite, thomsonite, mesolite) is followed by natrolite. The sequence reflects an increase in and decrease in of the precipitating fluid. Low radiogenic 87Sr/86Sr values indicate a local origin of the elements necessary for secondary mineral formation from primary igneous phases. In addition, fractures cut the intrusive body, which contain zeolites, followed by calcite and a variety of other silicates, carbonates, and sulfates as younger generations. Stable isotope analysis of late-fracture calcite indicates very late circulation of meteoric fluids and mobilization of organic matter from surrounding sedimentary units.

  17. Hydrocracking process utilizing a catalyst having a reduced zeolite content

    SciTech Connect

    Abdo, S.F.

    1989-08-15

    This patent describes a process for refining hydrocarbon feedback containing organonitrogen components, organosulfur components or a mixture thereof. The process comprises: contacting the feedback with molecular hydrogen under hydrotreating conditions in the presence of a hydrotreating catalyst comprising a Group VIB metal component and a Group VIII metal component such that a subtantial proportion of the organonitrogen components, organosulfur components or mixture thereof is converted to ammonia, hydrogen sulfide or a mixture thereof; contacting substantially all of the effluent from the first step with molecular hydrogen in a first hydrocracking zone in the presence of a first hydrocracking catalyst comprising a zeolite and a hydrogeneration component to produce a hydrocracking product of substantially lower boiling point; separating the hydrocracking product into a higher boiling fraction and a lower boiling fraction; contacting the higher boiling fraction with molecular hydrogen in a second hydrocracking zone under hydrocracking conditions in an atmosphere which contains no more than about 200 ppmv ammonia and in the presence of a second hydrocracking catalyst to convert the higher boiling fraction into lower boiling products. The second hydrocracking catalysts comprises; a porous, inorganic refractory oxide component; and between about 40 weight percent and about 70 weight percent of a crystalline aluminosilicate Y zeolite having a silica-to-alumina mole ratio above about 6.0 intimately mixed with the refractory oxide component. The crystalline aluminosilicate Y zeolite having been ion-exchanged with Group VIII noble metal cations.

  18. Crystal Structure and Chemical Composition of a Presolar Silicate from the Queen Elizabeth Range 99177 Meteorite

    NASA Technical Reports Server (NTRS)

    Nguyen, A. N.; Keller, L. P.; Rahman, Z.; Messenger, S.

    2013-01-01

    Mineral characterization of presolar silicate grains, the most abundant stardust phase, has provided valuable information about the formation conditions in circumstellar environments and in super-nova (SN) outflows. Spectroscopic observations of dust around evolved stars suggest a majority of amor-phous, Mg-rich olivine grains, but crystalline silicates, most of which are pyroxene, have also been observed [1]. The chemical compositions of hundreds of presolar silicates have been determined by Auger spectroscopy and reveal high Fe contents and nonstoichiometric compositions intermediate to olivine and pyroxene [2-6]. The unexpectedly high Fe contents can partly be attributed to secondary alteration on the meteorite parent bodies, as some grains have Fe isotopic anomalies from their parent stellar source [7]. Only about 35 presolar silicates have been studied for their mineral structures and chemical compositions by transmission electron microscopy (TEM). These grains display a wide range of compositions and structures, including crystalline forsterite, crystalline pyroxene, nanocrystalline grains, and a majority of amorphous nonstoichiometric grains. Most of these grains were identified in the primitive Acfer 094 meteorite. Presolar silicates from this meteorite show a wide range of Fe-contents, suggestive of secondary processing on the meteorite parent body. The CR chondrite QUE 99177 has not suffered as much alteration [8] and displays the highest presolar silicate abundance to date among carbonaceous chondrites [3, 6]. However, no mineralogical studies of presolar silicates from this meteorite have been performed. Here we examine the mineralogy of a presolar silicate from QUE 99177.

  19. Oxygen and hydrogen isotope geochemistry of zeolites

    NASA Technical Reports Server (NTRS)

    Karlsson, Haraldur R.; Clayton, Robert N.

    1990-01-01

    Oxygen and hydrogen isotope ratios for natural samples of the zeolites analcime, chabazite, clinoptilolite, laumontite, mordenite, and natrolite have been obtained. The zeolite samples were classified into sedimentary, hydrothermal, and igneous groups. The ratios for each species of zeolite are reported. The results are used to discuss the origin of channel water, the role of zeolites in water-rock interaction, and the possibility that a calibrated zeolite could be used as a low-temperature geothermometer.

  20. Spectral and structural evolution in annealed amorphous Mg-silicates

    NASA Astrophysics Data System (ADS)

    Thompson, S. P.; Verrienti, C.; Fonti, S.; Orofino, V.; Blanco, A.; Lennie, A. R.

    The long residence times and disruptive processes experienced in interstellar space by silicate grains that originally condensed from the atmospheres of evolved O-rich stars is likely to have resulted in a homogenised population of pre-solar silicates with amorphous structures. However, prior to being incorporated into comet bodies during the initial phases of solar system formation, these grains are thought to have undergone substantial thermal processing in the early solar nebula. Depending on which regions of the nebula a given grain sampled, this would have resulted in either partial or complete structural rearrangement of the grain material into more ordered forms. This is widely believed to be the origin of the fine-structured features detected in the IR spectra at 10 and 20 um of certain comets today and attributed to crystalline silicate grains. To better understand the nature and thermal history of cometary silicates and to place physical constraints on both the extent of grain processing and on models of the early nebula it is therefore necessary to simulate the thermal processing of pre-solar silicates in the laboratory. To this end we have synthesised several amorphous Mg-rich silicates with compositions described by MgxSiyOz (where x, y, z have been determined by EDX analysis) and investigated their annealing response in the region of 1000K using the combined techniques of IR spectroscopy and high-resolution synchrotron x-ray powder diffraction. The main results of this investigation are (1) partially crystalline silicates produce spectral features at 10 and 20 um that resemble cometary features. (2) Partially crystalline silicates although exhibiting long-range crystal structure also show a large degree of disorder over short-length scales. (3) Thermal response is strongly dependent on composition. (4) For certain ranges in composition a mixed amorphous silicate and crystalline forsterite structure is formed, while for others an amorphous-to-amorphous phase transition is observed, with crystallisation occurring at much higher temperatures. The implications of these findings for the interpretation of observational spectra, particularly at 10 and 20 um, will be discussed.

  1. Dispersion and orientation of zeolite ZSM-5 crystallites within a fluid catalytic cracking catalyst particle.

    PubMed

    Sprung, Christoph; Weckhuysen, Bert M

    2014-03-24

    Confocal fluorescence microscopy was employed to selectively visualize the dispersion and orientation of zeolite ZSM-5 domains inside a single industrially applied fluid catalytic cracking (FCC) catalyst particle. Large ZSM-5 crystals served as a model system together with the acid-catalyzed fluorostyrene oligomerization reaction to study the interaction of plane-polarized light with these anisotropic zeolite crystals. The distinction between zeolite and binder material, such as alumina, silica, and clay, within an individual FCC particle was achieved by utilizing the anisotropic nature of emitted fluorescence light arising from the entrapped fluorostyrene-derived carbocations inside the zeolite channels. This characterization approach provides a non-invasive way for post-synthesis characterization of an individual FCC catalyst particle in which the size, distribution, orientation, and amount of zeolite ZSM-5 aggregates can be determined. It was found that the amount of detected fluorescence light originating from the stained ZSM-5 aggregates corresponds to about 15?wt?%. Furthermore, a statistical analysis of the emitted fluorescence light indicated that a large number of the ZSM-5 domains appeared in small sizes of about 0.015-0.25??m(2), representing single zeolite crystallites or small aggregates thereof. This observation illustrated a fairly high degree of zeolite dispersion within the FCC binder material. However, the highest amount of crystalline material was aggregated into larger domains (ca. 1-5??m(2)) with more or less similarly oriented zeolite crystallites. It is clear that this visualization approach may serve as a post-synthesis quality control on the dispersion of zeolite ZSM-5 crystallites within FCC particles. PMID:24616006

  2. Quantification of thickness and wrinkling of exfoliated two-dimensional zeolite nanosheets

    NASA Astrophysics Data System (ADS)

    Kumar, Prashant; Agrawal, Kumar Varoon; Tsapatsis, Michael; Mkhoyan, K. Andre

    2015-05-01

    Some two-dimensional (2D) exfoliated zeolites are single- or near single-unit cell thick silicates that can function as molecular sieves. Although they have already found uses as catalysts, adsorbents and membranes precise determination of their thickness and wrinkling is critical as these properties influence their functionality. Here we demonstrate a method to accurately determine the thickness and wrinkles of a 2D zeolite nanosheet by comprehensive 3D mapping of its reciprocal lattice. Since the intensity modulation of a diffraction spot on tilting is a fingerprint of the thickness, and changes in the spot shape are a measure of wrinkling, this mapping is achieved using a large-angle tilt-series of electron diffraction patterns. Application of the method to a 2D zeolite with MFI structure reveals that the exfoliated MFI nanosheet is 1.5 unit cells (3.0 nm) thick and wrinkled anisotropically with up to 0.8 nm average surface roughness.

  3. Interstellar silicate analogs for grain-surface reaction experiments: Gas-phase condensation and characterization of the silicate dust grains

    SciTech Connect

    Sabri, T.; Jger, C.; Gavilan, L.; Lemaire, J. L.; Vidali, G.; Henning, T.

    2014-01-10

    Amorphous, astrophysically relevant silicates were prepared by laser ablation of siliceous targets and subsequent quenching of the evaporated atoms and clusters in a helium/oxygen gas atmosphere. The described gas-phase condensation method can be used to synthesize homogeneous and astrophysically relevant silicates with different compositions ranging from nonstoichiometric magnesium iron silicates to pyroxene- and olivine-type stoichiometry. Analytical tools have been used to characterize the morphology, composition, and spectral properties of the condensates. The nanometer-sized silicate condensates represent a new family of cosmic dust analogs that can generally be used for laboratory studies of cosmic processes related to condensation, processing, and destruction of cosmic dust in different astrophysical environments. The well-characterized silicates comprising amorphous Mg{sub 2}SiO{sub 4} and Fe{sub 2}SiO{sub 4}, as well as the corresponding crystalline silicates forsterite and fayalite, produced by thermal annealing of the amorphous condensates, have been used as real grain surfaces for H{sub 2} formation experiments. A specifically developed ultra-high vacuum apparatus has been used for the investigation of molecule formation experiments. The results of these molecular formation experiments on differently structured Mg{sub 2}SiO{sub 4} and Fe{sub 2}SiO{sub 4} described in this paper will be the topic of the next paper of this series.

  4. The safety of synthetic zeolites used in detergents.

    PubMed

    Fruijtier-Plloth, Claudia

    2009-01-01

    Synthetic zeolites are replacing phosphates as builders in laundry detergents; workers and consumers may, therefore, increasingly be exposed to these materials and it is important to assess their safety. This article puts mechanistic, toxicological and exposure data into context for a safety assessment. Zeolites are hygroscopic compounds with ion-exchanging properties. They may partially decompose under acidic conditions such as in the stomach releasing sodium ions, silicic acid and aluminum salts. The intact molecule is not bioavailable after oral intake or exposure through the dermal and inhalational routes. Under current conditions of manufacture and use, no systemic toxicity is to be expected from neither the intact molecule nor the degradation products; a significant effect on the bioavailability of other compounds is not likely. Zeolites may cause local irritation. It is, therefore, important to minimise occupational exposure. The co-operation of detergent manufacturers with the manufacturers of washing machines is necessary to find the right balance between environmental aspects such as energy and water savings and the occurrence of detergent residues on textiles due to insufficient rinsing. PMID:18563391

  5. Steps toward interstellar silicate mineralogy. V. Thermal Evolution of Amorphous Magnesium Silicates and Silica

    NASA Astrophysics Data System (ADS)

    Fabian, D.; Jger, C.; Henning, Th.; Dorschner, J.; Mutschke, H.

    2000-12-01

    The thermally induced amorphous-to-crystalline transition has been studied for bulk sheets and micrometre-sized particles of magnesium silicate glass (MgSiO3), nanometre-sized amorphous magnesium silicate (MgSiO3 and Mg2SiO4 smokes) and amorphous silica particles (SiO2). Silicate glass was produced by the shock-quenching of melts. Samples of nanometre-sized smoke particles have been obtained by the laser ablation technique. Both the MgSiO3 and the Mg2SiO4 smokes have been found to consist of two particle species; particles of smaller size ranging in diametre from 10 nm to about 100 nm and bigger size ranging from a few 100 nm to almost 3 micrometres in diametre. Nanometre-sized particles have been shown to be depleted in magnesium whereas the micrometre-sized particles were found to be enriched in Mg. Generally, the particles are composed of nonstoichiometric magnesium silicates with compositions varying even inside of the particles. Frequently, the particles contained internal voids that are assumed to have been formed by thermal shrinkage or outgassing of the particles' interior during cooling. Annealing at 1000 K transformed the magnesium silicate smokes into crystalline forsterite (c-Mg2SiO4), tridymite (a crystalline modification of SiO2) and amorphous silica (a-SiO2) according to the initial Mg/Si-ratio of the smoke. Crystallization took place within a few hours for the Mg2SiO4 smoke and within one day for the MgSiO3 smoke. The MgSiO3 glass evolved more slowly because crystallization started at the sample surface. It has been annealed at temperatures ranging from 1000 to 1165 K. In contrast to the smoke samples, MgSiO3 glass crystallized as orthoenstatite (MgSiO3). Only after 50 hours of annealing at 1000 K, weak indications of forsterite and tridymite formation have been found in the X-ray diffraction spectra. At a temperature of 1000 K, amorphous silica nanoparticles showed distinctly lower rates of thermal evolution compared with the magnesium silicates. At 1220 K, the timescale of crystallization of a-SiO2 into cristobalite and tridymite amounts to 4.5 h. From the experiments, crystallization parameters have been obtained: activation energy and velocity of crystal growth. The spectra shown in this study will be made publically available in the electronic database (http://www.astro.uni-jena.de).

  6. Template-free nanosized faujasite-type zeolites

    NASA Astrophysics Data System (ADS)

    Awala, Hussein; Gilson, Jean-Pierre; Retoux, Richard; Boullay, Philippe; Goupil, Jean-Michel; Valtchev, Valentin; Mintova, Svetlana

    2015-04-01

    Nanosized faujasite (FAU) crystals have great potential as catalysts or adsorbents to more efficiently process present and forthcoming synthetic and renewable feedstocks in oil refining, petrochemistry and fine chemistry. Here, we report the rational design of template-free nanosized FAU zeolites with exceptional properties, including extremely small crystallites (10-15 nm) with a narrow particle size distribution, high crystalline yields (above 80%), micropore volumes (0.30 cm3 g-1) comparable to their conventional counterparts (micrometre-sized crystals), Si/Al ratios adjustable between 1.1 and 2.1 (zeolites X or Y) and excellent thermal stability leading to superior catalytic performance in the dealkylation of a bulky molecule, 1,3,5-triisopropylbenzene, probing sites mostly located on the external surface of the nanosized crystals. Another important feature is their excellent colloidal stability, which facilitates a uniform dispersion on supports for applications in catalysis, sorption and thin-to-thick coatings.

  7. Laser control of zeolite nucleation.

    PubMed

    Navarro, Marta; Mayoral, Alvaro; Mateo, Ester; Lahoz, Ruth; de la Fuente, Germán F; Coronas, Joaquín

    2012-02-01

    Precursor solutions for the synthesis of zeolites are irradiated by means of a Nd-YAG laser. These solutions are subsequently submitted to a hydrothermal treatment and the results analyzed by X-ray diffraction and electron microscopy. Laser irradiation promotes the formation of silica nanoparticles that nucleate into zeolite (silicalite-1), following a hydrothermal treatment. The average crystal size (in the 0.6-3.6 μm range) of the zeolite exponentially decreases as a function of laser irradiation time. In addition, a longer irradiation time results in a narrower crystal size distribution. PMID:22266775

  8. Clinoptilolite zeolitized tuff from Central Alborz Range, North Iran

    NASA Astrophysics Data System (ADS)

    Taghipour, Batoul

    2010-05-01

    Zeolites are hydrated alumino-silicates of the alkaline and alkaline earth cations, principally sodium, potassium, calcium, and magnesium (Iijima 1980; Hay 1981). Zeolites occur principally in unmetamorphosed sedimentary rocks and are particularly widespread in volcani-clastic strata (Hay, 1978). Clinoptilolite is a natural zeolite of the heulandite group with the simplified formula of (Na, K)6 Si30 Al6 O72 .nH2. It is the most common natural zeolite found mainly in sedimentary rocks of volcanic origin. Alborz zone is one of the important geological divisions in Iran. This zone is restricted to Kopeh dagh zone in North & Central Iranian zone in South and is a region of active deformation within the broad Arabian-Eurasia collision zone (Allen et al. 2003). The zeolitized green tuff belt from Central Alborz which introduce here are made of volcanoclastic sequence of Karaj Formation. This belt is about 40 km long along Alborz Range and is Eocene in age. Zeolites and associated minerals of this altered vitric tuff studied. Zeolitization took place in some beds of Karaj Formations, with average range of 3 to 300 meters thickness. There are several gypsum lenses which interbed with a widespread green tuff succession in the studied area. On the basis of chemical composition these tuffs are in the range of acid to intermediate volcanic rocks. Also magmatic affinity is calc-alkaline and geological setting of the area belongs to volcanic arc granitoid. Petrographic data has shown that various shape and size of shard glass are the main component of tuffs. Based on the field studies, detail microscopy, XRD and electron microprobe analysis (EMPA), the following main minerals are determined: Clinoptilolite+montmorillonite+crystobalite. Clinoptilolite and smectite are predominant minerals in all altered samples. Concerning the Si/Al ratio of 40 point analyses of glass shards the Alborz tuff has clinoptilolite composition. Otherwise the chemical composition of altered shard glass is very similar to clinoptilolite structural formula. By using medium results of chemical data the structural formula for Firuzkuh clinoptilolite is as follow: Si 29.91 Al 6.01 Fe2+ 951 Mg2+ 0.393 Ca 0.222 Na 3.162 K 1.422 Paleogeographic conditions have provided a marginal shallow seawater environment which has been filled by volcanoclastics sequence. In Eocene the zeolitization occur as layers which are confined stratigraphically, it seems this process that took place only in preferred tuffaceous horizons which enriched by shard glass. So the term staratabound can be used for this type zeolitization. In altered tuffs there are a close relationship between clinoptiloite and montmorilonite in some deposits. Alborz range, there was an occasionally marine environment (existence of marine microfossils) with humid climate (remnants of plants in some points). Transformation process (glass zeolite + smectite) provides a further silica contribution to the system, which finally in supersaturation and decreasing pH favors the precipitation of silica in altered tuff. This may have occurred when ground water flow become to mix with saline water to lowering the pH.

  9. Calcium silicate insulation structure

    DOEpatents

    Kollie, Thomas G.; Lauf, Robert J.

    1995-01-01

    An insulative structure including a powder-filled evacuated casing utilizes a quantity of finely divided synthetic calcium silicate having a relatively high surface area. The resultant structure-provides superior thermal insulating characteristics over a broad temperature range and is particularly well-suited as a panel for a refrigerator or freezer or the insulative barrier for a cooler or a insulated bottle.

  10. Zeolites as catalysts in organic reactions: condensation of aldehydes with benzene derivatives

    SciTech Connect

    Climent, M.J.; Corma, A.; Garcia, H.; Primo, J. )

    1991-07-01

    Reactions of four aldehydes with five aromatic compounds have been carried out on a series of USY zeolites with unit cell size in the 24.56 to 24.25-{angstrom} range. Conversion decreased in the order formaldehyde > benzaldehyde > acetaldehyde > propionaldehyde and also in the series anisole > toluene > benzene > chlorobenzene. For aliphatic aldehydes a mixture of ortho-ortho, ortho-para, and para-para diarylmethanes was obtained. USY zeolites show a higher para-directing selectivity than AlCl{sub 3}. Benzaldehyde reacted with benzene derivatives to afford mixtures of diaryl- and triarylmethanes. Formation of ditolyl- and dianisylmethanes in the corresponding reactions indicated that bulky triarylmethanes, once formed inside the crystalline framework, have strong diffusional limitations to get out of the zeolite cavities and can undergo subsequent protolytic cleavage. A decrease in the activity of the zeolite to catalyze hydride transfer reactions lead to a decrease on the diphenylmethane yield. Finally, diphenylmethane appears as a primary product indicating that a series of consecutive reactions such as the formation of diarylcarbinols followed by protonation, water elimination, and hydride abstraction are taking place inside the pores of the zeolite before the real primary product comes out from the zeolite.

  11. Ultrastrong Alkali-Resisting Lanthanide-Zeolites Assembled by [Ln60] Nanocages.

    PubMed

    Dong, Jie; Cui, Ping; Shi, Peng-Fei; Cheng, Peng; Zhao, Bin

    2015-12-30

    Zeolites, as one of the most important porous materials, are most widely utilized in sorbents, catalysis, and ion-exchange fields. However, the multi-functional lanthanide-zeolites constructed exclusively by lanthanide ions and oxygen linkers are to our knowledge unknown hitherto. Herein, we, for the first time, report the unique structure and multifunctions of lanthanide zeolites (1·Gd, 1·Tb, 1·Dy), featuring 60 nuclear [Ln60] nanocages as building blocks and ultrastrong alkali-resisting. These compounds possess extremely high stability and still retain single crystallinity after treatment in boiling water, 0.1 M HCl, and 20 M NaOH aqueous solutions. Magnetic studies revealed 1·Gd has large magnetocaloric effect with -ΔSm(max) = 66.5 J kg(-1) K(-1), falling among the largest values known to date. Importantly, these lanthanide-zeolites themselves can efficiently catalyze the cycloaddition of CO2 with epoxides under mild conditions. Our finding extends the conventional zeolites to lanthanide counterparts, opening a new space for seeking novel and/or multifunctional zeolites. PMID:26653619

  12. The growth of zeolites A, X and mordenite in space

    NASA Technical Reports Server (NTRS)

    Sacco, Albert, Jr.; Bac, N.; Coker, E. N.; Dixon, A. G.; Warzywoda, J.; Thompson, R. W.

    1994-01-01

    Zeolites are a class of crystalline aluminosilicate materials that form the backbone of the chemical process industry worldwide. They are used primarily as adsorbents and catalysts and support to a significant extent the positive balance of trade realized by the chemical industry in the United States (around $19 billion in 1991). The magnitude of their efforts can be appreciated when one realizes that since their introduction as 'cracking catalysts' in the early 1960's, they have saved the equivalent of 60 percent of the total oil production from Alaska's North Slope. Thus the performance of zeolite catalysts can have a profound effect on the U.S. economy. It is estimated that a 1 percent increase in yield of the gasoline fraction per barrel of oil would represent a savings of 22 million barrels of crude oil per year, representing a reduction of $400 million in the United States' balance of payments. Thus any activity that results in improvement in zeolite catalyst performance is of significant scientific and industrial interest. In addition, due to their 'stability,' uniformity, and, within limits, their 'engineerable' structures, zeolites are being tested as potential adsorbents to purify gases and liquids at the parts-per-billion levels needed in today's electronic, biomedical, and biotechnology industries and for the environment. Other exotic applications, such as host materials for quantum-confined semiconductor atomic arrays, are also being investigated. Because of the importance of this class of material, extensive efforts have been made to characterize their structures and to understand their nucleation and growth mechanisms, so as to be able to custom-make zeolites for a desired application. To date, both the nucleation mechanics and chemistry (such as what are the 'key' nutrients) are, as yet, still unknown for many, if not all, systems. The problem is compounded because there is usually a 'gel' phase present that is assumed to control the degree of supersaturation, and this gel undergoes a continuous 'polymerization' type reaction during nucleation and growth. Generally, for structure characterization and diffusion studies, which are useful in evaluating zeolites for improving yield in petroleum refining as well as for many of the proposed new applications (e.g., catalytic membranes, molecular electronics, chemical sensors) large zeolites (greater than 100 to 1000 times normal size) with minimum lattice defects are desired. Presently, the lack of understanding of zeolite nucleation and growth precludes the custom design of zeolites for these or other uses. It was hypothesized that the microgravity levels achieved in an orbiting spacecraft could help to isolate the possible effects of natural convection (which affects defect formation) and minimize sedimentation, which occurs since zeolites are twice as dense as the solution from which they are formed. This was expected to promote larger crystals by allowing growing crystals a longer residence time in a high-concentration nutrient field. Thus it was hypothesized that the microgravity environment of Earth orbit would allow the growth of large, more defect-free zeolite crystals in high yield.

  13. Hydrocracking process using zeolite beta

    SciTech Connect

    Angevine, P.J.; Mitchell, K.M.; Oleck, S.M.; Shih, S.S.

    1986-09-16

    A process is described for the hydrocracking and dewaxing of a petroleum fraction comprising waxy components boiling above 345/sup 0/C., which comprises passing the fraction over a hydrocracking catalyst comprising zeolite beta and a matrix material in the presence of hydrogen and under hydrocracking conditions, the proportion of zeolite beta in the hydrocracking catalyst increasing in the direction in which the fraction is passed.

  14. Copper-containing zeolite catalysts

    DOEpatents

    Price, Geoffrey L. (Baton Rouge, LA); Kanazirev, Vladislav (Sofia, BG)

    1996-01-01

    A catalyst useful in the conversion of nitrogen oxides or in the synthesis of nitriles or imines from amines, formed by preparing an intimate mechanical mixture of a copper (II)-containing species, such as CuO or CuCl.sub.2, or elemental copper, with a zeolite having a pore mouth comprising 10 oxygen atoms, such as ZSM-5, converting the elemental copper or copper (II) to copper (I), and driving the copper (I) into the zeolite.

  15. Copper-containing zeolite catalysts

    DOEpatents

    Price, G.L.; Kanazirev, V.

    1996-12-10

    A catalyst useful in the conversion of nitrogen oxides or in the synthesis of nitriles or imines from amines, is formed by preparing an intimate mechanical mixture of a copper (II)-containing species, such as CuO or CuCl{sub 2}, or elemental copper, with a zeolite having a pore mouth comprising 10 oxygen atoms, such as ZSM-5, converting the elemental copper or copper (II) to copper (I), and driving the copper (I) into the zeolite.

  16. IMPROVED CATALYSTS FOR HEAVY OIL UPGRADING BASED ON ZEOLITE Y NANOPARTICLES ENCAPSULATED IN STABLE NANOPOROUS HOSTS

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2004-06-30

    The focus of this project is to improve the catalytic performance of zeolite Y for heavy petroleum hydrocracking by synthesizing nanoparticles of the zeolite ({approx}20-30 nm) inside nanoporous silicate or aluminosilicate hosts of similar pore diameters. The encapsulated zeolite nanoparticles are expected to possess pores of reduced diffusional path lengths, hence hydrocarbon substrates will diffuse in, are converted and the products quickly diffused out. This is expected to prevent over-reaction, hence minimizing pore blockage and active sites deactivation. In this phase of the project, research activities were focused on refining procedures to: (a) improve the synthesis of ordered, high surface area nanoporous silica, such as SBA-15, with expanded pore size using trimethylbenzene as additive to the parent SBA-15 synthesis mixture; and (b) reduce the particle size of zeolite Y such that they can be effectively incorporated into the nanoporous silicas. The synthesis of high surface ordered nanoporous silica containing enlarged pores of diameter of 25 nm (larger than the standard size of 8.4 nm) using trimethylbenzene as a pore size expander was accomplished. The synthesis of zeolite Y nanoparticles with median pore size of approximately 50 nm (smaller than the 80 nm typically obtained with TMAOH) using combined TMABr/TMAOH as organic additives was also accomplished.

  17. IMPROVED CATALYSTS FOR HEAVY OIL UPGRADING BASED ON ZEOLITE Y NANOPARTICLES ENCAPSULATED STABLE NANOPOROUS HOST

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2005-03-21

    The objectives of this project are to synthesis nanocrystals of highly acidic zeolite Y, encapsulate them within the channels of mesoporous (nanoporous) silicates or nanoporous organosilicates and evaluate the ''zeolite Y/Nanoporous host'' composites as catalysts for the upgrading of heavy petroleum feedstocks. Our results to date are summarized as follows. The synthesis of high surface ordered nanoporous silica of expanded pore diameter of 25 nm (larger than the standard size of 8.4 nm) using trimethylbenzene as a pore size expander was accomplished. The synthesis of zeolite Y nanoparticles with median pore size of approximately 50 nm (smaller than the 80 nm typically obtained with TMAOH) using combined TMABr/TMAOH as organic additives was also accomplished. The successful synthesis of zeoliteY/Nanoporous host composite materials by sequential combination of zeolite precursors and nanoporous material precursor mixtures was implied based on results from various characterization techniques such as X-Ray diffraction, infrared spectra, thermal analysis, porosimetry data. The resulting materials showed pore sizes up to 11 nm, and infrared band at 570 cm{sup -1} suggesting the presence of both phases. Work in the immediate future will be focused on the following three areas: (1) Further characterization of all-silica and aluminosilicate mesoporous materials with expanded pore sizes up to 30 nm will continue; (2) Research efforts to reduce the average particle size of zeolite nanoparticles down to 35-30 nm will continue; (3) Further synthesis of polymer-SBA15 nanocomposites will be conducted by changing the amount and chemistry of the zeolitic precursors added; and (4) Investigation on the catalytic properties of the materials using probe catalytic reactions (such as cumene cracking), followed by catalytic testing for heavy oil conversion.

  18. Small-angle neutron scattering studies of the template-mediated crystallization of ZSM-5 type zeolite

    SciTech Connect

    Iton, L.E.; Brun, T.O.; Epperson, J.E. . Materials Science and Technology Div.); Trouw, F. . Intense Pulsed Neutron Source Program); White, J.W.; Henderson, S.J. )

    1988-03-01

    Small-angle neutron scattering is a useful new approach to the study of zeolite crystallization from aluminosilicate gels and the action of template molecules. It has been applied to gels for synthesis of zeolite ZSM-5 using tetrapropylammonium ions as templates where the scattering length densities of the gel particles and their texture were determined using contrast variation methods. Gels formulated from soluble silicate incorporate template molecules promptly into an amorphous embryonic'' structure and crystallization ensues via a solid hydrogel transformation mechanism. Gels formulated from colloidal silica show different scattering behavior, and a liquid phase transport mechanism is inferred. 8 refs., 4 figs., 2 tabs.

  19. The Mineralogy of Circumstellar Silicates Preserved in Cometary Dust

    NASA Technical Reports Server (NTRS)

    Keller, L. P.; Messenger, S.

    2010-01-01

    Interplanetary dust particles (IDPs) contain a record of the building blocks of the solar system including presolar grains, molecular cloud material, and materials formed in the early solar nebula. Cometary IDPs have remained relatively unaltered since their accretion because of the lack of parent body thermal and aqueous alteration. We are using coordinated transmission electron microscope (TEM) and ion microprobe studies to establish the origins of the various components within cometary IDPs. Of particular interest is the nature and abundance of presolar silicates in these particles because astronomical observations suggest that crystalline and amorphous silicates are the dominant grain types produced in young main sequence stars and evolved O-rich stars. Five circumstellar grains have been identified including three amorphous silicate grains and two polycrystalline aggregates. All of these grains are between 0.2 and 0.5 micrometers in size. The isotopic compositions of all five presolar silicate grains fall within the range of presolar oxides and silicates, having large (17)O-enrichments and normal (18)O/(16)O ratios (Group 1 grains from AGB and RG stars). The amorphous silicates are chemically heterogeneous and contain nanophase FeNi metal and FeS grains in a Mg-silicate matrix. Two of the amorphous silicate grains are aggregates with subgrains showing variable Mg/Si ratios in chemical maps. The polycrystalline grains show annealed textures (equilibrium grains boundaries, uniform Mg/Fe ratios), and consist of 50-100 nm enstatite and pyrrhotite grains with lesser forsterite. One of the polycrystalline aggregates contains a subgrain of diopside. The polycrystalline aggregates form by subsolidus annealing of amorphous precursors. The bulk compositions of the five grains span a wide range in Mg/Si ratios from 0.4 to 1.2 (avg. 0.86). The average Fe/Si (0.40) and S/Si (0.21) ratios show a much narrower range of values and are approximately 50% of their solar abundances. The latter observation may indicate a decoupling of the silicate and sulfide components in grains that condense in stellar outflows. The amorphous silicate grains described here were not extensively affected by irradiation, sputtering, or thermal processing and may represent relatively pristine circumstellar grains. They are strong candidates for the "dirty silicates" in astronomical observations of circumstellar dust shells. The polycrystalline grains were originally amorphous silicate grains that were likely annealed in the early solar nebula but the processing was not sufficient to erase their anomalous oxygen isotopic compositions.

  20. Optical Properties of Astronomical Silicates with Infrared Techniques (OPASI-T)

    NASA Technical Reports Server (NTRS)

    Rinehart, Stephen

    2010-01-01

    Astronomical dust is observed in a variety of astrophysical environments and plays an important role in radiative processes and chemical evolution in the galaxy. Depending upon the environment, dust can be either carbon-rich or oxygen-rich (silicate grains). Both astronomical observations and ground-based data show that the optical properties of silicates can change dramatically with the crystallinity of the material, and recent laboratory research provides evidence that the optical properties of silicate dust vary as a function of temperature as well. Therefore, correct interpretation of a vast array of astronomical data relies on the understanding of the properties of silicate dust as functions of wavelength, temperature, and crystallinity. The OPASI-T (Optical Properties of Astronomical Silicates with Infrared Techniques) project addresses the need for high quality optical characterization of metal-enriched silicate condensates using a variety of techniques. A combination of both new and established experiments are used to measure the extinction, reflection, and emission properties of amorphous silicates across the infrared (near infrared to millimeter wavelengths), providing a comprehensive data set characterizing the optical parameters of dust samples. We present room temperature measurements and the experimental apparatus to be used to investigate and characterize additional metal-silicate materials.

  1. Silicates in Alien Asteroids

    NASA Technical Reports Server (NTRS)

    2009-01-01

    This plot of data from NASA's Spitzer Space Telescopes shows that asteroid dust around a dead 'white dwarf' star contains silicates a common mineral on Earth. The data were taken primarily by Spitzer's infrared spectrograph, an instrument that breaks light apart into its basic constituents. The yellow dots show averaged data from the spectrograph, while the orange triangles show older data from Spitzer's infrared array camera. The white dwarf is called GD 40.

  2. Selective preparation of zeolite X and A from flyash and its use as catalyst for biodiesel production.

    PubMed

    Volli, Vikranth; Purkait, M K

    2015-10-30

    This work discusses the utilization of flyash for synthesis of heterogeneous catalyst for transesterification. Different types of zeolites were synthesized from alkali fusion followed by hydrothermal treatment of coal flyash as source material. The synthesis conditions were optimized to obtain highly crystalline zeolite based on degree of crystallinity and cation exchange capacity (CEC). The effect of CEC, acid treatment, Si/Al ratio and calcination temperature (800, 900 and 1000 C) on zeolite formation was also studied. Pure, single phase and highly crystalline zeolite was obtained at flyash/NaOH ratio (1:1.2), fusion temperature (550 C), fusion time (1 h), hydrothermal temperature (110 C) and hydrothermal time (12h). The synthesized zeolite was ion-exchanged with potassium and was used as catalyst for transesterification of mustard oil to obtain a maximum conversion of 84.6% with 5 wt% catalyst concentration, 12:1 methanol to oil molar ratio, reaction time of 7 h at 65 C. The catalyst was reused for 3 times with marginal reduction in activity. PMID:25956640

  3. Thermochemistry of Silicates

    NASA Technical Reports Server (NTRS)

    Costa, Gustavo; Jacobson, Nathan

    2015-01-01

    The thermodynamic properties of vapor and condensed phases of silicates are crucial in many fields of science. These quantities address fundamental questions on the formation, stability, transformation, and physical properties of silicate minerals and silicate coating compositions. Here the thermodynamic activities of silica and other species in solid solution have been measured by the analysis of the corresponding high temperature vapors using Knudsen Effusion Mass Spectrometry (KEMS). In first set of experiments KEMS has been used to examine the volatility sequence of species (Fe, SiO, Mg, O2 and O) present in the vapor phase during heating of fosterite-rich olivine (Fo93Fa7) up to 2400 C and to measure the Fe, SiO and Mg activities in its solid solution. The data of fosterite-rich olivine are essential for thermochemical equilibrium models to predict the atmospheric and surface composition of hot, rocky exoplanets (Lava Planets). In the second set of experiments the measured thermodynamic activities of the silica in Y2O3-SiO2 and Yb2O3-SiO2 systems are used to assess their reactivity and degradation recession as environmental barrier coatings (EBCs) in combustion environments (e.g. non-moveable parts of gas turbine engine).

  4. Structural chemistry of anhydrous sodium silicates - a review.

    PubMed

    Kahlenberg, Volker

    2010-01-01

    Sodium silicates are of considerable importance for many fields of inorganic chemistry and applied mineralogy, being either raw materials for synthesis or already finished products. In addition to their industrial relevance they have also been studied intensively because of their interesting physico-chemical properties including high ion-exchange capacity and selectivity or two-dimensional sodium diffusion and conductivity. Furthermore, the structural chemistry of crystalline sodium silicates offers the crystallographer challenging tasks such as polytypism, polymorphism, temperature and/or pressure-dependent phase transitions, pseudo-symmetry, complex twinning phenomena as well as incommensurately modulated structures. Many of these structural problems have been solved only recently, although in some cases they have been known for several decades. This article will provide an overview on the structurally characterized sodium silicates and their fascinating crystallochemical characteristics. PMID:21138160

  5. Effect of mechanical treatment on the silicate lattice of kaolinite

    NASA Astrophysics Data System (ADS)

    Zulumyan, N. H.; Papakhchyan, L. R.; Isahakyan, A. R.; Beglaryan, H. A.; Aloyan, S. G.

    2012-12-01

    X-ray diffraction, differential thermal and chemical analysis have been used to investigate the effect of mechanical treatment on the crystalline lattice of kaolinite. It was established that mechanical treatment leads to amorphization of the mineral and the release of hydroxyl water, but the continuity of kaolinite's silicate lattice remains intact despite certain deformations, and the phase transformations of the mineral thus occur without any noticeable change in temperature.

  6. Entrapping of Cs and Sr in heat-treated zeolite matrices

    NASA Astrophysics Data System (ADS)

    Liguori, B.; Caputo, D.; Iucolano, F.; Aprea, P.; de Gennaro, B.

    2013-04-01

    A solidification-stabilization procedure aiming at immobilizing Cs+ and Sr2+, two of the radioactive species more frequently present in nuclear power plant wastewaters, was successfully tested. Both cations were simultaneously exchanged by a blend of two zeolites, a phillipsite-rich tuff, selective for Cs+, and a synthetic zeolite Linde-type A, selective for Sr2+. The contaminated material was then heat treated up to 1200 C with the result of safely immobilizing both cations, as demonstrated by leaching estimation with three different procedures. X-ray studies of the single cation-loaded zeolites or mixture of them helped to interpret the immobilization mechanism, involving cation trapping in chemically stable crystalline/amorphous matrices formed as a result of firing.

  7. Cobalt and nickel supported on HY zeolite: Synthesis, characterization and catalytic properties

    SciTech Connect

    Garrido Pedrosa, Anne M. . E-mail: annemgp@yahoo.com; Souza, Marcelo J.B.; Melo, Dulce M.A.; Araujo, Antonio S.

    2006-06-15

    Bifunctional catalysts consisting of cobalt and nickel supported on HY zeolite were synthesized by solvent excess impregnation and characterized by X-ray diffraction, Fourier-transformed infrared spectroscopy, scanning electron microscopy, atomic absorption spectroscopy, thermogravimetric analysis and nitrogen adsorption. The profiles of metal reduction on zeolite were obtained by temperature-programmed reduction. The catalytic properties of the bifunctional catalysts were verified by n-hexane hydroconversion. X-ray diffraction and microstructural analyses showed the presence of crystalline phases in HY zeolite and in samples after impregnation. A decrease in the micropore surface area was observed by nitrogen adsorption experiments and attributed to a reduction in the accessibility to micropores. The catalysts showed catalytic activity in the hydroconversion of n-hexane with selectivity to branched hydrocarbons. Such catalytic activity was related to the acid and metallic properties of the bifunctional catalysts used.

  8. Formation of cobalt hydrotalcite by cation exchange of Co2+-substitued zeolite X

    NASA Astrophysics Data System (ADS)

    Jeong, H. Y.; Lee, K.

    2013-12-01

    Zeolite has been utilized to sequester heavy metals and nuclides due to the high cation exchange capacity. However, once-immobilized cations by zeolite tend to be re-exchanged by other cations (Ca2+, Mg2+, Na+, etc) present in groundwater. Thus, it is important to understand the mechanism associated with re-exchange reactions to predict the environmental fate and behavior of the metal cations sequestered by zeolite. In this study, we performed a series of cation exchange experiments using Co2+-substituted zeolite X (Co-X) in concentrated CaCl2 solutions. The radioactive isotope of cobalt (60Co2+), commonly found in low-to-intermediate level nuclear wastes, undergoes radioactive decay, likely altering the physicochemical properties of zeolite by generating heat and irradiation. To simulate such effects, Co-X was thermally treated at 400 and 600oC before re-exchange experiments. At the higher treatment temperature, the re-exchanged amount of Co2+ in Co-X by Ca2+ was found to decrease. According to X-ray diffraction, the re-exchange led to little change in the zeolite crystallinity for thermally untreated samples, but the significantly decreased crystallinity was noted for re-exchanged, thermally treated samples. Nonetheless, 27Al MAS NMR spectra of all re-exchanged samples revealed that the peaks corresponding to 4-fold coordinated Al became broader with their position shifting as a result of the re-exchange, suggesting that the re-exchange caused a short-range order structural distortion for both thermally untreated and treated samples. Also, Co-K edge X-ray absorption spectroscopy (XAS) was employed to examine the mechanism(s) involved in the re-exchange. By comparison of XAS spectra between re-exchanged samples and model compounds, Co2+ was likely to be either present as an extraframwork cation within zeolite or incorporated into a cobalt hydrotalcite (Co6Al2(OH)16(An-)2/n where An- is an interlayer anion) phase. The relative contribution of an extraframwork Co2+ versus cobalt hydrotalcite in re-exchanged samples was determined using the least squares fitting of EXAFS spectra. Formation of cobalt hydrotalcite became greater with the increasing treatment temperature. Taken together, thermally-induced structural distortion of zeolite enhanced the dealumination of zeolite and the subsequent formation of cobalt hydrotalcite.

  9. Parameters influencing zeolite incorporation in PDMS membranes

    SciTech Connect

    Vankelecom, I.F.J.; Scheppers, E.; Heus, R.; Uytterhoeven, J.B. )

    1994-11-24

    The incorporation of several types of zeolite in PDMS membranes is studied, by measuring the tensile strength, xylene sorption, and density of the membranes. The zeolite is shown to be involved in the cross-linking of the membrane. The interaction between the PDMS matrix and the zeolites results in reinforced membranes in the case of zeolite Y. The parameters influencing the dispersion of the zeolite in the membrane are investigated, as well as several aspects of the preparation method. Finally, the idea of cross-linking is applied to explain the results of water/ethanol pervaporation. 25 refs., 9 figs., 4 tabs.

  10. Zeolites with Continuously Tuneable Porosity**

    PubMed Central

    Wheatley, Paul S; Chlubn-Eliov, Pavla; Greer, Heather; Zhou, Wuzong; Seymour, Valerie R; Dawson, Daniel M; Ashbrook, Sharon E; Pinar, Ana B; McCusker, Lynne B; Opanasenko, Maksym; ?ejka, Ji?; Morris, Russell E

    2014-01-01

    Zeolites are important materials whose utility in industry depends on the nature of their porous structure. Control over microporosity is therefore a vitally important target. Unfortunately, traditional methods for controlling porosity, in particular the use of organic structure-directing agents, are relatively coarse and provide almost no opportunity to tune the porosity as required. Here we show how zeolites with a continuously tuneable surface area and micropore volume over a wide range can be prepared. This means that a particular surface area or micropore volume can be precisely tuned. The range of porosity we can target covers the whole range of useful zeolite porosity: from small pores consisting of 8-rings all the way to extra-large pores consisting of 14-rings. PMID:25284344

  11. A new approach to evaluate natural zeolite ability to sorb lead (Pb) from aqueous solutions

    NASA Astrophysics Data System (ADS)

    Drosos, Evangelos I. P.; Karapanagioti, Hrissi K.

    2013-04-01

    Lead (Pb) is a hazardous pollutant commonly found in aquatic ecosystems. Among several methods available, the addition of sorbent amendments to soils or sediments is attractive, since its application is relatively simple, while it can also be cost effective when a low cost and re-usable sorbent is used; e.g. natural zeolites. Zeolites are crystalline aluminosilicates with a three-dimensional structure composed of a set of cavities occupied by large ions and water molecules. Zeolites can accommodate a wide variety of cations, such as Na+, K+, Ca2+, Mg2+, which are rather loosely held and can readily be exchanged for others in an aqueous solution. Natural zeolites are capable of removing cations, such as lead, from aqueous solutions by ion exchange. There is a wide variation in the cation exchange capacity (CEC) of natural zeolites because of the different nature of various zeolites cage structures, natural structural defects, adsorbed ions, and their associated gangue minerals. Naturally occurring zeolites are rarely pure and are contaminated to varying degrees by other minerals, such as clays and feldspars, metals, quartz, or other zeolites as well. These impurities affect the CEC even for samples originated from the same region but from a different source. CEC of the material increases with decreasing impurity content. Potentially exchangeable ions in such impurities do not necessarily participate in ion exchange mechanism, while, in some cases, impurities may additionally block the access to active sites. For zeoliferous rocks having the same percentage of a zeolitic phase, the CEC increases with decreasing Si/Al ratio, as the more Si ions are substituted by Al ions, the more negative the valence of the matrix becomes. Sodium seems to be the most effective exchangeable ion for lead. On the contrary, it is unlikely that the potassium content of the zeolite would be substituted. A pretreatment with high concentration solutions of Na, such as 2 M NaCl, can significantly improve zeolite CEC by bringing the material to near homoionic form. pH and temperature are the critical parameters for using natural zeolites as sorbents. Zeolites should not be used in extremely acidic, neither in extremely basic pH conditions, except for very short times. The exchange of Pb, requires low solution pH, to avoid precipitation but not too low because the H+ are competitive ions for ion exchange; as a result the zeolite CEC related to Pb removal may be downgraded. If pH enters the basic range (e.g. pH>8), more aquatic complexes with lower positive valence than those prevailing in lower pH are produced; these complexes are less attracted by the negative charged zeolitic matrix. Pb uptake is favored at higher temperatures as ion exchange (including the diffusion of exchangeable ions inside the material and the medium, and vice versa) is an endothermic process. With the increase of temperature there is a decrease in hydration of all available exchangeable cations that eases the movement within the channels of the solid matrix. Additionally, the mobility of the potassium ions, present in the zeolitic material, also increases with the temperature resulting in enhanced CEC.

  12. Suspending Zeolite Particles In Tanks

    SciTech Connect

    Poirier, M.R.

    1999-01-19

    The Savannah River Site (SRS) is in the process of removing waste (sludge and salt cake) from million gallon waste tanks. The current practice for removing waste from the tanks is adding water, agitating the tanks with long shaft vertical centrifugal pumps, and pumping the sludge/salt solution from the tank to downstream treatment processes. This practice has left sludge heels ({tilde} 30,000 gallons) in the bottom of the tanks. SRS is evaluating shrouded axial impeller mixers for removing the sludge heels in the waste tanks. The authors conducted a test program to determine mixer requirements for suspending sludge heels using the shrouded axial impeller mixers. The tests were performed with zeolite in scaled tanks which have diameters of 1.5, 6.0, and 18.75 feet. The mixer speeds required to suspend zeolite particles were measured at each scale. The data were analyzed with various scaling methods to compare their ability to describe the suspension of insoluble solids with the mixers and to apply the data to a full-scale waste tank. The impact of changes in particle properties and operating parameters was also evaluated. The conclusions of the work are: Scaling of the suspension of fast settling zeolite particles was best described by the constant power per unit volume method. Increasing the zeolite particle concentration increased the required mixer power needed to suspend the particles. Decreasing the zeolite particle size from 0.7 mm ? 0.3 mm decreased the required mixer power needed to suspend the particles. Increasing the number of mixers in the tank decreased the required mixer power needed to suspend the particles. A velocity of 1.6 ft/sec two inches above the tank bottom is needed to suspend zeolite particles.

  13. Structural Characterization of Zeolite Beta

    NASA Astrophysics Data System (ADS)

    Newsam, J. M.; Treacy, M. M. J.; Koetsier, W. T.; de Gruyter, C. B.

    1988-12-01

    Crystallographic faulting in zeolite structures affects both the catalytic and sorption properties, and can greatly complicate attempts at structural characterization. A near extreme example of stacking disorder is provided by zeolite beta, a large pore, high-silica zeolite that was first reported in 1967. We describe here the determination of the framework structure of zeolite beta, using primarily high-resolution electron microscopy, electron diffraction, computer-assisted modelling and powder X-ray diffraction. Zeolite beta can be regarded as a highly intergrown hybrid of two distinct, but closely related structures that both have fully three-dimensional pore systems with 12-rings as the minimum constricting apertures. One end member, polymorph A, forms an enantiomorphic pair, space group symmetries P4_122 and P4_322, with a = 1.25 nm, c = 2.66 nm. Polymorph B is achiral, space group C2/c with a = 1.76 nm, b = 1.78 nm, c = 1.44 nm, ? = 114.5^circ. Both structures are constructed from the same centrosymmetric tertiary building unit (TBU), arranged in layers that, successively, interconnect in either a left- (L) or a right- (R) handed fashion. Polymorph A represents an uninterrupted sequence of RRRR... (or LLLL...) stacking. Polymorph B has an alternating RLRL... stacking sequence. The TBU has no intrinsic preference for either mode of connection, enabling both to occur with almost equal probability in zeolite beta, giving rise to a near random extent of interplanar stacking faults and, to a lesser extent, intraplanar defects terminated by hydroxyl groups. The faulting does not significantly affect the accessible pore volume, but influences the tortuosity of the pore connectivity along the c direction. The high stacking fault densities give rise to complex powder X-ray diffraction (PXD) patterns for zeolite beta materials that comprise both sharp and broad features. By exploiting recursive relations between possible stacking sequences, PXD patterns have been calculated as a function of faulting probability. Reasonable agreement with observed PXD profiles is observed for a ca. 60% faulting probability in the chiral stacking sequence, suggesting a slight preference for polymorph B. The framework building units observed in zeolite beta can also be used to construct other frameworks.

  14. New insights into the complex architecture of siliceous copepod teeth.

    PubMed

    Michels, Jan; Vogt, Jrgen; Simon, Paul; Gorb, Stanislav N

    2015-06-01

    Copepods belong to the dominant marine zooplankton taxa and play an important role in particle and energy fluxes of the marine water column. Their mandibular gnathobases possess tooth-like structures, so-called teeth. In species feeding on large proportions of diatoms these teeth often contain silica, which is very probably the result of a coevolution with the siliceous diatom frustules. Detailed knowledge of the morphology and composition of the siliceous teeth is essential for understanding their functioning and their significance in the context of feeding interactions between copepods and diatoms. Based on analyses of the gnathobases of the Antarctic copepod Rhincalanus gigas, the present study clearly shows, for the first time, that the silica in the siliceous teeth features large proportions of crystalline silica that is consistent with the mineral ?-cristobalite and is doped with aluminium. The siliceous structures have internal chitinous fibre networks, which are assumed to serve as scaffolds during the silicification process. The compact siliceous teeth of R. gigas are accompanied by structures with large proportions of the elastic protein resilin, likely reducing the mechanical damage of the teeth when the copepods feed on diatoms with very stable frustules. The results indicate that the coevolution with diatom frustules has resulted in gnathobases exhibiting highly sophisticated composite structures. PMID:25622509

  15. 21 CFR 573.260 - Calcium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Calcium silicate. 573.260 Section 573.260 Food and... Listing § 573.260 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely used as an anticaking agent in animal feed, provided that the amount of calcium silicate does...

  16. 21 CFR 573.260 - Calcium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Calcium silicate. 573.260 Section 573.260 Food and... Listing § 573.260 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely used as an anticaking agent in animal feed, provided that the amount of calcium silicate does...

  17. 21 CFR 573.260 - Calcium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Calcium silicate. 573.260 Section 573.260 Food and... Listing § 573.260 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely used as an anticaking agent in animal feed, provided that the amount of calcium silicate does...

  18. 21 CFR 573.260 - Calcium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium silicate. 573.260 Section 573.260 Food and... Listing § 573.260 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely used as an anticaking agent in animal feed, provided that the amount of calcium silicate does...

  19. 21 CFR 573.260 - Calcium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Calcium silicate. 573.260 Section 573.260 Food and... Listing § 573.260 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely used as an anticaking agent in animal feed, provided that the amount of calcium silicate does...

  20. Spectroscopic signatures of nitrogen-substituted zeolites.

    PubMed

    Hammond, Karl D; Dogan, Fulya; Tompsett, Geoffrey A; Agarwal, Vishal; Conner, W Curtis; Grey, Clare P; Auerbach, Scott M

    2008-11-12

    Nanoporous acid catalysts such as zeolites form the backbone of catalytic technologies for refining petroleum. With the promise of a biomass economy, new catalyst systems will have to be discovered, making shape-selective base catalysts especially important because of the high oxygen content in biomass-derived feedstocks. Strongly basic zeolites are attractive candidates, but such materials are notoriously difficult to make due to the strong inherent acidity of aluminosilicates. Several research groups have endeavored to produce strongly basic zeolites by treating zeolites with amines, but to date there is no compelling evidence that nitrogen is incorporated into zeolite frameworks. In this communication, we detail synthesis, NMR spectroscopy, and quantum mechanical calculations showing that nitrogen adds onto both surface and interior sites while preserving the framework structure of zeolites. This finding is crucial for the rational design of new biomass-refinement catalysts, allowing 50 years of zeolite science to be brought to bear on the catalytic synthesis of biofuels. PMID:18855470

  1. Pockels effect of silicate glass-ceramics: Observation of optical modulation in MachZehnder system

    PubMed Central

    Yamaoka, Kazuki; Takahashi, Yoshihiro; Yamazaki, Yoshiki; Terakado, Nobuaki; Miyazaki, Takamichi; Fujiwara, Takumi

    2015-01-01

    Silicate glass has been used for long time because of its advantages from materials viewpoint. In this paper, we report the observation of Pockels effect by MachZehnder interferometer in polycrystalline ceramics made from a ternary silicate glass via crystallization due to heat-treatment, i.e., glass-ceramics. Since the silicate system is employed as the precursor, merits of glass material are fully utilized to fabricate the optical device component, in addition to that of functional crystalline material, leading us to provide an electro-optic device, which is introducible into glass-fiber network. PMID:26184722

  2. Pockels effect of silicate glass-ceramics: Observation of optical modulation in Mach-Zehnder system.

    PubMed

    Yamaoka, Kazuki; Takahashi, Yoshihiro; Yamazaki, Yoshiki; Terakado, Nobuaki; Miyazaki, Takamichi; Fujiwara, Takumi

    2015-01-01

    Silicate glass has been used for long time because of its advantages from material's viewpoint. In this paper, we report the observation of Pockels effect by Mach-Zehnder interferometer in polycrystalline ceramics made from a ternary silicate glass via crystallization due to heat-treatment, i.e., glass-ceramics. Since the silicate system is employed as the precursor, merits of glass material are fully utilized to fabricate the optical device component, in addition to that of functional crystalline material, leading us to provide an electro-optic device, which is introducible into glass-fiber network. PMID:26184722

  3. Pockels effect of silicate glass-ceramics: Observation of optical modulation in Mach-Zehnder system

    NASA Astrophysics Data System (ADS)

    Yamaoka, Kazuki; Takahashi, Yoshihiro; Yamazaki, Yoshiki; Terakado, Nobuaki; Miyazaki, Takamichi; Fujiwara, Takumi

    2015-07-01

    Silicate glass has been used for long time because of its advantages from materials viewpoint. In this paper, we report the observation of Pockels effect by Mach-Zehnder interferometer in polycrystalline ceramics made from a ternary silicate glass via crystallization due to heat-treatment, i.e., glass-ceramics. Since the silicate system is employed as the precursor, merits of glass material are fully utilized to fabricate the optical device component, in addition to that of functional crystalline material, leading us to provide an electro-optic device, which is introducible into glass-fiber network.

  4. IMPROVED CATALYSTS FOR HEAVY OIL UPGRADING BASED ON ZEOLITE Y NANOPARTICLES ENCAPSULATED IN STABLE NANOPOROUS HOST

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2005-03-31

    The objectives of this project are to synthesis nanocrystals of highly acidic zeolite Y, encapsulate them within the channels of mesoporous (nanoporous) silicates or nanoporous organosilicates and evaluate the ''zeolite Y/Nanoporous host'' composites as catalysts for the upgrading of heavy petroleum feedstocks. Our results to date are summarized as follows. The synthesis of high surface ordered nanoporous silica of expanded pore diameter of 25 nm (larger than the standard size of 8.4 nm) using trimethylbenzene as a pore size expander was accomplished. The synthesis of zeolite Y nanoparticles with median pore size of approximately 50 nm (smaller than the 80 nm typically obtained with TMAOH) using combined TMABr/TMAOH as organic additives was also accomplished. The successful synthesis of zeoliteY/Nanoporous host composite materials by sequential combination of zeolite precursors and nanoporous material precursor mixtures was implied based on results from various characterization techniques such as X-Ray diffraction, infrared spectra, thermal analysis, porosimetry data. The resulting materials showed pore sizes up to 11 nm, and infrared band at 570 cm{sup -1} suggesting the presence of both phases. New results indicated that good quality highly ordered nanoporous silica host can be synthesized in the presence of zeolite Y seed precursor depending on the amount of precursor added. Preliminary research on the catalytic performance of the materials is underway. Probe acid catalyzed reactions, such as the cracking of cumene is currently being conducted. Work in the immediate future will be focused on the following three areas: (1) Further characterization of all-silica and aluminosilicate mesoporous materials with expanded pore sizes up to 30 nm will continue; (2) Research efforts to reduce the average particle size of zeolite nanoparticles down to 35-30 nm will continue; (3) Further synthesis of ZeoliteY/Nanoporous host composite catalysts of improved structural and physicochemical characteristics will be conducted by changing the amount and chemistry of the zeolitic precursors added; and (4) Investigation on the catalytic properties of the materials using probe catalytic reactions (such as cumene cracking), followed by catalytic testing for heavy oil conversion.

  5. Enhanced selectivity of zeolites by controlled carbon deposition

    DOEpatents

    Nenoff, Tina M.; Thoma, Steven G.; Kartin, Mutlu

    2006-05-09

    A method for carbonizing a zeolite comprises depositing a carbon coating on the zeolite pores by flowing an inert carrier gas stream containing isoprene through a regenerated zeolite at elevated temperature. The carbonized zeolite is useful for the separation of light hydrocarbon mixtures due to size exclusion and the differential adsorption properties of the carbonized zeolite.

  6. A novel concept for photovoltaic cells: clusters of titanium dioxide encapsulated within zeolites as photoactive semiconductors.

    PubMed

    Alvaro, Mercedes; Carbonell, Esther; Atienzar, Pedro; García, Hermenegildo

    2006-09-11

    Discrete clusters of TiO(2) (of only a few titanium atoms) are prepared within the internal micropore space of zeolite Y (4.8 wt % Ti loading) and characterized by Raman spectroscopy (rutile- and anatase-like structures), electron microscopy combined with elemental analyses (coincident Si and Ti spatial distribution), and X-ray diffraction (minor zeolite crystallinity decrease). The parent TiO(2)@Y sample is modified either by adsorption of acid-organic compounds (benzoic and 4-aminobenzoic acids or catechol) or by nitrogen doping. After modification, the optical UV/Vis spectrum of the parent TiO(2)@Y (onset of the absorption band at wavelengths <300 nm and bandgap of 4.2 eV) changes, and the appearance of new bands expanding to the visible region is observed. In contrast to the inactive zeolite Y matrix, all the zeolite-encapsulated TiO(2) species exhibit a photovoltaic response. The influence of the I(2)/I(3) (-) concentration in the electrolyte solution on the temporal profile of the photovoltage clearly shows that I(2)/I(3) (-) is also a suitable carrier for the positive charge in zeolite-based photovoltaic devices. The photocurrent response and the efficiency of the photovoltaic cell based on zeolite-encapsulated TiO(2) materials depend on the nature of the organic modifier and on the N-doping. The most efficient photovoltaic cell is that based on N-doped TiO(2)@Y, which exhibits a V(OC) (voltage at open circuit) of 270 mV, an I(SC) of 5.8 muA (current at short circuit), and a fill factor (FF) of 0.4. Although these values are low compared to current dye-sensitized TiO(2) solar cells, our findings could open up a promise for a stimulating research on the photovoltaic activity of zeolite-based host-guest solids. PMID:16921574

  7. Investigation of structure formation mechanism of a mesoporous ZSM-5 zeolite by mesoscopic simulation

    NASA Astrophysics Data System (ADS)

    Ren, Yanqun; Liu, Baoyu; Kiryutina, Tatyana; Xi, Hongxia; Qian, Yu

    2015-02-01

    Amphiphilic surfactant molecules have a profound influence in directing zeolite crystallization, while the self-assembly process between the functionalized surfactant and aluminosilicate species is the key factor in determining the structure of zeolites. However, such a complex process is extremely difficult to be characterized experimentally. A novel mesoporous ZSM-5 zeolite with hexagonal mesostructures and crystalline microporous frameworks has been synthesized in our previous work. In present research, dissipative particle dynamics (DPD), a mesoscopic simulation method, has been used to investigate the self-assembly process of a surfactant/tetraethylorthosilicate (TEOS)/water system in order to explore the structure formation mechanism of a mesoporous ZSM-5 zeolite. The simulation results show that under a certain composition, the specially designed bifunctional triquaternary ammonium-type surfactant and TEOS can form spherical core-shell micelles. The core (inner section) of a spherical micelle is occupied by hydrophobic beads, while the shell (outer section) is formed by hydrophilic beads. Besides, an ordered, uniform mesophase can be formed under a constant shear rate and transformed into mesoscale structure. The simulation results are consistent with the corresponding experimental results. Overall, the DPD simulation is a valuable tool to investigate the porogenic mechanism of surfactants. The present approach may open a window for investigating the formation mechanism of mesoporous zeolites that involves the surfactant-driven synthesis process.

  8. Selective Chlorination of Toluene to p-Chlorotoluene Catalyzed by Nanosized Zeolite K-L Catalysts.

    PubMed

    Zhu, Xiaoyan; Fu, Yujun; Yin, Hengbo; Feng, Yonghai; Shen, Lingqin; Wang, Aili; Li, Jitai; Ni, Wenxiu; Xie, Xulan

    2015-08-01

    Nanosized zeolite K-L catalysts were synthesized by the hydrothermal method starting from silica sol and potassium aluminate. The crystallinities of the zeolite K-L catalysts increased with increasing the SiO2/Al2O3 mole ratio of reaction solution and prolonging the autoclaving time. Nanosized and well-dispersed zeolite K-L catalysts were synthesized when the SiO2/Al2O3 mole ratio was more than 26:1. Well-crystallized and nanosized zeolite K-L catalysts showed high catalytic activity for the chlorination of toluene to p-chlorotoluene. When the nanosized zeolite K-L catalyst was synthesized with the SiO2/Al2O3 mole ratio of 31:1 at the autoclaving temperature of 150 C for 96 h, the selectivities of p-chlorotoluene and o-chlorotoluene were 76.2% and 20.0%, respectively, at the complete conversion of toluene. PMID:26369216

  9. Examination of the solventlike nature of zeolites based on a solvatochromic indicator

    SciTech Connect

    Dutta, P.K.; Turbeville, W. )

    1991-05-16

    Zeolites are crystalline aluminosilicates with cages and channel systems that can host a variety of organic transformations. This intracrystalline space is akin to a solvent, and description of this space in terms of solventlike properties is appropriate. The concept of solvatochromic indicators has been successfully used to define the physicochemical properties of organic solvents. In this study, the authors have investigated the electronic and Raman spectroscopy of the molecule N-(2-hydroxybenzylidene)aniline and established a quantitative correlation between the spectral intensities of the benzenoid and zwitterionic forms of this molecule and the {alpha}-value of various hydroxylic solvents. The {alpha} value is a measure of the hydrogen bond donor ability of the solvent. This correlation has been used to establish an {alpha} value scale for a series of faujasitic zeolites with varying Si/Al ratios. It was found that the {alpha} value of the zeolite increased with Si/Al ratio to reach a maximum around 7.8, followed by a decrease at higher Si/Al ratios. Since Na{sup +}-exchanged zeolites were examined in all cases, the interaction of the anil molecule in its zwitterionic form with Lewis acids (Na{sup +}) and bases (oxygen of the framework) was considered to be responsible for its formation. The Si/Al ratio of the framework determines the acid-base character of the zeolite and is reflected in a quantitative manner by the {alpha} value determined in this study.

  10. A novel magnetic 4A zeolite adsorbent synthesised from kaolinite type pyrite cinder (KTPC)

    NASA Astrophysics Data System (ADS)

    Wang, Weiqing; Feng, Qiming; Liu, Kun; Zhang, Guofan; Liu, Jing; Huang, Yang

    2015-01-01

    As a solid waste, kaolinite type pyrite cinder (KTPC) is a special pyrite cinder, its mineral components include metakaolin and magnetite, and the chemical compositions of these minerals include SiO2, Al2O3, FeO and Fe2O3. In this study, a novel magnetic 4A zeolite adsorbent was synthesised from KTPC using the hydrothermal method, and the optimum hydrothermal synthesis conditions were investigated using X-ray diffraction (XRD) and by determining the specific surface area (SSA) and the saturated cation exchange adsorption capacity (SCEAC) to Cs+. Under the optimum hydrothermal synthesis conditions, the magnetic 4A zeolite adsorbent can be synthesised with high crystallinity, and the SSA and SCEAC to Cs+ are 24.49 m2/g and 106.63 mg/g, respectively. The further characterisations of pore size distribution, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), thermogravimetry-derivative thermogravimetry-differential thermal analysis (TG-DTG-DTA), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM) were performed. The results revealed that magnetic particles are coated onto the zeolite surface and further form magnetic aggregates, and the existing magnetic particles in KTPC do not change their crystal structure and do not affect the synthesis of the 4A zeolite. In addition, the synthesised 4A zeolite adsorbent can be used as a magnetic adsorbent in wastewater treatment with high magnetic sensitivity and is thermally stable up to approximately 900 C.

  11. A comparison of the amorphization of zeolitic imidazolate frameworks (ZIFs) and aluminosilicate zeolites by ball-milling.

    PubMed

    Baxter, Emma F; Bennett, Thomas D; Cairns, Andrew B; Brownbill, Nick J; Goodwin, Andrew L; Keen, David A; Chater, Philip A; Blanc, Frédéric; Cheetham, Anthony K

    2016-03-01

    X-ray diffraction has been used to investigate the kinetics of amorphization through ball-milling at 20 Hz, for five zeolitic imidazolate frameworks (ZIFs) - ZIF-8, ZIF-4, ZIF-zni, BIF-1-Li and CdIF-1. We find that the rates of amorphization for the zinc-containing ZIFs increase with increasing solvent accessible volume (SAV) in the sequence ZIF-8 > ZIF-4 > ZIF-zni. The Li-B analogue of the dense ZIF-zni amorphizes more slowly than the corresponding zinc phase, with the behaviour showing a correlation with their relative bulk moduli and SAVs. The cadmium analogue of ZIF-8 (CdIF-1) amorphizes more rapidly than the zinc counterpart, which we ascribe primarily to its relatively weak M-N bonds as well as the higher SAV. The results for the ZIFs are compared to three classical zeolites - Na-X, Na-Y and ZSM-5 - with these taking up to four times longer to amorphize. The presence of adsorbed solvent in the pores is found to render both ZIF and zeolite frameworks more resistant to amorphization. X-ray total scattering measurements show that amorphous ZIF-zni is structurally indistinguishable from amorphous ZIF-4 with both structures retaining the same short-range order that is present in their crystalline precursors. By contrast, both X-ray total scattering measurements and (113)Cd NMR measurements point to changes in the local environment of amorphous CdIF-1 compared with its crystalline CdIF-1 precursor. PMID:26575842

  12. Hydrogen Selective Exfoliated Zeolite Membranes

    SciTech Connect

    Tsapatsis, Michael; Daoutidis, Prodromos; Elyassi, Bahman; Lima, Fernando; Iyer, Aparna; Agrawal, Kumar; Sabnis, Sanket

    2015-04-06

    The objective of this project was to develop and evaluate an innovative membrane technology at process conditions that would be representative of Integrated Gasification Combined Cycle (IGCC) advanced power generation with pre-combustion capture of carbon dioxide (CO2). This research focused on hydrogen (H2)-selective zeolite membranes that could be utilized to separate conditioned syngas into H2-rich and CO2-rich components. Both experiments and process design and optimization calculations were performed to evaluate the concept of ultra-thin membranes made from zeolites nanosheets. In this work, efforts in the laboratory were made to tackle two fundamental challenges in application of zeolite membranes in harsh industrial environments, namely, membrane thickness and membrane stability. Conventional zeolite membranes have thicknesses in the micron range, limiting their performance. In this research, we developed a method for fabrication of ultimately thin zeolite membranes based on zeolite nanosheets. A range of layered zeolites (MWW, RWR, NSI structure types) suitable for hydrogen separation was successfully exfoliated to their constituent nanosheets. Further, membranes were made from one of these zeolites, MWW, to demonstrate the potential of this group of materials. Moreover, long-term steam stability of these zeolites (up to 6 months) was investigated in high concentrations of steam (35 mol% and 95 mole%), high pressure (10 barg), and high temperatures (350 °C and 600 °C) relevant to conditions of water-gas-shift and steam methane reforming reactions. It was found that certain nanosheets are stable, and that stability depends on the concentration of structural defects. Additionally, models that represent a water-gas-shift (WGS) membrane reactor equipped with the zeolite membrane were developed for systems studies. These studies had the aim of analyzing the effect of the membrane reactor integration into IGCC plants in terms of performance and economic aspects of the plants. Specifically, simulation and design optimization studies were performed using the developed stand-alone membrane reactor models to identify the membrane selectivity and permeance characteristics necessary to achieve desired targets of CO2 capture and H2 recovery, as well as guide the selection of the optimal reactor design that minimizes the membrane cost as a function of its surface area required. The isothermal membrane reactor model was also integrated into IGCC system models using both the MATLAB and Aspen software platforms and techno-economic analyses of the integrated plants have been carried out to evaluate the feasibility of replacing current technologies for pre-combustion capture by the proposed novel approach in terms of satisfying stream constraints and achieving the DOE target goal of 90% CO2 capture. The results of the performed analyses based on present value of annuity calculations showed break even costs for the membrane reactor within the feasible range for membrane fabrication. However, the predicted membrane performance used in these simulations exceeded the performance achieved experimentally. Therefore, further work is required to improve membrane performance.

  13. Multiple-quantum NMR studies of spin clusters in liquid crystals and zeolites

    SciTech Connect

    Pearson, J. . Dept. of Chemistry Lawrence Berkeley Lab., CA )

    1991-07-01

    This work will describe the use of MQ NMR to study spin clusters in anisotropic materials. A technique known as multiple-quantum spin counting was used to determine average spin cluster sizes liquid crystalline materials and in faujacitic zeolites containing aromatic hydrocarbons. The first half of the thesis will describe MQ NMR and the MQ spin counting technique, and the second half of the thesis will describe the actual experiments and their results.

  14. DIRECT LABORATORY ANALYSIS OF SILICATE STARDUST FROM RED GIANT STARS

    SciTech Connect

    Vollmer, Christian; Hoppe, Peter; Brenker, Frank E.

    2009-07-20

    We performed combined focused ion beam/transmission electron microscopy studies to investigate the chemistry and structure of eight presolar silicate grains that were previously detected by NanoSIMS oxygen isotope mapping of the carbonaceous chondrite Acfer 094. The analyzed presolar silicates belong to the O isotope Groups I/II ({sup 17}O-enriched and {sup 18}O-depleted) and therefore come from 1-2.5 M{sub sun} asymptotic giant branch stars of close-to-solar or slightly lower-than-solar metallicity. Three grains are amorphous, Mg-rich, and show a variable, but more pyroxene-like composition. Most probably, these grains have formed under circumstellar low-temperature conditions below the crystallization temperature. Three grains are Fe-bearing glasses similar to the 'glass with embedded metal and sulfides' (GEMS) grains found in interplanetary dust particles. However, two of the meteorite GEMS grains from this study lack comparatively large ({approx}>20 nm) Fe-rich inclusions and have sulfur contents <1 at.%, which is different than observed for the majority of GEMS grains. These grains likely condensed under strong non-equilibrium conditions from an Si-enriched gas. One olivine is characterized by a crystalline core and an amorphous, more Fe-rich rim, which is probably the result of interstellar medium sputtering combined with Mg removal. The detection of another olivine with a relatively high Fe content (Mg no. 0.9) shows that circumstellar crystalline silicates are more Fe-rich than astrophysical models usually suggest. The overall predominance of olivine among the crystalline silicate stardust population compared to pyroxene indicates preferential formation or survival of this type of mineral. As pyroxene is indeed detected in circumstellar outflows, it remains to be seen how this result is compatible with astrophysical observations and experimental data.

  15. Crystalline and Crystalline International Disposal Activities

    SciTech Connect

    Viswanathan, Hari S.; Chu, Shaoping; Reimus, Paul William; Makedonska, Nataliia; Hyman, Jeffrey De'Haven; Karra, Satish; Dittrich, Timothy M.

    2015-12-21

    This report presents the results of work conducted between September 2014 and July 2015 at Los Alamos National Laboratory in the crystalline disposal and crystalline international disposal work packages of the Used Fuel Disposition Campaign (UFDC) for DOE-NE’s Fuel Cycle Research and Development program.

  16. UTILITY OF ZEOLITES IN HAZARDOUS METAL REMOVAL FROM WATER

    EPA Science Inventory

    Zeolites are well known for their ion exchange, adsorption and acid catalysis properties. Different inorganic pollutants have been removed from water at room temperature by using synthetic zeolites. Zeolite Faujasite Y has been used to remove inorganic pollutants including arseni...

  17. A Model for the Dust Envelope of the Silicate Carbon Star IRAS 09425-6040

    NASA Astrophysics Data System (ADS)

    Suh, Kyung-Won

    2016-03-01

    IRAS 09425-6040 (I09425) is a silicate carbon star with conspicuous crystalline silicate and water-ice features and emission excesses in the far-infrared and millimeter (mm) wavelength ranges. To understand properties of the dust envelope of I09425, we propose a physical model based on the observations and known properties of asymptotic giant branch stars and dust. We perform radiative transfer model calculations using multiple dust shells and disks with various dust species. We compare the model results with the observed spectral energy distribution (SED) acquired with different telescopes. We find that the physical model for I09425 using multiple shells of carbon and silicate dust and multiple disks of amorphous and crystalline silicates reproduces the observed SED fairly well. This object looks to have detached cold O-rich (silicate and water-ice) dust shells, which could be remnants of the recent chemical transition from O to C and an inner C-rich dust shell. A long-lived thin disk of very large silicate grains can reproduce the emission excess in the mm wavelength band and a recently formed thick disk of crystalline silicates can reproduce the prominent emission features in the spectral range 8–45 μm. The highly crystallized silicates could be recently formed by high temperature annealing due to the last O-rich superwind just before the chemical transition of the central star. I09425 could be a rare object that has the remnants of past O-rich stellar winds in the outer shells as well as in the circumbinary disks.

  18. Analyses of Cometary Silicate Crystals: DDA Spectral Modeling of Forsterite

    NASA Technical Reports Server (NTRS)

    Wooden, Diane

    2012-01-01

    Comets are the Solar System's deep freezers of gases, ices, and particulates that were present in the outer protoplanetary disk. Where comet nuclei accreted was so cold that CO ice (approximately 50K) and other supervolatile ices like ethane (C2H2) were preserved. However, comets also accreted high temperature minerals: silicate crystals that either condensed (greater than or equal to 1400 K) or that were annealed from amorphous (glassy) silicates (greater than 850-1000 K). By their rarity in the interstellar medium, cometary crystalline silicates are thought to be grains that formed in the inner disk and were then radially transported out to the cold and ice-rich regimes near Neptune. The questions that comets can potentially address are: How fast, how far, and over what duration were crystals that formed in the inner disk transported out to the comet-forming region(s)? In comets, the mass fractions of silicates that are crystalline, f_cryst, translate to benchmarks for protoplanetary disk radial transport models. The infamous comet Hale-Bopp has crystalline fractions of over 55%. The values for cometary crystalline mass fractions, however, are derived assuming that the mineralogy assessed for the submicron to micron-sized portion of the size distribution represents the compositional makeup of all larger grains in the coma. Models for fitting cometary SEDs make this assumption because models can only fit the observed features with submicron to micron-sized discrete crystals. On the other hand, larger (0.1-100 micrometer radii) porous grains composed of amorphous silicates and amorphous carbon can be easily computed with mixed medium theory wherein vacuum mixed into a spherical particle mimics a porous aggregate. If crystalline silicates are mixed in, the models completely fail to match the observations. Moreover, models for a size distribution of discrete crystalline forsterite grains commonly employs the CDE computational method for ellipsoidal platelets (c:a:b=8.14x8.14xl in shape with geometrical factors of x:y:z=1:1:10, Fabian et al. 2001; Harker et al. 2007). Alternatively, models for forsterite employ statistical methods like the Distribution of Hollow Spheres (Min et al. 2008; Oliveira et al. 2011) or Gaussian Random Spheres (GRS) or RGF (Gielen et al. 200S). Pancakes, hollow spheres, or GRS shapes similar to wheat sheaf crystal habit (e.g., Volten et al. 2001; Veihelmann et al. 2006), however, do not have the sharp edges, flat faces, and vertices seen in images of cometary crystals in interplanetary dust particles (IDPs) or in Stardust samples. Cometary forsterite crystals often have equant or tabular crystal habit (J. Bradley). To simulate cometary crystals, we have computed absorption efficiencies of forsterite using the Discrete Dipole Approximation (DDA) DDSCAT code on NAS supercomputers. We compute thermal models that employ a size distribution of discrete irregularly shaped forsterite crystals (nonspherical shapes with faces and vertices) to explore how crystal shape affects the shape and wavelength positions of the forsterite spectral features and to explore whether cometary crystal shapes support either condensation or annealing scenarios (Lindsay et al. 2012a, b). We find forsterite crystal shapes that best-fit comet Hale-Bopp are tetrahedron, bricks or brick platelets, essentially equant or tabular (Lindsay et al. 2012a,b), commensurate with high temperature condensation experiments (Kobatake et al. 2008). We also have computed porous aggregates with crystal monomers and find that the crystal resonances are amplified. i.e., the crystalline fraction is lower in the aggregate than is derived by fitting a linear mix of spectral features from discrete subcomponents, and the crystal resonances 'appear' to be from larger crystals (Wooden et al. 2012). These results may indicate that the crystalline mass fraction in comets with comae dominated by aggregates may be lower than deduced by popular methods that only emoy ensembles of discrete crystals.

  19. Synthesis, Structure, and Carbon Dioxide Capture Properties of Zeolitic Imidazolate Frameworks

    SciTech Connect

    Phan, Anh; Doonan, Christian J; Uribe-Romo, Fernando J; Knobler, Carolyn B; O'Keeffe, Michael; Yaghi, Omar M

    2010-01-19

    Zeolites are one of humanitys most important synthetic products. These aluminosilicate-based materials represent a large segment of the global economy. Indeed, the value of zeolites used in petroleum refining as catalysts and in detergents as water softeners is estimated at $350 billion per year. A major current goal in zeolite chemistry is to create a structure in which metal ions and functionalizable organic units make up an integral part of the framework. Such a structure, by virtue of the flexibility with which metal ions and organic moieties can be varied, is viewed as a key to further improving zeolite properties and accessing new applications. Recently, it was recognized that the Si?O?Si preferred angle in zeolites (145) is coincident with that of the bridging angle in the M?Im?M fragment (where M is Zn or Co and Im is imidazolate), and therefore it should be possible to make new zeolitic imidazolate frameworks (ZIFs) with topologies based on those of tetrahedral zeolites. This idea was successful and proved to be quite fruitful; within the last 5 years over 90 new ZIF structures have been reported. The recent application of high-throughput synthesis and characterization of ZIFs has expanded this structure space significantly: it is now possible to make ZIFs with topologies previously unknown in zeolites, in addition to mimicking known structures. In this Account, we describe the general preparation of crystalline ZIFs, discussing the methods that have been developed to create and analyze the variety of materials afforded. We include a comprehensive list of all known ZIFs, including structure, topology, and pore metrics. We also examine how complexity might be introduced into new structures, highlighting how link?link interactions might be exploited to effect particular cage sizes, create polarity variations between pores, or adjust framework robustness, for example. The chemical and thermal stability of ZIFs permit many applications, such as the capture of CO{sub 2} and its selective separation from industrially relevant gas mixtures. Currently, ZIFs are the best porous materials for the selective capture of CO{sub 2}; furthermore, they show exceptionally high capacity for CO{sub 2} among adsorbents operating by physisorption. The stability of ZIFs has also enabled organic transformations to be carried out on the crystals, yielding covalently functionalized isoreticular structures wherein the topology, crystallinity, and porosity of the ZIF structure are maintained throughout the reaction process. These reactions, being carried out on macroscopic crystals that behave as single molecules, have enabled the realization of the chemists dream of using crystals as molecules, opening the way for the application of the extensive library of organic reactions to the functionalization of useful extended porous structures.

  20. Replica exchange reactive molecular dynamics simulations of initial reactions in zeolite synthesis.

    PubMed

    Jing, Zhifeng; Xin, Liang; Sun, Huai

    2015-10-14

    Molecular simulation is a promising tool for the study of zeolite formation. However, sufficient sampling remains a grand challenge for the practical use of molecular simulation for this purpose. Here, we investigate the initial stage of zeolite synthesis under realistic conditions by using the replica-exchange method and the ReaxFF reactive force field. After a total simulation time of 480 ns, both energetic and structural properties approach convergence. Analyses of data collected at 600 K show that the inorganic structure directing agent NaOH promotes the aggregation of silicate, the formation of branched Si atoms and the formation of 5-membered rings. With the trajectories collected simultaneously at different temperatures, the effect of temperature is discussed. PMID:26365615

  1. Spin probes of chemistry in zeolites

    SciTech Connect

    Werst, D.W.; Trifunac, A.D.

    1997-09-01

    Electron spin resonance (EPR) studies in zeolites are reviewed in which radiolysis was used to ionize the zeolite lattice, create reactive intermediates, spin label reaction products and to provide a window onto chemistry and transport of adsorbates and matrix control of chemistry. The review examines reactions of radical cations and the influence of the geometry constraints inside the zeolite, explores how zeolite model systems can be used to learn about energy and charge transfer in solids and illustrates the use of radiolysis and EPR for in situ spectroscopic studies of solid-acid catalysis. The various spin probes created inside the zeolite pores report on properties of the zeolites as well as shed light on radiolytic processes.

  2. The impact of aqueous medium on zeolite framework integrity

    SciTech Connect

    Vjunov, Aleksei; Fulton, John L.; Camaioni, Donald M.; Hu, Jian Z.; Burton, Sarah D.; Arslan, Ilke; Lercher, Johannes A.

    2015-05-12

    Understanding the zeolite framework stability in aqueous phase is crucial to develop stable catalysts. Al K–edge, extended X–ray absorption fine structure and 27Al MAS NMR spectroscopies in combination with DFT calculations have been used to monitor both qualitative and quantitative structural changes of two well–characterized samples with BEA structure. The effects of various properties on stability were explored, including Al concentration, Al distribution, particle size and structural defects. As the samples were degraded by treatment in hot liquid water, the local structure about the Al T–site remained mostly intact, including the Al–O–Si angles and bond distances, while the nano–scale crystalline structure as measured by XRD and TEM was disrupted. The combined data suggest a three–step mechanism in which, initially, the HBEA framework crystallinity decreases via hydrolysis of T–O bonds along polymorph stacking faults and inter–grain boundaries in a mode similar to crack propagation in glass. With prolonged exposure, amorphization occurs via hydrolysis of surface Si–OH groups propagating inward through the zeolite lattice. In parallel, cracks propagate within the crystalline micro–domains along paths through specific T–O–T groups. Authors thank B. W. Arey (PNNL) for HIM measurements, T. Huthwelker for support during Al XAFS measurements at the Swiss Light Source (PSI, Switzerland) and M. Y. Hu (PNNL) for support during NMR experiments. This work was supported by the U. S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. NMR experiments were performed at the Environmental Molecular Science Laboratory, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research, and Physical Science Laboratory both located at Pacific Northwest National Laboratory (PNNL). PNNL is a multi–program national laboratory operated for DOE by Battelle under Contract No. DE–AC05–76RL01830.

  3. Effect of metal loading processes on the stability and thermal transformation of Co{sup 2+}- and Cu{sup 2+}-zeolite Y prepared from Egyptian kaolin

    SciTech Connect

    EL-Mekkawi, Doaa M. Selim, Mohamed M.

    2012-07-15

    This paper aims to assess the effect of the transition metals (TM) loading procedure on the incorporation of Co{sup 2+} and Cu{sup 2+} in zeolite Y, and their relevance to stability of the zeolite, particularly with respect to the thermal transformation to the spinel phases. In this work, zeolite Y prepared from Egyptian kaolin was used. XRF, XRD, TEM, UV/visible absorption measurements, and atomic absorption analyses in addition to the visual observations are recorded. XRF has been used to investigate the materials composition. TEM and XRD indicate the presence of nanoparticle spinel upon the calcination of the TM-zeolites at 1000 Degree-Sign C. In addition to spinel particles, XRD shows the formation of metal oxides, SiO{sub 2} and alumino-silicate phases. According to the transition metal and the cation loading process, different phases were detected. UV/visible absorption measurements and the visual observations are used to determine the experimental condition of the highest spinel content. It has been noticed that the experimental conditions of the metal sorption processes greatly affect the phase transformation. Stability and thermal transformation of zeolite depend on the initial concentration of the transition cation solutions and the number of loading cycles. - Highlights: Black-Right-Pointing-Pointer We study the effects of loading procedure in the incorporation of TM in zeolite Y. Black-Right-Pointing-Pointer Synthetic zeolite Y prepared from Egyptian kaolin has been used. Black-Right-Pointing-Pointer The type of TM affects the stability and thermal transformation of zeolite. Black-Right-Pointing-Pointer Loading processes affect the stability and thermal transformation of zeolite.

  4. Process for preparing silicon substituted zeolite compositions

    SciTech Connect

    Skeels, G.W.

    1991-02-26

    This patent describes the process for substituting silicon into the crystal lattice of zeolites in place of extracted lattice aluminum atoms to achieve zeolite products of higher silicon content. It comprises: providing a starting aluminosilicate zeolite having a framework SiO{sub 2}/Al{sub 2}O{sub 3} molar ratio of at least 2 and pore diameters of at least 3 Angstroms; contacting the starting zeolite at a temperature of 25{degrees} C. to 95{degrees} C. with an aqueous solution of a fluorosilicate salt containing from 0.5 to 1.5 moles per liter of the fluorosilicate salt dissolved therein, the proportions of zeolite and fluorosilicate salt being at least 0.1 moles of salt per 100 grams of anhydrous zeolite; maintaining contact between the zeolite and the salt solution for a period not in excess of 5 hours; removing from contact with the zeolite the liquid medium containing at least 90 percent of the by-product fluoroaluminate salt produced by the reaction of the fluorosilicate salt with the zeolite.

  5. Increased thermal conductivity monolithic zeolite structures

    DOEpatents

    Klett, James (Knoxville, TN); Klett, Lynn (Knoxville, TN); Kaufman, Jonathan (Leonardtown, MD)

    2008-11-25

    A monolith comprises a zeolite, a thermally conductive carbon, and a binder. The zeolite is included in the form of beads, pellets, powders and mixtures thereof. The thermally conductive carbon can be carbon nano-fibers, diamond or graphite which provide thermal conductivities in excess of about 100 W/mK to more than 1,000 W/mK. A method of preparing a zeolite monolith includes the steps of mixing a zeolite dispersion in an aqueous colloidal silica binder with a dispersion of carbon nano-fibers in water followed by dehydration and curing of the binder is given.

  6. Synthesis of ‘unfeasible’ zeolites

    NASA Astrophysics Data System (ADS)

    Mazur, Michal; Wheatley, Paul S.; Navarro, Marta; Roth, Wieslaw J.; Položij, Miroslav; Mayoral, Alvaro; Eliášová, Pavla; Nachtigall, Petr; Čejka, Jiří; Morris, Russell E.

    2016-01-01

    Zeolites are porous aluminosilicate materials that have found applications in many different technologies. However, although simulations suggest that there are millions of possible zeolite topologies, only a little over 200 zeolite frameworks of all compositions are currently known, of which about 50 are pure silica materials. This is known as the zeolite conundrum—why have so few of all the possible structures been made? Several criteria have been formulated to explain why most zeolites are unfeasible synthesis targets. Here we demonstrate the synthesis of two such ‘unfeasible’ zeolites, IPC-9 and IPC-10, through the assembly–disassembly–organization–reassembly mechanism. These new high-silica zeolites have rare characteristics, such as windows that comprise odd-membered rings. Their synthesis opens up the possibility of preparing other zeolites that have not been accessible by traditional solvothermal synthetic methods. We envisage that these findings may lead to a step change in the number and types of zeolites available for future applications.

  7. Silicate pneumoconiosis in hens.

    PubMed

    Roperto, F; Borzacchiello, G; Ungaro, R; Galati, P

    2000-05-01

    Thirteen cases of silicate pneumoconiosis in 3- to 4-year-old hens are described. Ten of the birds were raised in the suburbs of a city near several chalk quarries and two cement-works; the remaining three hens (aged 3 years) had lived in an environment with high particulate pollution from a nearby brick-works in which large amounts of clay were used daily. Silicotic granulomas composed of dust-laden macrophages were scattered over the lungs. They were located mainly in the infundibula and atria of tertiary bronchi and around vessels; more rarely they occurred in the lamina propria mucosae of primary and secondary bronchi. Energy dispersive x-ray microanalysis coupled with both transmission and scanning electron microscopy revealed that the dust was composed mainly of silicon, aluminium, calcium, iron and potassium. Titanium, sulphur, magnesium, zinc, copper and chlorine were also found. It is concluded that animals raised in polluted environmental conditions may serve as an important indicator of risks to human health and pathogenetic mechanisms. Thirteen cases of silicate pneumoconiosis in 3- to 4-year-old hens are described. Ten of the birds were raised in the suburbs of a city near several chalk quarries and two cement-works; the remaining three hens (aged 3 years) had lived in an environment with high particulate pollution from a nearby brick-works in which large amounts of clay were used daily. Silicotic granulomas composed of dust-laden macrophages were scattered over the lungs. They were located mainly in the infundibula and atria of tertiary bronchi and around vessels; more rarely they occurred in the lamina propria mucosae of primary and secondary bronchi. Energy dispersive x-ray microanalysis coupled with both transmission and scanning electron microscopy revealed that the dust was composed mainly of silicon, aluminium, calcium, iron and potassium. Titanium, sulphur, magnesium, zinc, copper and chlorine were also found. It is concluded that animals raised in polluted environmental conditions may serve as an important indicator of risks to human health and pathogenetic mechanisms. PMID:10805978

  8. Microsphere zeolite materials derived from coal fly ash cenospheres as precursors to mineral-like aluminosilicate hosts for 135,137Cs and 90Sr

    NASA Astrophysics Data System (ADS)

    Vereshchagina, Tatiana A.; Vereshchagin, Sergei N.; Shishkina, Nina N.; Vasilieva, Nataly G.; Solovyov, Leonid A.; Anshits, Alexander G.

    2013-06-01

    Hollow microsphere zeolite materials with a bilayered zeolite/glass crystalline shell bearing NaP1 zeolite were synthesized by the hydrothermal treatment of coal fly ash cenospheres (Si/Al = 2.7) in an alkaline medium. Cs+ and/or Sr2+ forms of zeolitized cenospheres with the different Cs+ and/or Sr2+ loading were prepared by the ion exchange from nitrate solutions. The resulted (Cs,Na)P1, (Sr,Na)P1 and (Cs,Sr,Na)P1 bearing microsphere zeolites were converted to glass ceramics by heating at 900-1000 °C. The differential scanning calorimetry and quantitative phase analysis were used to monitor the solid-phase transformation of the initial and ion exchanged zeolite materials. It was established that the final solidified forms of Cs+ and/or Sr2+ are glass-crystalline ceramic materials based on pollucite-nepheline, Sr-feldspar-nepheline and Sr-feldspar-pollucite composites including ˜60 wt.% of the major host phases (pollucite, Sr-feldspar) and 10-20 wt.% of glass. The 137Cs leaching rate of 4.1 × 10-7 g cm-2 day-1 was determined for the pollucite glass-ceramic according to Russian State Standard (GOST) No. 52126 P-2003 (7 day, 25 °C, distilled water).

  9. Analysis of a Sheet Silicate.

    ERIC Educational Resources Information Center

    Adams, J. M.; Evans, S.

    1980-01-01

    Describes a student project in analytical chemistry using sheet silicates. Provides specific information regarding the use of phlogopite in an experiment to analyze samples for silicon, aluminum, magnesium, iron, potassium, and fluoride. (CS)

  10. Ion implantation in silicate glasses

    SciTech Connect

    Arnold, G.W.

    1993-12-01

    This review examines the effects of ion implantation on the physical properties of silicate glasses, the compositional modifications that can be brought about, and the use of metal implants to form colloidal nanosize particles for increasing the nonlinear refractive index.

  11. Molecular silicate and aluminate species in anhydrous and hydrated cements.

    PubMed

    Rawal, Aditya; Smith, Benjamin J; Athens, George L; Edwards, Christopher L; Roberts, Lawrence; Gupta, Vijay; Chmelka, Bradley F

    2010-06-01

    The compositions and molecular structures of anhydrous and hydrated cements are established by using advanced solid-state nuclear magnetic resonance (NMR) spectroscopy methods to distinguish among different molecular species and changes that occur as a result of cement hydration and setting. One- and two-dimensional (2D) solid-state (29)Si and (27)Al magic-angle spinning NMR methodologies, including T(1)-relaxation-time- and chemical-shift-anisotropy-filtered measurements and the use of very high magnetic fields (19 T), allow resonances from different silicate and aluminate moieties to be resolved and assigned in complicated spectra. Single-pulse (29)Si and (27)Al NMR spectra are correlated with X-ray fluorescence results to quantify the different crystalline and disordered silicate and aluminate species in anhydrous and hydrated cements. 2D (29)Si{(1)H} and (27)Al{(1)H} heteronuclear correlation NMR spectra of hydrated cements establish interactions between water and hydroxyl moieties with distinct (27)Al and (29)Si species. The use of a (29)Si T(1)-filter allows anhydrous and hydrated silicate species associated with iron-containing components in the cements to be distinguished, showing that they segregate from calcium silicate and aluminate components during hydration. The different compositions of white Portland and gray oilwell cements are shown to have distinct molecular characteristics that are correlated with their hydration behaviors. PMID:20455533

  12. Experiments on metal-silicate plumes and core formation.

    PubMed

    Olson, Peter; Weeraratne, Dayanthie

    2008-11-28

    Short-lived isotope systematics, mantle siderophile abundances and the power requirements of the geodynamo favour an early and high-temperature core-formation process, in which metals concentrate and partially equilibrate with silicates in a deep magma ocean before descending to the core. We report results of laboratory experiments on liquid metal dynamics in a two-layer stratified viscous fluid, using sucrose solutions to represent the magma ocean and the crystalline, more primitive mantle and liquid gallium to represent the core-forming metals. Single gallium drop experiments and experiments on Rayleigh-Taylor instabilities with gallium layers and gallium mixtures produce metal diapirs that entrain the less viscous upper layer fluid and produce trailing plume conduits in the high-viscosity lower layer. Calculations indicate that viscous dissipation in metal-silicate plumes in the early Earth would result in a large initial core superheat. Our experiments suggest that metal-silicate mantle plumes facilitate high-pressure metal-silicate interaction and may later evolve into buoyant thermal plumes, connecting core formation to ancient hotspot activity on the Earth and possibly on other terrestrial planets. PMID:18826918

  13. 21 CFR 172.410 - Calcium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Calcium silicate. 172.410 Section 172.410 Food and... PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Anticaking Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely used in food in accordance with...

  14. 21 CFR 172.410 - Calcium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be...

  15. 21 CFR 172.410 - Calcium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be...

  16. 21 CFR 172.410 - Calcium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be...

  17. 21 CFR 172.410 - Calcium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be...

  18. Zeolites Remove Sulfur From Fuels

    NASA Technical Reports Server (NTRS)

    Voecks, Gerald E.; Sharma, Pramod K.

    1991-01-01

    Zeolites remove substantial amounts of sulfur compounds from diesel fuel under relatively mild conditions - atmospheric pressure below 300 degrees C. Extracts up to 60 percent of sulfur content of high-sulfur fuel. Applicable to petroleum refineries, natural-gas processors, electric powerplants, and chemical-processing plants. Method simpler and uses considerably lower pressure than current industrial method, hydro-desulfurization. Yields cleaner emissions from combustion of petroleum fuels, and protects catalysts from poisoning by sulfur.

  19. A Site-Isolated Iridium Diethylene Complex Supported on Highly Dealuminated Y Zeolite: Synthesis and Characterization

    SciTech Connect

    Uzun,A.; Bhirud, V.; Kletnieks, P.; Haw, J.; Gates, B.

    2007-01-01

    Highly dealuminated Y zeolite-supported mononuclear iridium complexes with reactive ethylene ligands were synthesized by chemisorption of Ir(C2H4)2(C5H7O2). The resultant structure and its treatment in He, CO, ethylene, and H2 were investigated with infrared (IR) and extended X-ray absorption fine structure (EXAFS) spectroscopies. The IR spectra show that Ir(C2H4)2(C5H7O2) reacted readily with surface OH groups of the zeolite, leading to the removal of C5H7O2 ligands and the formation of supported mononuclear iridium complexes, confirmed by the lack of Ir-Ir contributions in the EXAFS spectra. The EXAFS data show that each Ir atom was bonded to four carbon atoms at an average distance of 2.10 Angstroms, consistent with the presence of two ethylene ligands per Ir atom and in agreement with the IR spectra indicating p-bonded ethylene ligands. The EXAFS data also indicate that each Ir atom was bonded to two oxygen atoms of the zeolite at a distance of 2.15 Angstroms . The supported iridium-ethylene complex reacted with H2 to give ethane, and it also catalyzed ethylene hydrogenation at atmospheric pressure and 294 K. Treatment of the sample in CO led to the formation of Ir(CO)2 complexes bonded to the zeolite. The sharpness of the ?CO bands indicates a high degree of uniformity of these complexes on the support. The iridium-ethylene complex on the crystalline zeolite support is inferred to be one of the most nearly uniform supported metal complex catalysts. The results indicate that it is isostructural with a previously reported rhodium complex on the same zeolite; thus, the results are a start to a family of analogous, structurally well-defined supported metal complex catalysts.

  20. THE BIOCOMPATIBILITY OF MESOPOROUS SILICATES

    PubMed Central

    Hudson, Sarah; Padera, Robert F.; Langer, Robert; Kohane, Daniel S.

    2008-01-01

    Micro- and nano- mesoporous silicate particles are considered potential drug delivery systems because of their ordered pore structures, large surface areas and the ease with which they can be chemically modified. However, few cytotoxicity or biocompatibility studies have been reported, especially when silicates are administered in the quantities necessary to deliver low-potency drugs. The biocompatibility of mesoporous silicates of particle sizes ~ 150 nm, ~ 800 nm and ~ 4 µm and pore sizes of 3 nm, 7 nm and 16 nm respectively are examined here. In vitro, mesoporous silicates showed a significant degree of toxicity at high concentrations with mesothelial cells. Following subcutaneous injection of silicates in rats, the amount of residual material decreased progressively over three months, with good biocompatibility on histology at all time points. In contrast, intra peritoneal and intra venous injections in mice resulted in death or euthanasia. No toxicity was seen with subcutaneous injection of the same particles in mice. Microscopic analysis of the lung tissue of the mice indicates that death may be due to thrombosis. Although local tissue reaction to mesoporous silicates was benign, they caused severe systemic toxicity. This toxicity could be mitigated by modification of the materials. PMID:18675454

  1. Nanocrystalline Zeolites: Synthesis, Mechanism, and Applications

    NASA Astrophysics Data System (ADS)

    Severance, Michael Andrew

    Nanocrystalline zeolite particles are becoming an important material in many technical applications (e.g. zeolite membranes). Synthetic methods that minimize the zeolite crystal diameter, while providing a narrow particle size distribution, are of primary importance in these technical applications. However, there are several limitations to currently existing synthetic routes aimed at producing nanozeolites and zeolite membrane devices. For example, zeolite growth in these contexts typically requires days to weeks at high temperature to crystallize. Despite excellent performance of zeolite membranes in several separation applications, the long synthesis times required undermine any practical application of these technologies. This work focuses on chemical manipulation of zeolite nucleation processes in sol gel systems in effort to address such limitations. The primary findings indicate that careful control of the nucleation stage of a clear zeolite synthesis (optically transparent sol gel) allow the formation of zeolite Y nanocrystals less than 50 nm in diameter with a polydispersity index less than 0.2. Furthermore, chemical perturbations made during the nucleation stage of zeolite Y hydrogel synthesis is shown to accelerate crystal growth by a factor of 3-4, depending on the specific sol gel chemistry. These findings are applied to the nanocrystal seeding and rapid hydrothermal growth of zeolite Y membranes on inexpensive polymeric supports. A novel synthetic method is developed to this end. Also, the chemical and physical properties of monodisperse nanocrystalline zeolite Y synthesized herein are explored by electrochemical impedance spectroscopy. It is found that the particle interface plays an important role in the ionic conductivity of nanocrystalline zeolites in contrast to their larger zeolite counterparts in analogy to other ceramic and metal oxide ion conductors. Finally, the possibility to produce novel organic and inorganic composite systems through zeolite host-guest chemistry is explored. A nanozeolite-silver nanoparticle host-guest system is synthesized and a mechanism describing its evolution is developed. Also, the photochemistry of a colloidal nanozeolite-organic dye host-guest system is explored with ultrafast transient UV-Vis absorption spectroscopy. This allows some of the fastest chemical events to be probed within the host-guest system.

  2. Synthesis and Properties of Nanoparticle Forms Saponite Clay, Cancrinite Zeolite and Phase Mixtures Thereof

    PubMed Central

    Shao, Hua

    2010-01-01

    The low-temperature synthesis (90C) of nanoparticle forms of a pure phase smectic clay (saponite) and zeolite (cancrinite) is reported, along with phase mixtures thereof. A synthesis gel corresponding to the Si:Al:Mg unit cell composition of saponite (3.6:0.40:3.0) and a NaOH/Si ratio of 1.39 affords the pure phase clay with disordered nanolayer stacking. Progressive increases in the NaOH/Si ratio up to a value of 8.33 results in the co-crystallization of first garronite and then cancrinite zeolites with nanolath morphology. The resulting phase mixtures exhibit a compound particulate structure of intertwined saponite nanolayers and cancrinite nanolaths that cannot be formed through physical mixing of the pure phase end members. Under magnesium-free conditions, pure phase cancrinite nanocrystals are formed. The Si/Al ratio of the reaction mixture affects the particle morphology as well as the chemical composition of the cancrinite zeolite. Ordinarily, cancrinite crystallizes with a Si/Al ratio of 1.0, but a silicon-rich form of the zeolite (Si/Al=1.25) is crystallized at low temperature from a silica rich synthesis gel, as evidenced by 29Si NMR spectroscopy and XEDS-TEM. Owing to the exceptionally high external surface areas of the pure phase clay (875 m2/g) and zeolite end members (8.9 - 40 m2/g), as well as their unique mixed phase composites (124 - 329 m2/g), these synthetic derivatives are promising model nanoparticles for studies of the bioavailability of poly-aromatic hydrocarbons immobilized in silicate bearing sediments and soils. PMID:21709774

  3. Physical, Chemical and Structural Evolution of Zeolite-Containing Waste Forms Produced from Metakaolinite and Calcined Sodium Bearing Waste (HLW and/or LLW)

    SciTech Connect

    Grutzeck, Michael W.

    2005-06-27

    Zeolites are extremely versatile. They can adsorb liquids and gases and serve as cation exchange media. They occur in nature as well cemented deposits. The ancient Romans used blocks of zeolitized tuff as a building material. Using zeolites for the management of radioactive waste is not a new idea, but a process by which the zeolites can be made to act as a cementing agent is. Zeolitic materials are relatively easy to synthesize from a wide range of both natural and man-made substances. The process under study is derived from a well known method in which metakaolin (an impure thermally dehydroxylated kaolinite heated to {approx}700 C containing traces of quartz and mica) is mixed with sodium hydroxide (NaOH) and reacted in slurry form (for a day or two) at mildly elevated temperatures. The zeolites form as finely divided powders containing micrometer ({micro}m) sized crystals. However, if the process is changed slightly and only just enough concentrated sodium hydroxide solution is added to the metakaolinite to make a thick crumbly paste and then the paste is compacted and cured under mild hydrothermal conditions (60-200 C), the mixture will form a hard ceramic-like material containing distinct crystalline tectosilicate minerals (zeolites and feldspathoids) imbedded in an X-ray amorphous hydrated sodium aluminosilicate matrix. Due to its lack of porosity and vitreous appearance we have chosen to call this composite a ''hydroceramic''.

  4. Metal/zeolite catalysts of methane dehydroaromatization

    NASA Astrophysics Data System (ADS)

    Mamonov, N. A.; Fadeeva, E. V.; Grigoriev, D. A.; Mikhailov, M. N.; Kustov, Leonid M.; Alkhimov, S. A.

    2013-06-01

    Results of studying methane dehydroaromatization over metal/zeolite catalysts have been reviewed. Special attention has focused on molybdenum catalysts based on HZSM-5 zeolites. The effect of catalyst synthesis and reaction conditions on the catalytic properties of the systems has been scrutinized. Information on the mechanism of the process and the nature of active sites has been reported. The bibliography includes 137 references.

  5. SEQUESTERING MANURE N WITH SYNTHETIC ZEOLITES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Natural zeolites have a long and successful history of agricultural use in Japan and more recently in the U.S. However the price (often > $US500 Mg -1) limits their use in agriculture. Zeolites can be synthesized from fly ash by reaction with sodium hydroxide solutions and low temperature. The proje...

  6. UTILITY OF ZEOLITES IN ARSENIC REMOVAL FROM WATER

    EPA Science Inventory

    Zeolites are well known for their ion exchange and adsorption properties. So far the cation exchanger properties of zeolites have been extensively studied and utilized. The anion exchanger properties of zeolites are less studied. Zeolite Faujasite Y has been used to remove arseni...

  7. Noble metal acidic zeolites for isomerization

    SciTech Connect

    Schweizer, A.E.

    1991-02-12

    This patent describes a method for producing a noble metal containing zeolite catalyst for isomerization of paraffinic hydrocarbons. Contacting a zeolite material selected from the group consisting of acidic fayjasites. LZ-210 faujasites, and mordenite with a noble-metal compound selected from Pt(acetylacetonate){sub 2} and Pd(acetylacetonate){sub 2} for an effective amount of time to incorporate Pt and/or Pd into the pore surface regions of the zeolite, but not to disperse the Pt and/or Pd throughout the entire zeolite; and calcining the so treated zeolite at a temperature from about 250 {degrees} C, to about 600 {degrees} C. for an effective amount of time.

  8. First principles study of the oxygen vacancy formation and the induced defect states in hafnium silicates

    NASA Astrophysics Data System (ADS)

    Chen, Tsung-Ju; Kuo, Chin-Lung

    2012-04-01

    Using first-principles density functional theory calculations, we have investigated the O vacancy formation and the relevant induced defect states in hafnium silicates over a wide range of compositions. The PBE0 hybrid density functional was employed for the analysis of the electronic properties and the charge transition levels of the O vacancy in crystalline HfSiO4 and in amorphous Hf-silicates, respectively. Based on the generated structure models, eight typical kinds of O coordination structures were identified in amorphous Hf-silicates. Our calculated results show that the positions of the induced defect energy levels in the band gap and the formation energies of O vacancy are largely determined by the local structures of the vacancy sites, which appear to be nearly independent of the composition of amorphous Hf-silicates. Our calculations also show that O vacancy can possess the negative-U behavior in crystalline HfSiO4 but not in amorphous Hf-silicates, where most of the O vacancies can simply exhibit the negative-U behavior as in the positive charge states. Given the measured band offset of 3.40 eV between Si and amorphous Hf-silicates, a considerable number of O vacancies were found to prefer to stay in the charge neutral state as the Fermi level lies within the band gap region of Si. Furthermore, due to its relatively higher formation energy, the concentration of O vacancy in Hf-silicates can be much lower than that in m-HfO2 when the Fermi level lies below the midgap region of Si. Accordingly, a significantly reduced flat band voltage shift and less transient threshold voltage instability can be found in Hf-silicates as compared with m-HfO2, which are in good agreement with the recent experimental findings.

  9. [Spectroscopic analysis of the crystallization mechanism of synthesized zeolite with XRD and FTIR approaches].

    PubMed

    Fan, Chun-hui; Ma, Hong-rui; Hua, Li

    2012-04-01

    Zeolites were synthesized from fly ash using modified one-stage method. The changes in cation exchange capacity (CEC) and chemical elements of zeolite were investigated during the synthesis process to reveal the materials and elements transformation in solid-liquid system. The approaches of XRD, SEM and FTIR were used to indicate the crystallization characteristics and mechanism. The zeolite NaP1 was synthesized, and the CEC value reached to the maximum of 135 mmol/100g at 24 h. After the hydrothermal reaction for 12 h, the characteristic peak and metastable crystalline structure of zeolite NaP1 appeared, then the hydroxy sodalite products formed at 48 h. The crystallization process was the result of materials transformation: the elements of fly ash released into the liquid system for the melting effect of alkali solution, and the solid system played the role of skeleton in crystallization process, being the "source" and the "sink" of the reaction, respectively, and the achievements presented the crystallization mechanism of liquid-phase and solid-phase transformation. PMID:22715798

  10. Dealumination of hexagonal (EMT)/cubic (FAU) zeolite intergrowth materials: A SEM and HRTEM study

    SciTech Connect

    Ohsuna, Tetsu; Watanabe, Denjiro; Terasaki, Osamu; Anderson, M.W.; Carr, S.W.

    1994-12-01

    The aim of this paper is to describe the effects of mild dealumination of the end members (FAU, EMT) and intergrowths produced using crown ethers on the nature of the resultant zeolite. The end members and intergrowths were prepared as described previously and dealuminated according to the following procedure. The intergrowth was prepared from a mixture of crown ethers; 66% 18-crown-6 and 33% 15-crown-5 to give an ordered intergrowth. The zeolites were first calcined to remove the crown ether template (600{degree}C, flowing air, 16 h) and then exchanged with ammonium ions. The zeolite (6 g) was slurried in ammonium acetate solution (450 cm{sup 3}, 0.8 M), and to this was added slowly 15.6 cm{sup 3} of ammonium hexafluorosilicate solution (0.5 M). The mixture was stirred at 75{degree}C for 3 h. The zeolite was collected and carefully washed with water (3 x 100 cm{sup 3}). The dealuminated samples were characterized by {sup 29}Si and {sup 27}Al MAS NMR, X-ray powder diffraction and adsorption measurements. These data indicate that the resultant materials are highly crystalline and showed no signs of structural degradation both in short-range order ({sup 27}Al, {sup 29}Si MAS NMR) and long-range order (XRD). However, the SEM and high-resolution images were particularly informative.

  11. Connecting the Silicate Dust and Gas Properties of Distant Galaxies Using Quasar Absorption Systems

    NASA Astrophysics Data System (ADS)

    Aller, Monique C.; Kulkarni, Varsha P.; York, Donald G.; Welty, Daniel E.; Vladilo, Giovanni; Som, Debopam; Lackey, Kyle; Dwek, Eli; Beiranvand, Nassim; Morrison, Sean

    2016-01-01

    We present recent results from our program investigating the silicate dust properties in distant galaxies using quasar absorption systems. The dust and gas properties of distant galaxies can be characterized by studying the absorption features produced by them along the sightlines to luminous background quasars. Based on our prior finding that silicate dust absorption in z<1.5 quasar absorption systems exhibits a range of optical depths and absorption feature substructures, suggestive of silicate grain property variations, we are investigating silicate dust absorption in quasar absorption systems toward quasars with archival Spitzer Space Telescope Infrared Spectrograph (IRS) spectra. We present our measurements of the 10 and/or 18 micron silicate dust absorption feature(s) in these systems, and discuss constraints on the grain properties, such as composition and crystallinity, based on the shape and substructure present in these features. We also investigate the correlations between the silicate dust properties and the reddening. Connections between the silicate dust and gas phase metal absorption properties can also be probed for some of our targets with archival ground-based spectra. These relationships will yield valuable insights into the star formation history and evolution of metals and dust. This work is supported by NASA through ADAP grant NNX14AG74G and by an award issued by JPL/Caltech, and from US-NSF grant AST-1108830 to the University of South Carolina.

  12. Comparative pathology of silicate pneumoconiosis.

    PubMed Central

    Brambilla, C.; Abraham, J.; Brambilla, E.; Benirschke, K.; Bloor, C.

    1979-01-01

    A simple pneumoconiosis with lamellar birefringent crystals was observed in animals dying in the San Diego Zoo. We studied 100 autopsies from 11 mammalian and eight avian species. In mammals, mild pulmonary lesions comprised crystal-laden macrophages in alveoli and lymphatics. Interstitial fibrosis was present in 20% of cases. There were no nodules. In birds, dust retention produced large granulomas around tertiary bronchi without fibrosis. Mineralogic analysis using scanning and transmission electron microscopy showed most of the crystals to be silicates. Ninety percent were complex silicates, with aluminum-potassium silicates comprising 70% of the analyzed particles. Electron and x-ray diffraction showed the silicates to be muscovite mica and its hydrothermal degradation product, ie, illite clay. This mica was also present on filtration membranes of atmospheric air samples obtained from the San Diego Zoo. The amount of dust retention was related to the animal's age, anatomic or ecologic variances, and length of stay in the San Diego Zoo. Its semidesert atmosphere is rich in silicates, which are inhaled and deposited in the lungs. Similar mica-induced lesions are found in humans living in this region or the Southwest of the USA. This simple pneumoconiosis is likely to be widespread in human populations living in desert or semidesert climates. Images Figure 9 Figure 10 Figure 7 Figure 8 Figure 5 Figure 6 Figure 1 Figure 2 Figure 3 Figure 4 PMID:223447

  13. Low-voltage bendable pentacene thin-film transistor with stainless steel substrate and polystyrene-coated hafnium silicate dielectric.

    PubMed

    Yun, Dong-Jin; Lee, Seunghyup; Yong, Kijung; Rhee, Shi-Woo

    2012-04-01

    The hafnium silicate and aluminum oxide high-k dielectrics were deposited on stainless steel substrate using atomic layer deposition process and octadecyltrichlorosilane (OTS) and polystyrene (PS) were treated improve crystallinity of pentacene grown on them. Besides, the effects of the pentacene deposition condition on the morphologies, crystallinities and electrical properties of pentacene were characterized. Therefore, the surface treatment condition on dielectric and pentacene deposition conditions were optimized. The pentacene grown on polystyrene coated high-k dielectric at low deposition rate and temperature (0.2-0.3 /s and R.T.) showed the largest grain size (0.8-1.0 ?m) and highest crystallinity among pentacenes deposited various deposition conditions, and the pentacene TFT with polystyrene coated high-k dielectric showed excellent device-performance. To decrease threshold voltage of pentacene TFT, the polystyrene-thickness on high-k dielectric was controlled using different concentration of polystyrene solution. As the polystyrene-thickness on hafnium silicate decreases, the dielectric constant of polystyrene/hafnium silicate increases, while the crystallinity of pentacene grown on polystyrene/hafnium silicate did not change. Using low-thickness polystyrene coated hafnium silicate dielectric, the high-performance and low voltage operating (<5 V) pentacene thin film transistor (?: ~2 cm(2)/(V s), on/off ratio, >1 10(4)) and complementary inverter (DC gains, ~20) could be fabricated. PMID:22462593

  14. sup 29 Si and sup 27 Al NMR study of zeolite formation from alkali-leached kaolinites. Influence of thermal preactivation

    SciTech Connect

    Madani, A.; Aznar, A.; Sanz, J.; Serratosa, J.M. )

    1990-01-25

    The alkali treatment of kaolinites heated between 400 and 1,000{degree}C has been studied by NMR ({sup 29}Si and {sup 27}Al signals), IR, and x-ray diffraction techniques. The dissolution of kaolinite samples produces Al(OH){sub 4}{sup {minus}} and SiO{sub 4}{sup 4{minus}} species which participate in the zeolite germ formation. The nature of zeolites generated (hydroxysodalite, Na-A, and tetragonal P{sub t}) varies with thermal activation of the starting silicates, but the prolonged leaching of the samples favors the transformation of initially formed phases into the most stable P{sub t} zeolite. The synthesis of this compound (Si/Al > 1) requires the previous polymerization of dissolved silica species, and the amount of incorporated Si depends on the temperature of pretreatment of kaolinite.

  15. Photonucleation in silicate glasses

    NASA Astrophysics Data System (ADS)

    Goller, Martin Herbert

    The possibility of implementing gold-based photosensitivity in magnesium-aluminosilicate glasses was investigated. The compositional range was centered around the precipitation field of cordierite. The glass composition was varied by introducing alkali oxides to reduce the melting and processing temperatures since these conditions are also important for the photosensitivity process. A compromise was found among melting, processing and crystalline phases developed during heat treatment. Further studies addressed the introduction of the dopants necessary to obtain photosensitivity including the compounds of cerium and ZnO. Thermal analysis methods were used to determine the glass transformation temperature and the crystallization temperatures for the glasses. The phase development in crystallized glasses was analyzed using X-ray diffraction. High-temperature X-ray diffraction was used to follow the kinetics of the phase development. The glasses were also characterized using UV-VIS-spectroscopy, fluorescence spectroscopy and vibrational spectroscopy. Theoretical investigations were made concerning basicity of the glass and non-bridging oxygen content of the glass in relation to the presence of photosensitivity. Using this analysis, the glasses in this work were compared with those previously reported. Light scattering of small particles in glass was studied both theoretically and experimentally using a commercial photosensitive lithium-aluminosilicate glass containing silver. This glass was also investigated concerning its crystallization behavior arising from different irradiation/heat treatment parameters. From this study it was shown that the optical parameters, i.e., the refractive index and absorption coefficient must be determined accurately for each system, if a quantitative estimate of particle size is desired. It was not possible to generate photosensitivity in the intended system, even with additives of cerium compounds and ZnO as previously reported for other systems. The basicity analysis and the non-bridging oxygen analysis indicate that the nature of the composition is not favorable to photosensitivity. The results suggest the merit of this approach when attempting to predict photosensitivity in other glass forming systems.

  16. Highly fluorescent C-dots obtained by pyrolysis of quaternary ammonium ions trapped in all-silica ITQ-29 zeolite

    NASA Astrophysics Data System (ADS)

    Baldovi, Herme G.; Valencia, Susana; Alvaro, Mercedes; Asiri, Abdullah M.; Garcia, Hermenegildo

    2015-01-01

    C-dots obtained in the homogeneous phase may exhibit a broad particle size distribution. The formation of C-dots within nanometric reaction cavities could be a methodology to gain control on their size distribution. Among the various possibilities, in the present work, the cavities of small pore size zeolites have been used to confine C-dots generated by the pyrolysis of the organic structure directing agent present in the synthesis of these crystalline aluminosilicates. To explore this methodology, ITQ-29 zeolite having a Linde type A (LTA) structure was prepared as pure silica with 4-methyl-2,3,6,7-tetrahydro-1H,5H-pyrido[3.2.1-ij]quinolinium as the organic structure directing agent. Pyrolysis under an inert atmosphere at 550 °C of a pure-silica ITQ-29 sample (cubic particles of 4 μm edge) renders a highly fluorescent zeolite containing about 15 wt% of the carbonised residue. While another small pore zeolite, ITQ-12 (ITW), also renders photoluminescent C-dots under similar conditions, medium or large pore zeolites, such as silicalite (MFI) or pure silica Beta (BEA), failed to produce fluorescent powders under analogous thermal treatment and only decomposition and complete removal of the corresponding quaternary ammonium ion templates was observed for these zeolites. The dissolution of the pyrolysed ITQ-29 zeolite framework and the extraction of the carbon residue with ethyl acetate have allowed the characterisation of C-dots with particle sizes between 5 and 12 nm and a photoluminescence quantum yield of 0.4 upon excitation at 350 nm that is among the highest reported for non-surface functionalized C-dots. Photoluminescence varies with the excitation wavelength and is quenched by oxygen. Pyrolysed ITQ-29 powders can act as fluorescent oxygen sensors.

  17. Studies on the formation of hierarchical zeolite T aggregates with well-defined morphology in different template systems

    NASA Astrophysics Data System (ADS)

    Yin, Xiaoyan; Chu, Naibo; Lu, Xuewei; Li, Zhongfang; Guo, Hong

    2016-01-01

    In this paper, the disk-like and pumpkin-like hierarchical zeolite T aggregates consisted of primary nano-grains have been hydrothermally synthesized with and without the aid of the second template. The first template is used with tetramethylammonium hydroxide (TMAOH) and the second template is used with triethanolamine (TEA) or polyving akohol (PVA). A combination of characterization techniques, including XRD, SEM, TEM and N2 adsorption-desorption to examine the crystal crystallinity, morphology and surface properties of hierarchical zeolite T aggregates. In the single-template preparation process, the two-step varying-temperature treatment has been used to improve the meso-porosity of zeolite T aggregates. In the double-template preparation process, the amounts of PVA or TEA on the crystallinity, morphology and meso-porosity of zeolite T aggregates have been studied. It has been proved that the interstitial voids between the primary grains of aggregates are the origin of additional mesopores of samples. The micro- and meso-porosities of samples prepared with and without the second template have been contrasted in detail at last. In particular, the sample synthesized with the addition of PVA presents a hierarchical pore structure with the highest Sext value of 122 m2/g and Vmeso value of 0.255 cm3/g.

  18. CuO nanoparticles incorporated in hierarchical MFI zeolite as highly active electrocatalyst for non-enzymatic glucose sensing.

    PubMed

    Dong, Junping; Tian, Taolei; Ren, Linxiao; Zhang, Yuan; Xu, Jiaqiang; Cheng, Xiaowei

    2015-01-01

    A hierarchical MFI zeolite, with typical micro/meso bimodal pore structures, was prepared by desilication method. CuO nanoparticles (NPs) were incorporated into the hierarchical MFI zeolite by impregnation method. CuO/hierarchical zeolite composites were characterized by X-ray diffraction, transmission electron microscopy and nitrogen sorption. It is shown that the CuO nanoparticles are mostly dispersed in the mesopores with remaining of the crystallinity and morphology of the host zeolite. CuO nanoparticles located in hierarchical zeolite exhibit the excellent electrocatalytic performances to oxidation of glucose in alkaline media. The electrocatalytic activity enhances with increasing the loading content of CuO from 5% to 15%. The composites were fabricated for nonenzyme glucose sensing. Under the optimal conditions, the sensor shows a wide linear range from 510(-7) to 1.8410(-2) M with a low detection limit of 3.710(-7) M. The sensor also exhibits good repeatability, long-term stability as well as high selectivity against interfering species. PMID:25499226

  19. Water nanodroplets confined in zeolite pores.

    PubMed

    Coudert, Franois-Xavier; Cailliez, Fabien; Vuilleumier, Rodolphe; Fuchs, Alain H; Boutin, Anne

    2009-01-01

    We provide a comprehensive depiction of the behaviour of a nanodroplet of approximately equal to 20 water molecules confined in the pores of a series of 3D-connected isostructural zeolites with varying acidity, by means of molecular simulations. Both grand canonical Monte Carlo simulations using classical interatomic forcefields and first-principles Car-Parrinello molecular dynamics were used in order to characterise the behaviour of confined water by computing a range of properties, from thermodynamic quantities to electronic properties such as dipole moment, including structural and dynamical information. From the thermodynamic point of view, we have identified the all-silica zeolite as hydrophobic, and the cationic zeolites as hydrophilic; the condensation transition in the first case was demonstrated to be of first order. Furthermore, in-depth analysis of the dynamical and electronic properties of water showed that water in the hydrophobic zeolite behaves as a nanodroplet trying to close its hydrogen-bond network onto itself, with a few short-lived dangling OH groups, while water in hydrophilic zeolites "opens up" to form weak hydrogen bonds with the zeolite oxygen atoms. Finally, the dipole moment of confined water is studied and the contributions of water self-polarisation and the zeolite electric field are discussed. PMID:19227366

  20. Zeolites on Mars: Prospects for Remote Sensing

    NASA Technical Reports Server (NTRS)

    Gaffney, E. S.; Singer, R. B.; Kunkle, T. D.

    1985-01-01

    The Martian surface composition measured by Viking can be represented by several combinations of minerals incorporating major fractions of zeolites known to occur in altered mafic rocks and polar soils on Earth. The abundant occurrence of zeolites on Mars is consistent with what is known about both the physical and chemical environment of that planet. The laboratory reflectance spectra (0.65 to 2.55 microns) of a number of relatively pure zeolite minerals and some naturally occurring zeolite-clay soils were measured. All of the spectra measured are dominated by strong absorption near 1.4 and 1.9 microns and a steep reflectance drop longward of about 2.2 microns, all of which are due to abundant H2O. Weaker water overtone bands are also apparent, and in most cases there is spectral evidence for minor Fe(3+). In these features the zeolite spectra are similar to spectra of smectite clays which have abundant interlayer water. The most diagnostic difference between clay and zeolite spectra is the total absence in the zeolites of the weak structural OH absorption.

  1. Rejuvenation and silicic melt migration in a near-solidus silicic mush induced by "gas sparging"?

    NASA Astrophysics Data System (ADS)

    Bachmann, O.; Bergantz, G. W.; White, M. D.

    2002-12-01

    The 5000 km3 Fish Canyon Tuff displays petrographic and geochemical evidence for simultaneous dissolution of feldspars + quartz and crystallization of hydrous phases (hornblende + biotite) during gradual near-isobaric reheating from ~ 720 to 760 C. These observations, along with a high crystallinity (45 % crystals) and near-solidus mineral assemblage, suggest that the Fish Canyon magma cooled to a solidified crystal mush before being partly remelted by dissolution of feldspar and quartz just prior to eruption. We postulate this retrograde-prograde path in temperature may be a consequence of a voluminous shallow intrusion of water-rich mafic magma, which erupted shortly after the Fish Canyon Tuff as the 200 km3 Huerto Andesite. The absence of any measurable gradients in the Fish Canyon magma cannot be reconciled with a reheating event dominated by conductive heat transfer or significant mixing with the mafic magma: it requires that heat was dispersed throughout the batholithic Fish Canyon chamber rapidly and pervasively, in order to partially remelt feldspars and quartz without destabilizing the hydrous phases. For volatile-rich magmas stored in the upper crust, such as the Fish Canyon and Huerto magmas, it is now commonly assumed that they are saturated with a fluid phase. This low-density fluid is potentially an efficient heat carrier if it can percolate upward. To test this hypothesis, we performed numerical simulations of "gas sparging" through a crystalline framework saturated with a high-viscosity silicate melt. We assumed (1) that the crystallizing mafic magma releases volatiles, and (2) that the overlying silicic magma has crystallized to more than 50 %, becoming effectively a porous solid. We allowed a continuous flux of a hot (850-900C), H2O-CO2 fluid phase to enter the system from the base of the silicic mush. Preliminary results indicate that gas sparging is much more efficient that conduction in transferring heat if gas ascent rates are on the order of 0.1-1 m/y, and if volume of gas released by the underplating mafic magma is 30-40 % of the volume of the silicic mush. Using well-constrained initial and boundary conditions from the Fish Canyon system, timescales for rejuvenating the Fish Canyon mush are on the order of a few thousands of years. Gas sparging also provides an alternative mechanism to increase the internal pressure in silicic crystal mushes and induce gas filter pressing (drainage of the evolved interstitial melt from the mush), considered to be a potential process for the formation of high-SiO2 rhyolites (Sisson and Bacon, 1999). Maintaining a high volatile content in the Fish Canyon system would also provide an explanation for the stability of the hornblende and biotite during the prograde evolution. Ref: Sisson, T.W., and Bacon, C.R. (1999), Gas-driven filter pressing in magmas: Geology, v.27, p. 613-616.

  2. Framework-incorporated Mn and Co analcime zeolites: Synthesis and characterization

    SciTech Connect

    Azizi, Seyed Naser; Ehsani Tilami, Salma

    2013-02-15

    The framework-substituted cobalt and manganese analcime zeolites were synthesized via a direct hydrothermal approach. The obtained samples were characterized by XRD powder, SEM-EDX, nitrogen physical adsorption, Raman microscopy, diffuse reflectance UV-Vis and IR spectroscopy which complementarily demonstrated the incorporation of cobalt and manganese into the zeolites framework. The results showed that substitution of Mn and Co could be placed in two synthesis gels with same compositions containing Al/Mn=5 and Al/Co=4 mol ratios, respectively. In addition, with replacing Al with Mn and synthesis of Mn-modified analcime, zeolite with higher surface area and pore volume could be achieved than the Co modified analcime. - Graphical abstract: The images and adsorption-desorption isotherms of N{sub 2} at 77 K for (a) Co (b) Mn modified analcime. Highlights: Black-Right-Pointing-Pointer Synthesis of Co and Mn modified analcime for the first time. Black-Right-Pointing-Pointer Framework-incorporation of Co and Mn using the same silicate gel composition. Black-Right-Pointing-Pointer Applying several techniques to provide proofs for the characterization.

  3. Quantification of thickness and wrinkling of exfoliated two-dimensional zeolite nanosheets

    PubMed Central

    Kumar, Prashant; Agrawal, Kumar Varoon; Tsapatsis, Michael; Mkhoyan, K. Andre

    2015-01-01

    Some two-dimensional (2D) exfoliated zeolites are single- or near single-unit cell thick silicates that can function as molecular sieves. Although they have already found uses as catalysts, adsorbents and membranes precise determination of their thickness and wrinkling is critical as these properties influence their functionality. Here we demonstrate a method to accurately determine the thickness and wrinkles of a 2D zeolite nanosheet by comprehensive 3D mapping of its reciprocal lattice. Since the intensity modulation of a diffraction spot on tilting is a fingerprint of the thickness, and changes in the spot shape are a measure of wrinkling, this mapping is achieved using a large-angle tilt-series of electron diffraction patterns. Application of the method to a 2D zeolite with MFI structure reveals that the exfoliated MFI nanosheet is 1.5 unit cells (3.0 nm) thick and wrinkled anisotropically with up to 0.8 nm average surface roughness. PMID:25958985

  4. Structural insight into germanium-containing silicate species by electrospray ionization mass spectrometry (ESI-MS) and ESI-MS/MS.

    PubMed

    Schaack, Bernd Bastian; Schrader, Wolfgang; Schth, Ferdi

    2009-08-13

    The properties of zeolitic and related materials highly depend on their pore dimensions and topology as well as the presence and nature of framework heteroelements. Here, we present detailed insights into prenucleating solutions of zeolitic materials using two different organic structure-directing agents (SDAs) in the presence of fluoride ions. The silicate speciation was analyzed by means of electrospray ionization mass spectrometry (ESI-MS), wherein the structures of the occurring species were proven to depend on the nature of the used organic SDA. In addition, MS/MS experiments were revealed as a powerful tool to obtain detailed structural insight into the occurring silicate oligomers. With this information, we were able to locate heteroelements, namely, germanium, within these species and, furthermore, to determine the structure-directing effects of the used organic SDAs. PMID:19624110

  5. The role of zeolite in the Fischer–Tropsch synthesis over cobalt–zeolite catalysts

    NASA Astrophysics Data System (ADS)

    Sineva, L. V.; Asalieva, E. Yu; Mordkovich, V. Z.

    2015-11-01

    The review deals with the specifics of the Fischer–Tropsch synthesis for the one-stage syncrude production from CO and H2 in the presence of cobalt–zeolite catalytic systems. Different types of bifunctional catalysts (hybrid, composite) combining a Fischer–Tropsch catalyst and zeolite are reviewed. Special attention focuses on the mechanisms of transformations of hydrocarbons produced in the Fischer–Tropsch process on zeolite acid sites under the synthesis conditions. The bibliography includes 142 references.

  6. Studies on sorption properties of zeolite derived from Indian fly ash.

    PubMed

    Mishra, T; Tiwari, S K

    2006-09-01

    Indian fly ash has been completely converted to crystalline porous 13X zeolite by NaOH fusion at 600 degrees C followed by hydrothermal treatment at 105 degrees C for 20 h. Obtained materials were characterized by XRD, SEM and surface area measurement. Prepared material was used for the sorption study of different metal ions (Cu(2+), Co(2+) and Ni(2+)) at different pH, temperature. Thermodynamic data (DeltaS, DeltaH and DeltaG) corresponding to different metal ion uptake were evaluated from Langmuir equation. In all the experiment sorption capacity of prepared zeolite was found to be quite high than that of fly ash at acidic pH. However, the uptake selectivity order for both the materials is Cu(2+)>Co(2+)>Ni(2+). PMID:16563613

  7. Copper-Exchanged Zeolite L Traps Oxygen

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K.; Seshan, Panchalam K.

    1991-01-01

    Brief series of simple chemical treatments found to enhance ability of zeolite to remove oxygen from mixture of gases. Thermally stable up to 700 degrees C and has high specific surface area which provides high capacity for adsorption of gases. To increase ability to adsorb oxygen selectively, copper added by ion exchange, and copper-exchanged zeolite reduced with hydrogen. As result, copper dispersed atomically on inner surfaces of zeolite, making it highly reactive to oxygen, even at room temperature. Reactivity to oxygen even greater at higher temperatures.

  8. Photoinduced electron transfer reactions in zeolite cages

    SciTech Connect

    Dutta, P.K.

    1992-01-01

    This report summarizes work in the two areas of zeolites and layered double hydroxides. Results of studies on structural aspects of Ru(bpy)[sub 3][sup 2+]-zeolite Y are summarized. Photoinduced electron transfer between entrapped Ru(bpy)[sub 3][sup 2+] and methylviologen (MV) in neighboring supercages was examined. Benzylviologen was also used. Since molecules larger than 13 [angstrom] cannot be accomodated in zeolite cages, the layered double metal hydroxides (LDH) LiAl[sub 2](OH)[sub 6][sup +]X[sup [minus

  9. Pulsed laser deposition of zeolitic membranes

    SciTech Connect

    Peachey, N.M.; Dye, R.C.; Ries, P.D.

    1995-02-01

    The pulsed laser deposition of zeolites to form zeolitic thin films is described. Films were grown using both mordenite and faujasite targets and were deposited on various substrates. The optimal films were obtained when the target and substrate were separated by 5 cm. These films are comprised of small crystallites embedded in an amorphous matrix. Transmission electron microscopy reveals that the amorphous material is largely porous and that the pores appear to be close to the same size as the parent zeolite. Zeolotic thin films are of interest for sensor, gas separation, and catalytic applications.

  10. Photochemical charge separation in zeolites: Electron transfer dynamics, nanocrystals and zeolitic membranes. Final technical report

    SciTech Connect

    Dutta, Prabir K.

    2001-09-30

    Aluminosilicate zeolites provide an excellent host for photochemical charge separation. Because of the constraints provided by the zeolite, the back electron transfer from the reduced acceptor to the oxidized sensitizer is slowed down. This provides the opportunity to separate the charge and use it in a subsequent reaction for water oxidation and reduction. Zeolite-based ruthenium oxide catalysts have been found to be efficient for the water splitting process. This project has demonstrated the usefulness of zeolite hosts for photolytic splitting of water.

  11. Battery components employing a silicate binder

    DOEpatents

    Delnick, Frank M.; Reinhardt, Frederick W.; Odinek, Judy G.

    2011-05-24

    A battery component structure employing inorganic-silicate binders. In some embodiments, casting or coating of components may be performed using aqueous slurries of silicates and electrode materials or separator materials.

  12. Spectroscopic and XRD characterisation of zeolite catalysts active for the oxidative methylation of benzene with methane

    NASA Astrophysics Data System (ADS)

    Adebajo, Moses O.; Long, Mervyn A.; Frost, Ray L.

    2004-03-01

    The benzene methylation with methane over zeolite catalysts was previously shown in our laboratory to require the presence of oxygen. Thus, a two-step mechanism involving the intermediate formation of methanol by partial oxidation of methane followed by the methylation of benzene with methanol in the second step, was postulated. This paper now reports the results of the characterisation of the zeolite catalysts used for the oxidative benzene methylation reaction in order to provide some information about their composition, structure, properties and their behaviour before and after the reaction. The catalysts were characterised by X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray fluorescence (XRF), FT-IR and solid state NMR. XRD results indicate that the crystalline structures of all the ZSM-5 and H-beta catalysts remained unchanged after batch reaction of benzene with methane over the catalysts in agreement with the observation that the catalysts recovered from the reactor could be reused without loss of activity. Elemental analyses and FT-IR data show that as the level of metal ion exchange increases, the Brnsted acid concentration decreases but this metal ion exchange does not totally remove Brnsted acidity. FT-IR results further show that only a small amount of acid sites is actually necessary for a catalyst to be active since used catalysts containing highly reduced Brnsted acidity are found to be reusable without any loss of their activity. 29Si and 27Al magic angle spinning (MAS) NMR together with FT-IR spectra also show that all the active zeolites catalysts contain some extra-framework octahedral aluminium in addition to the normal tetrahedral framework aluminium. The presence of this extra-lattice aluminium does not, however, have any adverse effect on the crystallinity of the catalysts both before and after oxidative benzene methylation reaction. There appears also to be no significant dealumination of the zeolite catalysts during reaction since their catalytic performance was retained after use.

  13. Lithologic mapping of silicate rocks using TIMS

    NASA Technical Reports Server (NTRS)

    Gillespie, A. R.

    1986-01-01

    Common rock-forming minerals have thermal infrared spectral features that are measured in the laboratory to infer composition. An airborne Daedalus scanner (TIMS) that collects six channels of thermal infrared radiance data (8 to 12 microns), may be used to measure these same features for rock identification. Previously, false-color composite pictures made from channels 1, 3, and 5 and emittance spectra for small areas on these images were used to make lithologic maps. Central wavelength, standard deviation, and amplitude of normal curves regressed on the emittance spectra are related to compositional information for crystalline igneous silicate rocks. As expected, the central wavelength varies systematically with silica content and with modal quartz content. Standard deviation is less sensitive to compositional changes, but large values may result from mixed admixture of vegetation. Compression of the six TIMS channels to three image channels made from the regressed parameters may be effective in improving geologic mapping from TIMS data, and these synthetic images may form a basis for the remote assessment of rock composition.

  14. Effect of vanadium contamination on the framework and micropore structure of ultra stable Y-zeolite.

    PubMed

    Etim, U J; Xu, B; Ullah, Rooh; Yan, Z

    2016-02-01

    Y-zeolites are the main component of fluid catalytic cracking (FCC) catalyst for conversion of crude petroleum to products of high demand including transportation fuel. We investigated effects of vanadium which is present as one of the impurities in FCC feedstock on the framework and micropore structure of ultra-stable (US) Y-zeolite. The zeolite samples were prepared and characterized using standard techniques including: (1) X-ray diffraction, (2) N2 adsorption employing non local density functional theory method, NLDFT, (3) Transmittance and Pyridine FTIR, (4) Transmittance electron microscopy (TEM), and (5) (27)Al and (29)Si MAS-NMR. Results revealed that in the presence of steam, vanadium caused excessive evolution of non inter-crystalline mesopores and structural damage. The evolved mesopore size averaged about 25.0nm at 0.5wt.% vanadium loading, far larger than mesopore size in zeolitic materials with improved hydrothermal stability and performance for FCC catalyst. A mechanism of mesopore formation based on accelerated dealumination has been proposed and discussed. Vanadium immobilization experiments conducted to mitigate vanadium migration into the framework clearly showed vanadium is mobile at reaction conditions. From the results, interaction of vanadium with the passivator limits and decreases mobility and activity of vanadium into inner cavities of the zeolite capable of causing huge structure breakdown and acid sites destruction. This study therefore deepens insight into the causes of alteration in activity and selectivity of vanadium contaminated catalyst and hints on a possible mechanism of passivation in vanadium passivated FCC catalyst. PMID:26520826

  15. FORMATION OF COSMIC CRYSTALS IN HIGHLY SUPERSATURATED SILICATE VAPOR PRODUCED BY PLANETESIMAL BOW SHOCKS

    SciTech Connect

    Miura, H.; Yamada, J.; Tsukamoto, K.; Nozawa, J.; Tanaka, K. K.; Yamamoto, T.; Nakamoto, T.

    2010-08-10

    Several lines of evidence suggest that fine silicate crystals observed in primitive meteorite and interplanetary dust particles (IDPs) nucleated in a supersaturated silicate vapor followed by crystalline growth. We investigated evaporation of {mu}m-sized silicate particles heated by a bow shock produced by a planetesimal orbiting in the gas in the early solar nebula and condensation of crystalline silicate from the vapor thus produced. Our numerical simulation of shock-wave heating showed that these {mu}m-sized particles evaporate almost completely when the bow shock is strong enough to cause melting of chondrule precursor dust particles. We found that the silicate vapor cools very rapidly with expansion into the ambient unshocked nebular region; for instance, the cooling rate is estimated to be as high as 2000 K s{sup -1} for a vapor heated by a bow shock associated with a planetesimal of radius 1 km. The rapid cooling of the vapor leads to nonequilibrium gas-phase condensation of dust at temperatures much lower than those expected from the equilibrium condensation. It was found that the condensation temperatures are lower by a few hundred K or more than the equilibrium temperatures. This explains the results of the recent experimental studies of condensation from a silicate vapor that condensation in such large supercooling reproduces morphologies similar to those of silicate crystals found in meteorites. Our results strongly suggest that the planetesimal bow shock is one of the plausible sites for formation of not only chondrules but also other cosmic crystals in the early solar system.

  16. Amended Silicated for Mercury Control

    SciTech Connect

    James Butz; Thomas Broderick; Craig Turchi

    2006-12-31

    Amended Silicates{trademark}, a powdered, noncarbon mercury-control sorbent, was tested at Duke Energy's Miami Fort Station, Unit 6 during the first quarter of 2006. Unit 6 is a 175-MW boiler with a cold-side electrostatic precipitator (ESP). The plant burns run-of-the-river eastern bituminous coal with typical ash contents ranging from 8-15% and sulfur contents from 1.6-2.6% on an as-received basis. The performance of the Amended Silicates sorbent was compared with that for powdered activated carbon (PAC). The trial began with a period of baseline monitoring during which no sorbent was injected. Sampling during this and subsequent periods indicated mercury capture by the native fly ash was less than 10%. After the baseline period, Amended Silicates sorbent was injected at several different ratios, followed by a 30-day trial at a fixed injection ratio of 5-6 lb/MMACF. After this period, PAC was injected to provide a comparison. Approximately 40% mercury control was achieved for both the Amended Silicates sorbent and PAC at injection ratios of 5-6 lbs/MMACF. Higher injection ratios did not achieve significantly increased removal. Similar removal efficiencies have been reported for PAC injection trials at other plants with cold-side ESPs, most notably for plants using medium to high sulfur coal. Sorbent injection did not detrimentally impact plant operations and testing confirmed that the use of Amended Silicates sorbent does not degrade fly ash quality (unlike PAC). The cost for mercury control using either PAC or Amended Silicates sorbent was estimated to be equivalent if fly ash sales are not a consideration. However, if the plant did sell fly ash, the effective cost for mercury control could more than double if those sales were no longer possible, due to lost by-product sales and additional cost for waste disposal. Accordingly, the use of Amended Silicates sorbent could reduce the overall cost of mercury control by 50% or more versus PAC for locations where fly ash is sold as a by-product.

  17. Transmission Electron Microscopy of Al-rich Silicate Stardust from Asymptotic Giant Branch Stars

    NASA Astrophysics Data System (ADS)

    Vollmer, Christian; Hoppe, Peter; Brenker, Frank E.

    2013-05-01

    We report on transmission electron microscopy (TEM) investigations of two mineralogically unusual stardust silicates to constrain their circumstellar condensation conditions. Both grains were identified by high spatial resolution nano secondary ion mass spectrometry (NanoSIMS) in the Acfer 094 meteorite, one of the most pristine carbonaceous chondrites available for study. One grain is a highly crystalline, highly refractory (Fe content < 0.5 at%), structurally undisturbed orthopyroxene (MgSiO3) with an unusually high Al content (1.8 0.5 at%). This is the first TEM documentation of a single crystal pyroxene within the complete stardust silicate data set. We interpret the microstructure and chemistry of this grain as being a direct condensate from a gas of locally non-solar composition (i.e., with a higher-than-solar Al content and most likely also a lower-than-solar Mg/Si ratio) at (near)-equilibrium conditions. From the overabundance of crystalline olivine (six reported grains to date) compared to crystalline pyroxene (only documented as a single crystal in this work) we infer that formation of olivine over pyroxene is favored in circumstellar environments, in agreement with expectations from condensation theory and experiments. The second stardust silicate consists of an amorphous Ca-Si rich material which lacks any crystallinity based on TEM observations in which tiny (<20 nm) hibonite nanocrystallites are embedded. This complex assemblage therefore attests to the fast cooling and rapidly changing chemical environments under which dust grains in circumstellar shells form.

  18. TRANSMISSION ELECTRON MICROSCOPY OF Al-RICH SILICATE STARDUST FROM ASYMPTOTIC GIANT BRANCH STARS

    SciTech Connect

    Vollmer, Christian; Hoppe, Peter; Brenker, Frank E.

    2013-05-20

    We report on transmission electron microscopy (TEM) investigations of two mineralogically unusual stardust silicates to constrain their circumstellar condensation conditions. Both grains were identified by high spatial resolution nano secondary ion mass spectrometry (NanoSIMS) in the Acfer 094 meteorite, one of the most pristine carbonaceous chondrites available for study. One grain is a highly crystalline, highly refractory (Fe content < 0.5 at%), structurally undisturbed orthopyroxene (MgSiO{sub 3}) with an unusually high Al content (1.8 {+-} 0.5 at%). This is the first TEM documentation of a single crystal pyroxene within the complete stardust silicate data set. We interpret the microstructure and chemistry of this grain as being a direct condensate from a gas of locally non-solar composition (i.e., with a higher-than-solar Al content and most likely also a lower-than-solar Mg/Si ratio) at (near)-equilibrium conditions. From the overabundance of crystalline olivine (six reported grains to date) compared to crystalline pyroxene (only documented as a single crystal in this work) we infer that formation of olivine over pyroxene is favored in circumstellar environments, in agreement with expectations from condensation theory and experiments. The second stardust silicate consists of an amorphous Ca-Si rich material which lacks any crystallinity based on TEM observations in which tiny (<20 nm) hibonite nanocrystallites are embedded. This complex assemblage therefore attests to the fast cooling and rapidly changing chemical environments under which dust grains in circumstellar shells form.

  19. 21 CFR 582.2227 - Calcium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  20. 21 CFR 582.2227 - Calcium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  1. 21 CFR 182.2227 - Calcium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  2. 21 CFR 182.2227 - Calcium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  3. 21 CFR 582.2227 - Calcium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  4. 21 CFR 182.2227 - Calcium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  5. 21 CFR 582.2227 - Calcium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  6. 21 CFR 582.2227 - Calcium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  7. 21 CFR 182.2227 - Calcium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c)...

  8. 21 CFR 582.2437 - Magnesium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Magnesium silicate. 582.2437 Section 582.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations,...

  9. 21 CFR 182.2437 - Magnesium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Magnesium silicate. 182.2437 Section 182.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations,...

  10. 21 CFR 182.2437 - Magnesium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Magnesium silicate. 182.2437 Section 182.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations,...

  11. 21 CFR 582.2437 - Magnesium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Magnesium silicate. 582.2437 Section 582.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations,...

  12. 21 CFR 582.2437 - Magnesium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Magnesium silicate. 582.2437 Section 582.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations,...

  13. 21 CFR 582.2437 - Magnesium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Magnesium silicate. 582.2437 Section 582.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations,...

  14. 21 CFR 582.2437 - Magnesium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Magnesium silicate. 582.2437 Section 582.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations,...

  15. 21 CFR 182.2437 - Magnesium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Magnesium silicate. 182.2437 Section 182.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations,...

  16. 21 CFR 182.2437 - Magnesium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Magnesium silicate. 182.2437 Section 182.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Magnesium silicate. (a) Product. Magnesium silicate. (b) Tolerance. 2 percent. (c) Limitations,...

  17. Liquid crystalline bispropargyl thermosets

    SciTech Connect

    Langlois, D.A.; Benicewicz, B.C.; Douglas, E.P.

    1998-11-01

    A series of rigid-rod bispropargyl thermoset monomers have been synthesized. These monomers were examined by differential scanning calorimetry (DSC) and hot stage polarized optical microscopy. Enantiotropic or monotropic nematic liquid crystalline phases were observed for all but two monomers. Partial curing of these reactive liquid crystalline monomers resulted in the formation of stable liquid crystalline phases with broad nematic phase after partial curing. DSC investigations indicated that the onset temperature of thermally induced cross-linking was approximately 260 C and insensitive to the phase type. The rate of cure was insensitive to the phase in which the cure occurred due to the unusual reaction mechanism for the propargyl end group.

  18. Zeolite membranes fabricated by pulsed laser deposition

    SciTech Connect

    Peachey, N.M.; Espinoza, B.F.; Dye, R.C.

    1995-12-01

    The well-defined cavities of the zeolite cage provides an attractive structure around which a membrane can be constructed. However, the fabrication of useful thin film zeolite membranes has presented difficulties since these crystals are not readily formed into thin, defect-free materials. Recently, pulsed laser deposition (PLD) has been used to make thin film sensors. In this process, a laser beam is used to create a plume of particles having reactive edges or dangling bonds. These can then react on a support material to form porous zeolites embedded in a dense phase material. The use of differing wavelengths of laser light can provide a degree of control of the energy of the particles oblated from the target. These novel thin film zeolites provide a unique approach to the synthesis of separation membranes and sensors.

  19. Mixing of zeolite powders and molten salt

    SciTech Connect

    Pereira, C.; Zyryanov, V.N.; Lewis, M.A.; Ackerman, J.P.

    1996-05-01

    Transuranics and fission products in a molten salt can be incorporated into zeolite A by an ion exchange process and by a batch mixing or blending process. The zeolite is then mixed with glass and consolidated into a monolithic waste form for geologic disposal. Both processes require mixing of zeolite powders with molten salt at elevated temperatures (>700 K). Complete occlusion of salt and a uniform distribution of chloride and fission products are desired for incorporation of the powders into the final waste form. The relative effectiveness of the blending process was studied over a series of temperature, time, and composition profiles. The major criteria for determining the effectiveness of the mixing operations were the level and uniformity of residual free salt in the mixtures. High operating temperatures (>775 K) improved salt occlusion. Reducing the chloride levels in the mixture to below 80% of the full salt capacity of the zeolite significantly reduced the free salt level in the final product.

  20. Complexation of porphyrins with nanoparticles of zeolite

    NASA Astrophysics Data System (ADS)

    Gyulkhandanyan, Anna G.; Zakoyan, Anna A.; Sargsyan, Hakob H.; Ghazaryan, Robert K.; Sheyranyan, Marina A.; Gyulkhandanyan, Grigor V.

    2015-06-01

    The binding of nanoparticles zeolite with a number of cationic porphyrins are studied. Previously, it was established that the main mechanism of binding the zeolite nanoparticles with cationic porphyrins is an ionic bond. Since binding of porphyrins as ligands to nanoparticles at the initial stage of interaction is determined by the Brownian motion of porphyrins, it is obvious that the interaction of porphyrins with nanoparticles may depend on the temperature. In the present paper by methods of absorption and fluorescence spectroscopy was studied the complexation of porphyrins with zeolite nanoparticles at different temperature conditions. It was established that there is a clear temperature dependence of the complexation of cationic metalloporphyrins with zeolite naonoparticles, and for correct determination of the percentage of binding must be strict thermostating of the experimental conditions.

  1. Effects of ionization on silicate glasses. [Silicate glasses

    SciTech Connect

    Primak, W.

    1982-02-01

    This evaluation of radiation effects in silicate glasses caused by ionization is based on our own investigations, on material collected in our files (reports, articles, and notes), and on a computer literature search through recent issues of Physics Abstracts and Chemical Abstracts (and the apparently pertinent references which appeared). Some of our recent results, available heretofore only in internal correspondence, are presented in some detail. It is concluded that research into the behavior of silicate glasses generally will be required before the specific effects in the radioactive waste storage glasses can be properly understood and evaluated. Two particular neglected areas of investigation are targeted for immediate concern: a kinetic analysis of annealing data and the acquisition of data on effects of irradiation at controlled elevated temperatures.

  2. Kinetics of zeolite dealumination in steam

    SciTech Connect

    Hughes, C.D.; Labouriau, A.; Crawford, S.N.; Romero, R.; Quirin, J.; Earl, W.L.

    1998-08-01

    Zeolite dealumination is a well known phenomenon that contributes to the deactivation or activation of catalysts in several different applications. The most obvious effect is in acid catalysis where dealumination under reaction conditions removes the Broensted sites, thus deactivating the catalyst. The authors are interested in the use of cation exchanged zeolites as selective reduction catalysts for removal of NO{sub x} from exhaust streams, particularly from automotive exhaust. In this case, copper exchanged ZSM-5 has been shown to be an effective catalyst for the generic reaction of NO{sub x} with hydrocarbons. However, high temperature and steam in combustion exhaust causes dealumination and consequent migration of copper out of the zeolite structure resulting in rapid deactivation of the catalyst. Dealumination of zeolites has been reported by many authors in uncountable papers and cannot be reviewed here. However, to the authors` knowledge there are no reports on the kinetics of dealumination under varying conditions of temperature and steam. By measuring the kinetics of dealumination with different zeolites and exchange cations they expect to develop working models of the dealumination process that will allow control of zeolite deactivation. This manuscript is a description of the basic techniques used and a progress report on the very beginning of this study.

  3. Three Mile Island zeolite vitirification demonstration program

    SciTech Connect

    Siemens, D.H.; Knowlton, D.E.; Shupe, M.W.

    1981-06-01

    The cleanup of the high-activity-level water at Three Mile Island (TMI) provides an opportunity to further develop waste management technology. Approximately 790,000 gallons of high-activity-level water at TMI's Unit-2 Nuclear Power Station will be decontaminated at the site using the submerged demineralizer system (SDS). In the SDS process, the cesium and strontium in the water are sorbed onto zeolite that is contained within metal liners. The Department of Energy has asked the Pacific Northwest Laboratory (PNL) to take a portion of the zeolite from the SDS process and demonstrate, on a production scale, that this zeolite can be vitrified using the in-can melting process. This paper is a brief overview of the TMI zeolite vitrification program. The first section discusses the formulation of a glass suitable for immobilizing SDS zeolite. The following section describes a feed system that was developed to feed zeolite to the in-can melter. It also describes the in-can melting process and the government owned facilities in which the demonstrations will take place. Finally, the schedule for completing the program activities is outlined.

  4. Crystalline Silica Primer

    USGS Publications Warehouse

    Staff- Branch of Industrial Minerals

    1992-01-01

    substance and will present a nontechnical overview of the techniques used to measure crystalline silica. Because this primer is meant to be a starting point for anyone interested in learning more about crystalline silica, a list of selected readings and other resources is included. The detailed glossary, which defines many terms that are beyond the scope of this publication, is designed to help the reader move from this presentation to a more technical one, the inevitable next step.

  5. Probing zeolites by vibrational spectroscopies.

    PubMed

    Bordiga, Silvia; Lamberti, Carlo; Bonino, Francesca; Travert, Arnaud; Thibault-Starzyk, Frdric

    2015-10-21

    This review addresses the most relevant aspects of vibrational spectroscopies (IR, Raman and INS) applied to zeolites and zeotype materials. Surface Brnsted and Lewis acidity and surface basicity are treated in detail. The role of probe molecules and the relevance of tuning both the proton affinity and the steric hindrance of the probe to fully understand and map the complex site population present inside microporous materials are critically discussed. A detailed description of the methods needed to precisely determine the IR absorption coefficients is given, making IR a quantitative technique. The thermodynamic parameters of the adsorption process that can be extracted from a variable-temperature IR study are described. Finally, cutting-edge space- and time-resolved experiments are reviewed. All aspects are discussed by reporting relevant examples. When available, the theoretical literature related to the reviewed experimental results is reported to support the interpretation of the vibrational spectra on an atomic level. PMID:26435467

  6. The zeolite deposits of Greece

    USGS Publications Warehouse

    Stamatakis, M.G.; Hall, A.; Hein, J.R.

    1996-01-01

    Zeolites are present in altered pyroclastic rocks at many localities in Greece, and large deposits of potential economic interest are present in three areas: (1) the Evros region of the province of Thrace in the north-eastern part of the Greek mainland; (2) the islands of Kimolos and Poliegos in the western Aegean; and (3) the island of Samos in the eastern Aegean Sea. The deposits in Thrace are of Eocene-Oligocene age and are rich in heulandite and/or clinoptilolite. Those of Kimolos and Poliegos are mainly Quaternary and are rich in mordenite. Those of Samos are Miocene, and are rich in clinoptilolite and/or analcime. The deposits in Thrace are believed to have formed in an open hydrological system by the action of meteoric water, and those of the western Aegean islands in a similar way but under conditions of high heat flow, whereas the deposits in Samos were formed in a saline-alkaline lake.

  7. Zeolite LTA Nanoparticles Prepared by Laser-Induced Fracture of Zeolite Microcrystals.

    PubMed

    Nichols, William T; Kodaira, Tetsuya; Sasaki, Yukichi; Shimizu, Yoshiki; Sasaki, Takeshi; Koshizaki, Naoto

    2006-01-12

    Zeolite LTA nanoparticles are prepared by laser-induced fragmentation of zeolite LTA microparticles using a pulsed laser. Zeolite nanoparticle formation is attributed to absorption of the laser at impurities or defects within the zeolite microcrystal generating thermoelastic stress that mechanically fractures the microparticle into smaller nanoparticle fragments. Experimentally, it is found that nanoparticles have a wide size and morphology distribution. Large nanoparticles (>200 nm) are typically irregularly shaped crystals of zeolite LTA, whereas small nanoparticles (<50 nm) tend to be spherical, dense, and amorphous, indicative of destruction of the original LTA crystal structure. Results of the fragmentation versus laser parameters show that shorter laser wavelengths are more efficient at producing zeolite nanoparticles, which is explained based on a larger cross section for optical absorption in the zeolite crystal. Increasing the laser energy density irradiating the sample was found to be a trade-off between increasing the amount of fragmentation and increasing the amount of structural damage to the zeolite crystal. It is suggested that in the presence of strongly absorbing defects, plasma formation is induced resulting in dramatically higher temperatures. On the basis of these results it is suggested the optimal laser processing conditions are 355 nm and 10 mJ/pulse laser energy for our LTA samples. PMID:16471503

  8. Influence of zeolite crystal size on zeolite-polyamide thin film nanocomposite membranes.

    PubMed

    Lind, Mary L; Ghosh, Asim K; Jawor, Anna; Huang, Xiaofei; Hou, William; Yang, Yang; Hoek, Eric M V

    2009-09-01

    Zeolite-polyamide thin film nanocomposite membranes were coated onto polysulfone ultrafiltration membranes by interfacial polymerization of amine and acid chloride monomers in the presence of Linde type A zeolite nanocrystals. A matrix of three different interfacial polymerization chemistries and three different-sized zeolite crystals produced nanocomposite thin films with widely varying structure, morphology, charge, hydrophilicity, and separation performance (evaluated as reverse osmosis membranes). Pure polyamide film properties were tuned by changing polymerization chemistry, but addition of zeolite nanoparticles produced even greater changes in separation performance, surface chemistry, and film morphology. For fixed polymer chemistry, addition of zeolite nanoparticles formed more permeable, negatively charged, and thicker polyamide films. Smaller zeolites produced greater permeability enhancements, but larger zeolites produced more favorable surface properties; hence, nanoparticle size may be considered an additional "degree of freedom" in designing thin film nanocomposite reverse osmosis membranes. The data presented offer additional support for the hypothesis that zeolite crystals alter polyamide thin film structure when they are present during the interfacial polymerization reaction. PMID:19527039

  9. Modifying Silicates for Better Dispersion in Nanocomposites

    NASA Technical Reports Server (NTRS)

    Campbell, Sandi

    2005-01-01

    An improved chemical modification has been developed to enhance the dispersion of layered silicate particles in the formulation of a polymer/silicate nanocomposite material. The modification involves, among other things, the co-exchange of an alkyl ammonium ion and a monoprotonated diamine with interlayer cations of the silicate. The net overall effects of the improved chemical modification are to improve processability of the nanocomposite and maximize the benefits of dispersing the silicate particles into the polymer. Some background discussion is necessary to give meaning to a description of this development. Polymer/silicate nanocomposites are also denoted polymer/clay composites because the silicate particles in them are typically derived from clay particles. Particles of clay comprise layers of silicate platelets separated by gaps called "galleries." The platelet thickness is 1 nm. The length varies from 30 nm to 1 m, depending on the silicate. In order to fully realize the benefits of polymer/silicate nanocomposites, it is necessary to ensure that the platelets become dispersed in the polymer matrices. Proper dispersion can impart physical and chemical properties that make nanocomposites attractive for a variety of applications. In order to achieve nanometer-level dispersion of a layered silicate into a polymer matrix, it is typically necessary to modify the interlayer silicate surfaces by attaching organic functional groups. This modification can be achieved easily by ion exchange between the interlayer metal cations found naturally in the silicate and protonated organic cations - typically protonated amines. Long-chain alkyl ammonium ions are commonly chosen as the ion-exchange materials because they effectively lower the surface energies of the silicates and ease the incorporation of organic monomers or polymers into the silicate galleries. This completes the background discussion. In the present improved modification of the interlayer silicate surfaces, the co-ion exchange strengthens the polymer/silicate interface and ensures irreversible separation of the silicate layers. One way in which it does this is to essentially tether one amine of each diamine molecule to a silicate surface, leaving the second amine free for reaction with monomers during the synthesis of a polymer. In addition, the incorporation of alkyl ammonium ions into the galleries at low concentration helps to keep low the melt viscosity of the oligomer formed during synthesis of the polymer and associated processing - a consideration that is particularly important in the case of a highly cross-linked, thermosetting polymer. Because of the chemical bonding between the surface-modifying amines and the monomers, even when the alkyl ammonium ions become degraded at high processing temperature, the silicate layers do not aggregate and, hence, nanometer-level dispersion is maintained.

  10. Silicate Dust in RS Ophiuchi

    NASA Astrophysics Data System (ADS)

    Rushton, M. T.; Woodward, C. E.; Helton, L. A.; Gehrz, R. D.; Evans, A.; Kaminsky, B.; Pavlenko, Y. V.; Eyres, S. P. S.; Maxwell, M.

    2014-12-01

    We present Spitzer IRS spectra of the recurrent nova RS Ophiuchi obtained between 2006 and 2009. The data show emission lines due to HI, [Ne II], [Ne V], [Ne VI] and [O IV] and the well known silicate features at 10 ?m and 18 ?m, whose behaviour are reported here. The silicate features are variable in the period covered by the observations, appearing strongest in our 2007 data. Interestingly, the central wavelength of the 18 ?m band is shorter than observed in other symbiotic systems and other circumstellar environments, suggesting unusual grain properties in RS Oph. We report changes that have taken place in the dusty environment in RS Oph and investigate the properties of the dust grains.

  11. Optimizing the crystallinity and acidity of H-SAPO-34 by fluoride for synthesizing Cu/SAPO-34 NH3-SCR catalyst.

    PubMed

    Ma, Jing; Si, Zhichun; Wu, Xiaodong; Weng, Duan; Ma, Yue

    2016-03-01

    A series of H-SAPO-34 zeolites were synthesized by a hydrothermal method in fluoride media. The as-synthesized H-SAPO-34 zeolites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 physisorption, temperature-programmed desorption of NH3 (NH3-TPD) and nuclear magnetic resonance (NMR) measurements. The results showed that a certain concentration of F(-) anions promoted the nucleation and crystallization of H-SAPO-34. The H-SAPO-34 synthesized in the fluoride media showed high crystallinity, uniform particle size distribution, large specific surface area and pore volume, and enhanced acidity. Therefore, Cu/SAPO-34 based on the fluoride-assisted zeolite showed a broadened temperature window for the selective catalytic reduction of NO by NH3 (NH3-SCR) reaction due to the enhanced acidity of the zeolite and the improved dispersion of copper species. PMID:26969071

  12. Kilogram scale production of EMT zeolite: Optimization of the synthesis conditions

    SciTech Connect

    Anglerot, D.; Fitoussi, F.; Schulz, P.

    1995-12-01

    Faujasite type zeolites have found Widespread use in industrial applications, both as catalysts and as adsorbents. EMT (Elf Mulhouse Two), the hexagonal polymorph of faujasite, is prepared in 8 days at 110{degrees}C from a synthesis gel containing 18-crown-6 as organic template. In this work it was aimed at developing a reproducible method to prepare kilogram batches of highly crystalline and pure EMT, focusing in particular on the raw material quality, the template content and the influence of agitation (type and rate) on the ageing and crystallization periods. The characterization of the obtained materials is also reported (XRD, chemical and thermal analyses, SEM, NMR spectroscopy ... ).

  13. Evidence of yttrium silicate inclusions in YSZ-porcelain veneers.

    PubMed

    Stoner, Brian R; Griggs, Jason A; Neidigh, John; Piascik, Jeffrey R

    2014-04-01

    This report introduces the discovery of crystalline defects that can form in the porcelain veneering layer when in contact with yttria-stabilized zirconia (YSZ). The focus was on dental prostheses and understanding the defects that form in the YSZ/porcelain system; however the data reported herein may have broader implications toward the use and stability of YSZ-based ceramics in general. Specimens were cut from fully sintered YSZ plates and veneering porcelain was applied (<1 mm thick) to one surface and fired under manufacturer's recommended protocol. Scanning electron microscopy (SEM) with integrated electron dispersive X-ray (EDAX) was used for microstructural and elemental analysis. EDAX, for chemical analysis and transmission electron diffraction (TED) for structural analysis were both performed in the transmission electron microscope (TEM). Additionally, in order to spatially resolve Y-rich precipitates, micro-CT scans were conducted at varying depths within the porcelain veneer. Local EDAX (SEM) was performed in the regions of visible inclusions and showed significant increases in yttrium concentration. TEM specimens also showed apparent inclusions in the porcelain and selected area electron diffraction was performed on these regions and found the inclusions to be crystalline and identified as either yttrium-silicate (Y2 SiO5 ) or yttrium-disilicate (Y2 Si2 O7 ). Micro-CT data showed that yttrium-silicate precipitates were distributed throughout the thickness of the porcelain veneer. Future studies are needed to determine whether many of the premature failures associated with this materials system may be the result of crystalline flaws that form as a result of high temperature yttrium diffusion near the surfaces of YSZ. PMID:24106151

  14. Use of zeolitized pumice waste as a water softening agent.

    PubMed

    Arrigo, I; Catalfamo, P; Cavallari, L; Di Pasquale, S

    2007-08-17

    Important pumice quarries are located on the island of Lipari (Italy) where an intense activity of extraction, transformation and trade of pumice takes place. Nevertheless, the finest fraction amounting to about 60% of mined pumice is discarded and disposed off in open-sky pits. This implies economic losses for mining industries and environmental problems for neighbouring villages. In order to find a sustainable use of this waste, we resumed and improved an old extractive process with aqueous sodium alkali, where a sodium silicate concentrated solution was produced together with an unextracted residue partially converted into zeolite P in Na+ form and now we are searching for suitable applications of this residue. In this paper, we relate about its use as a low cost water softening agent on the basis of results obtained from several tests both in batch systems and column. They show that, at room temperature, the residue works well with calcium and badly with magnesium, whereas, at 60 degrees C, also the affinity toward Mg ions increases to acceptable levels. Repeated regenerations of the residue with concentrated NaCl solutions do not appreciably compromise the performance. The limits for the possible use as water softening agent are defined. PMID:17320286

  15. Preparation of environmentally friendly alkylglucoside surfactants using zeolites as catalysts

    SciTech Connect

    Corma, A.; Iborra, S.; Miquel, S.; Primo, J.

    1996-07-01

    Acid zeolites were evaluated for glycosidation activity of D-glucose and n-butanol. Zeolites with high Si/Al ratios such as faujasite and beta are the most suitable catalysts. 24 refs., 7 figs., 5 tabs.

  16. 11. EASTERN END OF ZEOLITE BUILDING. NOTE DIAL TO LEFT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. EASTERN END OF ZEOLITE BUILDING. NOTE DIAL TO LEFT OF CLOCK GAUGING TOTAL ZEOLITE INFLUENT IN MILLIONS OF GALLONS PER DAY. - F. E. Weymouth Filtration Plant, 700 North Moreno Avenue, La Verne, Los Angeles County, CA

  17. Mineralogy of Presolar Silicate and Oxide Grains of Diverse Stellar Origins

    NASA Astrophysics Data System (ADS)

    Nguyen, Ann N.; Keller, Lindsay P.; Messenger, Scott

    2016-02-01

    We report the chemical and structural analysis of nine presolar silicate grains and one presolar oxide grain from the ungrouped chondrite Acfer 094 and the CR chondrite Queen Alexandra Range 99177. Oxygen isotopic analyses indicate that five of these grains condensed in the outflows of asymptotic giant branch (AGB) stars, four have supernova (SN) origins, and one grain likely has a nova origin. Transmission electron microscopy studies show that most of the grains are amorphous with widely varying non-stoichiometric chemical compositions. Three crystalline AGB grains were identified: a clinoenstatite-containing grain assemblage, a Fe-rich olivine grain, and a nanocrystalline enstatite grain encased in an amorphous silicate shell. An amorphous stoichiometric enstatite (MgSiO3) SN grain likely condensed as a crystal and was later rendered amorphous. We do not observe a systematic difference in the chemistries and mineralogies of presolar silicates from different stellar sources, suggesting that the grains formed under a similar range of conditions.

  18. Liquid crystalline composites containing phyllosilicates

    DOEpatents

    Chaiko, David J.

    2004-07-13

    The present invention provides phyllosilicate-polymer compositions which are useful as liquid crystalline composites. Phyllosilicate-polymer liquid crystalline compositions of the present invention can contain a high percentage of phyllosilicate while at the same time be transparent. Because of the ordering of the particles liquid crystalline composite, liquid crystalline composites are particularly useful as barriers to gas transport.

  19. Improved epitaxy of ultrathin praseodymia films on chlorine passivated Si(111) reducing silicate interface formation

    SciTech Connect

    Gevers, S.; Bruns, D.; Weisemoeller, T.; Wollschlaeger, J.; Flege, J. I.; Kaemena, B.; Falta, J.

    2010-12-13

    Ultrathin praseodymia films have been deposited on both Cl-passivated and nonpassivated Si(111) substrates by molecular beam epitaxy. Comparative studies on the crystallinity and stoichiometry are performed by x-ray photoelectron spectroscopy, x-ray standing waves, and x-ray reflectometry. On nonpassivated Si(111) an amorphous silicate film is formed. In contrast, praseodymia deposited on Cl-passivated Si(111) form a well-ordered crystalline film with cubic-Pr{sub 2}O{sub 3} (bixbyite) structure. The vertical lattice constant of the praseodymia film is increased by 1.4% compared to the bulk value. Furthermore, the formation of an extended amorphous silicate interface layers is suppressed and confined to only one monolayer.

  20. Fly ash zeolite catalyst support for Fischer-Tropsch synthesis

    NASA Astrophysics Data System (ADS)

    Campen, Adam

    This dissertation research aimed at evaluating a fly ash zeolite (FAZ) catalyst support for use in heterogeneous catalytic processes. Gas phase Fischer-Tropsch Synthesis (FTS) over a fixed-bed of the prepared catalyst/FAZ support was identified as an appropriate process for evaluation, by comparison with commercial catalyst supports (silica, alumina, and 13X). Fly ash, obtained from the Wabash River Generating Station, was first characterized using XRD, SEM/EDS, particle size, and nitrogen sorption techniques. Then, a parametric study of a two-step alkali fusion/hydrothermal treatment process for converting fly ash to zeolite frameworks was performed by varying the alkali fusion agent, agent:flyash ratio, fusion temperature, fused ash/water solution, aging time, and crystallization time. The optimal conditions for each were determined to be NaOH, 1.4 g NaOH: 1 g fly ash, 550 °C, 200 g/L, 12 hours, and 48 hours. This robust process was applied to the fly ash to obtain a faujasitic zeolite structure with increased crystallinity (40 %) and surface area (434 m2/g). Following the modification of fly ash to FAZ, ion exchange of H+ for Na+ and cobalt incipient wetness impregnation were used to prepare a FTS catalyst. FTS was performed on the catalysts at 250--300 °C, 300 psi, and with a syngas ratio H2:CO = 2. The HFAZ catalyst support loaded with 11 wt% cobalt resulted in a 75 % carbon selectivity for C5 -- C18 hydrocarbons, while methane and carbon dioxide were limited to 13 and 1 %, respectively. Catalyst characterization was performed by XRD, N2 sorption, TPR, and oxygen pulse titration to provide insight to the behavior of each catalyst. Overall, the HFAZ compared well with silica and 13X supports, and far exceeded the performance of the alumina support under the tested conditions. The successful completion of this research could add value to an underutilized waste product of coal combustion, in the form of catalyst supports in heterogeneous catalytic processes.

  1. Topological nonsymmorphic crystalline superconductors

    NASA Astrophysics Data System (ADS)

    Wang, Qing-Ze; Liu, Chao-Xing

    2016-01-01

    Topological superconductors possess a nodeless superconducting gap in the bulk and gapless zero energy modes, known as "Majorana zero modes," at the boundary of a finite system. In this work, we introduce a new class of topological superconductors, which are protected by nonsymmorphic crystalline symmetry and thus dubbed "topological nonsymmorphic crystalline superconductors." We construct an explicit Bogoliubov-de Gennes type of model for this superconducting phase in the D class and show how Majorana zero modes in this model are protected by glide plane symmetry. Furthermore, we generalize the classification of topological nonsymmorphic crystalline superconductors to the classes with time reversal symmetry, including the DIII and BDI classes, in two dimensions. Our theory provides guidance to search for new topological superconducting materials with nonsymmorphic crystal structures.

  2. The formation of molecular hydrogen on silicate dust analogs: The rotational distribution

    SciTech Connect

    Gavilan, L.; Lemaire, J. L.; Vidali, G.; Sabri, T.; Jger, C.

    2014-02-01

    Our laboratory experiments continue to explore how the formation of molecular hydrogen is influenced by dust and how dust thereby affects hydrogen molecules adsorbed on its surface. In Sabri et al., we present the preparation of nanometer-sized silicate grain analogs via laser ablation. These analogs illustrate extremes in structure (fully crystalline or fully amorphous grains), and stoichiometry (the forsterite and fayalite end-members of the olivine family). These were inserted in FORMOLISM, an ultra-high vacuum setup where they can be cooled down to ?5 K. Atomic beams are directed at these surfaces and the formation of new molecules is studied via REMPI(2+1) spectroscopy. We explored the rotational distribution (0 ? J'' ? 5) of v'' = 0 of the ground electronic state of H{sub 2}. The results of these measurements are reported here. Surprisingly, molecules formed and ejected from crystalline silicates have a cold (T {sub rot} ? 120 K) rotational energy distribution, while for molecules formed on and ejected from amorphous silicate films, the rotational temperature is ?310 K. These results are compared to previous experiments on metallic surfaces and theoretical simulations. Solid-state surface analysis suggests that flatter grains could hinder the 'cartwheel' rotation mode. A search for hot hydrogen, predicted as a result of H{sub 2} formation, hints at its production. For the first time, the rotational distribution of hydrogen molecules formed on silicate dust is reported. These results are essential to understanding the chemistry of astrophysical media containing bare dust grains.

  3. The Formation of Molecular Hydrogen on Silicate Dust Analogs: The Rotational Distribution

    NASA Astrophysics Data System (ADS)

    Gavilan, L.; Lemaire, J. L.; Vidali, G.; Sabri, T.; Jger, C.

    2014-02-01

    Our laboratory experiments continue to explore how the formation of molecular hydrogen is influenced by dust and how dust thereby affects hydrogen molecules adsorbed on its surface. In Sabri et al., we present the preparation of nanometer-sized silicate grain analogs via laser ablation. These analogs illustrate extremes in structure (fully crystalline or fully amorphous grains), and stoichiometry (the forsterite and fayalite end-members of the olivine family). These were inserted in FORMOLISM, an ultra-high vacuum setup where they can be cooled down to ~5 K. Atomic beams are directed at these surfaces and the formation of new molecules is studied via REMPI(2+1) spectroscopy. We explored the rotational distribution (0 <= J'' <= 5) of v'' = 0 of the ground electronic state of H2. The results of these measurements are reported here. Surprisingly, molecules formed and ejected from crystalline silicates have a cold (T rot ~ 120 K) rotational energy distribution, while for molecules formed on and ejected from amorphous silicate films, the rotational temperature is ~310 K. These results are compared to previous experiments on metallic surfaces and theoretical simulations. Solid-state surface analysis suggests that flatter grains could hinder the "cartwheel" rotation mode. A search for hot hydrogen, predicted as a result of H2 formation, hints at its production. For the first time, the rotational distribution of hydrogen molecules formed on silicate dust is reported. These results are essential to understanding the chemistry of astrophysical media containing bare dust grains.

  4. Molecular simulations and experimental studies of zeolites

    NASA Astrophysics Data System (ADS)

    Moloy, Eric C.

    Zeolites are microporous aluminosilicate tetrahedral framework materials that have symmetric cages and channels with open-diameters between 0.2 and 2.0 nm. Zeolites are used extensively in the petrochemical industries for both their microporosity and their catalytic properties. The role of water is paramount to the formation, structure, and stability of these materials. Zeolites frequently have extra-framework cations, and as a result, are important ion-exchange materials. Zeolites also play important roles as molecular sieves and catalysts. For all that is known about zeolites, much remains a mystery. How, for example, can the well established metastability of these structures be explained? What is the role of water with respect to the formation, stabilization, and dynamical properties? This dissertation addresses these questions mainly from a modeling perspective, but also with some experimental work as well. The first discussion addresses a special class of zeolites: pure-silica zeolites. Experimental enthalpy of formation data are combined with molecular modeling to address zeolitic metastability. Molecular modeling is used to calculate internal surface areas, and a linear relationship between formation enthalpy and internal surface areas is clearly established, producing an internal surface energy of approximately 93 mJ/m2. Nitrate bearing sodalite and cancrinite have formed under the caustic chemical conditions of some nuclear waste processing centers in the United States. These phases have fouled expensive process equipment, and are the primary constituents of the resilient heels in the bottom of storage tanks. Molecular modeling, including molecular mechanics, molecular dynamics, and density functional theory, is used to simulate these materials with respect to structure and dynamical properties. Some new, very interesting results are extracted from the simulation of anhydrous Na6[Si6Al 6O24] sodalite---most importantly, the identification of two distinct oxygen sites (rather than one), and formation of a new supercell. New calorimetric measurements of enthalpy are used to examine the energetics of the hydrosodalite family of zeolites---specifically, formation enthalpies and hydration energies. Finally, force-field computational methods begin the examination of water in terms of energetics, structure, and radionuclide containment and diffusion.

  5. Production of biofuel from waste cooking palm oil using nanocrystalline zeolite as catalyst: process optimization studies.

    PubMed

    Taufiqurrahmi, Niken; Mohamed, Abdul Rahman; Bhatia, Subhash

    2011-11-01

    The catalytic cracking of waste cooking palm oil to biofuel was studied over different types of nano-crystalline zeolite catalysts in a fixed bed reactor. The effect of reaction temperature (400-500 C), catalyst-to-oil ratio (6-14) and catalyst pore size of different nanocrystalline zeolites (0.54-0.80 nm) were studied over the conversion of waste cooking palm oil, yields of Organic Liquid Product (OLP) and gasoline fraction in the OLP following central composite design (CCD). The response surface methodology was used to determine the optimum value of the operating variables for maximum conversion as well as maximum yield of OLP and gasoline fraction, respectively. The optimum reaction temperature of 458 C with oil/catalyst ratio=6 over the nanocrystalline zeolite Y with pore size of 0.67 nm gave 86.4 wt% oil conversion, 46.5 wt% OLP yield and 33.5 wt% gasoline fraction yield, respectively. The experimental results were in agreement with the simulated values within an experimental error of less than 5%. PMID:21924606

  6. Hydrogen isotope separation using molecular sieve of synthetic zeolite 3A

    SciTech Connect

    Kotoh, K.; Kimura, K.; Nakamura, Y.; Kudo, K.

    2008-07-15

    It is known that hydrogen isotope molecules can be adsorbed easily onto synthetic zeolite 4A, 5A, and 13X at the liquid-nitrogen temperature of 77.4 K. We show here that hydrogen and deuterium are not adsorptive onto zeolite 3A at the same temperature. This phenomenon is explained by assuming the molecular sieve function in zeolite-3A-crystalline lattice structure. From a series of pseudo-isobaric experiments, it is also shown that the sieving phenomenon appears in a range above 77.4 K. This behavior is interpreted as resulting on the dependence of sieve's mesh size on temperature, where the sieving effect is considered to appear at a certain temperature. In this interpretation, an isotopic difference between hydrogen and deuterium is suggested to exist in the sieving effect appearance temperatures. This is endorsed in the result of pseudo-isobaric experiments. This temperature deference is very significant because that indicates the possibility of an effective method of hydrogen isotope separation. This possibility is verified through an experimental series of adsorption-desorption with a mixture of H{sub 2} and D{sub 2}, where the gas samples adsorbed through the sieve operated at intentionally selected temperatures are isolated and then analyzed. The result demonstrates remarkable values of isotope separation factor. (authors)

  7. The behaviour of water confined in zeolites: molecular dynamics simulations versus experiment

    NASA Astrophysics Data System (ADS)

    Demontis, P.; Guln-Gonzlez, J.; Masia, M.; Suffritti, G. B.

    2010-07-01

    In order to study the behaviour of water adsorbed in zeolites, which are microporous crystalline aluminosilicates, whose channels and cavities of nanometric dimensions can host many different molecules, we developed a sophisticated empirical potential for water, including the full flexibility of the molecule and the correct response to the electric field generated by the cations and by the charged atoms of the aluminosilicate framework. The reproduction of experimental data by our potential model is similar or even better than that obtained from the first principles methods. The results of molecular dynamics simulations of water confined in a variety of zeolites (worm-like clusters in silicalite, spherical nanoclusters in zeolite A and ice-like nanotubes in AlPO4-5 and SSZ-24) at different temperatures and coverage (loading) are discussed in connection with the experimental data, whose overall good reproduction encourages the attempt of an atomic-scale description of structural and dynamical phenomena occurring in confined water, in particular in the supercooled regime. The results are also compared with simulations and experimental data on bulk water.

  8. Catalytically active and hierarchically porous SAPO-11 zeolite synthesized in the presence of polyhexamethylene biguanidine.

    PubMed

    Liu, Yan; Qu, Wei; Chang, Weiwei; Pan, Shuxiang; Tian, Zhijian; Meng, Xiangju; Rigutto, Marcello; van der Made, Alexander; Zhao, Lan; Zheng, Xiaoming; Xiao, Feng-Shou

    2014-03-15

    Hierarchically porous SAPO-11 zeolite (H-SAPO-11) is rationally synthesized from a starting silicoaluminophosphate gel in the presence of polyhexamethylene biguanidine as a mesoscale template. The sample is well characterized by XRD, N2 sorption, SEM, TEM, NMR, XPS, NH3-TPD, and TG techniques. The results show that the sample obtained has good crystallinity, hierarchical porosity (mesopores at ca. 10 nm and macropores at ca. 50-200 nm), high BET surface area (226 m(2)/g), large pore volume (0.25 cm(3)/g), and abundant medium and strong acidic sites (0.36 mmol/g). After loading Pt (0.5 wt.%) on H-SAPO-11 by using wet impregnation method, catalytic hydroisomerization tests of n-dodecane show that the hierarchical Pt/SAPO-11 zeolite exhibits high conversion of n-dodecane and enhanced selectivity for branched products as well as reduced selectivity for cracking products, compared with conventional Pt/SAPO-11 zeolite. This phenomenon is reasonably attributed to the presence of hierarchical porosity, which is favorable for access of reactants on catalytically active sites. The improvement in catalytic performance in long-chain paraffin hydroisomerization over Pt/SAPO-11-based catalyst is of great importance for its industrial applications in the future. PMID:24461835

  9. Probing Interstellar Silicate Dust Grain Properties in Quasar Absorption Systems at Redshifts z<1.4

    NASA Astrophysics Data System (ADS)

    Aller, M.; Kulkarni, V. P.; York, D. G.; Welty, D. E.; Vladilo, G.; Som, D.

    Absorption lines in the spectra of distant quasars whose sightlines serendipitously pass through foreground galaxies provide a valuable tool to simultaneously probe the dust and gas compositions of the interstellar medium (ISM) in galaxies. In particular, the damped and sub-damped Lyman- ? (DLA/sub-DLA) absorbers trace gas-rich galaxies, independent of the intrinsic luminosities or star-formation rates of the associated galaxy stellar populations. The first evidence of silicate dust in a quasar absorption system was provided through our detection of the 10 m silicate feature in the z=0.52 DLA absorber toward the quasar AO 0235+164. We present results from 2 follow-up programs using archival Spitzer Space Telescope infrared spectra to study the interstellar silicate dust grain properties in a total of 13 quasar absorption systems at 0.1 < z < 1.4. We find clear detections of the 10 m silicate feature in the quasar absorption systems studied. In addition, we also detect the 18 m silicate feature in the sources with adequate spectral coverage. We find variations in the breadth, peak wavelength, and substructure of the 10 m interstellar silicate absorption features among the absorbers. This suggests that the silicate dust grain properties in these distant galaxies may differ relative to one another, and relative to those in the Milky Way. We also find suggestions in several sources, based on comparisons with laboratory-derived profiles from the literature, that the silicate dust grains may be significantly more crystalline than those in the amorphous Milky Way ISM. This is particularly evident in the z=0.89 absorber toward the quasar PKS 1830-211, where substructure near 10 m is consistent with a crystalline olivine composition. If confirmed, these grain property variations may have implications for both dust and galaxy evolution over the past 9 Gyrs, and for the commonly-made assumption that highredshift dust is similar to local dust. We also discuss indications of trends between silicate dust absorption strength and both carbonaceous dust properties and gas-phase metal properties, such as the gas velocity spread, determined from UV/optical spectra.

  10. Synthesis of novel perfluoroalkylglucosides on zeolite and non-zeolite catalysts.

    PubMed

    Nowicki, Janusz; Mokrzycki, ?ukasz; Sulikowski, Bogdan

    2015-01-01

    Perfluoroalkylglucosides comprise a very important class of fluorine-containing surfactants. These compounds can be synthesized by using the Fisher reaction, starting directly from glucose and the required perfluoroalcohols. We wish to report on the use of zeolite catalysts of different structure and composition for the synthesis of perfluoroalkylglucosides when using glucose and 1-octafluoropentanol as substrates. Zeolites of different pore architecture have been chosen (ZSM-5, ZSM-12, MCM-22 and Beta). Zeolites were characterized by XRD, nitrogen sorption, scanning electron microscopy (SEM) and solid-state 27Al MAS NMR spectroscopy. The activity of the zeolite catalysts in the glycosidation reaction was studied in a batch reactor at 100 C below atmospheric pressure. The performance of zeolites was compared to other catalysts, an ion-exchange resin (Purolite) and a montmorillonite-type layered aluminosilicate. The catalytic performance of zeolite Beta was the highest among the zeolites studied and the results were comparable to those obtained over Purolite and montmorillonite type catalysts. PMID:25856063

  11. Zeolites as catalysts in oil refining.

    PubMed

    Primo, Ana; Garcia, Hermenegildo

    2014-11-21

    Oil is nowadays the main energy source and this prevalent position most probably will continue in the next decades. This situation is largely due to the degree of maturity that has been achieved in oil refining and petrochemistry as a consequence of the large effort in research and innovation. The remarkable efficiency of oil refining is largely based on the use of zeolites as catalysts. The use of zeolites as catalysts in refining and petrochemistry has been considered as one of the major accomplishments in the chemistry of the XXth century. In this tutorial review, the introductory part describes the main features of zeolites in connection with their use as solid acids. The main body of the review describes important refining processes in which zeolites are used including light naphtha isomerization, olefin alkylation, reforming, cracking and hydrocracking. The final section contains our view on future developments in the field such as the increase in the quality of the transportation fuels and the coprocessing of increasing percentage of biofuels together with oil streams. This review is intended to provide the rudiments of zeolite science applied to refining catalysis. PMID:24671148

  12. Italian zeolitized rocks of technological interest

    NASA Astrophysics Data System (ADS)

    de'Gennaro, M.; Langella, A.

    1996-09-01

    Large areas of Italian territory are covered by thick and widespread deposits of zeolite-bearing volcaniclastic products. The main zeolites are phillipsite and chabazite spread over the whole peninsula, and clinoptilolite recorded only in Sardinia. A trachytic to phonolitic glassy precursor accounts for the formation of the former zeolites characterized by low Si/Al ratios (?3.00), while clinoptilolite is related to more acidic volcanism. The genesis of most of these zeolitized deposits is linked to pyroclastic flow emplacement mechanisms characterized by quite high temperatures and by the presence of abundant fluids. The main utilization of these materials has been and still is as dimension stones in the building industry. Currently, limited amounts are also employed in animal farming (dietary supplement, pet litter and manure deodorizer) and in agriculture as soil improvement and slow-release fertilizers. New fields of application have been proposed for these products on account of their easy availability, very low cost, their high-grade zeolites (50 70%), and good technological features such as high cation exchange capacities and adsorption properties.

  13. Development of Desiccant System using Wakkanai Siliceous Shale

    NASA Astrophysics Data System (ADS)

    Nakabayashi, Saya; Nagano, Katsunori; Nakamura, Makoto; Togawa, Junya; Kurokawa, Asami

    The aim of this study is to develop a desiccant system using Wakkanai siliceous shale. A honeycombed desiccant rotor containing this shale's powder and chlorides was made and evaluated. However a specific surface area and a pore volume were smaller than a silica-gel rotor or a zeolite rotor, the maximum amount of water adsorption was twice as other rotors. We have verified the function of this desiccant rotor concerning adsorption and desorption of moisture from the draft experiments. The rotor containing the shale could adsorb moisture stably in the cyclic test, and be regenerated by 40C air under this experimental condition. This means that the exhaust heat from the heat pump can be used for regenerating rotor. Furthermore, the numerical simulation was carried out on the assumption that this rotor was used for a dehumidification for the residential air conditioning in Tokyo. This rotor could adsorb 37.1% moisture of the required dehumidification amount for the hottest day in 2008. When we employed a pre-cooling before dehumidification, the amount of adsorption increased to 66.2%.

  14. [Research on the mineral phase and component of non-crystalline and nano-crystalline corrosion products on bronzes unearthed from Shang Tomb in Xingan].

    PubMed

    Cheng, Xiao-lin; Pan, Lu

    2012-05-01

    The patinas on bronzes in Shang Tomb of Xingan were powdery, pale green, which were more like "bronze disease", but the mineral composition of patinas was not paratacamite or atacamite. Micro X-ray diffraction (XRD) and high performance transmission electroscope (HTEM) showed that the patinas were mainly composed of non-crystalline and nano-crystalline SnO2, and the size of nano-crystalline particle was in the range of 4-5.7 nm; Moreover, the energy-dispersive X-ray spectrometry showed that element tin is the primary ingredient of the sample, as well as little copper, silicon, lead and iron were detected. By studying the crystal lattice stripe image of the nanometer SnO2, it was deduced that the chemical formula of nano-crystalline SnO2 did not include other elements; The Raman spectrum of the sample showed that there were not any characteristic peaks of SnO2, the spectrum was more like non-crystalline SnO2, and the weak and broad peak of 973 cm(-1) indicated that the sample may contain silicate grains, It was inferred that little of copper, silicon, lead and iron should exist in the form of non-crystalline silicate particles. PMID:22827070

  15. Catalytic crystallization of ices by small silicate smokes at temperatures less than 20K

    NASA Technical Reports Server (NTRS)

    Moore, M.; Ferrante, R.; Hudson, R.; Tanabe, T.; Nuth, J.

    1993-01-01

    Samples of methanol and water ices condensed from the vapor onto aluminum substrates at low temperatures (below approximately 80 K) form amorphous ices; annealing at temperatures in excess of 140-155 K is usually required to convert such amorphous samples to crystalline ices. However, we have found that when either methanol or water vapor is deposited on to aluminum substrates that have been coated with a thin (0.1-0.5 mm) layer of amorphous silicate smoke, the ices condense in crystalline form. We believe that crystalline ice forms as the result of energy liberated at the ice/silicate interface perhaps due to weak bonding of the ice at defect sites on the grains and the very high surface to volume ratio and defect density of these smokes. Annealing of amorphous water ice mixed with more volatile components such as methane, carbon monoxide, etc., has been suggested as an efficient way to produce clatherates in the outer solar nebula and thus explain the volatile content of comets and icy satellites of the outer planets. This hypothesis may need to be re-examined if amorphous ice does not form on cold silicate grains.

  16. Adsorption kinetics of silicic acid on akaganeite.

    PubMed

    Naren, Gaowa; Ohashi, Hironori; Okaue, Yoshihiro; Yokoyama, Takushi

    2013-06-01

    As part of a series of studies on the interaction between ferric ions and silicic acid in the hydrosphere, the adsorption of silicic acid on akaganeite was investigated kinetically at various pH values. The adsorption of silicic acid increased with increasing pH over an initial pH range of 4-11.5. In the kinetic experiment, the Cl(-) was released from akaganeite much faster than silicic acid was adsorbed. From this result, we concluded that chloride ions bound on the surface of akaganeite are released and Fe-OH or Fe-O(-) sites are formed, which then acts as an adsorption site for silicic acid. The uptake mechanism of silicic acid by akaganeite is significantly different from that by schwertmannite, despite the presence of the same tunnel structure. PMID:23538050

  17. Preparation, Processing, and Characterization of Oriented Polycrystalline Zeolite and Aluminophosphate Membranes

    NASA Astrophysics Data System (ADS)

    Stoeger, Jared Andrew

    Since the advent of zeolite membranes, speculation on their industrial applicability has been closely monitored, although widespread commercialization has been hampered by limitations in fabrication and post-synthesis processing. Economical, energy-efficient technology breakthroughs require an evaluation of a range of material candidates which show robustness and reliability. Straightforward manufacturing techniques should be devised to generate thousands of square meters of membrane area; however, this demands control of structural characteristics on the scale of nanometers. As described in this dissertation, the path forward will be forged by exploiting the intrinsic crystalline properties of zeolites or aluminophosphates for the next advancement in membrane technology. A facile method is described for the preparation of silicalite-1 (MFI zeolite type) membranes using the secondary growth technique on symmetric porous stainless steel tubes. Activation through rapid thermal processing (RTP), a lamp-based heat-treatment process used as a critical fabrication step in silicon integrated circuit manufacturing, is proven to reduce the density of non-zeolitic transport pathways which are detrimental to high-resolution molecular sieving. RTP-treated membranes are shown to have enhanced performance in the binary separation of vapor-phase isomers (p-/o-xylene), gas-phase isomers (n-/i-butane), and alcohol/water when compared to membranes activated at a much slower heating rate but otherwise similarly-prepared. The performance is discussed in the context of the market potential for industrially-attractive separations: the recovery of p-xylene from an isomeric mixture or alcohol biofuels from aqueous post-fermentation streams. Hydrothermal growth techniques for the preparation and characterization of continuous aluminophosphate (AFI zeolite type) membranes with a preferential crystallographic alignment on porous alpha-Al2O3 disc supports are demonstrated. A mechanism is proposed for flake-like crystal formation in the early stages of in-plane crystalline intergrowth between oriented columnar crystals by electric heating. It is shown that elevated temperatures induce a phase transformation to a densified aluminophosphate phase despite framework metal substitution or alternative heat-treatment conditions. Additionally, stability and membrane characteristics following in situ microwave growth using a TiO2-coated support are examined. Indications of improved quality validate the candidacy of the microwave-grown membranes with regard to the potential for carbon nanotube synthesis in the aligned one-dimensional channels for high flux, high separation factor membrane fabrication.

  18. Silicate stabilization studies in propylene glycol

    SciTech Connect

    Schwartz, S.A.

    1999-08-01

    In most North American and many European coolant formulations, the corrosion inhibition of heat-rejecting aluminum surfaces is provided by alkali metal silicates. But, their tendency towards polymerization, leading to gelation and/or precipitation, can reduce the effectiveness of a coolant. This paper presents the results of experiments which illustrate formulation-dependent behavior of inorganic silicate in propylene glycol compositions. Specific examples of the effects of glycol matrix, stabilizer type, and hard water on silicate stabilization are provided.

  19. Substitution clustering in a non-stoichiometric celsian synthesized by the thermal transformation of barium exchanged zeolite X

    SciTech Connect

    Clayden, Nigel J. . E-mail: N.Clayden@uea.ac.uk; Esposito, Serena; Ferone, Claudio; Pansini, Michele

    2006-07-15

    The thermal transformation of Ba exchanged zeolite X to celsian has been studied by {sup 27}Al and {sup 29}Si MAS NMR spectroscopy. Evidence for the degradation of the zeolite framework is present in the {sup 29}Si NMR spectra after thermal treatment at 850 deg. C. Confirmation is provided by the {sup 29}Si NMR data that synthesis of celsian via the decomposition of Ba exchanged zeolite leads to a single defect phase. Clustering of the isomorphous replacement of aluminium by silicon must occur to explain the observed {sup 29}Si chemical shifts. The {sup 27}Al NMR data show distorted aluminium co-ordination sites upon the thermal transformation of Ba exchanged zeolite X. The distortions present in the amorphous matrix are greater than those present in the monoclinic and hexagonal crystalline phases of celsian. - Graphical abstract: Monte Carlo simulation of the Q {sub 4}(mAl) silicon connectivity in the {alpha}-hexagonal celsian lattice, for a Si/Al ratio of 1:1. Si atoms are shown in yellow and the Al atoms in black.

  20. Cumulate Fragments in Silicic Ignimbrites

    NASA Astrophysics Data System (ADS)

    Bachmann, O.; Ellis, B. S.; Wolff, J.

    2014-12-01

    Increasingly, studies are concluding that silicic ignimbrites are the result of the amalgamation of multiple discrete magma batches. Yet the existence of discrete batches presents a conundrum for magma generation and storage; if silicic magma batches are not generated nearly in situ in the upper crust, they must traverse, and reside within, a thermally hostile environment with large temperature gradients, resulting in low survivability in their shallow magmatic hearths. The Snake River Plain (Idaho, USA) is a type example of this 'multi-batch' assembly with ignimbrites containing multiple populations of pyroxene crystals, glass shards, and crystal aggregates. The ubiquitous crystal aggregates hint at a mechanism to facilitate the existence of multiple, relatively small batches of rhyolite in the upper crust. These aggregates contain the same plagioclase, pyroxene, and oxide mineral compositions as single phenocrysts of the same minerals in their host rocks, but they have significantly less silicic bulk compositions and lack quartz and sanidine, which occur as single phenocrysts in the deposits. This implies significant crystallization followed by melt extraction from mushy reservoir margins. The extracted melt then continues to evolve (crystallizing sanidine and quartz) while the melt-depleted margins provide an increasingly rigid and refractory network segregating the crystal-poor batches of magma. The hot, refractory, margins insulate the crystal-poor lenses, allowing (1) extended residence in the upper crust, and (2) preservation of chemical heterogeneities among batches. In contrast, systems that produce cumulates richer in low-temperature phases (quartz, K-feldspars, and/or biotite) favour remelting upon recharge, leading to less segregation of eruptible melt pockets and the formation of gradationally zoned ignimbrites. The occurrence of similar crystal aggregates from a variety of magmatic lineages suggests the generality of this process.

  1. A Site-Isolated Iridium Diethylene Complex Supported on Highly Dealuminated Y Zeolite: Synthesis And Characterization

    SciTech Connect

    Uzun, A.; Bhirud, V.A.; Kletnieks, P.W.; Haw, J.F.; Gates, B.C.

    2009-06-04

    Highly dealuminated Y zeolite-supported mononuclear iridium complexes with reactive ethylene ligands were synthesized by chemisorption of Ir(C{sub 2}H{sub 4}){sub 2}(C{sub 5}H{sub 7}O{sub 2}). The resultant structure and its treatment in He, CO, ethylene, and H2 were investigated with infrared (IR) and extended X-ray absorption fine structure (EXAFS) spectroscopies. The IR spectra show that Ir(C{sub 2}H{sub 4}){sub 2}(C{sub 5}H{sub 7}O{sub 2}) reacted readily with surface OH groups of the zeolite, leading to the removal of C{sub 5}H{sub 7}O{sub 2} ligands and the formation of supported mononuclear iridium complexes, confirmed by the lack of Ir-Ir contributions in the EXAFS spectra. The EXAFS data show that each Ir atom was bonded to four carbon atoms at an average distance of 2.10 {angstrom}, consistent with the presence of two ethylene ligands per Ir atom and in agreement with the IR spectra indicating {pi}-bonded ethylene ligands. The EXAFS data also indicate that each Ir atom was bonded to two oxygen atoms of the zeolite at a distance of 2.15 {angstrom}. The supported iridium-ethylene complex reacted with H{sub 2} to give ethane, and it also catalyzed ethylene hydrogenation at atmospheric pressure and 294 K. Treatment of the sample in CO led to the formation of Ir(CO){sub 2} complexes bonded to the zeolite. The sharpness of the V{sub CO} bands indicates a high degree of uniformity of these complexes on the support. The iridium-ethylene complex on the crystalline zeolite support is inferred to be one of the most nearly uniform supported metal complex catalysts. The results indicate that it is isostructural with a previously reported rhodium complex on the same zeolite; thus, the results are a start to a family of analogous, structurally well-defined supported metal complex catalysts.

  2. Effect of silicate ions on electrode overvoltage

    NASA Technical Reports Server (NTRS)

    Gras, J. M.; Seite, C.

    1979-01-01

    The influence of the addition of a silicate to a caustic solution (KOH) is studied in order to determine the degree to which silicates inhibit the corrosion of chrysotile under conditions of electrolysis at working temperatures of 100 C and above. In an alkaline solution containing various silicate concentrations, current density was increased and electrode overvoltage was measured. Results show that silicate ion concentrations in the electrolyte increase with temperature without effecting electrochemical performance up to 115 C at 700 MA/sqcm. At this point the concentration is about 0.5 g Si/100 g KOH. Beyond this limit, electrolytic performance rapidly degenerates due to severe oxidation of the electrodes.

  3. Tailoring polymer properties with layered silicates

    NASA Astrophysics Data System (ADS)

    Xu, Liang

    Polymer layered silicate nanocomposites have found widespread applications in areas such as plastics, oil and gas production, biomedical, automotive and information storage, but their successful commercialization critically depends on consistent control over issues such as complete dispersion of layered silicate into the host polymer and optimal interaction between the layered silicates and the polymers. Polypropylene is a commercially important polymer but usually forms intercalated structures with organically modified layered silicate upon mixing, even it is pre-treated with compatibilizing agent such as maleic anhydride. In this work, layered silicate is well dispersed in ammonium modified polypropylene but does not provide sufficient reinforcement to the host polymer due to poor interactions. On the other hand, interactions between maleic anhydride modified polypropylene and layered silicate are fine tuned by using a small amount of maleic anhydride and mechanical strength of the resultant nanocomposites are significantly enhanced. In particular, the melt rheological properties of layered silicate nanocomposites with maleic anhydride functionalized polypropylene are contrasted to those based on ammonium-terminated polypropylene. While the maleic anhydride treated polypropylene based nanocomposites exhibit solid-like linear dynamic behavior, consistent with the formation of a long-lived percolated nanoparticle network, the single-end ammonium functionalized polypropylene based nanocomposites demonstrated liquid-like behavior at comparable montmorillonite concentrations. The differences in the linear viscoelasticity are attributed to the presence of bridging interaction in maleic anhydride functionalized nanocomposites, which facilitates formation of a long-lived silicate network mediated by physisorbed polymer chains. Further, the transient shear stress of the maleic anhydride functionalized nanocomposites in start-up of steady shear is a function of the shear strain alone and the steady shear response is consistent with that of non-Brownian systems. In addition, the weak dependence on the steady shear stress of the steady first normal stress difference suggests that the polymer chain mediated silicate network contributes to such unique flow behavior. This dissertation also explores the following aspects. To effectively achieve a stable and exfoliated silicate system, polystyrene tethered layered silicates via nitroxide mediated polymerization are dispersed in a monodisperse lamellar polystyrene polyisoprene diblock copolymer and serve as structure-direct agent, creating nearly oriented structures. In addition, small angle scattering techniques are utilized to examine the degree of dispersion of layered silicate in organic solvents, where the scattering data are fitted to various physical meaningful models, thus providing detailed information on the degree of dispersion and silicate dimensions. Finally, spectroscopic properties of the fluorescent dyes are altered upon adsorption to the silicate surface, providing information about the local environment at the interface and possibly the degree of silicate dispersion. The interactions between dyes, silicates and solvents are examined by fluorescence and UV-Vis spectroscopy.

  4. Crystallization of zeolite A: a spectroscopic study

    SciTech Connect

    Dutta, P.K.; Shieh, D.C.

    1986-05-22

    The transformation of aluminosilicate gel to zeolite A was investigated by Raman spectroscopy, supported by x-ray diffraction and NMR measurements. The gel, even though amorphous, has a structure consisting of predominantly four-membered rings connected in a random fashion. It is considerably depolymerized, consisting of Si atoms with one and two nonbonded oxygen atoms. For the transformation of this gel to zeolite A to proceed, it is essential to have Al(OH)/sub 4//sup -/ species in solution. During the nucleation period, the gel reorganizes its structure by interaction with these Al(OH)/sub 4//sup -/ ions and forms nuclei of zeolite A. The crystallization curve obtained by Raman spectroscopy closely resembles that from x-ray diffraction.

  5. Spectroscopic characterization of bismuth embedded Y zeolites

    NASA Astrophysics Data System (ADS)

    Sun, Hong-Tao; Sakka, Yoshio; Miwa, Yuji; Shirahata, Naoto; Fujii, Minoru; Gao, Hong

    2010-09-01

    Bismuth embedded Y zeolites were studied by using UV-vis- near infrared (NIR) diffuse reflectance, Raman, and steady-state NIR photoluminescence spectroscopy. The results suggest that Bi53+ and Bi+ active centers coexist in the dehydrated and hydrated zeolite framework, both of which contribute to NIR emission. Furthermore, it was revealed that the high-temperature annealing leads to the formation of Bi2O3 clusters, which act as blocks for selectively closing down the "in-out windows" of H2O and O2 molecules in the zeolites. It is believed that these materials can find a wide array of applications as active media of broadly tunable micro or nano-optical sources.

  6. Hydrogen Purification Using Natural Zeolite Membranes

    NASA Technical Reports Server (NTRS)

    DelValle, William

    2003-01-01

    The School of Science at Universidad del Turabo (UT) have a long-lasting investigation plan to study the hydrogen cleaning and purification technologies. We proposed a research project for the synthesis, phase analysis and porosity characterization of zeolite based ceramic perm-selective membranes for hydrogen cleaning to support NASA's commitment to achieving a broad-based research capability focusing on aerospace-related issues. The present study will focus on technology transfer by utilizing inorganic membranes for production of ultra-clean hydrogen for application in combustion. We tested three different natural zeolite membranes (different particle size at different temperatures and time of exposure). Our results show that the membranes exposured at 900 C for 1Hr has the most higher permeation capacity, indicated that our zeolite membranes has the capacity to permeate hydrogen.

  7. Dielectric Property of Silicate-Doped CaBi4Ti4O15 Thin Films

    NASA Astrophysics Data System (ADS)

    Ogawa, Shota; Kondoh, Yohta; Kimura, Junichi; Funakubo, Hiroshi; Uchida, Hiroshi

    2012-09-01

    Thin films of silicate-doped CaBi4Ti4O15 were fabricated to enhance the insulating property of one-axis-oriented CaBi4Ti4O15 films under an applied electric field. The crystalline phase of CaBi4Ti4O15, a type of bismuth layer-structured dielectric (BLSD) compound, was successfully grown on (100)LaNiO3/(111)Pt/TiO2/(100)Si with the preferential orientation of the (001) plane by the addition of bismuth silicate with a nominal composition of Bi12SiO20 up to 1.00%. The crystallographic orientation of the (001)BLSD plane normal to the substrate surface was degraded by excessive bismuth silicate addition above 1.50%. The breakdown electric field was increased by bismuth silicate addition up to 2.00% without the degraded relative dielectric permittivity (?r) of approximately 230. The bismuth silicate could precipitate between the grain boundaries in the CaBi4Ti4O15 films without an interface reaction or a solid solution that enhances the insulating behavior of the BLSD films.

  8. Crystal engineering of zeolites with graphene

    NASA Astrophysics Data System (ADS)

    Gebhardt, Paul; Pattinson, Sebastian W.; Ren, Zhibin; Cooke, David J.; Elliott, James A.; Eder, Dominik

    2014-06-01

    Achieving control over the morphology of zeolite crystals at the nanoscale is crucial for enhancing their performance in diverse applications including catalysis, sensors and separation. The complexity and sensitivity of zeolite synthesis processes, however, often make such control both highly empirical and difficult to implement. We demonstrate that graphene can significantly alter the morphology of titanium silicalite (TS-1) particles, in particular being able to reduce their dimensions from several hundreds to less than 10 nm. Through electron microscopy and molecular mechanics simulations we propose a mechanism for this change based on the preferential interaction of specific TS-1 surfaces with benzyl-alcohol-mediated graphene. These findings suggest a facile new means of controlling the zeolite morphology and thereby also further demonstrate the potential of graphene in hybrid materials. Moreover, the generality of the mechanism points the way to a new avenue of research in using two-dimensional materials to engineer functional inorganic crystals.Achieving control over the morphology of zeolite crystals at the nanoscale is crucial for enhancing their performance in diverse applications including catalysis, sensors and separation. The complexity and sensitivity of zeolite synthesis processes, however, often make such control both highly empirical and difficult to implement. We demonstrate that graphene can significantly alter the morphology of titanium silicalite (TS-1) particles, in particular being able to reduce their dimensions from several hundreds to less than 10 nm. Through electron microscopy and molecular mechanics simulations we propose a mechanism for this change based on the preferential interaction of specific TS-1 surfaces with benzyl-alcohol-mediated graphene. These findings suggest a facile new means of controlling the zeolite morphology and thereby also further demonstrate the potential of graphene in hybrid materials. Moreover, the generality of the mechanism points the way to a new avenue of research in using two-dimensional materials to engineer functional inorganic crystals. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr00320a

  9. Studies of anions sorption on natural zeolites.

    PubMed

    Barczyk, K; Mozgawa, W; Krl, M

    2014-12-10

    This work presents results of FT-IR spectroscopic studies of anions-chromate, phosphate and arsenate - sorbed from aqueous solutions (different concentrations of anions) on zeolites. The sorption has been conducted on natural zeolites from different structural groups, i.e. chabazite, mordenite, ferrierite and clinoptilolite. The Na-forms of sorbents were exchanged with hexadecyltrimethylammonium cations (HDTMA(+)) and organo-zeolites were obtained. External cation exchange capacities (ECEC) of organo-zeolites were measured. Their values are 17mmol/100g for chabazite, 4mmol/100g for mordenite and ferrierite and 10mmol/100g for clinoptilolite. The used initial inputs of HDTMA correspond to 100% and 200% ECEC of the minerals. Organo-modificated sorbents were subsequently used for immobilization of mentioned anions. It was proven that aforementioned anions' sorption causes changes in IR spectra of the HDTMA-zeolites. These alterations are dependent on the kind of anions that were sorbed. In all cases, variations are due to bands corresponding to the characteristic Si-O(Si,Al) vibrations (occurring in alumino- and silicooxygen tetrahedra building spatial framework of zeolites). Alkylammonium surfactant vibrations have also been observed. Systematic changes in the spectra connected with the anion concentration in the initial solution have been revealed. The amounts of sorbed CrO4(2-), AsO4(3-) and PO4(3-) ions were calculated from the difference between their concentrations in solutions before (initial concentration) and after (equilibrium concentration) sorption experiments. Concentrations of anions were determined by spectrophotometric method. PMID:25002191

  10. Natural zeolite reactivity towards ozone: the role of compensating cations.

    PubMed

    Valds, Hctor; Alejandro, Serguei; Zaror, Claudio A

    2012-08-15

    Among indoor pollutants, ozone is recognised to pose a threat to human health. Recently, low cost natural zeolites have been applied as alternative materials for ozone abatement. In this work, the effect of compensating cation content of natural zeolite on ozone removal is studied. A Chilean natural zeolite is used here as starting material. The amount of compensating cations in the zeolite framework was modified by ion exchange using an ammonium sulphate solution (0.1 mol L(-1)). Characterisation of natural and modified zeolites were performed by X-ray powder diffraction (XRD), nitrogen adsorption at 77K, elemental analysis, X-ray fluorescence (XRF), thermogravimetric analysis coupled with mass spectroscopy (TGA-MS), and temperature-programmed desorption of ammonia (NH(3)-TPD). Ozone adsorption and/or decomposition on natural and modified zeolites were studied by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Results show that the zeolite compensating cation content affects ozone interaction with zeolite active sites. Ammonium ion-exchange treatments followed by thermal out-gassing at 823 K, reduces ozone diffusion resistance inside the zeolite framework, increasing ozone abatement on zeolite surface active sites. Weak and strong Lewis acid sites of zeolite surface are identified here as the main active sites responsible of ozone removal. PMID:22633878

  11. Phonolite-hosted zeolite deposits in the Kaiserstuhl Volcanic Complex, Germany

    NASA Astrophysics Data System (ADS)

    Weisenberger, Tobias; Spürgin, Simon

    2014-05-01

    Several subvolcanic phonolitic intrusions occur within the Miocene Kaiserstuhl Volcanic Complex (KVC) located in the central-southern segment of the Upper Rhine Graben, which is part of the European Cenozoic Rift System. Hydrothermally altered phonolitic rocks are of economic interest, due to the high (>40 wt%) zeolite content, which accounts for the remarkable zeolitic physicochemical properties of the ground rock. These properties have widespread industrial application in water softening, catalysis, remediation of soils and soil quality, wastewater treatment, and as additive in the cement industry. Currently the largest phonolite intrusion Fohberg is active in mining, located in the eastern part of the KVC. The Endhale phonolite, approximately 1.5 km to the north marks a further deposit currently under exploration. Both phonolites are hosted in Tertiary sedimentary units. The aim of this study is to carry out a new mineralogical and geochemical data a) to evaluate the manifestation of hydrothermal alteration of the Fohberg and Endhale phonolitic intrusions, and b) to constrain the physical and chemical properties of the fluids, which promoted hydrothermal replacement of primary igneous minerals. The high degree of alteration is in contrast to the only slightly altered Kirchberg phonolite in the western KVC. The alkaline intrusive bodies are characterized by the primary mineralogy: feldspathoid mineral, K-feldspar, aegirine-augite, wollastonite, and andradite, with additional REE-minerals (e.g. götzenite). Fluid-induced re-equilibration of feldspathoid minerals and wollastonite caused breakdown to a set of secondary phases. Feldspathoid minerals are totally replaced by secondary phases including various zeolite species, calcite, and barite. Wollastonite breakdown results in the formation of various zeolites, calcite, pectolite, sepiolite, and quartz. The large variability of secondary minerals indicates a heterogenic fluid composition throughout the phonolitic intrusions and through time. Zeolites formed during sub-solidus hydrothermal alteration under alkaline conditions and completely replace feldspathoid minerals in the matrix of the rock. A sequence of Ca-Na dominated zeolite species (gonnardite, thomsonite, mesolite) is followed by pure sodium endmember species (analcime, natrolite). These sequence reflects an increase in log[aNa+)/(aH+)] of the precipitating fluid. In contrast to the Fohberg phonolitc the Endhale phonolite contains analcime in addition to natrolite as pure Na zeolite species. The appearance of analcime is caused by higher silica activity during fluid rock interaction, which favors the formation of analcime over natrolite. The Fohberg phonolite is cut by fractures, which are totally or partially sealed with secondary minerals. Secondary minerals contain zeolites, followed by calcite and a variety of other silicates, carbonates, and sulphates as younger generations. Stable isotope analyses of late fracture calcite indicate the late circulation of meteoric fluids and mobilization of organic matter from surrounding sedimentary units.

  12. A cationic cesium continuum in zeolite x.

    PubMed

    Sun, T; Seff, K; Heo, N H; Petranovskii, V P

    1993-01-22

    A cesium continuum that fills the channels and cavities of zeolite X has been prepared, and its structure has been determined by single-crystal x-ray crystallography. The three-dimensional continuum is cationic to balance the negative charge of the zeolite framework. Its valence electrons, only 0.3 per Cs(+) ion, are widely delocalized over 95 percent of the cesium ions in the crystal. The continuum has a unit cell formula of (Cs(122))(86+) and contains Cs(13) and Cs(14) clusters (one per supercage) arranged like the atoms in diamond, with one Cs(2) appendix (in the sodalite cavity) per cluster. PMID:17734168

  13. Formation of Gold Nanoparticles in Zeolites

    NASA Astrophysics Data System (ADS)

    Pestryakov, A.; Tuzovskaya, I.; Smolentseva, E.; Bogdanchikova, N.; Jentoft, F. C.; Knop-Gericke, A.

    The formation of gold nanoparticles in mordenites has been studied by the methods of FTIR spectroscopy of adsorbed CO and diffuse reflectance UV-visible spectroscopy. Different states of ionic and metallic gold were detected in the zeolite cavities and on the external surface of the zeolite - Au+ and Au3+ ions, charged clusters Aun?+, and neutral nanoparticles Aum. The relative amount of these states depends on the method of sample preparation, type of redox treatment and the SiO2/Al2O3 molar ratio.

  14. A Cationic Cesium Continuum in Zeolite X

    NASA Astrophysics Data System (ADS)

    Sun, Tao; Seff, Karl; Heo, Nam Ho; Petranovskii, Vitalli P.

    1993-01-01

    A cesium continuum that fills the channels and cavities of zeolite X has been prepared, and its structure has been determined by single-crystal x-ray crystallography. The three-dimensional continuum is cationic to balance the negative charge of the zeolite framework. Its valence electrons, only 0.3 per Cs^+ ion, are widely delocalized over 95 percent of the cesium ions in the crystal. The continuum has a unit cell formula of (Cs122)86+ and contains Cs13 and Cs14 clusters (one per supercage) arranged like the atoms in diamond, with one Cs_2 appendix (in the sodalite cavity) per cluster.

  15. Silicate Glass Corrosion Mechanism revisited

    NASA Astrophysics Data System (ADS)

    Geisler, Thorsten; Lenting, Christoph; Dohmen, Lars

    2015-04-01

    Understanding the mechanism(s) of aqueous corrosion of nuclear waste borosilicate glasses is essential to predict their long-term aqueous durability in a geologic repository. Several observations have been made with compositionally different silicate glasses that cannot be explained by any of the established glass corrosion models. These models are based on diffusion-controlled ion exchange and subsequent structural reorganisation of a leached, hydrated residual glass, leaving behind a so-called gel layer. In fact, the common observation of lamellar to more complex pattern formation observed in experiment and nature, the porous structure of the corrosion layer, an atomically sharp boundary between the corrosion zone and the underlying pristine glass, as well as results of novel isotope tracer and in situ, real time experiments rather support an interface-coupled glass dissolution-silica reprecipitation model. In this model, the congruent dissolution of the glass is coupled in space and time to the precipitation and growth of amorphous silica at an inwardly moving reaction front. We suggest that these coupled processes have to be considered to realistically model the long-term performance of silicate glasses in aqueous environments.

  16. Epitaxial Growth of ZSM-5@Silicalite-1: A Core-Shell Zeolite Designed with Passivated Surface Acidity.

    PubMed

    Ghorbanpour, Arian; Gumidyala, Abhishek; Grabow, Lars C; Crossley, Steven P; Rimer, Jeffrey D

    2015-04-28

    The design of materials with spatially controlled chemical composition has potential advantages for wide-reaching applications that span energy to medicine. Here, we present a method for preparing a core-shell aluminosilicate zeolite with continuous translational symmetry of nanopores and an epitaxial shell of tunable thickness that passivates Brnsted acid sites associated with framework Al on exterior surfaces. For this study, we selected the commercially relevant MFI framework type and prepared core-shell particles consisting of an aluminosilicate core (ZSM-5) and a siliceous shell (silicalite-1). Transmission electron microscopy and gas adsorption studies confirmed that silicalite-1 forms an epitaxial layer on ZSM-5 crystals without blocking pore openings. Scanning electron microscopy and dynamic light scattering were used in combination to confirm that the shell thickness can be tailored with nanometer resolution (e.g., 5-20 nm). X-ray photoelectron spectroscopy and temperature-programmed desorption measurements revealed the presence of a siliceous shell, while probe reactions using molecules that were either too large or adequately sized to access MFI pores confirmed the uniform shell coverage. The synthesis of ZSM-5@silicalite-1 offers a pathway for tailoring the physicochemical properties of MFI-type materials, notably in the area of catalysis, where surface passivation can enhance product selectivity without sacrificing catalyst activity. The method described herein may prove to be a general platform for zeolite core-shell design with potentially broader applicability to other porous materials. PMID:25824422

  17. Ab-Initio Study of Incongruent Melting in Silicates

    NASA Astrophysics Data System (ADS)

    Pinilla, C.; Stixrude, L. P.

    2014-12-01

    Knowledge of the multi-component thermodynamics and phase equilibria of silicate melts at Earth's interior conditions are key to understand the chemical and thermal evolution of the planet. Yet they remain poorly constrained with a wide uncertainty on the eutectic composition and temperature. In this work we present results from ab-initio molecular dynamics in combination with the two-phase coexistance method to study properties of a system of MgSiO3 liquid coexisting with crystalline MgO at conditions of the deep lower mantle. During incongruent melting the crystal may either grow via partial freezing of the liquid or shrink via partial melting at a given temperature and pressure. The melting process can be studied using the two-phases method where liquid and solid are in contact at a given temperature and pressure and so under thermodynamic equilibrium. We characterise the composition and densities of the resultant solid and liquid phases, provide chemical potentials of the liquid phase and study the structural and dynamical properties of the melt. In addition, we discuss the performance of alternative computational methods applied to the study of incongruent melting in silicate systems where long simulation times and a large number of atoms are usually needed. Finally, we discuss the implication of our findings for the evolution of the Earth's interior.

  18. Carbon substitution for oxygen in silicates in planetary interiors.

    PubMed

    Sen, Sabyasachi; Widgeon, Scarlett J; Navrotsky, Alexandra; Mera, Gabriela; Tavakoli, Amir; Ionescu, Emanuel; Riedel, Ralf

    2013-10-01

    Amorphous silicon oxycarbide polymer-derived ceramics (PDCs), synthesized from organometallic precursors, contain carbon- and silica-rich nanodomains, the latter with extensive substitution of carbon for oxygen, linking Si-centered SiO(x)C(4-x) tetrahedra. Calorimetric studies demonstrated these PDCs to be thermodynamically more stable than a mixture of SiO2, C, and silicon carbide. Here, we show by multinuclear NMR spectroscopy that substitution of C for O is also attained in PDCs with depolymerized silica-rich domains containing lithium, associated with SiO(x)C(4-x) tetrahedra with nonbridging oxygen. We suggest that significant (several percent) substitution of C for O could occur in more complex geological silicate melts/glasses in contact with graphite at moderate pressure and high temperature and may be thermodynamically far more accessible than C for Si substitution. Carbon incorporation will change the local structure and may affect physical properties, such as viscosity. Analogous carbon substitution at grain boundaries, at defect sites, or as equilibrium states in nominally acarbonaceous crystalline silicates, even if present at levels at 10-100 ppm, might form an extensive and hitherto hidden reservoir of carbon in the lower crust and mantle. PMID:24043830

  19. Carbon substitution for oxygen in silicates in planetary interiors

    PubMed Central

    Sen, Sabyasachi; Widgeon, Scarlett J.; Navrotsky, Alexandra; Mera, Gabriela; Tavakoli, Amir; Ionescu, Emanuel; Riedel, Ralf

    2013-01-01

    Amorphous silicon oxycarbide polymer-derived ceramics (PDCs), synthesized from organometallic precursors, contain carbon- and silica-rich nanodomains, the latter with extensive substitution of carbon for oxygen, linking Si-centered SiOxC4-x tetrahedra. Calorimetric studies demonstrated these PDCs to be thermodynamically more stable than a mixture of SiO2, C, and silicon carbide. Here, we show by multinuclear NMR spectroscopy that substitution of C for O is also attained in PDCs with depolymerized silica-rich domains containing lithium, associated with SiOxC4-x tetrahedra with nonbridging oxygen. We suggest that significant (several percent) substitution of C for O could occur in more complex geological silicate melts/glasses in contact with graphite at moderate pressure and high temperature and may be thermodynamically far more accessible than C for Si substitution. Carbon incorporation will change the local structure and may affect physical properties, such as viscosity. Analogous carbon substitution at grain boundaries, at defect sites, or as equilibrium states in nominally acarbonaceous crystalline silicates, even if present at levels at 10–100 ppm, might form an extensive and hitherto hidden reservoir of carbon in the lower crust and mantle. PMID:24043830

  20. 3-d Orientation and Properties of Polymer Layered Silicate Nanocomposites

    NASA Astrophysics Data System (ADS)

    Bafna, Ayush; Beaucage, Gregory; Mirabella, Francis; Kohl, Bryce

    2002-03-01

    3-d Orientation and Properties of Polymer Layered Silicate Nanocomposites (PLSN) containing silicate (clay) layers dispersed in a polymer matrix were studied. Exfoliation of the clay platelets enhances barrier property of the nanocomposites. 3-d orientation of these clay platelets in nanocomposites plays a major role in determining final properties. Depending on the processing technique and the tensor cumulative shear the clay platelets orient in different directions. The effect of clay orientation on barrier properties is presented in this study. The effect of clay dispersion on the degree of crystallinity and crystal thickness is also presented. A relation between cumulative shear and clay orientation is proposed Polymer-Clay nanocomposite films were produced in a film blower. The effect of shear on the 3-dimensional orientation of clay platelets was studied small angle x-ray scattering (SAXS). Effects of this platelet orientation on the barrier properties were studied. Transmission electron microscopy (TEM) was used to study the exfoliation and dispersion of the clay platelets in the nanocomposite. X-ray diffraction (XRD) along with DSC, SAXS and TEM was used to study the effect of clay dispersion on the crystallization behavior of polymer in the nanocomposite.

  1. 21 CFR 182.2227 - Calcium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Anticaking Agents § 182.2227 Calcium silicate. (a) Product. Calcium...

  2. 21 CFR 582.2906 - Tricalcium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Tricalcium silicate. 582.2906 Section 582.2906 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE Anticaking Agents 582.2906 Tricalcium silicate. (a) Product....

  3. 21 CFR 182.2906 - Tricalcium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Tricalcium silicate. 182.2906 Section 182.2906 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Anticaking Agents 182.2906 Tricalcium silicate. (a) Product....

  4. 21 CFR 182.2437 - Magnesium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Magnesium silicate. 182.2437 Section 182.2437 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Anticaking Agents § 182.2437 Magnesium silicate. (a) Product....

  5. Silicate minerals and the interferon system

    SciTech Connect

    Hahon, N.; Booth, J.A.

    1987-08-01

    Natural-occurring minerals representative of six silicate classes were examined for their influence on interferon induction by influenza virus in Rhesus monkey kidney (LLC-MK/sub 2/) cell monolayers. Minerals within the classes nesosilicate, sorosilicate, cyclosilicate, and inosilicate exhibited either little or marked (50% or greater) inhibition of interferon induction. Within the inosilicate class, however, minerals of the pyroxenoid group (wollastonite, pectolite, and rhodonite) all significantly showed a two- to threefold increase in interferon production. Silicate materials in the phyllosilicate and tectosilicate classes all showed inhibitory activity for the induction process. When silicate minerals were coated with the polymer poly(4-vinylpyridine-N-oxide), the inhibitory activity of silicates on viral interferon induction was counteracted. Of nine randomly selected silicate minerals, which inhibited viral interferon induction, none adversely affected the ability of exogenous interferon to confer antiviral cellular resistance. Increased levels of influenza virus multiplication concomitant with decreased levels of interferon occurred in cell monolayers pretreated with silicates. The findings of this study demonstrate the diverse effects of minerals representative of different silicate classes on the interferon system and indicate that certain silicates in comprising the viral interferon induction process may increase susceptibility to viral infection.

  6. Dynamic crystallization of silicate melts

    NASA Technical Reports Server (NTRS)

    Russell, W. J.

    1984-01-01

    Two types of furnaces with differing temperature range capabilities were used to provide variations in melt temperatures and cooling rates in a study of the effects of heterogeneous nucleation on crystallization. Materials of chondrule composition were used to further understanding of how the disequilibrium features displayed by minerals in rocks are formed. Results show that the textures of natural chondrules were duplicated. It is concluded that the melt history is dominant over cooling rate and composition in controlling texture. The importance of nuclei, which are most readily derived from preexisting crystalline material, support an origin for natural chondrules based on remelting of crystalline material. This would be compatible with a simple, uniform chondrule forming process having only slight variations in thermal histories resulting in the wide range of textures.

  7. Layered Topological Crystalline Insulators

    NASA Astrophysics Data System (ADS)

    Kim, Youngkuk; Kane, C. L.; Mele, E. J.; Rappe, Andrew M.

    2015-08-01

    Topological crystalline insulators (TCIs) are insulating materials whose topological property relies on generic crystalline symmetries. Based on first-principles calculations, we study a three-dimensional (3D) crystal constructed by stacking two-dimensional TCI layers. Depending on the interlayer interaction, the layered crystal can realize diverse 3D topological phases characterized by two mirror Chern numbers (MCNs) (μ1,μ2 ) defined on inequivalent mirror-invariant planes in the Brillouin zone. As an example, we demonstrate that new TCI phases can be realized in layered materials such as a PbSe (001) monolayer/h -BN heterostructure and can be tuned by mechanical strain. Our results shed light on the role of the MCNs on inequivalent mirror-symmetric planes in reciprocal space and open new possibilities for finding new topological materials.

  8. Liquid crystalline composites containing phyllosilicates

    DOEpatents

    Chaiko; David J. (Naperville, IL)

    2007-05-08

    The present invention provides barrier films having reduced gas permeability for use in packaging and coating applications. The barrier films comprise an anisotropic liquid crystalline composite layer formed from phyllosilicate-polymer compositions. Phyllosilicate-polymer liquid crystalline compositions of the present invention can contain a high percentage of phyllosilicate while remaining transparent. Because of the ordering of the particles in the liquid crystalline composite, barrier films comprising liquid crystalline composites are particularly useful as barriers to gas transport.

  9. Crystalline titanate catalyst supports

    DOEpatents

    Anthony, R.G.; Dosch, R.G.

    1993-01-05

    A series of new crystalline titanates (CT) are shown to have considerable potential as catalyst supports. For Pd supported catalyst, the catalytic activity for pyrene hydrogenation was substantially different depending on the type of CT, and one was substantially more active than Pd on hydrous titanium oxide (HTO). For 1-hexene hydrogenation the activities of the new CTs were approximately the same as for the hydrous metal oxide supports.

  10. Liquid crystalline dendrimers.

    PubMed

    Donnio, Bertrand; Buathong, Saïwan; Bury, Izabela; Guillon, Daniel

    2007-09-01

    In recent years, there has been an increasing interest in the field of liquid crystalline dendrimers. Such a fast development is, among other things, driven by the multiple possibilities offered by combining the mesomorphic properties of single mesogenic subunits with the supermolecular and versatile architectures of dendrimers to yield a new class of highly functional materials. The induction and the control of the mesomorphic properties (phase type and stability) in dendrimers can be achieved by a dedicated molecular design which depends on the chemical nature and structure of both the functional groups and the dendritic matrix. In particular, the intrinsic connectivity of the dendrimer such as the multivalency of the focal core and the multiplicity of the branches, both controlling the geometrical rate of growth, or the dendritic generation, plays a crucial role and influences at various stages the subtle relationships between the supermolecular structure and the mesophase structure and stability. In this critical review article, an account of the various types of dendritic systems that form liquid-crystalline mesophases along with a description of the self-organization of representative case-study supermolecules into liquid crystalline mesophases will be discussed. Some basics of thermotropic liquid crystals and dendrimers will be given in the introduction. Then, in the following sections, selected examples including side-chain, main-chain, fullerodendrimers, shape-persistent dendrimers, supramolecular dendromesogens and metallodendrimers, as representative families of LC dendrimers, will be described. In the conclusion some further developments will be highlighted. This review will not cover liquid crystalline hyperbranched and dendronized polymers that might be considered as being somehow less structurally "perfect". PMID:17660881

  11. Crystalline titanate catalyst supports

    DOEpatents

    Anthony, Rayford G.; Dosch, Robert G.

    1993-01-01

    A series of new crystalline titanates (CT) are shown to have considerable potential as catalyst supports. For Pd supported catalyst, the catalytic activity for pyrene hydrogenation was substantially different depending on the type of CT, and one was substantially more active than Pd on hydrous titanium oxide (HTO). For 1-hexene hydrogenation the activities of the new CTs were approximately the same as for the hydrous metal oxide supports.

  12. One-pot synthesis of MWW zeolite nanosheets using a rationally designed organic structure-directing agent

    PubMed Central

    Luo, Helen Y.; Michaelis, Vladimir K.; Hodges, Sydney; Griffin, Robert G.

    2015-01-01

    A new material MIT-1 comprised of delaminated MWW zeolite nanosheets is synthesized in one-pot using a rationally designed organic structure-directing agent (OSDA). The OSDA is comprised of a hydrophilic head segment that resembles the OSDA used to synthesize the zeolite precursor MCM22(P), a hydrophobic tail segment that resembles the swelling agent used to swell MCM22(P), and a di-quaternary ammonium linker that connects both segments. MIT-1 features high crystallinity and surface areas exceeding 500 m2g?1, and can be synthesized over a wide synthesis window that includes Si/Al ratios ranging from 13 to 67. Characterization data reveal high mesoporosity and acid strength with no detectable amorphous silica phases. Compared to MCM-22 and MCM-56, MIT-1 shows a three-fold increase in catalytic activity for the Friedel-Crafts alkylation of benzene with benzyl alcohol. PMID:26478803

  13. COLLIDING CRYSTALLINE BEAMS.

    SciTech Connect

    WEI, J.

    1998-06-26

    The understanding of crystalline beams has advanced to the point where one can now, with reasonable confidence, undertake an analysis of the luminosity of colliding crystalline beams. Such a study is reported here. It is necessary to observe the criteria, previously stated, for the creation and stability of crystalline beams. This requires, firstly, the proper design of a lattice. Secondly, a crystal must be formed, and this can usually be done at various densities. Thirdly, the crystals in a colliding-beam machine are brought into collision. We study all of these processes using the molecular dynamics (MD) method. The work parallels what was done previously, but the new part is to study the crystal-crystal interaction in collision. We initially study the zero-temperature situation. If the beam-beam force (or equivalent tune shift) is too large then overlapping crystals can not be created (rather two spatially separated crystals are formed). However, if the beam-beam force is less than but comparable to that of the space-charge forces between the particles, we find that overlapping crystals can be formed and the beam-beam tune shift can be of the order of unity. Operating at low but non-zero temperature can increase the luminosity by several orders of magnitude over that of a usual collider. The construction of an appropriate lattice, and the development of adequately strong cooling, although theoretically achievable, is a challenge in practice.

  14. Colliding crystalline beams

    SciTech Connect

    Wei, J.; Sessler, A.M.

    1998-08-01

    The understanding of crystalline beams has advanced to the point where one can now, with reasonable confidence, undertake an analysis of the luminosity of colliding crystalline beams. Such a study is reported here. It is necessary to observe the criteria, previously stated, for the creation and stability of crystalline beams. This requires, firstly, the proper design of a lattice. Secondly, a crystal must be formed, and this can usually be done at various densities. Thirdly, the crystals in a colliding-beam machine are brought into collision. The authors study all of these processes using the molecular dynamics (MD) method. The work parallels what was done previously, but the new part is to study the crystal-crystal interaction in collision. They initially study the zero-temperature situation. If the beam-beam force (or equivalent tune shift) is too large then overlapping crystals can not be created (rather two spatially separated crystals are formed). However, if the beam-beam force is less than but comparable to that of the space-charge forces between the particles, they find that overlapping crystals can be formed and the beam-beam tune shift can be of the order of unity. Operating at low but non-zero temperature can increase the luminosity by several orders of magnitude over that of a usual collider. The construction of an appropriate lattice, and the development of adequately strong cooling, although theoretically achievable, is a challenge in practice.

  15. Biochemical evolution. I. Polymerization on internal, organophilic silica surfaces of dealuminated zeolites and feldspars

    PubMed Central

    Smith, Joseph V.

    1998-01-01

    Catalysis at mineral surfaces might generate replicating biopolymers from simple chemicals supplied by meteorites, volcanic gases, and photochemical gas reactions. Many ideas are implausible in detail because the proposed mineral surfaces strongly prefer water and other ionic species to organic ones. The molecular sieve silicalite (Union Carbide; = Al-free Mobil ZSM-5 zeolite) has a three-dimensional, 10-ring channel system whose electrically neutral Si-O surface strongly adsorbs organic species over water. Three -O-Si tetrahedral bonds lie in the surface, and the fourth Si-O points inwards. In contrast, the outward Si-OH of simple quartz and feldspar crystals generates their ionic organophobicity. The ZSM-5-type zeolite mutinaite occurs in Antarctica with boggsite and tschernichite (Al-analog of Mobil Beta). Archean mutinaite might have become de-aluminated toward silicalite during hot/cold/wet/dry cycles. Catalytic activity of silicalite increases linearly with Al-OH substitution for Si, and Al atoms tend to avoid each other. Adjacent organophilic and catalytic Al-OH regions in nanometer channels might have scavenged organic species for catalytic assembly into specific polymers protected from prompt photochemical destruction. Polymer migration along weathered silicic surfaces of micrometer-wide channels of feldspars might have led to assembly of replicating catalytic biomolecules and perhaps primitive cellular organisms. Silica-rich volcanic glasses should have been abundant on the early Earth, ready for crystallization into zeolites and feldspars, as in present continental basins. Abundant chert from weakly metamorphosed Archaean rocks might retain microscopic clues to the proposed mineral adsorbent/catalysts. Other framework silicas are possible, including ones with laevo/dextro one-dimensional channels. Organic molecules, transition-metal ions, and P occur inside modern feldspars. PMID:9520372

  16. IMPROVED CATALYSTS FOR HEAVY OIL UPGRADING BASED ON ZEOLITE Y NANOPARTICLES ENCAPSULATED IN STABLE NANOPOROUS HOST

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2005-11-15

    Composite materials of SBA-15/zeolite Y were synthesized from zeolite Y precursor and a synthesis mixture of mesoporous silicate SBA-15 via a hydrothermal process in the presence of a slightly acidic media of pH 4-6 with 2M H{sub 2}SO{sub 4}. The SBA-15/ZY composites showed Type IV adsorption isotherms, narrow BJH average pore size distribution of 4.9 nm, surface areas up to 800 m{sup 2}2/g and pore volumes 1.03 cm{sup 3}, all comparable to pure SBA-15 synthesized under similar conditions. Chemical analysis revealed Si/Al ratio down to 8.5 in the most aluminated sample, and {sup 27}AlSS MAS NMR confirmed aluminum was in tetrahedral coordination. This method of introduction of Al in pure T{sub d} coordination is effective in comparison to other direct and post synthesis alumination methods. Bronsted acid sites were evident from a pyridinium peak at 1544 cm-1 in the FTIR spectrum after pyridine adsorption, and from NH{sub 3} -TPD experiments. SBA-15/ZY composites showed significant catalytic activities for the dealkylation of isopropylbenzene to benzene and propene, similar to those of commercial zeolite Y. It was observed that higher conversion for catalysts synthesized with high amount of ZY precursor mixture added to the SBA-15. Over all the composites has shown good catalytic activity. Further studies will be focused on gaining a better understand the nature of the precursor, and to characterize and to locate the acid sites in the composite material. The composite will also be evaluated for heavy oil conversion to naphtha and middle distillates.

  17. Biochemical evolution. I. Polymerization On internal, organophilic silica surfaces of dealuminated zeolites and feldspars.

    PubMed

    Smith, J V

    1998-03-31

    Catalysis at mineral surfaces might generate replicating biopolymers from simple chemicals supplied by meteorites, volcanic gases, and photochemical gas reactions. Many ideas are implausible in detail because the proposed mineral surfaces strongly prefer water and other ionic species to organic ones. The molecular sieve silicalite (Union Carbide; = Al-free Mobil ZSM-5 zeolite) has a three-dimensional, 10-ring channel system whose electrically neutral Si-O surface strongly adsorbs organic species over water. Three -O-Si tetrahedral bonds lie in the surface, and the fourth Si-O points inwards. In contrast, the outward Si-OH of simple quartz and feldspar crystals generates their ionic organophobicity. The ZSM-5-type zeolite mutinaite occurs in Antarctica with boggsite and tschernichite (Al-analog of Mobil Beta). Archean mutinaite might have become de-aluminated toward silicalite during hot/cold/wet/dry cycles. Catalytic activity of silicalite increases linearly with Al-OH substitution for Si, and Al atoms tend to avoid each other. Adjacent organophilic and catalytic Al-OH regions in nanometer channels might have scavenged organic species for catalytic assembly into specific polymers protected from prompt photochemical destruction. Polymer migration along weathered silicic surfaces of micrometer-wide channels of feldspars might have led to assembly of replicating catalytic biomolecules and perhaps primitive cellular organisms. Silica-rich volcanic glasses should have been abundant on the early Earth, ready for crystallization into zeolites and feldspars, as in present continental basins. Abundant chert from weakly metamorphosed Archaean rocks might retain microscopic clues to the proposed mineral adsorbent/catalysts. Other framework silicas are possible, including ones with laevo/dextro one-dimensional channels. Organic molecules, transition-metal ions, and P occur inside modern feldspars. PMID:9520372

  18. Effective diffusivities in zeolites 3. Effects of polarity, cation density, and site occupancy in ZSM-5

    SciTech Connect

    Garcia, S.F.; Weisz, P.B. )

    1993-11-01

    The effective diffusivity that determines the catalytic reaction inhibition (utilization factor) in the steady-state process of catalysis, D[sub ss], differs from that derived from nonsteady-state sorption kinetics, D[sub ns] (e.g., uptake diffusivity'). D[sub ss] is obtainable from D[sub ns] by a transformation based on the equilibrium ratio C[sub T]/C[sub o] of the total sorbed concentration to the applied vapor phase concentration c[sub o][center dot]D[sub s] is several orders of magnitude larger than D[sub ns]. For o-xylene in siliceous ZSM-5 D[sub ss] was found to be virtually invariant with temperature. Introducing a polar NH[sub 2] substituent in place of CH[sub 3] does not alter the temperature independence, i.e., it does not introduce or alter activation energy'. In fact, a larger diffusively results, presumably from the slightly smaller effective molecular size. Introducing a high sodium cation density in the zeolite structure creates a temperature dependence of D[sub ss]. However, it is shown to be a result of the high percentage of occupancy of transition (jump) sites by sorbed molecules which diminishes with increasing temperature. These several observations allow important conclusions to be drawn concerning the real or apparent nature of activated' diffusion in the zeolite. 18 refs., 8 figs.

  19. Intrinsic flexibility of porous materials; theory, modelling and the flexibility window of the EMT zeolite framework

    PubMed Central

    Fletcher, Rachel E.; Wells, Stephen A.; Leung, Ka Ming; Edwards, Peter P.; Sartbaeva, Asel

    2015-01-01

    Framework materials have structures containing strongly bonded polyhedral groups of atoms connected through their vertices. Typically the energy cost for variations of the inter-polyhedral geometry is much less than the cost of distortions of the polyhedra themselves – as in the case of silicates, where the geometry of the SiO4 tetrahedral group is much more strongly constrained than the Si—O—Si bridging angle. As a result, framework materials frequently display intrinsic flexibility, and their dynamic and static properties are strongly influenced by low-energy collective motions of the polyhedra. Insight into these motions can be obtained in reciprocal space through the ‘rigid unit mode’ (RUM) model, and in real-space through template-based geometric simulations. We briefly review the framework flexibility phenomena in energy-relevant materials, including ionic conductors, perovskites and zeolites. In particular we examine the ‘flexibility window’ phenomenon in zeolites and present novel results on the flexibility window of the EMT framework, which shed light on the role of structure-directing agents. Our key finding is that the crown ether, despite its steric bulk, does not limit the geometric flexibility of the framework. PMID:26634720

  20. Zeolite 5A Catalyzed Etherification of Diphenylmethanol

    ERIC Educational Resources Information Center

    Cooke, Jason; Henderson, Eric J.; Lightbody, Owen C.

    2009-01-01

    An experiment for the synthetic undergraduate laboratory is described in which zeolite 5A catalyzes the room temperature dehydration of diphenylmethanol, (C[subscript 6]H[subscript 5])[subscript 2]CHOH, producing 1,1,1',1'-tetraphenyldimethyl ether, (C[subscript 6]H[subscript 5])[subscript 2]CHOCH(C[subscript 6]H[subscript 5])[subscript 2]. The…

  1. SODIUM ZEOLITE A SUPPLEMENTATION TO DAIRY CALVES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sodium zeolite A (SZA), an aluminosilicate, has been used in a number of animal studies, but alterations in mineral metabolism and tissue composition have not been fully investigated. The objective of this study was to determine the effects of SZA on mineral metabolism and tissue mineral composition...

  2. Multicomponent liquid ion exchange with chabazite zeolites

    SciTech Connect

    Robinson, S.M.; Arnold, W.D. Jr.; Byers, C.W.

    1993-10-01

    In spite of the increasing commercial use of zeolites for binary and multicomponent sorption, the understanding of the basic mass-transfer processes associated with multicomponent zeolite ion-exchange systems is quite limited. This study was undertaken to evaluate Na-Ca-Mg-Cs-Sr ion exchange from an aqueous solution using a chabazite zeolite. Mass-transfer coefficients and equilibrium equations were determined from experimental batch-reactor data for single and multicomponent systems. The Langmuir isotherm was used to represent the equilibrium relationship for binary systems, and a modified Dubinin-Polyani model was used for the multicomponent systems. The experimental data indicate that diffusion through the microporous zeolite crystals is the primary diffusional resistance. Macropore diffusion also significantly contributes to the mass-transfer resistance. Various mass-transfer models were compared to the experimental data to determine mass-transfer coefficients. Effective diffusivities were obtained which accurately predicted experimental data using a variety of models. Only the model which accounts for micropore and macropore diffusion occurring in series accurately predicted multicomponent data using single-component diffusivities. Liquid and surface diffusion both contribute to macropore diffusion. Surface and micropore diffusivities were determined to be concentration dependent.

  3. Zeolite 5A Catalyzed Etherification of Diphenylmethanol

    ERIC Educational Resources Information Center

    Cooke, Jason; Henderson, Eric J.; Lightbody, Owen C.

    2009-01-01

    An experiment for the synthetic undergraduate laboratory is described in which zeolite 5A catalyzes the room temperature dehydration of diphenylmethanol, (C[subscript 6]H[subscript 5])[subscript 2]CHOH, producing 1,1,1',1'-tetraphenyldimethyl ether, (C[subscript 6]H[subscript 5])[subscript 2]CHOCH(C[subscript 6]H[subscript 5])[subscript 2]. The

  4. Framework Al zoning in zeolite ECR-1.

    PubMed

    Shin, Jiho; Ahn, Nak Ho; Cho, Sung June; Ren, Limin; Xiao, Feng-Shou; Hong, Suk Bong

    2014-02-25

    Rietveld analyses of the synchrotron X-ray diffraction data for various cation forms of zeolite ECR-1 have demonstrated framework Al zoning, which parallels the alternation of Al-rich maz and Al-poor mor layers. This can be further supported by notable differences in the average bond valence of its 10 crystallographically distinct tetrahedral sites. PMID:24409461

  5. Dispersion enhanced metal/zeolite catalysts

    DOEpatents

    Sachtler, Wolfgang M. H. (Evanston, IL); Tzou, Ming-Shin (Evanston, IL); Jiang, Hui-Jong (Evanston, IL)

    1987-01-01

    Dispersion stabilized zeolite supported metal catalysts are provided as bimetallic catalyst combinations. The catalyst metal is in a reduced zero valent form while the dispersion stabilizer metal is in an unreduced ionic form. Representative catalysts are prepared from platinum or nickel as the catalyst metal and iron or chromium dispersion stabilizer.

  6. Dispersion enhanced metal/zeolite catalysts

    DOEpatents

    Sachtler, W.M.H.; Tzou, M.S.; Jiang, H.J.

    1987-03-31

    Dispersion stabilized zeolite supported metal catalysts are provided as bimetallic catalyst combinations. The catalyst metal is in a reduced zero valent form while the dispersion stabilizer metal is in an unreduced ionic form. Representative catalysts are prepared from platinum or nickel as the catalyst metal and iron or chromium dispersion stabilizer.

  7. MERCURY SEPARATION FROM POLLUTANT WATER USING ZEOLITES

    EPA Science Inventory

    Arsenic is known to be a hazardous contaminant in drinking water that causes arsenical dermatitis and skin cancer. In the present work, the potential use of a variety of synthetic zeolites for removal of arsenic from water has been examined at room temperature. Experiments have...

  8. ARSENIC SEPARATION FROM WATER USING ZEOLITES: SYMPOSIUM

    EPA Science Inventory

    NRMRL-ADA-01134 Shevade, S, Ford*, R., and Puls*, R.W. "Arsenic Separation from Water Using Zeolites." In: 222nd ACS National Meeting, ACS Environmental Chemistry Division Symposia, Chicago, IL, 08/26-30/2001. 2001. 04/23/2001 This...

  9. ARSENIC SEPARATION FROM WATER USING ZEOLITES

    EPA Science Inventory

    Arsenic is known to be a hazardous contaminant in drinking water. The presence of arsenic in water supplies has been linked to arsenical dermatosis and skin cancer . Zeolites are well known for their ion exchange capacities. In the present work, the potential use of a variety of ...

  10. Ni(2+)-zeolite/ferrosphere and Ni(2+)-silica/ferrosphere beads for magnetic affinity separation of histidine-tagged proteins.

    PubMed

    Vereshchagina, T A; Fedorchak, M A; Sharonova, O M; Fomenko, E V; Shishkina, N N; Zhizhaev, A M; Kudryavtsev, A N; Frank, L A; Anshits, A G

    2016-01-19

    Magnetic Ni(2+)-zeolite/ferrosphere and Ni(2+)-silica/ferrosphere beads (Ni-ferrosphere beads - NFB) of a core-shell structure were synthesized starting from coal fly ash ferrospheres having diameters in the range of 0.063-0.050 mm. The strategy of NFB fabrication is an oriented chemical modification of the outer surface preserving the magnetic core of parent beads with the formation of micro-mesoporous coverings. Two routes of ferrosphere modification were realized, such as (i) hydrothermal treatment in an alkaline medium resulting in a NaP zeolite layer and (ii) synthesis of micro-mesoporous silica on the glass surface using conventional methods. Immobilization of Ni(2+) ions in the siliceous porous shell of the magnetic beads was carried out via (i) the ion exchange of Na(+) for Ni(2+) in the zeolite layer or (ii) deposition of NiO clusters in the zeolite and silica pores. The final NFB were tested for affinity in magnetic separation of the histidine-tagged green fluorescent protein (GFP) directly from a cell lysate. Results pointed to the high affinity of the magnetic beads towards the protein in the presence of 10 mM EDTA. The sorption capacity of the ferrosphere-based Ni-beads with respect to GFP was in the range 1.5-5.7 mg cm(-3). PMID:26688000

  11. Mesoporous Silicate Materials in Sensing

    PubMed Central

    Melde, Brian J.; Johnson, Brandy J.; Charles, Paul T.

    2008-01-01

    Mesoporous silicas, especially those exhibiting ordered pore systems and uniform pore diameters, have shown great potential for sensing applications in recent years. Morphological control grants them versatility in the method of deployment whether as bulk powders, monoliths, thin films, or embedded in coatings. High surface areas and pore sizes greater than 2 nm make them effective as adsorbent coatings for humidity sensors. The pore networks also provide the potential for immobilization of enzymes within the materials. Functionalization of materials by silane grafting or through co-condensation of silicate precursors can be used to provide mesoporous materials with a variety of fluorescent probes as well as surface properties that aid in selective detection of specific analytes. This review will illustrate how mesoporous silicas have been applied to sensing changes in relative humidity, changes in pH, metal cations, toxic industrial compounds, volatile organic compounds, small molecules and ions, nitroenergetic compounds, and biologically relevant molecules.

  12. Zeolite Nanoparticles for Selective Sorption of Plasma Proteins.

    PubMed

    Rahimi, M; Ng, E-P; Bakhtiari, K; Vinciguerra, M; Ahmad, H Ali; Awala, H; Mintova, S; Daghighi, M; Bakhshandeh Rostami, F; de Vries, M; Motazacker, M M; Peppelenbosch, M P; Mahmoudi, M; Rezaee, F

    2015-01-01

    The affinity of zeolite nanoparticles (diameter of 8-12?nm) possessing high surface area and high pore volume towards human plasma proteins has been investigated. The protein composition (corona) of zeolite nanoparticles has been shown to be more dependent on the plasma protein concentrations and the type of zeolites than zeolite nanoparticles concentration. The number of proteins present in the corona of zeolite nanoparticles at 100% plasma (in vivo state) is less than with 10% plasma exposure. This could be due to a competition between the proteins to occupy the corona of the zeolite nanoparticles. Moreover, a high selective adsorption for apolipoprotein C-III (APOC-III) and fibrinogen on the zeolite nanoparticles at high plasma concentration (100%) was observed. While the zeolite nanoparticles exposed to low plasma concentration (10%) exhibited a high selective adsorption for immunoglobulin gamma (i.e. IGHG1, IGHG2 and IGHG4) proteins. The zeolite nanoparticles can potentially be used for selectively capture of APOC-III in order to reduce the activation of lipoprotein lipase inhibition during hypertriglyceridemia treatment. The zeolite nanoparticles can be adapted to hemophilic patients (hemophilia A (F-VIII deficient) and hemophilia B (F-IX deficient)) with a risk of bleeding, and thus might be potentially used in combination with the existing therapy. PMID:26616161

  13. Zeolite Nanoparticles for Selective Sorption of Plasma Proteins

    NASA Astrophysics Data System (ADS)

    Rahimi, M.; Ng, E.-P.; Bakhtiari, K.; Vinciguerra, M.; Ahmad, H. Ali; Awala, H.; Mintova, S.; Daghighi, M.; Bakhshandeh Rostami, F.; de Vries, M.; Motazacker, M. M.; Peppelenbosch, M. P.; Mahmoudi, M.; Rezaee, F.

    2015-11-01

    The affinity of zeolite nanoparticles (diameter of 8–12 nm) possessing high surface area and high pore volume towards human plasma proteins has been investigated. The protein composition (corona) of zeolite nanoparticles has been shown to be more dependent on the plasma protein concentrations and the type of zeolites than zeolite nanoparticles concentration. The number of proteins present in the corona of zeolite nanoparticles at 100% plasma (in vivo state) is less than with 10% plasma exposure. This could be due to a competition between the proteins to occupy the corona of the zeolite nanoparticles. Moreover, a high selective adsorption for apolipoprotein C-III (APOC-III) and fibrinogen on the zeolite nanoparticles at high plasma concentration (100%) was observed. While the zeolite nanoparticles exposed to low plasma concentration (10%) exhibited a high selective adsorption for immunoglobulin gamma (i.e. IGHG1, IGHG2 and IGHG4) proteins. The zeolite nanoparticles can potentially be used for selectively capture of APOC-III in order to reduce the activation of lipoprotein lipase inhibition during hypertriglyceridemia treatment. The zeolite nanoparticles can be adapted to hemophilic patients (hemophilia A (F-VIII deficient) and hemophilia B (F-IX deficient)) with a risk of bleeding, and thus might be potentially used in combination with the existing therapy.

  14. Conversion of Ethanol to Hydrocarbons on Hierarchical HZSM-5 Zeolites

    SciTech Connect

    Ramasamy, Karthikeyan K.; Zhang, He; Sun, Junming; Wang, Yong

    2014-12-15

    This study reports synthesis, characterization, and catalytic activity of the nano-size hierarchical HZSM-5 zeolite with high mesoporosity produced via a solvent evaporation procedure. Further, this study compares hierarchical zeolites with conventional HZSM-5 zeolite with similar Si/Al ratios for the ethanol-to-hydrocarbon conversion process. The catalytic performance of the hierarchical and conventional zeolites was evaluated using a fixed-bed reactor at 360 C, 300 psig, and a weight hourly space velocity of 7.9 h-1. For the low Si/Al ratio zeolite (~40), the catalytic life-time for the hierarchical HZSM-5 was approximately 2 times greater than the conventional HZSM-5 despite its coking amount deposited 1.6 times higher than conventional HZSM-5. For the high Si/Al ratio zeolite (~140), the catalytic life-time for the hierarchical zeolite was approximately 5 times greater than the conventional zeolite and the amount of coking deposited was 2.1 times higher. Correlation was observed between catalyst life time, porosity, and the crystal size of the zeolite. The nano-size hierarchical HZSM-5 zeolites containing mesoporosity demonstrated improved catalyst life-time compared to the conventional catalyst due to faster removal of products, shorter diffusion path length, and the migration of the coke deposits to the external surface from the pore structure.

  15. Zeolite Nanoparticles for Selective Sorption of Plasma Proteins

    PubMed Central

    Rahimi, M.; Ng, E.-P.; Bakhtiari, K.; Vinciguerra, M.; Ahmad, H. Ali; Awala, H.; Mintova, S.; Daghighi, M.; Bakhshandeh Rostami, F.; de Vries, M.; Motazacker, M. M.; Peppelenbosch, M. P.; Mahmoudi, M.; Rezaee, F.

    2015-01-01

    The affinity of zeolite nanoparticles (diameter of 8–12 nm) possessing high surface area and high pore volume towards human plasma proteins has been investigated. The protein composition (corona) of zeolite nanoparticles has been shown to be more dependent on the plasma protein concentrations and the type of zeolites than zeolite nanoparticles concentration. The number of proteins present in the corona of zeolite nanoparticles at 100% plasma (in vivo state) is less than with 10% plasma exposure. This could be due to a competition between the proteins to occupy the corona of the zeolite nanoparticles. Moreover, a high selective adsorption for apolipoprotein C-III (APOC-III) and fibrinogen on the zeolite nanoparticles at high plasma concentration (100%) was observed. While the zeolite nanoparticles exposed to low plasma concentration (10%) exhibited a high selective adsorption for immunoglobulin gamma (i.e. IGHG1, IGHG2 and IGHG4) proteins. The zeolite nanoparticles can potentially be used for selectively capture of APOC-III in order to reduce the activation of lipoprotein lipase inhibition during hypertriglyceridemia treatment. The zeolite nanoparticles can be adapted to hemophilic patients (hemophilia A (F-VIII deficient) and hemophilia B (F-IX deficient)) with a risk of bleeding, and thus might be potentially used in combination with the existing therapy. PMID:26616161

  16. Energetics of sodium-calcium exchanged zeolite A.

    PubMed

    Sun, H; Wu, D; Guo, X; Shen, B; Navrotsky, A

    2015-05-01

    A series of calcium-exchanged zeolite A samples with different degrees of exchange were prepared. They were characterized by powder X-ray diffraction (XRD) and differential scanning calorimetry (DSC). High temperature oxide melt drop solution calorimetry measured the formation enthalpies of hydrated zeolites CaNa-A from constituent oxides. The water content is a linear function of the degree of exchange, ranging from 20.54% for Na-A to 23.77% for 97.9% CaNa-A. The enthalpies of formation (from oxides) at 25 C are -74.50 1.21 kJ mol(-1) TO2 for hydrated zeolite Na-A and -30.79 1.64 kJ mol(-1) TO2 for hydrated zeolite 97.9% CaNa-A. Dehydration enthalpies obtained from differential scanning calorimetry are 32.0 kJ mol(-1) H2O for hydrated zeolite Na-A and 20.5 kJ mol(-1) H2O for hydrated zeolite 97.9% CaNa-A. Enthalpies of formation of Ca-exchanged zeolites A are less exothermic than for zeolite Na-A. A linear relationship between the formation enthalpy and the extent of calcium substitution was observed. The energetic effect of Ca-exchange on zeolite A is discussed with an emphasis on the complex interactions between the zeolite framework, cations, and water. PMID:25827491

  17. Impact of Zeolite Aging in Hot Liquid Water on Activity for Acid-Catalyzed Dehydration of Alcohols.

    PubMed

    Vjunov, Aleksei; Derewinski, Miroslaw A; Fulton, John L; Camaioni, Donald M; Lercher, Johannes A

    2015-08-19

    The location and stability of Brnsted acid sites catalytically active in zeolites during aqueous phase dehydration of alcohols were studied on the example of cyclohexanol. The catalytically active hydronium ions originate from Brnsted acid sites (BAS) of the zeolite that are formed by framework tetrahedral Si atom substitution by Al. Al K-edge extended X-ray absorption fine structure (EXAFS) and (27)Al magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopies in combination with density functional theory (DFT) calculations are used to determine the distribution of tetrahedral Al sites (Al T-sites) both qualitatively and quantitatively for both parent and HBEA catalysts aged in water prior to catalytic testing. The aging procedure leads to partial degradation of the zeolite framework evidenced from the decrease of material crystallinity (XRD) as well as sorption capacity (BET). With the exception of one commercial zeolite sample, which had the highest concentration of framework silanol-defects, there is no evidence of Al coordination modification after aging in water. The catalyst weight-normalized dehydration rate correlated best with the sum of strong and weak Brnsted acidic protons both able to generate the hydrated hydronium ions. All hydronium ions were equally active for the acid-catalyzed reactions in water. Zeolite aging in hot water prior to catalysis decreased the weight normalized dehydration reaction rate compared to that of the parent HBEA, which is attributed to the reduced concentration of accessible Brnsted acid sites. Sites are hypothesized to be blocked due to reprecipitation of silica dissolved during framework hydrolysis in the aging procedure. PMID:26237038

  18. Tin-containing silicates: alkali salts improve methyl lactate yield from sugars.

    PubMed

    Tolborg, Sren; Sdaba, Irantzu; Osmundsen, Christian M; Fristrup, Peter; Holm, Martin S; Taarning, Esben

    2015-02-01

    This study focuses on increasing the selectivity to methyl lactate from sugars using stannosilicates as heterogeneous catalyst. All group?I ions are found to have a promoting effect on the resulting methyl lactate yield. Besides, the alkali ions can be added both during the preparation of the catalyst or directly to the solvent mixture to achieve the highest reported yield of methyl lactate (ca. 75?%) from sucrose at 170?C in methanol. The beneficial effect of adding alkali to the reaction media applies not only to highly defect-free Sn-Beta prepared through the fluoride route, but also to materials prepared by post-treatment of dealuminated commercial Beta zeolites, as well as ordered mesoporous stannosilicates, in this case Sn-MCM-41 and Sn-SBA-15. These findings open the door to the possibility of using other preparation methods or different Sn-containing silicates with equally high methyl lactate yields as Sn-Beta. PMID:25605624

  19. UTILITY OF ZEOLITES IN REMOVAL OF INORGANIC AND ORGANIC WATER POLLUTANTS

    EPA Science Inventory

    Zeolites are well known for their ion exchange, adsorption and acid catalysis properties. Different inorganic and organic pollutants have been removed from water at room temperature using various zeolites. Synthetic zeolite Faujasite Y has been used to remove inorganic pollutants...

  20. A study of the alumina-silica gel adsorbent for the removal of silicic acid from geothermal water: increase in adsorption capacity of the adsorbent due to formation of amorphous aluminosilicate by adsorption of silicic acid.

    PubMed

    Yokoyama, Takushi; Ueda, Akira; Kato, Koichi; Mogi, Katsumi; Matsuo, Shorin

    2002-08-01

    Two kinds of adsorbents (Si adsorbent and Al adsorbent) for the removal of silicic acid from geothermal water to retard the formation of silica scales were prepared using silicic acid contained in geothermal water. The Si adsorbent was prepared by evaporating geothermal water, and the Al adsorbent was prepared by evaporating geothermal water after the addition of aluminum chloride. The specific surface area of the Si adsorbent was small and it's adsorption capacity of silicic acid was low. Although the specific surface area of the Al adsorbent was also small, it was significantly increased by the adsorption of silicic acid and it's adsorption capacity was high. Based on the change in the local structure of aluminum ion by the adsorption of silicic acid, the Al adsorbent was considered to be silica particles covered with crystalline aluminum hydroxide. Moreover, it was concluded that the increase in the specific surface area of the Al adsorbent and the decrease in the zeta potential were due to the formation of an amorphous aluminosilicate with a large surface area and a negative charge (one 4-coordinated Al) by the reaction between aluminum ions and silicic acids. PMID:16290755

  1. CO2 SEPARATIONS USING ZEOLITE MEMBRANES

    SciTech Connect

    Richard D. Noble; John L. Falconer

    2001-06-30

    Zeolite and other inorganic molecular sieve membranes have shown potential for separations based on molecular size and shape because of their small pore sized, typically less than 1 nm, and their narrow pore size distribution. The high thermal and chemical stability of these inorganic crystals make them ideal materials for use in high temperature applications such as catalytic membrane reactors. Most of the progress with zeolite membranes has been with MFI zeolites prepared on porous disks and tubes. The MFI zeolite is a medium pore size structure having nearly circular pores with diameters between .53 and .56 nm. Separation experiments through MFI membranes indicate that competitive adsorption separates light gas mixtures. Light gas selectivities are typically small, however, owing to small differences in adsorption strengths and their small sizes relative to the MFI pore opening. Furthermore, competitive adsorption does not work well at high temperature where zeolite membranes are stable and have potential application. Separation by differences in size has a greater potential to work at high temperature than competitive adsorption, but pores smaller than those in MFI zeolites are required. Therefore, some studies focused on the synthesis of a small, 8-membered-pore structures such as zeolite A (0.41-nm pore diameter) and SAPO-34, a chabazite (about .4-nm pore diameter with about 1.4 nm cages) analog. The small pore size of the zeolite A and SAPO-34 structures made the separation of smaller molecules by differences in size possible. Zeolite MFI and SAPO-34 membranes were prepared on the inside surface of porous alumina tubes by hydrothermal synthesis, and single gas and binary mixture permeances were measured to characterize the membrane's performance. A mathematical diffusion model was developed to determine the relative quantities of zeolite and non-zeolite pores in different membranes by modeling the permeation date of CO{sub 2}. This model expresses the total flux through the membrane as the sum of surface diffusion through zeolite pores and viscous flow and Knudsen diffusion through non-zeolite pores. As predicted by the model, the permeance of CO{sub 2} decrease with increasing pressure at constant pressure drop for membranes with few non-zeolite pores, but the permeance increased through viscous flow pores and was constant through pores allowing Knudsen diffusion. Membranes having more non-zeolite pores had lower CO{sub 2}/CH{sub 4} selectivities. The SAPO-34 membranes were characterized for light gas separation applications, and the separation mechanisms were identified. Single gas permeances of CO{sub 2}, N{sub 2}, and CH{sub 4} decreased with increasing kinetic diameter. For the best membrane at 300K, the He and H{sub 2} permeances were less than that of CO{sub 2}, because He, H{sub 2} and CO{sub 2} were small compared to the SAPO-34 pore, and differences in the heat of adsorption determined the permeance order. The small component permeated the fastest in CO{sub 2}/CH{sub 4}, CO{sub 2}/N{sub 2}, N{sub 2}/CH{sub 4}, H{sub 2}/CH{sub 4}, and H{sub 2}/N{sub 2} mixtures between 300 and 470 K. For H{sub 2}/CO{sub 2} mixtures, which were separated by competitive adsorption at room temperature, the larger component permeated faster below 400K. The room temperature CO{sub 2}/CH{sub 4} selectivity was 36 and decreased with temperature. The H{sub 2}/CH{sub 4} mixture selectivity was 8 and constant with temperature up to 480 K. Calcination, slow temperature cycles, and exposure to water vapor had no permanent effect on membrane performance, but temperature changes of approximately 30 K/min decreased the membrane's effectiveness. The effects of humidity on gas permeation were studied with SAPO-34 membranes of different qualities. Membranes with high CO{sub 2}/CH{sub 4} selectivities (greater than 20) were stable in water vapor under controlled conditions, but degradation was seen for some membranes. The degradation opened non-SAPO-34 pores that were larger than SAPO-34 pores as shown by the IC{sub 4}H{sub 10} permeance, CO{sub 2}/CH{sub 4} selectivity, and CO{sub 2} flux pressure dependence. In SAPO-34 pores, water apparently adsorbed and increased the gas permeances. Thus, the effect of water on gas permeation is a useful indicator of the membrane quality.

  2. Study on the order degree and geochemical characteristics of major elements of siliceous rock in eastern Qinling area, China.

    PubMed

    Ming, Lü; Li, Hong-Zhong; Zhao, Ming-zhen; Ma, Ming-wu; Yang, Zhi-Jun; Liang, Jin

    2014-11-01

    Siliceous rocks were extensively distributed in the marine volcanic sedimentary formation of Erlangping Group in the Early Paleozoic in eastern Qinling area. These siliceous rocks formed in the same age, but had differences in the degree of crystallization and order because of the late diagenetic evolution. In the present study, the major elements and order degree of the siliceous rocks were studied, which were from the Erlangping Group in Xixia area, Songxian area and Nanzhao area of eartern Qinling orogenic belt. As shown in the results, the siliceous rocks contained SiO2 with percentage between 84.75% and 94.12% and average of 89.09%. The SiO2/(K2O+Na2O) values were from 26.69 to 114.78 with 65.67 as its average, and the values of SiO2/Al2O3 were from 10.48 to 61.52 with average of 30.58. These above characteristics excellently agreed with the geochemical characteristics of hydrothermal siliceous rocks, which deposited in the continental margin environment. In the Raman analytical results, the quartz contributed to the characteristic Raman shifts at 394, 464, 465 and 467 cm(-1). In the results of Gaussian fitting the degrees of order increased with the order of siliceous rocks of Songxian area, Nanzhao area and Xixia area, which were witnessed by the descending in FWHM values of quartz in the siliceous rocks of Songxian area, Nanzhao area and Xixia area orderly. Disagreeing with the FWHM values of Gaussian fitting, the silica contents of the siliceous rocks had a rising trend of Songxian (87.36%), Nanzhao (89.57%), Xixia area (90.35%), which meant a descending in impurity elements with the order of Songxian area, Nanzhao area and Xixia areas. According to this, there was high agreement between lower crystallinity degree and higher purity of silica, and this denoted that the rising in order degree of silica would result in lower impurity in siliceous rocks. Although the crystallinity degrees could change with the influences of temperature, pressure and its natural property, the impurity elements decreased with the rising in crystallinity degrees of silica. Although there was excluding of impurity elements during the increase in degrees of crystallinity and order, the key factor for the diversities of major elements in siliceous rocks was not likely to be the excluding of impurity elements during the increase in the crystallinity degrees in silica In this study, the Raman analysis exhibited to be an effective way to understand the degree of order for the silica of the siliceous rocks, which would be a potential way to study the subsequent diagenetic evolution of siliceous rocks. PMID:25752047

  3. Studying the effect of zeolite inclusion in aluminum alloy on measurement of its surface hardness using laser-induced breakdown spectroscopy technique

    NASA Astrophysics Data System (ADS)

    Khalil, Osama Mostafa; Mingareev, Ilya; Bonhoff, Tobias; El-Sherif, Ashraf F.; Richardson, Martin C.; Harith, Mohamed Abdel

    2014-01-01

    Laser-induced breakdown spectroscopy (LIBS) has been used to study the surface hardness of special aluminum alloys containing zeolite. The aluminum alloy has acquired pronounced changes in its metallurgical properties due to the zeolite inclusion. The surface hardness of the samples under investigation is determined by measuring the spectral intensity ratios of the ionic to atomic spectral lines in the LIBS spectra of samples having different surface hardness values that have been conventionally measured before for comparison. The presence of aluminum silicate mineral in the studied alloys enabled material volume to expand under compression. This feature gave new results in the measurement of hardness via LIBS. It has been proven that the trend of the alloy density change complies with the increase of ionic to atomic spectral line intensity ratio.

  4. Polyamide 6/Layered Silicate Nanocomposites

    NASA Astrophysics Data System (ADS)

    D?bowska, M.; Rudzi?ska-Girulska, J.; Pig?owski, J.; Do??ga, J.

    2008-05-01

    Polyamide 6 (PA6) and its two exfoliated nanocomposites (PA6/Nf919 and PA6/BZ-COCO), with bentonite (2.5 wt.%) organophilically treated with different cations, were studied. Improved mechanical properties, changes in crystallinity and morphology as well as higher glass transition temperature values were observed for the nanocomposites in comparison to the neat PA6. For the nanocomposite PA6/BZ-COCO, of better surface modification of platelets and better interaction between the polymeric matrix and the organobentonite, higher values of Young's modulus and yielding point together with higher contribution of larger free volume holes to free volume distributions occurred.

  5. Identifying the Crystal Graveyards Remaining After Large Silicic Eruptions

    NASA Astrophysics Data System (ADS)

    Gelman, S. E.; Deering, C. D.; Bachmann, O.; Huber, C.; Gutiérrez, F. J.

    2014-12-01

    The accumulation of voluminous crystal-poor rhyolites from an upper crustal mush environment inherently necessitates the complementary formation of unerupted silicic cumulates. However, identification of such frozen cumulates remains controversial. This has motivated us to develop of a new geochemical model aimed at better constraining the behavior of trace elements in a magma reservoir concurrently tracking crystallization and imperfect segregation of melt. We use a numerical method to solve our model equations rather than seek analytical solutions, thereby relieving overly simplistic assumptions for the dependencies between partition coefficient or melt segregation rate as functions of crystallinity. Our model allows partition coefficient to vary depending on the crystallinizing mineralogy at any particular stage in magma cooling, as well as the ability to test different rates and efficiencies of crystal-melt segregation. We apply our model first to the Searchlight Pluton as a well-constrained case study, which allows us to quantitatively test existing interpretations of that pluton. Building on this, we broaden our model to better understand the relationship between volcanic and plutonic rocks utilizing the NAVDAT database. Our results produce unambiguous fractionation signatures for segregated melts, while those signatures are muted for their cumulate counterparts. These models suggest that some large granitiods may represent accumulations of crystals, having lost melt in some cases to volcanic eruptions or to higher level evolved plutonic units, although the trace element signature of this process is expected to be subtle.

  6. Chemical Interactions in Multimetal/Zeolite Catalysts

    SciTech Connect

    Sachtler, Wolfgang M. H.

    2004-04-16

    This two-year project has led to a significant improvement in the fundamental understanding of the catalytic action of zeolite-supported redox catalysts. It turned out to be essential that we could combine four strategies for the preparation of catalysts containing transition metal (TM) ions in zeolite cavities: (1) ion exchange from aqueous solution; (2) chemical vapor deposition (CVD) of a volatile halide onto a zeolite in its acidic form; (3) solid state ion exchange; and (4) hydrothermal synthesis of a zeolite having TM ions in its lattice, followed by a treatment transporting these ions to ''guest positions''. Technique (2) enables us to position more TM ions into cavities than permitted by the conventional technique (1).viz one positive charge per Al centered tetrahedron in the zeolite lattice. The additional charge is compensated by ligands to the TM ions, for instance in oxo-ions such as (GaO){sup +} or dinuclear [Cu-O-Cu]{sup 2+}. While technique (3) is preferred over CVD where volatile halides are not available, technique (4) leads to rather isolated ''ex lattice'' oxo-ions. Such oxo-ions tend to be mono-nuclear, in contrast to technique (2) which preferentially creates dinuclear oxo-ions of the same TM element. A favorable element for the present research was that the PI is also actively engaged in a project on the reduction of nitrogen oxides, sponsored by EMSI program of the National Science Foundation and the US Department of Energy, Office of Science. This combination created a unique opportunity to test and analyze catalysts for the one step oxidation of benzene to phenol and compare them with catalysts for the reduction of nitrogen oxides, using hydrocarbons as the reductant. In both projects catalysts have been used which contain Fe ions or oxo-ions in the cavities the zeolite MFI, often called ZSM-5. With Fe as the TM-element and MFI as the host zeolite we found that catalysts with high Fe content, prepared by technique (2) were optimal for the De-NO{sub x} reaction, but extremely unselective for benzene oxidation to phenol. Conversely, the catalysts prepared with (4) had the highest turnover frequency for benzene oxidation, but performed very poorly for NO{sub x} reduction with so-butane. In fact the Fe concentration in the former catalysts were so low that it was necessary to design a special experimental program for the sole purpose of showing that it is really the Fe which catalyzes the benzene oxidation, not some acid center as has been proposed by other authors. For this purpose we used hydrogen sulfide to selectively poison the Fe sites, without deactivating the acidic sites. In addition we could show that the hydrothermal treatment of catalysts prepared by technique (4) is essential to transform iron ions in the zeolite lattice to ''ex lattice ions'' in guest positions. That line of the work required very careful experimentation, because a hydrothermal treatment of a zeolite containing Fe ions in its cavities can also lead to agglomeration of such ions to nano-particles of iron oxide which lowers the selectivity for the desired formation of phenol. This part of the program showed convincingly that indeed Fe is responsible for the benzene oxidation catalysis. The results and conclusion of this work, including the comparison of different catalysts, was published in a number of papers in the scientific literature, listed in the attached list. In these papers also our analysis of the reaction orders and the possible mechanism of the used test reaction are given.

  7. The use of zeolites as slow release anthelmintic carriers.

    PubMed

    Dyer, A; Morgan, S; Wells, P; Williams, C

    2000-06-01

    This work examines the ability of commercial zeolite Y to act as a slow release agent for a number of anthelmintic drugs. Administration to rats, dosed with Nippostrongylus brasiliensis, of pyrantel and/or fenbendazole and pigs, dosed with Ascaris and Oesophagostomum, of dichlorvos (DDVP) loaded onto zeolite Y was more successful in killing adult worms than administration of the pure drug alone. The zeolite Y was used as supplied for initial studies and then later dealuminated for further studies. The drug loadings were monitored by thermal analysis and the loaded zeolites were used in several field trials. The results indicate that zeolite Y is a suitable vehicle for the slow release of some anthelmintics. The slow release of drug from the zeolite matrix improved its efficacy. PMID:10881284

  8. Preparation of Robust, Thin Zeolite Membrane Sheet for Molecular Separation

    SciTech Connect

    Liu, Wei; Zhang, Jian; Canfield, Nathan L.; Saraf, Laxmikant V.

    2011-10-19

    This paper reports a feasibility study on the preparation of zeolite membrane films on a thin, porous metal support sheet (50-{micro}m thick). Zeolite sodium A (NaA) and silicalite zeolite frameworks are chosen to represent synthesis of respective hydrophilic-type and hydrophobic-type zeolite membranes on this new support. It is found that a dense, continuous inter-grown zeolite crystal layer at a thickness less than 2 {micro}m can be directly deposited on such a support by using direct and secondary growth techniques. The resulting membrane shows excellent adhesion on the metal sheet. Molecular-sieving functions of the prepared membranes are characterized with ethanol/water separation, CO2 separation, and air dehumidification. The results show great potential to make flexible metal-foil-like zeolite membranes for a range of energy conversion and environmental applications.

  9. Atomic sites and stability of Cs+ captured within zeolitic nanocavities

    PubMed Central

    Yoshida, Kaname; Toyoura, Kazuaki; Matsunaga, Katsuyuki; Nakahira, Atsushi; Kurata, Hiroki; Ikuhara, Yumi H.; Sasaki, Yukichi

    2013-01-01

    Zeolites have potential application as ion-exchangers, catalysts and molecular sieves. Zeolites are once again drawing attention in Japan as stable adsorbents and solidification materials of fission products, such as 137Cs+ from damaged nuclear-power plants. Although there is a long history of scientific studies on the crystal structures and ion-exchange properties of zeolites for practical application, there are still open questions, at the atomic-level, on the physical and chemical origins of selective ion-exchange abilities of different cations and detailed atomic structures of exchanged cations inside the nanoscale cavities of zeolites. Here, the precise locations of Cs+ ions captured within A-type zeolite were analyzed using high-resolution electron microscopy. Together with theoretical calculations, the stable positions of absorbed Cs+ ions in the nanocavities are identified, and the bonding environment within the zeolitic framework is revealed to be a key factor that influences the locations of absorbed cations. PMID:23949184

  10. The ADOR mechanism for the synthesis of new zeolites.

    PubMed

    Eliov, Pavla; Opanasenko, Maksym; Wheatley, Paul S; Shamzhy, Mariya; Mazur, Michal; Nachtigall, Petr; Roth, Wieslaw J; Morris, Russell E; ?ejka, Ji?

    2015-10-21

    A novel methodology, called ADOR (assembly-disassembly-organisation-reassembly), for the synthesis of zeolites is reviewed here in detail. The ADOR mechanism stems from the fact that certain chemical weakness against a stimulus may be present in a zeolite framework, which can then be utilized for the preparation of new solids through successive manipulation of the material. In this review, we discuss the critical factors of germanosilicate zeolites required for application of the ADOR protocol and describe the mechanism of hydrolysis, organisation and condensation to form new zeolites starting from zeolite UTL. Last but not least, we discuss the potential of this methodology to form other zeolites and the prospects for future investigations. PMID:25946705

  11. Zeolite and swine inoculum effect on poultry manure biomethanation

    NASA Astrophysics Data System (ADS)

    Kougias, P. G.; Fotidis, I. A.; Zaganas, I. D.; Kotsopoulos, T. A.; Martzopoulos, G. G.

    2013-03-01

    Poultry manure is an ammonia-rich substrate that inhibits methanogenesis, causing severe problems to the anaerobic digestion process. In this study, the effect of different natural zeolite concentrations on the mesophilic anaerobic digestion of poultry waste inoculated with well-digested swine manure was investigated. A significant increase in methane production was observed in treatments where zeolite was added, compared to the treatment without zeolite.Methane production in the treatment with 10 g dm-3 of natural zeolite was found to be 109.75% higher compared to the treatment without zeolite addition. The results appear to be influenced by the addition of zeolite, which reduces ammonia toxicity in anaerobic digestion and by the ammonia-tolerant swine inoculum.

  12. Advanced zeolites used in FCC catalysts boost motor octane number

    SciTech Connect

    Letzsch, W.S.; Magee, J.S.; Upson, L.L.; Valeri, F. )

    1988-10-31

    Fluid catalytic cracking catalysts that contain an advanced zeolite called LZ-210, have been shown, by commercial trials, to increase the motor octane number (MON) of the FCC gasoline produced. The zeolite crystal utilizes lower unit cell size, lower sodium in the zeolite, less alumina debris in the zeolite structure, and silica reinsertion into the zeolite structure to accomplish the MON increase. Data from commercial trials are presented to support the MON increases, along with some explanations of how the advanced zeolite accomplishes them. A strong gasoline market and the removal of lead have combined to place a premium on clear gasoline octanes. Because gasoline from fluid catalytic cracking units is the largest segment of the refinery pool (up to 40%), its octane numbers are particularly important. Traditional emphasis has been on the research octance number (RON) but motor octanes frequently limit the blending process.

  13. Zeolite catalysis in conversion of cellulosics. Annual report

    SciTech Connect

    Tsao, G.T.

    1994-02-01

    The authors have studied the kinetics of oxylose/xylulose isomerization in significant detail over a variety of zeolites and obtained the pseudo-first order reaction rate constants. The authors have found that HY zeolite is still the best material and zeolites are more selective than homogeneous acid catalysts where decomposition of the sugar compounds is much faster. They have completed, as described in the Year 2 Work Plan, the study of cellobiose hydrolysis with an ion exchange resin. The kinetics of the solid-catalyzed reaction is qualitatively similar to that for catalysis by homogeneous acids. The planned program of NMR studies has revealed the dynamics of sugar molecules within the zeolite cavities. Two chemisorbed and a physisorbed state have been identified in HY zeolite. A new state, accounting for as much as a half of the sugar, has been found in ZSM-5 zeolite.

  14. Alkali Silicate Vehicle Forms Durable, Fireproof Paint

    NASA Technical Reports Server (NTRS)

    Schutt, John B.; Seindenberg, Benjamin

    1964-01-01

    The problem: To develop a paint for use on satellites or space vehicles that exhibits high resistance to cracking, peeling, or flaking when subjected to a wide range of temperatures. Organic coatings will partially meet the required specifications but have the inherent disadvantage of combustibility. Alkali-silicate binders, used in some industrial coatings and adhesives, show evidence of forming a fireproof paint, but the problem of high surface-tension, a characteristic of alkali silicates, has not been resolved. The solution: Use of a suitable non-ionic wetting agent combined with a paint incorporating alkali silicate as the binder.

  15. Crystalline rocks of the Spinatizha area, Pakistan

    NASA Astrophysics Data System (ADS)

    Lawrence, R. D.; Yeats, R. S.; Khan, S. H.; Subhani, A. M.; Bonelli, D.

    During the Cretaceous an andesitic arc developed across south Asia facing the Tethys Ocean. Remnants of this arc are preserved in Iran, Afghanistan, and the Chagai Hills and Kohistan, Pakistan. West of the Chaman fault near Spinatizha, Pakistan (33° 33'N, 66° 23'E) a terrain of crystalline rocks is exposed that links the Chagai Hills portion of this arc with the Kandahar portion of it in Afghanistan. Four units are present. (1) The Spinatizha Metamorphic Complex includes orthogneiss, greenschist, amphibolite, metavolcanics, marble and foliated muscovite granite. Extreme variation in rock type and degree of metamorphism characterises the entire complex. It is the oldest unit west of the Chaman fault in Pakistan. (2) The Bazai Ghar Volcanics consist of weakly deformed tuffs, flow breccias, and other coarse-grained pyroclastics of andesitic-arc type. Andesite flows and at least one silicic welded tuff are also present. The Bazai Ghar Volcanics are everywhere separated from the Spinatizha Metamorphic unit by granitic intrusions and a major fault. (3) Both the above units are intruded by a series of calc-alkaline granitic plutons ranging from diorite to granite. The silicic plutons generally intrude the more mafic ones. The Bazai Ghar Volcanics and related intrusions are probably equivalent to the Cretaceous (?) Sinjrani volcanics and the Cretaceous and younger intrusions of the Chagai Hills. (4) Along the fault zone between the volcanic and metamorphic rocks is a small area of previously unknown clastic sedimentary rocks: conglomerates and slates. The unit is of Palaeogene age but cannot yet be correlated with known units. The Spinatizha crystalline terrain extends south along the Chaman fault into Afghanistan and is covered by the Helmund desert to the west. It is the eastern continuation of the calc-alkaline arc terrain of the Chagai Hills dragged by oroclinal flexing into the Chaman transform zone. To the north it connects with the Kandahar volcanic arc. The metamorphic complex may represent the basement on which the arc terrain rests, only exposed due to strong vertical uplift near the Chaman fault.

  16. Zeolite membranes - a review and comparison with MOFs.

    PubMed

    Rangnekar, N; Mittal, N; Elyassi, B; Caro, J; Tsapatsis, M

    2015-10-21

    The latest developments in zeolite membranes are reviewed, with an emphasis on the synthesis techniques, including seed assembly and secondary growth methods. This review also discusses the current industrial applications of zeolite membranes, the feasibility of their use in membrane reactors and their hydrothermal stability. Finally, zeolite membranes are compared with metal-organic framework (MOF) membranes and the latest advancements in MOF and mixed matrix membranes are highlighted. PMID:26155855

  17. Zeolite (clinoptilolite) as feed additive to reduce manure mineral content.

    PubMed

    Leung, S; Barrington, S; Wan, Y; Zhao, X; El-Husseini, B

    2007-12-01

    Clinoptilolite (a species of zeolite) as grower hog feed additive can potentially improve nutrient ingestion and lower manure nutrient levels. A first objective was to establish the optimal particle size of the zeolite powder, as a fine size increases the adsorption surface while a coarse size can facilitate handling. The second objective tested the effect of feeding zeolite on manure nutrient levels. For the first objective, three zeolite powders (250-500 microm; 50-250 microm, and 50-500 microm) were exposed to an NH(4)(+) solution under a pH of either 7.0 or 2.0. The resulting solutions were tested for cation exchange. A commercial zeolite was also tested for the pH of 2.0 to evaluate zeolite stability. At 0%, 5% and 10% humidity, the same three particle size powders were subjected to shear tests to determine the zeolite's angle of friction. For the second objective using metabolic cages, female hogs were subjected to one of four rations (a control and three with zeolite) while collecting and analyzing their manures. For the first objective, the coarse particle zeolite performed best, adsorbing 158 and 123 Cmol(+)/kg of NH(4)(+) under neutral and acid pH, respectively, and releasing an equivalent amount of minerals only under neutral pH. The commercial zeolite with less clinoptilolite released more Al, Fe, Cu and Pb, showing less stability. The high internal angle of friction of zeolite did not vary with particle size and moisture, indicating funnel flow under gravity. For the second objective, hogs fed a zeolite diet produced manure with 15% and 22% less N and P, respectively, and demonstrated a better feed conversion, although not statistically significant (P>0.05). These results show that there is some potential in using high quality clinoptilolite in the ration of grower hogs. PMID:16905313

  18. Large zeolites - Why and how to grow in space

    NASA Technical Reports Server (NTRS)

    Sacco, Albert, Jr.

    1991-01-01

    The growth of zeolite crystals which are considered to be the most valuable catalytic and adsorbent materials of the chemical processing industry are discussed. It is proposed to use triethanolamine as a nucleation control agent to control the time release of Al in a zeolite A solution and to increase the average and maximum crystal size by 25-50 times. Large zeolites could be utilized to make membranes for reactors/separators which will substantially increase their efficiency.

  19. Fluoride-assisted synthesis of bimodal microporous SSZ-13 zeolite.

    PubMed

    Zhu, Xiaochun; Kosinov, Nikolay; Hofmann, Jan P; Mezari, Brahim; Qian, Qingyun; Rohling, Roderigh; Weckhuysen, Bert M; Ruiz-Martnez, Javier; Hensen, Emiel J M

    2016-02-11

    The presence of small amount of fluoride in alkaline hydrothermal synthesis of SSZ-13 zeolite yields bimodal microporous particles with substantially improved performance in the methanol-to-olefins (MTO) reaction. Hydrocarbon uptake measurements and fluorescence microspectroscopy of spent catalysts demonstrate enhanced diffusion through micropores at the grain boundaries of nanocrystals running through the zeolite particles. Fluoride-assisted SSZ-13 synthesis is a cheap and scalable approach to optimize the performance of MTO zeolite catalysts. PMID:26810114

  20. Crystalline beam ground state

    SciTech Connect

    Wei, Jie ); Li, Xiao-Ping; Sessler, A.M. )

    1993-01-01

    In order to employ Molecular Dynamics method, commonly used in condensed matter physics, we have derived the equations of motion for a beam of charged particles in the rotating rest frame of the reference particle. We include in the formalism that the particles are confined by the guiding and focusing magnetic fields, and that they are confined in a conducting vacuum pipe while interacting with each other via a Coulomb force. Numerical simulations has been performed to obtain the equilibrium structure. The effects of the shearing force, centrifugal force, and azimuthal variation of the focusing strength are investigated. It is found that a constant gradient storage ring can not give a crystalline beam, but that an alternating-gradient (AG) structure can. In such a machine the ground state is, except for one-dimensional (1-D) crystals, time-dependent. The ground state is a zero entropy state, despite the time-dependent, periodic variation of the focusing force. The nature of the ground state, similar to that found by Rahman and Schiffer, depends upon the density and the relative focusing strengths in the transverse directions. At low density, the crystal is 1-D. As the density increases, it transforms into various kinds of 2-D and 3-D crystals. If the energy of the beam is higher than the transition energy of the machine, the crystalline structure can not be formed for lack of radial focusing.

  1. Crystalline beam ground state

    SciTech Connect

    Wei, Jie; Li, Xiao-Ping; Sessler, A.M.

    1993-06-01

    In order to employ Molecular Dynamics method, commonly used in condensed matter physics, we have derived the equations of motion for a beam of charged particles in the rotating rest frame of the reference particle. We include in the formalism that the particles are confined by the guiding and focusing magnetic fields, and that they are confined in a conducting vacuum pipe while interacting with each other via a Coulomb force. Numerical simulations has been performed to obtain the equilibrium structure. The effects of the shearing force, centrifugal force, and azimuthal variation of the focusing strength are investigated. It is found that a constant gradient storage ring can not give a crystalline beam, but that an alternating-gradient (AG) structure can. In such a machine the ground state is, except for one-dimensional (1-D) crystals, time-dependent. The ground state is a zero entropy state, despite the time-dependent, periodic variation of the focusing force. The nature of the ground state, similar to that found by Rahman and Schiffer, depends upon the density and the relative focusing strengths in the transverse directions. At low density, the crystal is 1-D. As the density increases, it transforms into various kinds of 2-D and 3-D crystals. If the energy of the beam is higher than the transition energy of the machine, the crystalline structure can not be formed for lack of radial focusing.

  2. Comparing gas separation performance between all known zeolites and their zeolitic imidazolate framework counterparts.

    PubMed

    Gómez-Álvarez, Paula; Hamad, Said; Haranczyk, Maciej; Ruiz-Salvador, A Rabdel; Calero, Sofia

    2015-12-14

    To find optimal porous materials for adsorption-based separations is a challenging task due to the extremely large number of possible pore topologies and compositions. New porous material classes such as Metal Organic Frameworks (MOFs) are emerging, and hope to replace traditionally used materials such as zeolites. Computational screening offers relatively fast searching for candidate structures as well as side-by-side comparisons between material families. This work is pioneering at examining the families comprised by the experimentally known zeolites and their respective Zeolitic Imidazolate Framework (ZIF) counterparts in the context of a number of environmental and industrial separations involving carbon dioxide, nitrogen, methane, oxygen, and argon. Additionally, unlike related published work, here all the targeted structures have been previously relaxed through energy minimization. On the first level of characterization, we considered a detailed pore characterization, identifying 24 zeolites as promising candidates for gas separation based on adsorbate sizes. The second level involved interatomic potential-based calculations to assess the adsorption performance of the materials. We found no correlation in the values of heat of adsorption between zeolites and ZIFs sharing the same topology. A number of structures were identified as potential experimental targets for CO2/N2, and CO2/CH4 affinity-based separations. PMID:26600432

  3. Peculiarities of the dielectric response of natural zeolite composites prepared by using zeolite and silicon powders

    NASA Astrophysics Data System (ADS)

    Ozturk Koc, S.; Orbukh, V. I.; Eyvazova, G. M.; Lebedeva, N. N.; Salamov, B. G.

    2016-03-01

    We present the real and imaginary part of the dielectric permittivity of natural zeolite composites prepared by using zeolite and silicon powders. The dielectric response (DR) dependences on the frequency (3-300 GHz) of electric field and different Si concentrations (5-33%) are non-monotonic and a maximum peak is observed. This peak position is practically independent on the frequency and its maximum is observed in zeolite composites which included 9% of the Si-powder. Also the maximum peak is decreased by about an order of magnitude when frequency increases from 500 Hz to 5 kHz. Addition of the conductive Si-particles to zeolite-powder leads to two opposite effects. Firstly, the movement of electrons in the Si-particles provides increase of DR. Secondly, cations which leaving from zeolite pores can be neutralized by the particles of Si in the intercrystalline-space. Such a peculiar mechanism for recombination of Si electrons and cations from pores leads to a reduction of DR for large silicon concentrations. Due to the fact that the contribution of free carriers in the decreasing of the DR as the frequency increases, it is consistent with the suggestion that the maximum peak decreases with increasing frequency.

  4. Anomalous strain behavior in CO2-saturated zeolitic tuffs

    NASA Astrophysics Data System (ADS)

    Dralus, D. E.; Vanorio, T.; Mavko, G. M.

    2012-12-01

    Zeolites are aluminosilicate minerals with open, cage-like structures and negatively charged frames. Some naturally-occurring zeolites are stabile at geothermal temperatures and have cage structures large enough that small molecules can traverse the intracrystalline cage network easily. This, in addition to their negatively-charged frames, makes these zeolites strong adsorbents (and potentially absorbents) of carbon dioxide. We present a short series of experiments to determine what mechanical effects result from carbon dioxide interaction with zeolitic tuff samples. Three samples were tested: a non-zeolitized grey tuff from the Campi Flegrei region, a zeolitized yellow tuff from the same region, and a zeolite-rich tuff from southern California. The samples were tested in a hydrostatic pressure vessel up to 12 MPa confining pressure. Strains and ultrasonic acoustic velocities were measured under dry conditions as well as during helium injection and carbon dioxide injection. Results show acoustic velocities depend only on differential pressure and not on pore fluid type. Both zeolitized tuffs show decreased strain with gaseous carbon dioxide in the pore space; the decreased strain (or swelling) represents an 8%-16% deviation from the total strain in the helium-saturated case. This indicates that it is the interaction between zeolite minerals and carbon dioxide causing the anomalous strain readings.

  5. Zeolite Crystal Growth in Microgravity and on Earth

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Center for Advanced Microgravity Materials Processing (CAMMP), a NASA-sponsored Research Partnership Center, is working to improve zeolite materials for storing hydrogen fuel. CAMMP is also applying zeolites to detergents, optical cables, gas and vapor detection for environmental monitoring and control, and chemical production techniques that significantly reduce by-products that are hazardous to the environment. Shown here are zeolite crystals (top) grown in a ground control experiment and grown in microgravity on the USML-2 mission (bottom). Zeolite experiments have also been conducted aboard the International Space Station.

  6. Coreactant-induced modifications of catalytic behavior in zeolitic systems

    SciTech Connect

    Martin, A.M.; Chen, J.-K.; John, V.T. )

    1989-11-01

    The complex feed processing over zeolite catalysts, competitive reaction between the feed components results in observed rates and selectivities that cannot be predicted from pure component data alone. Hydroisomerization of paraffins over various Pt/zeolites in the presence of an aromatic cofeed is considered as an illustration. The aromatic affects paraffin reaction rates by occupying catalytic sites and perhaps also by partially blocking the pores. Analysis of Arrhenius plots helps in correlations of zeolite structure and the extent to which the paraffin reaction is affected. It is shown that the coreactant can induce selectivity to a zeolite that would otherwise not be shape selective.

  7. Method for the recovery of silver from silver zeolite

    DOEpatents

    Reimann, George A.

    1986-01-01

    High purity silver is recovered from silver exchanged zeolite used to capture radioactive iodine from nuclear reactor and nuclear fuel reprocessing environments. The silver exchanged zeolite is heated with slag formers to melt and fluidize the zeolite and release the silver, the radioactivity removing with the slag. The silver containing metallic impurities is remelted and treated with oxygen and a flux to remove the metal impurities. About 98% of the silver in the silver exchanged zeolite having a purity of 99% or better is recoverable by the method.

  8. Method for the recovery of silver from silver zeolite

    DOEpatents

    Reimann, G.A.

    1985-03-05

    High purity silver is recovered from silver exchanged zeolite used to capture radioactive iodine from nuclear reactor and nuclear fuel reprocessing environments. The silver exchanged zeolite is heated with slag formers to melt and fluidize the zeolite and release the silver, the radioactivity removing with the slag. The silver containing metallic impurities is remelted and treated with oxygen and a flux to remove the metal impurities. About 98% of the silver in the silver exchanged zeolite having a purity of 99% or better is recoverable by the method.

  9. Ion exchange properties of Japanese natural zeolites in seawater.

    PubMed

    Wajima, Takaaki

    2013-01-01

    Ion exchange properties of five different Japanese natural zeolites in seawater were examined. Sodium ions could be reduced by all zeolites, although anions, Cl(-) and SO(4)(2-), in seawater showed barely changes. Natural zeolite desalination treatment mainly depends on the ion exchange between Na(+), K(+) and Mg(2+) in seawater and Ca(2+) in natural zeolite. This study found that mordenite is superior to clinoptilolite for use in Na(+) reduction. Mordenite with high cation exchange capacity containing Ca(2+) resulted in the highest Na(+) reduction from seawater. PMID:23303099

  10. Dry method for recycling iodine-loaded silver zeolite

    DOEpatents

    Thomas, Thomas R.; Staples, Bruce A.; Murphy, Llewellyn P.

    1978-05-09

    Fission product iodine is removed from a waste gas stream and stored by passing the gas stream through a bed of silver-exchanged zeolite until the zeolite is loaded with iodine, passing dry hydrogen gas through the bed to remove the iodine and regenerate the bed, and passing the hydrogen stream containing the hydrogen iodide thus formed through a lead-exchanged zeolite which adsorbs the radioactive iodine from the gas stream and permanently storing the lead-exchanged zeolite loaded with radioactive iodine.

  11. Laser processing of siliceous materials

    NASA Astrophysics Data System (ADS)

    Panzner, Michael; Lenk, Andreas; Wiedemann, Guenter R.; Hauptmann, Jan; Weiss, Hans J.; Ruemenapp, Thomas; Morgenthal, Lothar; Beyer, Eckhard

    2000-08-01

    Laser processing of siliceous materials becomes increasingly important. Analogous to the laser processing of conventional materials there are applications in the fields of cleaning, surface processing, cutting, etc. The present paper concerns the state of the art and new applications: (1) Laser cleaning of natural stone surfaces. The good disability allows restoration work to be carried out conveniently, as for example the complete removal of crusts or the removal to such degree that moisture is not trapped beneath. (2) Non-slip finish of polished natural stone surfaces: The excellent focusing of laser beams on spots as small as 100 micrometer and below can be exploited to produce macroscopically invisible structures on the surfaces of different materials. This permits microscopically small craters and lentil shaped depressions to be generated on the stone surface. Therefore it is possible to provide a non-slip finish to polished natural stone surfaces without noticeably impairing the gloss. (3) Concrete cutting: In Europe, and particularly in Germany, there is a growing demand for redevelopment of concrete apartment buildings, involving the removal of non-bearing walls and the cutting of openings. The temporal relocation of residents due to the noise and moisture from the use of diamond tools could be avoided by applying a laser cutting technology. With a 3 kW-Nd-YAG-laser, 70 mm concrete can be cut with rates up to 25 mm/min.

  12. Organically modified silicate aerogels, ``Aeromosils``

    SciTech Connect

    Kramer, S.J.; Mackenzie, J.D.; Rubio-Alonso, F.

    1996-12-31

    Aerogels derived from sol-gel oxides such as silica have become quite scientifically popular because of their extremely low densities, high surface areas, and their interesting optical, dielectric, thermal and acoustic properties. However, their commercial applicability has thus far been rather limited, due in great part to their brittleness and hydrophilicity. In prior work by the research group, modifying silicate gel structures with flexible, organic containing polymers such as polydimethylsiloxane imparted significant compliance (even rubbery behavior) and hydrophobicity. These materials have been referred to as Ormosils. This study expounds on the current effort to extend these desirable properties to aerogels, and in-so-doing, creating novel ``Aeromosils``. Reactive incorporation of hydroxy-terminal polydimethylsiloxane (PDMS) into silica sol-gels was made using both acid and two-step acid/base catalyzed processes. Aerogels were derived by employing the supercritical CO{sub 2} technique. Analyses of microstructure were made using nitrogen adsorption (BET surface area and pore size distribution), and some mechanical strengths were derived from tensile strength testing. Interesting Aeromosil properties obtained include optical transparency, surface areas of up to 1,200 m{sup 2}/g, rubberiness, and better strength than corresponding silica aerogels with elongations at break exceeding 5% in some cases.

  13. Improved alkali-metal/silicate binders

    NASA Technical Reports Server (NTRS)

    Schutt, J.

    1978-01-01

    Family of inorganic binders utilizes potassium or sodium oxide/silicate dispersion and employs high mole ratio of silicon dioxide to alkali-metal binder. Binders are stable, inexpensive, extremely water resistant, and easy to apply.

  14. Siliceous microfossil extraction from altered Monterey rocks

    SciTech Connect

    Nelson, C.O.; Casey, R.E.

    1986-04-01

    Samples of altered Monterey rocks of differing lithologies were processed by various methods to develop new techniques for extracting siliceous microfossils. The preliminary use of thin sections made from the same rocks reduced the number of probable samples (samples worth further processing) by about one-third. Most of the siliceous microfossils contained in altered Monterey rocks appear to be highly recrystallized and are extremely fragile; however, some contained silicified and silica-infilled radiolarians and planktonic and benthonic foraminifera, which are very tough. In general the most useful techniques were gently hydrochloric acid, hydrogen peroxide, formic acid, monosodium glutamate, and regular siliceous microfossil extraction techniques. Unsuccessful techniques and a new siliceous microfossil flotation technique are also documented.

  15. Highly silicic compositions on the Moon.

    PubMed

    Glotch, Timothy D; Lucey, Paul G; Bandfield, Joshua L; Greenhagen, Benjamin T; Thomas, Ian R; Elphic, Richard C; Bowles, Neil; Wyatt, Michael B; Allen, Carlton C; Donaldson Hanna, Kerri; Paige, David A

    2010-09-17

    Using data from the Diviner Lunar Radiometer Experiment, we show that four regions of the Moon previously described as "red spots" exhibit mid-infrared spectra best explained by quartz, silica-rich glass, or alkali feldspar. These lithologies are consistent with evolved rocks similar to lunar granites in the Apollo samples. The spectral character of these spots is distinct from surrounding mare and highlands material and from regions composed of pure plagioclase feldspar. The variety of landforms associated with the silicic spectral character suggests that both extrusive and intrusive silicic magmatism occurred on the Moon. Basaltic underplating is the preferred mechanism for silicic magma generation, leading to the formation of extrusive landforms. This mechanism or silicate liquid immiscibility could lead to the formation of intrusive bodies. PMID:20847267

  16. Oxidation of the Ru(0001) surface covered by weakly bound, ultrathin silicate films

    NASA Astrophysics Data System (ADS)

    Emmez, Emre; Anibal Boscoboinik, J.; Tenney, Samuel; Sutter, Peter; Shaikhutdinov, Shamil; Freund, Hans-Joachim

    2016-04-01

    Bilayer silicate films grown on metal substrates are weakly bound to the metal surfaces, which allows ambient gas molecules to intercalate the oxide/metal interface. In this work, we studied the interaction of oxygen with Ru(0001) supported ultrathin silicate and aluminosilicate films at elevated O2 pressures (10- 5-10 mbar) and temperatures (450-923 K). The results show that the silicate films stay essentially intact under these conditions, and oxygen in the film does not exchange with oxygen in the ambient. O2 molecules readily penetrate the film and dissociate on the underlying Ru surface underneath. The silicate layer does however strongly passivate the Ru surface towards RuO2(110) oxide formation that readily occurs on bare Ru(0001) under the same conditions. The results indicate considerable spatial effects for oxidation reactions on metal surfaces in the confined space at the interface. Moreover, the aluminosilicate films completely suppress the Ru oxidation, providing some rationale for using crystalline aluminosilicates in anti-corrosion coatings.

  17. Influence of Silicate Melt Composition on Metal/Silicate Partitioning of W, Ge, Ga and Ni

    NASA Technical Reports Server (NTRS)

    Singletary, S. J.; Domanik, K.; Drake, M. J.

    2005-01-01

    The depletion of the siderophile elements in the Earth's upper mantle relative to the chondritic meteorites is a geochemical imprint of core segregation. Therefore, metal/silicate partition coefficients (Dm/s) for siderophile elements are essential to investigations of core formation when used in conjunction with the pattern of elemental abundances in the Earth's mantle. The partitioning of siderophile elements is controlled by temperature, pressure, oxygen fugacity, and by the compositions of the metal and silicate phases. Several recent studies have shown the importance of silicate melt composition on the partitioning of siderophile elements between silicate and metallic liquids. It has been demonstrated that many elements display increased solubility in less polymerized (mafic) melts. However, the importance of silicate melt composition was believed to be minor compared to the influence of oxygen fugacity until studies showed that melt composition is an important factor at high pressures and temperatures. It was found that melt composition is also important for partitioning of high valency siderophile elements. Atmospheric experiments were conducted, varying only silicate melt composition, to assess the importance of silicate melt composition for the partitioning of W, Co and Ga and found that the valence of the dissolving species plays an important role in determining the effect of composition on solubility. In this study, we extend the data set to higher pressures and investigate the role of silicate melt composition on the partitioning of the siderophile elements W, Ge, Ga and Ni between metallic and silicate liquid.

  18. Acidity of two-dimensional zeolites.

    PubMed

    Rybicki, Marcin; Sauer, Joachim

    2015-11-01

    Hybrid quantum mechanics:molecular mechanics (QM/MM) calculations of absolute deprotonation energies are performed with periodic boundary conditions for Brnsted sites of aluminosilicate bilayers with various Al/Si ratios (two-dimensional zeolite). The supercell method is applied and density functional theory is used. Much lower values are obtained (1042, 1069 and 1091 kJ mol(-1) for Al/Si = 1/63, 1/7 and 1/3, respectively) than those for bulk zeolites (1233 kJ mol(-1) for H-chabazite with Al/Si = 1/11). We ascribe the much lower deprotonation energy to the smaller effective dielectric constant (1.6-1.9) of an ultra-thin dielectric in a vacuum compared to that of the corresponding bulk systems (3.0 for H-chabazite), which leads to a better stabilization of the charge created upon deprotonation. PMID:26437870

  19. Electrical Response of PEDOT-PSS/FAU Zeolite Composites toward SO2: Controlling the Adsorption Properties of FAU Zeolite

    NASA Astrophysics Data System (ADS)

    Chanthaanont, Pojjawan; Sirivat, Anuvat

    2012-02-01

    In our work, we propose to combine a conductive polymer, Poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonic acid) (PEDOT-PSS), with FAU zeolites to investigate the potential of the composites for use as SO2 sensing materials.Composites with PEDOT-PSS as a matrix containing faujasite zeolites of various cation types (divalent transition metal ions: Fe^2+, Co^2+, Ni^2+ and Cu^2+), were fabricated to investigate the effect of the cation type of the faujasite zeolites on the electrical conductivity response when exposed to SO2. The composite was tested through repeated sensing and recovery processes to investigate the reversibility and reproducibility. During the recovery process, the electrical conductivity of the composites were recovered, which proves that the sensing characteristics are repeatable. Responses and the interaction mechanism of the conductive polymer/zeolite composites were investigated. The composite with 20% (v/v) of zeolite content gives the highest sensitivity. The electrical conductivity responses of PEDOT-PSS/Zeolite composites can be altered due to the available adsorption sites for gas molecules. The addition of zeolites to the pristine PEDOT-PSS improved the electrical conductivity sensitivity of the composites by enhancing the interaction between PEDOT-PSS and SO2. The type of cation in the zeolite pores effected the sensitivity of the composites, depending on the acidity of the ion-exchanged zeolites.

  20. Bis-GMA/TEGDMA Dental Composites Reinforced with Electrospun Nylon 6 Nanocomposite Nanofibers Containing Highly Aligned Fibrillar Silicate Single Crystals

    PubMed Central

    Tian, Ming; Gao, Yi; Liu, Yi; Liao, Yiliang; Xu, Riwei; Hedin, Nyle E.; Fong, Hao

    2007-01-01

    The objective of this research was to study the reinforcement of electrospun nylon 6/fibrillar silicate nanocomposite nanofibers on Bis-GMA/TEGDMA dental composites. The hypothesis was that the uniform distribution of nano-scaled and highly aligned fibrillar silicate single crystals into electrospun nylon 6 nanofibers would improve the mechanical properties of the resulting nanocomposite nanofibers, and would lead to the effective reinforcement of dental composites. The nylon 6/fibrillar silicate nanocomposite nanofibers were crystalline, structurally oriented and had an average diameter of approximately 250 nm. To relatively well distribute nanofibers in dental composites, the nanofiber containing composite powders with a particle structure similar to that in interpenetration networks were prepared first, and then used to make the dental composites. The results indicated that small mass fractions (1 % and 2 %) of nanofiber impregnation improved the mechanical properties substantially, while larger mass factions (4 % and 8 %) of nanofiber impregnation resulted in less desired mechanical properties. PMID:17940586

  1. Thermodynamics and Kinetics of Silicate Vaporization

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Costa, Gustavo C. C.

    2015-01-01

    Silicates are a common class of materials that are often exposed to high temperatures. The behavior of these materials needs to be understood for applications as high temperature coatings in material science as well as the constituents of lava for geological considerations. The vaporization behavior of these materials is an important aspect of their high temperature behavior and it also provides fundamental thermodynamic data. The application of Knudsen effusion mass spectrometry (KEMS) to silicates is discussed. There are several special considerations for silicates. The first is selection of an appropriate cell material, which is either nearly inert or has well-understood interactions with the silicate. The second consideration is proper measurement of the low vapor pressures. This can be circumvented by using a reducing agent to boost the vapor pressure without changing the solid composition or by working at very high temperatures. The third consideration deals with kinetic barriers to vaporization. The measurement of these barriers, as encompassed in a vaporization coefficient, is discussed. Current measured data of rare earth silicates for high temperature coating applications are discussed. In addition, data on magnesium-iron-silicates (olivine) are presented and discussed.

  2. Silicate Abundance and its Significance in the Hooghly-Matla Estuary, India (Invited)

    NASA Astrophysics Data System (ADS)

    Ghosh, T.; Akhand, A.

    2010-12-01

    Sea water contains in suspension a wide spectrum of siliceous materials. The surface water abounds with organisms such as diatoms and radiolarians having skeletons composed of non-crystalline form of hydrated silica. A very high level of silicate (130-140 ?M) noticed in the Bay of Bengal nearer the confluence of the rivers, where nutrient levels are appreciably higher during southwest monsoon period (March-October) in contrast to other seasons (CSMCRI, 2007). The relatively high (>5 g) silicate values at the Ganges head (Bay of Bengal) is attributable to river runoff during the same period (CSMCRI, 2007). In general, the concentration of inorganic phosphate, nitrate and silicate increased in the direction of Antarctic Sea, particularly around 40 S latitude, in the proximity of sub-tropical convergence. In comparison to Atlantic and Pacific oceans, the concentration of nutrients in the Indian Ocean is almost twice (Venkataramana, 2007). The mean value of 102.943.2 ?M for silicate in Hooghly estuary is found lower than worldwide average river water concentration of 147.893.6 ?M (Gems, 2002). Seasonal variation of river runoff of silicate shows maximum value of 12.6109 mol during monsoon; thereafter, its value decreased to 2.54 and 1.33109 mol during post-monsoon and pre-monsoon, respectively. The net residual flows of 4.91, 1.47 and 0.5109 mol and the exchange flux of 6.95, 0.94 and 0.51109 mol is found at the estuary during monsoon, post-monsoon and pre-monsoon, respectively. The annual flux of silicate out of the estuary is estimated to be 15.28109 mol (428103 t), about 93% of the total fluvial flux. The non-conservative flux of silicate removed from the water column is found to be 1.12 109 mol (31.0103 t), which is about 5% in the global scale (0.6106 t year-1) (Tregguer et al.,1995). Nitrate, Phosphate and Silicate, have been studied in the Hooghly-Matla estuarine complex and compared with selected previous studies. It is observed that both nitrate and phosphate concentrations remained almost stable varied (between 19.28 and 19.4?M for DIN and between 1.61and 1.99?M for DRP) during the period between 1975 and 2001, but silicate shows a distinct increasing trend from 35.6 to 102.9?M (Nandy et al., 1983; NIO, 1986; Ghosh et al., 1992). These also conforms our study, with the concentration of silicate from 19.97 M to 72.73 M during pre-monsoon and 48.26 M to 103.19 M during the monsoon in the Hooghly-Matla estuarine complex. High concentrations of biogenic silica in tidal marshes are necessary for maximum benthic diatom production which in turn helps high secondary production of commercial fish and crustaceans (Courtney, 2007). The Gross Primary Productivity is found to be increased in three stations of these estuaries (27.325.06 mg/m3/ hr in 1990, 33.5814 mg/m3/ hr in 2000 and 44.365.91 mg/m3/ hr in 2007) (Biswas et. al., 2009), with the increasing trend of silicate within this estuarine complex. The increasing trend of total catches in the Eastern and Western Indian Ocean (FAO, 1998), of which the Bay of Bengal is an important part (Islam, 2003), justify the interrelation. Thus, these findings are ascertaining the interrelation between the increasing trend of silicate concentration with the enhanced primary productivity, which in turn increase the fish yield in the Hooghly-Matla estuarine complex on the Bay of Bengal.

  3. Liquid crystalline polymers

    NASA Technical Reports Server (NTRS)

    1990-01-01

    The remarkable mechanical properties and thermal stability of fibers fabricated from liquid crystalline polymers (LCPs) have led to the use of these materials in structural applications where weight savings are critical. Advances in processing of LCPs could permit the incorporation of these polymers into other than uniaxial designs and extend their utility into new areas such as nonlinear optical devices. However, the unique feature of LCPs (intrinsic orientation order) is itself problematic, and current understanding of processing with control of orientation falls short of allowing manipulation of macroscopic orientation (except for the case of uniaxial fibers). The current and desirable characteristics of LCPs are reviewed and specific problems are identified along with issues that must be addressed so that advances in the use of these unique polymers can be expedited.

  4. Nanocomposites with Crystalline Polymers

    NASA Astrophysics Data System (ADS)

    Kumar, Sanat

    2015-03-01

    The creation of ordered (layered) biomimetic materials typically follows a series of steps: first mix nanoparticles with water, organize the NPs by ice templating, evaporate the ice and then back fill with metal or polymer. We propose a simple method exploiting the in situ self-assembly of a crystalline polymer in the presence of nanoparticles to facilitate this process, and provide a completely new pathway for the synthesis of biomimetic materials. A suite of complementary experimental tools are used in this analysis. In parallel, we are developing theoretical tools to a priori predict the morphologies adopted by semicrystalline polymers. The convergence of these novel experimental and theoretical developments in the venerable field of semicrystalline polymers could lead to new applications for this largest class of commercially relevant polymeric materials. With Jacques Jestin, Brian Benicewicz, Dan Zhao, Longxi Zhao

  5. Structural and diffusion characterizations of steam-stable mesostructured zeolitic UL-ZSM-5 materials.

    PubMed

    Vinh-Thang, Hoang; Huang, Qinglin; Ungureanu, Adrian; Ei?, Mladen; Trong-On, Do; Kaliaguine, Serge

    2006-05-01

    A series of mesoporous UL-ZSM-5 materials (Si/Al = 50) with different micro- and mesoporosity as well as crystallinity was prepared following the procedure proposed in one of our recent studies (Trong-On, D.; Kaliaguine, S. Angew. Chem. Int. Ed. 2001, 40, 3248-3251. Trong-On, D.; Kaliaguine, S. U.S. Patent 6,669,924, B1, 2003). These materials have zeolitic structure in the form of nanoparticles intergrown in the walls of the amorphous wormhole-like aluminosilicate mesopores of Al-Meso-50, which was used as a precursor in the synthesis. The structure, crystallinity, and textural properties of the synthesized materials, as well as a reference ZSM-5 zeolite sample, were determined by X-ray diffraction (XRD), transmission electron microscopy (TEM)/scanning electron microscoy (SEM) analyses, Fourier transform infrared spectroscopy (FTIR), 27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR), and nitrogen adsorption/desorption techniques. The acid properties were examined by FTIR of adsorbed pyridine. UL-ZSM-5 materials were shown to be highly hydrothermally stable. The diffusion of two C7 hydrocarbons, i.e., n-heptane and toluene, in four UL-ZSM-5 materials with different microporosities, related acidities, and crystallinities were investigated using the zero-length column (ZLC) method. Furthermore, the wormhole-like mesostructured aluminosilicate precursor (Al-Meso-50) and a reference MFI zeolite sample were also investigated using the same technique. A theoretical model considering a combination of mesopore diffusion (with surface slip in the main channels) with an activated, mainly surface diffusion mechanism in the intrawall biporous structure, was proposed and employed to interpret the experimental ZLC results. A classical Knudsen type of diffusion was replaced by an activated surface slip type of diffusion mechanism in the mesopores. The transport of n-heptane in UL-ZSM-5 materials was found to be mainly controlled by mesopore diffusion in the main-channel structure, while that of toluene was dominated by the intrawall diffusion process. Diffusion activation energies of n-heptane are about 2 times higher in comparison to toluene, which has a larger kinetic diameter. The main mesopore channel structure seems to appreciably contribute to the overall mass transport. Furthermore, the effect of hydrothermal treatment (20% steam at 800 degrees C for 24 h) on the diffusion of these two sorbates on UL-ZSM-5 materials was also evaluated. PMID:16649795

  6. Crystallization of neodymium-rich phases in silicate glasses developed for nuclear waste immobilization

    NASA Astrophysics Data System (ADS)

    Caurant, D.; Majerus, O.; Loiseau, P.; Bardez, I.; Baffier, N.; Dussossoy, J. L.

    2006-08-01

    Glass-ceramics containing neodymium-rich crystalline phases can be obtained by crystallization of silicate glasses (nucleation + crystal growth heat treatments) or by controlled cooling of melts. Such materials could be envisaged as durable matrices for conditioning minor actinides- and Pu-rich nuclear wastes if the partitioning ratio of the wastes between crystalline phase and residual glass is high (principle of double containment barrier). In radioactive waste forms, Nd would be partially substituted by actinides and neutron absorbers (Gd). In this work, two silicate glass compositions leading to efficient nucleation and crystallization of either zirconolite (Ca 1- xNd xZrTi 2- xAl xO 7, x < 1) or apatite (Ca 2Nd 8Si 6O 26) in their bulk were studied as potential waste forms. The effect of the method used to prepare glass-ceramics (controlled cooling from the melt or nucleation + crystal growth from the glass) on both the microstructure and the structure of the neodymium-rich crystalline phase was studied. The highest number of zirconolite or apatite crystals in the bulk was obtained using the nucleation + crystal growth method. However, the percentage of neodymium incorporated in zirconolite crystals remained too small to make realistic the use of such materials for the conditioning of actinides in comparison with more durable bulk ceramics.

  7. New antiaxillary odour deodorant made with antimicrobial Ag-zeolite (silver-exchanged zeolite).

    PubMed

    Nakane, T; Gomyo, H; Sasaki, I; Kimoto, Y; Hanzawa, N; Teshima, Y; Namba, T

    2006-08-01

    The causative substances for axillary osmidrosis, which are often found in apocrine sweat, are the decomposed/denatured products of short-chain fatty acid and other biological metabolite compounds produced by axillary-resident bacteria. Conventional underarm deodorants suppress the process of odour production mostly by the following mechanism: (1) suppression of perspiration, (2) reduction in numbers of resident bacteria, (3) deodorization and (4) masking. The most important and effective method to reduce odour is to suppress the growth of resident bacteria with antimicrobials, which have several drawbacks, especially in their safety aspect. To solve these problems, we focused on Ag-zeolite (silver-exchanged zeolite) that hold stable Ag, an inorganic bactericidal agent, in its structure, and therefore, poses less risk in safety. Its bactericidal effect on skin-resident bacteria was found to be excellent and comparable with that of triclosan, a most frequently used organic antimicrobial in this product category. The dose-response study of Ag-zeolite powder spray (0-40 w/w%) using 39 volunteers revealed that 5-40 w/w% Ag-zeolite could show a sufficient antimicrobial effect against skin-resident bacteria. The comparison study using 0.2 w/w% triclosan as the control and 10 w/w% Ag-zeolite indicated that: (1) one application of the powder spray containing 10 w/w% Ag-zeolite could show a sufficient antimicrobial effect against the resident bacteria and its effect continued for 24 h, (2) a powder spray containing 0.2 w/w% triclosan was unable to show a sufficient antimicrobial effect, and (3) no adverse event was observed. These studies show that Ag-zeolite has a superior antimicrobial ability that is rarely found in conventional antimicrobials used in deodorant products and a strong antiaxillary odour deodorant ability because of its long-lasting effect. During clinical study, patch tests with humans and other clinical studies of this product showed no adverse events related to the treatment with the Ag-zeolite product. PMID:18489270

  8. Fluorine-19 NMR Study of the Environment of Fluorine in Silicate and Aluminosilicate Oxyfluoride Glasses.

    NASA Astrophysics Data System (ADS)

    Kiczenski, T. J.; Stebbins, J. F.

    2002-12-01

    Using a compilation of F-19 NMR chemical shift values for crystalline model compounds, we have explored the local fluorine environment in several silicate and aluminosilicate oxyfluoride glasses. The F-19 MAS NMR spectrum of the Mg-silicate glass consists of a broad peak centered at -170 ppm, which encompasses the F-Mg(3) environments (where "3" is the number of Mg neighbors) of crystalline MgF2 (-195 ppm) and phlogopite (-175 ppm). The predominant environment in the glass is consequently assigned to F-Mg(n), where "n" indicates an unknown number of nearest neighbors. The magnesium aluminosilicate glass spectra all consist of a major feature at about -175 ppm and a shoulder at approximately -145 ppm. Based on the model compound data, the shoulder lies in the region attributed to Al-F-M2+ sites, and it was observed that glasses with a higher Al/Mg ratio featured extra intensity in the high-frequency shoulder. The shoulder is consequently assigned to Al-F-Mg(n), while the major feature is attributed to F-Mg(n) sites. This indicates that Mg is decidedly more effective in bonding to fluorine than either Ca or Ba in aluminosilicate glasses, following the trend established in our previous work on the Ba- and Ca-aluminosilicate glasses (the higher field strength modifier cation is more effective in competing with Al). Fluorine preferentially bonding with the modifier cation over aluminum has, to our knowledge, never been previously observed in aluminosilicate glasses. Spectra for Na-La-silicate glasses are characterized by an extremely wide peak (hundreds of ppm) and a relatively narrow peak at -220 ppm. The narrow peak at -220 ppm is assigned to F-Na(n) due to its proximity to the chemical shift of F-Na(6) (-225 ppm, from crystalline NaF). The small relative area of the F-Na(n) peak indicates a pronounced preference for F-La bonds over F-Na bonds, which is consistent with the findings of the previously discussed aluminosilicates. The massive, broad feature encapsulates the region described by the mixed fluorine environments of crystalline NaLaF4 (-30 to -63 ppm), and has therefore been assigned to a wide variety of fluorine environments, consisting of F-La bonds in a mixed environment with some number of F-Na bonds. In order to explore La-F clustering we have employed "echo" experiments, which can provide information about F-F distances. In the Na-La-silicates, the broad feature decays much faster than the F-Na(n) peak, indicating a shorter F-F distance in the sites associated with La. This is not consistent with random anion distribution but can be easily explained by the formation of fluorine-rich clusters. This may provide insight into the mechanism for the onset of crystallization in glass ceramics. In the long echo-time experiments on the Na-La-silicate glasses, the intensity of the broad feature was virtually gone, and the intensity of the F-Na(n) peak was largely decreased. This allowed us to clearly observe another peak centered at -140 ppm. This is near the peak found for the Si-F-Na(2) structure (-152 ppm) in the model compounds. Further examination of the original one-pulse spectra revealed the presence of this peak in small quantities in all compositions. Its relative intensity (about 2 percent of the total intensity) is comparable to that of Si-F-Ba(n) and Si-F-Na(n) bonding found in the fluorine containing Ba-silicate and Na-silicate glasses (respectively) from our previous studies. This suggests that Si-F bonding is independent of composition and may be an intrinsic characteristic of fluorine-containing silicate glasses.

  9. A vibrational spectroscopic study of the silicate mineral pectolite - NaCa₂Si₃O₈(OH).

    PubMed

    Frost, Ray L; López, Andrés; Theiss, Frederick L; Romano, Antônio Wilson; Scholz, Ricardo

    2015-01-01

    The mineral pectolite NaCa₂Si₃O₈(OH) is a crystalline sodium calcium silicate which has the potential to be used in plaster boards and in other industrial applications. Raman bands at 974 and 1026 cm(-1) are assigned to the SiO stretching vibrations of linked units of Si₃O₈ units. Raman bands at 974 and 998 cm(-1) serve to identify Si₃O₈ units. The broad Raman band at around 936 cm(-1) is attributed to hydroxyl deformation modes. Intense Raman band at 653 cm(-1) is assigned to OSiO bending vibration. Intense Raman bands in the 2700-3000 cm(-1) spectral range are assigned to OH stretching vibrations of the OH units in pectolite. Infrared spectra are in harmony with the Raman spectra. Raman spectroscopy with complimentary infrared spectroscopy enables the characterisation of the silicate mineral pectolite. PMID:25004896

  10. Preparation and screening of crystalline zeolite and hydrothermally-synthesized materials

    DOEpatents

    Schultz, Peter G.; Xiang, Xiaodong; Goldwasser, Isy; Briceno, Gabriel; Sun, Xiao-Dong; Wang, Kai-An

    2005-03-08

    Methods and apparatus for the preparation and use of a substrate having an array of diverse materials in predefined regions thereon. A substrate having an array of diverse materials thereon is generally prepared by delivering components of materials to predefined regions on a substrate, and simultaneously reacting the components to form at least two materials. Materials which can be prepared using the methods and apparatus of the present invention include, for example, covalent network solids, ionic solids and molecular solids. More particularly, materials which can be prepared using the methods and apparatus of the present invention include, for example, inorganic materials, intermetallic materials, metal alloys, ceramic materials, organic materials, organometallic materials, non-biological organic polymers, composite materials (e.g., inorganic composites, organic composites, or combinations thereof), etc. Once prepared, these materials can be screened for useful properties including, for example, electrical, thermal, mechanical, morphological, optical, magnetic, chemical, or other properties. Thus, the present invention provides methods for the parallel synthesis and analysis of novel materials having useful properties.

  11. Steps toward interstellar silicate dust mineralogy

    NASA Technical Reports Server (NTRS)

    Dorschner, J.; Guertler, J.; Henning, TH.

    1989-01-01

    One of the most certain facts on interstellar dust is that it contains grains with silicon oxygen tetrahedra (SOT), the internal vibrations of which cause the well known silicate bands at 10 and 18 microns. The broad and almost structureless appearance of them demonstrates lack of translation symmetry in these solids that must be considered amorphous or glassy silicates. There is no direct information on the cations in these interstellar silicates and on the number of bridging oxygens per tetrahedron (NBO). Comparing experimental results gained on amorphous silicates, e.g., silicate glasses, of cosmically most abundant metals (Mg, Fe, Ca, Al) with the observations is the only way to investigate interstellar silicate dust mineralogy (cf, Dorschner and Henning, 1986). At Jena University Observatory IR spectra of submicrometer-sized grains of pyroxene glasses (SSG) were studied. Pyroxenes are common minerals in asteroids, meteorites, interplanetary, and supposedly also cometary dust particles. Pyroxenes consist of linearly connected SOT (NBO=2). In the vitreous state reached by quenching melted minerals, the SOT remain nearly undistorted (Si-O bond length unchanged); the Si-O-Si angles at the bridging oxygens of pyroxenes, however, scatter statistically. Therefore, the original cation oxygen symmetry of the crystal (octahedral and hexahedral coordination by O) is completely lost. The blended bands at 10 and 18 microns lose their diagnostic differences and become broad and structureless. This illustrates best the basic problem of interstellar silicate mineral diagnostics. Optical data of glasses of enstatite, bronzite, hypersthene, diopside, salite, and hedenbergite have been derived. Results of enstatite (E), bronzite (B), and hypersthene (H) show very good agreement with the observed silicate features in the IR spectra of evolutionarily young objects that show P-type silicate signature according to the classification by Gurtler and Henning (1986). Compositional parameters and main characteristics of experimental SSG spectra in IR for the glasses E, B, and H are shown in tabular form. Results fit excellently the relations derived by Koike and Hasegawa (1987) and suggest that the band ratio of the astronomical silicate by Draine and Lee (1984) is too low.

  12. In Situ SAXS/WAXS of Zeolite Microwave Synthesis: NaY, NaA, and Beta Zeolites

    SciTech Connect

    Panzarella,B.; Tompsett, G.; Conner, W.; Jones, K.

    2007-01-01

    A custom waveguide apparatus is constructed to study the microwave synthesis of zeolites by in situ small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). The WR-284 waveguide is used to heat precursor solutions using microwaves at a frequency of 2.45 GHz. The reaction vessels are designed to include sections of thin-walled glass, which permit X-rays to pass through the precursor solutions with minimal attenuation. Slots were machined into the waveguide to provide windows for X-ray energy to enter and scatter from solutions during microwave heating. The synthesis of zeolites with conventional heating is also studied using X-ray scattering in the same reactor. SAXS studies show that the crystallization of beta zeolite and NaY zeolite is preceded by a reorganization of nanosized particles in their precursor solutions or gels. The evolution of these particles during the nucleation and crystallization stages of zeolite formation depends on the properties of the precursor solution. The synthesis of NaA and NaX zeolites and sodalite from a single zeolite precursor is studied by microwave and conventional heating. Microwave heating shifts the selectivity of this synthesis in favor of NaA and NaX over sodalite; conventional heating leads to the formation of sodalite for synthesis from the same precursor. The use of microwave heating also led to a more rapid onset of NaA zeolite product crystallization compared to conventional heating. Pulsed and continuous microwave heating are compared for zeolite synthesis. The resulting rates of formation of the zeolite products, and the relative amounts of the products determined from the WAXS spectra, are similar when either pulsed or continuous microwave heating is applied in the reactor while maintaining the same synthesis temperature. The consequences of these results in terms of zeolite synthesis are discussed.

  13. Characterization and antibacterial activity of silver exchanged regenerated NaY zeolite from surfactant-modified NaY zeolite.

    PubMed

    Salim, Mashitah Mad; Malek, Nik Ahmad Nizam Nik

    2016-02-01

    The antibacterial activity of regenerated NaY zeolite (thermal treatment from cetyltrimethyl ammonium bromide (CTAB)-modified NaY zeolite and pretreatment with Na ions) loaded with silver ions were examined using the broth dilution minimum inhibitory concentration (MIC) method against Escherichia coli (E. coli ATCC 11229) and Staphylococcus aureus (S. aureus ATCC 6538). X-ray diffraction (XRD), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) and chemical elemental analyses were used to characterize the regenerated NaY and AgY zeolites. The XRD patterns indicated that the calcination and addition of silver ions on regenerated NaY zeolite did not affect the structure of the regenerated NaY zeolite as the characteristic peaks of the NaY zeolite were retained, and no new peaks were observed. The regenerated AgY zeolite showed good antibacterial activity against both bacteria strains in distilled water, and the antibacterial activity of the samples increased with increasing Ag loaded on the regenerated AgY zeolite; the regenerated AgY zeolite was more effective against E. coli than S. aureus. However, the antibacterial activity of the regenerated AgY was not effective in saline solution for both bacteria. The study showed that CTAB-modified NaY zeolite materials could be regenerated to NaY zeolite using thermal treatment (550°C, 5h) and this material has excellent performance as an antibacterial agent after silver ions loading. PMID:26652350

  14. Crewmember working on the mid deck Zeolite Crystal Growth experiment.

    NASA Technical Reports Server (NTRS)

    1992-01-01

    View showing Payload Specialist Bonnie Dunbar, in the mid deck, conducting the Zeolite Crystal Growth (ZCG) Experiment in the mid deck stowage locker work area. View shows assembly of zeolite sample in the metal autoclave cylinders prior to insertion into the furnace.

  15. FUNDAMENTALS AND APPLICATIONS OF PERVAPORATION THROUGH ZEOLITE MEMBRANES

    EPA Science Inventory

    Zeolite membranes are well suited for separating liquid-phase mixtures by pervaporation because of their molecular-sized pores and their hydrophilic/hydrophobic nature, and the first commercial application of zeolite membranes has been for dehydrating organics [1]. Because of ...

  16. Ion exchange in a zeolite-molten chloride system

    SciTech Connect

    Woodman, R.H.; Pereira, C.

    1997-07-01

    Electrometallurgical treatment of spent nuclear fuel results in a secondary waste stream of radioactive fission products dissolved in chloride salt. Disposal plans include a waste form that can incorporate chloride forms featuring one or more zeolites consolidated with sintered glass. A candidate method for incorporating fission products in the zeolites is passing the contaminated salt over a zeolite column for ion exchange. To date, the molten chloride ion-exchange properties of four zeolites have been investigated for this process: zeolite A, IE95{reg_sign}, clinoptilolite, and mordenite. Of these, zeolite A has been the most promising. Treating zeolite 4A, the sodium form of zeolite A , with the solvent salt for the waste stream-lithium-potassium chloride of eutectic melting composition, is expected to provide a material with favorable ion-exchange properties for the treatment of the waste salt. The authors constructed a pilot-plant system for the ion-exchange column. Initial results indicate that there is a direct relationship between the two operating variable of interest, temperature, and initial sodium concentration. Also, the mass ratio has been about 3--5 to bring the sodium concentration of the effluent below 1 mol%.

  17. Zeolitization of tuffaceous rocks of the green river formation, wyoming.

    PubMed

    Goodwin, J H; Surdam, R C

    1967-07-21

    The alkali-rich zeolites mordenite and clinoptilolite have been discovered in tuffaceous rocks of the Green River Formation, Wyoming. This occurrence strongly supports the alteration of glass to alkali-rich zeolite to analcime as the paragenetic sequence of alteration of tuffaceous rocks deposited in ancient Lake Gosiute. PMID:17734226

  18. Selective thermal oxidation of hydrocarbons in zeolites by oxygen

    DOEpatents

    Frei, Heinz; Blatter, Fritz; Sun, Hai

    2000-01-01

    A process for selective thermal oxidation of hydrocarbons adsorbed onto zeolite matrices. A highly selective thermal oxidation of unsubstituted or alkyl substituted alkanes, alkenes, aromatics and cycloalkyls is carried out in solvent free zeolites under dark thermal conditions. The process oxidizes hydrocarbons almost completely selectively without substantial production of byproducts.

  19. Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen

    DOEpatents

    Frei, H.; Blatter, F.; Sun, H.

    1999-06-22

    A process is described for selective thermal oxidation or photooxidation of hydrocarbons adsorbed onto zeolite matrices. A highly selective thermal oxidation and photooxidation of unsubstituted or alkyl substituted alkanes, alkenes, aromatics and cycloalkyls in solvent free zeolites under dark thermal conditions or under irradiation with visible light. The process oxidizes hydrocarbons almost completely selectively without substantial production of byproducts. 19 figs.

  20. Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen

    DOEpatents

    Frei, Heinz; Blatter, Fritz; Sun, Hai

    1999-01-01

    A process for selective thermal oxidation or photooxidation of hydrocarbons adsorbed onto zeolite matrices. A highly selective thermal oxidation and photooxidation of unsubstituted or alkyl substituted alkanes, alkenes, aromatics and cycloalkyls in solvent free zeolites under dark thermal conditions or under irradiation with visible light. The process oxidizes hydrocarbons almost completely selectively without substantial production of byproducts.

  1. Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen

    DOEpatents

    Frei, Heinz; Blatter, Fritz; Sun, Hai

    2001-01-01

    A process for a combined selective thermal oxidation and photooxidation of hydrocarbons adsorbed onto zeolite matrices. A highly combined selective thermal oxidation and photooxidation of unsubstituted or alkyl substituted alkanes, alkenes, aromatics and cycloalkyls in solvent free zeolites under dark thermal conditions or under irradiation with visible light. The process oxidizes hydrocarbons almost completely selectively without substantial production of byproducts.

  2. CATION CONTROLLED SINGLET OXYGEN MEDIATED OXIDATION OF OLEFINS WITHIN ZEOLITES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Oxidation of trialkyl olefins has been performed within zeolites employing thionin as the singlet oxygen sensitizer. Unusual selectivity in favor of secondary hydroperoxides is observed within zeolites. In light of the fact that in solution such a selectivity is never observed the selectivity report...

  3. Zeolites in the Pine Ridge Indian Reservation, South Dakota

    USGS Publications Warehouse

    Raymond, William H.; Bush, Alfred L.; Gude, Arthur J., 3rd

    1982-01-01

    Zeolites of possible commercial value occur in the Brule Formation of Oligocene age and the Sharps Formation (Harksen, 1961) of Miocene age which crop out in a wide area in the northern part of the Pine Ridge Indian Reservation. The thickness of the zeolite-bearing Interval and the extent of areas within the Interval which contain significant amounts of zeolites are far greater than was expected prior to this investigation. The shape of the zeolite-bearing Interval is tabular and the dimensions of Its exposure are roughly 10 ml x 200 mi x 150 ft (16 km x 160 km x 45 m) thick. Within the study area, there are tracts in which the zeolite resource potential is significant (see pl. 2). This report is intended to inform the Oglala Sioux Tribe of some of the most promising zeolite occurrences. Initial steps can then be taken by the Tribe toward possible development of the resources, should they wish to do so. The data contained herein identify areas of high zeolite potential, but are not adequate to establish economic value for the deposits. If development is recommended by the tribal government, we suggest that the tribal government contact companies involved in research and production of natural zeolites and provide them with the data in this report.

  4. The development of electrical treeing in LDPE and its nanocomposites with spherical silica and fibrous and laminar silicates

    NASA Astrophysics Data System (ADS)

    Tiemblo, Pilar; Hoyos, Mario; Gómez-Elvira, Jose Manuel; Guzmán, Julio; García, Nuria; Dardano, Andrea; Guastavino, Francesco

    2008-06-01

    Electrical treeing in LDPE and three LDPE nanocomposites, with spherical silica and fibrous and laminar phyllosilicates, has been studied. Electrical tests were performed at a 50 Hz frequency and voltages between 8 and 29 kV, and the time to inception of the first electrical partial discharges (TTI) of the electrical trees and the time to breakdown (TBD), related to the electrical stability of the insulator, were determined. Above 15 kV all the nanocomposites show longer inception times and shorter tree growth times than LDPE. It is proposed that both observations are caused by the modification of the polymer crystalline morphology induced by the presence of the fillers and by the development of a large number of interfacial structures, both organo-inorganic and amorphous-crystalline. Below 15 kV the TBD is increased in the nanocomposites with the laminar silicate because of tortuosity and the TTI is increased in the fibrous silicate containing a nanocomposite because of the LDPE crystalline morphology in the presence of the silicate. The nanosilica particles decrease the electrical stability in the whole voltage range by decreasing both TTI and TBD.

  5. Compositional effects on Si–OH bond length in hydrous silicates with implications for trends in the SiOH acidity

    SciTech Connect

    Zarubin, Dmitri P.

    2014-04-01

    Theoretical calculations of the structure and Brønsted acidity of SiOH groups in silica clusters have never addressed the question if these vary with the degree of SiOH deprotonation. In this connection, a statistical analysis is presented of Si–OH bond lengths in crystalline hydrogen silicates with well-determined structures with a special emphasis placed on effects of the silicate composition. It is found that among hydrogen silicates of large cations with low charges the Si–OH bonds are always longer than terminal Si–O bonds in the same anion and correlate in length with the anionic charge per tetrahedron. The findings are explained by steric limitations on charge balancing at oxygen atoms by hydrogen bonds and/or cations. It is suggested that similar limitations and imbalances may underlie the well-known trends in the Brønsted acidity of silicic acids and silicas in aqueous media: decreased acidity with increased SiOH deprotonation and increased acidity with increased tetrahedra connectivity. - Graphical abstract: Si–OH bonds in crystalline silicates lengthen with the anionic charge per tetrahedron, which is in parallel with the well-known trend of decreased acidity of silicic acids and silicas in solution with increased degree of deprotonation. - Highlights: • Si–OH bonds in alkali hydrogen silicates are always longer than terminal Si–O bonds. • Si–OH bonds in silicates lengthen with the anionic charge per tetrahedron. • The Si–OH bond elongation results from inherent underbonding of terminal O atoms. • The longer the Si–OH bond, the less acidic the OH group is.

  6. Applications of two-dimensional solid state nuclear magnetic resonance in silicates

    NASA Astrophysics Data System (ADS)

    Xu, Zhi

    1998-10-01

    Nuclear magnetic resonance (NMR) is a powerful technique and has been routinely applied in many fields. In this study, we have used high resolution two-dimensional (2D) solid state NMR techniques to study the dynamic process of Li diffusion, the kinetic process of oxygen isotope exchange, and the structural characterization of hydrous and anhydrous silicate glasses at atomic level. In the Li diffusion study, we first established the correlation between the sp6Li chemical shifts and the lithium coordination environments in lithium containing silicates. Then, we assigned the sp6Li magic angle spinning (MAS) spectrum and applied 1D, 2D variable temperature exchange NMR to observe Lisp+ diffusion in lithium orthosilicate. For the first time, our result revealed a detailed picture of the hopping rates of Lisp+ ions among structurally distinct sites and helped to define the diffusion pathway. We have shown that Lisp+ ions hopping rates and activation energies depend on site geometry. NMR measurements on Li ionic hopping frequencies was used to accurately predict the bulk conductivity. In the site-specific oxygen isotope exchange study, we first developed a method to obtain quantitative sp{17}O NMR spectra. Then, we applied the method to stilbite, a natural zeolite. We have shown for the first time that framework oxygens in Al-O-Si sites react faster with oxygens in the channel water than oxygens in Si-O-Si sites. Such an observation has partially proved the quantum ab initio calculation on water adsorption onto silicates. Our measured kinetics results agreed well with bulk isotopic measurements. Water dissolution mechanism in silicates glasses, especially aluminosilicate glasses, has been a long-standing controversy. We have used the sp{17}O spectra for hydrous and anhydrous sodium tetrasilicate glasses and albite glasses to study the structural role of hydrogen-containing species. For the first time, we have observed the oxygen peak for SiOH in hydrous sodium tetrasilicate glass. Such a component might also be present in hydrous albite glasses. We also detected the oxygen signal for molecular Hsb2O in all the hydrous silicate and aluminosilicate glasses. Our results tend to support one of the water dissolution models.

  7. Antimony and silicon environments in antimony silicate glasses

    SciTech Connect

    Mee, M.; Davies, B.C.; Orman, R.G.; Thomas, M.F.; Holland, D.

    2010-09-15

    Antimony silicate glasses, of general formula xSb{sub 2}O{sub 3}.(1-x)SiO{sub 2} (0.1{<=}x{<=}0.78), have been prepared by melt-quenching and their structures studied using {sup 29}Si MAS NMR spectroscopy, {sup 121}Sb Moessbauer spectroscopy and Raman spectroscopy. Oxidation during melting gives rise to Sb{sup 5+} in concentrations, which increase linearly with x to give a value of {approx}10% when x=0.78. {sup 121}Sb Moessbauer spectra show Moessbauer shifts and quadrupole splittings consistent with Sb{sup 3+} in a [:SbO{sub 3}] trigonal pyramid, similar to that in crystalline Sb{sub 2}O{sub 3}. A broad band in the Raman spectrum at {approx}410 cm{sup -1} is due to the vibrations of such a unit. The dependence of the silicon Q{sup n} speciation on x can be interpreted by the formation of Sb-O-Sb links possibly to form rings of 4 [:SbO{sub 3}] units such as are found in valentinite. - Graphical abstract: Antimony silicate glasses have been shown to contain Sb{sup 3+} in [:SbO{sub 3}] trigonal pyramid units using {sup 121}Sb Moessbauer spectroscopy and Raman spectroscopy. {sup 29}Si magic-angle-spinning NMR has shown silicon Q{sup n} speciation which can be interpreted as formation of rings of 4 [:SbO{sub 3}] units such as are found in valentinite.

  8. Luminescent properties of Er and Si co-implanted silicates

    NASA Astrophysics Data System (ADS)

    Pellegrino, P.; Garrido, B.; Lebour, Y.; Moreno, J. A.; Garcia, C.; Morante, J. R.; Bettotti, P.; Pavesi, L.; Prassas, M.

    2005-02-01

    An extensive research for optical active materials at 1540 nm is currently being carried out, on the steam of the strong need for optoelectronic devices which can be integrated with the mainstream Si technology. The formation of silica films doped with Er and Si clusters has been shown as one of the promising approaches. We explored the emission properties of different silicate glasses co-implanted with silicon and Er ions to various doses. As starting materials we used soda-lime and aluminium silicates, glasses which show a larger optical bandwidth than silica at 1540 nm. A Si multi-implantation scheme has been adopted for a planar profile. The best conditions to precipitate Si and activate the Er atoms have been investigated. Optimal annealing temperatures have been found around 500 C, depending on the particular composition of the original glass substrate. The structural analysis of the resulting structures ensures that the best emission properties are the ones for which a phase separation between the implanted Si and the matrix occurs, even without the formation of crystalline aggregates. A comprehensive study of the emission properties is given as a function of the matrix characteristics, Si and Er content, excitation wavelength and power density. It is shown an increase of the emission enhancement of the Er atoms due to the presence of Si cluster when increasing the excitation power. Modelling of the interaction between the absorbing Si nanoprecipitates and the emitting Er atoms has been carried out, in order to estimate the relevant physical parameters which describe the PL process.

  9. Some observations on the synthesis of fully-dispersible nanocrystalline zeolite ZSM-5.

    PubMed

    Selvin, Rosilda; Chiang, Anthony S T

    2014-09-01

    A facile method for the rapid synthesis of fully-dispersible ZSM-5 (Si/Al = 100) of about 30 nm size in high yield (about 91%) is described. The method comprises three steps, viz., concentration of an initial clear solution, low-temperature (80 degrees C) ageing of concentrated sol, and high-temperature (175 degrees C) hydrothermal treatment or microwave heating (175 degrees C) of aged concentrated sol. A simple vacuum-concentration method was used for the extraction of pure NPs of ZSM-5 in solution. XRD, FT-IR, TGA and ASAP characterizations showed that the NPs were partially crystalline. The concentration step accelerated the aggregation of primary units, which helps in the production of a large number of nucleation centers protected by TPA+ ions against aggregation. During low-temperature ageing, the number of critical sized nuclei increases, growing into zeolite. The high-temperature heating results in the complete growth of unreacted silica, giving high yields. A key factor for generating small non-aggregated zeolite crystals is the amount of water in the synthesis sol. The three-step method presented here produces a target material of small and uniform sized, non-aggregated ZSM-5 of about 30 nm in a short reaction time. The results are significant, as the synthesis method adopted here produces much uniform, non-aggregated nanocrystalline ZSM-5 in a shorter time with high yield. PMID:25924414

  10. Monoethanol amine modified zeolite 13X for CO{sub 2} adsorption at different temperatures

    SciTech Connect

    P.D. Jadhav; R.V. Chatti; R.B. Biniwale; N.K. Labhsetwar; S. Devotta; S.S. Rayalu . s_rayalu@neeri.res.in

    2007-12-15

    Zeolite 13X has been modified with monoethanol amine (MEA). MEA loadings of 0.5-25 wt % have been achieved using the impregnation method in different solvents. The mode of incorporation based on methanol with stirring at room temperature appears to be the most feasible. The adsorbent has been characterized for crystallinity, surface area, pore volume, and pore size. The thermal stability of the adsorbent is studied using a thermal analyzer. The CO{sub 2} adsorption capacity of adsorbents is evaluated using the breakthrough adsorption method with a packed column on a 10 g scale. The adsorption capacities of adsorbents are estimated in the temperature range 30-120{sup o}C. The adsorbents show improvement in CO{sub 2} adsorption capacity over the unmodified zeolite by a factor of ca. 1.6 at 30{sup o}C, whereas at 120{sup o}C the efficiency improved by a factor of 3.5. For adsorption at these temperatures, different MEA loading levels were found to be suitable as per the governing adsorption phenomena, that is, physical or chemical. The adsorbent is also studied for CO{sub 2} selectivity over N{sub 2} at 75{sup o}C. The MEA-modified adsorbent shows better CO{sub 2} selectivity, which was improved further in the presence of moisture. 25 refs., 6 figs., 3t abs.

  11. Computational characterization of zeolite porous networks: an automated approach.

    PubMed

    First, Eric L; Gounaris, Chrysanthos E; Wei, James; Floudas, Christodoulos A

    2011-10-14

    An automated method has been developed to fully characterize the three-dimensional structure of zeolite porous networks. The proposed optimization-based approach starts with the crystallographic coordinates of a structure and identifies all portals, channels, and cages in a unit cell, as well as their connectivity. We apply our algorithms to known zeolites, hypothetical zeolites, and zeolite-like structures and use the characterizations to calculate important quantities such as pore size distribution, accessible volume, surface area, and largest cavity and pore limiting diameters. We aggregate this data over many framework types to gain insights about zeolite selectivity. Finally, we develop a continuous-time Markov chain model to estimate the probability of occupancy of adsorption sites throughout the porous network. ZEOMICS, an online database of structure characterizations and web tool for the automated approach is freely available to the scientific community (http://helios.princeton.edu/zeomics/). PMID:21881655

  12. Modified zeolite-based catalyst for effective extinction hydrocracking

    SciTech Connect

    Yan, T.Y. )

    1989-10-01

    The shape selectivity of zeolites makes them generally ineffective for extinction hydrocracking of polycyclic aromatic feeds. To overcome this problem, the zeolite can be modified with an amorphous cracking component to form a composite catalyst. This composite catalyst will be effective for extinction hydrocracking and retain the superior performance characteristics of a zeolite catalyst at the same time because the zeolite and the amorphous components of the catalyst operate complementarily. To illustrate this principle, NiW/REX-NiW/SiO/sub 2/Al/sub 2/O/sub 3/ composite catalyst was tested in the pilot plant. It was active, low in aging rate, resistant to nitrogen poisoning and high in selectivities for naphthas. The aged catalyst could be oxidatively regenerated to fully recover the activity and the product selectivities. This composite catalyst was superior to both individual (zeolite and amorphous) components for extinction hydrocracking. Catalysts similar to this have been used commercially for many years.

  13. Rheological Influence of Synthetic Zeolite on Cement Pastes

    NASA Astrophysics Data System (ADS)

    Baldino, N.; Gabriele, D.; Frontera, P.; Crea, F.; de Cindio, B.

    2008-07-01

    Self Compacting Concrete (SCC) is characterized by specific and particular mechanical properties, often due to the addition of components, able to modify the paste rheology. Concrete properties are strongly affected by characteristics of the fresh cement paste that is the continuous phase dispersing larger aggregates. Therefore, aiming to characterize mechanical properties of final concrete is relevant to know rheological properties of the base cement paste. In this work cement pastes for SCC were prepared by using, as additive, synthetic zeolite 5A in different amounts and they were analyzed by small amplitude oscillations. Experimental results have shown a relationship between dynamic moduli and zeolite content, identifying a proper level of zeolite addition. Moreover samples containing traditional fine additives, such as silica fume and limestone, were prepared and experimental data were compared to those obtained by using zeolite. It was found that zeolite seems to give better properties to cement paste than other additives can do.

  14. Preparation of a Versatile Bifunctional Zeolite for Targeted Imaging Applications

    PubMed Central

    Ndiege, Nicholas; Raidoo, Renugan; Schultz, Michael K.; Larsen, Sarah

    2011-01-01

    Bifunctional zeolite Y was prepared for use in targeted in vivo molecular imaging applications. The strategy involved functionalization of the external surface of zeolite Y with chloropropyltriethoxysilane followed by reaction with sodium azide to form azide-functionalized NaY, which is amenable to copper(1) catalyzed click chemistry. In this study, a model alkyne (4-pentyn-1-ol) was attached to the azide-terminated surface via click chemistry to demonstrate feasibility for attachment of molecular targeting vectors (e.g., peptides, aptamers) to the zeolite surface. The modified particle efficiently incorporates the imaging radioisotope gallium-68 (68Ga) into the pores of the azide-functionalized NaY zeolite to form a stable bifunctional molecular targeting vector. The result is a versatile clickable zeolite platform that can be tailored for future in vivo molecular targeting and imaging modalities. PMID:21306141

  15. Design of composite photocatalyst of TiO2 and Y-zeolite for degradation of 2-propanol in the gas phase under UV and visible light irradiation.

    PubMed

    Kamegawa, Takashi; Ishiguro, Yasushi; Kido, Ryota; Yamashita, Hiromi

    2014-01-01

    Hydrophobic Y-zeolite (SiO2/Al2O3 = 810) and TiO2 composite photocatalysts were designed by using two different types of TiO2 precursors, i.e., titanium ammonium oxalate and ammonium hexafluorotitanate. The porous structure, surface property and state of TiO2 were investigated by various characterization techniques. By using an ammonium hexafluorotitanate as a precursor, hydrophobic modification of the Y-zeolite surface and realizing visible light sensitivity was successfully achieved at the same time after calcination at 773 K in the air. The prepared sample still maintained the porous structure of Y-zeolite and a large surface area. Highly crystalline anatase TiO2 was also formed on the Y-zeolite surface by the role of fluorine in the precursor. The usages of ammonium hexafluorotitanate were effective for the improvement of the photocatalytic performance of the composite in the degradation of 2-propanol in the gas phase under UV and visible light (? > 420 nm) irradiation. PMID:25314607

  16. Raman spectroscopic studies of zeolite framework. Hydrated Zeolite A and the influence of cations

    SciTech Connect

    Dutta, P.K.; Del Barco, B.

    1985-05-09

    Raman spectra of hydrated zeolite A completely exchanged with Li/sup +/, Na/sup +/, K/sup +/, Tl/sup +/, and NH/sub 4//sup +/ ions are reported in this paper. The emphasis has been on the high-frequency region between 300 and 1200 cm/sup -1/, where the intramolecular modes of the aluminosilicate framework are expected. The Raman bands cluster in three regions of the spectrum: (a) 300-500 cm/sup -1/, assigned to T-O deformation modes; (b) 650-750 cm/sup -1/, assigned to Al-O stretching vibrations; and (c) 900-1100 cm/sup -1/, assigned to Si-O stretching motions. The Raman spectra of the ion-exchanged zeolites suggest that Li/sup +/ distorts the zeolite framework, whereas in Na/sup +/-, K/sup +/-, and Tl/sup +/-A, the zeolite structure remains unchanged. In NH/sub 4/-A, there is strong spectroscopic evidence for H-bond formation between the cation and the lattice oxygens. 31 references, 2 figures, 1 table.

  17. Influence of NaA Zeolite Crystal Expansion/Contraction on Zeolite Membrane Separations

    SciTech Connect

    Sorenson, Stephanie G; Payzant, E Andrew; Gibbons, Will T; Soydas, Belma; Kita, Hidetoshi; Noble, Richard D; Falconer, John L.

    2011-01-01

    In-situ powder XRD measurements showed that the NaA zeolite unit cell contracts and expands upon adsorption, and these changes in zeolite crystal size correlate with permeation changes through NaA zeolite membranes. These membranes had high pervaporation selectivities, even though gas permeation was mainly through defects, as indicated by Knudsen selectivities for gases. At 300 K and a thermodynamic activity of 0.03, water contracted the NaA crystals by 0.22 vol%, and this contraction increased the helium flux through two NaA membranes by approximately 80%. Crystal contraction also increased the fluxes of i-butane during vapor permeation and i-propanol (IPA) during pervaporation (~ 0.03 wt% water). At activities above 0.07, water expanded NaA crystals and correspondingly decreased the membrane fluxes of helium, i-butane, and IPA. Similarly, methanol contracted NaA crystals by 0.05 vol% at an activity of 0.02, and this contraction slightly increased the helium and i-butane fluxes through a NaA membrane. Above an activity of 0.06, methanol expanded the crystals, and the fluxes of helium and i-butane through a NaA membrane decreased. The adsorbate-induced changes explain some pervaporation behavior reported by others, and they indicate that crystal expansion and contraction may increase or decrease zeolite NaA membrane selectivity by changing the defect sizes.

  18. Mid-Infrared Spectrum of the Zodiacal Emission: Detection of Crystalline Silicates in Interplanetary Dust

    NASA Technical Reports Server (NTRS)

    Ootsubo, T.; Onaka, T.; Yamamura, I.; Ishihara, D.; Tanabe, T.; Roellig, T. L.

    2003-01-01

    Within a few astronomical units of the Sun the solar system is filled with interplanetary dust, which is believed to be dust of cometary and asteroidal origin. Spectroscopic observations of the zodiacal emission with moderate resolution provide key information on the composition and size distribution of the dust in the interplanetary space. They can be compared directly to laboratory measurements of candidate materials, meteorites, and dust particles collected in the stratosphere. Recently mid-infrared spectroscopic observations of the zodiacal emission have been made by two instruments on board the Infrared Space Observatory; the camera (ISOCAM) and the spectrophotometer (ISOPHOT-S). A broad excess emission feature in the 9-11 micron range is reported in the ISOCAM spectrum, whereas the ISOPHOT-S spectra in 6-12 microns can be well fitted by a blackbody radiation without spectral features.

  19. Topological Crystalline Insulators

    NASA Astrophysics Data System (ADS)

    Hsieh, Timothy

    2015-03-01

    Topological crystalline insulators (TCI) are new phases of matter in which nontrivial band topology and crystal symmetry unite to protect metallic states on the boundary. Remarkably, TCIs have been predicted and observed in the conveniently simple rocksalt SnTe class of IV-VI semiconductors. Despite the simple crystal structure, the interplay between topology and crystal symmetry in these materials have led to a rich variety of new phenomena, including the coexistence of massless and massive Dirac fermions arising from ferroelectric distortion and strain-induced flat band superconductivity. These new physical mechanisms are not only of intrinsic interest but may also find application in new transistor devices. After discussing the topological nature and potential uses of IV-VI family TCIs, I will present recent predictions of TCIs in several anti-perovskite materials. The origin of TCI in this new class of materials is strikingly different and involves the band inversion of two J = 3/2 quartets of Dirac fermions, which together form a ``Dirac octet.'' As interactions play a significant role in many anti-perovskites, this prediction serves as first step toward realizing TCIs in strongly correlated systems. This work is supported by NSF Graduate Research Fellowship No. 0645960 and DOE Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-SC0010526.

  20. Mineralogy Of Silicate Dust Particles For Comet 17P/Holmes By Subaru/COMICS

    NASA Astrophysics Data System (ADS)

    Yamaguchi, M.; Ootsubo, T.; Watanabe, J.; Honda, M.; Sakon, I.; Ishiguro, M.; Sarugaku, Y.; Kobayashi, H.; Kawakita, H.

    2011-10-01

    Dust grains and icy materials in comets have been used to investigate the formation conditions of the solar system. It is considered that the existence of crystalline silicate in comets indicates the radial mixing of materials in the early solar nebula. The outburst of comet 17P/Holmes showed on late October, 2007. We carried out low-dispersion spectroscopic observations of 17P/Holmes in midinfrared region with Subaru/COMICS. We show results of our model fitting analysis by using a thermal emission model for this comet. We discuss about the mineral composition for dust grains of 17P/Holmes.