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1

Catalytic pyrolysis using UZM-44 aluminosilicate zeolite  

DOEpatents

A new family of aluminosilicate zeolites designated UZM-44 has been synthesized. These zeolites are represented by the empirical formula Na.sub.nM.sub.m.sup.k+T.sub.tAl.sub.1-xE.sub.xSi.sub.yO.sub.z where "n" is the mole ratio of Na to (Al+E), M represents a metal or metals from zinc, Group 1, Group 2, Group 3 and or the lanthanide series of the periodic table, "m" is the mole ratio of M to (Al+E), "k" is the average charge of the metal or metals M, T is the organic structure directing agent or agents, and E is a framework element such as gallium. The process involves contacting a carbonaceous biomass feedstock with UZM-44 at pyrolysis conditions to produce pyrolysis gases comprising hydrocarbons. The catalyst catalyzes a deoxygenation reaction converting oxygenated hydrocarbons into hydrocarbons and removing the oxygen as carbon oxides and water. A portion of the pyrolysis gases is condensed to produce low oxygen biomass-derived pyrolysis oil.

Nicholas, Christopher P; Boldingh, Edwin P

2013-12-17

2

Catalytic pyrolysis using UZM-39 aluminosilicate zeolite  

DOEpatents

A new family of coherently grown composites of TUN and IMF zeotypes has been synthesized and show to be effective catalysts for catalytic pyrolysis of biomass. These zeolites are represented by the empirical formula. Na.sub.nM.sub.m.sup.n+R.sub.rQ.sub.qAl.sub1-xE.sub.xSi.sub.yO.s- ub.z where M represents zinc or a metal or metals from Group 1, Group 2, Group 3 or the lanthanide series of the periodic table, R is an A,.OMEGA.-dihalosubstituted paraffin such as 1,4-dibromobutane, Q is a neutral amine containing 5 or fewer carbon atoms such as 1-methylpyrrolidine and E is a framework element such as gallium. The process involves contacting a carbonaceous biomass feedstock with UZM-39 at pyrolysis conditions to produce pyrolysis gases comprising hydrocarbons. The catalyst catalyzes a deoxygenation reaction converting oxygenated hyrdocarbons into hydrocarbons removing the oxygen as carbon oxides and water. A portion of the pyrolysis gases is condensed to produce low oxygen biomass-derived pyrolysis oil.

Nicholas, Christpher P; Boldingh, Edwin P

2013-12-17

3

Novel process for the preparation of ZSM-5 aluminosilicate zeolite  

SciTech Connect

A method of manufacture of ZSM-5 aluminosilicate zeolite is described which consists of crystallizing, at a temperature of from about 185/sup 0/C to about 250/sup 0/C, an aqueous crystallizing gel consisting essentially of a colloidal silica, a colloidal alumina, water, trisodium phosphate and potassium fluoride. Water is present in a range of from about 200 to about 500 moles of water per mole of colloidal alumina, wherein the colloidal silica and the colloidal alumina are present in a molar ratio of greater than about 20 moles of the colloidal silica per mole of the colloidal alumina and less than 50 moles of the colloidal silica per mole of the colloidal alumina. Trisodium phosphate is present in a mole ratio of 1.8 to 2.7 moles of the trisodium phosphate per mole of the colloidal alumina and wherein the potassium fluoride is present in a molar relationship of greater than 0.5 to less than 2.1 moles of potassium fluoride per mole of colloidal alumina.

Winquist, B.H.C.

1989-04-04

4

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

PubMed

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

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

2006-09-01

5

Zeolites  

NASA Technical Reports Server (NTRS)

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

1992-01-01

6

Synthesis of highly stable mesoporous aluminosilicates from commercially available zeolites and their application to the pyrolysis of woody biomass  

Microsoft Academic Search

Ordered mesoporous aluminosilicates have been successfully obtained via the simple combination of topdown and bottomup approaches, using commercially available zeolites as the framework sources. The mesoporous aluminosilicates are characterized by XRD, N2 sorption, SEM, TEM, ICP, and NMR, and have proven to have controllable aluminium contents, well-developed mesoporosity, and excellent hydrothermal stability. The hydrothermally stable mesoporous aluminosilicates, which possess the

Hyung Ik Lee; Hyun Ju Park; Young-Kwon Park; Jae Young Hur; Jong-Ki Jeon; Ji Man Kim

2008-01-01

7

Zealous zeolites  

Microsoft Academic Search

Zeolites have made significant inroads in fluid cracking catalysts for gasoline and have pushed phosphates out of laundry detergents. But these crystalline aluminosilicate structures are just beginning to make their mark in chemical processes and environmental applications. Ideally suited for work as molecular sieves and catalysts, zeolites sport uniform surface pores and channels that are receptive only to molecules of

1996-01-01

8

Radical formation in the adsorption of trimethylbenzenes on crystalline and amorphous aluminosilicates  

SciTech Connect

The formation and conversion of cation radicals (CR) in the absorption of the isomers of trimethylbenzene (TMB), pseudocumene and mesitylene on Y zeolites, a high-silica wide-pore mordenite, the UHS zeolite TsVM, which belong to the class of pentasils, and on an amorphous aluminosilicate (AS) have been studied by EPR. It is shown that the formation of CR takes place in the adsorption of TMB on dehydrated specimens of the H-forms of the zeolites and amorphous AS in the presence of O/sub 2/. The possible structure of the CR formed, the paths for their conversion, as well as the structure of the radical-forming center are discussed. A mechanism is suggested for the formation and conversion of CR at an oxidizing-reducing center activated by oxygen. The radical processes which take place on the zeolites and amorphous AS are associated with the selectivity of the catalytic reactions involving the participation of TMB and also with the deactivation of the catalysts.

Surin, S.A.; Fedorova, L.A.; Gullyev, C.; Chukin, G.D.; Nefedov, B.K.; Radchenko, E.D.

1987-04-01

9

Mesoporous aluminosilicates assembled from dissolved LTA zeolite and triblock copolymer in the presence of tetramethylammonium hydroxide.  

PubMed

Zeolite Na-A crystals dissolved in a HCl solution were used as a single-source of silicon and aluminum for the synthesis of mesoporous aluminosilicates via a template-assisted method with an organic base tetramethylammonium hydroxide (TMAOH). Amphiphilic triblock copolymer Pluronic F127 (EO(106)PO(70)EO(106)) was used as template. Increasing the amount of TMAOH in the synthetic solution resulted in an increase in the aluminum content of the products. On the other hand, mesostructural periodicity was deteriorated with higher content of aluminum incorporated into the mesoporous framework. The samples with low Si/Al ratios less than 5 have wormhole-like pore structure, while the samples with Si/Al ratios more than 7 possess highly ordered mesoporous structure, a body-centered Im3m symmetry, with single crystal like morphology. The samples with Si/Al ratio of 7, which prepared at TMAOH molar concentration of 25 mM in the templating solution, possess BET surface area of 470 m(2)/g, pore size of 6.4 nm, and pore volume of 0.56 cm(3)/g. Aluminum atoms have successfully been incorporated in a tetra-coordinated position and remained stable even after calcination at 600 degrees C. PMID:19223041

Tanaka, Shunsuke; Okada, Hiroaki; Nakatani, Norihito; Maruo, Takanori; Nishiyama, Norikazu; Miyake, Yoshikazu

2009-05-15

10

A new aluminosilicate molecular sieve with a system of pores between those of ZSM-5 and beta zeolite.  

PubMed

A new aluminosilicate zeolite (ITQ-39) has been synthesized. This is an extensively faulted structure with very small domains that makes the structure elucidation very difficult. However, a combination of adsorption spectroscopy and reactivity studies with selected probe molecules suggests that the pore structure of ITQ-39 is related to that of Beta zeolite, with a three-directional channel system with large pores (12-MR), but with an effective pore diameter between those of Beta and ZSM-5, or a three-directional channel system with interconnected large (12-MR) and medium pores (10-MR). The pore topology of ITQ-39 is very attractive for catalysis and shows excellent results for the preparation of cumene by alkylation of benzene, while it can be a promising additive for FCC. PMID:21591745

Moliner, Manuel; Gonzlez, Jorge; Portilla, M Teresa; Willhammar, Tom; Rey, Fernando; Llopis, Francisco J; Zou, Xiaodong; Corma, Avelino

2011-06-22

11

Investigation of the Physicochemical Changes Preceding Zeolite Nucleation in a Sodium-Rich Aluminosilicate Gel  

E-print Network

-high-resolution transmission electron microscopy-energy-dispersive spec- trometry methods complemented by X-ray diffraction the initial polymerization of aluminosilicate species a significant part of the sodium hydroxide is expelled from the gel into the solution, which restricts extensive polymerization and leads to formation

Bao, Xinhe

12

First-principles molecular modeling of structure-property relationships and reactivity in the zeolite chabazite  

E-print Network

Zeolites are crystalline, porous aluminosilicates; while a pure silicate structure is charge-neutral, the substitution of A1? for Si?? creates in the framework a negative charge, which can be compensated by a proton that ...

Lo, Cynthia

2005-01-01

13

?-? interaction of aromatic groups in amphiphilic molecules directing for single-crystalline mesostructured zeolite nanosheets  

NASA Astrophysics Data System (ADS)

One of the challenges in material science has been to prepare macro- or mesoporous zeolite. Although examples of their synthesis exist, there is a need for a facile yet versatile approach to such hierarchical structures. Here we report a concept for designing a single quaternary ammonium head amphiphilic template with strong ordered self-assembling ability through ?-? stacking in hydrophobic side, which stabilizes the mesostructure to form single-crystalline mesostructured zeolite nanosheets. The concept is demonstrated for the formation of a new type of MFI (zeolite framework code by International Zeolite Association) nanosheets joined with a 90 rotational boundary, which results in a mesoporous zeolite with highly specific surface area even after calcination. Low binding energies for this self-assembling system are supported by a theoretical analysis. A geometrical matching between the arrangement of aromatic groups and the zeolitic framework is speculated for the formation of single-crystalline MFI nanosheets.

Xu, Dongdong; Ma, Yanhang; Jing, Zhifeng; Han, Lu; Singh, Bhupendra; Feng, Ji; Shen, Xuefeng; Cao, Fenglei; Oleynikov, Peter; Sun, Huai; Terasaki, Osamu; Che, Shunai

2014-06-01

14

Growth of zeolite crystals in the microgravity environment of space  

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

15

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)

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).

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

2013-06-01

16

ZEOLITE COATING SYSTEM FOR CORROSION CONTROL TO ELIMINATE HEXAVALENT CHROMIUM FROM DOD APPLICATIONS  

Microsoft Academic Search

Zeolites are microporous crystalline aluminosilicates with uniform and molecular sized pores. They are non-toxic and have been explored for medical applications. We have been investigating the application of zeolite films as chromium-free protective coatings on aluminum alloys. We have shown that as-synthesized organic template containing high-silica-zeolite (HSZ) MFI coatings on AA-2024-T3 are non-porous and have excellent corrosion resistance in strong

Derek E. Beving; Cory R. O'Neill; Yushan Yan; Nicole Anderson

17

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

PubMed

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 296mg CaCO3/g, comparable to commercially-available zeolite (310mg 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

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

2014-11-01

18

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

ERIC Educational Resources Information Center

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

Saini, Vipin K.; Pires, Joao

2012-01-01

19

Stable single-unit-cell nanosheets of zeolite MFI as active and long-lived catalysts  

Microsoft Academic Search

Zeolites-microporous crystalline aluminosilicates-are widely used in petrochemistry and fine-chemical synthesis because strong acid sites within their uniform micropores enable size- and shape-selective catalysis. But the very presence of the micropores, with aperture diameters below 1nm, often goes hand-in-hand with diffusion limitations that adversely affect catalytic activity. The problem can be overcome by reducing the thickness of the zeolite crystals, which

Minkee Choi; Kyungsu Na; Jeongnam Kim; Yasuhiro Sakamoto; Osamu Terasaki; Ryong Ryoo

2009-01-01

20

Structural Characterization of Nanosheet-type MFI Zeolite  

NASA Astrophysics Data System (ADS)

Zeolites are microporous crystalline aluminosilicates and have ordered micropores of a few in the structure. Zeolites are widely used in petrochemistry and fine-chemical synthesis because strong acid sites within their uniform micropores enable size- and shape-selective catalysis. Here we show that appropriately designed bifunctional surfactants can direct the formation of zeolite structures on the mesoporous and microporous length scales simultaneously, and thus produce nanosheet-type MFI zeolite that are only 2 nm thick, which corresponds to the b-axis dimension of a single MFI unit cell. The nanosheet-type MFI zeolite showd a significantly increased surface area, high catalytic activities, and excellent thermal and hydrothermal stability.

Sakamoto, Yasuhiro; Choi, Minkee; Na, Kyungsu; Kim, Jeongnam; Park, Woojin; Ryoo, Ryong; Terasaki, Osamu

21

Structural, compositional and acidic characteristics of nanosized amorphous or partially crystalline  

E-print Network

and thoroughly charac- terized by chemical analysis, XRD, FT-IR, solid state MAS NMR, N2 adsorption, TEM, NH3-TPD hydrothermal synthesis temperature and % relative XRD crystallinity. Incorporation of aluminum in the ZSM-5-ray amorphous aluminosilicates possessed tetrahedral aluminum atoms which were more zeolitic in character

Trikalitis, Pantelis N.

22

Solid state radioluminescent sources using zeolites  

Microsoft Academic Search

Inorganic zeolites show promise as an alternative to traditional tritium gas tube light sources. Greater proximity of tritium atoms and luminescing centers, as well as greater tritium loading density, have been obtained within the zeolite aluminosilicate matrix. Zeolites are in addition optically clear and radiation stable. The zeolite radioluminescence program is described. Procedures for obtaining light sources are presented and

John T. Gill; Daniel B. Hawkins; Clifford L. Renschler

1990-01-01

23

Solid state radioluminescent sources using zeolites  

NASA Astrophysics Data System (ADS)

Inorganic zeolites show promise as an alternative to traditional tritium gas tube light sources. Greater proximity of tritium atoms and luminescing centers, as well as greater tritium loading density, have been obtained within the zeolite aluminosilicate matrix. Zeolites are in addition optically clear and radiation stable. The zeolite radioluminescence program is described. Procedures for obtaining light sources are presented and results are discussed.

Gill, John T.; Hawkins, Daniel B.; Renschler, Clifford L.

24

Scratch-resistant zeolite anti-reflective coating on glass for solar applications  

Microsoft Academic Search

Sol-gel SiO2 anti-reflection (AR) coating on solar glass is known to increase the current output by a few percent, but its mechanical durability is of concern. To improve its strength, the amorphous SiO2 may be replaced by zeolite, which is a microporous aluminosilicate crystalline material. Scratch-resistant AR coating has been prepared by the dip coating of a composition which contains

Chien-Hung Chen; Shiao-Yi Li; Anthony S. T. Chiang; Albert T. Wu; Y. S. Sun

2011-01-01

25

Synthesis strategies in the search for hierarchical zeolites.  

PubMed

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

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

2013-05-01

26

Solid state radioluminescent sources using tritium-loaded zeolites  

Microsoft Academic Search

Zeolite-based tritium lamps are a possible alternative to traditional tritium gas tube light sources. Rare earth luminescing centers may be ion-exchanged into zeolite matrices. Close proximity of tritium atoms to the rare earths can be provided by highly tritiated water sorbed within the pore structure of the zeolite aluminosilicate matrix. Zeolites are optically clear and radiation stable. Light outputs from

J. T. Gill; D. B. Hawkins; C. L. Renschler

1991-01-01

27

Solid state radioluminescent sources using tritium-loaded zeolites, and their proposed use as process monitors  

Microsoft Academic Search

Zeolite-based tritium lamps are a possible alternative to traditional tritium gas tube light sources. Rare earth luminescing centers may be ion-exchanged into zeolite matrices. Close proximity of tritium atoms to the rate earths can be provided by highly tritiated water sorbed within the pore structure of the zeolite aluminosilicate matrix. Zeolites are optically clear and radiation stable. Light outputs up

J. T. Gill; D. B. Hawkins; C. L. Renschler

1992-01-01

28

Hot isostatically-pressed aluminosilicate glass-ceramic with natural crystalline analogues for immobilizing the calcined high-level nuclear waste at the Idaho Chemical Processing Plant  

SciTech Connect

The additives Si, Al, MgO, P{sub 2}O{sub 5} were mechanically blended with fluorinelsodium calcine in varying proportions. The batches were vacuum sealed in stainless steel canisters and hot isostatically pressed at 20,000 PSI and 1000 C for 4 hours. The resulting suite of glass-ceramic waste forms parallels the natural rocks in microstructural and compositional heterogeneity. Several crystalline phases ar analogous in composition and structure to naturally occurring minerals. Additional crystalline phases are zirconia and Ca-Mg borate. The glasses are enriched in silica and alumina. Approximately 7% calcine elements occur dissolved in this glass and the total glass content in the waste forms averages 20 wt%. The remainder of the calcine elements are partitioned into crystalline phases at 75 wt% calcine waste loading. The waste forms were tested for chemical durability in accordance with the MCC1-test procedure. The leach rates are a function of the relative proportions of additives and calcine, which in turn influence the composition and abundances of the glass and crystalline phases. The DOE leach rate criterion of less than 1 g/m{sup 2}-day is met by all the elements B, Cs and Na are increased by lowering the melt viscosity. This is related to increased crystallization or devitrification with increases in MgO addition. This exploratory work has shown that the increases in waste loading occur by preferred partitioning of the calcine components among crystalline and glass phases. The determination of optimum processing parameters in the form of additive concentration levels, homogeneous blending among the components, and pressure-temperature stabilities of phases must be continued to eliminate undesirable effects of chemical composition, microstructure and glass devitrification.

Raman, S.

1993-12-01

29

Hot isostatically-pressed aluminosilicate glass-ceramic with natural crystalline analogues for immobilizing the calcined high-level nuclear waste at the Idaho Chemical Processing Plant  

Microsoft Academic Search

The additives Si, Al, MgO, PO were mechanically blended with fluorinelsodium calcine in varying proportions. The batches were vacuum sealed in stainless steel canisters and hot isostatically pressed at 20,000 PSI and 1000 C for 4 hours. The resulting suite of glass-ceramic waste forms parallels the natural rocks in microstructural and compositional heterogeneity. Several crystalline phases ar analogous in composition

1993-01-01

30

Microprobes aluminosilicate ceramic membranes  

DOEpatents

Methods have been developed to make mixed alumina-silicate and aluminosilicate particulate microporous ceramic membranes. One method involves the making of separate alumina and silica sols which are then mixed. Another method involves the creation of a combined sol with aluminosilicate particles. The resulting combined alumina and silica membranes have high surface area, a very small pore size, and a very good temperature stability.

Anderson, Marc A. (2114 Chadbourne Ave., Madison, WI 53705); Sheng, Guangyao (45 N. Orchard St., Madison, WI 53715)

1993-01-01

31

Solid state radioluminescent sources using tritium-loaded zeolites  

NASA Astrophysics Data System (ADS)

Zeolite-based tritium lamps are a possible alternative to traditional tritium gas tube light sources. Rare earth luminescing centers may be ion-exchanged into zeolite matrices. Close proximity of tritium atoms to the rare earths can be provided by highly tritiated water sorbed within the pore structure of the zeolite aluminosilicate matrix. Zeolites are optically clear and radiation stable. Light outputs from tritium-loaded zeolites are shown here to exceed 2 micro-W/sq cm, with good stability. Procedures for obtaining light sources are presented and results are discussed. The possible use of these luminescent materials as process monitors for zeolite absorption columns in tritium service is also discussed.

Gill, J. T.; Hawkins, D. B.; Renschler, C. L.

32

Composites of microporous aluminum phosphates and zeolites and conversions over these catalysts  

SciTech Connect

A process for dewaxing a hydrocarbon feedstock is described comprising contacting the feedstock under sufficient dewaxing conditions with a catalyst composition comprising (i) a catalytically active crystalline silicate and (ii) a crystalline aluminum phosphate, wherein the crystalline silicate is an aluminosilicate zeolite having a silica to alumina mole ratio of from about 2 to about 500, and wherein the aluminum phosphate has a microporous framework structure in which the pores are uniform and have nominal diameters within the range of about 3 to 10 Angstroms. The aluminum phosphate has an intracrystalline adsorption capacity for water at 4.6 torr and 24/sup 0/C of at least 3.5 weight percent. The adsorption and desorption of water in the aluminum phosphate is completely reversible while retaining the same essential phosphate framework topology in both the hydrated and dehydrated state.

Kirker, G.W.; Landis, M.E.; Yen, J.H.

1988-02-09

33

Surface and interface investigation of aluminosilicate biomaterial by the in vivo experiments  

Microsoft Academic Search

Porous mixtures of aluminosilicate\\/calcium phosphate have been studied for biomaterials applications. Aluminosilicates formed with an inorganic polymeric constitution present amorphous zeolites because of their 3D network structure and present the ability to link to bone matrix. Amorphous geopolymers of the potassiumpoly(sialate)nanopolymer type were synthesised at low temperature and studied for their use as potential biomaterials. They were mixed with 13%

H. Oudadesse; A. C. Derrien; S. Martin; H. Chaair; G. Cathelineau

2008-01-01

34

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

SciTech Connect

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''.

Grutzeck, Michael W.

2005-06-27

35

Functionalized Amorphous Aluminosilicates  

NASA Astrophysics Data System (ADS)

Alkali treated aluminosilicate (geopolymer) was functionalized by surfactant to increase the hydrophobicity for making Pickering emulsion for the first part of this work. In the first part of this study, alkali treated metakaolin was functionalized with cetyltrimethylammonium bromide ((C16H33)N(CH 3)3Br, CTAB). The electrostatic interaction between this quaternary ammonium and the surface of the aluminosilicate which has negative charge has taken place. The particles then were used to prepare Pickering emulsion. The resulting stable dispersions, obtained very fast at very simple conditions with low ratio of aluminosilicate to liquid phase. In the second part, the interaction between geopolymer and glycerol was studied to see the covalent grafting of the geopolymer for making geopolymer composite. The composite material would be the basis material to be used as support catalyst, thin coating reagent and flame retardant material and so on, Variety of techniques, Thermogravimetric (TGA), Particle-induced X-ray emission (PIXE), FTIR, Solid state NMR, Powder X-ray diffraction (PXRD), BET surface area, Elemental analysis (CHN), TEM, SEM and Optical microscopy were used to characterize the functionalized geopolymer.

Mesgar, Milad

36

Aluminosilicate cementation of saprolites, grits and silcretes in Western Australia  

Microsoft Academic Search

Amorphous to poorly crystalline aluminosilicates have been found as cementing agents within saprolites, hardpans and silcretes, particularly in granitic terrains in the Yilgarn Block, Western Australia. The cements range mineralogically from siliceous allophane to a kaolinite?opal?CT assemblage probably derived from the allophane. The allophane is non?crystalline, with no distinctive X?ray or electron diffraction patterns, and has close optical similarities to

C. R. M. Butt

1983-01-01

37

Study of the ethanolic tributylmethylammonium aluminosilicate solutions using 27Al NMR  

Microsoft Academic Search

Alkaline solutions containing both silicate and aluminate ions are of considerable research interest inter alia because of their involvement in the synthesis of zeolites. In the present work, we use 27Al NMR to characterize alkaline aqueous and ethanolic tributylmethylammonium aluminosilicate solutions with different Al\\/Si ratios. Tributylmethylammonium (TBMA) used as a cation template and no alkaline metals are used for preparation

Nasser Goudarzi; Mohammad Goodarzi; M. Arab Chamgangali; G. Bagherian

2009-01-01

38

Properties and applications of zeolites.  

PubMed

Zeolites are aluminosilicate solids bearing a negatively charged honeycomb framework of micropores into which molecules may be adsorbed for environmental decontamination, and to catalyse chemical reactions. They are central to green-chemistry since the necessity for organic solvents is minimised. Proton-exchanged (H) zeolites are extensively employed in the petrochemical industry for cracking crude oil fractions into fuels and chemical feedstocks for other industrial processes. Due to their ability to perform cation-exchange, in which the cations that are originally present to counterbalance the framework negative charge may be exchanged out of the zeolite by cations present in aqueous solution, zeolites are useful as industrial water-softeners, in the removal of radioactive Cs+ and Sr2+ cations from liquid nuclear waste and in the removal of toxic heavy metal cations from groundwaters and run-off waters. Surfactant-modified zeolites (SMZ) find particular application in the co-removal of both toxic anions and organic pollutants. Toxic anions such as arsenite, arsenate, chromate, cyanide and radioactive iodide can also be removed by adsorption into zeolites that have been previously loaded with co-precipitating metal cations such as Ag+ and Pb2+ which form practically insoluble complexes that are contained within the zeolite matrix. PMID:21047018

Rhodes, Christopher J

2010-01-01

39

Low-Temperature luminescence spectra of naphthalene adsorbed on crystalline and amorphous adsorbents  

Microsoft Academic Search

ofor the existence of strong intracrystalline fields (on the order of v\\/A units) in the adsorption cavities [7]. This is the reason for the existence of the strong perturbing effect of the zeolite matrix on adsorbed molecules [8-13]. We studied isostructural zeolites containing different amounts of sodium cations in the cell and also decationized zeolites. The amorphous adsorbents, Na aluminosilicate

A. M. Eremenko; M. A. Piontko vskaya; I. E. Neimark

1971-01-01

40

Kinetics of silicate exchange in alkaline aluminosilicate solutions.  

PubMed

In strongly alkaline aqueous KOH solutions containing SiIV in large excess over AlIII, the kinetics of exchange of monomeric silicate with small acyclic aluminosilicate solute species is much more rapid than with either cyclic aluminosilicates or any all-silicate anions. Selective inversion recovery 29Si NMR studies of homogeneous solutions of stoichiometric composition 3.0 mol kg-1 of SiO2, 0.1 mol kg-1 of Al2O3, and 8.0 mol kg-1 of K2O in 60-75% D2O gave rate constants of 2.0 +/- 0.2 kg mol-1 s-1 and 17 +/- 4 s-1 for the forward and reverse reactions of monomeric silicate with (HO)3AlOSiOn(OH)(3-n)(n+1)- (n = 2 or 3) at 0 degree C. These rate constants are more than 10(4)-fold faster than those extrapolated from 60 to 90 degrees C for comparable reactions of silicate anions. The greater lability of acyclic aluminate centers relative to silicate is ascribed partly to the availability of HO- groups for condensation reactions on Al and mainly to the ease of expansion of the coordination number of AlIII beyond 4. The latter attribute is diminished when AlIII is constrained to be tetrahedral in cyclic structures. With respect to the mechanism of formation of zeolites from alkaline aqueous media, it is suggested that small, labile AlOSi units add rapidly to growing zeolitic structures "on demand", whereas the more kinetically inert cage or ring structures cannot. This would explain why a silicate or aluminosilicate structure that is dominant among solute species at equilibrium in the presence of a particular cation may bear little or no geometric relation to the zeolitic framework promoted kinetically by that same cation. PMID:11197023

North, M R; Swaddle, T W

2000-06-12

41

Synthesis and testing of nanosized zeolite Y  

NASA Astrophysics Data System (ADS)

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)

Karami, Davood

42

Zeolites and Intrazeolite Chemistry: Insights from Infrared Spectroscopy  

Microsoft Academic Search

Zeolites are widely used as adsorbents, catalysts, ion exchangers and molecular sieves. However, less is known about the potential use of zeolites and related microporous solids for tailored synthesis of advanced materials. Zeolite-based host-guest nanocomposites are a type of advanced material in which zeolites act as hosts for encapsulating and organizing molecules, crystalline nano-phases and supramolecular entities inside the zeolite

C. Otero Aren

2000-01-01

43

Salt-occluded zeolite waste forms: Crystal structures and transformability  

SciTech Connect

Neutron diffraction studies of salt-occluded zeolite and zeolite/glass composite samples, simulating nuclear waste forms loaded with fission products, have revealed complex structures, with cations assuming the dual roles of charge compensation and occlusion (cluster formation). These clusters roughly fill the 6--8 {angstrom} diameter pores of the zeolites. Samples are prepared by equilibrating zeolite-A with complex molten Li, K, Cs, Sr, Ba, Y chloride salts, with compositions representative of anticipated waste systems. Samples prepared using zeolite 4A (which contains exclusively sodium cations) as starting material are observed to transform to sodalite, a denser aluminosilicate framework structure, while those prepared using zeolite 5A (sodium and calcium ions) more readily retain the zeolite-A structure. Because the sodalite framework pores are much smaller than those of zeolite-A, clusters are smaller and more rigorously confined, with a correspondingly lower capacity for waste containment. Details of the sodalite structures resulting from transformation of zeolite-A depend upon the precise composition of the original mixture. The enhanced resistance of salt-occluded zeolites prepared from zeolite 5A to sodalite transformation is thought to be related to differences in the complex chloride clusters present in these zeolite mixtures. Data relating processing conditions to resulting zeolite composition and structure can be used in the selection of processing parameters which lead to optimal waste forms.

Richardson, J.W. Jr. [Argonne National Lab., IL (United States). Intense Pulsed Neutron Source Div.

1996-12-31

44

The growth of zeolites A, X and mordenite in space  

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

45

Crystalline Membranes  

NASA Technical Reports Server (NTRS)

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.

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

2008-01-01

46

Reclaiming silver from silver zeolite  

SciTech Connect

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.

Reimann, G.A.

1991-10-01

47

Reclaiming silver from silver zeolite  

SciTech Connect

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.

Reimann, G.A.

1991-10-01

48

Layered zeolitic materials: an approach to designing versatile functional solids.  

PubMed

Relevant layered zeolites have been considered in this perspective article from the point of view of the synthesis methodologies, materials characterization and catalytic implications, considering the unique physico-chemical characteristics of lamellar materials. The potential of layered zeolitic precursors to generate novel lamellar accessible zeolites through swelling, intercalation, pillarization, delamination and/or exfoliation treatments is studied, showing the chemical, functional and structural versatility exhibited by layered zeolites. Recent approaches based on the assembly of zeolitic nanosheets which act as inorganic structural units through the use of dual structural directing agents, the selective modification of germanosilicates and the direct generation of lamellar hybrid organic-inorganic aluminosilicates are also considered to obtain layered solids with well-defined functionalities. The catalytic applications of the layered zeolites are also highlighted, pointing out the high accessibility and reactivity of active sites present in the lamellar framework. PMID:24457617

Daz, Urbano; Corma, Avelino

2014-07-21

49

Zeolite Studies. Aluminium Phosphate Zeolites.  

National Technical Information Service (NTIS)

Alpo-zeolites (ALPO sub 4 -zeolites) have been synthesized by hydrothermal synthesis in an autoclave from alumina, tetralkylammonium hydroxide and phosphorus acid. Catalysis tests with hydrocarbons indicate that the compounds have good olefinisomerization...

G. S. Haegh, U. Blindheim

1983-01-01

50

Structural and diffusion characterizations of steam-stable mesostructured zeolitic UL-ZSM-5 materials.  

PubMed

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

Vinh-Thang, Hoang; Huang, Qinglin; Ungureanu, Adrian; Ei?, Mladen; Trong-On, Do; Kaliaguine, Serge

2006-05-01

51

Binding and catalytic reduction of NO by transition metal aluminosilicates  

SciTech Connect

The objective of this research is to provide the scientific understanding of processes that actively and selectively reduce NO in dilute exhaust streams, as well as in concentrated streams, to N{sub 2}. Experimental studies of NO chemistry in transition metal-containing aluminosilicate catalysts are being carried out with the aim of determining the chemical rules for NO reduction on non-precious metals. The catalyst supports chosen for this investigation are A and Y zeolites, mordenite, and monoliths based on cordierite. The supported transition metal cations that were examined are principally the first row redox metals, e.g. Cr(2), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Cu(I). The reactions of interest are the reductions of NO by H{sub 2}, CO, and CH{sub 4}, as well as the disproportionation of NO. Rare earth cations that possess redox properties were placed in the more shielded sites, e.g. Site I in Y zeolite, prior to or simultaneously with the exchange procedure with the transition metal cations. Theoretical calculations of the electronic structure of the transition metal cations in zeolitic sites were carried out by ab initio methods. The aim of this part of the research is to find the best match between the metal-based antibonding orbitals and the antibonding orbitals of the NO molecule such that the N-O bond is weakened and is readily broken. 9 refs., 4 figs., 3 tabs.

Klier, K.; Herman, R.G.; Hou, Shaolie.

1991-09-01

52

Mineral resource of the month: natural and synthetic zeolites  

USGS Publications Warehouse

Robert Virta, mineral commodity specialist for the U.S. Geological Survey, prepared the following information about the zeolite industry. Volcanic rocks containing natural zeolites hydrated aluminosilicate minerals that contain alkaline and alkaline-earth metals have been mined worldwide for more than 1,000 years for use as cements and building stone. For centuries, people thought natural zeolites occurred only in small amounts inside cavities of volcanic rock. But in the 1950s and early 1960s, large zeolite deposits were discovered in volcanic tuffs in the western United States and in marine tuffs in Italy and Japan. And since then, similar deposits have been found around the world, from Hungary to Cuba to New Zealand. The discovery of these larger deposits made commercial mining of natural zeolite possible.

Virta, R.

2008-01-01

53

Study of pure-silica Zeolite Nucleation and Growth from Solution  

E-print Network

Zeolites are microporous crystalline materials, which are widely used in catalysis, adsorption, and ion-exchange processes. However, in most cases, the synthesis of novel zeolites as functional materials still relies on trial-and-error methods...

Li, Xiang

2011-10-21

54

Structure and catalytic properties of the most complex intergrown zeolite ITQ-39 determined by electron crystallography  

NASA Astrophysics Data System (ADS)

Porous materials such as zeolites contain well-defined pores in molecular dimensions and have important industrial applications in catalysis, sorption and separation. Aluminosilicates with intersecting 10- and 12-ring channels are particularly interesting as selective catalysts. Many porous materials, especially zeolites, form only nanosized powders and some are intergrowths of different structures, making structure determination very challenging. Here, we report the atomic structures of an aluminosilicate zeolite family, ITQ-39, solved from nanocrystals only a few unit cells in size by electron crystallography. ITQ-39 is an intergrowth of three different polymorphs, built from the same layer but with different stacking sequences. ITQ-39 contains stacking faults and twinning with nano-sized domains, being the most complex zeolite ever solved. The unique structure of ITQ-39, with a three-dimensional intersecting pairwise 12-ring and 10-ring pore system, makes it a promising catalyst for converting naphtha into diesel fuel, a process of emerging interest for the petrochemical industry.

Willhammar, Tom; Sun, Junliang; Wan, Wei; Oleynikov, Peter; Zhang, Daliang; Zou, Xiaodong; Moliner, Manuel; Gonzalez, Jorge; Martnez, Cristina; Rey, Fernando; Corma, Avelino

2012-03-01

55

Biaxial Q-shearing of 27Al 3QMAS NMR spectra: insight into the structural disorder of framework aluminosilicates.  

PubMed

In this contribution, we present the application potentiality of biaxial Q-shearing of (27)Al 3QMAS NMR spectra in the analysis of structural defects of aluminium units in aluminosilicates. This study demonstrates that the combination of various shearing transformations of the recorded (27)Al 3QMAS NMR spectra enables an understanding of the broadening processes of the correlation signals of disordered framework aluminosilicates, for which a wide distribution of (27)Al MAS NMR chemical shifts and quadrupolar parameters (i.e., second-order quadrupolar splitting and quadrupole-induced chemical shifts) can be expected. By combining the suitably selected shearing transformation procedures, the mechanisms of the formation of local defects in aluminosilicate frameworks, including Al/Si substitution effects in the next-nearest neighbouring T-sites, variations in bond angles, and/or variations in the physicochemical nature of charge-balancing counter-ions, can be identified. The proposed procedure has been extensively tested on a range of model aluminosilicate materials (kyanite, ?-alumina, metakaolin, analcime, chabazite, natrolite, phillipsite, mordenite, zeolite A, and zeolite Y). PMID:24333044

Kobera, Libor; Brus, Jiri; Klein, Petr; Dedecek, Jiri; Urbanova, Martina

2014-01-01

56

PHYSICAL, CHEMICAL AND STRUCTURAL EVOLUTIION OF ZEOLITE-CONTAINING WASTE FORMS PRODUCED FROM METAKAOLINITE AND CALCINED SODUIM BEARING WASTE (HLW AND/OR LLW)  

SciTech Connect

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 Romans used blocks of zeolitized tuff as a building material. Using zeolites for the management of radioactive waste is not new, 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 precursors. The process under study is derived from a well known method in which metakaolin (thermally dehydroxylated kaolin a mixture of kaolinite and smaller amounts of quartz and mica that has been heated to {approx}700 C) is mixed with sodium hydroxide (NaOH) and water 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 just enough concentrated sodium hydroxide solution is added to the metakaolinite to make a thick paste and then the paste is cured under mild hydrothermal conditions (60-200 C), the mixture forms a concrete-like ceramic material made up of distinct crystalline tectosilicate minerals (zeolites and feldspathoids) imbedded in an X-ray amorphous hydrated sodium aluminosilicate matrix. Due to its vitreous character we have chosen to call this composite a ''hydroceramic''. Similar to zeolite powders, a hydroceramic is able to sequester cations in both lattice positions and within the channels and voids present in its tectosilicate framework structure. It can also accommodate a wide range of salt molecules (e.g., sodium nitrate) within these same openings thus rendering them insoluble. Due to its fine crystallite size and cementing character, the matrix develops significant physical strength. The obvious similarities between a hydroceramic waste form and a waste form based on solidified Portland cement grout are only superficial because their chemistries are entirely different. In addition to being vastly superior to conventional Portland cement grouts with respect to salt retention, standard radwaste leach protocols (PCT, TCLP, etc.) have shown that hydroceramics also do a better job of immobilizing the RCRA-toxic and radioactive components of ''sodium bearing wastes'' (SBWs).

Grutzeck, Michael W.

2004-06-10

57

Assessment of the Antiviral Properties of Zeolites Containing Metal Ions  

Microsoft Academic Search

The antiviral properties of zeolite (sodium aluminosilicate) powders amended with metal ions were assessed using human coronavirus\\u000a 229E, feline infectious peritonitis virus (FIPV), and feline calicivirus F-9. Zeolites containing silver and silver\\/copper\\u000a caused significant reductions of coronavirus 229E after 1h in suspension. The silver\\/copper combination yielded a >5.13-log10 reduction within 24h. It was also the most effective (>3.18-log10) against FIPV

Kelly R. Bright; Enue E. Sicairos-Ruelas; Patricia M. Gundy; Charles P. Gerba

2009-01-01

58

Computational studies of water adsorption in zeolites  

SciTech Connect

We have performed high-level ab initio calculations using Hartree-Fock (HF) theory, Moller-Plesset perturbation theory (MP2), and density-functional theory (DFT) to study the geometry and energetics of the adsorption complex involving H{sub 2}O and the Bronsted acid site in the zeolite H-ZSM-5. These calculations use aluminosilicate cluster models for the zeolite framework with as many as 28 T atoms (T=Si, Al). We included geometry optimization in the local vicinity of the acid site at the MP2 and DFT levels of theory for the smallest cluster, while in the larger clusters this was done at the HF/6-31G(d) level of theory. We have also calculated corrections for zero-point energies, extensions to higher basis sets, and higher levels of electron correlation. Results for the adsorption energy and geometry of this complex are reported and compared with previous theoretical and experimental values.

Zygmunt, S.A. [Valparaiso Univ., IN (United States); Curtiss, L.A.; Iton, L.E. [Argonne National Lab., IL (United States)

1995-05-01

59

Single and Multiple Heteroatom Incorporation in MFI Zeolites  

E-print Network

Zeolites are crystalline inorganic solids that are industrially used for adsorption, ion exchange and catalysis. As catalysts, they have been particularly successful in the hydrocarbon processing industry due to their unique activities...

Garcia Vargas, Nataly

2012-11-05

60

High-Aluminum-Affinity Silica Is a Nanoparticle That Seeds Secondary Aluminosilicate Formation  

PubMed Central

Despite the importance and abundance of aluminosilicates throughout our natural surroundings, their formation at neutral pH is, surprisingly, a matter of considerable debate. From our experiments in dilute aluminum and silica containing solutions (pH ~ 7) we previously identified a silica polymer with an extraordinarily high affinity for aluminium ions (high-aluminum-affinity silica polymer, HSP). Here, further characterization shows that HSP is a colloid of approximately 2.4 nm in diameter with a mean specific surface area of about 1,000 m2 g-1 and it competes effectively with transferrin for Al(III) binding. Aluminum binding to HSP strongly inhibited its decomposition whilst the reaction rate constant for the formation of the ?-silicomolybdic acid complex indicated a diameter between 3.6 and 4.1 nm for these aluminum-containing nanoparticles. Similarly, high resolution microscopic analysis of the air dried aluminum-containing silica colloid solution revealed 3.9 1.3 nm sized crystalline Al-rich silica nanoparticles (ASP) with an estimated Al:Si ratio of between 2 and 3 which is close to the range of secondary aluminosilicates such as imogolite. Thus the high-aluminum-affinity silica polymer is a nanoparticle that seeds early aluminosilicate formation through highly competitive binding of Al(III) ions. In niche environments, especially in vivo, this may serve as an alternative mechanism to polyhydroxy Al(III) species binding monomeric silica to form early phase, non-toxic aluminosilicates. PMID:24349573

Jugdaohsingh, Ravin; Brown, Andy; Dietzel, Martin; Powell, Jonathan J.

2013-01-01

61

Zeolites: Can they be synthesized by design  

SciTech Connect

Zeolites and zeolite-like molecular sieves are crystalline oxides that have high surface-to-volume ratios and are able to recognize, discriminate, and organize molecules with differences of < 1 [angstrom]. The close connection between the atomic structure and macroscopic properties of these materials has led to uses in molecular recognition. For example, zeolites and zeolite-like molecular sieves can reveal marvelous molecular recognition specificity and sensitivity that can be applied to catalysis, separations technology, and chemical sensing. Additionally, they can serve as hosts to organize guest atoms and molecules that endow composite materials with optoelectric and electrochemical properties. Because of the high level of structural control necessary to create high-performance materials with zeolites or zeolite-like molecular sieves, the design and synthesis of these solids with specific architectures and properties are highly desired. Although this lofty goal is still elusive, advances have been made to allow the serious consideration of designing molecular sieves. Here, the author covers two aspects of this ongoing effort. First, he discusses the feasibility of designing pore architectures through the use of organic structure-directing agents. Second, he explores the possibility of creating zeolites through ''Lego chemistry.''

Davis, M.E. (California Inst. of Technology, Pasadena, CA (United States))

1994-09-01

62

Assessing different zeolitic adsorbents for their potential use in Kr and Xe separation  

NASA Astrophysics Data System (ADS)

Separation of Kr from Xe is an important problem in spent nuclear fuel fission gas management. The energy intensive and expensive cryogenic distillation method is currently used to separate these gases. In this thesis, we have carried out the research into appropriate sorbents for the separation of Kr and Xe using pressure swing adsorption. We have examined zeolites using gas adsorption studies as they have the potential to be more cost effective than other sorbents. Zeolites are microporous aluminosilicates and have ordered pore structures. The pores in zeolites have extra-framework cations are substantially free to move. The mobility of cations and the uniformity in pore size permits the separation and removal of gases in zeolites. In our experiment, first, we have measured adsorption isotherms with same zeolitic framework but with different cations. Second, we have measured the adsorption isotherm with different zeolitic frameworks but with same cation. Using these adsorption isotherms, we have calculated the initial heats of adsorption to find out the strength of interaction between the zeolitic framework and the gases. Finally, we have compared the difference in the initial heats of adsorption to find the suitable zeolite that has the highest selectivity of Xe over Kr. In conclusion, we have found out that K LSX seems to have higher potential among the zeolites that we have compared for the separation of Kr from Xe with the differential heats of adsorption for Xe vs Kr as 7.4 kJ/mol.

Alagappan, Breetha

63

The ITQ-37 mesoporous chiral zeolite.  

PubMed

The synthesis of crystalline molecular sieves with pore dimensions that fill the gap between microporous and mesoporous materials is a matter of fundamental and industrial interest. The preparation of zeolitic materials with extralarge pores and chiral frameworks would permit many new applications. Two important steps in this direction include the synthesis of ITQ-33, a stable zeolite with 18 x 10 x 10 ring windows, and the synthesis of SU-32, which has an intrinsically chiral zeolite structure and where each crystal exhibits only one handedness. Here we present a germanosilicate zeolite (ITQ-37) with extralarge 30-ring windows. Its structure was determined by combining selected area electron diffraction (SAED) and powder X-ray diffraction (PXRD) in a charge-flipping algorithm. The framework follows the SrSi(2) (srs) minimal net and forms two unique cavities, each of which is connected to three other cavities to form a gyroidal channel system. These cavities comprise the enantiomorphous srs net of the framework. ITQ-37 is the first chiral zeolite with one single gyroidal channel. It has the lowest framework density (10.3 T atoms per 1,000 A(3)) of all existing 4-coordinated crystalline oxide frameworks, and the pore volume of the corresponding silica polymorph would be 0.38 cm(3) g(-1). PMID:19407798

Sun, Junliang; Bonneau, Charlotte; Cantn, Angel; Corma, Avelino; Daz-Cabaas, Mara J; Moliner, Manuel; Zhang, Daliang; Li, Mingrun; Zou, Xiaodong

2009-04-30

64

Adsorption of chromium ions from aqueous solution by using activated carbo-aluminosilicate material from oil shale.  

PubMed

A novel activated carbo-aluminosilicate material was prepared from oil shale by chemical activation. The chemicals used in the activation process were 95 wt% sulfuric and 5 wt% nitric acids. The produced material combines the sorption properties and the mechanical strength of both activated carbon and zeolite. An X-ray diffraction analysis shows the formation of zeolite Y, Na-X, and A-types, sodalite, sodium silicate, mullite, and cancrinite. FT-IR spectrum shows the presence of carboxylic, phenolic, and lactonic groups on the surface of this material. The zero point of charge estimated at different mass to solution ratio ranged from 7.9 to 8.3. Chromium removal by this material showed sorption capacity of 92 mg/g. PMID:16626724

Shawabkeh, Reyad Awwad

2006-07-15

65

Low-temperature synthesized aluminosilicate glasses  

Microsoft Academic Search

The reaction below 100 C of a dehydroxylated clay (metakaolinite: (Al2O3)(SiO2)2(H2O)0.05) suspended in an alkaline sodium silicate solution ((Na2O)(SiO2)1.4(H2O)x) leads to an amorphous glassy aluminosilicate, called in this work low-temperature inorganic polymer glass (LTIPG or IPG).

H. Rahier; B. VAN MELE; M. Biesemans; J. Wastiels; X. Wu

1996-01-01

66

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

NASA Astrophysics Data System (ADS)

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.

Beving, Derek Eugene

67

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...

68

Selective toluene disproportionation over pore size controlled MFI zeolite  

SciTech Connect

Selective disproportionate of toluene to p-xylene was studied over modified MFI aluminosilicate. The relationship between extent of silica deposition and para selectivity was established. The effect of reaction parameters such as temperature and weight hourly space velocity (WHSV) on para selectivity was considered. Kinetics of reaction in the temperature range 723--773 K was carried out. The estimated activation energy value is lower than reported for toluene disproportionation in the literature. This has been explained on the basis of enhanced intracrystalline diffusion in the modified zeolite.

Das, J.; Bhat, Y.S.; Halgeri, A.B. (Indian Petrochemicals Corp. Ltd., Gujarat (India). Research Centre)

1994-02-01

69

Electro-optical parameters of bond polarizability model for aluminosilicates.  

PubMed

Electro-optical parameters (EOPs) of bond polarizability model (BPM) for aluminosilicate structures were derived from quantum-chemical DFT calculations of molecular models. The tensor of molecular polarizability and the derivatives of the tensor with respect to the bond length are well reproduced with the BPM, and the EOPs obtained are in a fair agreement with available experimental data. The parameters derived were found to be transferable to larger molecules. This finding suggests that the procedure used can be applied to systems with partially ionic chemical bonds. The transferability of the parameters to periodic systems was tested in molecular dynamics simulation of the polarized Raman spectra of alpha-quartz. It appeared that the molecular Si-O bond EOPs failed to reproduce the intensity of peaks in the spectra. This limitation is due to large values of the longitudinal components of the bond polarizability and its derivative found in the molecular calculations as compared to those obtained from periodic DFT calculations of crystalline silica polymorphs by Umari et al. (Phys. Rev. B 2001, 63, 094305). It is supposed that the electric field of the solid is responsible for the difference of the parameters. Nevertheless, the EOPs obtained can be used as an initial set of parameters for calculations of polarizability related characteristics of relevant systems in the framework of BPM. PMID:16571058

Smirnov, Konstantin S; Bougeard, Daniel; Tandon, Poonam

2006-04-01

70

Inelastic X-ray Scattering Studies of Zeolite Collapse  

SciTech Connect

In situ inelastic x-ray scattering (IXS) experiments have been used to probe heterogeneity and deformability in zeolte Y as this thermally collapses to a high density amorphous (HDA) aluminosilicate phase. The Landau-Placzek ratio R{sub LP} falls slowly as amorphisation advances, increasing in the later stages of collapse clearly showing how homogeneity improves non-linearly--behaviour linked closely with the decline in molar volume V{sub Molar}. The Brillouin frequency {omega}{sub Q} also decreases with amorphisation in a similar fashion, signifying a non-uniform decrease in the speed of sound v{sub l}. All of these changes with zeolite amorphisation infer formation of an intermediate low density amorphous (LDA) phase. This low entropy or 'perfect glass' has mechanical properties which are closer to the zeolite rather to the HDA glass--notably a very small value of Poisson's Ratio signifying unusually low resistance to deformation.

Greaves, G. Neville; Kargl, Florian; Ward, David [Centre for Advanced Functional Materials and Devices, Institute of Mathematics and Physics, Aberystwyth University, Aberystwyth SY23 3BZ (United Kingdom); Holliman, Peter [Centre for Advanced Functional Materials and Devices, College of Physical and Applied Sciences, Bangor University, Bangor LL57 2UW (United Kingdom); Meneau, Florian [Centre for Advanced Functional Materials and Devices, SOLEIL, Orme des Merisiers, Batiment A, Saint Aubin, BP 48, 91192, Gif sur Yvette Cedex (France)

2009-01-29

71

ZEOLITE STRUCTURE ANALYSIS WITH POWDER X-RAY DIFFRACTION AND SOLID-STATE NMR TECHNIQUES  

Microsoft Academic Search

Large advances in the development of catalytic materials were made with the synthesis of zeolites, which are porous crystalline materials that can be used as catalysts, catalyst supports, sorbents and ion exchangers. Zeolite structures consist of T-atoms tetrahedrally coordinated to oxygen atoms, where T can be AI, Si, or any other element capable of isomorphous substitution for Si. The unavailability

G. T. KOKOTAILO; C. A. FYFE

72

Densification of salt-occluded zeolite a powders to a leach-resistant monolith  

SciTech Connect

Pyrochemical processing of spent fuel from the Integral Fast Reactor (IFR) yields a salt waste of LiCl-KCl that contains approximately 6 wt% fission products, primarily as CsCl and SrCl{sub 2}. Past work has shown that zeolite A will preferentially sorb cesium and strontium and will encapsulate the salt waste in a leach-resistant, radiation-resistant aluminosilicate matrix. However, a method is sill needed to convert the salt-occluded zeolite powders into a form suitable for geologic disposal. We are thus investigating a method that forms bonded zeolite by hot pressing a mixture of glass frit and salt-occluded zeolite powders at 990 K (717{degree}C) and 28 MPa. The leach resistance of the bonded zeolite was measured in static leach tests run for 28 days in 363 K (90{degree}C) deionized water. Normalized release rates of all elements in the bonded zeolite were low, <1 g/m{sup 2} d. Thus, the bonded zeolite may be a suitable waste form for IFR salt waste.

Lewis, M.A.; Fischer, D.F.; Murhpy, C.D.

1993-10-01

73

Structure and catalytic properties of the most complex intergrown zeolite ITQ-39 determined by electron crystallography.  

PubMed

Porous materials such as zeolites contain well-defined pores in molecular dimensions and have important industrial applications in catalysis, sorption and separation. Aluminosilicates with intersecting 10- and 12-ring channels are particularly interesting as selective catalysts. Many porous materials, especially zeolites, form only nanosized powders and some are intergrowths of different structures, making structure determination very challenging. Here, we report the atomic structures of an aluminosilicate zeolite family, ITQ-39, solved from nanocrystals only a few unit cells in size by electron crystallography. ITQ-39 is an intergrowth of three different polymorphs, built from the same layer but with different stacking sequences. ITQ-39 contains stacking faults and twinning with nano-sized domains, being the most complex zeolite ever solved. The unique structure of ITQ-39, with a three-dimensional intersecting pairwise 12-ring and 10-ring pore system, makes it a promising catalyst for converting naphtha into diesel fuel, a process of emerging interest for the petrochemical industry. PMID:22354432

Willhammar, Tom; Sun, Junliang; Wan, Wei; Oleynikov, Peter; Zhang, Daliang; Zou, Xiaodong; Moliner, Manuel; Gonzalez, Jorge; Martnez, Cristina; Rey, Fernando; Corma, Avelino

2012-03-01

74

Solid state NMR of porous materials : zeolites and related materials.  

PubMed

Solid state NMR spectroscopy applied to the science of crystalline micro- and mesoporous silica materials over the past 10 years is reviewed. A survey is provided of framework structure and connectivity analyses from chemical shift effects of various elements in zeolites including heteroatom substitutions, framework defects and pentacoordinated silicon for zeolites containing fluoride ions. New developments in the field of NMR crystallography are included. Spatial host-guest ordering and confinement effects of zeolite-sorbate complexes are outlined, with special emphasis on NMR applications utilizing the heteronuclear dipolar interaction. The characterization of zeolite acid sites and in situ NMR on catalytic conversions is also included. Finally, the motion of extra-framework cations is investigated in two tutorial cases of sodium hopping in sodalite and cancrinite. PMID:21452082

Koller, Hubert; Weiss, Mark

2012-01-01

75

Synthesis and catalytic applications of novel mesoporous aluminosilicate molecular sieves  

SciTech Connect

This paper reports on the synthesis of 4 series of mesoporous aluminosilicate molecular sieves (Al-MCM-41) and their catalytic applications. Four different Al compounds were examined as Al source in the hydrothermal synthesis, including pseudo boehmite (alumina), Al sulfate, Al isopropoxide, and Na aluminate. Each Al source was examined at 3 different feed Si/Al ratios in the synthesis. XRD results show that there are differences in the d{sub 100}-spacings for the samples prepared with different Al sources: Na aluminate > Al isopropoxide < Na aluminate. XRD also indicates that the synthesized Al-MCM-41 samples have different crystallinity. {sup 27}Al NMR and {sub 29}Si NMR reveal that most of the Al species in the samples prepared with pseudo boehmite were present in octahedral coordination, whereas in other samples nearly all the Al species are tetrahedral (in the framework). The acid characteristics of the synthesized molecular sieves were characterized by temperature-programmed desorption of n-butylamine, and by using 1,3,5-triisopropylbenzene hydrocracking as probe reaction. The results of TPD and probe reaction clearly indicate that the Al source used for synthesis has a major impact on the acidic and catalytic properties of Al-MCM-41. The samples prepared with Al isopropoxide and Na aluminate are better as catalysts than those with Al sulfate and pseudo boehmite. They also explored the potential of mesoporous molecular sieves as support for noble metal hydrogenation catalysts and metal sulfide-based hydrotreating catalysts. Pd and Pt-loaded mesoporous molecular sieves were prepared and applied for hydrogenation of naphthalene and phenanthrene. The results show that mesoporous molecular sieve-supported catalysts are much more active than alumina- and titania-supported catalysts. The data for dibenzothiophene hydrodesulfurization suggest that Al-MCM-41 supported Co-Mo may be effective for deep desulfurization of distillate fuels.

Reddy, K.M.; Song, C. [Pennsylvania State Univ., University Park, PA (United States)

1997-12-31

76

Multinuclear NMR investigation of the formation of aluminosilicate anions  

SciTech Connect

The structure of simple aluminosilicate anions formed by the reaction of silicate and aluminate anions was investigated by {sup 29}Si and {sup 27}Al NMR spectroscopy. The extent of aluminosilicate formation was found to increase with increasing silicate ratio and increasing cation size. The first of these trends is attributed to the redistribution of Si with increasing silicate ratio to more acidic anions. The second trend is attributed to the formation of cation-anion pairs.

McCormick, A.V.; Bell, A.T.; Radke, C.J. (Lawrence Berkeley Lab., CA (USA))

1989-03-09

77

Multinuclear NMR investigation of the formation of aluminosilicate anions  

Microsoft Academic Search

The structure of simple aluminosilicate anions formed by the reaction of silicate and aluminate anions was investigated by ²⁹Si and ²⁷Al NMR spectroscopy. The extent of aluminosilicate formation was found to increase with increasing silicate ratio and increasing cation size. The first of these trends is attributed to the redistribution of Si with increasing silicate ratio to more acidic anions.

A. V. McCormick; A. T. Bell; C. J. Radke

1989-01-01

78

Investigation of the electronic and dynamic properties of sodium and caesium exchanged zeolite by MO and MD simulations  

Microsoft Academic Search

For the pyrochemical reprocessing of spent metallic fuels in molten salt baths it is of importance to investigate the electronic and dynamic properties of the negative elements like Cs in aluminosilicates framework. The molecular orbital simulation has been performed on three types of clusters and 4A-zeolite frameworks with exchangeable alkali-ions containing as significant fission products in order to estimate the

Masahiko Matsumiya; Ryuzo Takagi

2002-01-01

79

A study of zeolite film synthesis on porous substrates  

NASA Astrophysics Data System (ADS)

Synthetic zeolites are attractive for chemical processing applications due to their high thermal and chemical stability. Potential new applications include zeolite membranes for gas separation, catalysis, sensor application, etc. The use of zeolite ZSM-5 for gas separation has been widely used due to the intermediate pore size. The formation of a zeolite layer on the heterogeneous surface depends on several factors. This study was conducted in order to investigate the synthesis techniques and the conditions for zeolite layer formation for zeolite ZSM-5 and zeolite LTA. The synthesis of the zeolite ZSM-5 layer was performed using an electrophoretic deposition technique on alpha-alumina substrates. The effects of chemical composition and applied electrical potential were evaluated using SEM, gas permeation, and the Maxwell-Stefan model. The results show that the thickness of the layers is controlled by the synthesis concentration and electrical potential across two electrodes. This indicates that the surface charge has a strong influence on zeolite layer formation on a substrate. The evaluation of the zeolite layers was performed using gas permeation analysis and the modeling using the Maxwell-Stefan diffusion approach. This analysis reveals that small defects in less than 0.1% of the zeolite layer can give a difference of about two orders of magnitude between the membrane diffusivity and zeolite particle diffusivity, which resulted in the high gas permeation rates observed. The zeolite LTA framework is composed of an equal amount of silica and alumina arranged in a three-dimension tetrahedral structure. This high alumina content zeolite possesses a strong negative surface charge in a basic solution due to the substitution of aluminum atoms into a SiO4 tetrahedral structure making it difficult to form a continuous layer in solution. This study is conducted in order to understand the differences in the formation of the zeolite in a solution and on a surface. Synthesis parameters such as synthesis duration, chemical composition, and synthesis temperature were varied. The crystallization kinetics was carried out using the particle size measurement, percent crystallinity from XRD analysis, IR absorption of tetrahedra using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), and the exponential growth model. The relationship of the substrate variation to the zeolite layer quality was examined using SEM and gas permeation tests. The results show that the formation of the zeolite layer depends on the surface nucleation site, the mass transfer rate of the nutrient onto the surface, and the relative surface charge of the zeolite particles and substrates. The evaluation of the electrical double layer effect using the colloid particle interaction theory shows a strong repulsion between zeolite LTA particles and the substrates. Increasing the crystal size results in a stronger repulsion between particles, causing the particles to grow individually and precipitate out of the solution.

Oonkhanond, Bovornlak

80

Diagram of Zeolite Crystals  

NASA Technical Reports Server (NTRS)

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

2003-01-01

81

Pillared MFI zeolite nanosheets of a single-unit-cell thickness.  

PubMed

Zeolite MFI nanosheets of 2-nm thickness have been hydrothermally synthesized via cooperative assembly between silica and an organic surfactant, which is functionalized with a diquaternary ammonium group. The zeolite nanosheets have been further assembled into their ordered multilamellar mesostructure through hydrophobic interactions between the surfactant tails located outside the zeolite nanosheet. This assembly process involves successive transformations from an initially hexagonal mesophase to a multilamellar mesophase without crystallinity and then to a lamellar mesophase with a crystalline zeolite framework. The mesopore volume in the interlamellar space could be retained by supporting the zeolite nanosheets with silica pillars, as in pillared clays, even after surfactant removal by calcination. The mesopore diameters could be controlled according to the surfactant tail lengths. Due to the interlamellar structural coherence, the hierarchically mesoporous/microporous zeolite could exhibit small-angle X-ray diffraction peaks up to the fourth-order reflections corresponding to the interlayer distance. In addition, an Ar adsorption analysis and transmission electron microscopic investigation indicated that the pillars were highly likely to be built with an MFI structure. The present approach using a zeolite structure-directing functional group contained in a surfactant would be suitable for the synthesis of other related nanomorphous zeolites in the future. PMID:20136135

Na, Kyungsu; Choi, Minkee; Park, Woojin; Sakamoto, Yasuhiro; Terasaki, Osamu; Ryoo, Ryong

2010-03-31

82

Sustainable synthesis of zeolites without addition of both organotemplates and solvents.  

PubMed

The development of sustainable and environmentally friendly techniques for synthesizing zeolites has attracted much attention, as the use of organic templates and solvents in the hydrothermal synthesis of zeolites is a major obstacle for realizing green and sustainable synthesis ways. Recently, the introduction of the organotemplate-free synthesis method allowed avoiding the use of organic templates, but water as solvent was still required; solvent-free routes on the other hand beared the potential to significantly reduce the amount of polluted wastewater, but organic templates were still present. In this work, we have demonstrated a combined strategy of both organotemplate- and solvent-free conditions to synthesize aluminosilicate zeolites Beta and ZSM-5 (S-Beta and S-ZSM-5), two of the most important zeolites relevant for industry. The samples are thoroughly characterized by XRD patterns, SEM images, N2 sorption isotherms, UV-Raman spectra, and (29)Si and (27)Al MAS NMR spectra. The results demonstrate that S-Beta and S-ZSM-5 zeolites exhibit almost the same textural parameters (e.g., BET surface area and pore volume) and catalytic performance in cumene cracking and m-xylene isomerization as those of conventional Beta and ZSM-5 zeolites synthesized under hydrothermal conditions (C-Beta and C-ZSM-5). The organotemplate- and solvent-free syntheses of S-Beta and S-ZSM-5 take place at a low-pressure regime and are free of harmful gases as well as give high product yields together with highly efficient consumption of the starting raw materials. These advantages plus the very simple procedures opened the pathway to a highly sustainable zeolite synthesis protocol compared to conventional methods currently employed for C-Beta and C-ZSM-5. Very interestingly, this simple synthesis is a good model for understanding zeolite crystallization. The detail characterizations indicate that the S-Beta crystals are formed from the assembly of zeolite building units, mainly 4MRs, while the 5MRs in the framework are just formed in the crystallization of S-ZSM-5, rather than existence in the starting solid mixture. During the crystallization processes, small traces of water play an important role for the hydrolysis and condensation of silica and/or aluminosilicate species. PMID:24552214

Wu, Qinming; Wang, Xiong; Qi, Guodong; Guo, Qiang; Pan, Shuxiang; Meng, Xiangju; Xu, Jun; Deng, Feng; Fan, Fengtao; Feng, Zhaochi; Li, Can; Maurer, Stefan; Mller, Ulrich; Xiao, Feng-Shou

2014-03-12

83

Hierarchical zeolites from class F coal fly ash  

NASA Astrophysics Data System (ADS)

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.

Chitta, Pallavi

84

Composite zeolite membranes  

DOEpatents

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.

Nenoff, Tina M. (Albuquerque, NM); Thoma, Steven G. (Albuquerque, NM); Ashley, Carol S. (Albuquerque, NM); Reed, Scott T. (Albuquerque, NM)

2002-01-01

85

ZEOLITE CHARACTERIZATION TESTING  

SciTech Connect

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.

Jacobs, W; Herbert Nigg, H

2007-09-13

86

Analysis of the Biological and Chemical Reactivity of Zeolite-Based Aluminosilicate Fibers and Particulates  

Microsoft Academic Search

Environmental and\\/or occupational exposure to minerals, metals, and fibers can cause lung dis- eases that may develop years after exposure to the agents. The presence of toxic fibers such as asbestos in the environment plus the continuing development of new mineral or vitreous fibers requires a better understanding of the specific physical and chemical features of fibers\\/particles responsible for bioactivity.

Estelle Fach; W. James Waldman; Marshall Williams; John Long; Richard K. Meister; Prabir K. Dutta

2002-01-01

87

The roles of entropy and enthalpy in stabilizing ion-pairs at transition states in zeolite acid catalysis.  

PubMed

Acidic zeolites are indispensable catalysts in the petrochemical industry because they select reactants and their chemical pathways based on size and shape. Voids of molecular dimensions confine reactive intermediates and transition states that mediate chemical reactions, stabilizing them by van der Waals interactions. This behavior is reminiscent of the solvation effects prevalent within enzyme pockets and has analogous consequences for catalytic specificity. Voids provide the "right fit" for certain transition states, reflected in their lower free energies, thus extending the catalytic diversity of zeolites well beyond simple size discrimination. This catalytic diversity is even more remarkable because acid strength is essentially unaffected by confinement among known crystalline aluminosilicates. In this Account, we discuss factors that determine the "right fit" for a specific chemical reaction, exploring predictive criteria that extend the prevailing discourse based on size and shape. We link the structures of reactants, transition states, and confining voids to chemical reactivity and selectivity. Confinement mediates enthalpy-entropy compromises that determine the Gibbs free energies of transition states and relevant reactants; these activation free energies determine turnover rates via transition state theory. At low temperatures (400-500 K), dimethyl ether carbonylation occurs with high specificity within small eight-membered ring (8-MR) voids in FER and MOR zeolite structures, but at undetectable rates within larger voids (MFI, BEA, FAU, and SiO(2)-Al(2)O(3)). More effective van der Waals stabilization within 8-MR voids leads to lower ion-pair enthalpies but also lower entropies; taken together, carbonylation activation free energies are lower within 8-MR voids. The "right fit" is a "tight fit" at low temperatures, a consequence of how temperature appears in the defining equation for Gibbs free energy. In contrast, entropy effects dominate in high-temperature alkane activation (700-800 K), for which the "right fit" becomes a "loose fit". Alkane activation turnovers are still faster on 8-MR MOR protons because these transition states are confined only partially within shallow 8-MR pockets; they retain higher entropies than ion-pairs fully confined within 12-MR channels at the expense of enthalpic stability. Selectivities for n-alkane dehydrogenation (relative to cracking) and isoalkane cracking (relative to dehydrogenation) are higher on 8-MR than 12-MR sites because partial confinement preferentially stabilizes looser ion-pair structures; these structures occur later along reaction coordinates and are higher in energy, consistent with Marcus theory for charge-transfer reactions. Enthalpy differences between cracking and dehydrogenation ion-pairs for a given reactant are independent of zeolite structure (FAU, FER, MFI, or MOR) and predominantly reflect the different gas-phase proton affinities of alkane C-C and C-H bonds, as expected from Born-Haber thermochemical cycles. These thermochemical relations, together with statistical mechanics-based treatments, predict that rotational entropy differences between intact reactants and ion-pair transition states cause intrinsic cracking rates to increase with n-alkane size. Through these illustrative examples, we highlight the effects of reactant and catalyst structures on ion-pair transition state enthalpies and entropies. Our discussion underscores the role of temperature in mediating enthalpic and entropic contributions to free energies and, in turn, to rates and selectivities in zeolite acid catalysis. PMID:21870839

Gounder, Rajamani; Iglesia, Enrique

2012-02-21

88

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

SciTech Connect

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.

Conrad Ingram; Mark Mitchell

2004-06-30

89

Sorption effects in zeolite catalysis  

SciTech Connect

Catalysis by zeolites and other microcrystalline materials is characterized by an unusually high degree of fundamental understanding. In acid catalysis, the active sites are part of the zeolite structure, not surface defects, and their nature and number can often be accurately determined. The dynamics of adsorption and desorption of reactant and product molecules, i.e. diffusion in zeolites, has also been extensively studied. Much less emphasis has been placed on a quantitative understanding of thermodynamic equilibrium sorption phenomena in zeolite catalyzed reactions. This talk will briefly discuss the principles and experimental data for hydrocarbon sorption in a variety of zeolites. It will then describe the application of these principles to a variety of zeolite catalyzed reactions. These include rate enhancements by non-acidic zeolites in thermal Diels-Alder reactions and paraffin cracking, the effect of carbon number and of zeolite structure on the observed activation energy of catalytic cracking, and the observation of very strong rate inhibition in ethylbenzene disproportionation.

Haag, W.O.

1996-10-01

90

Preparation of functionalized zeolitic frameworks  

DOEpatents

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.

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

2012-11-20

91

Preparation of functionalized zeolitic frameworks  

DOEpatents

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.

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

2013-07-09

92

Aluminosilicate and aluminosilicate based polymer composites: Present status, applications and future trends  

NASA Astrophysics Data System (ADS)

Aluminosilicates have traditionally been important materials for applications related to adsorbents, water softeners, catalysis and mechanical and thermal reinforcement due to their high surface area, excellent thermal/hydrothermal stability, high shape-selectivity and superior ion-exchange ability. Recently, their use as polymer fillers has allowed to increasingly extending their application range to innovative areas such as medical and biological fields as well as in sensors, filtration membranes, energy storage and novel catalysis routes. Further, the large versatility and tailoring possibilities of both filler and matrix indicates this area as one of the enabling key technologies of the near future. This work summarizes the main developments up to date in this increasingly interesting field, focuses on the main applications already developed as well as on the key challenges for the near future.

Lopes, A. C.; Martins, P.; Lanceros-Mendez, S.

2014-08-01

93

NMR investigations of tetrapropylammonium aluminosilicate and borosilicate solutions  

SciTech Connect

{sup 29}Si, {sup 27}Al, and {sup 11}B NMR spectroscopies were used to characterize dilute, highly alkaline tetrapropylammonium (TPA) aluminosilicate and borosilicate solutions. The compositions of the solutions range from 0.1 to 2 mol % SiO{sub 2}, silicate ratios (R = (SiO{sub 2})/(M{sub 2}O); M{sup +} = TPA{sup +}) from 0.1 to 2, and Si/Al or Si/B molar ratios from 0.25 to 10. {sup 29}Si and {sup 27}Al NMR spectra provide evidence for the formation of aluminosilicate anions. Si is observed with Q{sub 1}(A1Al), Q{sub 2{minus}Delta}(1Al), Q{sub 2}(1Al) + Q{sub 3{Delta}}(1Al), and Q{sub 3}(1Al) connectivity. Several new {sup 29}Si NMR peaks are assigned to specific aluminosilicate anions based on chemical shifts. {sup 27}Al NMR spectra of aluminosilicate solutions reveal peaks corresponding to Al bound to zero, one, two, and three siloxane bonds. The distribution of aluminosilicate anions is affected by the concentration of dissolved Si and Al, as well as the solution pH. The distribution of aluminosilicate species is described in terms of simple chemical equilibria. {sup 29}Si and {sup 11}B NMR spectra of borosilicate solutions indicate that borate anions are less reactive than aluminate anions. {sup 11}B NMR spectra reveal only a small fraction of the dissolved B appears to form borosilicates.

Mortlock, R.F.; Bell, A.T.; Radke, C.J. (Univ. of California, Berkeley (USA))

1991-01-10

94

Photodarkening in Yb-doped aluminosilicate fibers induced by 488 nm irradiation  

Microsoft Academic Search

Photodarkening of Yb-doped aluminosilicate fibers by continuous wave 488nm irradiation was investigated. The irradiation induced significant excess loss in the UV-visible spectroscopy (VIS) region in Yb-doped aluminosilicate fibers while pure aluminosilicate fibers showed negligible induced loss. Ultraviolet-VIS-near-infrared spectroscopy revealed an absorption peak at 220nm in unexposed Yb-doped aluminosilicate fiber preforms. The observed peak was attributed to Yb-associated oxygen deficiency centers

S. Yoo; C. Basu; A. J. Boyland; C. Sones; J. Nilsson; J. K. Sahu; D. Payne

2007-01-01

95

Aluminum27 NMR Investigations of Aqueous and Methanolic Aluminosilicate Solutions  

Microsoft Academic Search

Aluminum-27 NMR spectroscopy was used to characterize aqueous and methanolic alkaline solutions of tetramethylammonium (TMA) aluminosilicates. Aluminosilicate solutions have been prepared with different concentrations of silicon [0.5771.24% (w\\/w)], aluminum [0.00220.239% (w\\/w)], methanol [0.00.70% (w\\/w)] and H2O [0.2390% (w\\/w)]. All solutions contain the same ratio of Si\\/TMA = 1 and Si\\/Al molar ratios between 0.5 and 25.27Al NMR spectra of TMA

Abdolraouf Samadi-Maybodi; Nasser Goudarzi; Hamidreza Bijanzadeh

2005-01-01

96

Synthesis and characterization of activated carbo-aluminosilicate material from oil shale  

E-print Network

Synthesis and characterization of activated carbo-aluminosilicate material from oil shale Reyad activated carbo-aluminosilicate materials were prepared from oil shale by chemical activation. The chemical Published by Elsevier Inc. Keywords: Synthesis; Activated carbo-aluminosilicate; Adsorption; Oil shale

Shawabkeh, Reyad A.

97

ZSM-5 zeolite nanosheets with improved catalytic activity synthesized using a new class of structure-directing agents.  

PubMed

A new series of multiquaternary ammonium structure-directing agents, based on 1,4-diazabicyclo[2.2.2]octane, was prepared. ZSM-5 zeolites with nanosheet morphology (10?nm crystal thickness) were synthesized under hydrothermal conditions using multiquaternary ammonium surfactants as the zeolite structure-generating agents. Both wide-angle and small-angle diffraction patterns were obtained using only a suitable structure-directing agent under a specific zeolite synthesis composition. A mechanism of zeolite formation is proposed based on the results obtained from various physicochemical characterizations. ZSM-5 materials were investigated in catalytic reactions requiring medium to strong acidity, which are important for the synthesis of a wide range of industrially important fine and specialty chemicals. The catalytic activity of ZSM-5 materials was compared with that of the conventional ZSM-5 and amorphous mesoporous aluminosilicate Al-MCM-41. The synthesis strategy of the present investigation using the new series of structure-directing agents could be extended for the synthesis of other related zeolites or other porous materials in the future. Zeolite with a structural feature as small as the size of a unit cell (5-10?nm) with hierarchically ordered porous structure would be very promising for catalysis. PMID:25056112

Kore, Rajkumar; Srivastava, Rajendra; Satpati, Biswarup

2014-09-01

98

The influence of using Jordanian natural zeolite on the adsorption, physical, and mechanical properties of geopolymers products.  

PubMed

Geopolymers consist of an amorphous, three-dimensional structure resulting from the polymerization of aluminosilicate monomers that result from dissolution of kaolin in an alkaline solution at temperatures around 80 degrees C. One potential use of geopolymers is as Portland cement replacement. It will be of great importance to provide a geopolymer with suitable mechanical properties for the purpose of water storage and high adsorption capacity towards pollutants. The aim of this work is to investigate the effect of using Jordanian zeolitic tuff as filler on the mechanical performance and on the adsorption capacity of the geopolymers products. Jordanian zeolitic tuff is inexpensive and is known to have high adsorption capacity. The results confirmed that this natural zeolitic tuff can be used as a filler of stable geopolymers with high mechanical properties and high adsorption capacity towards methylene blue and Cu(II) ions. The XRD measurements showed that the phillipsite peaks (major mineral constituent of Jordanian zeolite) were disappeared upon geopolymerization. The zeolite-based geopolymers revealed high compressive strength compared to reference geopolymers that employ sand as filler. Adsorption experiments showed that among different geopolymers prepared, the zeolite-based geopolymers have the highest adsorption capacity towards methylene blue and copper(II) ions. PMID:19036505

Yousef, Rushdi Ibrahim; El-Eswed, Bassam; Alshaaer, Mazen; Khalili, Fawwaz; Khoury, Hani

2009-06-15

99

Heterostructured layered aluminosilicate-itraconazole nanohybrid for drug delivery system.  

PubMed

A nanohybrid, consisting of layered aluminosilicate as a host material and itraconazole as a guest molecule, was successfully synthesized through the interfacial intercalation reaction across the boundary between water and water-immiscible liquid at the various pH. According to the powder X-ray diffraction pattern, the basal spacing of the intraconazole-layered aluminosilicate nanohybrid increased from 14.7 to 22.7 A depending on the pH of the aqueous suspension. The total amounts of itraconazole in the hybrids were determined to be 2.3-25.4 wt% by HPLC analysis. The in vivo pharmacokinetics study was performed in rats in order to compare the absorptions of itraconazole for the itraconazole-layered aluminosilicate nanohybrid and a commercial product, Sporanox. The pharmacokinetic data for the nanohybrid and Sporanox showed that the mean area under the plasma concentration-time curve (AUC, 2477 +/- 898 ng x hr/mL and 2630 +/- 953 ng x hr/mL, respectively) and maximum concentration (Cmax, 225.4 +/- 77.4 ng x hr/mL and 223.6 +/- 51.9 ng x hr/mL, respectively), were within the bioequivalence (BE) range. Therefore, we concluded that this drug-layered aluminosilicate nanohybrid system has a great potential for its application in formulation of poorly soluble drugs. PMID:24245252

Yang, Jae-Hun; Jung, Hyun; Kim, Su Yeon; Yo, Chul Hyun; Choy, Jin-Ho

2013-11-01

100

Al Coordination Changes in High-Pressure Aluminosilicate Liquids  

Microsoft Academic Search

Understanding the effect of pressure on aluminosilicate glass and liquid structure is critical to understanding magma flow at depth. Aluminum coordination has been predicted by mineral phase analysis and molecular dynamic calculations to change with increasing pressure. Nuclear magnetic resonance studies of glasses quenched from high pressure provide clear evidence for an increase in the average coordination of Al with

J. L. Yarger; K. H. Smith; R. A. Nieman; J. Diefenbacher; G. H. Wolf; B. T. Poe; P. F. McMillan

1995-01-01

101

A high acid mesoporous USY zeolite prepared by alumination  

NASA Astrophysics Data System (ADS)

A high-acidity HUSY zeolite with mesoporous structure was prepared by alumination with a dilute aqueous NaAlO2 solution and characterized by XRD, N2 adsorption, IR framework vibration and 29Si MAS NMR methods. The results indicated the extra-framework aluminum was reinserted into the tetrahedral framework through isomorphic substitution of framework Si (0Al) sites by Al ions, whereas the crystal and micropore structure were unaltered. FTIR spectra of hydroxyl vibrations and pyridine adsorbed on realuminated zeolites showed that the number of Brnsted acid sites and strong Lewis acid sites increased whereas weak Lewis acid sites decreased twice. The mesoporous structure composed of inter-and intra-crystalline pores in the aluminated HUSY increased the external surface area of the zeolite, improving accessibility of molecules to the active sites and enhancing its catalytic ability. The realuminated HUSY zeolite supported with Ru catalyst exhibited a higher catalytic activity for benzene hydrogenation than the parent HUSY zeolite; the reaction rate in comparison to the mesozeolite increased by 5.5 times.

Ma, Jinghong; Kang, Yuhong; Ma, Ning; Hao, Wenming; Wang, Yan; Li, Ruifeng

2013-01-01

102

Removal of zinc, copper and lead by natural zeolite-a comparison of adsorption isotherms.  

PubMed

An uptake of zinc (Zn), copper (Cu), and lead (Pb) from aqueous solutions by ion exchange on natural zeolitic tuff has been studied. The Croatian zeolite clinoptilolite from the Donje Jesenje deposit has been used as a natural ion exchanger. The efficiency of removal is higher for Pb and Cu than for Zn ions. Measured concentrations of Si in the liquid phase identify the detachment of the aluminosilicate structure during ion exchange in the presence of H(+) and OH(-) ions. The adsorption isotherm equations; Langmuir-Freundlich, Redlich-Petersen, Toth, Dubinin-Radushkevich, modified Dubinin-Radushkevich, and Lineweawer-Burk were derived from the basic empirical equations, and used for calculation of ion exchange parameters. The best fitting of experimental results to the proposed isotherms was observed in models that assume that ionic species bind first at energetically most favorable sites, with multi-layer adsorption taking place subsequently. PMID:15026244

Peri?, J; Trgo, M; Vukojevi? Medvidovi?, N

2004-04-01

103

Zeolite crystal growth in space  

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

104

Hard x-ray nanotomography of amorphous aluminosilicate cements.  

SciTech Connect

Nanotomographic reconstruction of a sample of low-CO{sub 2} 'geopolymer' cement provides the first three-dimensional view of the pore structure of the aluminosilicate geopolymer gel, as well as evidence for direct binding of geopolymer gel onto unreacted fly ash precursor particles. This is central to understanding and optimizing the durability of concretes made using this new class of binder, and demonstrates the value of nanotomography in providing a three-dimensional view of nanoporous inorganic materials.

Provis, J. L.; Rose, V.; Winarski, R. P.; van Deventer, J. S. J. (Advanced Photon Source); ( CNM)

2011-08-01

105

SO2 REMOVAL FROM FLUE GASES USING UTILITY SYNTHESIZED ZEOLITES  

SciTech Connect

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.

Michael Grutzeck

1999-04-30

106

SO2 REMOVAL FROM FLUE GASES USING UTILITY SYNTHESIZED ZEOLITES  

SciTech Connect

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.

MICHAEL GRUTZECK

1998-10-31

107

EMM-23: A Stable High-Silica Multidimensional Zeolite with Extra-Large Trilobe-Shaped Channels.  

PubMed

Stable, multidimensional, and extra-large pore zeolites are desirable by industry for catalysis and separation of bulky molecules. Here we report EMM-23, the first stable, three-dimensional extra-large pore aluminosilicate zeolite. The structure of EMM-23 was determined from submicron-sized crystals by combining electron crystallography, solid-state nuclear magnetic resonance (NMR), and powder X-ray diffraction. The framework contains highly unusual trilobe-shaped pores that are bound by 21-24 tetrahedral atoms. These extra-large pores are intersected perpendicularly by a two-dimensional 10-ring channel system. Unlike most ideal zeolite frameworks that have tetrahedral sites with four next-nearest tetrahedral neighbors (Q(4) species), this unusual zeolite possesses a high density of Q(2) and Q(3) silicon species. It is the first zeolite prepared directly with Q(2) species that are intrinsic to the framework. EMM-23 is stable after calcination at 540 C. The formation of this highly interrupted structure is facilitated by the high density of extra framework positive charge introduced by the dicationic structure directing agent. PMID:25198917

Willhammar, Tom; Burton, Allen W; Yun, Yifeng; Sun, Junliang; Afeworki, Mobae; Strohmaier, Karl G; Vroman, Hilda; Zou, Xiaodong

2014-10-01

108

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

PubMed

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

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

2008-11-01

109

NiPt\\/HY Zeolite Catalysts for Disproportionation of Toluene and 1,2,4-trimethylbenzene  

Microsoft Academic Search

NiPt\\/HY zeolite catalysts with different Ni contents were prepared and applied to the disproportionation of toluene and 1,2,4-trimethylbenzene in the temperature range 250400C. The line broadening XRD analysis indicates that the increasing Ni addition decreases the crystallinity of zeolites. ESCA studies show the complete reduction of Ni species up to 0.3 wt.% Ni addition over 0.1 wt.% Pt\\/H-Y and further

A. Geetha Bhavani; D. Karthekayen; A. Sreenivasa Rao; N. Lingappan

2005-01-01

110

Thermal behavior of natural zeolites  

SciTech Connect

Thermal behavior of natural zeolites impacts their application and identification and varies significantly from zeolite to zeolite. Zeolites evolve H{sub 2}0 upon heating, but recent data show that distinct ``types`` of water (e.g., loosely bound or tightly bound zeolitic water) do not exist. Rather water is bound primarily to extra-framework cations with a continuum of energies, giving rise to pseudocontinuous loss of water accompanied by a dynamic interaction between remaining H{sub 2}0 molecules and extra-framework cations. These interactions in the channels of zeolites give rise to dehydration dependent on the extra-framework cation, in addition to temperature and water vapor pressure. The dehydration reaction and the extra-framework cation also affect the thermal expansion/contraction. Most zeolites undergo dehydration-induced contractions that may be anisotropic, although minor thermal expansion can be seen with some zeolites. Such contractions can be partially or completely irreversible if they involve modifications of the tetrahedral framework and/or if rehydration is sluggish. Thermally induced structural modifications are also driven initially by dehydration and the concomitant contraction and migration of extra-framework cations. Contraction is accommodated by rotations of structural units and tetrahedral cation-oxygen linkages may break. Thermal reactions that involve breaking of tetrahedral cation-oxygen bonds markedly irreversible and may be kinetically limited, producing large differences between short- and long-term heating.

Bish, D.L.

1993-09-01

111

Zeolite formation from coal fly ash and its adsorption potential.  

PubMed

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

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

2009-10-01

112

Solid-state radioluminescent zeolite-containing composition and light sources  

DOEpatents

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.

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

113

Oxygen and hydrogen isotope geochemistry of zeolites  

NASA Technical Reports Server (NTRS)

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.

Karlsson, Haraldur R.; Clayton, Robert N.

1990-01-01

114

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

PubMed

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

Sprung, Christoph; Weckhuysen, Bert M

2014-03-24

115

Atomic Structure of a Cesium Aluminosilicate Geopolymer: A Pair Distribution Function Study  

SciTech Connect

The atomic pair distribution function (PDF) method was used to study the structure of cesium aluminosilicate geopolymer. The geopolymer was prepared by reacting metakaolin with cesium silicate solution followed by curing at 50C for 24 h in a sealed container. Heating of Cs-geopolymer above 1000C resulted in formation of crystalline pollucite (CsAlSi{sub 2}O{sub 6}). PDF refinement of the pollucite phase formed displayed an excellent fit over the 10-30 {angstrom} range when compared with a cubic pollucite model. A poorer fit was attained from 1-10 {angstrom} due to an additional amorphous phase present in the heated geopolymer. On the basis of PDF analysis, unheated Cs-geopolymer displayed structural ordering similar to pollucite up to a length scale of 9 {angstrom}, despite some differences. Our results suggest that hydrated Cs{sup +} ions were an integral part of the Cs-geopolymer structure and that most of the water present was not associated with Al-OH or Si-OH bonds.

Bell, J.; Sarin, P; Provis, J; Haggerty, R; Driemeyer, P; Chupas, P; van Deventer, J; Kriven, W

2008-01-01

116

Calcium-Magnesium-Aluminosilicate (CMAS) Reactions and Degradation Mechanisms of Advanced Environmental Barrier Coatings  

NASA Technical Reports Server (NTRS)

The thermochemical reactions between calcium-magnesium-aluminosilicate- (CMAS-) based road sand and several advanced turbine engine environmental barrier coating (EBC) materials were studied. The phase stability, reaction kinetics and degradation mechanisms of rare earth (RE)-silicates Yb2SiO5, Y2Si2O7, and RE-oxide doped HfO2 and ZrO2 under the CMAS infiltration condition at 1500 C were investigated, and the microstructure and phase characteristics of CMAS-EBC specimens were examined using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). Experimental results showed that the CMAS dissolved RE-silicates to form crystalline, highly non-stoichiometric apatite phases, and in particular attacking the silicate grain boundaries. Cross-section images show that the CMAS reacted with specimens and deeply penetrated into the EBC grain boundaries and formed extensive low-melting eutectic phases, causing grain boundary recession with increasing testing time in the silicate materials. The preliminary results also showed that CMAS reactions also formed low melting grain boundary phases in the higher concentration RE-oxide doped HfO2 systems. The effect of the test temperature on CMAS reactions of the EBC materials will also be discussed. The faster diffusion exhibited by apatite and RE-doped oxide phases and the formation of extensive grain boundary low-melting phases may limit the CMAS resistance of some of the environmental barrier coatings at high temperatures.

Ahlborg, Nadia L.; Zhu, Dongming

2013-01-01

117

The synthesis of zeolites from fly ash and the properties of the zeolite products  

Microsoft Academic Search

Fly ash produced during the combustion of powdered coal could be converted up to 45% into zeolite. By varying the experimental conditions different types of zeolite were produced, e.g. zeolite Na-P1, zeolite K-G and zeolite ZK19. By this zeolitization process the cation exchange capacity (CEC) was raised from 0.02 to circa 2.4 meq\\/g. Anionic heavy metals were largely extracted by

G Steenbruggen; G. G Hollman

1998-01-01

118

NMR investigations of tetrapropylammonium aluminosilicate and borosilicate solutions  

Microsoft Academic Search

²⁹Si, ²⁷Al, and ¹¹B NMR spectroscopies were used to characterize dilute, highly alkaline tetrapropylammonium (TPA) aluminosilicate and borosilicate solutions. The compositions of the solutions range from 0.1 to 2 mol % SiO, silicate ratios (R = (SiO)\\/(MO); M{sup +} = TPA{sup +}) from 0.1 to 2, and Si\\/Al or Si\\/B molar ratios from 0.25 to 10. ²⁹Si and ²⁷Al NMR

R. F. Mortlock; Alexis T. Bell; C. J. Radke

1991-01-01

119

Characterisation of frequency doubling in Eu(2+) doped aluminosilicate fibres  

NASA Technical Reports Server (NTRS)

The results of a series of experiments on efficient second-harmonic generation in a fiber with a Eu(2+)-doped aluminosilicate core are reported. The fiber was prepared by the seeding method with CW mode-locked radiation at 1.06 micron and produced ultrastable peak conversion efficiencies of 0.001 during mode-locked readout. Experiments were performed to determine the IR preparation intensity dependence, the stability of the output, and the type of erasure mechanisms which occur. The results are compared with those of germanosilicate fibers and some similarities and differences are discussed.

Driscoll, T. J.; Lawandy, N. M.; Killian, A.; Rienhart, L.; Morse, T. F.

1991-01-01

120

Structure-Property Relationships of Inorganically Surface-Modified Zeolite Molecular Sieves for Nanocomposite Membrane Fabrication  

SciTech Connect

A multiscale experimental study of the structural, compositional, and morphological characteristics of aluminosilicate (LTA) and pure-silica (MFI) zeolite materials surface-modified with MgO{sub x}H{sub y} nanostructures is presented. These characteristics are correlated with the suitability of such materials in the fabrication of LTA/Matrimid mixed-matrix membranes (MMMs) for CO{sub 2}/CH{sub 4} separations. The four functionalization methods studied in this work produce surface nanostructures that may appear superficially similar under SEM observation but in fact differ considerably in shape, size, surface coverage, surface area/roughness, degree of attachment to the zeolite surface, and degree of zeolite pore blocking. The evaluation of these characteristics by a combination of TEM, HRTEM, N{sub 2} physisorption, multiscale compositional analysis (XPS, EDX, and ICP-AES elemental analysis), and diffraction (ED and XRD) allows improved understanding of the origin of disparate gas permeation properties observed in MMMs made with four types of surface-modified zeolite LTA materials, as well as a rational selection of the method expected to result in the best enhancement of the desired properties (in the present case, CO{sub 2}/CH{sub 4} selectivity increase without sacrificing permeability). A method based on ion exchange of the LTA with Mg{sup 2+}, followed by base-induced precipitation and growth of MgOxHy nanostructures, deemed 'ion exchange functionalization' here, offers modified particles with the best overall characteristics resulting in the most effective MMMs. LTA/Matrimid MMMs containing ion exchange functionalized particles had a considerably higher CO{sub 2}/CH{sub 4} selectivity (40) than could be obtained with the other functionalization techniques (30), while maintaining a CO{sub 2} permeability of 10 barrers. A parallel study on pure silica MFI surface nanostructures is also presented to compare and contrast with the zeolite LTA case.

Lydon, Megan E [Georgia Institute of Technology; Unocic, Kinga A [ORNL; Jones, Christopher W [Georgia Institute of Technology; Nair, Sankar [Georgia Institute of Technology

2012-01-01

121

Enhancing nitrification at low temperature with zeolite in a mining operations retention pond.  

PubMed

Ammonium nitrate explosives are used in mining operations at Diavik Diamond Mines Inc. in the Northwest Territories, Canada. Residual nitrogen is washed into the mine pit and piped to a nearby retention pond where its removal is accomplished by microbial activity prior to a final water treatment step and release into the sub-Arctic lake, Lac de Gras. Microbial removal of ammonium in the retention pond is rapid during the brief ice-free summer, but often slows under ice cover that persists up to 9?months of the year. The aluminosilicate mineral zeolite was tested as an additive to retention pond water to increase rates of ammonium removal at 4C. Water samples were collected across the length of the retention pond monthly over a year. The structure of the microbial community (bacteria, archaea, and eukarya), as determined by denaturing gradient gel electrophoresis of PCR-amplified small subunit ribosomal RNA genes, was more stable during cold months than during July-September, when there was a marked phytoplankton bloom. Of the ammonia-oxidizing community, only bacterial amoA genes were consistently detected. Zeolite (10?g) was added to retention pond water (100?mL) amended with 5?mM ammonium and incubated at 12C to encourage development of a nitrifying biofilm. The biofilm community was composed of different amoA phylotypes from those identified in gene clone libraries of native water samples. Zeolite biofilm was added to fresh water samples collected at different times of the year, resulting in a significant increase in laboratory measurements of potential nitrification activity at 4C. A significant positive correlation between the amount of zeolite biofilm and potential nitrification activity was observed; rates were unaffected in incubations containing 1-20?mM ammonium. Addition of zeolite to retention ponds in cold environments could effectively increase nitrification rates year-round by concentrating active nitrifying biomass. PMID:22866052

Miazga-Rodriguez, Misha; Han, Sukkyun; Yakiwchuk, Brian; Wei, Kai; English, Colleen; Bourn, Steven; Bohnert, Seth; Stein, Lisa Y

2012-01-01

122

Zeolites as solid solvents 1 Paper presented at the International Symposium `Organic Chemistry and Catalysis' on the occasion of the 65th birthday of Prof. H. van Bekkum, Delft, Netherlands, 23 October 1997. 1  

Microsoft Academic Search

In addition to their natural appeal as crystalline solids possessing a void intracrystalline volume consisting of channels and cages, sometimes interconnected, zeolites also have remarkable features resulting from the surface curvature of their internal surface. These features involve non-covalent interactions between the framework of the zeolite and molecules adsorbed in their intracrystalline free space. These interactions extend beyond the molecular

Eric G. Derouane

1998-01-01

123

RESULTS OF CAUSTIC DISSOLUTION OF ALUMINOSILICATE SCALE AND CHARACTERIZATION DATA FOR SAMPLES FROM THE EVAPORATOR POT AND GRAVITY DRAIN LINE  

SciTech Connect

The build-up of sodium aluminosilicate scale in the 2H Evaporator system continues to cause operational difficulties. The use of a nitric acid cleaning operation proved successful in 2001. However, the operation required additional facilities to support spent cleaning solution neutralization and was quite costly. A proposed caustic cleaning flowsheet has many advantages over the acid flowsheet. Therefore, samples were retrieved from the evaporator system (gravity drain line and pot) for both chemical and radiological characterization and dissolution testing. The characterization of these scale samples showed the presence of nitrated cancrinite along with a dehydrated zeolite. Small amounts of depleted uranium were also found in these samples as expected and the amount of uranium ranged from 0.5 wt% to 2 wt%. Dissolution in sodium hydroxide solutions of various caustic concentrations showed that the scale slowly dissolves at elevated temperature (90 C). Data from similar testing indicate that the scale removed from the GDL in 2005 dissolves slower than that removed in 1997. Differences in the particle size of these samples of scale may well explain the measured dissolution rate differences.

Wilmarth, B; Rita Sullivan, R; Chris Martino, C

2006-08-21

124

Preliminary study of natural zeolite as catalyst for decreasing the viscosity of heavy oil  

NASA Astrophysics Data System (ADS)

Natural zeolite such as heulandite and clipnotilolite are found in abundant quantities in many regions in the world, particularly in Indonesia. The catalytic ability of natural zeolites were investigated in aquathermolysis in order to decreasing the viscosity of heavy oil. Prior to test the ability, a milling treatment of natural zeolite was carried out on variation of time 4, 6 and 8 hrs and subsequently followed by activation with a simple heating at 300C. The physical and chemical properties of zeolites before and after of milling as well as the activation were characterized using XRD, SEM and EDS. XRD results indicated the decreasing crystallinity of the treated zeolite. SEM results showed that the particle size was from 0.5 to 2 ?m, indicating the reducing of particle size after the treatment. The catalytic test showed that the addition of natural zeolite (0.5 wt.%) on the mixed of heavy oil and water in an autoclave at temperature 200C during 6 hrs can reduce the viscosity of heavy oil up to 65%.

Merissa, Shanti; Fitriani, Pipit; Iskandar, Ferry; Abdullah, Mikrajuddin; Khairurrijal

2013-09-01

125

Hierarchical hybrid organic-inorganic materials with tunable textural properties obtained using zeolitic-layered precursor.  

PubMed

Novel layered zeolitic organic-inorganic materials have been synthesized using a two-dimensional zeolite precursor IPC-1P prepared by a top-down approach from zeolite UTL. The formation of porous materials containing organic linkers or polyhedral oligomeric siloxane covalently bonded to zeolite layers in the interlayer space was confirmed by a variety of characterization techniques (N2/Ar sorption analysis, XRD, (29)Si and (13)C NMR, TEM). The organic-inorganic porous hybrids obtained by intercalation with silsesquioxane posessed layered morphology and contained large crystalline domains. The hybrids exhibited mesoporous or hierarchical micro-/mesoporous systems, stable up to 350 C. Textural properties of the formed zeolitic organic-inorganic materials can be controlled by varying the linker or synthetic conditions over a broad range. Surface areas and pore volumes of synthesized hybrids significantly exceed those for parent zeolite UTL and corresponding swollen material; the amount of micropores increased with increasing rigidity and size of the organic linker in the order biphenyl > phenylene > ethanediyl. PMID:24451039

Opanasenko, Maksym; Parker, Wallace O'Neil; Shamzhy, Mariya; Montanari, Erica; Bellettato, Michela; Mazur, Michal; Millini, Roberto; ?ejka, Ji?

2014-02-12

126

Catalytic performance of Metal-Organic-Frameworks vs. extra-large pore zeolite UTL in condensation reactions  

PubMed Central

Catalytic behavior of isomorphously substituted B-, Al-, Ga-, and Fe-containing extra-large pore UTL zeolites was investigated in Knoevenagel condensation involving aldehydes, Pechmann condensation of 1-naphthol with ethylacetoacetate, and Prins reaction of ?-pinene with formaldehyde and compared with large-pore aluminosilicate zeolite beta and representative Metal-Organic-Frameworks Cu3(BTC)2 and Fe(BTC). The yield of the target product over the investigated catalysts in Knoevenagel condensation increases in the following sequence: (Al)beta < (Al)UTL < (Ga)UTL < (Fe)UTL < Fe(BTC) < (B)UTL < Cu3(BTC)2 being mainly related to the improving selectivity with decreasing strength of active sites of the individual catalysts. The catalytic performance of Fe(BTC), containing the highest concentration of Lewis acid sites of the appropriate strength is superior over large-pore zeolite (Al)beta and B-, Al-, Ga-, Fe-substituted extra-large pore zeolites UTL in Prins reaction of ?-pinene with formaldehyde and Pechmann condensation of 1-naphthol with ethylacetoacetate. PMID:24790940

Shamzhy, Mariya; Opanasenko, Maksym; Shvets, Oleksiy; Cejka, Jiri

2013-01-01

127

Copper-containing zeolite catalysts  

DOEpatents

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.

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

1996-01-01

128

Copper-containing zeolite catalysts  

DOEpatents

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.

Price, G.L.; Kanazirev, V.

1996-12-10

129

Synthesis and structure determination of the hierarchical meso-microporous zeolite ITQ-43.  

PubMed

The formation of mesopores in microporous zeolites is generally performed by postsynthesis acid, basic, and steam treatments. The hierarchical pore systems thus formed allow better adsorption, diffusion, and reactivity of these materials. By combining organic and inorganic structure-directing agents and high-throughput methodologies, we were able to synthesize a zeolite with a hierarchical system of micropores and mesopores, with channel openings delimited by 28 tetrahedral atoms. Its complex crystalline structure was solved with the use of automated diffraction tomography. PMID:21868673

Jiang, Jiuxing; Jorda, Jose L; Yu, Jihong; Baumes, Laurent A; Mugnaioli, Enrico; Diaz-Cabanas, Maria J; Kolb, Ute; Corma, Avelino

2011-08-26

130

Dynamic Reduction of FeO-Bearing, Anhydrous Aluminosilicate Melts  

NASA Astrophysics Data System (ADS)

We have studied the reduction dynamics of FeO-bearing aluminosilicate melts at oxygen activities sufficiently low to form metallic iron. The experiments involved reacting droplets, suspended from refractory metal wires, with a high-temperature ( 1400oC), controlled-oxygen-activity environment maintained by a dynamic CO:CO2 buffer. In the case of an FeO-doped magnesium aluminosilicate ("Fe-MAS") melt ( 5 mol% FeO) exposed to an oxygen activity of 2x10-13 ("QIF-2"; CO:CO2=240:1), the reduction dynamic is rate-limited by chemical diffusion of Mg2+: oxygen chemically ablates from the free surface and the network-modifying cations diffuse inward, charge-compensated by a counterflux of electron holes (the "semiconductor condition" holds for diffusion dynamics in this melt [e.g., Cook and Cooper, 2000]); nm-scale crystals of pure ? -Fe nucleate at an internal front. Diffusion of an oxygen species is not involved. In the case of FeO-doped calcium-magnesium aluminosilicate (Fe-CMAS) melt ( 8 mol% FeO) exposed to an oxygen activity of 2x10-15 (QIF-4; CO:CO2=1750:1), the dynamic changes: molten Fe-C-Si alloy droplets form near the surface, and bubbles are seen to form internally, truncating at an internal front. Further, the reaction occurs more slowly than that seen for the similarly polymerized Fe-MAS melt. The results suggests that molecular CO diffuses inward, consuming electron holes so as to form carbonate ion species in the melt [cf. Brooker et al., 2001]. Quenching produces a driving potential to reverse the internal reduction reaction, so creating the bubbles. Consumption of the electron holes by reaction with the carbon species dramatically reduces the reduction-to-metal kinetics. Brooker RA, Kohn SC, Holloway JR, McMillan PF (2001) Chem Geol 174:241-254; Cook GB, Cooper RF (2000) Am Mineral 85:397-406

Everman, R. L.; Cooper, R. F.

2004-12-01

131

Amphiphilic properties of poly(oxyalkylene)amine-intercalated smectite aluminosilicates.  

PubMed

Layered aluminosilicates, including synthetic fluorine mica and natural montmorillonite (MMT), were intercalated with poly(oxypropylene)-polyamine quaternary salts with a 230-5000 molecular weight range. The X-ray basal spacing of these silicates had been expanded from 13.5 to 83.7 A for the synthetic mica and to 92.0 A for MMT. The relative silicate dimensions (300-1000 nm for synthetic mica and 80-100 nm for MMT) were ascertained by direct TEM observations in the case of the co-intercalated synthetic mica and MMT mixtures with Mw = 2000 quaternary ammonium salts. The tailored organic incorporation of synthetic mica and MMT clays could alter these hydrophilic clays, making them amphiphilic, and enable the lowering of toluene/water interfacial tension to 2.0 mN/m at the critical concentration of 0.1 wt %. PMID:15969426

Lin, Jiang-Jen; Chen, Yu-Min

2004-05-11

132

Development of aluminosilicate polyelectrolytes for solid-state battery applications  

Microsoft Academic Search

We have synthesized and characterized a range of novel polyelectrolytes containing weakly basic aluminosilicate anions in the polymer backbone in order to achieve t+ = 1 and high ionic mobility. Room-temperature conductivity is observed to increase in the series: (NaAl(OEOMe)2)(((OE)xO)2\\/2)n < (NaAl(OR)2(OSiMe2(CH2) 3(OE)xO(CH2)SiMe2O)2\\/2)n < (NaAl(OSiR3) (OSiMe2(CH2)3(OE) xO(CH2)3SiMe2O)3\\/2)n. This trend is ascribed to reduced ion pairing due to decreasing anion basicity,

G. C. Rawsky; K. J. Henretta; R. Lowrey; D. F. Shriver; S. Vaynman

1995-01-01

133

Mixing of zeolite powders and molten salt  

Microsoft Academic Search

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

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

1996-01-01

134

Thermal behaviour of a zeolitic tuff  

Microsoft Academic Search

Natural zeolites undergo structural changes after heating which open their possible use in different fields, related to their chemical and physical properties, such as building stone, lightweight aggregate, ceramic foam, concrete bricks, tiles, porcelain stoneware and additive in puzzolonic cements. In this study, thermal behavior of zeolitic tuff quarried from Grdes-Manisa, region of Turkey was investigated. Zeolitic rocks were first

. a?lar Duvarc?; Y. Akdeniz; F. zm?h?; S. lk; D. Balkse; M. iftio?lu

2007-01-01

135

Interaction of phenol with NaX zeolite as studied by 1H MAS NMR, 29Si MAS NMR and 29Si CP MAS NMR spectroscopy  

Microsoft Academic Search

The interaction of phenol with zeolite NaX has been studied by 1H and 29Si MAS and 29Si-CP-MAS NMR spectroscopy. A large displacement of the chemical shift of hydroxyl protons from 1.2 ppm in the crystalline state to about 9 ppm occurs upon H-bonding of phenol to basic oxygen atoms of the zeolite. An enhancement of the 29Si-CP-MAS signal is observed

T Beutel; M.-J Peltre; B. L Su

2001-01-01

136

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

SciTech Connect

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.

Garrido Pedrosa, Anne M. [Federal University of Rio Grande do Norte, Department of Chemistry, CP 1692, 59078-970 Natal-RN (Brazil)]. E-mail: annemgp@yahoo.com; Souza, Marcelo J.B. [Federal University of Sergipe, Department of Chemical Engineering, 49100-000 Sao Cristovao-SE (Brazil); Melo, Dulce M.A. [Federal University of Rio Grande do Norte, Department of Chemistry, CP 1692, 59078-970 Natal-RN (Brazil); Araujo, Antonio S. [Federal University of Rio Grande do Norte, Department of Chemistry, CP 1692, 59078-970 Natal-RN (Brazil)

2006-06-15

137

Entrapping of Cs and Sr in heat-treated zeolite matrices  

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

138

An emulsion-based droplet hydrothermal synthesis method for the production of uniform sized zeolite nanocrystals.  

PubMed

A droplet based new hydrothermal synthesis method for nano-zeolite synthesis in bulk amount with uniform size, shape and morphology is presented. The proposed process addresses the limitation and shortcomings of droplet based microfluidic reactors and conventional hydrothermal methods. The process has been designed on the concept of mixing two immiscible solutions at high speed which then produces nano/submicron size droplets. Confinement within the droplet provides uniform heat transfer, enhanced mass transfer to growing crystal, chaotic advection within droplet facilitate rapid mixing, prevent the contact between growing crystals etc. Fine-tuned nano-cubic LTA zeolite crystals of size ?100 nm with uniform morphology and size distribution were prepared. Just within 4h of reaction time (aging+crystallization) well shaped cubic crystals with high crystallinity and size uniformity can be synthesized by the proposed synthesis process. Diffraction and electron microscopic studies reveal the high phase purity and size uniformity of as-synthesized LTA zeolite particles. PMID:24655827

Sharma, Pankaj; Han, Moon Hee; Cho, Churl Hee

2014-05-15

139

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

NASA Astrophysics Data System (ADS)

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.

Jeong, H. Y.; Lee, K.

2013-12-01

140

Effects of anions on local structure of Al and Si in aluminosilicates  

SciTech Connect

Three kinds of amorphous aluminosilicates were synthesized by coprecipitation of silicic acid with aluminum hydroxide in the presence of different inorganic ions: sulfate, chloride, and nitrate. Although the bulk composition of the aluminosilicates obtained was not affected by anion species, their DTA spectra were significantly different, suggesting that their structures also differ. The local structure of Al and Si in the aluminosilicates was studied in detail by {sup 27}Al and {sup 29}Si MAS NMR. From the {sup 27}Al MAS NMR spectra and comparison between {sup 29}Si HD- and CP-MAS NMR spectra, it was concluded that the aluminosilicate obtained in the presence of sulfate ions has only a montmorillonite-like structure, whereas in the cases of chloride and nitrate, the solids are composed of three phases: aluminum hydroxide, silica, and the montmorillonite-like aluminosilicate. The difference in the local structure of Al and Si in the aluminosilicates was explained by the difference in interaction between the anions and aluminum ions.

Miyazaki, Akane [Tokyo Inst. of Tech., Yokohama (Japan). Interdisciplinary Graduate School of Science and Engineering] [Tokyo Inst. of Tech., Yokohama (Japan). Interdisciplinary Graduate School of Science and Engineering; Yokoyama, Takushi [Kyushu Univ., Fukuoka (Japan). Dept. of Chemistry] [Kyushu Univ., Fukuoka (Japan). Dept. of Chemistry

1999-06-15

141

Structure-Directing Roles and Interactions of Fluoride and Organocations with Siliceous Zeolite Frameworks  

SciTech Connect

Interactions of fluoride anions and organocations with crystalline silicate frameworks are shown to depend subtly on the architectures of the organic species, which significantly influence the crystalline structures that result. One- and two-dimensional (2D) {sup 1}H, {sup 19}F, and {sup 29}Si nuclear magnetic resonance (NMR) spectroscopy measurements establish distinct intermolecular interactions among F{sup -} anions, imidazolium structure-directing agents (SDA{sup +}), and crystalline silicate frameworks for as-synthesized siliceous zeolites ITW and MTT. Different types and positions of hydrophobic alkyl ligands on the imidazolium SDA{sup +} species under otherwise identical zeolite synthesis compositions and conditions lead to significantly different interactions between the F{sup -} and SDA{sup +} ions and the respective silicate frameworks. For as-synthesized zeolite ITW, F{sup -} anions are established to reside in the double-four-ring (D4R) cages and interact strongly and selectively with D4R silicate framework sites, as manifested by their strong {sup 19}F{sup 29}Si dipolar couplings. By comparison, for as-synthesized zeolite MTT, F{sup -} anions reside within the 10-ring channels and interact relatively weakly with the silicate framework as ion pairs with the SDA{sup +} ions. Such differences manifest the importance of interactions between the imidazolium and F{sup -} ions, which account for their structure-directing influences on the topologies of the resulting silicate frameworks. Furthermore, 2D {sup 29}Si{l_brace}{sup 29}Si{r_brace} double-quantum NMR measurements establish {sup 29}Si-O-{sup 29}Si site connectivities within the as-synthesized zeolites ITW and MTT that, in conjunction with synchrotron X-ray diffraction analyses, establish insights on complicated order and disorder within their framework structures.

Shayib, Ramzy M.; George, Nathan C.; Seshadri, Ram; Burton, Allen W.; Zones, Stacey I.; Chmelka, Bradley F. (UCSB); (Chevron ETC)

2012-02-06

142

Exfoliated zeolite sheets and block copolymers as building blocks for composite membranes  

NASA Astrophysics Data System (ADS)

Mixed matrix materials, comprising of zeolites incorporated in suitable matrix (polymeric or inorganic), are promising as future membrane materials with high permselectivity. However, they suffer from the drawback of low productivity due to increase in the membrane thickness by incorporation of micron-sized zeolites crystals as well as the low-permeability matrices employed currently. Nanocomposite membranes, consisting of thin zeolite sheets (2 nm) embedded in an appropriate matrix, can provide a solution to this problem. This thesis addresses some of the material challenges to make such nanocomposite membranes. A high permeability polymer was synthesized by combining the glassy polystyrene (PS) with the rubbery polydimethylsiloxane (PDMS) in a block copolymer architecture. The mechanical toughness of the material was optimized to facilitate the fabrication of thin free standing films and its gas transport properties were evaluated. The PS-PDMS-PS triblock copolymers were successfully hydrogenated for the first time to obtain the PCHE-PDMS-PCHE triblock copolymers (PCHE stands for polycyclohexylethylene). The hydrogenation reaction proceeded without any polymer chain breaking and the resultant polymer showed some interesting, rather unexpected thermodynamic properties. These polymeric materials are potentially useful as the matrix of nanocomposite membranes. Highly crystalline zeolite sheets were obtained by exfoliation of zeolite lamellae. Preservation of crystal morphology and pore structure, which presents a major challenge during the exfoliation process, was successfully addressed in this work by judicious choice of operating conditions. Lamellae were exfoliated by surfactant intercalation and subsequently melt processing with polymers, resulting in polymer nanocomposites containing thin zeolite sheets (2.5 nm) with well preserved pore structure. A method to obtain polymer-free exfoliated sheets was also developed to facilitate the fabrication of inorganic composite membranes. These zeolite sheets can be used as the selectivity-enhancement additive in composite membranes.

Maheshwari, Sudeep

143

Microscopic characterization of crystalline phases in waste forms  

SciTech Connect

Transmission electron microscopy (TEM) has been used to determine the microstructure of crystalline phases present in zirconium- and titanium-bearing glass crystalline composite (GCC) waste forms. The GCC materials were found to contain spinels (maghemite), zirconolites, perovskites (CaTiO{sub 3}) and plagiociase feldspar (anorthite) mineral phases. The structure of the uranium and cerium-bearing monoclinic zirconolite was characterized by medium resolution TEM imaging and electron and X-ray diffraction (XRD). The phase was found to contain high levels of iron in comparison to Synroc-type zirconolites. Excess zirconium in zirconolite has resulted in martensitic baddeleyite (ZrO{sub 2}) formation. Anorthite (CaAl{sub 2}Si{sub 2}O{sub 8}) was present as elongated crystallites within a calcium-rich aluminosilicate glass. Lead and iron-bearing anorthite lying along distinct precipitates were occasionally observed within the an crystallographic planes.

Buck, E.C.; Dietz, N.L.; Wronkiewicz, D.J.; Bates, J.K. [Argonne National Lab., IL (United States); Millar, A. [Purdue Univ., West Lafayette, IN (United States)

1995-07-01

144

High functional expression of osteoblasts on imogolite, aluminosilicate nanotubes.  

PubMed

Imogolite is a naturally occurring aluminosilicate clay mineral with a nanotube structure of 2 nm diameter and 60 nm-2 microm length. In this study, synthetic imogolite nanotubes were applied to cell culture and the properties as a scaffold were compared with those of a conventional culture dish and a carbon nanotube (CNT) scaffold. The surface characteristics of the imogolite scaffold were drastically changed with the amount of coated imogolite on the dish. With the increase of imogolite concentration, the surface morphology of the scaffolds changed from an island-like shape in random orientation to a self-organized fiber texture aligned in the same direction, and finally full coverage in a random orientation with plural layers. Silicon releasability of the scaffolds was increased with the amount of coated imogolite. Mouse osteoblast-like cells (MC3T3-E1) cultured on imogolite showed a flat-form morphology and a cytoskeleton developed in all directions in contrast to a spindle-shaped morphology developed in one direction on cell culture dishes and CNT scaffolds. The proliferation and osteoblastic functions in ALP activity and mineralization showed similar increasing tendency. The largest values were obtained from the scaffold with a high concentration of imogolite. The results indicated good biocompatibility between the cells and imogolite scaffold and the enhancement effect of proliferation and osteoblastic differentiation. PMID:20499833

Ishikawa, Kosuke; Akasaka, Tsukasa; Yawaka, Yasutaka; Watari, Fumio

2010-02-01

145

Aqueous dissolution of sodium aluminosilicate geopolymers derived from metakaolin  

NASA Astrophysics Data System (ADS)

In dilute aqueous solutions, the elemental releases of Na, Al and Si from a metakaolin-based sodium aluminosilicate geopolymer were not very sensitive to pH in the range of 4-10 but increased outside this range, particularly on the acidic side. To minimise pH drifts, experiments were carried out using small amounts of graded powders in relatively large volumes of water. In deionised water, the Na dissolution rate in 7 days was dominant and increased by at least a factor of 4 on heating from 18 to 90 C, with greater increases in the extractions of Al and Si. At 18 C the elemental extractions in deionised water increased approximately linearly with time over the 1-7 days period. Further exposure led to a slower extraction into solution for Na and Si, with a decrease in extraction of Al. It was deduced that framework dissolution was important in significantly acidic or alkaline solutions, but that contributions from water transfer from pores to elemental extractions were present, even at low temperatures in neutral solutions. It was also deduced from the Na release data that the Na leaching kinetics of geopolymer in deionised water (dilute solutions) followed the pseudo-second-order kinetic model and the pseudo-second-order rate constant evaluated. Contact with KCl, KHCO3, and pH 6 and 10 potassium phthalate buffer solutions gave rise to a high degree of Na+ ? K+ exchange and rendered the framework ions less leachable in water.

Aly, Z.; Vance, E. R.; Perera, D. S.

2012-05-01

146

Mixed alkaline earth effect in the compressibility of aluminosilicate glasses.  

PubMed

The mixed modifier effect (MME) in oxide glasses manifests itself as a non-additive variation in certain properties when one modifier oxide species is substituted by another one at constant total modifier content. However, the structural and topological origins of the MME are still under debate. This study provides new insights into the MME by investigating the effect of isostatic compression on density and hardness of mixed MgO/CaO sodium aluminosilicate glasses. This is done using a specially designed setup allowing isostatic compression of bulk glass samples up to 1 GPa at elevated temperature. A mixed alkaline earth effect is found in the compressibility and relative change of hardness, viz., a local maximum of density as a function of Mg/Ca ratio appears following compression, whereas a local minimum of hardness in the uncompressed glasses nearly disappears after compression. Moreover, the densification of these glasses is found to occur at temperatures much below the glass transition temperature, indicating that a non-viscous mechanism is at play. This is further supported by the fact that density relaxes in a stretched exponential manner upon subsequent annealing at ambient pressure with an exponent of ?0.62. This is close to the Phillips value of 3/5 for relaxation in three dimensions when both short- and long-range interactions are activated. PMID:24511956

Smedskjaer, Morten M; Rzoska, Sylwester J; Bockowski, Michal; Mauro, John C

2014-02-01

147

Surface functionalization of aluminosilicate nanotubes with organic molecules  

PubMed Central

Summary The surface functionalization of inorganic nanostructures is an effective approach for enriching the potential applications of existing nanomaterials. Inorganic nanotubes attract great research interest due to their one-dimensional structure and reactive surfaces. In this review paper, recent developments in surface functionalization of an aluminosilicate nanotube, imogolite, are introduced. The functionalization processes are based on the robust affinity between phosphate groups of organic molecules and the aluminol (AlOH) surface of imogolite nanotubes. An aqueous modification process employing a water soluble ammonium salt of alkyl phosphate led to chemisorption of molecules on imogolite at the nanotube level. Polymer-chain-grafted imogolite nanotubes were prepared through surface-initiated polymerization. In addition, the assembly of conjugated molecules, 2-(5-hexyl-2,2:5,2-terthiophen-5-yl)ethylphosphonic acid (HT3P) and 2-(5-hexyl-2,2:5,2-terthiophen-5-yl)ethylphosphonic acid 1,1-dioxide (HT3OP), on the imogolite nanotube surface was achieved by introducing a phosphonic acid group to the corresponding molecules. The optical and photophysical properties of these conjugated-molecule-decorated imogolite nanotubes were characterized. Moreover, poly(3-hexylthiophene) (P3HT) chains were further hybridized with HT3P modified imogolite to form a nanofiber hybrid. PMID:22428100

Ma, Wei; Yah, Weng On; Otsuka, Hideyuki

2012-01-01

148

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...

149

Comparing quantum-chemical calculation methods for structural investigation of zeolite crystal structures by solid-state NMR spectroscopy.  

PubMed

Combining quantum-chemical calculations and ultrahigh-field NMR measurements of (29)Si chemical shielding (CS) tensors has provided a powerful approach for probing the fine details of zeolite crystal structures. In previous work, the quantum-chemical calculations have been performed on 'molecular fragments' extracted from the zeolite crystal structure using Hartree-Fock methods (as implemented in Gaussian). Using recently acquired ultrahigh-field (29) Si NMR data for the pure silica zeolite ITQ-4, we report the results of calculations using recently developed quantum-chemical calculation methods for periodic crystalline solids (as implemented in CAmbridge Serial Total Energy Package (CASTEP) and compare these calculations to those calculated with Gaussian. Furthermore, in the context of NMR crystallography of zeolites, we report the completion of the NMR crystallography of the zeolite ITQ-4, which was previously solved from NMR data. We compare three options for the 'refinement' of zeolite crystal structures from 'NMR-solved' structures: (i) a simple target-distance based geometry optimization, (ii) refinement of atomic coordinates in which the differences between experimental and calculated (29)Si CS tensors are minimized, and (iii) refinement of atomic coordinates to minimize the total energy of the lattice using CASTEP quantum-chemical calculations. All three refinement approaches give structures that are in remarkably good agreement with the single-crystal X-ray diffraction structure of ITQ-4. PMID:20623826

Brouwer, Darren H; Moudrakovski, Igor L; Darton, Richard J; Morris, Russell E

2010-12-01

150

Structure-Entropy Relationships in Aluminosilicate Garnets (Invited)  

NASA Astrophysics Data System (ADS)

Aluminosilicate garnet (X3Al2Si3O12) is a key rock-forming mineral whose geological occurrence is widespread. Various petrologic, geochemical and geophysical processes can be best interpreted if garnet's structure and thermodynamic properties are understood. Extensive research has been done on garnet's crystal-chemical properties using diffraction and spectroscopic measurements as well as computational methods. The level of understanding is, in general, good. In terms of macroscopic thermodynamic properties, there has also been much work done over the years. Here, however, the level of understanding is less. Consider the crystal chemistry and entropy behavior of two binary solid solutions, namely pyrope-grossular (Py-Gr) [(MgxCa1-x)3Al2Si3O12] and almandine-spessartine (Al-Sp) [(FexMn1-x)3Al2Si3O12]. The heat capacity, Cp, of a series of well characterized natural and synthetic almandine-spessartine garnets was recently measured between 3 and 300 K (Dachs et al., submitted). All garnets show a ?-type anomaly at low temperatures resulting from a paramagnetic-antiferromagnetic phase transition. The lattice heat capacity, Cp,vib, was calculated for each garnet member by applying the phonon dispersion model of Komada and Westrum (1997). This allows a decomposition of S298 into its vibrational (Svib) and magnetic (Smag) contributions. A full analysis shows that the Al-Sp binary is entropically ideal with ?Sex ? 0 at 298 K. Previously published calorimetric work on Py-Gr garnets shows, in contrast, substantial positive ?Sex across the join at 298 K (Dachs and Geiger, 2006). Why the difference? The vibrational behavior of the divalent X cations plays an important role in affecting macroscopic Cp,vib and Svib in aluminosilicate garnets. X-ray single-crystal diffraction and XAFS measurements show that the mean square amplitudes of vibration for Fe2+ in Al and Mn2+ in Sp are similar and, moreover, they do not vary significantly in magnitude as a function of composition across the Al-Sp binary. Vibrational modes in IR and Raman spectra of Al-Sp garnets show mostly continuous and linear variation in wavenumber across the binary. These results are fully consistent with the calorimetric work indicating ?Sex ? 0 at 298 K. In contrast, the mean square amplitudes of vibration of Mg and Ca in Py-Gr garnets are substantially different from each other. The behavior of IR and Raman modes in spectra of Py-Gr garnets are also quite different than the spectra of Al-Sp garnets. Low energy modes related to Ca and especially Mg do not shift linearly in energy across the Py-Gr join but soften in intermediate compositions. This behavior is considered to be the cause of the large positive ?Sex behavior. Al-Sp garnets differ, of course, from Py-Gr garnets because of their magnetic and electronic contributions to Cp and S.

Geiger, C. A.; Dachs, E.

2013-12-01

151

Three Mile Island zeolite vitrification demonstration program  

Microsoft Academic Search

This paper presents a brief overview of the Three Mile Island (TMI) zeolite vitrification program. The formulation of a glass suitable for immobilizing submerged demineralizer system (SDS) zeolites is discussed. A feed system that was developed to feed zeolites to the in-can melter is described. The in-can melting process and the government-owned facilities in which the demonstrations will take place

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

1982-01-01

152

Increased thermal conductivity monolithic zeolite structures  

DOEpatents

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.

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

2008-11-25

153

Zeolites Remove Sulfur From Fuels  

NASA Technical Reports Server (NTRS)

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.

Voecks, Gerald E.; Sharma, Pramod K.

1991-01-01

154

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

SciTech Connect

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.

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

2007-01-01

155

Influence of glass polymerisation and oxidation on micro-Raman water analysis in alumino-silicate glasses  

E-print Network

Influence of glass polymerisation and oxidation on micro-Raman water analysis in alumino-silicate glasses Maxime Merciera, Andrea Di Muroab , Daniele Giordanoc , Nicole Métricha , Priscille Lesned of an accurate analytical procedure for determination of dissolved water in complex alumino-silicate glasses via

Paris-Sud XI, Université de

156

Formation of single-walled aluminosilicate nanotubes from molecular precursors and curved nanoscale intermediates.  

PubMed

We report the identification and elucidation of the mechanistic role of molecular precursors and nanoscale (1-3 nm) intermediates with intrinsic curvature in the formation of single-walled aluminosilicate nanotubes. We characterize the structural and compositional evolution of molecular and nanoscale species over a length scale of 0.1-100 nm by electrospray ionization mass spectrometry, nuclear magnetic resonance spectroscopy ((27)Al liquid-state, (27)Al and (29)Si solid-state MAS), and dynamic light scattering. Together with structural optimization of key experimentally identified species by solvated density functional theory calculations, this study reveals the existence of intermediates with bonding environments, as well as intrinsic curvature, similar to the structure of the final nanotube product. We show that "proto-nanotube-like" intermediates with inherent curvature form in aqueous synthesis solutions immediately after initial hydrolysis of reactants, disappear from the solution upon heating to 95 C due to condensation accompanied by an abrupt pH decrease, and finally form ordered single-walled aluminosilicate nanotubes. Detailed quantitative analysis of NMR and ESI-MS spectra from the relevant aluminosilicate, aluminate, and silicate solutions reveals the presence of a variety of monomeric and polymeric aluminate and aluminosilicate species (Al(1)Si(x)-Al(13)Si(x)), such as Keggin ions [AlO(4)Al(12)(OH)(24)(H(2)O)(12)](7+) and polynuclear species with a six-membered Al oxide ring unit. Our study also directly reveals the complexation of aluminate and aluminosilicate species with perchlorate species that most likely inhibit the formation of larger condensates or nontubular structures. Integration of all of our results leads to the construction of the first molecular-level mechanism of single-walled metal oxide nanotube formation, incorporating the role of monomeric and polymeric aluminosilicate species as well as larger nanoparticles. PMID:21417255

Yucelen, G Ipek; Choudhury, Rudra Prosad; Vyalikh, Anastasia; Scheler, Ulrich; Beckham, Haskell W; Nair, Sankar

2011-04-13

157

Characterization and comparison of pore landscapes in crystalline porous materials.  

PubMed

Crystalline porous materials have many applications, including catalysis and separations. Identifying suitable materials for a given application can be achieved by screening material databases. Such a screening requires automated high-throughput analysis tools that characterize and represent pore landscapes with descriptors, which can be compared using similarity measures in order to select, group and classify materials. Here, we discuss algorithms for the calculation of two types of pore landscape descriptors: pore size distributions and stochastic rays. These descriptors provide histogram representations that encode the geometrical properties of pore landscapes. Their calculation involves the Voronoi decomposition as a technique to map and characterize accessible void space inside porous materials. Moreover, we demonstrate pore landscape comparisons for materials from the International Zeolite Association (IZA) database of zeolite frameworks, and illustrate how the choice of pore descriptor and similarity measure affects the perspective of material similarity exhibiting a particular emphasis and sensitivity to certain aspects of structures. PMID:23876827

Pinheiro, Marielle; Martin, Richard L; Rycroft, Chris H; Jones, Andrew; Iglesia, Enrique; Haranczyk, Maciej

2013-07-01

158

Studies of aluminum reinsertion into borosilicate zeolites with intersecting channels of 10- and 12-ring channel systems.  

PubMed

The work here describes the kinetic analyses of aluminum replacement for boron in a suite of borosilicate molecular sieves. While the method has been described before as a means of converting synthesized borosilicates (with weak inherent acidity) to aluminosilicates (with much stronger acid strength) when there are large pores in the structure, here we carry out the transformation under less than optimal replacement concentrations, in order to better follow the kinetics. We examined several zeolite structures with boundary conditions of boron MEL where there are only 10-ring (or intermediate) pore structures and no Al is taken up, to multidimensional large pore zeolites, like boron beta, where Al substitution can occur everywhere. We also studied materials with both intermediate and large pores, SSZ-56, 57, 70, and 82. In the case of 57 up to 90% of the structure is made up of boron MEL. We observe that the pH drop is proportional to the Al reinsertion and is the same for all zeolites we studied. In one case, we compared a zeolite (SSZ-24) with boron and then no boron sites and found that Al does not go into defect sites. It was again confirmed (shown in earlier work) that Al will go into nest sites created by boron hydrolysis out of the substrate before Al treatment. Along those lines we also made two new observations: (1) the profile for Al uptake, as followed by pH drop, is the same kinetically, whether the boron is there or not; and (2) NMR showed that the boron is leaving the structure faster than Al can go back in (SSZ-33 study), even when we treat a material with boron in the lattice. PMID:24401027

Zones, Stacey I; Benin, Annabelle; Hwang, Son-Jong; Xie, Dan; Elomari, Saleh; Hsieh, Ming-Feng

2014-01-29

159

Synthesis and immobilization of quaternary ammonium cations in acidic zeolites  

Microsoft Academic Search

A general method for the synthesis of quaternary ammo- nium cations in acidic zeolites by a direct reaction of tertiary amines and alcohols is described. Zeolites and zeolite-related porous solids are ideal inorganic hosts for accommodating a large variety of guest species. 1 Bulky carbon-centered ionic intermediates, such as triar- ylmethyl cations, can be encapsulated within zeolite supercages via a

Wei Wang; Andreas Buchholz; Irina I. Ivanova; Jens Weitkampa; Michael Hunger

2003-01-01

160

The potential application of natural zeolite for greywater treatment  

Microsoft Academic Search

Natural zeolites are good potential material for water and wastewater treatment. It is due to the advantages of low cost, ion-exchange and adsorption capability of the natural zeolites. It can also be modified and regenerated. This paper thus looks at efforts made in exploring the potential application of natural zeolites and modified natural zeolites in water and wastewater treatment especially

Nurul Widiastuti; Hongwei Wu; Ming Ang; Dong-ke Zhang

2008-01-01

161

Synthesis of MFI zeolite membranes for water desalination  

Microsoft Academic Search

Zeolite membranes have been extensively researched for many industrial separations via gas permeation and liquid pervaporation processes. General separation mechanisms in zeolite membranes include molecular sieving and competitive adsorption and diffusion. Recently, the possibility of using zeolite membranes to remove ions from aqueous solutions by reverse osmosis (RO) has been explored. RO desalination by zeolite membranes may offer an alternative

Mansoor Kazemimoghadam; Toraj Mohammadi

2007-01-01

162

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...

163

Zeolitic materials with hierarchical porous structures.  

PubMed

During the past several years, different kinds of hierarchical structured zeolitic materials have been synthesized due to their highly attractive properties, such as superior mass/heat transfer characteristics, lower restriction of the diffusion of reactants in the mesopores, and low pressure drop. Our contribution provides general information regarding types and preparation methods of hierarchical zeolitic materials and their relative advantages and disadvantages. Thereafter, recent advances in the preparation and characterization of hierarchical zeolitic structures within the crystallites by post-synthetic treatment methods, such as dealumination or desilication; and structured devices by in situ and ex situ zeolite coatings on open-cellular ceramic foams as (non-reactive as well as reactive) supports are highlighted. Specific advantages of using hierarchical zeolitic catalysts/structures in selected catalytic reactions, such as benzene to phenol (BTOP) and methanol to olefins (MTO) are presented. PMID:21495091

Lopez-Orozco, Sofia; Inayat, Amer; Schwab, Andreas; Selvam, Thangaraj; Schwieger, Wilhelm

2011-06-17

164

Phosphatation of zeolite H-ZSM-5: a combined microscopy and spectroscopy study.  

PubMed

A variety of phosphated zeolite H-ZSM-5 samples are investigated by using a combination of Fourier transfer infrared (FTIR) spectroscopy, single pulse (27)Al, (29)Si, (31)P, (1)H-(31)P cross polarization (CP), (27)Al-(31)P CP, and (27)Al 3Q magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, scanning transmission X-ray microscopy (STXM) and N2 physisorption. This approach leads to insights into the physicochemical processes that take place during phosphatation. Direct phosphatation of H-ZSM-5 promotes zeolite aggregation, as phosphorus does not penetrate deep into the zeolite material and is mostly found on and close to the outer surface of the zeolite, acting as a glue. Phosphatation of pre-steamed H-ZSM-5 gives rise to the formation of a crystalline tridymite AlPO4 phase, which is found in the mesopores of dealuminated H-ZSM-5. Framework aluminum species interacting with phosphorus are not affected by hydrothermal treatment. Dealuminated H-ZSM-5, containing AlPO4 , retains relatively more framework Al atoms and acid sites during hydrothermal treatment than directly phosphated H-ZSM-5. PMID:24402742

van der Bij, Hendrik E; Aramburo, Luis R; Arstad, Bjrnar; Dynes, James J; Wang, Jian; Weckhuysen, Bert M

2014-02-01

165

Salt-thermal zeolitization of fly ash.  

PubMed

The molten-salt method has been recently proposed as a new approach to zeolitization of fly ash. Unlike the hydrothermal method, this method employs salt mixtures as the reaction medium without any addition of water. In this study, systematic investigation has been conducted on zeolitization of fly ash in a NaOH-NaNO3 system in order to elucidate the mechanism of zeolite formation and to achieve its optimization. Zeolitization of fly ash was conducted by thermally treating a powder mixture of fly ash, NaOH, and NaNO3. Zeolitization of fly ash took place above 200 degrees C, a temperature lower than the melting points of salt and base in the NaOH-NaNO3 system. However, it was uncertain whether the reactions took place in a local molten state or in a solid state. Therefore, the proposed method is renamed the "salt-thermal" method rather than the "molten-salt" method. Mainly because of difficulty in mobility of components in salt mixtures, zeolitization seems to occur within a local reaction system. In situ rearrangement of activated components seems to lead to zeolite formation. Particle growth, rather than crystal growth through agglomeration, resulted in no distinct morphologies of zeolite phases. Following are the optimal zeolitization conditions of the salt-thermal method: temperature, 250-350 degrees C; time, 3-12 h; weight ratio of NaOH/NaNO3, 0.3-0.5; weight ratio of NaNO3/fly ash, 0.7-1.4. Therefore, it is clear from this work that the salt-thermal method could be applied to massive zeolitization of fly ash as a new alternative method for recycling this waste. PMID:11452614

Choi, C L; Park, M; Lee, D H; Kim, I E; Park, B Y; Choi, J

2001-07-01

166

One-pot surfactant assisted synthesis of aluminosilicate macrochannels with tunable micro- or mesoporous wall structure.  

PubMed

A one-step surfactant assisted synthesis pathway was developed leading to novel hierarchical macro-meso- (or micro-)porous aluminosilicates made of an assembly of macrochannels with openings between 0.5 and 2.0 microm and wormhole-like amorphous walls with tunable pore sizes. PMID:14594284

Lonard, Alexandre; Blin, Jean-Luc; Su, Bao-Lian

2003-10-21

167

EFFECT OF IMPURITIES ASSOCIATED WITH ALUMINOSILICATES ON ARSENIC SORPTION AND OXIDATION  

EPA Science Inventory

Arsenite, As(III), and arsenate, As(V), are of increasing environmental concern. Risk assessment and risk management of arsenic contaminated sites requires a better understanding of arsenic-mineral interactions. Aluminosilicate minerals, such as feldspars and clays, are the mos...

168

Al NMR study of the structure of lanthanum and yttrium based aluminosilicate glasses and melts  

E-print Network

A 27 Al NMR study of the structure of lanthanum and yttrium based aluminosilicate glasses and melts allowed to follow selected samples from 2200°C down to 1700°C and hence to characterize the aluminum of glasses has a large range of applications in modern technology like (a) host materials for laser, optical

Paris-Sud XI, Université de

169

Characteristics of a thermally activated alumino-silicate pozzolanic material and its use in concrete  

Microsoft Academic Search

This paper presents the results of the physical and chemical properties of a thermally activated alumino-silicate material (MK), and deals with the properties of fresh and hardened concrete incorporating this material. The properties of fresh concrete investigated included workability, bleeding, setting time, and autogenous temperature rise. The properties of the hardened concrete investigated included compressive, splitting-tensile and flexural strengths, Young's

M. H. Zhang; V. M. Malhotra

1995-01-01

170

The Roles of Temperature and Composition in High-Pressure Structural Changes in Aluminosilicate Melts  

Microsoft Academic Search

Extensive recent NMR studies show large effects of composition on the extent of structural change in aluminosilicate glasses quenched from melts at high pressure, which correlate with observed, recovered density increases. Although such results will eventually need to be complemented by quantitative, in situ spectroscopic and scattering measurements, they already provide important constraints on the types of models necessary to

J. F. Stebbins

2009-01-01

171

Zeolites on Mars: Prospects for Remote Sensing  

NASA Technical Reports Server (NTRS)

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.

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

1985-01-01

172

Interaction between zeolites and cluster compounds. Part 1.?Adsorption of iron pentacarbonyl on zeolites  

Microsoft Academic Search

Received 1 1 th November, 1982 The adsorption isotherms of Fe(CO), on Nay, HY and Linde L zeolites obtained in McBain balances show micropore adsorption, whereas additional capillary condensation is found with zeolite omega and Na-mordenite. The pores and\\/or cages of the zeolites studied are completely filled with the complex upon saturation, with the exception of Na-mordenite. Their behaviour is

Thomas Bein; Peter A. Jacobs

1983-01-01

173

Copper-Exchanged Zeolite L Traps Oxygen  

NASA Technical Reports Server (NTRS)

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.

Sharma, Pramod K.; Seshan, Panchalam K.

1991-01-01

174

Detecting Nanophase Weathering Products with CheMin: Reference Intensity Ratios of Allophane, Aluminosilicate Gel, and Ferrihydrite  

NASA Technical Reports Server (NTRS)

X-ray diffraction (XRD) data collected of the Rocknest samples by the CheMin instrument on Mars Science Laboratory suggest the presence of poorly crystalline or amorphous materials [1], such as nanophase weathering products or volcanic and impact glasses. The identification of the type(s) of X-ray amorphous material at Rocknest is important because it can elucidate past aqueous weathering processes. The presence of volcanic and impact glasses would indicate that little chemical weathering has occurred because glass is highly susceptible to aqueous alteration. The presence of nanophase weathering products, such as allophane, nanophase iron-oxides, and/or palagonite, would indicate incipient chemical weathering. Furthermore, the types of weathering products present could help constrain pH conditions and identify which primary phases altered to form the weathering products. Quantitative analysis of phases from CheMin data is achieved through Reference Intensity Ratios (RIRs) and Rietveld refinement. The RIR of a mineral (or mineraloid) that relates the scattering power of that mineral (typically the most intense diffraction line) to the scattering power of a separate mineral standard such as corundum [2]. RIRs can be calculated from XRD patterns measured in the laboratory by mixing a mineral with a standard in known abundances and comparing diffraction line intensities of the mineral to the standard. X-ray amorphous phases (e.g., nanophase weathering products) have broad scattering signatures rather than sharp diffraction lines. Thus, RIRs of X-ray amorphous materials are calculated by comparing the area under one of these broad scattering signals with the area under a diffraction line in the standard. Here, we measured XRD patterns of nanophase weathering products (allophane, aluminosilicate gel, and ferrihydrite) mixed with a mineral standard (beryl) in the CheMinIV laboratory instrument and calculated their RIRs to help constrain the abundances of these phases in the Rocknest samples.

Rampe, E. B.; Bish, D. L.; Chipera, S. J.; Morris, R. V.; Achilles, C. N.; Ming, D W.; Blake, D. F.; Anderson, R. C.; Bristow, T. F.; Crisp, A.; DesMarais, D. J.; Downs, R. T.; Farmer, J. D.; Morookian, J. M.; Morrison, S. M.; Sarrazin, P.; Spanovich, N.; Stolper, E. M.; Treiman, A. H.; Vaniman, D. T.; Yen, A. S.

2013-01-01

175

Mixing of zeolite powders and molten salt  

SciTech Connect

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.

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

1996-05-01

176

Dehydrated Lanthanum-exchanged Type Y Zeolite  

Microsoft Academic Search

Lanthanum atoms occupy different sites in the crystal structure of dehydrated type Y zeolite as the temperature changes, probably because of the absence of residual molecules for bonding at 725 C compared with their presence at lower temperatures.

J. V. Smith; J. M. Bennett; E. M. FLANIGEN

1967-01-01

177

Factors affecting the MTW zeolite cristallization process  

SciTech Connect

The synthesis mechanism of the high silica zeolite types other than MFI is rarely studied in the open literature. This work is devoted to the role of different parameters governing the zeolite MTW crystallization process. The influence of the most important factors: the nature of the silica and alumina source, the type of the organic cation, the alkalinity of the reaction mixture and the crystallization temperature, was studied. The molar composition of the initial hydrogel was varied in other to determine the crystallization field of the zeolite MTW. The observed morphology and particle size of the crystallites are related to the corresponding reaction conditions. The competitive formation of the other zeolite types (prevalently MFI and BEA) is discussed.

Katovic, A.; Giordano, G. [Universita della Calabria, Rende (Italy)

1995-12-01

178

Zeolite based catalysts for hydrodenitrogenation of quinoline  

E-print Network

ZEOLITE BASED CATALYSTS FOR HYDRODENITROGENATION OF QUINOLINE A Thesis by BHAVYEN SUNAN SANGHVI submitted to the Graduate College of Texas A 6 N University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE... December 1982 Najor Subject:Chemical Engineering ZEOLITE BASED CATALYSTS FOR HYDRODENITROGENATION OF QUINOLINE A Thesis by BHAVYEN SUNAN SANGHVI Approved as to style and content by: (Chairman of ommittee) (member) (member) yg-, , rn- !' (member...

Sanghvi, Bhavyen Suman

2012-06-07

179

Metal loading and reactivity of Zeolite Y  

E-print Network

METAL LOADING AND REACTIVITY OF ZEOLITE Y A Thesis by MARC GERARD SAENZ Submitted to the Graduate College of Texas ARM University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE August 1988 Major Subject...: Chemical Engineering METAL LOADING AND REACTIVITY OF ZEOLITE Y A Thesis by MARC GERARD SAENZ Approved as to style and content by: ydin Akgerma (Chairman of Co ttee) Da id L. Cocke (Member) Ahmed M. Gadalla (Member ) Raymond W. Plumer elt (Head...

Sa?enz, Marc Gerard

2012-06-07

180

Adsorption Behavior of Chlorophenols on Natural Zeolite  

Microsoft Academic Search

The adsorption of aqueous organic pollutants, i.e., phenol, monochlorophenols (2?and 4?), and dichlorophenols (2,4?and 3,5?) on natural Jordanian zeolitic tuff was studied. Three simplified kinetic models, viz., pseudo?first order, pseudo?second order, and intraparticle diffusion models were used to fit the kinetics data. The results revealed that at earlier stages of adsorption of phenols onto zeolite, the pseudo?second order and the

Rushdi I. Yousef

2007-01-01

181

Topological crystalline insulator nanostructures.  

PubMed

Topological crystalline insulators are topological insulators whose surface states are protected by the crystalline symmetry, instead of the time reversal symmetry. Similar to the first generation of three-dimensional topological insulators such as Bi2Se3 and Bi2Te3, topological crystalline insulators also possess surface states with exotic electronic properties such as spin-momentum locking and Dirac dispersion. Experimentally verified topological crystalline insulators to date are SnTe, Pb1-xSnxSe, and Pb1-xSnxTe. Because topological protection comes from the crystal symmetry, magnetic impurities or in-plane magnetic fields are not expected to open a gap in the surface states in topological crystalline insulators. Additionally, because they have a cubic structure instead of a layered structure, branched structures or strong coupling with other materials for large proximity effects are possible, which are difficult with layered Bi2Se3 and Bi2Te3. Thus, additional fundamental phenomena inaccessible in three-dimensional topological insulators can be pursued. In this review, topological crystalline insulator SnTe nanostructures will be discussed. For comparison, experimental results based on SnTe thin films will be covered. Surface state properties of topological crystalline insulators will be discussed briefly. PMID:25350386

Shen, Jie; Cha, Judy J

2014-11-01

182

Three Mile Island zeolite vitirification demonstration program  

SciTech Connect

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.

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

1981-06-01

183

Kinetics of zeolite dealumination in steam  

SciTech Connect

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.

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

1998-08-01

184

Properties of glass-bonded zeolite monoliths  

SciTech Connect

It has been shown that mineral waste forms can be used to immobilize waste salt generated during the pyrochemical processing of spent fuel from the Integral Fast Reactor (IFR). Solid, leach resistant monoliths were formed by hot-pressing mixtures of salt-occluded zeolite A powders and glass frit at 990 K and 28 MPa. Additional samples have now been fabricated and tested. Normalized release rates for all elements, including iodide and chloride, were less than 1 g/m{sup 2}d in 28-day tests in deionized water and in brine at 363 K (90{degrees}C). Preliminary results indicate that these rates fall with time with both leachants and that the zeolite phase in the glass-bonded zeolite does not function as an ion exchanger. Some material properties were measured. The Poisson ratio and Young`s modulus were slightly smaller in glass-bonded zeolite than in borosilicate glass. Density depended on zeolite fraction. The glass-bonded zeolite represents a promising mineral waste form for IFR salt.

Lewis, M.A.; Fischer, D.F. [Argonne National Lab., IL (United States); Murphy, C.D. [Univ. of Cincinnati, OH (United States)

1994-05-01

185

Nuclear Magnetic Resonance Studies of Aluminosilicate Gels Prepared in High-Alkaline and Salt-Concentrated Solutions  

SciTech Connect

We have examined the formation of aluminosilicate in high alkaline and salt concentrated solutions characteristic of nuclear tank wastes. Information on the mechanism and kinetics of the phase formation under hydrothermal conditions was obtained by characterization the structures of gel phases as a function of time and composition using multinuclear NMR techniques in combination with x-ray diffraction. This work offers a new insight into the aluminum and aluminosilicate chemistry in simulated nuclear tank wastes.

Wang, Li Q.; Mattigod, Shas V.; Parker, Kent E.; Hobbs, David T.; McCready, David E.

2005-01-11

186

Liquid hydrocarbon fuels from palm oil by catalytic cracking over aluminosilicate mesoporous catalysts with various Si\\/Al ratios  

Microsoft Academic Search

The production of liquid fuels from palm oil was studied at atmospheric pressure, reaction temperature of 723 K and weight hourly space velocity of 2.5 h?1 in a fixed bed micro-reactor containing aluminosilicate mesoporous material as cracking catalysts. The aluminosilicate materials with different Si\\/Al ratios were synthesized by direct (solgel and hydrothermal) and post-synthesis (ion-exchange and grafting) methods. The synthesized

Farouq A. Twaiq; Abdul Rahman Mohamed; Subhash Bhatia

2003-01-01

187

Mechanism of Zeolite Crystallization and Thermochemical Properties of Some Synthetic Zeolites. Final Report.  

National Technical Information Service (NTIS)

During the period of 4/1/82 to 9/30/84, the Department of Energy has provided support for laboratory synthesis of zeolites, calorimetric determinations, and thermal analyses on synthetic zeolites. This Final Report to the DOE is written as 6 independent s...

J. G. Liou

1984-01-01

188

Maximizing the catalytic function of hydrogen spillover in platinum-encapsulated aluminosilicates with controlled nanostructures  

NASA Astrophysics Data System (ADS)

Hydrogen spillover has been studied for several decades, but its nature, catalytic functions and even its existence remain topics of vigorous debate. This is a consequence of the lack of model catalysts that can provide direct evidences of the existence of hydrogen spillover and simplify the catalytic interpretation. Here we use platinum encapsulated in a dense aluminosilicate matrix with controlled diffusional properties and surface hydroxyl concentrations to elucidate the catalytic functions of hydrogen spillover. The catalytic investigation and theoretical modelling show that surface hydroxyls, presumably Brnsted acids, are crucial for utilizing the catalytic functions of hydrogen spillover on the aluminosilicate surface. The catalysts with optimized nanostructure show remarkable activities in hydro-/dehydrogenation, but virtually no activity for hydrogenolysis. This distinct chemoselectivity may be beneficial in industrially important hydroconversions such as propane dehydrogenation to propylene because the undesired hydrogenolysis pathway producing light hydrocarbons of low value (methane and ethane) is greatly suppressed.

Im, Juhwan; Shin, Hyeyoung; Jang, Haeyoun; Kim, Hyungjun; Choi, Minkee

2014-02-01

189

The catalytic reduction of nitric oxide with ammonia over tetraamminecopper (II) complexes  

E-print Network

that the ennanced catalytic activity of the NO-NH system in the presence of oxygen is directly 3 proportional to the amount of surface oxygen. The unusual activity profile of the reaction of nitric oxide with 23 ammonia over Cuy zeolites was first reported... of nitric oxide with ammonia over tetraamminecopper(II) complexes in aqueous solutions to compare this reaction environment with the parallel reac- tion over Cu(II) NaY zeolites. Zeolites are crystalline aluminosilicates which contain exchangeable...

Oates, Margaret Deron

2012-06-07

190

Structure of Cl-containing silicate and aluminosilicate glasses: A 35Cl MAS-NMR study  

Microsoft Academic Search

Chlorine-35 magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra were collected at 14.1 and 18.8 Tesla fields to determine the atomic scale structural environments of the chloride ions in anhydrous and hydrous silicate and aluminosilicate glasses containing 0.2 to 0.7 wt% Cl. NMR peaks are broad and featureless, but are much narrower than the total chemical shift range for

Travis O. Sandland; Lin-Shu Du; Jonathan F. Stebbins; James D. Webster

2004-01-01

191

Structure and mechanical properties of aluminosilicate geopolymer composites with Portland cement and its constituent minerals  

Microsoft Academic Search

The compressive strengths and structures of composites of aluminosilicate geopolymer with the synthetic cement minerals C3S, ?-C2S, C3A and commercial OPC were investigated. All the composites showed lower strengths than the geopolymer and OPC paste alone. X-ray diffraction, 29Si and 27Al MAS NMR and SEM\\/EDS observations indicate that hydration of the cement minerals and OPC is hindered in the presence

Jonathan Tailby; Kenneth J. D. MacKenzie

2010-01-01

192

What Is Crystalline Silica?  

MedlinePLUS

... glass. Additionally, crystalline silica exposures occur in the maintenance, repair and replacement of refractory brick furnace linings. In the maritime industry, shipyard employees are exposed to silica primarily in abrasive blasting operations to remove paint and clean and prepare steel ...

193

Source fabrication and lifetime for Li+ ion beams extracted from alumino-silicate sources  

SciTech Connect

A space-charge-limited beam with current densities (J) exceeding 1 mA/cm{sup 2} have been measured from lithium alumino-silicate ion sources at a temperature of #24;~1275#14;{degrees} C. At higher extraction voltages, the source appears to become emission limited with J #21;{>=} 1.5 mA/cm{sup 2}, and J increases weakly with the applied voltage. A 6.35 mm diameter source with an alumino-silicate coating, {<=}#20;0.25 mm thick, has a measured lifetime of ~#24;40 hours at ~#24;1275#14;{degrees} C, when pulsed at 0.05 Hz and with pulse length of #24;~6 μs each. At this rate, the source lifetime was independent of the actual beam charge extracted due to the loss of neutral atoms at high temperature. The source lifetime increases with the amount of alumino-silicate coated on the emitting surface, and may also be further extended if the temperature is reduced between pulses.

Roy, Prabir K.; Greenway, Wayne G.; Kwan, Joe W

2012-03-05

194

Source fabrication and lifetime for Li{sup +} ion beams extracted from alumino-silicate sources  

SciTech Connect

A space-charge-limited beam with current densities (J) exceeding 1 mA/cm{sup 2} have been measured from lithium alumino-silicate ion sources at a temperature of ?1275{degrees}C. At higher extraction voltages, the source appears to become emission limited with J ? 1.5 mA/cm{sup 2}, and J increases weakly with the applied voltage. A source with an alumino-silicate coating 6.35 mm in diameter and ?0.25 mm thick, has a lifetime of ?40 hours at ?1275{degrees}C, when pulsed at 0.05 Hz and with pulse length of ?6 ?s each. At this rate, the source lifetime was independent of the actual beam charge extracted due to the loss of neutral atoms at high temperature. Furthermore, the source lifetime increases with the amount of alumino-silicate coated on the emitting surface, and may also be extended if the temperature is reduced between pulses.

Greenway, W. G.; Kwan, J. W.

2012-02-10

195

2.5 Zeolites 2.5.1 Introduction  

E-print Network

). The value of zeolite catalysis to petroleum cracking is well in excess of $200 billion (MassNanoTech 2007 of zeolites' catalytic activity that is so important to the petrochemical industry. A second consequence

196

Alkylation of aniline with n -propyl alcohol over zeolites  

Microsoft Academic Search

The alkylation of aniline withn-propyl alcohol over ZSM-5 and Y zeolites has been studied. Ce-exchanged Y zeolites proved to be the most active for the alkylation of aniline byn-propyl alcohol. The reaction of N-propylaniline over zeolites has been investigated. N-alkylaniline decomposed over zeolites to aniline and alkene, which in turn rearrange to C-alkylanilines.n-Propyl derivatives were formed through an SN2 type

R. B. C. Pillai

1996-01-01

197

Salt-occluded zeolite waste forms: Crystal structures and transformability  

Microsoft Academic Search

Neutron diffraction studies of salt-occluded zeolite and zeolite\\/glass composite samples, simulating nuclear waste forms loaded with fission products, have revealed complex structures, with cations assuming the dual roles of charge compensation and occlusion (cluster formation). These clusters roughly fill the 6--8 diameter pores of the zeolites. Samples are prepared by equilibrating zeolite-A with complex molten Li, K, Cs, Sr,

J. W. Jr

1996-01-01

198

Design and fabrication of zeolite macro- and micromembranes  

NASA Astrophysics Data System (ADS)

The chemical nature of the support surface influences zeolite nucleation, crystal growth and elm adhesion. It had been demonstrated that chemical modification of support surface can significantly alter the zeolite film and has a good potential for large-scale applications for zeolite membrane production. The incorporation of titanium and vanadium metal ions into the structural framework of MFI zeolite imparts the material with catalytic properties. The effects of silica and metal (i.e., Ti and V) content, template concentration and temperature on the zeolite membrane growth and morphology were investigated. Single-gas permeation experiments were conducted for noble gases (He and Ar), inorganic gases (H2, N2, SF6) and hydrocarbons (methane, n-C4, i-C4) to determine the separation performance of these membranes. Using a new fabrication method based on microelectronic fabrication and zeolite thin film technologies, complex microchannel geometry and network (<5 mum), as well as zeolite arrays (<10 mum) were successfully fabricated onto highly orientated supported zeolite films. The zeolite micropatterns were stable even after repeated thermal cycling between 303 K and 873 K for prolonged periods of time. This work also demonstrates that zeolites (i.e., Sil-1, ZSM-5 and TS-1) can be employed as catalyst, membrane or structural materials in miniature chemical devices. Traditional semiconductor fabrication technology was employed in micromachining the device architecture. Four strategies for the manufacture of zeolite catalytic microreactors were discussed: zeolite powder coating, uniform zeolite film growth, localized zeolite growth, and etching of zeolite-silicon composite film growth inhibitors. Silicalite-1 was also prepared as free-standing membrane for zeolite membrane microseparators.

Chau, Lik Hang Joseph

2001-07-01

199

Transalkylation of toluene with trimethylbenzenes over large-pore zeolites  

Microsoft Academic Search

Zeolites Beta, mordenite and Y were evaluated for their activity in transalkylation reaction of toluene with trimethylbenzenes. Zeolite Beta was found to possess the highest conversion in toluenetrimethylbenzene transalkylation as well as a higher stability in time-on-stream compared with mordenite and zeolite Y. The effect of Si\\/Al ratio in zeolite Beta was evaluated and it was found that transalkylation activity

Andrea Krej?; Sulaiman Al-Khattaf; Muhammad Ashraf Ali; Martina Bejblov; Ji? ?ejka

2010-01-01

200

Cerium uptake by zeolite A synthesized from natural clinoptilolite tuffs  

Microsoft Academic Search

SummaryNatural clinoptilolite tuffs from the Semnan region in Iran was used for the synthesis of zeolite A. The tuffs and synthesized zeolites were characterized by XRD and XRF. The sorption behavior of the synthesized zeolite toward cerium was studied. Using the Lagergrens equation, the absorption constant was calculated. The measured distribution coefficient values (Kd) indicated that cerium uptake is higher

H. Faghihian; M. K. Amini; A. R. Nezamzadeh

2005-01-01

201

Natural zeolites in environmentally friendly processes and applications  

Microsoft Academic Search

An outline of the occurrences, features and environmental uses of the main sedimentary zeolites, namely chabazite, clinoptilolite, mordenite and phillipsite, is presented. After pointing out that zeolite-bearing rocks should not be considered as substitutes for synthetic zeolites, as they are lacking of purity and constancy of composition, three major areas of environmental application are identified: soil amendment, cement manufacture and

Carmine Colella

1999-01-01

202

Ion exchange in a zeolite-molten chloride system  

Microsoft Academic Search

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

R. H. Woodman; C. Pereira

1997-01-01

203

PARAMAGNETIC RESONANCE ABSORPTION OF GAMMA IRRADIATED SYNTHETIC ZEOLITES  

Microsoft Academic Search

The effect of gamma irradiation of synthetic zeolites was studied. ; Sodium X and sodium Y zeolites and also decationated samples prepared from these ; were irradiated in vacuum at room temperature with doses up to 20 megaroentgens. ; Two types of EPR signals were obtained. For the sodium Y and the sodium X ; zeolite a single line signal

D. N. Stamires; J. Turkevich

1963-01-01

204

The efficiency of Jordanian natural zeolite for heavy metals removal  

Microsoft Academic Search

The capability of Jordanian natural zeolite to remove nickel from aqueous solutions was experimentally investigated using a packed bed column. The zeolite samples were obtained from Jabal AL Aritayn in the northeast of Jordan. The effects of the initial concentration of nickel (C0), the packed bed length (L) and the zeolite grain size (Dp) on the adsorption process were considered.

Yazan Taamneh; Yazan TaamnehReyad Al Dwairi

2013-01-01

205

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

PubMed

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

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

2011-11-01

206

?-Crystallin as a molecular chaperone  

Microsoft Academic Search

The role of ?-crystallin as a molecular chaperone may explain how the lens stays transparent for so long. ?-Crystallin prevents the aggregation of other lens crystallins and proteins that have become unfolded by trapping the protein in a high molecular weight complex. It also protects enzyme activities. The substrate protein may interact while in a molten globule state. ?-Crystallin predominantly

Barry K Derham; John J Harding

1999-01-01

207

Zeolites as catalysts in oil refining.  

PubMed

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

Primo, Ana; Garcia, Hermenegildo

2014-10-20

208

Italian zeolitized rocks of technological interest  

NASA Astrophysics Data System (ADS)

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.

de'Gennaro, M.; Langella, A.

1996-09-01

209

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

NASA Astrophysics Data System (ADS)

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.

Stoeger, Jared Andrew

210

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

SciTech Connect

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.

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

2009-06-04

211

Hydrogen Purification Using Natural Zeolite Membranes  

NASA Technical Reports Server (NTRS)

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.

DelValle, William

2003-01-01

212

Positron annihilation in zeolite 13X  

NASA Astrophysics Data System (ADS)

Results presented in previous papers on positron annihilation in zeolite 13X referred only to fully hydrated or dehydrated samples. In these investigations the dehydration process was studied based on measurements of positron lifetime spectra in zeolite 13X samples. All spectra were resolved into three or four components. Measurements show that water removal is most intensive at the beginning of pumping. For dehydration at higher temperature results suggest that the last molecules of ``zeolitic water'' are removed from the sample at a temperature of about 200 C. It was found that independent of the stage of dehydration of the sample the intensity (I3+I4) of the two longest components in the spectrum is virtually constant (24%) and is equal to the intensity I3 of the longest component for the fully hydrated sample.

Habrowska, A. M.; Popiel, E. S.

1987-09-01

213

Studies of anions sorption on natural zeolites.  

PubMed

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

Barczyk, K; Mozgawa, W; Krl, M

2014-12-10

214

Development of a Composite Non-Electrostatic Surface Complexation Model Describing Plutonium Sorption to Aluminosilicates  

SciTech Connect

Due to their ubiquity in nature and chemical reactivity, aluminosilicate minerals play an important role in retarding actinide subsurface migration. However, very few studies have examined Pu interaction with clay minerals in sufficient detail to produce a credible mechanistic model of its behavior. In this work, Pu(IV) and Pu(V) interactions with silica, gibbsite (Aloxide), and Na-montmorillonite (smectite clay) were examined as a function of time and pH. Sorption of Pu(IV) and Pu(V) to gibbsite and silica increased with pH (4 to 10). The Pu(V) sorption edge shifted to lower pH values over time and approached that of Pu(IV). This behavior is apparently due to surface mediated reduction of Pu(V) to Pu(IV). Surface complexation constants describing Pu(IV)/Pu(V) sorption to aluminol and silanol groups were developed from the silica and gibbsite sorption experiments and applied to the montmorillonite dataset. The model provided an acceptable fit to the montmorillonite sorption data for Pu(V). In order to accurately predict Pu(IV) sorption to montmorillonite, the model required inclusion of ion exchange. The objective of this work is to measure the sorption of Pu(IV) and Pu(V) to silica, gibbsite, and smectite (montmorillonite). Aluminosilicate minerals are ubiquitous at the Nevada National Security Site and improving our understanding of Pu sorption to aluminosilicates (smectite clays in particular) is essential to the accurate prediction of Pu transport rates. These data will improve the mechanistic approach for modeling the hydrologic source term (HST) and provide sorption Kd parameters for use in CAU models. In both alluvium and tuff, aluminosilicates have been found to play a dominant role in the radionuclide retardation because their abundance is typically more than an order of magnitude greater than other potential sorbing minerals such as iron and manganese oxides (e.g. Vaniman et al., 1996). The sorption database used in recent HST models (Carle et al., 2006) and upscaled for use in CAU models (Stoller-Navarro, 2008) includes surface complexation constants for U, Am, Eu, Np and Pu (Zavarin and Bruton, 2004). Generally, between 15 to 30 datasets were used to develop the constants for each radionuclide. However, the constants that describe Pu sorption to aluminosilicates were developed using only 10 datasets, most of which did not specify the oxidation state of Pu in the experiment. Without knowledge or control of the Pu oxidation state, a high degree of uncertainty is introduced into the model. The existing Pu surface complexation model (e.g. Zavarin and Bruton, 2004) drastically underestimates Pu sorption and, thus, will overestimate Pu migration rates (Turner, 1995). Recent HST simulations at Cambric (Carle et al., 2006) suggest that the existing surface complexation model may underpredict Pu K{sub d}s by as much as 3 orders of magnitude. In order to improve HST and CAU-scale transport models (and, as a result, reduce the conservative nature Pu migration estimates), sorption experiments were performed over a range of solution conditions that brackets the groundwater chemistry of the Nevada National Security Site. The aluminosilicates examined were gibbsite, silica, and montmorillonite.

Powell, B A; Kersting, A; Zavarin, M; Zhao, P

2008-10-28

215

Photocatalytic activity of undoped and Ag-doped TiO{sub 2}-supported zeolite for humic acid degradation and mineralization  

SciTech Connect

Highlights: {yields} Hybrid materials based on natural zeolite and TiO{sub 2} obtained by solid-state reaction. {yields} XRD proved the presence of anatase form of undoped and Ag-doped TiO{sub 2} onto zeolite. {yields} FT-IR spectra evidenced the presence on TiO{sub 2} bounded at the zeolite network. {yields} Ag-doped TiO{sub 2} onto zeolitic matrix exhibited an enhanced photocatalytic activity. -- Abstract: The hybrid materials based on natural zeolite and undoped and Ag-doped TiO{sub 2}, i.e., Z-Na-TiO{sub 2} and Z-Na-TiO{sub 2}-Ag, were successfully synthesized by solid-state reaction in microwave-assisted hydrothermal conditions. Undoped TiO{sub 2} and Ag-doped TiO{sub 2} nanocrystals were previously synthesized by sol-gel method. The surface characterization of undoped TiO{sub 2}/Ag-doped TiO{sub 2} and natural zeolite hybrid materials has been investigated by X-ray diffraction, DRUV-VIS spectroscopy, FT-IR spectroscopy, BET analysis, SEM microscopy and EDX analysis. The results indicated that anatase TiO{sub 2} is the dominant crystalline type as spherical form onto zeolitic matrix. The presence of Ag into Z-Na-TiO{sub 2}-Ag was confirmed by EDX analysis. The DRUV-VIS spectra showed that Z-Na-TiO{sub 2}-Ag exhibited absorption within the range of 400-500 nm in comparison with Z-Na-TiO{sub 2} catalyst. The enhanced photocatalytic activity of Z-Na-TiO{sub 2}-Ag catalyst is proved through the degradation and mineralization of humic acid under ultraviolet and visible irradiation.

Lazau, C. [National Institute for Research and Development in Electrochemistry and Condensed Matter, Timisoara, Condensed Matter Department, P. Andronescu no.1, 300254 Timisoara (Romania)] [National Institute for Research and Development in Electrochemistry and Condensed Matter, Timisoara, Condensed Matter Department, P. Andronescu no.1, 300254 Timisoara (Romania); Ratiu, C. [National Institute for Research and Development in Electrochemistry and Condensed Matter, Timisoara, Condensed Matter Department, P. Andronescu no.1, 300254 Timisoara (Romania) [National Institute for Research and Development in Electrochemistry and Condensed Matter, Timisoara, Condensed Matter Department, P. Andronescu no.1, 300254 Timisoara (Romania); National Institute for Research and Development in Microtechnologies, Erou Iancu Nicolae Street, 077190 Bucharest (Romania); Orha, C. [National Institute for Research and Development in Electrochemistry and Condensed Matter, Timisoara, Condensed Matter Department, P. Andronescu no.1, 300254 Timisoara (Romania)] [National Institute for Research and Development in Electrochemistry and Condensed Matter, Timisoara, Condensed Matter Department, P. Andronescu no.1, 300254 Timisoara (Romania); Pode, R. ['Politehnica' University of Timisoara, P-ta Victoriei no.2, 300006 Timisoara (Romania)] ['Politehnica' University of Timisoara, P-ta Victoriei no.2, 300006 Timisoara (Romania); Manea, F., E-mail: florica.manea@chim.upt.ro ['Politehnica' University of Timisoara, P-ta Victoriei no.2, 300006 Timisoara (Romania)

2011-11-15

216

Liquid crystalline conducting polymers  

SciTech Connect

Recently we developed side chain liquid crystalline polyacetylene derivatives and achieved a substantial enhancement of electrical conductivity through magnetically forced alignment of the side chain of the polymer. When an electric field is employed as an alternative external force instead of the magnetic force, a ferroelectric liquid crystal should the more favorable than usual liquid crystals. This is because the former can respond more smoothly to the electric field owing to its spontaneous polarization than the latter. Here, in order to develop a novel liquid crystalline conducting polymer, we have synthesized a chiroptical liquid crystalline polyacetylene derivative. The liquid crystalline side chain of the polymer consists of a chiral alkyl moiety as a terminal group and a biphenyl moiety as a mesogenic core and a trimethylene segment as a spacer. The polymerization was carried out using a metathesis catalyst of MoCl{sub 5}-SnPh{sub 4}. Both the monomer and polymer showed the same signs in CD (circular dichroism) bands, indicating that the chirality of the monomer is maintained in the polymer. Measurements of DSC (differential scanning calorimeter) and polarizing microscope indicated that the polymer has a chiral smectic C (S{sub m} C*) phase assignable to the ferroelectric liquid crystal. Electrical and chemical properties of the polymer, including dielectric constant, electrical conductivity upon iodine doping and morphological alignment under an external force, are to be presented.

Akagi, K.; Goto, H.; Shirakawa, H. [Univ. of Tsukuba, Ibaraki (Japan)

1996-10-01

217

Effects of Fiber Content on Mechanical Properties of CVD SiC Fiber-Reinforced Strontium Aluminosilicate Glass-Ceramic Composites  

NASA Technical Reports Server (NTRS)

Unidirectional CVD SiC(f)(SCS-6) fiber-reinforced strontium aluminosilicate (SAS) glass-ceramic matrix composites containing various volume fractions, approximately 16 to 40 volume %, of fibers were fabricated by hot pressing at 1400 C for 2 h under 27.6 MPa. Monoclinic celsian, SrAl2Si2O8, was the only crystalline phase formed, with complete absence of the undesired hexacelsian phase, in the matrix. Room temperature mechanical properties were measured in 3-point flexure. The matrix microcracking stress and the ultimate strength increased with increase in fiber volume fraction, reached maximum values for V(sub f) approximately equal to 0.35, and degraded at higher fiber loadings. This degradation in mechanical properties is related to the change in failure mode, from tensile at lower V(sub f) to interlaminar shear at higher fiber contents. The extent of fiber loading did not have noticeable effect on either fiber-matrix debonding stress, or frictional sliding stress at the interface. The applicability of micromechanical models in predicting the mechanical properties of the composites was also examined. The currently available theoretical models do not appear to be useful in predicting the values of the first matrix cracking stress, and the ultimate strength of the SCS-6/SAS composites.

Bansal, Narottam P.

1996-01-01

218

Efficient adsorbents of nanoporous aluminosilicate monoliths for organic dyes from aqueous solution.  

PubMed

Growing public awareness on the potential risk to humans of toxic chemicals in the environment has generated demand for new and improved methods for toxicity assessment and removal, rational means for health risk estimation. With the aim of controlling nanoscale adsorbents for functionality in molecular sieving of organic pollutants, we fabricated cubic Im3m mesocages with uniform entrance and large cavity pores of aluminosilicates as highly promising candidates for the colorimetric monitoring of organic dyes in an aqueous solution. However, a feasible control over engineering of three-dimensional (3D) mesopore cage structures with uniform entrance (~5 nm) and large cavity (~10 nm) allowed the development of nanoadsorbent membranes as a powerful tool for large-quantity and high-speed (in minutes) adsorption/removal of bulk molecules such as organic dyes. Incorporation of high aluminum contents (Si/Al=1) into 3D cubic Im3m cage mesoporous silica monoliths resulted in small, easy-to-use optical adsorbent strips. In such adsorption systems, natural surfaces of active acid sites of aluminosilicate strips strongly induced both physical adsorption of chemically responsive dyes and intraparticle diffusion into cubic Im3m mesocage monoliths. Results likewise indicated that although aluminosilicate strips with low Si/Al ratios exhibit distortion in pore ordering and decrease in surface area and pore volume, enhancement of both molecular converges and intraparticle diffusion onto the network surfaces and into the pore architectures of adsorbent membranes was achieved. Moreover, 3D mesopore cage adsorbents are reversible, offering potential for multiple adsorption assays. PMID:21514595

El-Safty, Sherif A; Shahat, Ahmed; Awual, Md Rabiul

2011-07-01

219

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

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.

Snellings, R., E-mail: ruben.snellings@ees.kuleuven.b [Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven, Celestijnenlaan 200E, B-3001 Heverlee (Belgium); Mertens, G. [Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven, Celestijnenlaan 200E, B-3001 Heverlee (Belgium); Cizer, O. [Department of Civil Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 40, B-3001 Heverlee (Belgium); Elsen, J. [Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven, Celestijnenlaan 200E, B-3001 Heverlee (Belgium)

2010-12-15

220

Alkali aluminosilicate-saturated aqueous fluids in the earths upper mantle  

Microsoft Academic Search

The solubility in aqueous fluids of peralkaline alkali aluminosilicate components has been determined in the 0.8 to 2.0 GPa and 1000 to 1300C pressure and temperature range, respectively. Compositions were along the haploandesite join, Na2Si4O9Na2(NaAl)4O9, with 0, 3, and 6 mol.% Al2O3, denoted NS4Ax, where x represents the mol.% Al2O3.The silicate solubility in aqueous fluid is in the 3 to

Bjorn O. Mysen; Kevin Wheeler

2000-01-01

221

Direct detection of aluminosilicate species in aqueous solution by silicon-29 and aluminum-27 NMR spectroscopy  

Microsoft Academic Search

Silicon-29 NMR spectra of solutions containing 1 mol kg⁻¹ SiO and 0.07 mol kg⁻¹ Al in 2.4 mol kg⁻¹ aqueous NaOH at 5°C show five bands which are attributable to dissolved species containing Si-O-Al links. The major aluminosilicate species in solution appear to be Al-substituted derivatives of the silicate dimer, cyclic trimer, cyclic tetramer, and acyclic trimer. ²⁹Si spectra suggest

Stephen D. Kinrade; Thomas W. Swaddle

1989-01-01

222

Quantum mechanical calculation of 23 Na NMR shieldings in silicates and aluminosilicates  

Microsoft Academic Search

To assist in the assignment and interpretation of 23Na NMR spectra in silicate and aluminosilicate minerals and glasses we have calculated the 23Na NMR shieldings and the electric field gradients (EFG) at the Na for a number of Na-containing species. Included are Na(OH2)\\u000a n\\u000a \\u000a +, n?=?1, 2, 4, 5, 6 and 8, and Na+ complexes with SiH3OH, SiH3ONa and O(SiH3)2.

J. A. Tossell

1999-01-01

223

Thermomechanical Fatigue Behavior of a Silicon Carbide Fiber-Reinforced Calcium Aluminosilicate Composite  

Microsoft Academic Search

Isothermal fatigue and in-phase thermomechanical fatigue (TMF) tests were performed on a unidirectional, continuous-fiber, Nicalon-reinforced calcium aluminosilicate glass-ceramic composite ([0][sub 16], SiC\\/CAS-2). Monotonic tensile tests were performed at 1,100 C and 1,000 MPa\\/s to determine the material's ultimate strength ([sigma][sub ult]) and proportional limit ([sigma][sub pl]). Isothermal fatigue tests at 1,100 C employed two loading profiles, a triangular waveform with

T. Nicholas; J. W. Holmes

1993-01-01

224

Conversion of Fly Ash into Mesoporous Aluminosilicate Hsiao-Lan Chang, Chang-Min Chun, Ilhan A. Aksay, and Wei-Heng Shih*,  

E-print Network

Conversion of Fly Ash into Mesoporous Aluminosilicate Hsiao-Lan Chang, Chang-Min Chun, Ilhan A been synthesized from fused fly ash solutions and cationic cetyltrimethylammonium bromide (CTAB and aluminum sources. Fly ash, which is a byproduct of coal burning, contains mostly aluminosilicates. Recently

Aksay, Ilhan A.

225

JOURNAL DE PHYSIQUE Colloque C6, supplment au n" 8, Tome 39, aot 1978, page C6-934 MAGNETIC AFTEREFFECTS IN A COBALT ALUMINOSILICATE SPIN GLASS  

E-print Network

aluminosilicate glass, at tem- peratures around the AC susceptibility peak temperature (1> 7.8 K ) , are reported measure- ments of the DC susceptibility of a 35.5 at.% Co glass in the same temperature range AFTEREFFECTS IN A COBALT ALUMINOSILICATE SPIN GLASS t+ H.R. Rechenberg, and A.M. De Graaf Institute: de Fisiaa

Boyer, Edmond

226

Zeolite 5A Catalyzed Etherification of Diphenylmethanol  

ERIC Educational Resources Information Center

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

Cooke, Jason; Henderson, Eric J.; Lightbody, Owen C.

2009-01-01

227

POLYMER-ZEOLITE NANOCOMPOSITE HIGH-TEMPERATURE  

E-print Network

Efficiency · Industrial/Agricultural/Water End-Use Energy Efficiency · Renewable Energy TechnologiesPOLYMER-ZEOLITE NANOCOMPOSITE HIGH-TEMPERATURE PROTON-EXCHANGE-MEMBRANE FOR FUEL CELLS Prepared For: California Energy Commission Energy Innovations Small Grant Program Prepared By: Yushan Yan University

228

The poisoning of silver zeolite by organics  

Microsoft Academic Search

Silverzeolite was exposed to various organics to measure their effect on the silver zeolite's ability to subsequently adsorb iodine. The organics examined were alkanes, alkynes, aromatics, ketones, alcohols, and halocarbons (methyl and ethyl based). The reduction in iodine removal efficiency ranged from zero to 96%. Adding additional radicals to the base organic generally had the effect of decreasing the silver

J. G. Jolley; H. G. Tompkins

1984-01-01

229

Silver clusters and chemistry in zeolites  

SciTech Connect

The spectroscopic work done on silver clusters trapped in solid noble gas matrices at low temperature has been extensively reviewed by Ozin, and Henglein has done the same for photochemical studies of colloidal silver particles in solution. This article will review the chemistry of silver in zeolite hosts, including the synthesis and structures of silver clusters. 127 refs.

Sun, T.; Seff, K. (Univ. of Hawaii, Honolulu, HI (United States). Dept. of Chemistry)

1994-06-01

230

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 ...

231

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...

232

Dispersion enhanced metal/zeolite catalysts  

DOEpatents

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.

Sachtler, W.M.H.; Tzou, M.S.; Jiang, H.J.

1987-03-31

233

Dispersion enhanced metal/zeolite catalysts  

DOEpatents

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.

Sachtler, Wolfgang M. H. (Evanston, IL); Tzou, Ming-Shin (Evanston, IL); Jiang, Hui-Jong (Evanston, IL)

1987-01-01

234

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...

235

Mechanism of methanol conversion over zeolite  

Microsoft Academic Search

Details of the reaction mechanisms of conversions of methanol to various alkanes and alkenes were investigated. A discussion of the autocatalytic phenomena of the conversion of methanol over ZSM-5 zeolite was included. The temperature dependence and acidity aspects of the reaction rate were discussed. Also the use of Nafion-H and heteropolyacids as catalysts of conversion was also included. A detailed

1983-01-01

236

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

PubMed

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

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

2014-01-01

237

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...

238

Aqueous dissolution, solubilities and thermodynamic stabilities of common aluminosilicate clay minerals: Kaolinite and smectites  

USGS Publications Warehouse

Determinations of the aqueous solubilities of kaolinite at pH 4, and of five smectite minerals in suspensions set between pH 5 and 8, were undertaken with mineral suspensions adjusted to approach equilibrium from over- and undersaturation. After 1,237 days, Dry Branch, Georgia kaolinite suspensions attained equilibrium solubility with respect to the kaolinite, for which Keq = (2.72 ?? 0.35) ?? 107. The experimentally determined Gibbs free energy of formation (??Gf,2980) for the kaolinite is -3,789.51 ?? 6.60 kj mol-1. Equilibrium solubilities could not be determined for the smectites because the composition of the solution phase in the smectite suspensions appeared to be controlled by the formation of gibbsite or amorphous aluminum hydroxide and not by the smectites, preventing attempts to determine valid ??Gf0 values for these complex aluminosilicate clay minerals. Reported solubility-based ??Gf0 determinations for smectites and other variable composition aluminosilicate clay minerals are shown to be invalid because of experimental deficiencies and of conceptual flaws arising from the nature of the minerals themselves. Because of the variable composition of smectites and similar minerals, it is concluded that reliable equilibrium solubilities and solubility-derived ??Gf0 values can neither be rigorously determined by conventional experimental procedures, nor applied in equilibriabased models of smectite-water interactions. ?? 1986.

May, H.M.; Klnniburgh, D.G.; Helmke, P.A.; Jackson, M.L.

1986-01-01

239

Precursor impregnation and pyrolysis (PIP) processing of barium aluminosilicate - Nicalon composites  

SciTech Connect

Efforts were made to evaluate the utility of the polymer precursor method of processing Nicalon fiber reinforced barium aluminosilicate (BAS) composites. A novel precursor, synthesized in one step from BaO, Al(OH){sub 3} and SiO{sub 2} was used. This precursor, with a ceramic yield of {approx} 30 wt. %, was used to assess three forms of PIP processing. Fiber preforms consisting of 4-12 0/90{degrees} cross-woven Nicalon plies were impregnated with precursor/ethanol solutions at ambient pressure and under vacuum/pressure. Impregnated preforms were typically fired in air to 550{degrees}C to remove carbon and form a structurally intact composite. Cycle times were 12 h. Amorphous densities approaching 60-70 % of theory (rule of mixtures) were achieved with the fewest PIP cycles by the application of vacuum to the samples before infiltration, the use of pressure to infiltrate the samples and increasing the ceramic content of the precursor solution. Strontium aluminosilicate (SAS) was added to promote the hexagonal to monoclinic phase transformation.

Hinklin, T.R.; Neo, Siew Siang; Chew, K.W.; Laine, R.M. [Univ. of Michigan, Ann Arbor, MI (United States)

1996-12-31

240

29Si NMR study of structural ordering in aluminosilicate geopolymer gels.  

PubMed

A systematic series of aluminosilicate geopolymer gels was synthesized and then analyzed using 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR) in combination with Gaussian peak deconvolution to characterize the short-range ordering in terms of T-O-T bonds (where T is Al or Si). The effect of nominal Na2O/(Na2O + K2O) and Si/Al ratios on short-range network ordering was quantified by deconvolution of the 29Si MAS NMR spectra into individual Gaussian peaks representing different Q4(mAl) silicon centers. The deconvolution procedure developed in this work is applicable to other aluminosilicate gel systems. The short-range ordering observed here indicates that Loewenstein's Rule of perfect aluminum avoidance may not apply strictly to geopolymeric gels, although further analyses are required to quantify the degree of aluminum avoidance. Potassium geopolymers appeared to exhibit a more random Si/Al distribution compared to that of mixed-alkali and sodium systems. This work provides a quantitative account of the silicon and aluminum ordering in geopolymers, which is essential for extending our understanding of the mechanical strength, chemical and thermal stability, and fundamental structure of these systems. PMID:15779981

Duxson, Peter; Provis, John L; Lukey, Grant C; Separovic, Frances; van Deventer, Jannie S J

2005-03-29

241

White light emission from Sm3+/Tb3+ codoped oxyfluoride aluminosilicate glasses under UV light excitation  

NASA Astrophysics Data System (ADS)

In this paper, we report on the absorption and photoluminescence properties of oxyfluoride aluminosilicate and boro-aluminosilicate glasses codoped with Sm3+ and Tb3+ ions. The differential thermal analysis profiles of these glasses have been obtained to confirm their thermal stability. From the measured absorption spectrum, Judd-Ofelt (J-O) intensity parameters (?2, ?4 and ?6) have been evaluated for the Sm3+ ion. When excited by ultraviolet light these glasses emit a combination of blue, green and orange-red wavelengths forming white light. The ratio of the intensities of orange-red to green emissions can be tuned by varying both the concentration of the Sm3+ ion and the composition of the glass matrix. The excitation and emission spectra have shown a self-quenching effect for the Sm3+ ions and an efficient energy transfer from Tb3+ : 5D4 ? Sm3+ : 4G5/2 was observed which was also confirmed by the decay lifetime measurements.

Lakshminarayana, G.; Yang, R.; Qiu, J. R.; Brik, M. G.; Kumar, G. A.; Kityk, I. V.

2009-01-01

242

A HIGH CURRENT DENSITY LI+ ALUMINO-SILICATE ION SOURCE FOR TARGET HEATING EXPERIMENTS  

SciTech Connect

The NDCX-II accelerator for target heating experiments has been designed to use a large diameter ({approx_equal} 10.9 cm) Li{sup +} doped alumino-silicate source with a pulse duration of 0.5 {micro}s, and beam current of {approx_equal} 93 mA. Characterization of a prototype lithium alumino-silicate sources is presented. Using 6.35mm diameter prototype emitters (coated on a {approx_equal} 75% porous tungsten substrate), at a temperature of {approx_equal} 1275 C, a space-charge limited Li{sup +} beam current density of {approx_equal} 1 mA/cm{sup 2} was measured. At higher extraction voltage, the source is emission limited at around {approx_equal} 1.5 mA/cm{sup 2}, weakly dependent on the applied voltage. The lifetime of the ion source is {approx_equal} 50 hours while pulsing the extraction voltage at 2 to 3 times per minute. Measurements show that the life time of the ion source does not depend only on beam current extraction, and lithium loss may be dominated by neutral loss or by evaporation. The life time of a source is around {ge} 10 hours in a DC mode extraction, and the extracted charge is {approx_equal} 75% of the available Li in the sample. It is inferred that pulsed heating may increase the life time of a source.

Roy, Prabir K.; Greenway, Wayne G.; Kwan, Joe W.; Seidl, Peter A.; Waldron, William L.

2011-03-23

243

Crystalline titanate catalyst supports  

DOEpatents

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.

Anthony, R.G.; Dosch, R.G.

1993-01-05

244

Crystalline titanate catalyst supports  

DOEpatents

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.

Anthony, Rayford G. (Bryan, TX); Dosch, Robert G. (Albuquerque, NM)

1993-01-01

245

CO2 SEPARATIONS USING ZEOLITE MEMBRANES  

SciTech Connect

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, C

Richard D. Noble; John L. Falconer

2001-06-30

246

Chemical Interactions in Multimetal/Zeolite Catalysts  

SciTech Connect

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.

Sachtler, Wolfgang M. H.

2004-04-16

247

Foam flotation of zeolites: Application for zinc ion removal  

SciTech Connect

In this paper the solid/liquid separation of a NaY zeolite, a known cation exchanger, was investigated in the laboratory by foam flotation from aqueous suspensions. The main parameters affecting the process in batch experiments, such as the pH of the suspension, the type of collector, the cationic collector concentration, the zeolite concentration, and the ionic strength were examined. The optimum conditions for removal (flotation) of more than 95% of the zeolite were determined. Following flotation of the zeolite in the Na form, zinc ions were chosen to serve as an application for ion exchange by the zeolite (for metal recovery), followed by foam flotation of the exchanged form of the zeolite from solution.

Zouboulis, A.I.; Zamboulis, D.; Matis, K.A. (Aristotle Univ., Thessaloniki (Greece))

1991-01-01

248

Atomic sites and stability of Cs+ captured within zeolitic nanocavities  

PubMed Central

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

Yoshida, Kaname; Toyoura, Kazuaki; Matsunaga, Katsuyuki; Nakahira, Atsushi; Kurata, Hiroki; Ikuhara, Yumi H.; Sasaki, Yukichi

2013-01-01

249

Interaction of Microwaves with Synthetic Type A Zeolite Containing Water  

NASA Astrophysics Data System (ADS)

A synthetic honeycomb type A zeolite adsorbent was regenerated through microwave irradiation in a single-mode cavity microwave at 2.46 GHz. The regeneration mechanism was investigated by comparing the heating properties, thermogravimetric properties, and dielectric properties of the synthetic zeolite samples. The hydrated zeolite sample was easily heated to over 200 C, although a difference in the impedance matching frequency of only 0.01 GHz sharply reduced the maximum heating and increased the regeneration time. The adsorbed water in the hydrated zeolite initially acted as a heating agent by absorbing microwave energy, because the dielectric loss factor of water is higher than that of synthetic zeolite around 2.45 GHz. From 50 to 250 C, the zeolite itself also absorbed microwave energy.

Tanaka, Masahiro; Takayama, Sadatsugu; Sano, Saburo

2013-11-01

250

Modified zeolites as catalysts in the Friedel-Crafts acylation  

Microsoft Academic Search

Modified zeolites were found to be active catalysts in the Friedel-Crafts acylation of anisole by acetyl chloride and acetic anhydride. The effect of two different modifications of the zeolites were tested; lanthanum-exchange and varying the SiAl ratio. For the rare-earth modified zeolites, the activity was found to be dependent on the lanthanum content, and the yield increased with the level

Kristin Gaare; Duncan Akporiaye

1996-01-01

251

Transesterification of soybean oil with zeolite and metal catalysts  

Microsoft Academic Search

Transesterification of soybean oil with methanol was carried out at 60, 120, and 150C in the presence of a series NaX faujasite zeolite, ETS-10 zeolite, and metal catalysts. The stock zeolites were exchanged with potassium and cesium; NaX containing occluded sodium oxide (NaOx\\/NaX) and occluded sodium azide (NaOx\\/NaX*). The catalysts were calcined at 500C prior to use in order to

Galen J. Suppes; Mohanprasad A. Dasari; Eric J. Doskocil; Pratik J. Mankidy; Michael J. Goff

2004-01-01

252

Treatment of Acid Mine Drainage Using Fly Ash Zeolite  

Microsoft Academic Search

In this paper, two Indian fly ashes (from Talcher and Ramagundam) were converted into zeolites and both the raw fly ash and\\u000a zeolite were used to treat two British acidic mine waters. The results demonstrate that fly ash zeolites are more effective\\u000a than raw fly ash for treatment of acid mine drainage. Fly ash has been found effective for removal

Bably Prasad; Robert J. G. Mortimer

2011-01-01

253

Molten-salt method for the synthesis of zeolitic materials  

Microsoft Academic Search

The molten-salt method has been applied for the zeolitization of fly ash and other mineral wastes. Fly ash was converted into zeolitic materials by a simple thermal treatment at molten states of some salt mixtures without any addition of water. Various combinations of salt mixtures were employed for the zeolitization of fly ash, using NaOH, KOH, or NH4F as mineralizer,

Man Park; Choong Lyeal Choi; Woo Taik Lim; Myung Chul Kim; Jyung Choi; Nam Ho Heo

2000-01-01

254

Molten-salt method for the synthesis of zeolitic materials  

Microsoft Academic Search

Characterization of zeolitic materials synthesized by the newly developed molten-salt method was carried out. Their physicochemical properties were investigated and compared to those of zeolitic materials prepared by the conventional hydrothermal method. The molten-salt method exhibited much less elemental loss during the zeolitization process. The product yield based on the reaction weight was about twice as high in the molten-salt

Man Park; Choong Lyeal Choi; Woo Taik Lim; Myung Chul Kim; Jyung Choi; Nam Ho Heo

2000-01-01

255

Characterization of Y zeolites using sodium-23 MASNMR  

Microsoft Academic Search

Y zeolites have engendered a great deal of interest because of their large pore structure. As a result, considerable characterization work has been performed on the silica-alumina framework of Y and other zeolites. For example, the dealumination of Y zeolite has been extensively studied using various techniques including silicon-29 NMR, aluminum-27 NMR, and STEM\\/EDX analysis. In contrast, the characterization of

L. B. Welsh; S. L. Lambert

1988-01-01

256

Large zeolites - Why and how to grow in space  

NASA Technical Reports Server (NTRS)

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.

Sacco, Albert, Jr.

1991-01-01

257

Cobalt nanoparticles prepared in faujasite zeolites by borohydride reduction  

Microsoft Academic Search

Metallic cobalt nanoparticles have been prepared in the faujasite zeolite by the reduction of the Co2+-exchanged zeolite with sodium borohydride aqueous solutions. The influences of the temperature used for treating the Co2+-faujasite zeolite before reduction and the concentration of NaBH4 solution on the degree of reduction and the size of cobalt particles have been investigated. Although the treatment of the

Ye Wang; Hongli Wu; Qinghong Zhang; Qinghu Tang

2005-01-01

258

Non-Crystalline Cellulose and Production Thereof.  

National Technical Information Service (NTIS)

A non crystalline or low crystallinity cellulose. A method of making a non crystalline or low crystallinity cellulose comprising providing cellulosic material, adding an effective acid in an amount effective to at least wet the cellulosic material, mixing...

H. M. Harraz, Y. Y. Lee

2005-01-01

259

Prevention of aflatoxicosis in farm animals by Means of hydrated sodium calcium aluminosilicate addition to feedstuffs: a review  

Microsoft Academic Search

Mycotoxins are a wide group of fungal toxins that have been associated with severe toxic effects in man and animals. Aflatoxins are the most dangerous of these fungal secondary metabolites. Because there is no definitive way in which complete detoxification of food and feed contaminated with mycotoxins can be achieved, new methods to eliminate mycotoxicosis are sought.Hydrated sodium calcium aluminosilicate

A. J. Ramos; E. Hernndez

1997-01-01

260

Cyclohexane Dehydrogenation Using an Economical Iron Catalyst: Influence of AluminoSilicate Structure on the Catalytic Activity  

Microsoft Academic Search

The effect of mixing both local Egyptian hematitic ore and activated aluminosilicate material (bentonite clay) on the dehydrogenation activity of the former was studied.Three mixtures were prepared in which bentonite percentages were 10, 20, and 40 wt%. Cyclohexane used as a model reactant for the catalytic dehydrogenation reaction carried out in catalytic flow system within reaction temperature ranged from 150

T. Zaki

2005-01-01

261

Structural characterization of water-bearing silicate and aluminosilicate glasses by high-resolution solid-state NMR  

E-print Network

Structural characterization of water-bearing silicate and aluminosilicate glasses by high obtained for sodium tetrasilicate and phonolite glasses suggests that the water incorporation mechanisms as to completely exclude any of the different previously proposed models for water incorporation in silicate

Boyer, Edmond

262

Zeolite Crystal Growth in Microgravity and on Earth  

NASA Technical Reports Server (NTRS)

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.

2003-01-01

263

Alkylation of o-toluidine with methanol over acidic zeolites  

Microsoft Academic Search

The catalytic property of H-beta zeolite in the methylation of o-toluidine was compared to that of other acidic zeolites, viz. HY, H-MOR, H-ZSM-5 and H-FER. The H-beta catalyst showed higher conversion of o-toluidine, the main product being 2,4-xylidine. The selectivity towards 2,4-dimethylaniline (2,4-xylidine) was about 69% (at 400C) over H-beta zeolite and was selective than the other zeolites under study.

R Anand; R Maheswari; S. G Hegde; B. S Rao

2003-01-01

264

[Crystalline polymorphism of eflucimibe].  

PubMed

The importance, in therapeutics, of the concept of bioavailability and on-going quality research in the formulation of a drug has prompted us to examine the crystalline polymorphism of eflucimibe as from the research phase. This study has been carried out by re-crystallization of the product in organic solvents having a different polarity in a variety of experimental temperature and pressure conditions, then, subsequently, by re-cooling the previously dissolved substance. The analytical methods applied to identify and then describe the polymorphic forms are thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), X-ray powder diffraction from synchrotron radiation (XRPD), infrared spectrometry (IR), solid-state nuclear magnetic resonance spectrometry (SSNMR) and lastly maximum solubility measurements. By means of XRPD, two polymorphic forms called A and B have been clearly identified at ambient temperature. These two crystalline forms were obtained in a reproducible way, then described by DSC, XRPD, IR and SSNMR. Differential scanning calorimetry analysis has shown for polymorphic form A two endothermic phenomena with low energy at about 35 masculine and 118 degrees C attributed by XRDP to conformational polymorphism. The complex endothermic event that extends between 75 masculine and 105 degrees C appears to correspond to successive alterations of a lamellar structure. The solid-solid transition observed at 110 degrees C is due to a change of crystalline phase, then the melting point occurring at about 130 degrees C. For form B, two changes of crystalline phase are clearly observed at about 80 masculine and 120 degrees C. The reversibility of these changes was observed by thermomicroscopy in polarized light. Form A, which is less soluble in absolute ethanol than form B, is the more stable thermodynamically in the temperature range from 25 masculine to 50 degrees C where the data have been obtained. The Van't Hoff diagram layout for each polymorphic form appears to reveal an A<-->B transition temperature in a temperature range lower than 25 degrees C. This study, undertaken as from the research phase, has enabled us to highlight the polymorphism of this new chemical entity by means of XRDP by explaining the nature of the endothermic phenomena observed by DSC, and lastly identify the thermodynamically more stable polymorphic form, thus contributing to a better knowledge of this future drug. PMID:12050596

Ribet, J P; Pena, R; Chauvet, A; Patoiseau, J F; Autin, J M; Segonds, R; Basquin, M; Autret, J M

2002-05-01

265

Preparation and characterization of cesium-137 aluminosilicate pellets for radioactive source applications  

SciTech Connect

Twenty-seven fully loaded /sup 137/Cs aluminosilicate pellets were fabricated in a hot cell by the vacuum hot pressing of a cesium carbonate/montmorillonite clay mixture at 1500/sup 0/C and 570 psig. Four pellets were selected for characterization studies which included calorimetric measurements, metallography, scanning electron microscope and electron backscattering (SEM-BSE), electron microprobe, x-ray diffraction, and cesium ion leachability measurements. Each test pellet contained 437 to 450 curies of /sup 137/Cs as determined by calorimetric measurements. Metallographic examinations revealed a two-phase system: a primary, granular, gray matrix phase containing large and small pores and small pore agglomerations, and a secondary fused phase interspersed throughout the gray matrix. SEM-BSE analyses showed that cesium and silicon were uniformly distributed throughout both phases of the pellet. This indicated that the cesium-silicon-clay reaction went to completion. Aluminum homogeneity was unconfirmed due to the high background noise associated with the inherent radioactivity of the test specimens. X-ray diffraction analyses of both radioactive and non-radioactive aluminosilicate pellets confirmed the crystal lattice structure to be pollucite. Cesium ion quasistatic leachability measurements determined the leach rates of fully loaded /sup 137/Cs sectioned pollucite pellets to date to be 4.61 to 34.4 x 10/sup -10/ kg m/sup -2/s/sup -1/, while static leach tests performed on unsectioned fully loaded pellets showed the leach rates of the cesium ion to date to be 2.25 to 3.41 x 10/sup -12/ kg m/sup -2/s/sup -1/. The cesium ion diffusion coefficients through the pollucite pellet were calculated using Fick's first and second laws of diffusion. The diffusion coefficients calculated for three tracer level /sup 137/Cs aluminosilicate pellets were 1.29 x 10/sup -16/m/sup 2/s/sup -1/, 6.88 x 10/sup -17/m/sup 2/s/sup -1/, and 1.35 x 10/sup -17/m/sup 2/s/sup -1/, respectively.

Schultz, F.J.; Tompkins, J.A.; Haff, K.W.; Case, F.N.

1981-07-01

266

The Valence State of Silicon and Redox Dynamics in Aluminosilicate Melts  

NASA Astrophysics Data System (ADS)

Physicists have long been aware of the many valence states of Si and the roles these play in the kinetics of thermal oxidation of Si single crystals and the molecular structure of the amorphous oxide film (e.g., Borman et al., 1991). Similarly, the dynamics of oxidation and of vaporization of SiC are also affected by the presence of Si2+ in the amorphous silica surface film (e.g., Dunham et al., 1998; Mendybaev et al., 2002). Nevertheless, Si2+,4+ heterovalency is little considered in redox studies of silicate melts as reported in the petrology literature. We have performed experiments in which a liquid bronze (Cu,Sn) alloy was reacted with (1) a magnesium aluminosilicate melt and (2) a Zn2+-doped magnesium aluminosilicate melt, all done at a low oxygen fugacity (sufficient to keep the metal alloy from oxidizing in reaction with the gas environment). The driving potential for metal melt-silicate melt reaction has two components: (a) reduction of the silicate melt and oxidation of the metal alloy; (b) formation of a homogeneous silicate solution that incorporates ionic Cu and Sn. The reaction morphologies present compelling evidence that Si4+ in the silicate melt is reduced in part to Si2+, initially so as to incorporate Cu+,2+ into the melt; as the reaction proceeds, however, the Si2+ mobility becomes important in charge-compensation of the "inward" flux of Sn2+. Addition of Zn2+ to the starting silicate melt forces a spatially periodic variation in the silicate melt structure (as suggested by the chemistry) as the reaction proceeds. In separate experiments, reduction of an FeO-bearing calcium-magnesium aluminosilicate melt in a CO-rich environment creates a reaction morphology suggestive of reduction of Si4+ to facilitate the incorporation of carbonate ions into the melt. These experiments are perhaps exotic; nevertheless, they provoke the consideration of the potential role(s) played by silicon valence in any "self-buffering" process associated with the evolution of planetary interiors. Borman et al., Phys. Rev. Lett. 67:2387-2390 (1991). Dunham et al., Mater. Sci. Forum 264-2:391-394 (1998). Mendybaev et al., Geochim. Cosmochim. Acta 66:661-682 (2002).

Cooper, R. F.; Pettersen, C.; Everman, R. L.

2005-12-01

267

Reactive oxygen species mediated DNA damage in human lung alveolar epithelial (A549) cells from exposure to non-cytotoxic MFI-type zeolite nanoparticles.  

PubMed

Increasing utilization of engineered nanoparticles in the field of electronics and biomedical applications demands an assessment of risk associated with deliberate or accidental exposure. Metal based nanoparticles are potentially most important of all the nanoparticles in terms of health risks. Microporous alumino-silicates and pure silicates named as zeolites and zeo-type materials with variety of structures, chemical compositions, particle sizes and morphologies have a significant number of industrial uses such as in catalysis, sorption and ion-exchange processes. In particular, the nanosized particles due to their unique properties are used in hybrid organic-inorganic materials for photography, photonics, electronics, labeling, imaging, and sensing. The aim of the current study is to investigate pure silica MFI-type zeolites nanoparticles with sizes of 50nm and 100nm (samples MFI-50 and MFI-100) under suspended conditions and their toxicological effects on human lung alveolar (A549) cells under in vitro conditions. Live cell imaging showed that the nanoparticles precipitated from the colloidal suspension of cell culture media as large agglomerates, coming in contact with the cell surface through sedimentation. A cellular proliferative capacity test showed the zeolite nanoparticles to exhibit no significant cytotoxicity below a concentration of 100?g/ml. However, both the MFI-50 and MFI-100 nanoparticles induced high intracellular reactive oxygen species (ROS) generation and elevated mitochondrial membrane potential in the A549 cells over the measured time period of 12h and at concentrations up to ?50?g/ml. DNA fragmentation analysis using the comet assay showed that the MFI-50 and MFI-100 nanoparticles cause genotoxicity in a concentration dependent manner. Furthermore, the rate at which maximum genomic damage was caused by MFI-100 nanoparticles in the A549 cells was found to be high as compared to the MFI-50 nanoparticles. However, the damage caused by the MFI-50 nanoparticles was found to accumulate over a longer period of time as compared to MFI-100 nanoparticles. The study therefore points towards the capability of the non-cytotoxic zeolite nanoparticles to induce oxidative stress resulting in short-term altered cellular metabolism up-regulation and genomic instability. Although the damage was found to be short-lived, its persistence over longer durations, or stabilization cannot be neglected. Further studies are in progress to yield a better understanding of the mechanisms for oxidative stress and resulting cascade of events leading to genetic damage in the human lung alveolar epithelial cells following exposure to zeolite nanoparticles of different sizes. PMID:23103338

Bhattacharya, Kunal; Naha, Pratap C; Naydenova, Izabela; Mintova, Svetlana; Byrne, Hugh J

2012-12-17

268

Three Mile Island zeolite vitirification demonstration program  

Microsoft Academic Search

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

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

1981-01-01

269

Dehydrogenation of Light Alkanes over Zeolites  

Microsoft Academic Search

The conversion of light paraffins to olefins and the secondary reactions of the unsaturated compounds were investigated on H-ZSM5 and H-Y zeolites between 733 and 823 K. Steady state- and transient response-isotope tracing studies revealed that two mechanisms of dehydrogenation are operative. The main pathway is represented by monomolecular, protolytic dehydrogenation. This reaction contributes most to steady state olefin production.

Thomas F. Narbeshuber; Axel Brait; Kulathuyier Seshan; Johannes A. Lercher

1997-01-01

270

Quantitatively probing the Al distribution in zeolites.  

PubMed

The degree of substitution of Si(4+) by Al(3+) in the oxygen-terminated tetrahedra (Al T-sites) of zeolites determines the concentration of ion-exchange and Brnsted acid sites. Because the location of the tetrahedra and the associated subtle variations in bond angles influence the acid strength, quantitative information about Al T-sites in the framework is critical to rationalize catalytic properties and to design new catalysts. A quantitative analysis is reported that uses a combination of extended X-ray absorption fine structure (EXAFS) analysis and (27)Al MAS NMR spectroscopy supported by DFT-based molecular dynamics simulations. To discriminate individual Al atoms, sets of ab initio EXAFS spectra for various T-sites are generated from DFT-based molecular dynamics simulations, allowing quantitative treatment of the EXAFS single- and multiple-photoelectron scattering processes out to 3-4 atom shells surrounding the Al absorption center. It is observed that identical zeolite types show dramatically different Al distributions. A preference of Al for T-sites that are part of one or more 4-member rings in the framework over those T-sites that are part of only 5- and 6-member rings in an HBEA150 zeolite has been determined using this analysis. PMID:24815517

Vjunov, Aleksei; Fulton, John L; Huthwelker, Thomas; Pin, Sonia; Mei, Donghai; Schenter, Gregory K; Govind, Niranjan; Camaioni, Donald M; Hu, Jian Zhi; Lercher, Johannes A

2014-06-11

271

Chemical durability of soda-lime-aluminosilicate glass for radioactive waste vitrification  

SciTech Connect

Vitrification has been identified as one of the most viable waste treatment alternatives for nuclear waste disposal. Currently, the most popular glass compositions being selected for vitrification are the borosilicate family of glasses. Another popular type that has been around in glass industry is the soda-lime-silicate variety, which has often been characterized as the least durable and a poor candidate for radioactive waste vitrification. By replacing the boron constituent with a cheaper substitute, such as silica, the cost of vitrification processing can be reduced. At the same time, addition of network intermediates such as Al{sub 2}O{sub 3} to the glass composition increases the environmental durability of the glass. The objective of this study is to examine the ability of the soda-lime-aluminosilicate glass as an alternative vitrification tool for the disposal of radioactive waste and to investigate the sensitivity of product chemical durability to variations in composition.

Eppler, F.H.; Yim, M.S. [North Carolina State Univ., Raleigh, NC (United States)

1998-09-01

272

A facile strategy to recycle template P123 from mesoporous aluminosilicates by ultrasonic extraction.  

PubMed

High synthesis cost of mesoporous aluminosilicates (MA) limits their practical application. Recycling of copolymer template employed in preparation of MA is an effective way to reduce the synthesis cost. An ultrasonic extraction strategy for recycling of organic template P123 in MAs is reported. Effects of different extraction parameters on P123 recovery are investigated and the optimum conditions are obtained. 75.0% P123 is recovered from MAs within 10 min by one-step ultrasonication. Characterizations indicated that the resulting P123-free MA (MA-U) exhibits excellent properties compared with that of calcined products. Moreover, recovered P123 can be employed to synthesize high hydrothermally stable MA. This investigation provides a facile strategy to recycle P123 from MA. PMID:24703432

Jin, Jun-su; Cao, Li; Su, Guang-xun; Xu, Chun-yan; Zhang, Ze-ting; Gao, Xiong-hou; Liu, Hong-hai; Liu, Hong-tao

2014-09-01

273

Advanced analyses of 57Fe Mssbauer data of alumino-silicate glasses  

NASA Astrophysics Data System (ADS)

57Fe Mssbauer spectra of iron bearing alumino-silicate glasses are analysed by two complementary methods (SID and x-VBF) especially adapted for the analysis of disordered systems by taking into account distributions of hyperfine Mssbauer parameters. Qualitative and quantitative information about the oxidation state of iron are obtained as well as information about the distribution of local environments of iron. The possibility to separate the signal of ferric iron from that of ferrous iron allows to derive precise redox ratio in favourable cases but also to analyse more sharply the different contributions to Mssbauer spectra. Using two different glass series (feldspar composition, haplo-tonalitic composition), the characteristics of the two methods are described and employed to study the effect of composition, water incorporation and oxidation state on the glass structure. Optical absorption spectroscopy is used to support the interpretation of the Mssbauer spectra in case of the feldspar glasses.

Rossano, S.; Behrens, H.; Wilke, M.

2008-03-01

274

Effect of High Temperatures on the Properties of Alkali Activated Aluminosilicate with Electrical Porcelain Filler  

NASA Astrophysics Data System (ADS)

The effect of thermal pre-treatment up to 1,200C on the structure and properties of alkali-activated aluminosilicate material containing electrical porcelain filler is analyzed in this article. The material is found to have very good high-temperature resistance. The reasons for its positive response to high-temperature exposure are, on one hand, the formation and subsequent crystallization of akermanite, and on the another hand, melting of electrical porcelain filler in the alkali environment at about 1,150C and its subsequent reaction with the porous matrix resulting in formation of ceramic bonds. The combination of these two positive effects complementing each other in the formation of a new structure is responsible for the structure compaction indicated by the sudden decrease in porosity and is manifested in quite remarkable improvement of mechanical properties.

Zuda, Lucie; Rovnank, Pavel; Bayer, Patrik; ?ern, Robert

2008-04-01

275

Synthesis and characterization of inorganic polymers from the alkali activation of an aluminosilicate  

NASA Astrophysics Data System (ADS)

This paper presents the results of the synthesis and characterization of inorganic polymers (IP) from aluminosilicates: bentonite (BT) and pumice (PP). The synthesis of IP, was carried out by two methods involving alkaline activation, at room temperature and 80 5 C, using as activating agent sodium silicate both commercial and analytical (Na2SiO3). Sodium hydroxide (NaOH) at 3 M, 7 M and 12 M was added. A lower degree of polymerization was obtained by using analytical precursors subjected to room temperature and 80 5C. Replacement of heating by the use of the commercial activating agent with greater alkalinity allows the formation of a 3D network. The materials were structurally characterized by FTIR spectroscopy with Attenuated Reflectance (ATR), Scanning Electron Microscope (SEM) and X -ray diffraction (DRX).

Gonzlez, C. P.; Montao, A. M.; Gonzlez, A. K.; Ros, C. A.

2014-06-01

276

Structure and properties of sodium aluminosilicate glasses from molecular dynamics simulations  

NASA Astrophysics Data System (ADS)

Addition of alumina to sodium silicate glasses considerably improves the mechanical properties and chemical durability and changes other properties such as ionic conductivity and melt viscosity. As a result, aluminosilicate glasses find wide industrial and technological applications including the recent Corning Gorilla Glass. In this paper, the structures of sodium aluminosilicate glasses with a wide range of Al/Na ratios (from 1.5 to 0.6) have been studied using classical molecular dynamics simulations in a system containing around 3000 atoms, with the aim to understand the structural role of aluminum as a function of chemical composition in these glasses. The short- and medium-range structures such as aluminum coordination, bond angle distribution around cations, Qn distribution (n bridging oxygen per network forming tetrahedron), and ring size distribution have been systematically studied. In addition, the mechanical properties including bulk, shear, and Young's moduli have been calculated and compared with experimental data. It is found that aluminum ions are mainly four-fold coordinated in peralkaline compositions (Al/Na < 1) and form an integral part of the rigid silicon-oxygen glass network. In peraluminous compositions (Al/Na > 1), small amounts of five-fold coordinated aluminum ions are present while the concentration of six-fold coordinated aluminum is negligible. Oxygen triclusters are also found to be present in peraluminous compositions, and their concentration increases with increasing Al/Na ratio. The calculated bulk, shear, and Young's moduli were found to increase with increasing Al/Na ratio, in good agreement with experimental data.

Xiang, Ye; Du, Jincheng; Smedskjaer, Morten M.; Mauro, John C.

2013-07-01

277

Low-temperature synthesized aluminosilicate glasses: Part III Influence of the composition of the silicate solution on production, structure and properties  

Microsoft Academic Search

The low-temperature reaction between an aqueous sodium or potassium silicate solution and metakaolinite yields a solid aluminosilicate.\\u000a The influence of the molar ratios H2O\\/R2O (between 6.6 and 21.0) and SiO2\\/R2O (between 0.0 and 2.3) of the silicate solution (R=Na or K) on the aluminosilicate's production, on the reaction stoichiometry\\u000a and on the aluminosilicate's molecular structure is studied with differential scanning

H. RAHIER; W. SIMONS; B. VAN MELE; M Biesemans

1997-01-01

278

Infrared spectroscopic characterization of dehydration and accompanying phase transition behaviors in NAT-topology zeolites  

SciTech Connect

Relative humidity (PH2O, partial pressure of water)-dependent dehydration and accompanying phase transitions in NAT-topology zeolites (natrolite, scolecite, and mesolite) were studied under controlled temperature and known PH2O conditions by in situ diffuse-reflectance infrared Fourier transform spectroscopy and parallel X-ray powder diffraction. Dehydration was characterized by the disappearance of internal H2O vibrational modes. The loss of H2O molecules caused a sequence of structural transitions in which the host framework transformation path was coupled primarily via the thermal motion of guest Na?/Ca2? cations and H2O molecules. The observation of different interactions of H2O molecules and Na?/Ca2? cations with host aluminosilicate frameworks under highand low-PH2O conditions indicated the development of different local strain fields, arising from cation H2O interactions in NAT-type channels. These strain fields influence the Si O/Al O bond strength and tilting angles within and between tetrahedra as the dehydration temperature is approached. The newly observed infrared bands (at 2,139 cm-1 in natrolite, 2,276 cm-1 in scolecite, and 2,176 and 2,259 cm-1 in mesolite) result from strong cation H2O Al Si framework interactions in NAT-type channels, and these bands can be used to evaluate the energetic evolution of Na?/Ca2? cations before and after phase transitions, especially for scolecite and mesolite. The 2,176 and 2,259 cm-1 absorption bands in mesolite also appear to be related to Na?/Ca2? order disorder that occur when mesolite loses its Ow4 H2O molecules.

Wang, Hsiu-Wen [ORNL; Bishop, David [ORNL

2012-01-01

279

Catalytic processes in the presence of zeolites of increased internal acid activity and decreased external acid activity  

SciTech Connect

A process is described for aromatizing a C[sub 2+] aliphatic hydrocarbon stream in the presence of a catalyst which comprises ZSM-5 which becomes coked and deactivated during a catalytic aromatization cycle, the improvement comprising reducing production of coke, and increasing product yield by contacting said C[sub 2+] aliphatic hydrocarbon with a zeolite catalyst, in acid form, consisting of a silicate exhibiting the X-ray diffraction pattern of ZSM-5, and recovering a product effluent which comprises benzene, toluene, and at least one xylene selected from the group consisting of o-xylene, m-xylene, and p-xylene, wherein the silicate is formed by a method consisting essentially of the steps of providing as a reactant an aluminosilicate exhibiting the X-ray diffraction pattern of an ZSM-5 wherein said reactant exhibits an alpha value which is effective to crack hydrocarbons under cracking conditions and exhibits an activity to dealkylate 1,3,5-tri-t-butylbenzene, as measured by the rate of dealkylation of 1,3,5-tri-t-butylbenzene in the presence of said reactant; treating the reactant, in hydrogen form, with a solution of nitric acid at reflux temperature or lower; and recovering said silicate; which silicate exhibits an alpha value greater than that of said reactant and a rate for dealkylation of 1,3,5-tri-t-butylbenzene which is less than that rate of dealkylation of 1,3,5-tri-t-butylbenzene by said reactant.

Rodewald, P.G.

1993-06-15

280

Single crystalline magnetite nanotubes.  

PubMed

We descried a method to synthesize single crystalline Fe3O4 nanotubes by wet-etching the MgO inner cores of MgO/Fe3O4 core-shell nanowires. Homogeneous Fe3O4 nanotubes with controllable length, diameter, and wall thickness have been obtained. Resistivity of the Fe3O4 nanotubes was estimated to be approximately 4 x 10-2 Omega cm at room temperature. Magnetoresistance of approximately 1% was observed at T = 77 K when a magnetic field of B = 0.7 T was applied. The synthetic strategy presented here may be extended to a variety of materials such as YBCO, PZT, and LCMO which should provide ideal candidates for fundamental studies of superconductivity, piezoelectricity, and ferromagnetism in nanoscale structures. PMID:15631421

Liu, Zuqin; Zhang, Daihua; Han, Song; Li, Chao; Lei, Bo; Lu, Weigang; Fang, Jiye; Zhou, Chongwu

2005-01-12

281

Synthesis of zeolites from coal fly ash: an overview  

Microsoft Academic Search

Coal combustion by-products production in USA and EU is estimated in around 115 million tons per year. A large portion of this production is accounted for the coal fly ash (CFA). Cement and concrete manufacturing consumes most of the CFA produced. Zeolite synthesized from CFA is a minor but interesting product, with high environmental applications. Zeolites may be easily obtained

X Querol; N Moreno; J. C Umaa; A Alastuey; E Hernndez; A Lpez-Soler; F Plana

2002-01-01

282

Transport properties of alkanes through ceramic thin zeolite MFI membranes  

Microsoft Academic Search

Polycrystalline randomly oriented defect free zeolite layers on porous ?-Al2O3 supports are prepared with a thickness of less than 5 ?m by in situ crystallisation of silicalite-1. The flux of alkanes is a function of the sorption and intracrystalline diffusion. In mixtures of strongly and weakly adsorbing gases and a high loadings of the strongly adsorbing molecule in the zeolite

Z. A. E. P. Vroon; K. Keizer; M. J. Gilde; H. Verweij; A. J. Burggraaf

1996-01-01

283

Fission product removal from molten salt using zeolite  

Microsoft Academic Search

Spent nuclear fuel (SNF) can be treated in a molten salt electrorefiner for conversion into metal and mineral waste forms for geologic disposal. The fuel is dissolved in molten chloride salt. Non-transuranic fission products in the molten salt are ion-exchanged into zeolite A, which is subsequently mixed with glass and consolidated. Zeolite was found to be effective in removing fission

C. Pereira; B. D. Babcock

1996-01-01

284

Ion exchange in a zeolite-molten chloride system  

SciTech Connect

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%.

Woodman, R.H.; Pereira, C. [Argonne National Lab., IL (United States). Chemical Technology Div.

1997-07-01

285

ZEOLITE SYNTHESIS FROM PAPER SLUDGE ASH VIA ACID LEACHING  

Microsoft Academic Search

Paper sludge ash (PSA) typically has a low Si abundance and significant Ca content due to the presence of calcite fillers. Acid leaching with HCl was used to reduce the Ca content so that a zeolitic product with a high cation exchange capacity (CEC) could be synthesized. Zeolitic products were synthesized from raw ash and leached ash through reaction with

Takaaki Wajima; Yasuyuki Ikegami

2007-01-01

286

Removal of ammonium from greywater using natural zeolite  

Microsoft Academic Search

This paper focuses on the effectiveness of removing ammonium ion and the theoretical aspects of adsorption including adsorption isotherm, kinetics and thermodynamics as well as desorptionregeneration studies. Results have demonstrated that natural zeolite shows good performance with up to 97% for ammonium removal depending on contact time, zeolite loading, initial ammonium concentration and pH. The adsorption kinetics is best approximated

Nurul Widiastuti; Hongwei Wu; Ha Ming Ang; Dongke Zhang

2011-01-01

287

Radiation induced physical and chemical processes in zeolite materials  

Microsoft Academic Search

Ionic processes induced by high energy radiation in zeolites, including electron and hole trapping and related chemical reactions, are reviewed in this paper. Electronic structures of electrons localized in clusters of charge balancing cations and those solvated in zeolite confined water clusters are characterized by a combination of spectroscopic techniques such as ESR and transient UVvisible absorption. Reactivities of these

Guohong Zhang; Xinsheng Liu; J. Kerry Thomas

1997-01-01

288

A novel urea conductometric biosensor based on zeolite immobilized urease.  

PubMed

A new approach was developed for urea determination where a thin film of silicalite and zeolite Beta deposited onto gold electrodes of a conductometric biosensor was used to immobilize the enzyme. Biosensor responses, operational and storage stabilities were compared with results obtained from the standard membrane methods for the same measurements. For this purpose, different surface modification techniques, which are simply named as Zeolite Membrane Transducers (ZMTs) and Zeolite Coated Transducers (ZCTs) were compared with Standard Membrane Transducers (SMTs). Silicalite and zeolite Beta with Si/Al ratios 40, 50 and 60 were used to modify the conductometric electrodes and to study the biosensor responses as a function of changing zeolitic parameters. During the measurements using ZCT electrodes, there was no need for any cross-linker to immobilize urease, which allowed the direct evaluation of the effect of changing Si/Al ratio for the same type of zeolite on the biosensor responses for the first time. It was seen that silicalite and zeolite Beta added electrodes in all cases lead to increased responses with respect to SMTs. The responses obtained from ZCTs were always higher than ZMTs as well. The responses obtained from zeolite Beta modified ZMTs and ZCTs increased as a function of increasing Si/Al ratio, which might be due to the increased hydrophobicity and/or the acid strength of the medium. PMID:21807206

Kirdeciler, Salih Kaan; Soy, Esin; Oztrk, Sekin; Kucherenko, Ivan; Soldatkin, Oleksandr; Dzyadevych, Sergei; Akata, Burcu

2011-09-15

289

Crewmember working on the mid deck Zeolite Crystal Growth experiment.  

NASA Technical Reports Server (NTRS)

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.

1992-01-01

290

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 ...

291

Zeolites in the Pine Ridge Indian Reservation, South Dakota  

USGS Publications Warehouse

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.

Raymond, William H.; Bush, Alfred L.; Gude, Arthur J., 3rd

1982-01-01

292

Synthesis of zeolite beta in fluoride media under microwave irradiation  

E-print Network

Synthesis of zeolite beta in fluoride media under microwave irradiation Dae Sung Kim a , Jong time of the material significantly, while addition of ammonium fluoride accelerated the crystallization of zeolite beta. In particular, microwave technique combined with fluoride species and seeding led to more

Kim, Ji Man

293

Selective thermal oxidation of hydrocarbons in zeolites by oxygen  

DOEpatents

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.

Frei, Heinz (Berkeley, CA); Blatter, Fritz (Basel, CH); Sun, Hai (Saint Charles, MO)

2000-01-01

294

Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen  

DOEpatents

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.

Frei, Heinz (Berkeley, CA); Blatter, Fritz (Basel, CH); Sun, Hai (Saint Charles, MO)

1999-01-01

295

Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen  

DOEpatents

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.

Frei, Heinz (Berkeley, CA); Blatter, Fritz (Basel, CH); Sun, Hai (Saint Charles, MO)

2001-01-01

296

Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen  

DOEpatents

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.

Frei, H.; Blatter, F.; Sun, H.

1999-06-22

297

Synthesis of A-type zeolite membrane using a plate heater and its formation mechanism  

Microsoft Academic Search

The synthesis of zeolite membrane using a plate heater is described. Attempts have been made to synthesize zeolite membrane either by the static method, which is a typical zeolite synthesis method, or by the circulated solution system. In both methods, the zeolite membrane was selectively formed on the substrate that was heated with a plate heater. Liquid phase solution, which

Satoshi Yamazaki; Kazuo Tsutsumi

2000-01-01

298

KARAKTERISASI KOMPOSISI KIMIA, LUAS PERMUKAAN PORI DAN SIFAT TERMAL DARI ZEOLIT BAYAH, TASIKMALAYA, DAN LAMPUNG  

Microsoft Academic Search

CHARACTERIZATION OF CHEMICAL COMPOSITION, SURFACE AREA PORE, AND THERMAL PROPERTIES OF ZEOLITES FROM BAYAH, TASIKMALAYA, AND LAMPUNG. Characterization of chemical composition, surface area, pore radius, adsorption, and thermal properties of zeolites from Bayah, Tasikmalaya, and Lampung have been performed. The purpose of the characterization is to understand the characteristics of the three zeolites since different types of zeolite will yield

Dian Anggraini; Rosika Kriswarini

2007-01-01

299

Zeolites in Eocene basaltic pillow lavas of the Siletz River Volcanics, Central Coast Range, Oregon.  

USGS Publications Warehouse

Zeolites and associated minerals occur in a tholeiitic basaltic pillow lava sequence. Although the zeolite assemblages are similar to those found in other major zeolite occurrences in basaltic pillow lavas, regional zoning of the zeolite assemblages is not apparent. The formation of the different assemblages is discussed.-D.F.B.

Keith, T.E.C.; Staples, L.W.

1985-01-01

300

Efficient Synthesis of Carbon Nanotubes over Zeolites By Thermal Chemical Vapor Deposition  

NASA Astrophysics Data System (ADS)

Properties of the influence on the zeolite as the support towards the starting carbon materials by using thermal chemical vapor deposition (Thermal-CVD) to produced carbon nanotubes (CNTs) are investigated. The CNTs derived from camphor oil (C10H16O), a botanical hydrocarbon, has been found to be a promising precursor of carbon nanotubes (CNTs). Multi-wall CNTs have been grown from simple pyrolysis of camphor oil in the temperature 650 C in argon atmosphere at normal pressure using zeolite as a supported on Fe/Ni/Mn catalyst. On the other hand, multi-wall nanotubes of uniform diameter (20-30 nm) could be produced with a yield as high as 90%. Structural characterizations have been done by FESEM, and FTIR analyses. Good crystallinity, high purity, and absence of amorphous carbon and metallic particles are the essential features of camphor oil-grown nanotubes; which indirectly may be cost effective. The major parameters are also evaluated in order to obtain high-yield and high-quality CNTs.

Azira, A. A.; Zainal, N. F. A.; Soga, T.; Abdullah, S.; Rusop, M.

2008-05-01

301

Ontogeny of human lens crystallins.  

PubMed

The soluble proteins from prenatal and neonatal human lenses were fractionated by gel filtration into four distinct size classes viz. high molecular weight alpha-crystallin (HM-alpha), alpha-crystallin, intermediate molecular weight (IMW) proteins and low molecular weight (LMW) proteins. Extinction coefficients of the isolated proteins were determined and used to calculate the proportions of each fraction on a weight basis. The distributions of polypeptides within each of these fractions were analyzed by SDS gel electrophoresis and isoelectric focussing, followed by densitometric scanning of the gels. HM-alpha is detectable as early as the 14th week of gestation and its proportions increase rapidly, to about 9% of the total protein in the 1 year postnatal lens. The alpha-crystallin, IMW and LMW fractions show concomitant decreases and by 1 year they represent about 34, 35 and 18%, respectively. However, the proportions of IMW and LMW proteins do not accurately reflect those of the beta- and gamma-crystallins, as is often assumed. Substantial levels of non-crystallin polypeptides were found in the IMW protein fractions, including a group of very basic polypeptides (VBP) which comprised up to one-third of this material in the youngest lenses. Moreover, in postnatal lenses beta s-crystallin accounted for almost half of the LMW proteins. These points considered, alpha-crystallin is the major protein in the neonatal lens (approximately 42%, including HM-alpha), followed by the beta-crystallin (approximately 36% at most and probably less), the gamma-crystallins (approximately 11%) and beta s-crystallin (approximately 9%). Substantial changes in the proportions of specific polypeptides were observed throughout early development. These appear to result from changes at the level of protein synthesis and from postsynthetic modification. The A:B subunit ratio of alpha-crystallin drops from about 12 to below 3 during early development. This coincides with increasing levels of various deamidated and degraded subunits. The major beta-crystallin polypeptide also undergoes rapid deamidation and evidence is presented suggesting that the gamma-crystallins are subject to similar modification. The most dramatic changes were observed in the constituents of the LMW proteins. The synthesis of gamma-crystallins virtually ceases at some time around birth. At the same time, the levels of beta s-crystallin undergo an explosive increase. These and other changes are discussed in terms of their possible functional significance. They are also related to the complex protein status found in old lenses. PMID:4065234

Thomson, J A; Augusteyn, R C

1985-03-01

302

Synthesis and catalytic applications of combined zeolitic/mesoporous materials  

PubMed Central

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

Vernimmen, Jarian; Cool, Pegie

2011-01-01

303

Rheological Influence of Synthetic Zeolite on Cement Pastes  

NASA Astrophysics Data System (ADS)

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.

Baldino, N.; Gabriele, D.; Frontera, P.; Crea, F.; de Cindio, B.

2008-07-01

304

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

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

Kamegawa, Takashi; Ishiguro, Yasushi; Kido, Ryota; Yamashita, Hiromi

2014-01-01

305

Protein adsorption to hydrophobic Zeolite Y: salt effects and application to protein fractionation.  

PubMed

The binding equilibria of proteins with a hydrophobic variety of crystalline Zeolite Y is affected by salt and is a function of the type of salt and its concentration. The behaviour does not always follow the conventional pattern of increased binding at high salt concentrations and varies also for the different proteins involved. The overall process may be looked upon as a salting-in/salting-out mechanism. This material can be used as a surface for the selective adsorption of proteins and has been applied for the fractionation of ox heart homogenate in multi-stage operations. The presence of NaCl influences the protein binding, and this can be seen by monitoring the activity profile of lactate dehydrogenase. The bound protein can be reversed by treating the equilibrium mixture with low-molecular-mass poly(ethylene glycol)s. PMID:8297508

Ghose, S; Mattiasson, B

1993-12-01

306

Zeolitic Materials, Vol. 3, No. 1, December 2002, 29-35 Copyright 2002 Korean Zeolite Association 29  

E-print Network

trend until 0.1 M oxalic acid treatments. In the case of 0.5M and 1M oxalic acid treatments-Alumin > H-ZSM-5 > - Alumina, which was similar trend with the acid strength of catalysts. Zeolites are also to their solid acidity, constricted pore shape and redox property. We have found that beta zeolite exhibit

Kim, Ji Man

307

INTRACELLULAR CRYSTALLINE ERGOSTEROL IN NEUROSPORA  

Microsoft Academic Search

In the fungus Neurospora crassa, hexagonal crystalline inclusions have been observed with both the light and electron microscopes. These crystals have been enriched by differential centrifugation and found to be identical with ergosterol by the criteria of ultraviolet spectral analysis and cytochemical analysis. Observations have been made on the distribution and fine structure of the crystalline bodies in various wild

SEIZO TSUDA; E. L. TATUM

1961-01-01

308

Zeolites as new chromatographic carriers for proteins--easy recovery of proteins adsorbed on zeolites by polyethylene glycol.  

PubMed

Zeolites are able to adsorb proteins on their surface and might be suitable as a new type of chromatographic carrier material for proteins and for their conjugates (Matsui et al., Chem. Eur. J. 7 (2001) 1555-1560). Interestingly, maximum adsorption was observed at the isoelectric point (pI) of each protein. The current study was performed to investigate the desorption of proteins from the zeolites at pI. Proteins adsorbed to zeolites could be desorbed at pI by polyethylene glycol (PEG), but not by conventional eluents. The eluted proteins still retained their activities. The zeolite Na-BEA was an especially good composite for desorption by PEG. Using this method for the adsorption and desorption of proteins at pI, we succeeded in separating various proteins. The application of zeolites to biochemistry and biotechnology is also discussed. PMID:12782034

Chiku, Hiroyuki; Matsui, Masayoshi; Murakami, Shizuka; Kiyozumi, Yoshimichi; Mizukami, Fujio; Sakaguchi, Kengo

2003-07-01

309

Dispersible Exfoliated Zeolite Nanosheets and Their Application as a Selective Membrane  

Microsoft Academic Search

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

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

2011-01-01

310

Characteristics of Lead Sorption by Zeolite Minerals  

NASA Astrophysics Data System (ADS)

Lead adsorption behavior was investigated using four Zeolite minerals (clinoptilolite, analcime, phillipsite and chabazite). The used Pb2+ concentrations were 0, 0.1, 0.5, 1.0, 2.0, 3.0 and 5 mol mL-1. Results indicated that Pb2+ sorption followed the Langmuir adsorption isotherm, but over limited concentration ranges for clinoptilolite and analcime. The bindg energy (Kd) reached, 2.400 and 0.875 g L-1 for phillipsite and chabazite, respectively. The maximum adsorption capacity for such minerals reached 208.33 and 204.08 mg g-1 with correlation coefficient (R2) reached, 0.997 and 0.995, respectively. Meanwhile, two stages for Pb2+adsorption were observed with clinoptilolite and analcime in the low and high concentrations of the applied Pb2+. Data also was applicable to the Freundlich adsorption isotherm over the used entire Pb2+ concentration ranges. The binding energy (n) reached, 1.014, 1.005, 1.001 and 1.001 g L-1 for clinoptilolite, analcime, phillipsite and chabazite, respectively. However, the b values (maximum adsorption capacity) reached 202.582, 201.651, 207.062 and 206.871 mg g-1 with correlation coefficient (R2) nearly one for all studying minerals, respectively. Desorption data indicated that most of the sorbed Pb2+ was extractedin the 1st extraction following the adsorption experiment. The ability of the used zeolite minerals to retain Pb2+ was high and there were differences between the studied minerals in sorption of Pb2+. In conclusion, data eliminated that, zeolite minerals especially, philipsite and chabazite, could be successfully used as packing material in subsurface reactive barriers intercepting ground water plumes and for fixed bed reactors designed to remove Pb2+ from industrial wastewater.

Al-Sewailem, M. S.

311

[Zeolite catalysis in conversion of cellulosics  

SciTech Connect

To transform biomass into fermentable substrate for yeast, we are using zeolites instead of enzymes to catalyze the two bottleneck reactions in biomass conversion, xylose isomerization and ceuobiose hydrolysis. The experimental results on these reactions carried out over various zeolites and other catalysts are presented herein. The advantages and disadvantages of using these catalysts over enzymes are also discussed. Heterogeneous solid catalysts other than zeolites has been employed for cellobiose-to-glucose hydrolysis. The size and shape selectivity that makes zeoutes unique for some reactions can add diffusional hindrance. We have spent some time screening various known solid acidic catalysts. We report that a class of cationic ion exchange resins in the acidified form (e.g. Amberlite) has worked well as an acidic catalyst in hydrolyzing cellobiose to glucose. Our experimental results, together with those obtained from a homogeneous acid catalyst (e.g. sulfuric acid) for comparison are provided. Having succeeded in finding an alternative solid acid catalyst for hydrolysis, we explored other solid resin or other homogeneous but non-enzyme catalyst to carry out the xylose-to-xylulose isomerization. A fairly extensive search has been made. We explored the use of sodium aluminates in the homogeneous phase isomerization of glucose to fructose and obtained a very high conversion of glucose to fructose with the final mixture containing 85% of fructose instead of the common 45%. Fructose apparently complexes with aluminates, and its equilibrium concentration is shifted to considerably higher values than permitted by simple glucose/fructose equilibrium. We have recently found a number of catalysts capable of promoting isomerization between aldoses and ketoses. One solid resin, known as polyvinyl pyridine (PVP), is able to convert xylose to xylulose at a pH below 7. Our usage of alternative isomerization catalysts, including PVP, are described.

Tsao, G.T.

1992-01-01

312

[Zeolite catalysis in conversion of cellulosics  

SciTech Connect

To transform biomass into fermentable substrate for yeast, we are using zeolites instead of enzymes to catalyze the two bottleneck reactions in biomass conversion, xylose isomerization and ceuobiose hydrolysis. The experimental results on these reactions carried out over various zeolites and other catalysts are presented herein. The advantages and disadvantages of using these catalysts over enzymes are also discussed. Heterogeneous solid catalysts other than zeolites has been employed for cellobiose-to-glucose hydrolysis. The size and shape selectivity that makes zeoutes unique for some reactions can add diffusional hindrance. We have spent some time screening various known solid acidic catalysts. We report that a class of cationic ion exchange resins in the acidified form (e.g. Amberlite) has worked well as an acidic catalyst in hydrolyzing cellobiose to glucose. Our experimental results, together with those obtained from a homogeneous acid catalyst (e.g. sulfuric acid) for comparison are provided. Having succeeded in finding an alternative solid acid catalyst for hydrolysis, we explored other solid resin or other homogeneous but non-enzyme catalyst to carry out the xylose-to-xylulose isomerization. A fairly extensive search has been made. We explored the use of sodium aluminates in the homogeneous phase isomerization of glucose to fructose and obtained a very high conversion of glucose to fructose with the final mixture containing 85% of fructose instead of the common 45%. Fructose apparently complexes with aluminates, and its equilibrium concentration is shifted to considerably higher values than permitted by simple glucose/fructose equilibrium. We have recently found a number of catalysts capable of promoting isomerization between aldoses and ketoses. One solid resin, known as polyvinyl pyridine (PVP), is able to convert xylose to xylulose at a pH below 7. Our usage of alternative isomerization catalysts, including PVP, are described.

Tsao, G.T.

1992-12-31

313

Carbon dioxide sensitivity of zeolitic imidazolate frameworks.  

PubMed

Zeolitic imidazolate frameworks of zinc, cobalt, and cadmium, including the framework ZIF-8 commercially sold as Basolite Z1200, exhibit surprising sensitivity to carbon dioxide under mild conditions. The frameworks chemically react with CO2 in the presence of moisture or liquid water to form carbonates. This effect, which has been previously not reported in metal-organic framework chemistry, provides an explanation for conflicting reports on ZIF-8 stability to water and is of outstanding significance for evaluating the potential applications of metal-organic frameworks, especially for CO2 sequestration. PMID:24889776

Mottillo, Cristina; Fri?i?, Tomislav

2014-07-14

314

Growth of large zeolite crystals in space  

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

315

The effect of aluminum, pH, and chemical affinity on the rates of aluminosilicate dissolution reactions  

Microsoft Academic Search

Analysis of aluminosilicate steady-state dissolution\\/precipitation rates indicate that in contrast to what is commonly assumed, the constant pH rates are not independent of chemical affinity at far from equilibrium conditions. Rather, the logarithm of these rates for albite and kaolinite are linear functions of the logarithm of aqueous Al concentration over wide ranges of saturation states. Consideration of both the

Eric H. Oelkers; Jacques Schott; Jean-Luc Devidal

1994-01-01

316

Chemical Compatibility of Barium-Calcium-Aluminosilicate Based Sealing Glasses with Ferritic Stainless Steel Interconnect in SOFCs  

Microsoft Academic Search

In most planar SOFC stack designs, the interconnect, which is typically made from a ferritic stainless steel, is hermitically sealed to the ceramic PEN (Positive electrode-Electrolyte-Negative electrode) by a sealing glass. To maintain the structural stability and minimize degradation of the stack performance, the sealing glass must be chemically compatible with the stainless steel interconnect. In this study, a barium-calcium-aluminosilicate

Zhenguo Yang; Kerry D. Meinhardt; Jeffry W. Stevenson

2003-01-01

317

Probing the molecular-level control of aluminosilicate dissolution: A sensitive solid-state NMR proxy for reactive surface area  

Microsoft Academic Search

For two suites of volcanic aluminosilicate glasses, the accessible and reactive sites for covalent attachment of the fluorine-containing (3,3,3-trifluoropropyl)dimethylchlorosilane (TFS) probe molecule were measured by quantitative 19F nuclear magnetic resonance (NMR) spectroscopy. The first set of samples consists of six rhyolitic and dacitic glasses originating from volcanic activity in Iceland and one rhyolitic glass from the Bishop Tuff, CA. Due

Nancy M. Washton; Susan L. Brantley; Karl T. Mueller

2008-01-01

318

Atmospheric oxidation of the pyritic waste rock in Maardu, Estonia, 2: an assessment of aluminosilicate buffering potential  

Microsoft Academic Search

The assessment of the aluminosilicate buffering potential during acid weathering of the Estonian alum shale is provided.\\u000a It is found that the stoichiometric interaction between dissolved pyrite oxidation products and illite of the shale best describe\\u000a the buffering process and are consistent with earlier field studies. The scheme includes incongruent dissolution of illite\\u000a with smectite and K-jarosite precipitating. This complex

E. Puura; I. Neretnieks

2000-01-01

319

Nuclear magnetic resonance studies of aluminosilicate gels prepared in high-alkaline and salt-concentrated solutions  

Microsoft Academic Search

Solid-state 29Si, 27Al, and 23Na magic angle spinning (MAS) NMR techniques in combination with X-ray powder diffraction (XRD) are used to characterize aluminosilicate gels as a function of composition, pH, and reaction times. These gels were prepared at 80C using initial solutions with low Si\\/Al ratios, high alkaline and salt concentrations that are characteristic of nuclear tank wastes. XRD data

Li-Qiong Wang; Shas V. Mattigod; Kent E. Parker; David T. Hobbs; David E. McCready

2005-01-01

320

Electron transfer reactions within zeolites: Radical cation from benzonorbornadiene  

SciTech Connect

Zeolites are being used as solid acid catalysts in a number of commercial processes. Occasionally zeolites are also reported to perform as electron transfer agents. Recently, we observed that radical cations of certain olefins and thiophene oligomers can be generated spontaneously within ZSM-5 zeolites. We noticed that these radical cations generated from diphenyl polyenes and thiophene oligomers were remarkably stable (at room temperature) within ZSM-5 and can be characterized spectroscopically at leisure. We have initiated a program on electron transfer processes within large pore zeolites. The basis of this approach is that once a cation radical is generated within a large pore zeolite, it will have sufficient room to undergo a molecular transformation. Our aim is to identify a condition under which electron transfer can be routinely and reliably carried out within large pore zeolites such as faujasites. To our great surprise, when benzonorbornadiene A and a number of olefins were included in divalent cation exchanged faujasites. they were transformed into products very quickly (<15 min). This observation allowed us to explore the use of zeolites as oxidants. Results of our studies on benzonorbornadiene are presented in this communication. 16 refs., 1 fig.

Pitchumani, K.; Ramamurthy, V. [Tulane Univ., New Orleans, LA (United States)] [Tulane Univ., New Orleans, LA (United States); Corbin, D.R. [The Du Pont Company, Wilmington, DE (United States)] [The Du Pont Company, Wilmington, DE (United States)

1996-08-28

321

Synthesis of zeolite phases from combustion by-products.  

PubMed

Synthesis of zeolites from combustion by-products, including fly ash, bottom ash and rice husk ash, was studied. A molar ratio of SiO2/Al2O3 of 1.5 was used for the syntheses. Refluxing and hydrothermal methods were also used for synthesis for comparison. The reaction temperatures of refluxing and hydrothermal methods were 100 degrees C and 130 degrees C, respectively. Sodalite, phillipsite-K, and zeolite P1 with analcime were obtained when fly ash, bottom ash and rice husk ash were used as starting materials, respectively. With rice husk ash as a starting material, zeolite P1 was produced. This result had advantages over previous studies as there was no prior activation required for the synthesis. The concentrations and types of alkaline used in the synthesis also determined the zeolite type. The different zeolites obtained from three systems were measured for specific surface area and pore size by using BET and Hg-porosimetry, respectively. Ammonium exchange capacities of the synthesised powders containing zeolites, sodalite, zeolite P1 and phillipsite-K were 38.5, 65.0 and 154.7 meq 100 g(-1), respectively. PMID:20421244

Pimraksa, Kedsarin; Chindaprasirt, Prinya; Setthaya, Naruemon

2010-12-01

322

Zeolite Crystal Growth (ZCG) Flight on USML-2  

NASA Technical Reports Server (NTRS)

The extensive use of zeolites and their impact on the world's economy has resulted in many efforts to characterize their structure, and improve the knowledge base for nucleation and growth of these crystals. The zeolite crystal growth (ZCG) experiment on USML-2 aimed to enhance the understanding of nucleation and growth of zeolite crystals, while attempting to provide a means of controlling the defect concentration in microgravity. Zeolites A, X, Beta, and Silicalite were grown during the 16 day - USML-2 mission. The solutions where the nucleation event was controlled yielded larger and more uniform crystals of better morphology and purity than their terrestrial/control counterparts. The external surfaces of zeolite A, X, and Silicalite crystals grown in microgravity were smoother (lower surface roughness) than their terrestrial controls. Catalytic studies with zeolite Beta indicate that crystals grown in space exhibit a lower number of Lewis acid sites located in micropores. This suggests fewer structural defects for crystals grown in microgravity. Transmission electron micrographs (TEM) of zeolite Beta crystals also show that crystals grown in microgravity were free of line defects while terrestrial/controls had substantial defects.

Sacco, Albert, Jr.; Bac, Nurcan; Warzywoda, Juliusz; Guray, Ipek; Marceau, Michelle; Sacco, Teran L.; Whalen, Leah M.

1997-01-01

323

Adsorption of Pb and Cd by amine-modified zeolite.  

PubMed

Natural zeolites, known for their excellent sorption properties towards metal cations, are widely used for the purification of wastewaters. The selectivity of clinoptilolite, a common zeolite mineral, for Pb is known to be particularly high, whereas its selectivity for Cd is often lower. Extraordinarily high sorption capacities for soft metal cations were observed in the case of thiol-functionalized silica gels and clays. In order to enhance the zeolites' sorption capacity for Cd, we treated natural heteroionic and Na-clinoptilolite in aqueous suspensions with cysteamine and propylamine solutions and investigated the sorption of Cd and Pb to amine-modified zeolite by a series of batch experiments. Stability constants for amine sorption on all zeolite samples at room temperature and 50 degrees C were obtained. Partial dimerization of cysteamine explains the enhanced sorption of this compound. In contrast, amine treatment did not enhance the adsorption capacity or selectivity of the clinoptilolite towards Cd and Pb. Instead, the amounts of adsorbed heavy metals decreased stoichometrically with increasing sorption of cysteamine and propylamine. This reduction can be explained by the blockage of channels by amine molecules and revealed that the modification of zeolites with mercaptoamines does not enhance the sorption capacity of zeolite for Cd and Pb. PMID:15996705

Wingenfelder, Ulla; Nowack, Bernd; Furrer, Gerhard; Schulin, Rainer

2005-09-01

324

Copper cation removal in an electrokinetic cell containing zeolite.  

PubMed

Zeolites are used in environmental remediation of soil or water to immobilize or remove toxic materials by cation exchange. An experiment was conducted to test the use a low electric field to direct the toxic cations towards the zeolite. An electrokinetic cell was constructed using carbon electrodes. Synthetic Linde Type A (LTA) zeolite was placed in the cell. Copper(II) chloride dissolved in water was used as a contaminant. The Cu(2+) concentration was measured for ten hours with and without an applied electric field. The removal of the Cu(2+) ions was accelerated by the applied field in the first two hours. For longer time, the electric field did not improve the removal rate of the Cu(2+) ions. The presence of zeolite and applied electric field complicates the chemistry near the cathode and causes precipitation of Cu(2+) ions as copper oxide on the surface of the zeolite. With increased electric field the zeolite farther away from the cathode had little cation exchange due to the higher drift velocity of the Cu(2+) ions. The results also show that, in the LTA Zeolite A pellets, the cation exchange of Cu is limited to a shell of several tens of micrometers. PMID:21109348

Elsayed-Ali, Omar H; Abdel-Fattah, Tarek; Elsayed-Ali, Hani E

2011-01-30

325

Liquid Crystalline Organic Conductors: Studies in Crystalline and Mesomorphic Phase  

Microsoft Academic Search

The present results concern a liquid crystalline organic conductor: DIPSAr4TCNQ. The ac conductivity was measured for the first time in the mesophase and indicates the actual possibility of obtaining organic conductors with mesomorphic behavior.

V. Gionis; H. Strzelecka; M. Veber; R. Kormann; L. Zuppiroli

1986-01-01

326

Internal surface modification of zeolite MFI particles and membranes for gas separation  

NASA Astrophysics Data System (ADS)

Zeolites are a well-known class of crystalline oxide materials with tunable compositions and nanoporous structures, and have been used extensively in catalysis, adsorption, and ion exchange. The zeolite MFI is one of the well-studied zeolites because it has a pore size and structure suitable for separation or chemical conversion of many industrially important molecules. I synthesized MFI membranes with [h0h] out-of-plane orientation on ?-alumina supports. The membranes were modified by the same procedures as used for MFI particles and with 1-butanol, 3-amino-1-propanol, 2-[(2-aminoethyl)amino]ethanol, and benzenemethanol. The existence of functional groups in the pores of the zeolite was confirmed by PA-FTIR measurements. Permeation measurements of H2, N2, CO2, CH 4, and SF6, were performed at room temperature before and after modification. Permeation of n-butane, and i-butane were measured before and after modification with 1-butanol. For all of the studied gases, gas permeances decreased by 1-2 orders of magnitude compared to bare MFI membranes for modified membranes. This is a strong indication that the organic species in the MFI framework are interacting with or blocking the gas molecule transport through the MFI pores. The CO2/CH 4 permeation selectivity was close to the Knudsen selectivity (0.6) for the membranes before modification. CO2/CH4 selectivity increased for MFI/benzenemethanol modified membrane (1.0), whereas it decreased for the MFI/2-[(2-aminoethyl)amino]ethanol modified membrane (0.5). MFI/benzenemethanol crystals were shown to have a highest sorption capacity for CH4, whereas, MFI/2-[(2-aminoethyl)amino]ethanol crystals were shown to have a highest sorption capacity for CO2 over all other studied molecules Higher sorption of CH4 in MFI/benzenemethanol and higher sorption of CO2 in MFI/2-[(2-aminoethyl)amino]ethanol and their strong binding to the modified membrane are likely the reasons for observing higher and lower CO2/CH4 permeation selectivity respectively, compared to bare MFI membrane. A further detailed fundamental study of the CO2 adsorption mechanism in modified zeolites is necessary to gain a better understating of the adsorption and permeation behavior of such materials. For the organic molecules with only one functional group (1-butanol, benzenemethanol, and 1-propaneamine), physical adsorption was found - as intuitively expected - to be the only observed mode of attachment of CO2 to the modified zeolite material. Even in the case of MFI modified with 1,3-diaminopropane, only physical adsorption is seen. This is explained by the isolated nature of the amine groups in the material, due to which only a single amine group can interact with a CO2 molecule. On the other hand, chemisorbed CO2 species are clearly observed on bare MFI, and on MFI modified with 3-amino-1-propanol or 2-[(2-aminoethyl)amino]ethanol. Specifically, these are carbonate-like species that arise from the chemisorption of CO2 to the silanol group in bare MFI and the alcohol groups of the modifying molecule. The possibility of significant contributions from external surface silanol groups in adsorbing CO2 chemisorbed species was ruled out by a comparative examination of the FTIR spectra of 10 ?m and 900 nm MFI particles modified with 2-[(2-aminoethyl)amino]ethanol. (Abstract shortened by UMI.).

Kassaee, Mohamad H.

327

Method of preparing sodalite from chloride salt occluded zeolite A  

SciTech Connect

A method is described for immobilizing waste chloride salts containing radionuclides and hazardous nuclear material for permanent disposal starting with a substantially dry zeolite and sufficient glass to form leach resistance sodalite with occluded radionuclides and hazardous nuclear material. The zeolite and glass are heated to a temperature up to about 1,000 K to convert the zeolite to sodalite and thereafter maintained at a pressure and temperature sufficient to form a sodalite product near theoretical density. Pressure is used on the formed sodalite to produce the required density.

Lewis, M.A.; Pereira, C.

1995-12-31

328

Method of preparing sodalite from chloride salt occluded zeolite  

DOEpatents

A method is described for immobilizing waste chloride salts containing radionuclides and hazardous nuclear material for permanent disposal starting with a substantially dry zeolite and sufficient glass to form leach resistant sodalite with occluded radionuclides and hazardous nuclear material. The zeolite and glass are heated to a temperature up to about 1000 K to convert the zeolite to sodalite and thereafter maintained at a pressure and temperature sufficient to form a sodalite product near theoretical density. Pressure is used on the formed sodalite to produce the required density.

Lewis, M.A.; Pereira, C.

1997-03-18

329

TEM studies of zeolites and ordered mesoporous materials.  

PubMed

In the present manuscript we have reviewed recent results on transmission electron microscopy of beam sensitive materials such as zeolites and ordered mesoporous materials. The results of the investigation of the fine structure of different zeolite types as MFI, ITQ-7 and the presence of mixture of phases are shown. In addition, the incorporation of metals within the zeolitic framework and their different applications as precursors for metal nanowire growth are also described. The combination of HRTEM together with electron crystallography for solving new ordered mesoporous silica and associated analytical techniques shows the strength of electron microscopy for a full characterization of such materials. PMID:21227705

Diaz, Isabel; Mayoral, Alvaro

2011-07-01

330

Zeolite crystal growth in space - What has been learned  

NASA Technical Reports Server (NTRS)

Three zeolite crystal growth experiments developed at WPI have been performed in space in last twelve months. One experiment, GAS-1, illustrated that to grow large, crystallographically uniform crystals in space, the precursor solutions should be mixed in microgravity. Another experiment evaluated the optimum mixing protocol for solutions that chemically interact ('gel') on contact. These results were utilized in setting the protocol for mixing nineteen zeolite solutions that were then processed and yielded zeolites A, X and mordenite. All solutions in which the nucleation event was influenced produced larger, more 'uniform' crystals than did identical solutions processed on earth.

Sacco, A., Jr.; Thompson, R. W.; Dixon, A. G.

1993-01-01

331

Preparation of bioinorganic fertilizing media by adsorption of humates on glassy aluminosilicates.  

PubMed

Surface-modified expanded perlite was synthesized using humic substances from the Megalopolis peaty lignite. Adsorption is efficient and increases at higher temperatures and lower pHs. The preparation can be carried out under mild conditions leading to an eco-friendly, bioinorganic material useful as soil conditioner and biofertilizer. Six adsorption models were applied; the Klotz, Freundlich and Redlich-Peterson isotherms fit more successfully to the experimental data. The obeying of the theoretical models was correlated with the heterogeneity and non-uniform distribution of the adsorption sites, host-guest attraction forces as well as the formation of self-assembled aggregates and self-organized multilayers of humic substances onto the aluminosilicate adsorbent, consistent with changes in micromorphology. Thermodynamic quantities revealing distinct physicochemical characteristics of the adsorption phenomena, i.e., enthalpy, entropy and free energy change, were calculated. Desorption experiments and cultivation of microorganisms demonstrated that perlite may act successfully as host material for microbial populations upgrading the humic-loaded perlite for soil applications. PMID:20692818

Chassapis, Konstantinos; Roulia, Maria; Vrettou, Evangelia; Parassiris, Anastassios

2010-11-01

332

Chemical and mechanical consequences of environmental barrier coating exposure to calcium-magnesium-aluminosilicate.  

SciTech Connect

The success of Si-based ceramics as high-temperature structural materials for gas turbine applications relies on the use of environmental barrier coatings (EBCs) with low silica activity, such as Ba{sub 1-x}Sr{sub x}Al{sub 2}Si{sub 2}O{sub 8} (BSAS), which protect the underlying components from oxidation and corrosion in combustion environments containing water vapor. One of the current challenges concerning EBC lifetime is the effect of sandy deposits of calcium-magnesium-aluminosilicate (CMAS) glass that melt during engine operation and react with the EBC, changing both its composition and stress state. In this work, we study the effect of CMAS exposure at 1300 C on the residual stress state and composition in BSAS-mullite-Si-SiC multilayers. Residual stresses were measured in BSAS multilayers exposed to CMAS for different times using high-energy X-ray diffraction. Their microstructure was studied using a combination of scanning electron microscopy and transmission electron microscopy techniques. Our results show that CMAS dissolves the BSAS topcoat preferentially through the grain boundaries, dislodging the grains and changing the residual stress state in the topcoat to a nonuniform and increasingly compressive stress state with increasing exposure time. The presence of CMAS accelerates the hexacelsian-to-celsian phase transformation kinetics in BSAS, which reacts with the glass by a solution-reprecipitation mechanism. Precipitates have crystallographic structures consistent with Ca-doped celsian and Ba-doped anorthite.

Harder, B.; Ramirez-Rico, J.; Almer, J. D.; Kang, L.; Faber, K. (X-Ray Science Division); (NASA Glenn Research Center); (Univ. of Seville); (Rolls-Royce Corp.); (Northwestern Univ.)

2011-06-01

333

Characteristics of a thermally activated alumino-silicate pozzolanic material and its use in concrete  

SciTech Connect

Canada Centre for Mineral and Energy Technology (CANMET) has an ongoing program dealing with the development of concrete having long-term durability. One of the means of achieving this objective is to incorporate supplementary cementing materials such as silica fume, fly ash, slag, and rick husk ash in concrete. The incorporation of these supplementary cementing materials in concrete leads to reduction in its porosity; this, in turn, leads to reduced permeability and increased durability of concrete. This paper presents the results of the physical and chemical properties of a thermally activated alumino-silicate material (MK), and deals with the properties of fresh and hardened concrete incorporating this material. The properties of fresh concrete investigated included workability, bleeding, setting time, and autogenous temperature rise. The properties of the hardened concrete investigated included compressive, splitting-tensile and flexural strengths, Young`s modulus of elasticity, drying shrinkage, resistance to chloride-ion penetration, freezing and thawing, and salt-scaling resistance. The properties of the MK concrete were also compared with those of the control portland cement concrete and the silica fume concrete.

Zhang, M.H.; Malhotra, V.M. [CANMET, Ottawa, Ontario (Canada)] [CANMET, Ottawa, Ontario (Canada)

1995-12-01

334

Fabrication of large diameter alumino-silicate K{sup +} sources  

SciTech Connect

Alumino-silicate K{sup +} sources have been used in HIF experiments for many years. For example the Neutralized Transport Expt. (NTX) and the High Current Transport Expt. (HCX) are now using this type of ion source with diameters of 2.54 cm and 10 cm respectively. These sources have demonstrated ion currents of 80 mA and 700 mA, for typical HIF pulse lengths of 5-10 {micro}s. The corresponding current density is {approx} 10-15 mA/cm{sup 2}, but much higher current density has been observed using smaller size sources. Recently we have improved our fabrication techniques and, therefore, are able to reliably produce large diameter ion sources with high quality emitter surface without defects. This note provides a detailed description of the procedures employed in the fabrication process. The variables in the processing steps affecting surface quality, such as substrate porosity, powder size distribution, coating technique on large area concave surfaces, drying, and heat firing temperature have been investigated.

Baca, D.; Chacon-Golcher, E.; Kwan, J.W.; Wu, J.K.

2003-02-20

335

Alkaline solution/binder ratio as a determining factor in the alkaline activation of aluminosilicates  

SciTech Connect

This study investigates the effect of the alkaline solution/binder (S/B) ratio on the composition and nanostructure of the reaction products generated in the alkaline activation of aluminosilicates. The experiments used two mixtures of fly ash and dehydroxylated white clay and for each of these, varying proportions of the solution components. The alkali activator was an 8 M NaOH solution (with and without sodium silicate) used at three S/B ratios: 0.50, 0.75 and 1.25. The {sup 29}Si, {sup 27}Al MAS NMR and XRD characterisation of the reaction products reveal that for ratios nearest the value delivering suitable paste workability, the reaction-product composition and structure depend primarily on the nature and composition of the starting materials and the alkaline activator used. However, when an excess alkaline activator is present in the system, the reaction products tend to exhibit SiO{sub 2}/Al{sub 2}O{sub 3} ratios of approximately 1, irrespective of the composition of the starting binder or the alkaline activator.

Ruiz-Santaquiteria, C., E-mail: ruiz.cs@ietcc.csic.es [Eduardo Torroja Institute (CSIC), c/Serrano Galvache, n Degree-Sign 4, 28033 Madrid (Spain); Skibsted, J. [Instrument Centre for Solid-State NMR Spectroscopy, Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, Aarhus University, DK-8000 Aarhus C (Denmark)] [Instrument Centre for Solid-State NMR Spectroscopy, Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, Aarhus University, DK-8000 Aarhus C (Denmark); Fernandez-Jimenez, A.; Palomo, A. [Eduardo Torroja Institute (CSIC), c/Serrano Galvache, n Degree-Sign 4, 28033 Madrid (Spain)] [Eduardo Torroja Institute (CSIC), c/Serrano Galvache, n Degree-Sign 4, 28033 Madrid (Spain)

2012-09-15

336

Single-Walled Aluminosilicate Nanotube/Poly(vinyl alcohol) Nanocomposite Membranes  

SciTech Connect

The fabrication, detailed characterization, and molecular transport properties of nanocomposite membranes containing high fractions (up to 40 vol %) of individually-dispersed aluminosilicate single-walled nanotubes (SWNTs) in poly(vinyl alcohol) (PVA), are reported. The microstructure, SWNT dispersion, SWNT dimensions, and intertubular distances within the composite membranes are characterized by scanning and transmission electron microscopy (SEM and TEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), XRD rocking curve analysis, small-angle X-ray scattering (SAXS), and solid-state NMR. PVA/SWNT nanocomposite membranes prepared from SWNT gels allow uniform dispersion of individual SWNTs in the PVA matrix with a random distribution of orientations. SAXS analysis reveals the length ({approx}500 nm) and outer diameter ({approx}2.2 nm) of the dispersed SWNTs. Electron microscopy indicates good adhesion between the SWNTs and the PVA matrix without the occurrence of defects such as voids and pinholes. The transport properties of the PVA/SWNT membranes are investigated experimentally by ethanol/water mixture pervaporation measurements, computationally by grand canonical Monte Carlo and molecular dynamics, and by a macroscopic transport model for anisotropic permeation through nanotube-polymer composite membranes. The nanocomposite membranes substantially enhance the water throughput with increasing SWNT volume fraction, which leads to a moderate reduction of the water/ethanol selectivity. The model is parameterized purely from molecular simulation data with no fitted parameters, and shows reasonably good agreement with the experimental water permeability data.

Kang, Dun-Yen; Tong, Ho Ming; Zang, Ji; Choudhury, Rudra Prosad; Sholl, David S.; Beckham, Haskell W.; Jones, Christopher W.; Nair, Sankar (GIT)

2012-05-29

337

Aluminosilicate melts and glasses at 1 to 3 GPa: temperature and pressure effects on recovered structural and density changes  

NASA Astrophysics Data System (ADS)

The effects of pressure on aluminosilicate melt and glass structure have been studied by both in-situ methods and by quenching and recovering glasses from high pressure and temperature. Significant increases in the coordination number of Al are now well known from the pressure range of 6-10 GPa. New results show that even at shallower mantle pressures of 1-3 GPa, typical aluminosilicate melts have significant concentrations of aluminum cations with coordination numbers greater than 4, with up to 10's of percents of AlO5 and AlO6. Here, we compare the densities and Al coordinations of glass samples recovered from piston-cylinder experiments carried out at 1 to 3 GPa and different temperatures. Samples of two different compositions (Ca3Al2Si6O18 and Na2Si3O7 with 0.5% Al2O3) were compressed and held at temperatures ranging from near to their ambient glass transitions (Tg) up to temperatures above the liquidus. Our 2 GPa sodium aluminosilicate and calcium aluminosilicate glasses quenched from near to Tg show about 5 and 6 percent recovered densification, respectively. In both compositions, samples that were quenched from above the melting point showed substantially lower recovered density and lower Al coordination number compared to the samples that were held near to Tg. For example, sodium aluminosilicate glass quenched from 510C (near to Tg) had 70% more AlO5 than samples from 1200C. Based on the measurement of actual cooling rates, fictive temperature differences for the glasses from these two extreme temperatures are not large enough to account for this apparent loss in density and Al-coordination during quench. The most likely cause for these differences is therefore probably the pressure drop during cooling from temperatures above liquidus, as the pressure medium does not respond quickly enough to the thermal contraction of the liquid and furnace parts to remain isobaric. Results from previous high T and P quenching studies thus give only minimum estimates of pressure effects on melt structure. Samples were made in a piston-cylinder apparatus in 5mm platinum capsules, with 1 inch diameter calcium fluorite assemblies and graphite heaters. Structure was examined by Al-27 and Na-23 MAS NMR at 14.4 and 18.8 Tesla fields, and glass densities determined by high-precision sink-float methods.

Bista, S.; Stebbins, J. F.; Hankins, B.; Sisson, T. W.

2013-12-01

338

The evolution of strength and crystalline phases for alkali-activated ground blast furnace slag and fly ash-based geopolymers  

SciTech Connect

The increase in strength and evolution of crystalline phases in inorganic polymer cement, made by the alkali activation of slag, Class C and Class F fly ashes, was followed using compressive strength test and synchrotron X-ray diffraction. In order to increase the crystallinity of the product the reactions were carried out at 80 deg. C. We found that hydrotalcite formed in both the alkali-activated slag cements and the fly ash-based geopolymers. Hydroxycancrinite, one member of the ABC-6 family of zeolites, was found only in the fly ash geopolymers. Assuming that the predominantly amorphous geopolymer formed under ambient conditions relates to the crystalline phases found when the mixture is cured at high temperature, we propose that the structure of this zeolitic precursor formed in Na-based high alkaline environment can be regarded as a disordered form of the basic building unit of the ABC-6 group of zeolites which includes poly-types such as hydroxycancrinite, hydroxysodalite and chabazite-Na.

Oh, Jae Eun [Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720 (United States); Monteiro, Paulo J.M., E-mail: monteiro@berkeley.ed [Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720 (United States); Jun, Ssang Sun [Global Leading Offshore Plant Education Center, Korea Maritime University, Busan, 606-791 (Korea, Republic of); Choi, Sejin [Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720 (United States); Clark, Simon M. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 20015 (United States); Department of Earth and Planetary Sciences, University of California, Berkeley, CA 94720 (United States)

2010-02-15

339

Circumstellar Crystalline Silicates: Evolved Stars  

NASA Astrophysics Data System (ADS)

One of the most exciting developments in astronomy in the last 15 years was the discovery of crystalline silicate stardust by the Short Wavelength Spectrometer (SWS) on board of ISO; discovery of the crystalline grains was indeed one of the biggest surprises of the ISO mission. Initially discovered around AGB stars (evolved stars in the range of 0.8 > M/M¤>8) at far-infrared (IR) wavelengths, crystalline silicates have since been seen in many astrophysical environments including young stellar objects (T Tauri and Herbig Ae/Be), comets and Ultra Luminous Infrared Galaxies. Low and intermediate mass stars (LIMS) comprise 95% of the contributors to the ISM, so study of the formation of crystalline silicates is critical to our understanding of the ISM, which is thought to be primarily amorphous (one would expect an almost exact match between the composition of AGB dust shells and the dust in the ISM). Whether the crystalline dust is merely undetectable or amorphized remains a mystery. The FORCAST instrument on SOFIA as well as the PACS instrument on Herschel will provide exciting observing opportunities for the further study of crystalline silicates.

Tartar, Josh; Speck, A. K.

2008-05-01

340

Interaction between zeolites and cluster compounds. Part 2.?Thermal decomposition of iron pentacarbonyl on zeolites  

Microsoft Academic Search

Thermal decomposition in a thermobalance of Fe(CO), adsorbed on alkali-metal, hydrogen-Y, dealuminated Y, L and omega zeolites proceeds stepwise via slow decarbonylation at low and high temperatures, separated by a fast endothermic reaction. Average CO\\/Fe ratios have been determined after each step. From i.r. results the former intermediates are assigned to species bearing bridging CO, whereas reaction products with CO\\/Fe

Thomas Bein; Peter A. Jacobs

1984-01-01

341

Reactions of 3-methylpentane and 2,3-dimethylbutane on aluminosilicate catalysts  

SciTech Connect

Catalytic reactions of 3-methylpentane and 2,3-dimethylbutane on HY, amorphous silica-alumina, and HZSM-5 have been studied at 500{degree}C. Both kinetic phenomena and product selectivities have been reported. Cracking reactions an HZSM-5 can be attributed to initiation through protonation occurring at Bronsted sites. Bimolecular processes leading to chain reaction via hydride transfer are restricted within the narrow pore pentasil zeolite. On HY and amorphous silica-alumina, initiation of cracking also occurs at Bronsted sited. No direct evidence was found for participation of Lewis acid sites on the catalyst framework itself. Following initiation, reactions on these catalysts are accelerated through a chain process occurring at Lewis sites generated by adsorption of product olefins at Bronsted sites. The resulting change in the dominant cracking mechanism is reflected in the product selectivity, illustrated here by a falling off in formation of molecular hydrogen as conversion increases.

Abbot, J. (Univ. of Tasmania, Hobart (Australia))

1990-12-01

342

Adsorption of trichlorophenol on zeolite and adsorbent regeneration with ozone.  

PubMed

A FAU-type zeolite was studied as an adsorbent to remove 2,4,6-trichlorophenol (TCP), a frequently detected recalcitrant pollutant in water bodies. Both adsorption isotherm and kinetics were studied with TCP concentrations from 10 to 100mg/L. It was observed that TCP was effectively adsorbed onto the zeolite with a high adsorption capacity and a high kinetic rate. Freundlich model and pseudo-second-order kinetics were successfully applied to describe the experimental data. The influence of solution pH was also studied. Furthermore, ozone was applied to regenerate the loaded zeolite. It was found that an effective adsorption of TCP was kept for at least 8 cycles of adsorption and regeneration. The ozonation also increased the BET specific surface of zeolite by over 60% and consequently enhanced the adsorption capacity. PMID:24632370

Zhang, Yongjun; Mancke, Raoul Georg; Sabelfeld, Marina; Geien, Sven-Uwe

2014-04-30

343

Characterization of a zeolite membrane for catalytic membrane reactor application  

SciTech Connect

This paper describes the morphological and transport properties of a composite zeolite (silicalite) - alumina membrane. Some advantages obtained in combining the membrane with a conventional fixed-bed catalyst are also reported.

Giroir-Fendler, A.; Peureux, J.; Mozzanega, H.; Dalmon, J.A. [Institut de Recherches sur la Catalyse, Villeurbanne (France)

1996-12-31

344

Comparative study of the removal of coke from protonic zeolites  

SciTech Connect

The transformation of methanol was carried out at 400{degrees}C on four protonic zeolites: USHY (framework Si/Al ratio equal to 5), HZSM5 (Si/Al = 45), two mordenites HMOR (Si/Al = 7.5) and HMORDA (Si/Al = 80) prepared by dealumination of HMOR through hydrothermal and acid treatments. The composition of coke determined through the method developed in the authors` laboratory depended slightly on the zeolite. The amount of coke removed for the zeolites through oxidative treatment was determined as function of the temperature and for various coke contents. The rate of coke removal depended slightly on the coke content and on the coke composition by very much on the zeolite. In particular the coke of HMORDA and of HZSM5 was eliminated at high temperature only.

Gnep, N.S.; Roger, P.; Magnoux, P.; Guisnet, M. [Laboratoire de Catalyse en Chimie Organique, Poitiers (France)

1993-12-31

345

Investigation of Zeolite Nucleation and Growth Using NMR Spectroscopy  

E-print Network

Zeolite nucleation and growth is a complex problem that has been widely investigated but still not completely understood. However, a full understanding of this process is required in order to develop predictive models for the rational design...

Rivas Cardona, Alejandra

2012-02-14

346

Anionic Emulsion-Mediated Synthesis of Zeolite Beta  

NASA Astrophysics Data System (ADS)

Well-crystallized zeolite beta is first synthesized in the anionic emulsion systems of cyclohexane/sodium dodecylbenzenesulfonate(SDBS)/pentanol/zeolite synthesis mixture. Beta materials are then characterized by XRD, SEM, and N2-adsorption techniques. Compared to beta samples grown using the same synthesis mixture in the absence of the anionic emulsion, the as-synthesized beta presents uniform and well-defined larger crystals. Interestingly, N2-adsorption results show that such beta sample possesses both ordered mesopores at 3.9 nm and macropores centered at 60.5 nm. These pores combined with the intricate micropores of the Beta crystal comprise the hierarchical porosity. The hierarchical pore-structured zeolite beta may have potential catalysis application in reactions involving large molecules. Additionally, control experiments are also performed to ascertain the effects of the individual emulsion components. Further synthesis study finds the transformation of zeolite beta to ZSM-5 through increasing oil contents, crystallization temperature and time.

Jin, Chao; Zhang, Ying; Gao, Wei; Cui, Lishan

347

Controlled release of preservatives using dealuminated zeolite Y.  

PubMed

This study demonstrates that dealuminated zeolite Y can act as a depot after adsorption of phenol derived preservatives. Upon suspension of zeolite loaded with the preservative m-cresol, equilibrium was quickly reached between free and adsorbed m-cresol. The equilibrium concentration of m-cresol was below 1 mM; however, it was enough to kill bacteria such as Escherichia coli and Staphylococcus aureus under metabolically active conditions. Killing of bacteria was not obtained under non-proliferating conditions and m-cresol was only released from the zeolite upon bacterial activity. Together, these results demonstrate an interesting potential use of dealuminated zeolite Y containing adsorbed preservatives for preventing microbial growth in numerous applications in industry and clinical setting. PMID:17599464

Eriksson, Hkan

2008-04-24

348

Dealumination of HZSM-5 zeolites. I. Calcination and hydrothermal treatment  

SciTech Connect

The effect of calcination and hydrothermal treatments on the structure and properties of HZSM-5 zeolites with a range of aluminum contents has been investigated. Characterization of the treated zeolites was undertaken with solid-waste NMR ({sup 27}Al and {sup 29}Si), infrared, nitrogen and water adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, chemical analysis, and {sup 129}Xe NMR spectroscopy. Both calcination and hydrothermal treatment were found to cause dealumination of the zeolite lattice and formation of extralattice aluminum species of low symmetry which remain within the pores of the zeolite. HZSM-5 with low aluminum content was found to be more resistant to dealumination by either method and the degree of dealumination was greater when steam was present in the treatment. {sup 129}Xe NMR was found to be a useful probe for the presence of extralattice aluminum in the pores of lattice dealuminated HZSM-5. 35 refs., 9 figs., 3 tabs.

Campbell, S.M. [Louisana State Univ., Shreveport, LA (United States)] [Louisana State Univ., Shreveport, LA (United States); [Univ. of Auckland (New Zealand); Bibby, D.M.; Meinhold, R.H. [Industrial Research Ltd., Petone (New Zealand)] [and others] [Industrial Research Ltd., Petone (New Zealand); and others

1996-06-01

349

Xenon NMR studies of dynamics and exchange in zeolites  

SciTech Connect

We have found, despite earlier reports to the contrary, that for many microporous solids with one-dimensional channels (ZSM-12, ALPO-5, VPI-5, SSZ-24) the chemical shift has an anisotropic component. For ALPO-11, a detailed model has been developed which accounts for the loading-dependent chemical shift in terms of intraparticle exchange of statistical distributions of xenon atoms with 0, 1 or 2 nearest neighbors. A similar model can be applied to ZSM-12 up to moderate loadings. At higher loading levels 2D exchange methods show that interparticle exchange occurs as well. The same approach was used to study interparticle exchange in X and Y zeolite mixtures, exchange amongst zeolite clusters of up to 8 xenon atoms in the supercages of AgA zeolite, and main channel - side pocket exchange in mordenite. The parameters derived are directly relevant to the understanding of sorption and diffusion processes in zeolites.

Moudrakovski, I.L.; Ratcliffe, C.I.; Ripmeester, J.A. [Steacie Institute for Molecular Sciences, Ottawa, Ontario (Canada)

1996-10-01

350

Hydration and dehydration of Zeolitic Tuff from Yucca Mountain, Nevada  

NASA Astrophysics Data System (ADS)

Naturally occurring zeolites expand and contract when hydrated or dehydrated. In tuffaceous rock composed largely of such zeolites, the entire rock may swell or contract significantly as the rock becomes saturated or dries out. If such rock is constrained, significant stresses may develop as a result of hydration or dehydration. We present experimental results that substantiate this. In a zeolitized, non-welded tuff from Yucca Mountain, NV, rock permeability governs the swelling rate since the major constituent, clinoptilolite, hydrates as fast as it can be exposed to water. At Yucca Mountain, where a nuclear waste repository is proposed, strata of welded, devitrified tuff overlie non-welded, zeolitic tuff. Should the hydration state of the units change significantly over the repository lifetime, additional stresses on the same order of magnitude as now exist may develop.

Kranz, R. L.; Bish, D. L.; Blacic, J. D.

1989-10-01

351

The efficiency of Jordanian natural zeolite for heavy metals removal  

NASA Astrophysics Data System (ADS)

The capability of Jordanian natural zeolite to remove nickel from aqueous solutions was experimentally investigated using a packed bed column. The zeolite samples were obtained from Jabal AL Aritayn in the northeast of Jordan. The effects of the initial concentration of nickel ( C 0), the packed bed length ( L) and the zeolite grain size ( D p) on the adsorption process were considered. The finding indicated that these parameters named had a significant effect on the removal of nickel by the Jordanian zeolite. The characteristic breakthrough curves of the adsorption process were measured. The Klinkenberg model was adopted to explain the kinetic behavior of the adsorption phenomena, and we attempted to fit the packed bed experimental data to the breakthrough curve. The effective diffusivity was estimated and used to predict breakthrough curves under other adsorption conditions.

Taamneh, Yazan; Al Dwairi, Reyad

2013-03-01

352

Review and Bibliography on Rock Solubility and Zeolite Minerals.  

National Technical Information Service (NTIS)

A bibliography was prepared and literature reviewed on the solubility of rock and rock-forming minerals, with emphasis on laboratory methods for solubility studies and the solubility of zeolites and calcium carbonate. As solubility is dependent on many va...

G. W. DePuy

1968-01-01

353

Structure of D[sub 2] in zeolite  

Microsoft Academic Search

We have measured the structure of D[sub 2] adsorbed in zeolite 13[ital X] at temperatures in the range 5.5 to 80 K at a variety of fillings. We find that the D[sub 2] molecules adsorb into well-defined adsorbtion sites in the zeolite structure. Two distinct adsorbtion sites, with binding energies on the order of 40 and 80 K, have been

M. P. Fang; P. E. Sokol; Y. Wang

1994-01-01

354

Mathematical modeling of fixed-bed oxidative regeneration of zeolite  

Microsoft Academic Search

1.The formation of a steady-state combustion front has been demonstrated in the fixed-bed oxidative regeneration of zeolite.2.Process conditions have been investigated in relation to their effects on the basic characteristics of the process, i.e., the average coke combustion rate and the maximum temperature rise in the zeolite. This work has demonstrated the important role of these characteristics in selecting optimal

V. I. Nazarok; O. I. Gaponenko; A. S. Shmelev; K. I. Patrilyak; P. N. Galich

1975-01-01

355

Performance of Silver Zeolite in a Radioiodine Monitor  

Microsoft Academic Search

Measurement were made of the interaction of 8Kr, 133Xe, CH3I (131I) and I2 (131I) with various silver zeolites and activated charcoals under varying relative humidities and temperatures. Results show silver zeolite has significantly less interaction with noble gases and high adsorption efficiencies for CH3I making it superior to charcoal for airborne radioiodine monitoring. The penetration of airborne iodine activity into

G. Y. SooHoo; Chien-chang Lin; R. M. Norris; C. D. Wilkinson

1975-01-01

356

Molecular sieve zeolite technology - the first twenty-five years  

Microsoft Academic Search

ABSTRACT In twentyfive years molecular sieve zeolites have substantially impacted adsorption and catalytic process technology throughout the chemical,process,industries;,provided timely solutions to energy,and environmental,problems;,and grown,to over,a hundred,million,dollar industry,worldwide.,The evolution,in zeolite materials with improved or novel properties has strongly influenced the expansion of their,applications, and provided new flexibility in the design of products and processes.

Edith M. Flanigen

1980-01-01

357

Zeolites in the Cascade Range of northern Oregon  

Microsoft Academic Search

Twenty-three zeolite minerals were identified during secondary mineralogy studies of late Tertiary volcanic rock outcrop samples and\\/or late Tertiary to Quaternary geothermal drill-hole specimens in three areas of the Oregon Cascade Range (near Mount Hood, the Breiten bush-Austin Hot Springs area, and Newberry volcano). The Neogene to Holocene volcanic rocks contain euhedral to subhedral zeolite crystals in open spaces of

1997-01-01

358

Origin of strong acidity in lanthanum-exchanged zeolites  

E-print Network

of this research was to determine the factors which give rise to strong acidity in zeolites. There is a linear relation between catalytic activity and zeolite framework aluminum number in the range of' 0 to 32 aluminum atoms per unit cell, whereas at higher... amounts of framework aluminum the activity decreases. This relationship is in agreement with a theoretical model of framework aluminum distribution and acidity, in which protons associated with isolated aluminum atoms are assigned a higher acidity...

Carvajal Freese, Ralf R.

2012-06-07

359

Chromophore-bearing zeolite materials as precursors of colored ceramics  

Microsoft Academic Search

This work investigates the possibility to obtain colored ceramics by firing compacts of the synthetic zeolite A, pre-loaded with chromophore metal cations, and gives also a preliminary evaluation of their technical properties. Natural zeolite-bearing materials, i.e., clinoptilolite- and phillipsite-rich tuffs, which naturally contain chromofore agents, such as iron oxides and hydroxides, have also been considered as ceramic precursors. The results

B. Liguori; A. Cassese; C. Colella

2005-01-01

360

Metal Oxide/Zeolite Combination Absorbs H2S  

NASA Technical Reports Server (NTRS)

Mixed copper and molybdenum oxides supported in pores of zeolite found to remove H2S from mixture of gases rich in hydrogen and steam, at temperatures from 256 to 538 degree C. Absorber of H2S needed to clean up gas streams from fuel processors that incorporate high-temperature steam reformers or hydrodesulfurizing units. Zeolites chosen as supporting materials because of their high porosity, rigidity, alumina content, and variety of both composition and form.

Voecks, Gerald E.; Sharma, Pramod K.

1989-01-01

361

Commander Bowersox Tends to Zeolite Crystal Samples Aboard Space Station  

NASA Technical Reports Server (NTRS)

Expedition Six Commander Ken Bowersox spins Zeolite Crystal Growth sample tubes to eliminate bubbles that could affect crystal formation in preparation of a 15 day experiment aboard the International Space Station (ISS). Zeolites are hard as rock, yet are able to absorb liquids and gases like a sponge. By using the ISS microgravity environment to grow better, larger crystals, NASA and its commercial partners hope to improve petroleum manufacturing and other processes.

2003-01-01

362

Photochemistry without protons. Radical cation chemistry in zeolites  

SciTech Connect

The interconversion of the C{sub 7}H{sub 8} molecular framework, especially norbornadiene (NBD) and quadricyclane (Q), has been considered for photochemical energy storage. Actually, very little was known about the details of these carbon-skeleton transformations, and only one radical cation species (NBD{sup +}{center_dot}) was characterized. The authors have undertaken a thorough study of these systems using zeolite matrices. They have shown that zeolites have exceptional properties, allowing unprecedented control of chemical reactivity. In the attached scheme, they outline some of the species they were able to characterize. The crucial aspect of the zeolite matrix is that one can tune the matrix-radical cation interaction by varying the matrix polarity. The ZSM-5 zeolites of identical structure with different Si/Al ratio are ideally suited for such study. Without discussing all the transformations, the authors point that several processes, such as the reverse Diels-Alder reaction are known to occur by involvement of highly excited states. Such reactions in zeolites means that sites in the zeolite matrix are able to stabilize high electronic states of ions, significantly lowering the potential energy barrier for such reactions. Thus, they are able to thermally drive otherwise photodriven reactions.

Trifunac, A.D.; Barnabas, M.V.

1994-06-01

363

Moderate-temperature zeolitic alteration in a cooling pyroclastic deposit  

USGS Publications Warehouse

The locally zeolitized Topopah Spring Member of the Paintbrush Tuff (13 Myr.), Yucca Mountain, Nevada, U.S.A., is part of a thick sequence of zeolitized pyroclastic units. Most of the zeolitized units are nonwelded tuffs that were altered during low-temperature diagenesis, but the distribution and textural setting of zeolite (heulandite-clinoptilolite) and smectite in the densely welded Topopah Spring tuff suggest that these hydrous minerals formed while the tuff was still cooling after pyroclastic emplacement and welding. The hydrous minerals are concentrated within a transition zone between devitrified tuff in the central part of the unit and underlying vitrophyre. Movement of liquid and convected heat along fractures from the devitrified tuff to the ritrophyre caused local devitrification and hydrous mineral crystallization. Oxygen isotope geothermometry of cogenetic quartz confirms the nondiagenetic moderate temperature origin of the hydrous minerals at temperatures of ??? 40-100??C, assuming a meteoric water source. The Topopah Spring tuff is under consideration for emplacement of a high-level nuclear waste repository. The natural rock alteration of the cooling pyroclastic deposit may be a good natural analog for repository-induced hydrothermal alteration. As a result of repository thermal loading, temperatures in the Topopah Spring vitrophyre may rise sufficiently to duplicate the inferred temperatures of natural zeolitic alteration. Heated water moving downward from the repository into the vitrophyre may contribute to new zeolitic alteration. ?? 1989.

Levy, S. S.; O'Neil, J. R.

1989-01-01

364

Solvent Evaporation Assisted Preparation of Oriented Nanocrystalline Mesoporous MFI Zeolites  

SciTech Connect

A solvent evaporation route to produce hierarchically porous zeolites with an oriented MFI nanocrystalline structure has been developed, and the method is scalable and productive. In this method, hexadecyltrimethoxysilane is added to an ethanol solution containing zeolitic precursors. A hard gel is formed during the evaporation process. Subsequent hydrothermal treatments produce the hierarchically porous zeolite. High resolution transmission electron microscopy (HRTEM) studies suggest that misoriented zeolite nuclei are produced in the very early stages of the hydrothermal treatment, but further reactions lead to single crystal-like aggregates composed of intergrowth nanocrystals with a mean interparticle pore diameter of 12 nm. All Al atoms exist in tetrahedral sites, as confirmed by 27Al magic angle spinning nuclear magnetic resonance (MAS NMR). Variable temperature hyperpolarized (HP) 129Xe NMR spectroscopy suggest a fast molecular diffusion process from the interconnection between micro- and mesopores. Catalytic conversion of acetone to the isobutene reactions show comparable (with respect to conventional zeolites) selectivity to isobutene. However, hierarchically porous zeolites display enhanced activity and durability because of the more accessible acidic sites in the hierarchically porous structures.

Zhu, Kake; Sun, Junming; Liu, Jun; Wang, Li Q.; Wan, Haiying; Hu, Jian Z.; Wang, Yong; Peden, Charles HF; Nie, Zimin

2011-07-01

365

Solution properties of ?-crystallins: hydration of fish and mammal ?-crystallins.  

PubMed

Lens ? crystallins are found at the highest protein concentration of any tissue, ranging from 300 mg/mL in some mammals to over 1000 mg/mL in fish. Such high concentrations are necessary for the refraction of light, but impose extreme requirements for protein stability and solubility. ?-crystallins, small stable monomeric proteins, are particularly associated with the lowest hydration regions of the lens. Here, we examine the solvation of selected ?-crystallins from mammals (human ?D and mouse ?S) and fish (zebrafish ?M2b and ?M7). The thermodynamic water binding coefficient B? could be probed by sucrose expulsion, and the hydrodynamic hydration shell of tightly bound water was probed by translational diffusion and structure-based hydrodynamic boundary element modeling. While the amount of tightly bound water of human ?D was consistent with that of average proteins, the water binding of mouse ?S was found to be relatively low. ?M2b and ?M7 crystallins were found to exhibit extremely low degrees hydration, consistent with their role in the fish lens. ?M crystallins have a very high methionine content, in some species up to 15%. Structure-based modeling of hydration in ?M7 crystallin suggests low hydration is associated with the large number of surface methionine residues, likely in adaptation to the extremely high concentration and low hydration environment in fish lenses. Overall, the degree of hydration appears to balance stability and tissue density requirements required to produce and maintain the optical properties of the lens in different vertebrate species. PMID:24282025

Zhao, Huaying; Chen, Yingwei; Rezabkova, Lenka; Wu, Zhengrong; Wistow, Graeme; Schuck, Peter

2014-01-01

366

Pyrolysis of scrap tyres with zeolite USY.  

PubMed

A zeolite catalyst of ultrastable Y-type (USY) was investigated in the research of two staged pyrolysis-catalysis of scrap tyres. Scrap tyres were pyrolysed in a fixed bed reactor and the evolved pyrolysis gases were passed through a secondary catalytic reactor. The main objective of this paper was to investigate the effect of zeolite USY on the yield of products and the composition of derived oil. The influences of several parameters such as pyrolysis temperature, catalytic temperature, catalyst/tyre ratio, heating rate, etc. on the yield of the derived oil, char and gas were investigated. It showed that the increase of catalytic temperature and catalyst/tyre ratio resulted in high yield of gas at the expense of the oil yield. For example, when the catalyst/tyre ratio increased from 0.25 to 1.0, the yield of gas increased from 30.5 to 49.9 wt.%, and the oil yield decreased nearly two-fold from 31.6 to 12.7 wt.%. The concentration of light naphtha (boiling point < 160 degrees C) was also investigated in this study. And the high catalyst/tyre ratio favored to increase the concentration of light naphtha (< 160 degrees C) in oil. In order to study the composition of derived oil, a distilled fraction (< 280 degrees C), which was 92.5 wt.% of the oil obtained from catalytic pyrolysis of scrap tyre at a pyrolysis temperature, catalytic temperature and catalyst/tyre ratio of 500, 400 degrees C and 0.5, respectively, was analyzed with gas chromatography/mass spectrometry (GC/MS). The distillate was found to contain 1.23 wt.% benzene, 9.35 wt.% toluene, 3.68 wt.% ethylbenzene, 12.64 wt.% xylenes, 1.81 wt.% limonene and 13.89 wt.% PAHs, etc., where the single ring aromatics represented a significant potential use as chemicals. PMID:16704900

Shen, Boxiong; Wu, Chunfei; Wang, Rui; Guo, Binbin; Liang, Cai

2006-09-21

367

Surface properties of alumino-silicate single-walled nanotubes of the imogolite type.  

PubMed

An IR spectroscopy study is reported on the nature and accessibility of external and internal surfaces of single-walled alumino-silicate nanotubes (NTs) of the imogolite type. NTs form bundles with hexagonal symmetry, in which three kinds of surfaces may be figured out: surface A is the inner surface of NTs; surface B is that between three aligned NTs in the hexagonal packing; and surface C arises from slit mesopores between bundles. Two materials were considered: proper imogolite (IMO, (OH)3Al2O3SiOH) and its methylated analogue, (Me-IMO, (OH)3Al2O3SiCH3). The chemical nature of the outer surface of NTs is the same in both materials, i.e. a curved gibbsite sheet with both Al-OH-Al and Al-O-Al groups and an amphoteric character. The inner surface is very hydrophilic in IMO NTs, lined by closely packed silanols, and hydrophobic in Me-IMO, all silanols being replaced by -SiCH3 groups. The change in chemical composition is accompanied by an increment in pore size, about 1.0 nm in IMO, and ca. 2.0 nm in Me-IMO, which implies a change in the accessibility of the B surface, not available to any molecule in IMO, and accessible in Me-IMO to small molecules like water, due to larger pores between NTs. Aluminol species at the B surface display an acidic nature, in contrast with that of the same species at surface C, because of a confinement effect. PMID:23788080

Bonelli, Barbara; Armandi, Marco; Garrone, Edoardo

2013-08-28

368

A new titanium-bearing calcium aluminosilicate phase. 1: Meteoritic occurrences and formation in synthetic systems  

NASA Astrophysics Data System (ADS)

A new titanium-bearing calcium aluminosilicate mineral has been identified in coarse-grained calcium-aluminum-rich inclusions (CAIs) from carbonaceous chondrites. The formula for this phase, which we have temporarily termed 'UNK,' is Ca3Ti(Al,Ti)2(Si,Al)3O14, and it is present in at least 8 of the 20 coarse-grained CAIs from the Allende CV3 chondrite examined as part of this project. The phase occurs in Types A and B1 inclusions as small tabular crystal oriented along two mutually perpendicular planes in melilite. UNK crystallizes from melts in dynamic crystallization experiments conducted in air from four bulk compositions modeled after Types A, B1, B2 and C inclusions. Cooling rates resulting in crystallization of UNK ranged from 0.5 to 200 C/h from maximum (initial) temperatures of 1375 to 1580 C. Only below 1190 C does UNK itself begin to crystallize. To first order, the presence or absence of UNK from individual experiments can be understood in terms of the compositions of residual melts and nucleation probabilities. Compositions of synthetic and meteoritic UNK are very similar in terms of major oxides, differing only in the small amounts of trivalent Ti(7-13% of total Ti) in meteoritic samples. UNK crystallized from the Type A analog is similar texturally to that found in CAIs, although glass, which is typically associated with synthetic UNK, is not observed in the meteoritic occurrences. A low Ti end-member of UNK ('Si-UNK') with a composition near that of Ca3Al2Si4O14 was produced in a few samples from the Type B1 analog. This phase has not been found in the meteoritic inclusions.

Paque, Julie M.; Beckett, John R.; Barber, David J.; Stolper, Edward M.

1994-09-01

369

Aluminosilicate-based sealants for SOFCs and other electrochemical applications - A brief review  

NASA Astrophysics Data System (ADS)

Among different designs of solid oxide fuel cells (SOFCs), planar design is the most promising due to easier fabrication, improved performance and relatively high power density. In planar SOFCs and other solid-electrolyte devices, gas-tight seals must be formed along the edges of each cell and between the stack and gas manifolds. For a sealant to work effectively in high-temperature SOFC environment, equilibrium needs to be achieved amid its mechanical properties and flow behavior so that it does not only maintain its hermeticity at high temperature but is also able to reduce mechanical stresses generated in the seal during thermal cycling. The most common sealants based on glass or glass-ceramic materials have been shown to operate in fuel cells for more than 1000 h with no significant degradation. Analysis of the current literature sources demonstrated that from thermal and chemical stability points of view, silicate based glass systems are more suitable than borate and borosilicate glass systems. In this work, different glass-ceramic (GC) compositions based on alkaline- and alkaline-earth aluminosilicate-based glass systems are reviewed with a special emphasis on their thermal, chemical, mechanical, and electrical properties. Based on these considerations, glass composition design approaches are provided that aid in search of the best seal glasses satisfying the rigid functional requirements. Among all the glass systems studied, a pyroxene based CaO-MgO-SrO-BaO-La2O3-Al2O3-SiO2 seal GC compositions have been specifically discussed because those have achieved appropriate thermal and chemical properties along with high stability. Approaches for further developments and optimization of GC sealants are briefly discussed.

Tulyaganov, Dilshat U.; Reddy, Allu Amarnath; Kharton, Vladislav V.; Ferreira, Jos M. F.

2013-11-01

370

A new titanium-bearing calcium aluminosilicate phase. 1: Meteoritic occurrences and formation in synthetic systems  

NASA Technical Reports Server (NTRS)

A new titanium-bearing calcium aluminosilicate mineral has been identified in coarse-grained calcium-aluminum-rich inclusions (CAIs) from carbonaceous chondrites. The formula for this phase, which we have temporarily termed 'UNK,' is Ca3Ti(Al,Ti)2(Si,Al)3O14, and it is present in at least 8 of the 20 coarse-grained CAIs from the Allende CV3 chondrite examined as part of this project. The phase occurs in Types A and B1 inclusions as small tabular crystal oriented along two mutually perpendicular planes in melilite. UNK crystallizes from melts in dynamic crystallization experiments conducted in air from four bulk compositions modeled after Types A, B1, B2 and C inclusions. Cooling rates resulting in crystallization of UNK ranged from 0.5 to 200 C/h from maximum (initial) temperatures of 1375 to 1580 C. Only below 1190 C does UNK itself begin to crystallize. To first order, the presence or absence of UNK from individual experiments can be understood in terms of the compositions of residual melts and nucleation probabilities. Compositions of synthetic and meteoritic UNK are very similar in terms of major oxides, differing only in the small amounts of trivalent Ti(7-13% of total Ti) in meteoritic samples. UNK crystallized from the Type A analog is similar texturally to that found in CAIs, although glass, which is typically associated with synthetic UNK, is not observed in the meteoritic occurrences. A low Ti end-member of UNK ('Si-UNK') with a composition near that of Ca3Al2Si4O14 was produced in a few samples from the Type B1 analog. This phase has not been found in the meteoritic inclusions.

Paque, Julie M.; Beckett, John R.; Barber, David J.; Stolper, Edward M.

1994-01-01

371

A New Titanium-Bearing Calcium Aluminosilicate Phase. 1; Meteoritic Occurrences and Formation in Synthetic Systems  

NASA Technical Reports Server (NTRS)

A new titanium-bearing calcium aluminosilicate mineral has been identified in coarse-grained calcium-aluminum-rich inclusions (CAIs) from carbonaceous chondrites. The formula for this phase, which we have temporarily termed "UNK," is Ca3Ti(AlTi)2(Si,Al)3O14, and it is present in at least 8 of the 20 coarse-grained CAIs from the Allende CV3 chondrite examined as part of this project. The phase occurs in Types A and B1 inclusions as small tabular crystals oriented along two mutually perpendicular planes in melilite. UNK crystallizes from melts in dynamic crystallization experiments conducted in air from four bulk compositions modeled after Types A, B1, B2 and C inclusions. Cooling rates resulting in crystallization of UNK ranged from 0.5 to 200 C/h from maximum (initial) temperatures of 1375 to 1580 C. Only below 1190 C does UNK itself begin to crystallize. To first order, the presence or absence of UNK from individual experiments can be understood in terms of the compositions of residual melts and nucleation probabilities. Compositions of synthetic and meteoritic LINK are very similar in terms of major oxides, differing only in the small amounts of trivalent Ti (7-13% of total Ti) in meteoritic samples. UNK crystallized from the Type A analog is similar texturally to that found in CAls, although glass, which is typically associated with synthetic UN& is not observed in meteoritic occurrences. A low Ti end-member of UNK ("Si-UNK") with a composition new that of Ca3Al2Si4O14 was produced in a few samples from the Type B1 analog. This phase has not been found in the meteoritic inclusions.

Paque, Julie M.; Beckett, John R.; Barber, David J.; Stolper, Edward M.

1994-01-01

372

Synthesis of core-shell structured zeolite-A@mesoporous silica composites for butyraldehyde adsorption.  

PubMed

A simple sol-gel process is followed to construct a thin layer of mesoporous silica shell core-shell structure on micrometer sized and nanometer sized zeolite A (micro-zeolite A@SiO2 and nano-zeolite A@SiO2 respectively). Further thickness of the silica shells has been tuned from 20 to 50 nm while the zeolite A particle size changes from nanometer to micrometer. Pores of the silica shells arranged orderly on the crystal-faces of zeolite-A cores. Typically, adsorption amount of the butyraldehyde towards these core-shell composite materials is investigated well and is verified to be almost double than that of the pristine zeolite A. Interestingly the nano-zeolite A core containing core-shell composite absorbs maximum butyraldehyde (314 mg/g) compared to the micro-zeolite A (266 mg/g), even if the mesoporous shell thickness of the nano-zeolite A@SiO2 composites is less (20 nm) than that of micro-zeolite A@SiO2 (50 nm). Both of these values are significantly larger than the pristine zeolite A (nano-zeolite A; 151 mg/g and micro-zeolite A; 146 mg/g). PMID:24910060

Yu, Haijun; Lv, Yingying; Ma, Kuoyan; Wang, Changguo; Xue, Zhaoteng; Zhao, Yujuan; Deng, Yonghui; Dai, Ya; Zhao, Dongyuan

2014-08-15

373

Rotationally Molded Liquid Crystalline Polymers  

NASA Technical Reports Server (NTRS)

Rotational molding is a unique process for producing hollow plastic parts. Rotational molding offers low cost tooling and can produce very large parts with complicated shapes. Products made by rotational molding include water tanks with capacities up to 20,000 gallons, truck bed liners, playground equipment, air ducts, Nylon fuel tanks, pipes, toys, stretchers, kayaks, pallets, and many others. Thermotropic liquid crystalline polymers are an important class of engineering resins employed in a wide variety of applications. Thermotropic liquid crystalline polymers resins are composed of semirigid, nearly linear polymeric chains resulting in an ordered mesomorphic phase between the crystalline solid and the isotropic liquid. Ordering of the rigid rod-like polymers in the melt phase yields microfibrous, self-reinforcing polymer structures with outstanding mechanical and thermal properties. Rotational molding of liquid crystalline polymer resins results in high strength and high temperature hollow structures useful in a variety of applications. Various fillers and reinforcements can potentially be added to improve properties of the hollow structures. This paper focuses on the process and properties of rotationally molded liquid crystalline polymers. This paper will also highlight the interactions between academia and small businesses in developing new products and processes.

Rogers, Martin; Scribben, Eric; Baird, Donald; Hulcher, Bruce

2002-01-01

374

Hierarchical mesoporous zeolites: direct self-assembly synthesis in a conventional surfactant solution by kinetic control over the zeolite seed formation.  

PubMed

By kinetic control over the zeolite seed formation, we report the direct fabrication of hierarchical mesoporous zeolites using hexadecyl trimethyl ammonium bromide (CTAB) as the soft template in a conventional solution route. Nanometer-sized, subnanocrystal-type zeolite seeds with a high degree of polymerization are essential to prevent the formation of a separate amorphous mesoporous phase and the phase separation between the mesophase and zeolite crystals in the presence of CTAB and a certain amount of ethanol. The mechanisms for the formation of hierarchically porous zeolites in the solution process, including the effect of mother liquid aging, formation of subnanocrystal zeolite seeds and their self-assembly effect with CTAB, and the role of ethanol are proposed and discussed in detail. The prepared mesoporous ZSM-5 zeolite showed much higher catalytic activity than conventional counterparts for aldol condensations involving large molecules, especially in the synthesis of vesidryl. PMID:22084015

Zhu, Yan; Hua, Zile; Zhou, Jian; Wang, Lijun; Zhao, Jinjin; Gong, Yun; Wu, Wei; Ruan, Meiling; Shi, Jianlin

2011-12-16

375

Methane dehydro-aromatization over Mo/HZSM-5 in the absence of oxygen: A multinuclear solid-state NMR study of the interaction between supported Mo species and HZSM-5 zeolite with different crystal sizes  

SciTech Connect

The interaction between Mo species and a conventionally microsized and particularly nanosized HZSM-5 support was studied by high-resolution multinuclear solid-state NMR techniques. As proved by {sup 27}Al and {sup 29}Si MAS as well as CP/MAS NMR investigations, this interaction was so strong that the framework aluminum of both microsized and nanosized HZSM-5 zeolites could be extracted. With increasing Mo loading, more nonframework aluminum, resonance at ca. 30 ppm, appeared in the {sup 27}Al MAS NMR spectrum of the Mo-loaded nanosized HZSM-5 catalyst. Meanwhile, this strong interaction led to the formation of more new Al{sub 2}(MoO{sub 4}){sub 3} crystallines on the nanosized HZSM-5 support than on the microsized HZSM-5 support. The appearance of Al{sub 2}(MoO{sub 4}){sub 3} crystallines resulted in fewer active catalysts for the methane dehydro-aromatization. The results of {sup 1}H MAS NMR using perfluorotributyl amine as a probe molecule demonstrated that Mo species preferentially reacted with the silanols and nonframework AlOH on the external surface of microsized and nanosized HZSM-5 zeolites. In addition, impregnated Mo species remained predominantly on the external surface of the nanosized HZSM-5 zeolite, although there was a possibility that they might migrate into the lattice channels of the microsized HZSM-5 zeolite. The migration of some Mo species into the zeolite channels might be beneficial for the conversion of methane to aromatics in the absence of oxygen.

Zhang, W.; Ma, D.; Han, X.; Liu, X.; Bao, X.; Guo, X.; Wang, X.

1999-12-10

376

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

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

Yokoyama, Takushi; Ueda, Akira; Kato, Koichi; Mogi, Katsumi; Matsuo, Shorin

2002-08-01

377

Crystalline 'Genes' in Metallic Liquids  

E-print Network

The underlying structural order that transcends the liquid, glass and crystalline states is identified using an efficient genetic algorithm (GA). GA identifies the most common energetically favorable packing motif in crystalline structures close to the alloy's Al-10 at.% Sm composition. These motifs are in turn compared to the observed packing motifs in the actual liquid structures using a cluster-alignment method which reveals the average topology. Conventional descriptions of the short-range order, such as Voronoi tessellation, are too rigid in their analysis of the configurational poly-types when describing the chemical and topological ordering during transition from undercooled metallic liquids to crystalline phases or glass. Our approach here brings new insight into describing mesoscopic order-disorder transitions in condensed matter physics.

Sun, Yang; Ye, Zhuo; Fang, Xiaowei; Ding, Zejun; Wang, Cai-Zhuang; Mendelev, Mikhail I; Ott, Ryan T; Kramer, M J; Ho, Kai-Ming

2014-01-01

378

Diffusion of an alkane molecule in siliceous zeolite beta Matthew Aronson  

E-print Network

1 Diffusion of an alkane molecule in siliceous zeolite beta Matthew was performed to study the diffusion of an alkane molecule in siliceous zeolite beta, as a function of chain length and temperature. The alkane was modeled

Shell, M. Scott

379

BTX abatement using Chilean natural zeolite: the role of Brnsted acid sites.  

PubMed

In wastewater treatment facilities, air quality is not only affected by conventional unpleasant odour compounds; toxic volatile organic compounds (VOCs) are also found. In this study, the adsorptive capacity of Chilean natural zeolite toward VOC removal was evaluated. Moreover, the influence of zeolite chemical surface properties on VOC elimination was also investigated. Three modified zeolite samples were prepared from a natural Chilean zeolite (53% clinoptilolite, 40% mordenite and 7% quartz). Natural and modified zeolite samples were characterised by nitrogen adsorption at 77 K, elemental analyses and X-ray fluorescence (XRF). Chemical modifications of natural zeolite showed the important role of Brnsted acid sites on the abatement of VOCs. The presence of humidity has a negative effect on zeolite adsorption capacity. Natural zeolites could be an interesting option for benzene, toluene and xylene vapour emission abatement. PMID:22907462

Alejandro, S; Valds, H; Manero, M-H; Zaror, C A

2012-01-01

380

Novel granular materials with microcrystalline active surfaces: waste water treatment applications of zeolite/vermiculite composites.  

PubMed

The application of zeolites as adsorbents for waste water management is limited by the facts that only synthetic zeolites have sufficient capacity and only natural zeolites can be manufactured in practical sizes for application, i.e. synthetic zeolites have too small a grain size to be used and natural zeolites have low adsorption capacities. This study seeks to resolve this problem by the manufacture of synthetic zeolites upon an expanded lamella matrix (vermiculite). The synthesized composite was tested to show whether it combined the useful properties of both natural and synthetic zeolites. The study compared: hydraulic conductivity, adsorption capacity and rate of attainment of equilibrium of the synthetic composite in comparison to both a natural and a synthetic zeolite. The results demonstrate that the vermiculite-based composite shows the same hydraulic properties as a natural clinoptilolite with similar grain size (2-5mm), however, the rate of adsorption and maximum coverage were improved by a factor of 4. PMID:17360021

Johnson, Christopher D; Worrall, Fred

2007-05-01

381

Single crystalline mesoporous silicon nanowires  

SciTech Connect

Herein we demonstrate a novel electroless etching synthesis of monolithic, single-crystalline, mesoporous silicon nanowire arrays with a high surface area and luminescent properties consistent with conventional porous silicon materials. These porous nanowires also retain the crystallographic orientation of the wafer from which they are etched. Electron microscopy and diffraction confirm their single-crystallinity and reveal the silicon surrounding the pores is as thin as several nanometers. Confocal fluorescence microscopy showed that the photoluminescence (PL) of these arrays emanate from the nanowires themselves, and their PL spectrum suggests that these arrays may be useful as photocatalytic substrates or active components of nanoscale optoelectronic devices.

Hochbaum, A.I.; Gargas, Daniel; Jeong Hwang, Yun; Yang, Peidong

2009-08-04

382

Structural studies on bovine ?-crystallin  

PubMed Central

The amino acid sequences around the cysteine residues in the lens protein, ?-crystallin, were studied. Fraction II of the ?-crystallin from calf lens (Bjrk, 1964) was used. The protein was oxidized with performic acid and then hydrolysed with trypsin. Six peptides containing cysteic acid were isolated. One of the peptides contained three residues of cysteic acid and the others contained one residue of cysteic acid. We conclude that there are eight unique residues of cysteic acid in the oxidized protein. Amino acid analysis suggests that there are also eight residues of cysteic acid in the molecule, which thus contains only one polypeptide chain. PMID:5165918

Croft, L. R.; Waley, S. G.

1971-01-01

383

Removal of heavy metals from mine waters by natural zeolites.  

PubMed

In this study, we investigated the removal of Fe, Pb, Cd, and Zn from synthetic mine waters by a natural zeolite. The emphasis was given to the zeolite's behavior toward a few cations in competition with each other. Pb was removed efficiently from neutral as well as from acidic solutions, whereas the uptake of Zn and Cd decreased with low pH and high iron concentrations. With increasing Ca concentrations in solution, elimination of Zn and Cd became poorer while removal of Pb remained virtually unchanged. The zeolite was stable in acidic solutions. Disintegration was only observed below pH 2.0. Forward- and back-titration of synthetic acidic mine water were carried out in the presence and absence of zeolite to simulate the effects of a pH increase by addition of neutralizing agents and a re-acidification which can be caused by subsequent mixing with acidic water. The pH increase during neutralization causes precipitation of hydrous ferric oxides and decreased dissolved metal concentrations. Zeolite addition further diminished Pb concentrations but did not have an effect on Zn and Cd concentrations in solution. During re-acidification of the solution, remobilization of Pb was weaker in the presence than in the absence of zeolite. No substantial differences were observed for Fe, Cd, and Zn immobilization. The immobilization of the metals during pH increase and the subsequent remobilization caused by re-acidification can be well described by a geochemical equilibrium speciation model that accounts for metal complexation at hydrous ferric oxides, for ion exchange on the zeolite surfaces, as well as for dissolution and precipitation processes. PMID:16047799

Wingenfelder, Ulla; Hansen, Carsten; Furrer, Gerhard; Schulin, Rainer

2005-06-15

384

doi:10.1016/S0016-7037(02)00026-7 The distribution of sodium ions in aluminosilicate glasses: A high-field Na-23 MAS and 3Q  

E-print Network

connectivity among framework cations and oxygens in aluminosilicate and borosilicate glasses using nucleardoi:10.1016/S0016-7037(02)00026-7 The distribution of sodium ions in aluminosilicate glasses in silicate glasses and melts and their distributions have strong implications for the dynamic and static

Puglisi, Joseph

385

JOURNAL DE PHYSIQUE Colloque C6, supplment au n" 8, Tome 39, aot 1978, page C6-936 MAGNETIC PROPERTIES OF AMORPHOUS MANGANESE ALUMINOSILICATES : SPIN-GLASS LIKE  

E-print Network

PROPERTIES OF AMORPHOUS MANGANESE ALUMINOSILICATES : SPIN-GLASS LIKE BEHAVIOUR AT LOW TEMPERATURE « 3E9 K3C and remanent magnetization of aluminosilicate glasses MhO.Al203Si02 with atomic Mn concentrations 18.9 % and 15 between Mn + ions, the magnetic pro- perties are very similar to those of spin--glass alloys. Recent

Boyer, Edmond

386

Polycrystalline MFI zeolite membranes: xylene pervaporation and its implication on membrane microstructure  

Microsoft Academic Search

This paper reports experimental results on pervaporation of pure xylene isomers and their binary mixtures through ?-alumina-supported zeolite MFI membranes. The membranes were permeable for all xylene isomers. Intensive fouling of the zeolite membrane was observed during the pervaporation experiments due to strong interaction of xylene molecules with the zeolite pores via ?-complexation. The pervaporation flux of pure xylene isomers

Karsten Wegner; Junhang Dong; Y. S Lin

1999-01-01

387

FriedelCrafts acylation of aromatics and heteroaromatics by beta zeolite  

Microsoft Academic Search

FriedelCrafts acylation of aromatic compounds such as anisole, 2-methoxynaphthalene, veratrole, isobutylbenzene and aromatic heterocycle compounds such as pyrrole, furan, thiophene, benzothiophene with different acid anhydrides is carried out in the batch mode with different forms of beta zeolite. The micronized beta zeolite shows manifold activity over normal zeolite in acylation reactions of aromatics.

Mannepalli Lakshmi Kantam; Kalluri Venkata Sri Ranganath; Mutyala Sateesh; Kota Balaji Shiva Kumar; Boyapati Manoranjan Choudary

2005-01-01

388

Oxygen transport in zeolite Y measured by quenching of encapsulated tris(bipyridyl)ruthenium  

E-print Network

reserved. Keywords: Oxygen sensor; Zeolite diffusion; Zeolite confinement 1. Introduction The microporousOxygen transport in zeolite Y measured by quenching of encapsulated tris(bpy)2þ 3 ) by oxygen. Oxygen saturated solutions of Ru(bpy)2þ 3 typically show about 70% quenching (I0=I

Dutta, Prabir K.

389

Synthesis and characterization of MCM-49/ZSM-35 composite zeolites in the hexamethyleneimine and cyclohexamine system  

E-print Network

Composite zeolites, especially micro/microporous composites [1­8] and micro/mesoporous composites [9Synthesis and characterization of MCM-49/ZSM-35 composite zeolites in the hexamethyleneimine ZSM-35 Composite zeolite Hexamethyleneimine Cyclohexamine a b s t r a c t A novel route for synthesis

Bao, Xinhe

390

DOI: 10.1002/anie.200702628 Aluminum Siting in Silicon-Rich Zeolite Frameworks: A Combined  

E-print Network

Zeolites DOI: 10.1002/anie.200702628 Aluminum Siting in Silicon-Rich Zeolite Frameworks: A Combined High-Resolution 27 Al NMR Spectroscopy and Quantum Mechanics/Molecular Mechanics Study of ZSM-5- graphic position of aluminum in zeolite frameworks governs the location of the active sites, which in turn

Sklenak, Stepan

391

Zeolites in catalysis. (Latest citations from the EI Compendex plus database). Published Search  

SciTech Connect

The bibliography contains citations concerning the preparation, properties, and activity of zeolites used as catalysts in chemical reactions and chemical apparatus. Topics include catalytic cracking, reduction, processing, and various catalytic effects of zeolites and zeolite-containing compounds for a wide variety of applications. (Contains 250 citations and includes a subject term index and title list.)

Not Available

1993-08-01

392

Exploration of molecular sieve zeolites for the cooling of building with solar energy  

Microsoft Academic Search

The usefulness of molecular sieve zeolites for solar sorption heating and cooling has been investigated. Two different approaches have been used, one in which the temperature of the zeolite is uniform, the other in which a temperature gradient is established across the zeolite. With one-square-foot test panels using the uniform temperature approach, overall engineering efficiencies as high as 75% for

D. I. Tchernev

1977-01-01

393

Penentuan kapasiti dan jenis pencerapan Zeolit asli terhadap bahan pencelup sintetik  

Microsoft Academic Search

Abstrak. Zeolit yang dikenali sebagai penapis molekul mempunyai sifat keliangan dan luas permukaan tinggi telah digunakan sebagai bahan penjerap untuk menjerap bahan pencelup daripada air sisa berwarna. Zeolit mordenit asli yang berasal dari Indonesia telah diubahsuai kepada bentuk yang bersifat bes dan dikaji sifat penjerapannya terhadap bahan pencelup sintetik bes kuning 11. Seterusnya, jenis penjerapan sampel zeolit terhadap bahan pencelup

Chai Mee Kin; Asiah Hussain; Pengajian Sains; Jalan Kajang-Puchong

394

Extrusion of zeolites: Properties of catalysts with a novel aluminium phosphate sintermatrix  

Microsoft Academic Search

A novel type of mechanically strong zeolite extrudates is introduced, in which the zeolite crystals, here ZSM-5, are embedded in a sintermatrix of aluminium phosphate with the crystal structure of tridymite. The pore size distribution in the matrix can be tailored through both, the choice of the size of the embedded particles and their amount in the extrudates. At zeolite

Jens Freiding; Florina-Corina Patcas; Bettina Kraushaar-Czarnetzki

2007-01-01

395

MINERALOGY AND PETROGRAPHY OF NEW OCCURENCES DEPOSITS OF THE ZEOLITIC TUFF IN NORTHEAST JORDAN  

Microsoft Academic Search

The occurrences deposits of the zeolitic tuff were studied in four areas through detailed geological mapping at a scale 1:50.000 in northeast Jordan and through exploration project. These deposits covered large areas and characterized by rich content, lateral and vertical homogenous distribution of the zeolite minerals. The zeolites are an abundant constituent in these deposits, which form more than 50%

K. Tarawneh

396

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

ERIC Educational Resources Information Center

Presents experiments that introduce students to the myriad properties of zeolites using the sodium form of zeolite A (Na-A) from laundry detergent. Experiments include extracting Na-A from detergent, water softening properties, desiccant properties, ion-exchange properties, and Zeolite HA as a dehydration catalyst. (JRH)

Smoot, Alison L.; Lindquist, David A.

1997-01-01

397

ZEOLITE PERFORMANCE AS AN ANION EXCHANGER FOR ARSENIC SEQUESTRATION IN WATER  

EPA Science Inventory

Zeolites are well known for their use in ion exchange and acid catalysis reactions. The use of zeolites in anion or ligand exchange reactions is less studied. The NH4+ form of zeolite Y (NY6, Faujasite) has been tested in this work to evaluate its performance for arsenic removal...

398

Toward a Database of Hypothetical Zeolite Structures David J. Earl, and Michael W. Deem*,  

E-print Network

Toward a Database of Hypothetical Zeolite Structures David J. Earl, and Michael W. Deem the sampling. We discuss construction of a database of hypothetical zeolite frameworks with this approach and discuss how the database may be used to search for new zeolite structures with specific material

Earl, David J.

399

Hafnium in peralkaline and peraluminous boro-aluminosilicate glass, and glass subcomponents: a solubility study.  

SciTech Connect

A relationship between the solubility of hafnia (HfO2) and the host glass composition was explored by determining the solubility limits of HfO2 in peralkaline and peraluminous borosilicate glasses in the system SiO2-Al2O3-B2O3-Na2O, and in glasses in the system SiO2-Na2O-Al2O3 in air at 1450 C. The only Hf-bearing phase to crystallize in the peralkaline borosilicate melts is hafnia, while in the boron-free melts sodium-hafnium silicates crystallize. All peraluminous borosilicate melts crystallize hafnia, but the slightly peraluminous glasses also have sector-zoned hafnia crystals that contain Al and Si. The more peraluminous borosilicate glasses also crystallize a B-containing mullite. The general morphology of the hafnia crystals changes as peralkalinity (Na2O/(Na2O+Al2O3)) decreases, as expected in melts with increasing viscosity. In all of the glasses with Na2O > Al2O3, the solubility of hafnia is linearly and positively correlated with Na2O/(Na2O + Al2O3) or Na2O - Al2O3 (excess sodium), despite the presence of 5 to 16 mol% B2O3. The solubility of hafnia is higher in the sodium-aluminum borosilicate glasses than in the sodium-aluminosilicate glasses, suggesting that the boron is enhancing the effect that excess sodium has on the incorporation of Hf into the glass structure. The results of this solubility study are compared to other studies of high-valence cation solubility in B-free silicate melts. From this, for peralkaline B-bearing glasses, it is shown that, although the solubility limits are higher, the solution behavior of hafnia is the same as in B-free silicate melts previously studied. By comparison, also, it is shown that in peraluminous melts, there must be a different solution mechanism for hafnia: different than for peralkaline sodium-aluminum borosilicate glasses and different than for B-free silicate melts studied by others.

Davis, Linda L.; Darab, John G.; Qian, Maoxu; Zhao, Donggao; Palenik, Christopher S.; Li, Hong; Strachan, Denis M.; Li, Liyu

2003-10-15

400

[Adsorption of phenol chemicals by surfactant-modified zeolites].  

PubMed

Two kinds of zeolites were prepared from fly ash and modified by surfactant subsequently. Surfactant-modified zeolites were studied for adsorption of phenol chemicals (phenol, p-chlorphenol, bisphenol A). It showed that the adsorption affinity of zeolite to phenol chemicals was significantly improved after surfactant modification. The adsorption isotherms of phenol chemicals were well fitted by the Langmuir isotherm. For the two surfactant-surfactant modified zeolites, the maximum adsorption amounts of phenol, p-chlorphenol, and bisphenol A calculated from the Langmuir equation were 37.7, 52.36, 90.9 mg x g(-1) and 10.7, 22.83, 56.8 mg x g(-1), respectively. When pH values of solutions were higher than the pK(a) values of phenol chemicals, the removal efficiencies were getting higher with the increase of pH values. The octanol/water partition coefficient (K(ow)) was also found to be an important factor affecting adsorption of phenol chemicals by the modified zeolites. Higher K(ow) value, which means the greater hydrophobicity of the chemicals, resulted in a higher removal. PMID:23379165

Xie, Jie; Wang, Zhe; Wu, De-Yi; Li, Chun-Jie

2012-12-01

401

Risk assessment for the transportation of radioactive zeolite liners  

SciTech Connect

The risk is estimated for the shipment of radioactive zeolite liners in support of the Zeolite Vitrification Demonstration Program currently underway at Pacific Northwest Laboratory under the sponsorship of the US Department of Energy. This program will establish the feasibility of zeolite vitrification as an effective means of immobilizing high-specific-activity wastes. In this risk assessment, it is assumed that two zeolite liners, each loaded around July 1, 1981 to 60,000 Ci, will be shipped by truck around January 1, 1982. However, to provide a measure of conservatism, each liner is assumed to initially hole 70,000 Ci, with the major radioisotopes as follow: /sup 90/Sr = 3000 Ci, /sup 134/Cs = 7000 Ci, /sup 137/Cs = 60,000 Ci. Should shipment take place with essentially no delay after initial loading (regardless of loading date), the shipment loading would be only 2.7% higher than that for the assumed six-month delay. This would negligibly affect the overall risk. As a result of this risk assessment, it is concluded that the transport of the radioactive zeolite liners from TMI to PNL by truck can be conducted at an insignificant level of risk to the public.

Not Available

1982-01-01

402

Copper removal using bio-inspired polydopamine coated natural zeolites.  

PubMed

Herein, for the first time, natural clinoptilolite-rich zeolite powders modified with a bio-inspired adhesive, polydopamine (PDA), have been systematically studied as an adsorbent for copper cations (Cu(II)) from aqueous solution. Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) revealed successful grafting of PDA onto the zeolite surface. The effects of pH (2-5.5), PDA treatment time (3-24h), contact time (0 to 24h) and initial Cu(II) ion concentrations (1 to 500mgdm(-3)) on the adsorption of Cu(II) ions were studied using atomic absorption spectroscopy (AAS) and neutron activation analysis (NAA). The adsorption behavior was fitted to a Langmuir isotherm and shown to follow a pseudo-second-order reaction model. The maximum adsorption capacities of Cu(II) were shown to be 14.93mgg(-1) for pristine natural zeolite and 28.58mgg(-1) for PDA treated zeolite powders. This impressive 91.4% increase in Cu(II) ion adsorption capacity is attributed to the chelating ability of the PDA on the zeolite surface. Furthermore studies of recyclability using NAA showed that over 50% of the adsorbed copper could be removed in mild concentrations (0.01M or 0.1M) of either acid or base. PMID:24731937

Yu, Yang; Shapter, Joseph G; Popelka-Filcoff, Rachel; Bennett, John W; Ellis, Amanda V

2014-05-30

403

Playing with dye molecules at the inner and outer surface of zeolite L  

NASA Astrophysics Data System (ADS)

Plants are masters of transforming sunlight into chemical energy. In the ingenious antenna system of the leaf, the energy of the sunlight is transported by chlorophyll molecules for the purpose of energy transformation. We have succeeded in reproducing a similar light transport in an artificial system on a nano scale. In this artificial system, zeolite L cylinders adopt the antenna function. The light transport is made possible by specifically organized dye molecules, which mimic the natural function of chlorophyll. Zeolites are crystalline materials with different cavity structures. Some of them occur in nature as a component of the soil. We are using zeolite L crystals of cylindrical morphology which consist of a continuous one-dimensional tube system and we have succeeded in filling each individual tube with chains of joined but noninteracting dye molecules. Light shining on the cylinder is first absorbed and the energy is then transported by the dye molecules inside the tubes to the cylinder ends. We expect that our system can contribute to a better understanding of the important light harvesting process which plants use for the photochemical transformation and storage of solar energy. We have synthesized nanocrystalline zeolite L cylinders ranging in length from 300 to 3000 nm. A cylinder of 800 nm diameter, e.g. consists of about 150?000 parallel tubes. Single red emitting dye molecules (oxonine) were put at each end of the tubes filled with a green emitting dye (pyronine). This arrangement made the experimental proof of efficient light transport possible. Light of appropriate wavelength shining on the cylinder is only absorbed by the pyronine and the energy moves along these molecules until it reaches the oxonine. The oxonine absorbs the energy by a radiationless energy transfer process, but it is not able to send it back to the pyronine. Instead it emits the energy in the form of red light. The artificial light harvesting system makes it possible to realize a device in which different dye molecules inside the tubes are arranged in such a way that the whole visible spectrum can be used by conducting light from blue to green to red without significant loss. Such a material could conceivably be used in a dye laser of extremely small size. The light harvesting nanocrystals are also investigated as probes in near-field microscopy, as materials for new imaging techniques and as luminescent probes in biological systems. The extremely fast energy migration, the pronounced anisotropy, the geometrical constraints and the high concentration of monomers which can be realized, have great potential in leading to new photophysical phenomena. Attempts are being made to use the efficient zeolite-based light harvesting system for the development of a new type of thin-layer solar cell in which the absorption of light and the creation of an electron-hole pair are spatially separated as in the natural antenna system of green plants. Synthesis, characterization and applications of an artificial antenna for light harvesting within a certain volume and transport of the electronic excitation energy to a specific place of molecular dimension has been the target of research in many laboratories in which different approaches have been followed. To our knowledge, the system developed by us is the first artificial antenna which works well enough to deserve this name. Many other highly organized dye-zeolite materials of this type can be prepared by similar methods and are expected to show a wide variety of remarkable properties. The largely improved chemical and photochemical stability of dye molecules inserted in an appropriate zeolite framework allows us to work with dyes which otherwise would be considered uninteresting because of their lack of stability. We have developed two methods for preparing well-defined dye-zeolite materials, one of them working at the solid-liquid and the other at the solid-gas interface. Different approaches for preparing similar materials are in situ synthesis (ship in a bottle) or different types of crystalliz

Calzaferri, Gion; Brhwiler, Dominik; Megelski, Silke; Pfenniger, Michel; Pauchard, Marc; Hennessy, Brian; Maas, Huub; Devaux, Andr; Graf, Urs

2000-06-01

404

Synthesis of MCM-22 zeolite using rice husk as a silica source under varying-temperature conditions.  

PubMed

In this study, rice husk, an abundant agricultural byproduct, was utilized as an alternative silica source for the synthesis of MCM-22. The zeolite with high crystalline was synthesized using a three-stage varying-temperature hydrothermal method. The prepared silica and MCM-22 were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results showed that the duration required for zeolite crystallization was significantly decreased under varying-temperature conditions. The MCM-22 was in the form of thin platelet-like crystals, and no amorphous material existed in the framework of the MCM-22 after calcination and ammonium exchange. Cationic brilliant red 5GN, a basic dye used in the wool and blanket factories for fiber dyeing, was selected as the adsorptive to study the adsorption performance of the MCM-22. Adsorption experiments indicated that the maximum extent of adsorption was obtained at pH of 10, contact time of 60 min, and MCM-22 dose of 1.0 g/L. The adsorption kinetic has been described by first-order and pseudo-second-order models. It was observed that the rate of dye adsorption followed pseudo-second-order model. PMID:22226498

Cheng, Yue; Lu, Mang; Li, Jiansheng; Su, Xiaoyuan; Pan, Shunlong; Jiao, Chuang; Feng, Maohua

2012-03-01

405

Zeolite-inspired low-k dielectrics overcoming limitations of zeolite films.  

PubMed

Spin-on zeolite films deposited from Silicalite-1 nanocrystal suspensions prepared by hydrothermal treatment of clear solutions have the required properties for insulating media in microelectronics. However, on the scale of the feature sizes in on-chip interconnects of a few tens of nanometers, their homogeneity is still insufficient. We discovered a way to overcome this problem by combining the advantages of the clear solution approach of Silicalite-1 synthesis with a sol-gel approach. A combination of tetraethyl orthosilicate and methyltrimethoxysilane silica sources was hydrolyzed and cocondensed in the presence of an aqueous tetraalkylammonium hydroxide template. The resulting suspension of nanoparticles of a few nanometers in size together with residual oligomeric silica species were spun onto support. The final zeolite-inspired low-k films (ZLK) with respect to pore size and homogeneity satisfied all requirements and presented excellent hydrophobicity, stiffness, and dielectric constant. The size and content of initially formed nanoparticles and the spatial hindrance promoted by occluded tetraalkylammonium molecules were found to be crucial elements in the definition of the final pore network. PMID:19053487

Eslava, Salvador; Urrutia, Jone; Busawon, Abheesh N; Baklanov, Mikhail R; Iacopi, Francesca; Aldea, Steliana; Maex, Karen; Martens, Johan A; Kirschhock, Christine E A

2008-12-24

406

Separation of p-xylene and ethylbenzene from C/sub 8/ aromatics using medium-pore zeolites  

SciTech Connect

The author discusses medium-pore ZSM-5 zeolites found to be excellent for the separation of p-xylene and ethylbenzene from C/sub 8/ aromatics. Their adsorption capacity and selectivity for p-xylene were high. The selectivity for p-xylene over ethylbenzene was 5.5 at the optimum SiO/sub 2//Al/sub 2/O/sub 3/ of 700. The competitive adsorption capacity for p-xylene from a simulated reformer product was 120 mg/g. The p-xylene selectivity increased sharply and then leveled off when p-xylene loadings reached 50 and 90 mg/g, respectively. The high p-xylene selectivity and its dependence on p-xylene loading are believed to be related to the unique packing of p-xylene in the crystalline cavities.

Yan, T.Y. (Mobil Research and Development Corp., Princeton, NJ (USA). Central Research Div.)

1989-05-01

407

Separation of rho-xylene and ethylbenzene from C/sub 8/ aromatics using medium pore zeolites  

SciTech Connect

Medium pore ZSM-5 zeolites were found to be excellent for separation of p-xylene and ethylbenzene from C/sub 8/ aromatics. Their adsorption capacity and selectivity for p-xylene were high. The selectivity for p-xylene over ethylbenzene {beta}/sub p/e/, was 5.5 at the optimum SiO/sub 2//Al/sub 2/O/sub 3/ of 700. The competitive adsorption capacity for p-xylene from a simulated reformer product was 120 mg/g. The p-xylene selectivity {beta}/sub p/o'/ increased sharply and then leveled off when p-xylene loadings reached 50 mg/g and 90 mg/g, respectively. The high p-xylene selectivity and its dependence on p-xylene loading are believed to be related to the unique packing of p-xylene in the crystalline cavities.

Yan, T.Y. (Mobil Research and Development Corp., Central Research Lab., P.O. Box 1025, Princeton, NJ (US))

1988-01-01

408

One-step hydrothermal synthesis of manganese-containing MFI-type zeolite, Mn-ZSM-5, characterization, and catalytic oxidation of hydrocarbons.  

PubMed

Manganese-containing MFI-type Mn-ZSM-5 zeolite was synthesized by a facile one-step hydrothermal method using tetrapropylammonium hydroxide (TPAOH) and manganese(III)-acetylacetonate as organic template and manganese salts, respectively. A highly crystalline MFI zeolite structure was formed under pH = 11 in 2 days, without the need for additional alkali metal cations. Direct evidence of the incorporation of Mn in the zeolite framework sites was observed by performing structure parameter refinements, supported by data collected from other characterization techniques such as IR, Raman, UV-vis, TGA, N2-adsorption, SEM, TEM, EDAX, and XPS. UV-vis spectra from the unique optical properties of Mn-ZSM-5 show two absorption peaks at 250 and 500 nm. The absorption varies in different atmospheres accompanied by a color change of the materials due to oxygen evolution. Raman spectra show a significant and gradual red shift from 383 cm(-1) to 372 cm(-1) when the doping amount of Mn is increased from 0 to 2 wt %. This suggests a weakened zeolite structural unit induced by the Mn substitution. The catalytic activity was studied in both gas-phase benzyl alcohol oxidation and toluene oxidation reactions with remarkable oxidative activity presented for the first time. These reactions result in a 55% yield of benzaldehyde, and 65% total conversion of toluene to carbon dioxide for the 2% Mn-ZSM-5. Temperature programmed reduction (TPR) using CO in He demonstrates two reduction peaks: one between 300 and 500 C and the other between 500 and 800 C. The first reduction peak, due to manganese-activated oxidation sites shifted from higher temperature to lower temperature, and the peak intensity of CO2 rises when the dopant amount increases. For the first time, calculated photophysical properties of a model Mn(O-SiH3)4(-) compound, an Mn-embedded zeolite cluster, and model Mn oxides help to explain and interpret the diffuse reflectance spectroscopy of Mn-ZSM-5 zeolites. PMID:23679582

Meng, Yongtao; Genuino, Homer C; Kuo, Chung-Hao; Huang, Hui; Chen, Sheng-Yu; Zhang, Lichun; Rossi, Angelo; Suib, Steven L

2013-06-12

409

Synthetic Zeolites and Other Microporous Oxide Molecular Sieves  

NASA Astrophysics Data System (ADS)

Use of synthetic zeolites and other microporous oxides since 1950 has improved insulated windows, automobile air-conditioning, refrigerators, air brakes on trucks, laundry detergents, etc. Their large internal pore volumes, molecular-size pores, regularity of crystal structures, and the diverse framework chemical compositions allow "tailoring" of structure and properties. Thus, highly active and selective catalysts as well as adsorbents and ion exchangers with high capacities and selectivities were developed. In the petroleum refining and petrochemical industries, zeolites have made possible cheaper and lead-free gasoline, higher performance and lower-cost synthetic fibers and plastics, and many improvements in process efficiency and quality and in performance. Zeolites also help protect the environment by improving energy efficiency, reducing automobile exhaust and other emissions, cleaning up hazardous wastes (including the Three Mile Island nuclear power plant and other radioactive wastes), and, as specially tailored desiccants, facilitating the substitution of new refrigerants for the ozone-depleting chlorofluorocarbons banned by the Montreal Protocol.

Sherman, John D.

1999-03-01

410

Redeposited zeolitic rocks from the NE Rhodopes, Bulgaria  

NASA Astrophysics Data System (ADS)

The redeposited zeolitic rocks of Early Oligocene age in the NE Rhodopes, Bulgaria, are composed of zeolitic rock fragments. Material for the study was collected from four sections situated to the north of the Arda river, Haskovo district. These rocks occurred in a rhythmic series of sediments, occupying the interval between the products of two episodes of acidic volcanism (Lower Oligocene). They consist predominantly of subangular to subrounded clinoptilolitic rock fragments in which are preserved the specific relict textures of earlier zeolitized volcanic glass shards. The clinoptilolite content, which has been determined both under the microscope and by X-ray diffraction, varies between 10% and 80% but is usually about 50% by volume. Implications for the paleogeographic and tectonic regime of the area are considered.

Djourova, E. G.; Milakovska-Vergilova, Z. I.

1996-09-01

411

Computer simulations of benzene in faujasite-type zeolites  

SciTech Connect

The exact nature of the cation-benzene ring interaction is not yet known. In order to remedy this, energy minimization and Monte Carlo methods were used to probe the location and energetics of benzene in sodium zeolite-X and -Y. Sorption energies for the six-ring binding site in each of the zeolite models with the two forcefields (cff91 and cvff) are tabulated as function of Si/Al ratio. Both forcefields predict similar binding sites for each system; however, the final energies are sensitive to form and parameterization of the forcefield. Further work is needed to refine the forcefield for zeolite-sorbate interactions. 5 figs, 21 refs, 2 tabs.

Henson, N.J.; Cheetham, A.K. [California Univ., Santa Barbara, CA (United States). Dept. of Materials; Redondo, A. [Los Alamos National Lab., NM (United States); Levine, S.M.; Newsam, J.M. [Biosym Technologies Inc., San Diego, CA (United States)

1994-03-01

412

Mechanochemical approach for preparation of Mo-containing ?-zeolite  

NASA Astrophysics Data System (ADS)

The catalytically active solid materials were prepared by mechanochemical synthesis and impregnation. The starting material used as a support was ?-zeolite with a ratio SiO2/Al2O3=66. The molybdenum precursor was 12-molybdophosphoric heteropoly acid (HPMo). The samples were characterized by TPR and IR methods. The test reaction was thiophene hydrodesulfurization at atmospheric pressure. The interaction between HPMo and ?-zeolite in the catalyst sample, prepared by mechanochemical synthesis, is a weak one compared to that in the sample obtained on the basis of impregnation. The hydrodesulfurization activity of the milling sample is stabilized at a level about 50% higher than that of the sample prepared by impregnating HPMo on ?-zeolite. The higher hydrogenating activity of the mechanochemically treated sample is an additional advantage.

Kostova, N. G.; Spojakina, A. A.; Dutkov, E.; Bal, P.

2007-05-01

413

Multiple zeolite structures from one ionic liquid template.  

PubMed

This study reports the use of 1-butyl-3-methyl imidazolium methanesulfonate ionic liquid as a template in the synthesis of zeolites. It is found that the silicon source determines the formation of beta (BEA), mordenite framework inverted (MFI), or analcime (ANA) zeolites. Depending on this source, different preorganized complexes are obtained that drive the formation of the different zeolite structures. In the presence of ethanol, the ionic liquid form preorganized complexes that drive the formation of MFI. In its absence, BEA is obtained. Whereas, the large amount of sodium present when using sodium metasilicate leads to ANA formation. A molecular simulation study of the relative stability of the template-framework system and location of the template provides further insight into the mechanism of synthesis. PMID:23255393

Martnez Blanes, Jos Mara; Szyja, Bart?omiej M; Romero-Sarria, Francisca; Centeno, Miguel ngel; Hensen, Emiel J M; Odriozola, Jos Antonio; Ivanova, Svetlana

2013-02-01

414

The environmental applications of activated carbon/zeolite composite materials.  

PubMed

Over the past couple of years, the resurgence of placing an effective and sustainable amendment to combat against the auxiliary industrial entities, remains a highly contested agenda from a global point. With the renaissance of activated carbon, there has been a steadily growing interest in the research field. Recently, the adoption of zeolite composite, a prestigious advanced catalyst which formulates the enhancement of adsorption rate and hydrogen storage capability, has fore fronted to be a new growing branch in the scientific community. Confirming the assertion, this paper presents a state of art review of activated carbon/zeolite composite technology, its fundamental background studies, and environmental implications. Moreover, its major challenges together with the future expectation are summarized and discussed. Conclusively, the expanding of activated carbon/zeolite composite represents a potentially viable and powerful tool, leading to the plausible improvement of environmental preservation. PMID:21035101

Foo, K Y; Hameed, B H

2011-02-17

415

Hot isostatic pressing of glass-zeolite composites  

SciTech Connect

Glass-zeolite waste forms are being developed for immobilizing the chloride waste salt generated from the electrometallurgical treatment of spent fuel. Glass-zeolite composites with high densities were made using hot isostatic pressing (HIP) techniques. Processing parameters were investigated to yield desirable structural ceramic properties such as mechanical, chemical, and thermal stability. Limits for these parameters were determined by differential thermal and thermogravimetric analysis. The resulting ceramic properties such as bulk density, open or apparent porosity, and leach resistance were determined. In addition, phase equilibria and particle-size distribution were observed by optical light and electron microscopy. Pre-HIP processing techniques were also studied to ensure intimate mixing of the glass and zeolite powders. Particle size distributions resulting from dry blending procedure are appropriate for needed flow and packing characteristics.

Hash, M.C.; Pereira, C.; Lewis, M.A. [and others

1996-05-01

416

Water adsorption in hydrophilic zeolites: experiment and simulation.  

PubMed

We have measured experimental adsorption isotherms of water in zeolite LTA4A, and studied the regeneration process by performing subsequent adsorption cycles after degassing at different temperatures. We observed incomplete desorption at low temperatures, and cation rearrangement at successive adsorption cycles. We also developed a new molecular simulation force field able to reproduce experimental adsorption isotherms in the range of temperatures between 273 K and 374 K. Small deviations observed at high pressures are attributed to the change in the water dipole moment at high loadings. The force field correctly describes the preferential adsorption sites of water at different pressures. We tested the influence of the zeolite structure, framework flexibility, and cation mobility when considering adsorption and diffusion of water. Finally, we performed checks on force field transferability between different hydrophilic zeolite types, concluding that classical, non-polarizable water force fields are not transferable. PMID:24022609

Castillo, Juan Manuel; Silvestre-Albero, Juaquin; Rodriguez-Reinoso, Francisco; Vlugt, Thijs J H; Calero, Sofia

2013-10-28

417

Ring distributions in alkali- and alkaline-earth aluminosilicate framework glasses- a raman spectroscopic study  

USGS Publications Warehouse

Raman spectra of crystalline polymorphs of a number of tectosilicate minerals having various sizes of smallest rings of TO4 tetrahedra (T = Si, Al) have been investigated to identify the bands that are sensitive indicators of the smallest rings in the network. The information obtained from the Raman spectra of tectosilicate minerals (e.g., SiO2 polymorphs, NaAlSi3O8 (Ab), NaAlSiO4 (Ne), KAlSi3O8 (Or), and KAlSi2O6 (Lc)) is used to interpret the Raman spectra of the isochemical glasses. It is shown that the frequency of the dominant ??s (TOT) band in the spectra of both crystals and glasses is related to the dominant size of TO4 rings in the structure. In agreement with previous X-ray RDF work, it is found that in the glasses of Ab and Jd (NaAlSi2O6) compositions, six-membered rings of TO4 tetrahedra predominate. The Raman spectrum of Or glass, however, indicates that clusters of intermixed four- and six-membered rings of TO4 tetrahedra, similar to those existing in crystalline leucite, are also present in the glass. Raman evidence indicates that four-membered rings of TO4 tetrahedra predominate in the glass of An composition. Similarly, the higher frequency of the ??s (TOT) band in the spectrum of Ne glass as compared with the frequency the ??s (TOT) band in the spectra of crystalline cargenieite and nephelite indicates either an admixture of the four- and six-membered rings or the puckering of six-membered rings in the glass structure. ?? 1985.

Sharma, S.K.; Philpotts, J.A.; Matson, D.W.

1985-01-01

418

Influence of Crystal Expansion/Contraction on Zeolite Membrane Permeation  

SciTech Connect

X-ray diffraction was used to measure the unit cell parameters of B-ZSM-5, SAPO-34, and NaA zeolite powders as a function of adsorbate loading at 303 K, and in one case, at elevated temperatures. Most adsorbates expanded the zeolite crystals below saturation loading at 303 K: n-hexane and SF6 in B-ZSM-5, methanol and CO2 in SAPO-34, and methanol in NaA zeolite. As the loadings increased, the crystals expanded more. Changes in the unit cell volumes of B-ZSM-5 and SAPO-34 zeolite powders correlated with changes in permeation through zeolite membranes defects. When the zeolite crystals expanded or contracted upon adsorption, the defect sizes decreased or increased. In B-ZSM-5 membranes, the fluxes through defects decreased dramatically when n-hexane or SF6 adsorbed. In contrast, i-butane adsorption at 303 K contracted B-ZSM-5 crystals at low loadings and expanded them at higher loadings. Correspondingly, the flux through B-ZSM-5 membrane defects increased at low i-butane loadings and decreased at high loading because the defects increased in size at low loading and decreased at high loadings. At 398 K and 473 K, n-hexane expanded the B-ZSM-5 unit cell more as the temperature increased from 303 to 473 K. The silicalite-1 and B-ZSM-5 unit cell volumes expanded similarly upon n-hexane adsorption at 303 K; boron substitution had little effect on volume expansion.

Sorenson, Stephanie G [University of Colorado, Boulder; Payzant, E Andrew [ORNL; Noble, Richard D [University of Colorado, Boulder; Falconer, John L. [University of Colorado, Boulder

2010-01-01

419

Effect of natural and modified zeolite addition on anaerobic digestion of piggery waste.  

PubMed

The effect of natural and modified zeolites on the anaerobic degradation of acetate and methanol was evaluated by the determination of specific methane productivity (SMP) in batch minidigesters of 50 mL at doses of 0.01, 0.05 and 0.1 g of zeolite/g of VSS. The effects of the different zeolite concentrations were determined by the results of the SMP. A kinetic characterization with data of accumulated methane gas volume was also carried out. In the second phase of the study, the effects of natural and nickel zeolite concentrations were tested with piggery waste in laboratory scale digesters of 2.5 L operating at semi continuous mode, by increasing the organic load applied from 0.2 to 22.0 g TCOD/d corresponding to organic loading rates (OLR) of 0.1-8.8 g TCOD/l x d. A greater effect of modified zeolite on SMP was observed, with an increase of 8.5 times with magnesium zeolite, 4.4 times with cobalt zeolite and 2.8 times with nickel zeolite. Two phases were defined in the kinetic study and an increase of more than 2 times the apparent constant of digesters with modified zeolites was observed in the second phase when compared to unmodified natural zeolite. Modified natural zeolite addition to digesters can allow an increase in the potential biodegradability of piggery waste solid fraction and/or a considerable reduction of digestion volume. PMID:14640227

Miln, Z; Villa, P; Snchez, E; Montalvo, S; Borja, R; Ilangovan, K; Briones, R

2003-01-01

420

Improved thermal stability of an organic zeolite by fluorination  

Microsoft Academic Search

The thermal stability of an organic zeolite material, namely 2,4,6-tris(4-bromo-3,5-difluorphenoxy)-1,3,5-triazin (Br-3,5-DFPOT),\\u000a was improved by fluorination of 2,4,6-tris(4-bromophenoxy)-1,3,5-triazin (BrPOT). The open pore structure (van der Waals diameter\\u000a of 10.5) of the modified zeolite was observed up to 110C in comparison to 70C for BrPOT. Nitrogen sorption at low temperature\\u000a showed a type I isotherm and derived pore volumes thereof are in

Katharina Reichenbcher; Gatan Couderc; Antonia Neels; Karl Krmer; Edwin Weber; Jrg Hulliger

2008-01-01

421

Zeolite catalysis in the synthesis of isobutylene from hydrous ethanol  

NASA Astrophysics Data System (ADS)

This work deals with the synthesis of isobutylene from a hydrous ethanol feedstock over zeolites. The synthesis is accomplished in three steps: (1) low-temperature direct ethanol conversion to ethylene on H-ZSM-5 zeolite, (2) ethylene conversion to butene products over metal-exchanged zeolites, and (3) butene skeletal rearrangement to isobutylene over FER zeolites. The key to understanding and optimizing each synthesis step lies in the ability to control and regulate the zeolite acidity (Bronsted and Lewis)---both strength and number. Therefore, the continuous temperature programmed amine desorption (CTPAD) technique was further developed to simultaneously count the Bronsted acid sites and quantitatively characterize their strength. The adsorption of ethanol, reaction products, amines, coke and ethanol-derived residue (EDR) were monitored gravimetrically using the highly sensitive, novel Tapered Element Oscillating Microreactor (TEOM) apparatus. The TEOM was also used also in conjunction with CTPAD to characterize Bronsted acidity which is a new application for the instrument. For the first synthesis step, a parallel reaction exists which simultaneously produces diethyl ether and ethylene directly over H-ZSM-5. The reaction rates for each pathway were measured directly using a differential reactor operating at low temperatures (<473 K). Water in the ethanol feed enhances the rate of ethylene formation. A mechanism and kinetic expression are proposed for this reaction over H-ZSM-5, with diethyl-ether desorption and ethylene formation as the rate limiting steps. Heat of adsorption values measured from the independent microcalorimetry work reported in the literature are incorporated into the kinetic analysis which reduces the number of regressed parameters. For the remaining synthesis steps, several zeolite structures (ZSM-5, Y, FER) partially exchanged with Pd, Ti, Ni and Au were prepared and tested. It was determined from this screening study that the zeolites containing Pd are the most efficient catalysts for the dimerization reaction. Characterization results from x-ray diffraction (XRD), electron paramagnetic resonance (EPR) spectroscopy, and CTPAD suggest a stable, Pd species with a low oxidation state as part of the active site in Pd-exchanged zeolites. Isobutylene was present in the C4 fraction at reasonable quantities for most of the catalyst candidates, especially those containing an alkali metal co-cation.

Phillips, Cory Bernard

1999-11-01

422

Organization of zeolite microcrystals for production of functional materials.  

PubMed

This Account summarizes various methods of organizing zeolite microcrystals into two-dimensional functional entities such as monolayers, multilayers, and patterned monolayers on various substrates and three-dimensional functional entities such as microballs and protein-zeolite composite fibrils. In the case of monolayer assembly, various types of linkages and substrates, factors that govern the rate, degree of coverage, degree of close packing, degree of uniform orientation, and average binding strength between each crystal and the substrate are described. The current and future applications of the organized products are also discussed. PMID:17226943

Yoon, Kyung Byung

2007-01-01

423

Zeolites replacing plant fossils in the Denver formation, Lakewood, Colorado.  

USGS Publications Warehouse

Well-developed crystals of heulandite and stilbite, within fossil wood, occur in sedimentary rocks in Lakewood, Jefferson County. The rocks belong to the Denver formation, a locally fossiliferous deposit of fluvial claystone, siltstone, sandstone and conglomerate, containing some volcanic mudflows (andesitic) of late Cretaceous to Palaeocene age. Altered volcanic glass released Na and Ca into the ground-water and subsequently zeolites were crystallized in the open spaces between grains and within fossil plant structures. Minor pyrite, quartz (jasper), calcite and apatite also occur as replacements of fossil wood. Similar zeolite occurrences in other areas are reviewed.-R.S.M.

Modreski, P.J.; Verbeek, E.R.; Grout, M.A.

1984-01-01

424

Effect of crystal size on physical and catalytic properties of ZSM-5 type zeolites  

NASA Astrophysics Data System (ADS)

Diffusion of C6-alkanes in zeolite ZSM-5 and its aluminum free variant silicate-1 receives the greatest attention in the thesis. A physical property of zeolite like the ability to sorb, in particular, nonpolar compounds, was utilized in studying hydrocarbon diffusion by performing adsorption and desorption experiments. The diffusional behavior of the zeolite ZSM-5 and of aluminated silicate-1 at catalytically relevant temperatures was studied by way of a catalytic property of the zeolite. Descriptions of physical studies on nitrogen sorption in ZSM 5 type zeolites and of catalytic studies on the conversion of ethanol to hydrocarbons complete the thesis which tries to give a better understanding of adsorptive, diffusional, and catalytic behavior by describing experiments in which only one parameter has been varied, the zeolite crystal size. Discussions and conclusions are directed towards the industrial application of zeolite ZSM-5, as a catalyst.

Voogd, P.

1991-09-01

425

[Biodegradation and adsorption of bio-zeolite on pyridine and quinoline].  

PubMed

The study was to explore the treatment of pyridine, quinoline and their transformation product, NH(4+) -N, by the biodegradation and adsorption of a natural and a modified bio-zeolites. The experiment results demonstrated that the mixed bacteria on the bio-zeolites, a pyridine-degrading bacterium and a quinoline-degrading bacterium, could degrade pyridine and quinoline simultaneously. The NH(4+) -N transformed from pyridine and quinoline could be adsorbed by the natural and modified zeolites. The adsorption capacity of the modified zeolite was lower than that of the natural zeolite. However, more microorganisms could attach on the surface of the modified zeolite, so the application of the modified bio-zeolite has a better prospect in actual treatment of pyridine and/ or quinoline pollution. PMID:21072937

Bai, Yao-Hui; Sun, Qing-Hua; Xing, Rui; Wen, Dong-Hui; Tang, Xiao-Yan

2010-09-01

426

ATALANTE 2004 Nmes (France) June 21-25, 2004 1 Characterisation of Nd-doped calcium aluminosilicate parent glasses designed for the preparation of  

E-print Network

temperature around 760 °C was found for all the glasses (measured by differential thermal analysis), which of the glassy network. Due to the high preparation temperature of the glasses, a small quantity of Ti4+ ions aluminosilicate parent glasses designed for the preparation of zirconolite-based glass-ceramic waste forms P

Boyer, Edmond

427

Solubility and solution mechanisms of chlorine in aluminosilicate melts at high pressure and high temperature  

NASA Astrophysics Data System (ADS)

We address the effect of alkalies and aluminum on the solution behavior of Cl by combining solubility measurements of Cl and Raman data of Cl-bearing peralkaline aluminosilicate glasses (quenched melt). Six compositions along the join Na2Si3O7(NS3)-Na2(NaAl)3O7 and six compositions along the join K2Si3O7(KS3)-K2(KAl)3O7 were used. In order to isolate potential effects of Al/(Al+Si) from changes on melt polymerization, Al2O3 was exchanged with SiO2 in a charge-balanced form, NaAlO2 and KaAlO2 thus keeping approximately constant NBO/T (0.65 0.02) for all melts (assuming Al3+ in 4-fold coordination in the melts). Starting materials were doped with 5wt% Cl in the form of PdCl2, which releases Cl2 as its gaseous phase during experiment. Samples were synthetized on piston-cylinder apparatus at 1600C - 1.5 GPa. At the end of the experiments, Pd forms little spheres (1-2 ?m) that for most part dissolves into the capsule. Chlorine oversaturation in the melts is ensured by the observation of bubbles in the quenched samples. The Cl solubility in Na-bearing systems is about twice that of the than in K-bearing system and may, therefore, be negatively correlated with ionic radius of the metal cation.. The solubility also decreases with Al/(Al+Si). In NS3 system, it decreases from 4.01 0.13 wt% of Cl in Al-free systems to 1.87 0.19 wt% of Cl for an Al/Al+Si ratio of 0.34. In KS3 system, this decrease is from 2.23 0.08 wt% of Cl in Al-free systems to 0.62 0.05 wt% of Cl for an Al/Al+Si ratio of 0.36. In Al-free systems, preliminary Raman data show the appearance of a peak around 465cm-1, that we assigned to alkali-Cl bonding. The intensity of this 465cm-1 peak increases with Al content confirming the role of Al in Cl solution mechanism.We also identify the molecular Cl peak at 1540cm-1. The peak can be detected only in Al-bearing melts. The Al substitution for Si results in increased abundance of three-dimensional cages on the melt structure into which molecular Cl2 may be dissolved. This latter principle is similar to the solution behavior of other molecular and/or atomic species in melts.

Dalou, C.; Mysen, B. O.

2012-12-01

428

Computational studies of polyelectrolytes containing zeolite fragments.  

SciTech Connect

The structures and sodium affinities of a series of zeolitic fragments [H{sub 3}Al(OCH{sub 3}){sub x}(OSiH{sub 3}){sup -}{sub 1-x}, 2T, H{sub 2}Al(OCH{sub 3}){sub x}(OSiH{sub 3}){sup -}{sub 2-x}, 3T, Al(OCH3){sub x}(OSiH{sub 3}){sup -}{sub 4-x}, 5T] that mimic the charge sites in polyelectrolytes are calculated by ab initio molecular orbital methods at different levels of theory. At the HF/6-31G* level, the decrease in the sodium affinity due to the substitution of an OCH{sub 3} group by an OSiH{sub 3} group is about 8 kcal/mol in the 2T and 3T systems. In the 5T systems, the replacement of a sodium-coordinated OCH{sub 3} group by an OSiH{sub 3} group causes a decrease of 7 kcal/mol in the sodium affinity, while the substitution for a non-sodium-coordinated OCH{sub 3} group results in a 2.7 kcal/mol decrease. The lower sodium affinity indicates a weaker Coulombic interaction, suggesting an enhanced ionic conductivity with the substitution of carbon by silicon, consistent with experimental results. Natural bond orbital (NBO) analyses show that silicon-bonded oxygen atoms have smaller lone-pair dipole moments, resulting in a lower sodium affinity. The substitution of aluminum by boron leads to a higher sodium affinity, although the effect of replacing an OCH{sub 3} group by an OSiH{sub 3} group still reduces the sodium affinity. The effect of the sodium cation on the bond angles in these systems is also investigated.

Lee, Y.-C.; Curtiss, L. A.; Ratner, M. A.; Shriver, D. F.; Northwestern Univ.

1999-08-05

429

Computational studies of polyelectrolytes containing zeolitic fragments  

SciTech Connect

The structures and sodium affinities of a series of zeolitic fragments [H{sub 3}Al(OCH{sub 3}){sub x}(OSiH{sub 3}){sub 1{minus}x}{sup {minus}}, 2T, H{sub 2}Al(OCH{sub 3}){sub x}(OSiH{sub 3}){sub 2{minus}x}{sup {minus}}, Al(OCH{sub 3}){sub x}(OSiH{sub 3}){sub 4{minus}x}{sup {minus}}, 5T], that mimic the charge sites in polyelectrolytes are calculated by ab initio molecular orbital methods at different levels of theory. At the HF/6-31G{sup *} level, the decrease in the sodium affinity due to the substitution of an OCH{sub 3} group by an OSiH{sub 3} group is abo