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1

Amphiphilic organosilane-directed synthesis of crystalline zeolite with tunable mesoporosity  

Microsoft Academic Search

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

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

2006-01-01

2

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

3

Multipolar correlations between reactants in crystalline and semiamorphous zeolites  

SciTech Connect

The authors study the role of multipolar correlations in influencing the efficiency of reaction between a fixed target molecule and a diffusing coreactant in zeolites that exhibit both crystalline and semiamorphous structures. They focus on zeolite A and construct a geometrical model whose framework structure and attendant channel patterns have the same topology as the 26-hedral cavities of type I of this aluminosilicate. They consider reaction partners interacting via (attractiverepulsive) ion-ion, angle-averaged ion-dipole, and angle-averaged dipole-dipole potentials V(r), and by coupling the theory of finite Markov processes with a lattice version of the Debye-Smoluchowski theory of encounter-controlled reactions, they quantify the differences in the diffusion-controlled rate constant k/sub D/ for reactions taking place in crystalline regions of finite extent (rafts) versus those occurring in crystalline regions surrounded by an amorphous aluminosilicate structure. Calculations based on the model introduced in this paper suggest that much of the marked cation-exchange activity and catalytic activity of fully crystalline zeolites is already captured by semiamorphous zeolites containing raft structures having the spatial extent of those found in recent experimental work by Thomas and Bursill

Mandeville, J.B.; Golub, J.; Kozak, J.J.

1988-03-24

4

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

5

Pharmacokinetic Study of Zeolite A, Sodium Aluminosilicate, Magnesium Silicate, and Aluminum Hydroxide in Dogs  

Microsoft Academic Search

Zeolite A is a synthetic zeolite which may have therapeutic utility in osteoporotic individuals because of its ability to stimulate bone formation. A study of Zeolite A (30 mg\\/kg), sodium aluminosilicate (16 mg\\/kg), magnesium trisilicate (20 mg\\/kg), and aluminum hydroxide (675 mg) was designed in beagle dogs. The purpose of this study was to compare the oral bioavailability of silicon

Eugenio A. Cefali; Joseph C. Nolan; William R. McConnell; Denise Lowe Walters

1995-01-01

6

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

7

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

8

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

9

Zeolites.  

National Technical Information Service (NTIS)

Zeolites are naturally occurring aluminosilicate minerals. They have 3- dimensional framework structures of interconnected channels and cages that contain exchangeable alkali and alkaline earth cations and adsorbed water. Like phyllosilicates, zeolites ha...

D. W. Ming J. L. Boettinger

2001-01-01

10

Formic acid, ethanol in vycor glass, and water in aluminosilicate zeolites  

SciTech Connect

We present results of incoherent inelastic neutron-scattering experiments on formic acid, ethanol in vycor glass, and water in aluminosilicate zeolites performed at Argonne`s spallation neutron source, IPNS. The forming and breaking of hydrogen bonds are discussed in terms of translational and rotational diffusion, and vibrational footprints of various molecular species in these systems.

Loong, C.K.; Trouw, F.; Iton, L.E.

1993-11-01

11

Pharmacokinetic study of zeolite A, sodium aluminosilicate, magnesium silicate, and aluminum hydroxide in dogs.  

PubMed

Zeolite A is a synthetic zeolite which may have therapeutic utility in osteoporotic individuals because of its ability to stimulate bone formation. A study of Zeolite A (30 mg/kg), sodium aluminosilicate (16 mg/kg), magnesium trisilicate (20 mg/kg), and aluminum hydroxide (675 mg) was designed in beagle dogs. The purpose of this study was to compare the oral bioavailability of silicon and aluminum from Zeolite A, sodium aluminosilicate, magnesium trisilicate, and aluminum hydroxide in dogs. Twelve female dogs received each compound as a single dose separated by one week in a randomized, 4-way, crossover design. Plasma samples were drawn at time 0 and for 24 hours after dosing. The concentrations of silicon and aluminum were determined by graphite furnace atomic absorption. The mean plasma silicon AUC values (+/- S.D.) were 9.5 +/- 4.5, 7.7 +/- 1.6, 8.8 +/- 3.0, 6.1 +/- 1.9 mg.hr/L and the mean plasma silicon Cmax values (+/- S.D.) were 1.07 +/- 1.06, 0.67 +/- 0.27, 0.75 +/- 0.31, 0.44 +/- 0.17 mg/L for Zeolite A, sodium aluminosilicate, magnesium trisilicate, and aluminum hydroxide respectively. Although mean silicon AUC and Cmax values were elevated when compared to baseline after administration of the silicon containing compounds, only the AUC from Zeolite A reached statistical significance (p = 0.041). The mean plasma silicon Tmax values (+/- S.D.) were 7.9 +/- 6.4, 5.8 +/- 4.6, 6.9 +/- 6.3 and 8.5 +/- 3.4 hrs for Zeolite A, sodium aluminosilicate, magnesium trisilicate and aluminum Hydroxide respectively.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7784344

Cefali, E A; Nolan, J C; McConnell, W R; Walters, D L

1995-02-01

12

Facile synthesis of mesoporous aluminosilicates constructed with crystalline microporous frameworks  

NASA Astrophysics Data System (ADS)

A hierarchically micro-mesoporous structured ZSM-5 zeolite has been synthesized from assembly of aluminosilcate species with a tetra-quaternary ammonium type surfactant, in which the surfactant acts as two-level structure-directing templates for generating micropores and mesopores simultaneously. The synthesized samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, N2 adsorption-desorption isotherms, scanning electron microscopy, transmission electron microscopy, 27Al magic angle spinning nuclear magnetic resonance, X-ray photoelectron spectroscopy, Thermogravimetric analysis and Quantum chemical calculation. X-ray diffraction as well as nitrogen sorption analyses indicated the dual-porosity of samples, one is from intra-crystalline micropores, and the other is from mesopores. Quantum chemical calculation results showed that the inner ammonium groups of surfactant had more higher molecular degrees of freedom for the zeolite-structure-directing function. Moreover, on the basis of the same concept, this method could be extended to investigate other hierarchically structured zeolites.

Liu, Baoyu; Ren, Yanqun; Duan, Qianqian; Chen, Fei; Xi, Hongxia; Qian, Yu

2013-08-01

13

Synthesis of aluminosilicate and gallosilicate zeolites via a charge density mismatch approach and their characterization.  

PubMed

Aluminosilicate and gallosilicate zeolite syntheses via a charge density mismatch (CDM) approach are compared at intermediate-silica compositions (Si/Me = 5-16, where Me is Al or Ga). With a variation of the crystallization temperature and of the type and/or concentration of alkali metal ions added as a crystallization structure-directing agent (SDA) to tetraethylammonium-tetramethylammonium, tetraethylammonium-hexamethonium, and strontium-choline mixed-SDA systems, we were able to obtain 11 different zeolite structures. However, only 5 out of a total 40 pairs of aluminosilicate and gallosilicate synthesis runs at otherwise identical chemical compositions were found to give the same zeolite product with no detectable impurities, suggesting that the structure-directing ability of Ga is quite different from that of Al even in intermediate-silica synthesis conditions. The CDM approach to offretite synthesis led to hexagonal plate-like crystals with aspect ratios lower than 0.3, and UZM-22 exhibited no significant preference of Al substitution for particular tetrahedral sites, especially for site T1, unlike its framework type material ZSM-18. More interestingly, the EU-1 zeolite obtained from an aluminosilicate synthesis mixture containing Li(+) as an inorganic crystallization SDA in the tetraethylammonium-hexamethonium double-organic additive system has been characterized to locate about half of its Li(+) ions in the framework, while the Li distribution over the 10 topologically different tetrahedral sites is nonrandom in nature. PMID:21247158

Park, Min Bum; Cho, Sung June; Hong, Suk Bong

2011-02-16

14

Hydrothermally stable mesoporous aluminosilicates (MSU-S) assembled from zeolite seeds as catalysts for biomass pyrolysis  

Microsoft Academic Search

The in situ upgrading of biomass pyrolysis vapors with two mesoporous aluminosilicate materials (MSU-SBEA) assembled from zeolite Beta (BEA) seeds was tested in the present study, in comparison to conventional Al-MCM-41 and to non-catalytic biomass pyrolysis. The first sample (MSU-S\\/HBEA) exhibited an hexagonal mesopore structure while the second one (MSU-S\\/WBEA) possessed a wormhole-like mesopore structure with high textural porosity. The

Kostas S. Triantafyllidis; Eleni F. Iliopoulou; Eleni V. Antonakou; Angelos A. Lappas; Hui Wang; Thomas J. Pinnavaia

2007-01-01

15

?SR study on ferromagnetism of potassium clusters in aluminosilicate zeolite LTA  

Microsoft Academic Search

Potassium clusters stabilized in regular cages of aluminosilicate zeolite LTA are known to show ferromagnetic properties depending on the loading density of guest K atoms. In the present paper, a muon spin rotation\\/relaxation (?SR) experiment is reported for a sample at a K-loading density of 4.8 atoms per cage. This sample shows ferromagnetic properties below 6.5K. An increase in the

T. Nakano; D. Kiniwa; F. L. Pratt; I. Watanabe; Y. Ikemoto; Y. Nozue

2003-01-01

16

Analysis of the biological and chemical reactivity of zeolite-based aluminosilicate fibers and particulates.  

PubMed Central

Environmental and/or occupational exposure to minerals, metals, and fibers can cause lung diseases 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. Toward that goal, we have tested aluminosilicate zeolites to establish biological and chemical structure-function correlations. Zeolites have known crystal structure, are subject to experimental manipulation, and can be synthesized and controlled to produce particles of selected size and shape. Naturally occurring zeolites include forms whose biological activity is reported to range from highly pathogenic (erionite) to essentially benign (mordenite). Thus, we used naturally occurring erionite and mordenite as well as an extensively studied synthetic zeolite based on faujasite (zeolite Y). Bioactivity was evaluated using lung macrophages of rat origin (cell line NR8383). Our objective was to quantitatively determine the biological response upon interaction of the test particulates/fibers with lung macrophages and to evaluate the efficacy of surface iron on the zeolites to promote the Fenton reaction. The biological assessment included measurement of the reactive oxygen species by flow cytometry and chemiluminescence techniques upon phagocytosis of the minerals. The chemical assessment included measuring the hydroxyl radicals generated from hydrogen peroxide by iron bound to the zeolite particles and fibers (Fenton reaction). Chromatography as well as absorption spectroscopy were used to quantitate the hydroxyl radicals. We found that upon exposure to the same mass of a specific type of particulate, the oxidative burst increased with decreasing particle size, but remained relatively independent of zeolite composition. On the other hand, the Fenton reaction depended on the type of zeolite, suggesting that the surface structure of the zeolite plays an important role.

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

2002-01-01

17

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

PubMed

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

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

2014-02-12

18

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

19

Characterization of zeolite L nanoclusters  

Microsoft Academic Search

Zeolite L (structure code LTL) crystals are synthesized starting from homogeneous potassium aluminosilicate solutions. Particle size and shape of the formed zeolite L are examined by high-resolution transmission electron microscopy, field emission-scanning electron microscopy, X-ray diffraction, and dynamic light scattering. The synthesis conditions reported lead to nanoclusters of aligned zeolite crystalline domains of dimensions â¼40 nm in the channel direction

Michael Tsapatsis; Mark Lovallo; Masayoshi Sadakata; Mark E. Davis

1995-01-01

20

Influence of silica and alumina source materials on the physicochemical characteristics of crystalline zeolite beta  

Microsoft Academic Search

The influence of different silica sources such as silica sol and fumed silica on the physochemcial characteristics of well crystalline zeolite beta was studied as a function of variation in alumina sources viz. sodium aluminate and aluminium isopropoxide. Furthermore, the effect of templating organocation source on the crystallization kinetics and characteristics of fully crystalline beta zeolite was also investigated. The

M. W. Kasture; P. S. Niphadkar; S. R. Kate; P. D. Godbole; K. R. Patil; G. M. Chaphekar; P. N. Joshi

2004-01-01

21

Formulation and method for improved ion exchange in zeolites and related aluminosilicates using polymer solutions  

US Patent & Trademark Office Database

Among other things, this disclosure provides a method for exchanging cations in an aluminosilicate. The method includes combining, in an exchange solvent and under ion exchange conditions, an ion-exchangeable aluminosilicate having a first cation associated therewith as a counter ion and a second cation source, to provide a mixture that includes the ion-exchanged aluminosilicate which includes the second cation associated therewith as a counter ion. Suitable exchange solvents include polyalkylene oxide glycols, polyalkylene oxide glycol monoethers, polyalkylene oxide glycol diethers, or any combination thereof.

2012-07-17

22

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

PubMed

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. PMID:24957696

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

2014-01-01

23

Separation of Closely Related Systems by Molecular Sieve Zeolites  

Microsoft Academic Search

Molecular sieve zeolites are robust, thermally stable selective absorbents. They are chemically pure crystalline aluminosilicates with up to 50% of their crystal volume available for adsorption. Zeolites are widely used for industrial drying, purification, and separation, as well as catalysts and ion exchangers. They can be synthesized, on a plant scale, from silica (or sodium silicate) and sodium aluminate. The

A. Dyer

1978-01-01

24

Characterization of Aluminosilicate Formation on the Surface of a Crystalline Silicotitanate Ion Exchanger  

SciTech Connect

Millions of gallons of high-level radioactive waste are contained in underground tanks at U.S. Department of Energy sites such as Hanford and Savannah River. Most of the radioactivity is due to 137Cs and 90Sr, which must be extracted in order to concentrate the waste. An ion exchanger, crystalline silicotitanate IONSIV IE911, is being considered for separation for Cs at the Savannah River Site (SRS). While the performance of this ion exchanger has been well characterized under normal operating conditions, Cs removal at slightly elevated temperatures, such as those that may occur in a process upset, is not clear. Our recent study indicates that during exposure to SRS simulant at 55 degrees Celsius and 80 degrees Celsius, an aluminosilicate coating formed on the exchanger surface. There was concern that the coating would affect its ion exchange properties. A LEO 982 field emission scanning electron microscope (FESEM) and an Oxford ISIS energy dispersive x-ray spectrometer (EDS) were used to characterize the coating.

Young, James S.; Su, Yali; Li, Liyu; Balmer, M Lou; G W Bailey

2001-10-30

25

Quantifying defects in zeolites and zeolite membranes  

NASA Astrophysics Data System (ADS)

Zeolites are crystalline aluminosilicates that are frequently used as catalysts to transform chemical feedstocks into more useful materials in a size- or shape-selective fashion; they are one of the earliest forms of nanotechnology. Zeolites can also be used, especially in the form of zeolite membranes (layers of zeolite on a support), to separate mixtures based on the size of the molecules. Recent advances have also created the possibility of using zeolites as alkaline catalysts, in addition to their traditional applications as acid catalysts and catalytic supports. Transport and catalysis in zeolites are greatly affected by physical and chemical defects. Such defects can be undesirable (in the case of zeolite membranes), or desirable (in the case of nitrogen-doped alkaline zeolites). Studying zeolites at the relevant length scales requires indirect experimental methods such as vapor adsorption or atomic-scale modeling such as electronic structure calculations. This dissertation explores both experimental and theoretical characterization of zeolites and zeolite membranes. Physical defects, important in membrane permeation, are studied using physical adsorption experiments and models of membrane transport. The results indicate that zeolite membranes can be modeled as a zeolite powder on top of a support---a "supported powder," so to speak---for the purposes of adsorption. Mesoporosity that might be expected based on permeation and confocal microscopy measurements is not observed. Chemical defects---substitutions of nitrogen for oxygen---are studied using quantum mechanical models that predict spectroscopic properties. These models provide a method for simulating the 29Si NMR spectra of nitrogendefected zeolites. They also demonstrate that nitrogen substitutes into the zeolite framework (not just on the surface) under the proper reaction conditions. The results of these studies will be valuable to experimentalists and theorists alike in our efforts to understand the versatile and complicated materials that are zeolites.

Hammond, Karl Daniel

26

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

27

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

28

Hydrocarbon cracking with yttrium exchanged zeolite y catalyst  

Microsoft Academic Search

A process is described for cracking a gas oil boiling range hydrocarbon feedstock comprising the step of contacting the feedstock in a catalytic cracking zone under catalytic cracking conditions to produce convulsion products comprising gasoline with a catalyst composition. The process comprises: a Y crystalline aluminosilicate zeolite, having the structure of faujasite and having uniform pore diameters and a silica

C. F. Lochow; D. B. Kovacs

1987-01-01

29

SSZ-52, a zeolite with an 18-layer aluminosilicate framework structure related to that of the DeNOx catalyst Cu-SSZ-13.  

PubMed

A new zeolite (SSZ-52, |(C14H28N)6Na6(H2O)18|[Al12Si96O216]), related to the DeNOx catalyst Cu-SSZ-13 (CHA framework type), has been synthesized using an unusual polycyclic quaternary ammonium cation as the structure-directing agent. By combining X-ray powder diffraction (XPD), high-resolution transmission electron microscopy (HRTEM) and molecular modeling techniques, its porous aluminosilicate framework structure (R3m, a = 13.6373(1) Å, c = 44.7311(4) Å), which can be viewed as an 18-layer stacking sequence of hexagonally arranged (Si,Al)6O6 rings (6-rings), has been elucidated. The structure has a three-dimensional 8-ring channel system and is a member of the ABC-6 family of zeolites (those that can be described in terms of 6-ring stacking sequences) like SSZ-13, but it has cavities that are twice as large. The code SFW has been assigned to this new framework type. The large cavities contain pairs of the bulky organic cations. HRTEM and XPD simulations show that stacking faults do occur, but only at the 5-10% level. SSZ-52 has considerable potential as a catalyst in the areas of gas conversion and sequestration. PMID:23782259

Xie, Dan; McCusker, Lynne B; Baerlocher, Christian; Zones, Stacey I; Wan, Wei; Zou, Xiaodong

2013-07-17

30

Zeolite A imidazolate frameworks  

Microsoft Academic Search

Faujasite (FAU) and zeolite A (LTA) are technologically important porous zeolites (aluminosilicates) because of their extensive use in petroleum cracking and water softening. Introducing organic units and transition metals into the backbone of these types of zeolite allows us to expand their pore structures, enhance their functionality and access new applications. The invention of metal-organic frameworks and zeolitic imidazolate frameworks

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

2007-01-01

31

Dehydration of n-butanol on zeolite H-ZSM-5 and amorphous aluminosilicate: Detailed mechanistic study and the effect of pore confinement  

SciTech Connect

This study of the catalytic dehydration of n-butanol on zeolite H-ZSM-5 and amorphous aluminosilicate confirms the reaction scheme proposed earlier by the authors for isobutanol dehydration. The rate constant for n-butanol dehydration on H-ZSM-5 (determined from in situ FTIR kinetic studies by monitoring the growth of the water deformation peak at 1640 cm{sup -1}) is shown to be the true dehydration rate constant (1.7 x 10{sup -4}s{sup -1} at 100{degrees}C). On the other hand, the rate constants determined from GC steady-state kinetic studies (temperature interval 105-185{degrees}C) are effective ones, giving activation energies of 22{+-}2 kcal/mol and 33{+-}2 kcal/mol for complete dehydration and dehydration to butene only, respectively. By studying the dehydration reaction under different conditions (flow and static reactors, steady-state and non-steady-state regimes) and on samples with rather similar acid strengths but different porous systems (H-ZSM-5-microporous channels with diameter {approximately}5.5 {angstrom}, and amorphous aluminosilicate-pores of average diameter {approximately}50 {angstrom}), it was shown that depending on the concentration of butanol in the immediate vicinity of the active alkoxide intermediate {exists}-OC{sub 4}H{sub 9}, different reaction paths are utilized. High concentrations of alcohol favor ether formation, whereas low ones favour butene. This also explains the so-called {open_quotes}stop effect{close_quotes} observed in GC experiments, where an increase in the rate of butene formation occurs when the flow of alcohol is stopped and replaced with a flow of pure helium. Here, decreasing the concentration of alcohol in the micropores results in more of the alkoxide intermediate transforming to butene rather than to ether (which was the case at steady state). 28 refs., 17 figs., 3 tabs.

Makarova, M.A.; Paukshtis, E.A.; Zamaraev, K.I. [Boreskov Institute of Catalysis, Novosibirsk (Russian Federation)] [and others] [Boreskov Institute of Catalysis, Novosibirsk (Russian Federation); and others

1994-09-01

32

Microwave-hydrothermal synthesis of Al-substituted tobermorite from zeolites  

Microsoft Academic Search

Here, we report the rapid synthesis of Al-substituted tobermorites from zeolites under microwave-hydrothermal (M-H) conditions. The synthesized phases were characterized by powdered XRD analysis, SEM and selective Cs exchange determination. Zeolites served as aluminosilicate sources and M-H conditions yielded highly crystalline Al-substituted tobermorites in 2h at 180°C and they showed high selectivity for Cs. For example, an Al-substituted tobermorite synthesized

Sridhar Komarneni; Jayanth S Komarneni; Bharat Newalkar; Stephen Stout

2002-01-01

33

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

34

The initial step of silicate versus aluminosilicate formation in zeolite synthesis: a reaction mechanism in water with a tetrapropylammonium template.  

PubMed

The initial step for silicate and aluminosilicate condensation is studied in water in the presence of a realistic tetrapropylammonium template under basic conditions. The model corresponds to the synthesis conditions of ZSM5. The free energy profile for the dimer formation ((OH)(3)Si-O-Si-(OH)(2)O(-) or [(OH)(3)Al-O-Si-(OH)(3)](-)) is calculated with ab initio molecular dynamics and thermodynamic integration. The Si-O-Si dimer formation occurs in a two-step manner with an overall free energy barrier of 75 kJ mol(-1). The first step is associated with the Si-O bond formation and results in an intermediate with a five-coordinated Si, and the second one concerns the removal of the water molecule. The template is displaced away from the Si centres upon dimer formation, and a shell of water molecules is inserted between the silicate and the template. The main effect of the template is to slow down the backward hydrolysis reaction with respect to the condensation one. The Al-O-Si dimer formation first requires the formation of a metastable precursor state by proton transfer from Si(OH)(4) to Al(OH)(4)(-) mediated by a solvent molecule. It then proceeds through a single step with an overall barrier of 70 kJ mol(-1). The model with water molecules explicitly included is then compared to a simple calculation using an implicit continuum model for the solvent. The results underline the importance of an explicit and dynamical treatment of the water solvent, which plays a key role in assisting the reaction. PMID:22297854

Trinh, Thuat T; Rozanska, Xavier; Delbecq, Françoise; Sautet, Philippe

2012-03-14

35

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

Microsoft Academic Search

Single phase chamfered-edge zeolite 4A samples in pure form with a high crystallinity were synthesized by applying step-change of synthesis temperature during hydrothermal treatment of coal fly ash. The calcium binding capacity of these zeolite 4A samples (prepared from coal fly ash) and the commercial detergent grade zeolite 4A were tested for usage as a detergent builder. The results show

K. S. Hui; C. Y. H. Chao

2006-01-01

36

Natrolite: A zeolite with negative Poisson's ratios  

NASA Astrophysics Data System (ADS)

The recently published experimental elastic constants [C. Sanchez-Valle, S. V. Sinogeikin, Z. A. Lethbridge, R. I. Walton, C. W. Smith, K. E. Evans, and J. D. Bass, J. Appl. Phys. 98, 053508 (2005)] for single crystals of the orthorhombic aluminosilicate zeolite NAT (natrolite, Na2(Al2Si3O10)2H2O, Fdd2) throw valuable light on the potential of NAT as a material which exhibits single crystalline negative Poisson's ratios (auxetic). On performing an off-axis analysis of these elastic constants we confirm that the zeolite natrolite exhibits auxetic behavior in the (001) plane. This supports our preliminary report that NAT-type zeolites exhibit auxetic behavior through a mechanism involving microscopic rotation of semi-rigid structural units.

Grima, Joseph N.; Gatt, Ruben; Zammit, Victor; Williams, Jennifer J.; Evans, Kenneth E.; Alderson, Andrew; Walton, Richard I.

2007-04-01

37

Role of composition and oxygen partial pressure on microstructural and crystalline phase evolution in aluminosilicate derived aggregates  

NASA Astrophysics Data System (ADS)

Spherical aggregates, approximately 1mm in diameter, derived from either kaolinite or bauxite are used in tonnage quantities to aid the extraction of oil and natural gas. Aggregates intended for this application are referred to as proppants and key characteristics include low density and high strength, which are influenced by processing temperature and variation in raw ore chemistry. Kaolinite and bauxite ores doped with varying concentrations of K2O and Fe2O3 were sintered at different temperatures to elucidate composition-processing-property relationships. The dopants are known to form low temperature ternary eutectics with Al2O3 and SiO2 and are anticipated to facilitate low temperature densification and enhance mullite formation. In addition, proppants doped with Fe2 O3 were studied under varying oxygen partial pressures to further enhance low temperature densification by manipulating the valence state of iron. Microstructure and crystalline phase assemblage were evaluated by scanning electron microscopy and X-ray diffraction, respectively, and correlated with results of density and strength measurements obtained by gas pycnometry and diametral compression, respectively. Results indicate that dopant enhanced densification can simultaneously improve strength and processing economy of proppants by lowering sintering temperatures up to 100°C. Controlled atmosphere studies revealed that manipulating the valence of iron produces unique microstructures that may be useful in a number of different applications. These microstructures include aggregates with metallic coatings and aggregates with core-shell microstructures, which exhibit a porous core enclosed by a relatively dense outer shell.

Luscher, Walter G.

38

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

39

MAS NMR and FTIR spectra of framework aluminosilicates  

NASA Astrophysics Data System (ADS)

In the work, the results of 27Al MAS NMR studies carried out for structures of different framework aluminosilicates are presented. The spectra of natural clinoptilolite and its sodium and hydrogen forms were measured. The zeolite spectra were obtained before and after incorporation of heavy metal cations (Pb 2+, Cd 2+, Ni 2+ and Cr 3+) into the zeolite structure. After decomposition of the spectra into component peaks differences caused by ion exchange were observed. Additionally, NMR spectra of kalsilite (framework aluminosilicate, not belonging to zeolite group) and other zeolites (chabazite, heulandite and analcime) were measured. 27Al MAS NMR spectra of all the samples studied were compared with the FTIR spectra measured in the middle infrared region. Based on the results obtained it has been proved that the interpretation of spectra obtained using these two different techniques can give some information concerning changes occurring in various framework aluminosilicate structures.

Mozgawa, W.; Fojud, Z.; Handke, M.; Jurga, S.

2002-09-01

40

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

PubMed

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

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

2014-06-17

41

Zeolite matrices for pigments  

Microsoft Academic Search

Intracrystalline voids in zeolites and other crystalline molecular sieves are suitable for accommodation and stabilization of certain chromophors. Our method of ultramarine synthesis comprises a generation of the anion radicals S3? from precursors (sodium polysulfides) introduced into zeolites. The color of the resulting ultramarine was modified by introduction of various cations into the parent zeolites. Using of polysulfides combined with

S. Kowalak; M. Wróbel; N. Gol?ebniak; A. Jankowska; B. Turkot

1999-01-01

42

Zeolite membranes from kaolin  

SciTech Connect

Zeolite films are sought as components of molecular sieve membranes. Different routes used to prepare zeolite composite membranes include growing zeolite layers from gels on porous supports, depositing oriented zeolites on supports, and dispersing zeolites in polymeric membranes. In most cases, it is very difficult to control and avoid the formation of cracks and/or pinholes. The approach to membrane synthesis is based on hydrothermally converting films of layered aluminosilicates into zeolite films. The authors have demonstrated this concept by preparing zeolite A membranes on alumina supports from kaolin films. The authors have optimized the process parameters not only for desired bulk properties, but also for preparing thin (ca. 5 {micro}m), continuous zeolite A films. Scanning electron microscopy shows highly intergrown zeolite A crystals over most of the surface area of the membrane, but gas permeation experiments indicate existence of mesoporous defects and/or intercrystalline gaps. It has been demonstrated that the thickness of the final zeolite A membrane can be controlled by limiting the amount of precursor kaolin present in the membrane.

Karle, B.G. [Univ. of New Mexico, Albuquerque, NM (United States). Center for Micro-Engineered Ceramics; Brinker, C.J. [Univ. of New Mexico, Albuquerque, NM (United States). Center for Micro-Engineered Ceramics]|[Sandia National Labs., Albuquerque, NM (United States); Phillips, M.L.F. [Sandia National Labs., Albuquerque, NM (United States)

1996-07-01

43

MAS NMR and FTIR spectra of framework aluminosilicates  

Microsoft Academic Search

In the work, the results of 27Al MAS NMR studies carried out for structures of different framework aluminosilicates are presented. The spectra of natural clinoptilolite and its sodium and hydrogen forms were measured. The zeolite spectra were obtained before and after incorporation of heavy metal cations (Pb2+, Cd2+, Ni2+ and Cr3+) into the zeolite structure. After decomposition of the spectra

W. Mozgawa; Z Fojud; M Handke; S Jurga

2002-01-01

44

Oxygen and hydrogen isotope geochemistry of zeolites  

Microsoft Academic Search

Zeolites are widespread minerals and occur in a large variety of rock types. More than 40 naturally occurring species have been described. Zeolites are hydrous aluminosilicates which possess unique properties such as reversible dehydration, selective sorption, molecular sieving, ion exchange, and catalysis. While we known a great deal about their occurrence, chemistry, crystal structure, and physical properties, we know relatively

H. R. Karlsson; R. N. Clayton

1990-01-01

45

Nanoscale encapsulation: the structure of cations in hydrophobic microporous aluminosilicates  

SciTech Connect

Hydrophobic microporous aluminosilicates, created by organic surface modification of inherently hydrophilic materials such as zeolites and clays, are currently being investigated as storage media for hazardous cations. Use of organic monolayers to modify the surface of an aluminosilicate after introducing an ion into the zeolite/clay reduces the interaction of water with the material. Resulting systems are about 20 times more resistant to leaching of stored ion. XAS spectra from the encapsulated ion demonstrate that byproducts from the organic modifier can complex with the stored cation. This complexation can result in a decreased affinity of the cation for the aluminosilicate matrix. Changing the organic modifier eliminates this problem. XAS spectra also indicate that the reactivity and speciation of the encapsulated ion may change upon application of the hydrophobic layer.

Wasserman, S.R.; Yuchs, S.E.; Giaquinta, D.; Soderholm, L.; Song, Kang

1996-10-01

46

Calibration analysis of zeolites by laser induced breakdown spectroscopy  

NASA Astrophysics Data System (ADS)

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

Hor?á?ková, M.; Grolmusová, Z.; Hor?á?ek, M.; Rakovský, J.; Hudec, P.; Veis, P.

2012-08-01

47

Tailored crystalline microporous materials by post-synthesis modification.  

PubMed

Crystalline microporous solids are an important class of inorganic materials with uses in different areas impacting our everyday lives, namely as catalysts, adsorbents, and ion exchangers. Advancements in synthesis have been invaluable in expanding the classical aluminosilicate zeolites to new unique framework types and compositions, motivating innovative developments. However, the inexhaustible post-synthetic options to tailor zeolite properties have been and will continue to be indispensable to realize emerging and to improve conventional applications. Starting from the routine drying and template removal processes that every zeolite must experience prior to use, a wide spectrum of treatments exists to alter individual or collective characteristics of these materials for optimal performance. This review documents the toolbox of post-synthetic strategies available to tune the properties of zeolitic materials for specific functions. The categorisation is based on the scale at which the alteration is aimed at, including the atomic structure (e.g. the introduction, dislodgment, or replacement of framework atoms), the micropore level (e.g. template removal and functionalisation by inorganic and organic species), and the crystal and particle levels (e.g. the introduction of auxiliary porosity). Through examples in the recent literature, it is shown that the combination of post-synthetic methods enables rational zeolite design, extending the characteristics of these materials way beyond those imposed by the synthesis conditions. PMID:22996351

Valtchev, Valentin; Majano, Gerardo; Mintova, Svetlana; Pérez-Ramírez, Javier

2013-01-01

48

Experimental charge density matching approach to zeolite synthesis  

Microsoft Academic Search

An Experimental Charge Density Matching (ECDM) approach to zeolite synthesis is described. The method features the initial formation of a Charge Density Mismatch (CDM) aluminosilicate reaction mixture characterized by the mismatch between the charge density on the organoammonium structure directing agent (SDA) and the charge density on the potential aluminosilicate network that is expected to form. This amounts to creating

G. J. Lewis; M. A. Miller; J. G. Moscoso; B. A. Wilson; L. M. Knight; S. T. Wilson

2004-01-01

49

Zeolite A imidazolate frameworks  

NASA Astrophysics Data System (ADS)

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

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

2007-07-01

50

Core-shell strain structure of zeolite microcrystals.  

PubMed

Zeolites are crystalline aluminosilicate minerals featuring a network of 0.3-1.5-nm-wide pores, used in industry as catalysts for hydrocarbon interconversion, ion exchangers, molecular sieves and adsorbents. For improved applications, it is highly useful to study the distribution of internal local strains because they sensitively affect the rates of adsorption and diffusion of guest molecules within zeolites. Here, we report the observation of an unusual triangular deformation field distribution in ZSM-5 zeolites by coherent X-ray diffraction imaging, showing the presence of a strain within the crystal arising from the heterogeneous core-shell structure, which is supported by finite element model calculation and confirmed by fluorescence measurement. The shell is composed of H-ZSM-5 with intrinsic negative thermal expansion whereas the core exhibits a different thermal expansion behaviour due to the presence of organic template residues, which usually remain when the starting materials are insufficiently calcined. Engineering such strain effects could have a major impact on the design of future catalysts. PMID:23832126

Cha, Wonsuk; Jeong, Nak Cheon; Song, Sanghoon; Park, Hyun-jun; Thanh Pham, Tung Cao; Harder, Ross; Lim, Bobae; Xiong, Gang; Ahn, Docheon; McNulty, Ian; Kim, Jungho; Yoon, Kyung Byung; Robinson, Ian K; Kim, Hyunjung

2013-08-01

51

Investigation on the effect of zeolite precursor on the formation process of MCM-41 containing zeolite Y building units  

NASA Astrophysics Data System (ADS)

The formation process of MCM-41 containing zeolite Y building units has been investigated by UV Raman spectroscopy, 29Si and 27Al MAS NMR spectroscopy, X-ray diffraction (XRD), N2 adsorption and electron microscopy (SEM and TEM). It is found that the precursor containing zeolite Y secondary building units promotes the formation of a metastable mesopore structure just after mixing the zeolite precursors with CTAB. In contrast, the low-polymerized aluminosilicates and well-crystallized zeolite crystals cannot be assembled with CTAB at this stage. The result supports that the zeolite secondary building units should promote to the formation of the mesopore wall. This has been ascribed to its high anionic charge density as well as the appropriate multidentate coordination. Lowering down the pH value to 9.3 facilitates the further polymerization of the aluminosilicate species to build up a stable mesoporous phase.

Li, Peng; Xiong, Guang; Liu, Liping; Wang, Longlong

2013-04-01

52

Investigation on the effect of zeolite precursor on the formation process of MCM-41 containing zeolite Y building units.  

PubMed

The formation process of MCM-41 containing zeolite Y building units has been investigated by UV Raman spectroscopy, (29)Si and (27)Al MAS NMR spectroscopy, X-ray diffraction (XRD), N2 adsorption and electron microscopy (SEM and TEM). It is found that the precursor containing zeolite Y secondary building units promotes the formation of a metastable mesopore structure just after mixing the zeolite precursors with CTAB. In contrast, the low-polymerized aluminosilicates and well-crystallized zeolite crystals cannot be assembled with CTAB at this stage. The result supports that the zeolite secondary building units should promote to the formation of the mesopore wall. This has been ascribed to its high anionic charge density as well as the appropriate multidentate coordination. Lowering down the pH value to 9.3 facilitates the further polymerization of the aluminosilicate species to build up a stable mesoporous phase. PMID:23434547

Li, Peng; Xiong, Guang; Liu, Liping; Wang, Longlong

2013-04-15

53

Synthesis, structure, and carbon dioxide capture properties of zeolitic imidazolate frameworks.  

PubMed

Zeolites are one of humanity's most important synthetic products. These aluminosilicate-based materials represent a large segment of the global economy. Indeed, the value of zeolites used in petroleum refining as catalysts and in detergents as water softeners is estimated at $350 billion per year. A major current goal in zeolite chemistry is to create a structure in which metal ions and functionalizable organic units make up an integral part of the framework. Such a structure, by virtue of the flexibility with which metal ions and organic moieties can be varied, is viewed as a key to further improving zeolite properties and accessing new applications. Recently, it was recognized that the Si-O-Si preferred angle in zeolites (145 degrees ) is coincident with that of the bridging angle in the M-Im-M fragment (where M is Zn or Co and Im is imidazolate), and therefore it should be possible to make new zeolitic imidazolate frameworks (ZIFs) with topologies based on those of tetrahedral zeolites. This idea was successful and proved to be quite fruitful; within the last 5 years over 90 new ZIF structures have been reported. The recent application of high-throughput synthesis and characterization of ZIFs has expanded this structure space significantly: it is now possible to make ZIFs with topologies previously unknown in zeolites, in addition to mimicking known structures. In this Account, we describe the general preparation of crystalline ZIFs, discussing the methods that have been developed to create and analyze the variety of materials afforded. We include a comprehensive list of all known ZIFs, including structure, topology, and pore metrics. We also examine how complexity might be introduced into new structures, highlighting how link-link interactions might be exploited to effect particular cage sizes, create polarity variations between pores, or adjust framework robustness, for example. The chemical and thermal stability of ZIFs permit many applications, such as the capture of CO(2) and its selective separation from industrially relevant gas mixtures. Currently, ZIFs are the best porous materials for the selective capture of CO(2); furthermore, they show exceptionally high capacity for CO(2) among adsorbents operating by physisorption. The stability of ZIFs has also enabled organic transformations to be carried out on the crystals, yielding covalently functionalized isoreticular structures wherein the topology, crystallinity, and porosity of the ZIF structure are maintained throughout the reaction process. These reactions, being carried out on macroscopic crystals that behave as single molecules, have enabled the realization of the chemist's dream of using "crystals as molecules", opening the way for the application of the extensive library of organic reactions to the functionalization of useful extended porous structures. PMID:19877580

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

2010-01-19

54

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

55

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

56

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

57

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

58

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

59

PHYSICAL, CHEMICAL AND STRUCTURAL EVOLUTION OF ZEOLITE-CONTAINING WASTE FORMS PRODUCED FROM METAKAOLINITE AND CALCINED HLW  

SciTech Connect

Natural and synthetic zeolites are extremely versatile materials. They can adsorb a variety of liquids and gases, and take part in cation exchange reactions. Zeolites are relatively easy to synthesize from a wide range of natural and man-made materials. One such combination is a mixture of metakaolinite and concentrated sodium hydroxide solution. Once mixed and cured at elevated temperatures, these ingredients react to form a hard, dense, ceramic-like material that contains significant amounts of crystalline tectosilicates (zeolites and feldspathoids) imbedded in an X-ray amorphous sodium aluminosilicate hydrate matrix. This rather unique composite material has been termed a ''hydroceramic.'' The crystalline phases in the hydroceramic have the ability to sequester alkali, alkaline earth and a variety of higher valance cations in lattice positions or within networks of channels and voids. The matrix plays host to the crystallites and to residual amounts of insoluble hydroxide phases. Due to its gel-like character, the matrix also provides considerable strength. A previous publication has established the fact that a mixture of a calcined equivalent ICPP waste (sodium aluminate/hydroxide solution containing {approx}3:1 Na:Al) and fly ash and/or metakaolinite could be cured at various temperatures to produce a monolith containing Zeolite A (80 C) or Na-P1 plus hydroxy sodalite (130 C) dispersed in the alkali aluminosilicate hydrate matrix. Dissolution tests (PCT type) have shown these materials have superior retention of alkali, alkaline earth and heavy metal ions. The zeolitization process is a simple one. Metakaolinite is mixed with a calcined sodium-bearing waste and enough water to make a thick paste. The paste is transferred to a metal canister and ''soaked'' for a few hours at 90 C prior to conventional oven heating or steam autoclaving at -200 C for varying periods of time. Hydroceramics could well be a viable alternative for fixation of low activity sodium-bearing waste (SBW) calcines. The objective of the current study is to adapt this technology for use on site remediation and clean up of caustic waste solutions now in storage in tanks at Hanford and Savannah River. The proposed work is meant to develop a clearer understanding of the advantages and limitations of producing a zeolite-containing hydroceramic from treated low activity SBW, i.e. the effect of processing variables, reaction kinetics, crystal and phase chemistry, and microstructure on the performance of the waste form.

Grutzeck, Michael W.; Kwan, Stephen

2001-06-01

60

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

61

Vapor Phase Transport Synthesis of Zeolites from Sol-Gel Precursors  

SciTech Connect

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

THOMA,STEVEN G.; NENOFF,TINA M.

2000-07-14

62

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

63

Microwave assisted synthesis of zeolite A from metakaolin  

Microsoft Academic Search

Zeolites are generally synthesized by the hydrothermal reaction of sodium aluminosilicate gels prepared from pure chemicals in alkaline medium using conventional heating systems. In the present study, microwave energy is used as a novel heating tool for the synthesis of zeolite A and metakaolin (Al2O3·2SiO2), a calcined product of kaolin (Al2O3·2SiO2·2H2O) has been taken as a combined source for silica

Sathy Chandrasekhar; P. N. Pramada

2008-01-01

64

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

65

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

66

Density functional modelling of silicate and aluminosilicate dimerisation solution chemistry.  

PubMed

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

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

2011-02-14

67

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

Díaz, Urbano; Corma, Avelino

2014-07-21

68

Cesium incorporation and diffusion in cancrinite, sodalite, zeolite, and allophane  

Microsoft Academic Search

At the US Department of Energy’s Hanford site, high level nuclear waste has leaked from underground storage tanks. The waste consists of hyperalkaline solutions, which upon contact with the sediments, caused dissolution of silicate minerals and precipitation of new aluminosilicate minerals. Cancrinite, sodalite, LTA zeolite, and allophane have been identified as the new mineral phases in laboratory simulations. Cesium, the

Jarai Mon; Youjun Deng; Markus Flury; James B. Harsh

2005-01-01

69

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

70

Studies on natural STI zeolite: modification, structure, adsorption and catalysis  

Microsoft Academic Search

A natural STI zeolite discovered in China was identified as a calcium-rich and stellerite-isotype zeolite of stilbite with high crystallinity and an open pore system. Both ion exchange and dealumination can stabilize the framework of the zeolite. The structural properties of the parent and the modified STI zeolites were investigated by X-ray diffraction (XRD), thermogravimetric\\/differential thermogravimetric\\/differental thermal analysis (TG\\/DTG\\/DTA), Fourier

Jun Li; Jin Qiu; Yaojun Sun; Yingcai Long

2000-01-01

71

Chemical conversion of coal waste to micro-meso porous aluminosilicate materials  

NASA Astrophysics Data System (ADS)

The main objective of the present research is to develop chemical synthesis processes to produce useful materials from the class-F type fly ashes in coal wastes. There are two kinds of useful materials studied: one is the microporous aluminosilicate material that has a zeolitic structure with a pore size $700 msp2/g) and strong acid resistance. The mesoporous aluminosilicate materials synthesized from NaOH system have hexagonally arranged pores with a uniform size of 2.74 nm. The Si/Al molar ratio of the mesoporous aluminosilicates was found to be 13.4 but no Na was found. On the other hand, those synthesized from Ca(OH)sb2$ system have larger pores with a uniform size of 3.09 nm. However, the pores are disorderly arranged. The Si/Al ratio and the Ca content were found to be 13.9 and 1.6 wt%.

Chang, Hsiao-Lan

72

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

73

Towards a sustainable manufacture of hierarchical zeolites.  

PubMed

Hierarchical zeolites have been established as a superior type of aluminosilicate catalysts compared to their conventional (purely microporous) counterparts. An impressive array of bottom-up and top-down approaches has been developed during the last decade to design and subsequently exploit these exciting materials catalytically. However, the sustainability of the developed synthetic methods has rarely been addressed. This paper highlights important criteria to ensure the ecological and economic viability of the manufacture of hierarchical zeolites. Moreover, by using base leaching as a promising case study, we verify a variety of approaches to increase reactor productivity, recycle waste streams, prevent the combustion of organic compounds, and minimize separation efforts. By reducing their synthetic footprint, hierarchical zeolites are positioned as an integral part of sustainable chemistry. PMID:24520034

Verboekend, Danny; Pérez-Ramírez, Javier

2014-03-01

74

Amorphous and nanostructured silica and aluminosilicate spray-dried microspheres  

NASA Astrophysics Data System (ADS)

Amorphous silica and aluminosilicate microspheres with diameters in the 0.1-20 ?m range were produced by spray drying method. SEM, TEM and AFM images showed the spherical shape of the obtained particles. Based on thermal analysis data, several heat treatments have been applied on the as-prepared samples in order to check the amorphous state stability of the microspheres and to develop nanosized crystalline phases. As-prepared microspheres remain amorphous up to 1400 °C. By calcination at 1400 °C, cristobalite type nanocrystals are developed on silica sample, while in aluminosilicate sample first are developed mullite type nanocrystals and only after prolonged treatment are developed also cristobalite type nanocrystals. 29Si and 27Al MAS NMR results show that the local order around aluminum and silicon atoms strongly depend on the thermal history of the microspheres.

Todea, M.; Turcu, R. V. F.; Frentiu, B.; Tamasan, M.; Mocuta, H.; Ponta, O.; Simon, S.

2011-08-01

75

Anomalous strain behavior in CO2-saturated zeolitic tuffs  

NASA Astrophysics Data System (ADS)

Zeolites are aluminosilicate minerals with open, cage-like structures and negatively charged frames. Some naturally-occurring zeolites are stabile at geothermal temperatures and have cage structures large enough that small molecules can traverse the intracrystalline cage network easily. This, in addition to their negatively-charged frames, makes these zeolites strong adsorbents (and potentially absorbents) of carbon dioxide. We present a short series of experiments to determine what mechanical effects result from carbon dioxide interaction with zeolitic tuff samples. Three samples were tested: a non-zeolitized grey tuff from the Campi Flegrei region, a zeolitized yellow tuff from the same region, and a zeolite-rich tuff from southern California. The samples were tested in a hydrostatic pressure vessel up to 12 MPa confining pressure. Strains and ultrasonic acoustic velocities were measured under dry conditions as well as during helium injection and carbon dioxide injection. Results show acoustic velocities depend only on differential pressure and not on pore fluid type. Both zeolitized tuffs show decreased strain with gaseous carbon dioxide in the pore space; the decreased strain (or swelling) represents an 8%-16% deviation from the total strain in the helium-saturated case. This indicates that it is the interaction between zeolite minerals and carbon dioxide causing the anomalous strain readings.

Dralus, D. E.; Vanorio, T.; Mavko, G. M.

2012-12-01

76

Antimicrobial activity of commercial zeolite A on Acinetobacter junii and Saccharomyces cerevisiae.  

PubMed

The influence of three samples of commercially produced zeolite A (named A, M and R) in water medium on the bacterium Acinetobacter junii and yeast Saccharomyces cerevisiae was investigated. These microorganisms were used in the bioassay and are not specifically related to the use of zeolite A. All zeolite samples showed the negative influence on the survival and physiological status of A. junii and S. cerevisiae. The EC(50) values for the inhibition of CFU of A. junii were 0.328, 0.138 and 0.139 g l(-1) for zeolite sample A, M and R, respectively. The EC(50) values of tested zeolites for S. cerevisiae, estimated by fermentation and fluorescence microscopy assay, ranged from 2.88 to 5.47 g l(-1). The genotoxic effect of three samples of zeolite to S. cerevisiae was shown by the alkaline comet assay. When assuming all the aspects of zeolite toxicity to bacterium and yeast, the zeolite sample R appeared to be less toxic than the samples A and M. The hydrolysis of zeolite crystals, amorphous aluminosilicate and unreacted gel fraction in water medium and consecutive dissolution and leaching of aluminium and silicon in the form of aluminosilicate molecules (700-1300 Da) was detected. PMID:20705392

Hrenovi?, J; Zeljezi?, D; Kopjar, N; Sarpola, A; Broni?, J; Sekovani?, L

2010-11-15

77

Crystallisation Kinetics of ? Spodumene in Lithium Aluminosilicate Sol–Gel Glasses  

Microsoft Academic Search

ß-spodumene (LiAlSi2O6) is one of the crystalline phase of the lithium aluminosilicate (LAS) glass-ceramics, having a low thermal expansion coefficient. The sol–gel process is an advantageous processing route for LAS materials, compared to melting, as it avoids lithium oxide losses and formation of undesired crystalline phases. It is very important to understand the crystallisation kinetics in order to assess the

M. D. D. R. F. Moreira; I. M. Miranda Salvado; R. F. Silva

2004-01-01

78

Synthesis of a zeolitic thin layer by a vapor-phase transport method: appearance of a preferential orientation of MFI zeolite  

Microsoft Academic Search

Zeolitic membranes were synthesized on a porous alumina support by the vapor-phase transport method using one of two alumina sources: aluminum sulfate and sodium aluminate. By choosing the appropriate period and temperature for drying the aluminosilicate gel on the alumina support, MOR, FER and MFI could be synthesized. MOR was formed when the water content in the dry gel was

Eiichi Kikuchi; Kazuhiko Yamashita; Sachioko Hiromoto; Korekazu Ueyama; Masahiko Matsukata

1997-01-01

79

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

80

21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Hydrated sodium calcium aluminosilicate. 582.2729 Section...Agents § 582.2729 Hydrated sodium calcium aluminosilicate. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

2013-04-01

81

21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Sodium calcium aluminosilicate, hydrated. 182...Anticaking Agents § 182.2729 Sodium calcium aluminosilicate, hydrated. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

2013-04-01

82

Mesoporous aluminosilicates with ordered hexagonal structure, strong acidity, and extraordinary hydrothermal stability at high temperatures.  

PubMed

Highly ordered hexagonal mesoporous aluminosilicates (MAS-5) with uniform pore sizes have been successfully synthesized from assembly of preformed aluminosilcate precursors with cetyltrimethylammonium bromide (CTAB) surfactant. The aluminosilicate precursors were obtained by heating, at 100--140 degrees C for 2--10 h, aluminasilica gels at the Al(2)O(3)/SiO(2)/TEAOH/H(2)O molar ratios of 1.0/7.0--350/10.0--33.0/500--2000. Mesoporous MAS-5 shows extraordinary stability both in boiling water (over 300 h) and in steam (800 degrees C for 2 h). Temperature-programmed desorption of ammonia shows that the acidic strength of MAS-5 is much higher than that of MCM-41 and is comparable to that of microporous Beta zeolite. In catalytic cracking of 1,3,5-triisopropylbenzene and alkylation of isobutane with butene, MAS-5 exhibits greater catalytic activity and selectivity, as compared with MCM-41 and HZSM-5. The MAS-5 samples were characterized with infrared, UV--Raman, and NMR spectroscopy and numerous other techniques. The results suggest that MAS-5 consists of both mesopores and micropores and that the pore walls of MAS-5 contain primary and secondary structural building units, similar to those of microporous zeolites. Such unique structural features might be responsible for the observed strong acidity and high thermal stability of the mesoporous aluminosilicates with well-ordered hexagonal symmetry. PMID:11457329

Zhang, Z; Han, Y; Xiao, F S; Qiu, S; Zhu, L; Wang, R; Yu, Y; Zhang, Z; Zou, B; Wang, Y; Sun, H; Zhao, D; Wei, Y

2001-05-30

83

A sustainable template for mesoporous zeolite synthesis.  

PubMed

A generalized synthesis of high-quality, mesoporous zeolite (e.g., MFI-type) nanocrystals is presented, based on a biomass-derived, monolithic N-doped carbonaceous template. As an example, ZSM-5 single crystals with desirable large-diameter (12-16 nm) intracrystalline mesopores are synthesized. The platform provides scope to optimize template dimensions and chemistry for the synthesis of a range of micro-/mesoporous crystalline zeolites in a cost-effective and highly flexible manner. PMID:24397534

White, Robin J; Fischer, Anna; Goebel, Caren; Thomas, Arne

2014-02-19

84

Regenerative Cu/La zeolite supported desulfurizing sorbents  

NASA Technical Reports Server (NTRS)

Efficient, regenerable sorbents for removal of H2S from fluid hydrocarbons such as diesel fuel at moderate condition comprise a porous, high surface area aluminosilicate support, suitably a synthetic zeolite, and most preferably a zeolite having a free lattice opening of at least 6 Angstroms containing from 0.1 to 0.5 moles of copper ions, lanthanum ions or their mixtures. The sorbent removes sulfur from the hydrocarbon fuel in high efficiency and can be repetitively regenerated without loss of activity.

Voecks, Gerald E. (inventor); Sharma, Pramod K. (inventor)

1991-01-01

85

Effects of additives and heat treatment on the pore size distribution in pelletized zeolite Y  

Microsoft Academic Search

Zeolite Y is a crystalline aluminum silicate used as an adsorbent matrix in the purification of proteins. Particle size enlargement is sometimes required and is achieved by compaction of the zeolite powder followed by heat treatment. To maintain a large surface area available for adsorption, additives are used in the pelletizing procedure. Ultrastable zeolite Y (USY) was compacted into pellets

Daniel Klint; Jan-Olov Bovin

1999-01-01

86

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

87

Interface processes between iron containing aluminosilicate systems and simulated body fluid enriched with protein.  

PubMed

The behaviour of iron containing aluminosilicate samples in Kokubo's simulated body fluid (SBF) and in SBF enriched with bovine serum albumin (BSA) has been investigated. Crystalline samples of (80-x)SiO2 X 20Al2O3 X Fe2O3 system, with x = 5, 10 or 15 mol%, obtained by sol-gel method and heat treated at 1200 degrees C in air for 24 h. Data on electrical conductivity, calcium, phosphorous and potassium concentrations in simulated body fluids after samples soaking in static regime at 37 degrees C, for several periods up to 14 days, were used to estimate the dynamics of these cations on the interface of aluminosilicate samples with SBF, and with SBF containing BSA. The UV-visible and fluorescence spectra recorded from the simulated body fluids after immersion of the investigated aluminosilicate samples evidence changes function on immersion time and Fe2O3 content. PMID:20224936

Magyari, K; Popescu, O; Simon, V

2010-06-01

88

A new microporous polymorph of silica isomorphous to zeolite MCM-22  

SciTech Connect

A zeolite-like silica polymorph was prepared and given the descriptor, ITQ-1. The synthesis of this silica and high Si/Al aluminosilicates is described. The structure of the these materials was studied by X-ray diffraction and NMR.

Camblor, M.A.; Corell, C.; Corma, A. [CSIC-UPV, Valencia (Spain)] [and others] [CSIC-UPV, Valencia (Spain); and others

1996-10-01

89

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

NASA Astrophysics Data System (ADS)

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 potassium-poly(sialate)-nanopolymer type were synthesised at low temperature and studied for their use as potential biomaterials. They were mixed with 13% weight of calcium phosphate like biphasic hydroxyapatite and ?-tricalcium phosphate. In this study, " in vivo" experiments were monitored to evaluate the biocompatibility, the surface and the interface behaviour of these composites when used as bone implants. Moreover, it has been demonstrated using histological and physicochemical studies that the developed materials exhibited a remarkable bone bonding when implanted in a rabbit's thighbone for a period of 1 month. The easy synthesis conditions (low temperature) of this composite and the fast intimate links with bone constitute an improvement of synthetic bone graft biomaterial.

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

2008-11-01

90

Water behaviour in nanoporous aluminosilicates.  

PubMed

This paper briefly reviews results of molecular dynamics simulation studies of water confined in nanoporous aluminosilicates. The behaviour of confined molecules is shown to be influenced by the nature of the host structure, and the size and the topology of the voids. For some of the systems discussed the ambiguity in results of different modelling studies call for the use of extended potential and structural models. Thus, the use of polarizable force fields was shown to be necessary to take into account the variation of the molecular dipole of confined molecules in different environments. PMID:21399287

Smirnov, Konstantin S; Bougeard, Daniel

2010-07-21

91

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

92

Zeolite Characterization.  

National Technical Information Service (NTIS)

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 recover...

H. L. Nigg W. D. Jacobs

2007-01-01

93

Zeolite micromembranes.  

PubMed

Free-standing silicalite-1 (Sil-1) zeolite micromembranes have been successfully fabricated onto silicon substrate. Gas permeation test using permanent gases (i.e., helium, hydrogen, argon and nitrogen) and hydrocarbons (i.e., methane and n-butane) indicates that the micromembranes have excellent permeance flux and high permselectivity. PMID:15100781

Chau, Joseph Lik Hang; Leung, Adrian Yat Lai; Yeung, King Lun

2003-05-01

94

Zeta potential measurements of zeolite Y: Application in homogeneous deposition of particle coatings  

Microsoft Academic Search

Zeolite membranes are typically grown from thin coatings of sub-?m size zeolite particles on porous supports. The particles have the function of seeds in forming a dense zeolite membrane by a secondary growth process. This study focuses on how seed layer coatings can be optimally produced, crack- and agglomerate-free, by dip coating from stable dispersions of nano-crystalline zeolite Y. Surface

Tatsiana Kuzniatsova; Yanghee Kim; Krenar Shqau; Prabir K. Dutta; Henk Verweij

2007-01-01

95

Aluminosilicate Precipitation Impact on Uranium  

SciTech Connect

Experiments have been conducted to examine the fate of uranium during the formation of sodium aluminosilicate (NAS) when wastes containing high aluminate concentrations are mixed with wastes of high silicate concentration. Testing was conducted at varying degrees of uranium saturation. Testing examined typical tank conditions, e.g., stagnant, slightly elevated temperature (50 C). The results showed that under sub-saturated conditions uranium is not removed from solution to any large extent in both simulant testing and actual tank waste testing. This aspect was not thoroughly understood prior to this work and was necessary to avoid criticality issues when actual tank wastes were aggregated. There are data supporting a small removal due to sorption of uranium on sites in the NAS. Above the solubility limit the data are clear that a reduction in uranium concentration occurs concomitant with the formation of aluminosilicate. This uranium precipitation is fairly rapid and ceases when uranium reaches its solubility limit. At the solubility limit, it appears that uranium is not affected, but further testing might be warranted.

WILMARTH, WILLIAM

2006-03-10

96

Investigation of aluminosilicate as a solid oxide fuel cell refractory  

Microsoft Academic Search

Aluminosilicate represents a potential low cost alternative to alumina for solid oxide fuel cell (SOFC) refractory applications. The objectives of this investigation are to study: (1) changes of aluminosilicate chemistry and morphology under SOFC conditions, (2) deposition of aluminosilicate vapors on yttria stabilized zirconia (YSZ) and nickel, and (3) effects of aluminosilicate vapors on SOFC electrochemical performance. Thermal treatment of

Paul S. Gentile; Stephen W. Sofie

2011-01-01

97

Framework-Type Determination for Zeolite Structures in the Inorganic Crystal Structure Database  

NASA Astrophysics Data System (ADS)

In this work a structural characterization of zeolite crystals is performed by identifying the framework type to which each zeolite belongs. The framework type is assigned for 1433 zeolite database entries in the FIZ/NIST Inorganic Crystal Structure Database (ICSD) populating 95 framework types. These entries correspond to both natural and synthetic zeolites. Each ICSD entry is based on published work containing crystallographic information of the zeolite crystalline structure and some physical and chemical data. Today, the Structure Commission of the International Zeolite Association recognizes crystalline materials as belonging to the ``zeolite'' family only if they possess one of the approved framework types by the organization. Such information is of fundamental importance for identifying zeolites, for reference, for zeolite standards, for supporting the discovery of new zeolites, and for crystalline substance selection based on application. Unfortunately, framework-type information is not contained in the ICSD records. The long term goal of this work is filling such gap. Although the ICSD contains an extensive collection of zeolites, inclusion of zeolites belonging to the 191 accepted framework types could substantially expand such collection. The structural determination was achieved via several structural analysis methods based on numerical-computer implementations.

Yang, Shujiang; Lach-Hab, Mohammed; Vaisman, Iosif I.; Blaisten-Barojas, Estela; Li, Xiang; Karen, Vicky L.

2010-09-01

98

Direct imaging of single metal atoms and clusters in the pores of dealuminated HY zeolite  

NASA Astrophysics Data System (ADS)

Zeolites are aluminosilicate materials that contain regular three-dimensional arrays of molecular-scale pores, and they can act as hosts for catalytically active metal clusters. The catalytic properties of such zeolites depend on the sizes and shapes of the clusters, and also on the location of the clusters within the pores. Transmission electron microscopy has been used to image single atoms and nanoclusters on surfaces, but the damage caused by the electron beam has made it difficult to image zeolites. Here, we show that aberration-corrected scanning transmission electron microscopy can be used to determine the locations of individual metal atoms and nanoclusters within the pores of a zeolite. We imaged the active sites of iridium catalysts anchored in dealuminated HY zeolite crystals, determined their locations and approximate distance from the crystal surface, and deduced a possible cluster formation mechanism.

Ortalan, Volkan; Uzun, Alper; Gates, Bruce C.; Browning, Nigel D.

2010-07-01

99

Solar refrigeration utilizing zeolites  

Microsoft Academic Search

Zeolites offer a unique opportunity for a solid-gas adsorption refrigeration system because of their unusual sorption properties, in particular, extremely nonlinear adsorption isotherms. The operating principle of the zeolite system and experimental results are presented. The study demonstrates a zeolite system capable of providing refrigeration and ice production with very good engineering efficiency. This system utilizes natural zeolites as the

D. I. Tchernev

1979-01-01

100

MFI zeolite nanosponges possessing uniform mesopores generated by bulk crystal seeding in the hierarchical surfactant-directed synthesis.  

PubMed

The synthesis of a mesoporous material with uniform mesopore diameters and crystalline MFI zeolite walls has been achieved, simply by seeding the multiammonium surfactant-directed synthesis with bulk zeolite crystals. The bulk seeds disappeared in the final product. As a result of seeding, the mesoporous zeolites could be generated rapidly even at high Al content. PMID:24633468

Jo, Changbum; Cho, Kanghee; Kim, Jaeheon; Ryoo, Ryong

2014-03-25

101

Database of Zeolite Structures  

NSDL National Science Digital Library

The Database of Zeolite Structures is provided by the Structure Commission of the International Zeolite Association. Links include an Atlas of Zeolite Framework Types, Collection of Simulated XRD Powder Patterns for Zeolites, Catalog of Disordered Zeolite Structures, Schemes for Building Zeolite Framework Models, and Zeolite Structure References, as well as various publications. The database can be searched or browsed, and contains several useful tools such as the "input your data" link, which allows the user to enter crystallographic data not available in the database and generate the diffraction pattern.

2000-01-01

102

Preparation of Homogeneous Aluminosilicate Gels by Sol/Gel Techniques.  

National Technical Information Service (NTIS)

The factors affecting the production of homogeneous aluminosilicate gels from alkoxide precursors were investigated. Aluminosilicate gels were made in acidic conditions with a prepolymerization of the silicate precursors followed by the addition of the al...

M. Reese J. Sanchez A. V. McCormick

1993-01-01

103

Role of the zeolitic environment in catalytic activation of methanol  

SciTech Connect

One of the most significant industrial applications of zeolites exploits the ability of the microporous aluminosilicate environment to catalyze the methanol to gasoline (MTG) process. The industrial process proceeds at elevated temperatures ({approximately} 700 K) and methanol pressures which correspond to a loading of {approximately} 5--6 methanol molecules per acidic hydroxyl group, which is believed to be the active site. The authors present an extensive study of the initial stages of the methanol to gasoline conversion in the framework of the ab initio molecular dynamics approach. They investigate the effect of different zeolite environments, methanol loading, and temperature and show that, for understanding the initial adsorption and activation of the adsorbed species, all three factors need to be considered simultaneously. The results allow them to develop a simple model for the activation of the methanol molecule, which elucidates the role of both the zeolite framework and the methanol solvent. The zeolite framework plays an active role in methanol protonation. The solvent significantly softens the C-O bond of the methoxonium, rendering it very anharmonic. High mobility of the methoxonium cation, promoted by some zeolite frameworks, prevents it from forming hydrogen bonds with the active sites and the solvent leading to the activation of the methoxonium species. This picture is shown to be consistent with the experimental infrared spectra.

Stich, I. [Angstrom Technology Partnership, Tsukuba, Ibaraki (Japan)] [Angstrom Technology Partnership, Tsukuba, Ibaraki (Japan); [Slovak Technical Univ., Bratislava (Slovakia); Gale, J.D. [Imperial Coll. of Science, Technology and Medicine, London (United Kingdom). Dept. of Chemistry] [Imperial Coll. of Science, Technology and Medicine, London (United Kingdom). Dept. of Chemistry; Terakura, K. [National Inst. for Advanced Interdisciplinary Research, Higashi, Ibaraki (Japan)] [National Inst. for Advanced Interdisciplinary Research, Higashi, Ibaraki (Japan); [Japan Science and Technology Corp., Kawaguchi, Saitama (Japan); Payne, M.C. [Cavendish Lab., Cambridge (United Kingdom)] [Cavendish Lab., Cambridge (United Kingdom)

1999-04-14

104

Synthesis and characterization of nitrogen substituted zeolites  

NASA Astrophysics Data System (ADS)

The interest in basic solid materials, particularly for basic zeolites has considerably increased in the last two decades because of their potential use in catalysis and separation. Basic zeolites have most often been obtained by ion-exchange or impregnation with alkali metal cations or grafting of organic bases onto zeolite pore walls. Such materials often suffer from instability and/or pore blockage, because none of these approaches places basic sites directly into the zeolite framework. Recently zeolitic materials have been made with some of the bridging oxygen atoms in Si--O--Si and/or Si--O--Al linkages replaced by NH groups, i.e. by substitution of framework oxygen by nitrogen. As a result, the basic strength of the framework increases due to the lower electronegativity of nitrogen with respect to oxygen. In this study, solid base catalysts are obtained by nitrogen substitution of the faujasite type of zeolites under ammonia flow at high temperatures. The efficiency of the reaction is tested by using zeolites with different aluminum contents and extraframework cations and varying the reaction conditions such as ammonia flow rate, reaction temperature and duration. The characterization studies show that high levels of nitrogen substitution can be achieved while maintaining porosity, particularly for NaY and low-aluminum HY zeolites, without a significant loss in the crystallinity. 27Al and 29 Si MAS NMR experiments performed on the nitrogen substituted zeolites show dealumination of the framework and preferential substitution for Si--OH--Al sites at the early stages of the reaction (temperatures at 750--800 °C). No preference is seen for reactions performed at higher temperatures and longer reaction times (e.g., 850 °C and 48 h). X-ray PDF analysis performed on the modified zeolites show that the Si-N distance in the 1st shell is longer than Si-O bond distance and Si-Si/Al bond distance of the Si-O/N-Si/Al linkage decreases, as an indication of a decrease in bond angle. The basicity experiments performed on the zeolites show an increase basicity with increase of the nitrogen content.

Dogan, Fulya

105

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...

106

Modeling of Macroscopic/Microscopic Transport and Growth Phenomena in Zeolite Crystal Solutions Under Microgravity Conditions  

NASA Technical Reports Server (NTRS)

Crystals grown from liquid solutions have important industrial applications. Zeolites, for instance, a class of crystalline aluminosilicate materials, form the backbone of the chemical process industry worldwide, as they are used as adsorbents and catalysts. Many of the phenomena associated with crystal growth processes are not well understood due to complex microscopic and macroscopic interactions. Microgravity could help elucidate these phenomena and allow the control of defect locations, concentration, as well as size of crystals. Microgravity in an orbiting spacecraft could help isolate the possible effects of natural convection (which affects defect formation) and minimize sedimentation. In addition, crystals will stay essentially suspended in the nutrient pool under a diffusion-limited growth condition. This is expected to promote larger crystals by allowing a longer residence time in a high-concentration nutrient field. Among other factors, the crystal size distribution depends on the nucleation rate and crystallization. These two are also related to the "gel" polymerization/depolymerization rate. Macroscopic bulk mass and flow transport and especially gravity, force the crystals down to the bottom of the reactor, thus forming a sedimentation layer. In this layer, the growth rate of the crystals slows down as crystals compete for a limited amount of nutrients. The macroscopic transport phenomena under certain conditions can, however, enhance the nutrient supply and therefore, accelerate crystal growth. Several zeolite experiments have been performed in space with mixed results. The results from our laboratory have indicated an enhancement in size of 30 to 70 percent compared to the best ground based controls, and a reduction of lattice defects in many of the space grown crystals. Such experiments are difficult to interpret, and cannot be easily used to derive empirical or other laws since many physical parameters are simultaneously involved in the process. At the same time, however, there is increased urgency to develop such an understanding in order to more accurately quantify the process. In order to better understand the results obtained from our prior space experiments, and design future experiments, a detailed fluid dynamic model simulating the crystal growth mechanism is required. This will not only add to the fundamental knowledge on the crystallization of zeolites, but also be useful in predicting the limits of size and growth of these important industrial materials. Our objective is to develop macro/microscopic theoretical and computational models to study the effect of transport phenomena in the growth of crystals grown in solutions. Our effort has concentrated so far in the development of separate macroscopic and microscopic models. The major highlights of our accomplishments are described.

Gatsonis, Nikos A.; Alexandrou, Andreas; Shi, Hui; Ongewe, Bernard; Sacco, Albert, Jr.

1999-01-01

107

Preparation and characterization of zeolite-supported molybdenum and cobalt-molybdenum sulfide catalysts  

Microsoft Academic Search

Preparation, characterization and catalysis of zeolite-supported Mo, Co(Ni) and Co(Ni)?Mo sulfide catalysts have been reviewed in the present article. Incomplete sulfidation of Mo oxides and poor dispersion of Mo sulfides were observed for zeolite-supported Mo catalysts prepared by impregnation methods, accompanied by a considerable crystallinity loss at a high calcination temperature. A significant migration of Mo oxide species into zeolite

Yasuaki Okamoto

1997-01-01

108

Unstable-Fe-site-induced formation of mesopores in microporous zeolite Y without using organic templates.  

PubMed

A novel organic template-free strategy for generating mesoporosity in Y zeolites is reported. It is revealed that Fe(3+) functioned as unstable sites in the Fe-NaY zeolite, which promotes deferrization-dealumination, leading to enhanced formation of intra-crystalline mesopores as well as desirable interconnectivity. The mesopore-enriched zeolite exhibits a remarkable ability in conversion of the bulky substrate. PMID:24473160

Guo, Dongdong; Shen, Baojian; Qi, Guodong; Zhao, Liang; Xu, Jun; Deng, Feng; Qin, Yuchen; Guo, Qiaoxia; Ren, Shenyong; Gao, Xionghou; Qin, Song; Wang, Baojie; Zhao, Hongjuan; Liu, Honghai; Pang, Xinmei

2014-03-11

109

Heterogeneous distribution of nanophase aluminosilicate weathering products: Interpreting Martian weathering  

NASA Astrophysics Data System (ADS)

Nanocrystalline alteration products form in a range of soil and regolith weathering environments on Earth. In some weathering systems, poorly crystalline aluminosilicates such as allophane are distributed heterogeneously, as a function of depth in a vertical weathering profile or as a function of micro-environmental factors. Both of these factors can be important for understanding weathering processes on Earth and are particularly important to consider when interpreting allophane on Mars. Chemical and mineralogical measurements of Mars could be confounded by a vertical heterogeneity common to many weathering systems, because what is observed at the surface by spacecraft may not be representative of the complete weathering system. Appropriate caution should be taken to compare surface measurements of Mars to terrestrial weathering environments that examine soil columns. Also, nanocrystalline aluminosilicates are known to form coatings on regolith particles and rock fragments and can be compositionally distinct from weathering products formed in the greater regolith matrix. These types of coatings are particularly important to consider for interpreting remotely sensed spectral measurements because fragmented rocks, from sand to boulders, comprise much of the relatively dust-free surfaces of Mars. Due to their strong influence on spectral observations, coatings could be strongly detectable by thermal infrared spectroscopy relative to coexisting, weakly aggregated fine-grained weathering products, resulting in the oversampling of coatings. Consequently, detected nanocrystalline aluminosilicates phases may not represent the overall weathering system. As an example of these influences, we will consider the high-silica material(s) detected in Mars northern plains. Although there are several models for how this material formed, if it formed by in situ regolith weathering then the high-silica material was precipitated from dissolved regolith materials. Evidence for extensive cryoturbation in the northern plains indicates that subsurface materials have been brought to the surface, thus any vertical compositional heterogeneity resulting from weathering may have been subsequently homogenized. However, small-scale compositional heterogeneities could persist. Although high-silica material may coat particulates that comprise much of the surface, it may only represent only a micro-environment of the subsurface weathering. For example, although we suggest that the northern plains contain a silica-rich allophanic phase, weathering may also have produced more aluminous phases that are undetected in spectra because they do not form coatings. In addition, we will consider the possibility that Martian weathering produces poorly crystalline aluminosilicate phases that are structurally different from true allophane. We will report on the thermal infrared spectral difference between these phases. The details of Martian weathering processes that can be inferred from detection of allophane are limited by how well vertical and micro-environmental heterogeneities are understood and compensated for, for which input from the terrestrial weathering and soil science communities is essential.

Kraft, M. D.; Sharp, T. G.; Rampe, E. B.

2011-12-01

110

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

Microsoft Academic Search

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 SrClâ. 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

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

1993-01-01

111

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

112

Deactivation and coke combustion studies of nanocrystalline zeolite beta in catalytic cracking of used palm oil  

Microsoft Academic Search

Nanocrystalline zeolite beta was synthesized and its catalytic cracking activity for the production of biofuel from used palm oil was determined. The catalyst was characterized for its crystallinity, surface properties and morphology. The effect of reaction temperature on the catalytic cracking activity of nanocrystalline zeolite beta was also studied. The catalyst deactivation was monitored with the time on stream data

Niken Taufiqurrahmi; Abdul Rahman Mohamed; Subhash Bhatia

2010-01-01

113

Improved Catalysts for Heavy Oil Upgrading Based on Zeolite Y Nanoparticles Encapsulated Stable Nanoporous Host. Eighth Semi-Annual Technical Progress Report, April 1, 2006 -September 30, 2006.  

National Technical Information Service (NTIS)

The addition of hydrothermally-aged zeolite Y precursor to an SBA-15 synthesis mixture under a mildly acidic condition resulted in the formation of mesoporous aluminosilicate catalyst, Al-SBA-15, containing strong Bronsted acid sites and aluminum (Al) sta...

2006-01-01

114

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

115

Computational studies of Bronsted acid sites in zeolites  

SciTech Connect

The authors have performed high-level ab initio calculations using both Hartree-Fock (HF) and Moller-Plesset perturbation theory (MP2) 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. In these calculations, which use aluminosilicate cluster models for the zeolite framework with as many a 28 T atoms (T = Si, Al), we included geometry optimization in the local vicinity of the acid site at the HF/6-31G(d) level of theory, and have calculated corrections for zero-point energies, extensions for zero-point energies, extensions to higher basis sets, and the influence of electron correlation. Results for the adsorption energy and geometry of this complex are reported and compared with previous theoretical and experimental values.

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

1995-01-01

116

Model simulations of zeolite supralattices: Semiconductor Si clusters in sodalite  

NASA Astrophysics Data System (ADS)

Periodic three-dimensional arrays of uniform nanosize clusters can be synthesized in the cages and channels of open framework materials. The aluminosilicate frameworks of zeolites have wide electronic band gaps. In addition, they are optically transparent, which opens up the possibility of forming new guest electronic states within the gap, similar to the rare-earth doping of garnets and other insulating matrices. Here we investigate theoretically the atomic geometries, energetics and electronic properties of small semiconducting Si clusters encapsulated in the all-silica sodalite ? cages. The ? cage of sodalite is a building block common to the structure of many zeolites. We find that introducing ``native'' semiconductor clusters within the cages of the host materials gives rise to extremely flat molecular electronic bands in the band gap of the host. The band gaps of the cluster can be altered by the silica potential, geometrical alteration of the cluster, and by quantum confinement.

Demkov, Alexander A.; Sankey, Otto F.

1997-10-01

117

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

118

Lithium alumino-silicate ion source development  

NASA Astrophysics Data System (ADS)

We report experimental progress on Li+ source development in preparation for warm dense matter heating experiments. To uniformly heat targets to electron-volt temperatures for the study of warm dense matter, we are pursuing the use of a low (E < 5 MeV) kinetic energy singly ionized lithium beam and a thin target. Two kinds of lithium (Li+) alumino-silicate ion sources, ?-spodumene and ?-eucryptite, each of area 0.31 cm2, have been fabricated for ion emission measurements. These surface ionization sources are heated to 1200 to 1300 C where they preferentially emit singly ionized alkali ions. Tight process controls were necessary in preparing and sintering the alumino-silicate to the porous tungsten substrate to produce an emitter that gives uniform ion emission, sufficient current density and low beam emittance. Current density limit of the two kinds have been measured, and ion species identification of possible contaminants has been verified with a Wien (E x B) filter.

Roy, Prabir Kumar; Seidl, Peter A.; Kwan, Joe W.; Greenway, Wayne G.; Waldron, William L.; Wu, James K.; Mazaheri, Kavous

2009-11-01

119

Association of indigo with zeolites for improved color stabilization.  

PubMed

The durability of an organic color and its resistance against external chemical agents and exposure to light can be significantly enhanced by hybridizing the natural dye with a mineral. In search for stable natural pigments, the present work focuses on the association of indigo blue with several zeolitic matrices (LTA zeolite, mordenite, MFI zeolite). The manufacturing of the hybrid pigment is tested under varying oxidizing conditions, using Raman and ultraviolet-visible (UV-Vis) spectrometric techniques. Blending indigo with MFI is shown to yield the most stable composite in all of our artificial indigo pigments. In the absence of defects and substituted cations such as aluminum in the framework of the MFI zeolite matrix, we show that matching the pore size with the dimensions of the guest indigo molecule is the key factor. The evidence for the high color stability of indigo@MFI opens a new path for modeling the stability of indigo in various alumino-silicate substrates such as in the historical Maya Blue pigment. PMID:20925983

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

2010-10-01

120

Association of Indigo with Zeolites for Improved Color Stabilization  

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

121

Interface processes between iron containing aluminosilicate systems and simulated body fluid enriched with protein  

Microsoft Academic Search

The behaviour of iron containing aluminosilicate samples in Kokubo’s simulated body fluid (SBF) and in SBF enriched with bovine\\u000a serum albumin (BSA) has been investigated. Crystalline samples of (80–x)SiO2·20Al2O3·xFe2O3 system, with x = 5, 10 or 15 mol%, obtained by sol–gel method and heat treated at 1200°C in air for 24 h. Data on electrical\\u000a conductivity, calcium, phosphorous and potassium concentrations in simulated body

K. Magyari; O. Popescu; V. Simon

2010-01-01

122

Statistical Approach to the Transformation of Fly Ash into Zeolites  

NASA Astrophysics Data System (ADS)

The experimental conversion of F-class fly ash into zeolites is described. The ash, composed mainly of aluminosilicate glass, mullite and quartz, was collected in the Cracow power plant (southern Poland). The experiments involved the heating of fly ash samples in PTFE vessels. Time, temperature and solution composition were the reaction parameters considered in the experiments and in the subsequent modeling. A series of reactions with 0.5, 3 and 5M NaOH solutions (and some with additional 3M NaCl) were carried out at 70°, 100° and 150°C for 12-48 hours under autogenic pressure (not measured) and at a constant ash-to-solution ratio of 33.3 g/l. The following zeolite phases were synthesized: sodalite (SOD structure), hydroxysodalite (SOD), CAN type phases, Na-X (FAU), and NaP1 (GIS). Statistically calculated relationships based on the mineral- and chemical compositions of the reaction products support the conclusion that the type of zeolite phase that crystallizes depends on the concentration of OH- and Cl- in solution and on the temperature of the reaction. The duration of reaction, if on the order of tens of hours, is of less significance. The nature of the zeolite phase that crystalises is controlled by the intensity and selectivity of the substrate dissolution. That dissolution can favour, in sequence, one or other of the components in the substrate, resulting in Si/Al variation in the reaction solutions. Mullite dissolution (decreasing solution Si/Al) characterizes the most advanced reaction stages. The sequence of crystallization of the zeolite phases mirrors the sequential dissolution of substrate components, and the composition of the crystallizing zeolite crystals reflects the changes in the solution Si/Al.

Derkowski, Arkadiusz; Michalik, Marek

2007-01-01

123

Investigation of the adsorption properties and secondary porous structure of adsorbents exhibiting a molecular sieve action Communication 10. Composition, adsorption properties, and limiting adsorption volumes of synthetic type x zeolites  

Microsoft Academic Search

1.The volumes of the large cavities of NaX zeolites with various SiO2\\/Al2O3 ratios in their aluminosilicate skeletons were calculated on the basis of x-ray diffraction data. As the zeolites are enriched in silicon, the volumes of their large cavities are appreciably reduced, but there is a parallel increase in the number of unit cells per unit mass of the dehydrated

M. M. Dubinin; S. P. Zhdanov; E. G. Zhukovskaya; K. O. Murdmaa; E. F. Polstyanov; I. E. Sakavov; N. A. Shishakov

1964-01-01

124

Dispersible Exfoliated Zeolite Nanosheets and Their Application as a Selective Membrane  

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

125

Inorganic-organic composite nanoengineered films using self-assembled monolayers for directed zeolite film growth  

SciTech Connect

This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Zeolites, or molecular sieves, are aluminosilicate cage structures that are typically grown from a heterogeneous mixture of organic template molecules, inorganic salts of alumina and silica, and water. These zeolites are used in industry for catalytic cracking of hydrocarbons (gasoline manufacture from oil), and contaminant removal from chemical production processes. Within one year, we developed a viable method for the deposition of a quaternary ammonium salt amphiphile onto silicon wafer substrates. Using a biomimetic growth process, we were also able to demonstrate the first thin-film formation of a zeolite structure from such an organic template. Additionally, we synthesized the precursor to another amphiphile which was to be for further studies.

Dye, R.C.; Hermes, R.E.; Martinez, M.G.; Peachey, N.M.

1997-10-01

126

Synthesis of ZSM-type Zeolites from Biowaste Gasification Ashes  

Microsoft Academic Search

In Taiwan, over 800 thousand tons per year (TPY) of biowastes such as sugar cane bagasse, sugar cane leaf, rice straw, and corn leaf are produced. These biomasses are the major wastes of farms and are abundantly available. However, these biowastes cause disposal and landfill problems. The main component of these biowaste ashes is SiO2. High crystallinity (99%) zeolites ZSM-5

KUEN-SONG LIN; H. PAUL WANG; NI-BIN CHANG; C. J. G. JOU; M. C. HSIAO

2003-01-01

127

Synthesis, characterization, and mercury adsorption properties of hybrid mesoporous aluminosilicate sieve prepared with fly ash  

PubMed Central

A novel hybrid mesoporous aluminosilicate sieve (HMAS) was prepared with fly ash and impregnated with zeolite A precursors. This improved the mercury adsorption of HMAS compared to original MCM-41. The HMAS was characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption, Fourier transform infrared (FTIR) analysis, transmission electron microscopy (TEM) images and 29Si and 27Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectra. These showed that the HMAS structure was still retained after impregnated with zeolite A. But the surface area and pore diameter of HMAS decreased due to pore blockage. Adsorption of mercury from aqueous solution was studied on untreated MCM-41and HMAS. The mercury adsorption rate of HMAS was higher than that of origin MCM-41. The adsorption of mercury was investigated on HMAS regarding the pH of mercury solution, initial mercury concentration, and the reaction temperature. The experimental data fit well to Langmuir and Freundlich isotherm models. The Dublin–Radushkevich isotherm and the characterization show that the mercury adsorption on HMAS involved the ion-exchange mechanisms. In addition, the thermodynamic parameters suggest that the adsorption process was endothermic in nature. The adsorption of mercury on HMAS followed the first order kinetics.

Liu, Minmin; Hou, Li-an; Xi, Beidou; Zhao, Ying; Xia, Xunfeng

2013-01-01

128

Synthesis, characterization, and mercury adsorption properties of hybrid mesoporous aluminosilicate sieve prepared with fly ash  

NASA Astrophysics Data System (ADS)

A novel hybrid mesoporous aluminosilicate sieve (HMAS) was prepared with fly ash and impregnated with zeolite A precursors. This improved the mercury adsorption of HMAS compared to original MCM-41. The HMAS was characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption, Fourier transform infrared (FTIR) analysis, transmission electron microscopy (TEM) images and 29Si and 27Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectra. These showed that the HMAS structure was still retained after impregnated with zeolite A. But the surface area and pore diameter of HMAS decreased due to pore blockage. Adsorption of mercury from aqueous solution was studied on untreated MCM-41and HMAS. The mercury adsorption rate of HMAS was higher than that of origin MCM-41. The adsorption of mercury was investigated on HMAS regarding the pH of mercury solution, initial mercury concentration, and the reaction temperature. The experimental data fit well to Langmuir and Freundlich isotherm models. The Dublin-Radushkevich isotherm and the characterization show that the mercury adsorption on HMAS involved the ion-exchange mechanisms. In addition, the thermodynamic parameters suggest that the adsorption process was endothermic in nature. The adsorption of mercury on HMAS followed the first order kinetics.

Liu, Minmin; Hou, Li-an; Xi, Beidou; Zhao, Ying; Xia, Xunfeng

2013-05-01

129

Synthesis, characterization, and mercury adsorption properties of hybrid mesoporous aluminosilicate sieve prepared with fly ash.  

PubMed

A novel hybrid mesoporous aluminosilicate sieve (HMAS) was prepared with fly ash and impregnated with zeolite A precursors. This improved the mercury adsorption of HMAS compared to original MCM-41. The HMAS was characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption, Fourier transform infrared (FTIR) analysis, transmission electron microscopy (TEM) images and (29)Si and (27)Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectra. These showed that the HMAS structure was still retained after impregnated with zeolite A. But the surface area and pore diameter of HMAS decreased due to pore blockage. Adsorption of mercury from aqueous solution was studied on untreated MCM-41and HMAS. The mercury adsorption rate of HMAS was higher than that of origin MCM-41. The adsorption of mercury was investigated on HMAS regarding the pH of mercury solution, initial mercury concentration, and the reaction temperature. The experimental data fit well to Langmuir and Freundlich isotherm models. The Dublin-Radushkevich isotherm and the characterization show that the mercury adsorption on HMAS involved the ion-exchange mechanisms. In addition, the thermodynamic parameters suggest that the adsorption process was endothermic in nature. The adsorption of mercury on HMAS followed the first order kinetics. PMID:23687400

Liu, Minmin; Hou, Li-An; Xi, Beidou; Zhao, Ying; Xia, Xunfeng

2013-05-15

130

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

PubMed

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

Medina, Adriana; Gamero, Prócoro; Almanza, José Manuel; Vargas, Alfredo; Montoya, Ascención; Vargas, Gregorio; Izquierdo, María

2010-09-15

131

The geopolymerisation of alumino-silicate minerals  

Microsoft Academic Search

Geopolymers are similar to zeolites in chemical composition, but they reveal an amorphous microstructure. They form by the co-polymerisation of individual alumino and silicate species, which originate from the dissolution of silicon and aluminium containing source materials at a high pH in the presence of soluble alkali metal silicates. It has been shown before that geopolymerisation can transform a wide

Hua Xu; J. S. J. Van Deventer

2000-01-01

132

DFT calculations of EPR parameters for copper(II)-exchanged zeolites using cluster models.  

PubMed

The coordination environment of Cu(II) in hydrated copper-exchanged zeolites was explored through the use of density functional theory (DFT) calculations of EPR parameters. Extensive experimental EPR data are available in the literature for hydrated copper-exchanged zeolites. The copper complex in hydrated copper-exchanged zeolites was previously proposed to be [Cu(H(2)O)(5)OH](+) based on empirical trends in tetragonal model complex EPR data. In this study, calculated EPR parameters for the previously proposed copper complex, [Cu(H(2)O)(5)OH](+), were compared to model complexes in which Cu(II) was coordinated to small silicate or aluminosilicate clusters as a first approximation of the impact of the zeolitic environment on the copper complex. Interpretation of the results suggests that Cu(II) is coordinated or closely associated with framework oxygen atoms within the zeolite structure. Additionally, it is proposed that the EPR parameters are dependent on the Si/Al ratio of the parent zeolite. PMID:20000556

Ames, William M; Larsen, Sarah C

2010-01-14

133

The composition range of aluminosilicate geopolymers  

Microsoft Academic Search

Aluminosilicate geopolymers with SiO2\\/Al2O3 ratios ranging from 0.5 to 300 have been prepared from mixtures of dehydroxylated kaolinite with either ?-Al2O3 or fine Aerosil SiO2, with the ratios Na2O\\/SiO2 and H2O\\/SiO2 kept constant throughout the series. All the compositions hardened at ambient temperature, but the high-alumina compositions were of low strength and did not display typical XRD and NMR geopolymer

Ross A. Fletcher; Kenneth J. D. MacKenzie; Catherine L. Nicholson; Shiro Shimada

2005-01-01

134

"A Novel Synthesis of Zeolite W..."  

SciTech Connect

Zeolite W has been synthesized using organometallic silicon and aluminum precursors in two hydrothermal systems: organocation containing and organocation-free. The reaction using the organocation yielded a fully crystalline, relatively uniform crystal size product, with no organic molecules occluded in the pores. In contrast, the product obtained from an identical reaction, except for the absence of the organocation, contained amorphous as well as crystalline material and the crystalline phase showed a large diversity of both crystal size and morphology. The use of organometallic precursors, either with or without an organocation, allows for the crystallization of the MER framework at much lower 0H/Si02 and (K+ Na - Al)/Si ratios than is typical of inorganic systems. The reaction products were characterized by XRD, SEM, EDS, and thermal analyses.

Nenoff, Tina M.; Thoma, Steven G.

1999-05-07

135

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

136

Role of ammonium fluoride in crystallization process of beta zeolite  

NASA Astrophysics Data System (ADS)

The addition of Na + cations to the starting gel prepared using NH 4F significantly prolonged the crystallization time of beta zeolite. However, in the case of pure silica beta zeolite an addition of more NH 4F reduced the crystallization time by one-half. From 29Si MAS NMR measurements, the signal attributed to pentacoordinated silicon was found to be more pronounced for pure silica beta zeolite in the presence of Na + cations even in the solid phase with low crystallinity, as compared to that in the absence of Na + cations. Considering the results of theoretical calculation, because of more energetically stable state of Na +[SiO 4/2F] - species, it could be presumed that Na +[SiO 4/2F] - species might exist in pure silica beta zeolite. Furthermore, as confirmed by 19F MAS NMR measurements tetraethylammonium fluoride (TEAF) species were enclathrated intact in solid phase during the initial crystallization stage. This suggests that TEAF species are required for the formation of beta zeolite framework, in other words, as "SDA" which conditions the formation of kinetically favored phase, i.e., beta zeolite. Moreover, since part of TEA + cations is replaced by sodium cations, forming Na +[SiO 4/2F] - species, the amount of TEA +[SiO 4/2F] - species involved in either nucleation or crystal growth decreases and thus the crystallization time becomes longer.

Jon, Hery; Oumi, Yasunori; Itabashi, Keiji; Sano, Tsuneji

2007-09-01

137

Microwave assisted two-step process for rapid synthesis of Na-A zeolite from coal fly ash  

SciTech Connect

Using the amorphous aluminosilicate of coal fly ash (FA), Na-A zeolite was synthesized. The FA particles mechanically treated with ball mill were added into a tube made of cellulose filter paper, and they were pretreated with a NaOH solution by refluxing under microwave (MW) irradiation for 60 min. The amorphous aluminosilicate of FA was dissolved during the pretreatment. After pretreatment, the tube was removed and NaAlO{sub 2} solution was added to the residual solution to control the SiO{sub 2}/Al{sub 2}O{sub 3} molar ratio of the solution ranging from 0.5 to 4.0. The precipitates thus formed were aged by refluxing under MW irradiation for 60 min. After aging, white precipitates were yielded over the whole SiO{sub 2}/Al{sub 2}O{sub 3} range. At SiO{sub 2}/Al{sub 2}O{sub 3} = 0.51.0, the materials were identified as Na-A zeolite with a little amount of hydroxysodalite. The amorphous aluminosilicate emerged slightly at SiO{sub 2}/Al{sub 2}O{sub 3} = 2.0. The diffraction peaks of Na-A zeolite and hydroxysodalite disappeared at SiO{sub 2}/Al{sub 2}O{sub 3} = 4.0. The cation exchange capacity of Na-A zeolite formed at SiO{sub 2}/Al{sub 2}O{sub 3} = 0.5 and 1.0 was 4.32 and 4.70 meq.gP{sup -1}, respectively. The results obtained led to the conclusion that Na-A zeolite can be synthesized from milled FA for 120 min under MW irradiation.

Tanaka, H.; Fujimoto, S.; Fujii, A.; Hino, R.; Kawazoe, T. [Shimane University, Shimane (Japan). Faculty of Science & Engineering

2008-01-15

138

Zeolites in Soil Environments.  

National Technical Information Service (NTIS)

Over the past 25 years, natural zeolites have been examined for a variety of agricultural and environmental applications because of their unique cation-exchange, adsorption, and molecular sieving properties and their abundance in near-surface, sedimentary...

D. W. Ming J. L. Boettinger

2001-01-01

139

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

140

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

141

Properties of Natural Zeolites.  

National Technical Information Service (NTIS)

Samples of the naturally occuring zeolites phillipsote, clinoptilolite, erionite, and chabazite have been surveyed for their gas adsorption, ion exchange, and other characteristics. Chabazite and erionite, which are generally more stable, also have higher...

R. A. Munson

1973-01-01

142

Hydraulic conductivity of compacted zeolites.  

PubMed

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

Oren, A Hakan; Ozdamar, Tu?çe

2013-06-01

143

Brillouin scattering study on the single-crystal elastic properties of natrolite and analcime zeolites  

NASA Astrophysics Data System (ADS)

The Brillouin light-scattering technique was used to investigate the single-crystal elastic properties of two aluminosilicate zeolites, natrolite (NAT) and analcime (ANA), at ambient conditions. An inversion of the acoustic velocity data results in the full set of elastic stiffness moduli (Cij's) for both materials. From the single-crystal moduli the aggregate adiabatic bulk moduli (Ks), shear moduli (G), and Poisson's ratios (?) were found to be Ks=48.5(1.0) GPa, G=31.6(1.0) GPa, and ?=0.232(5) for NAT, and Ks=59.8(1.2) GPa, G=32.1(1.0) GPa, and ?=0.272(5) for ANA (Voigt-Reuss-Hill averages). The bulk and shear moduli of both zeolites are relatively low compared with those of densely packed aluminosilicates, reflecting an open framework structure of (Al,SiO4) tetrahedra which is easily deformed by bending the Si-O-Al angles. As expected for a less dense crystal, NAT is softer and more compressible than ANA. An evaluation of the directional Young's moduli shows that the compressibility of NAT is nearly uniform along the [100] and [010] axes, while [001] is stiffer, in agreement with previous compression studies. We do not find experimental evidence of negative Poisson's ratios for NAT zeolites as predicted by recent theoretical calculations.

Sanchez-Valle, Carmen; Sinogeikin, Stanislav V.; Lethbridge, Zoe A. D.; Walton, Richard I.; Smith, Christopher W.; Evans, Kenneth E.; Bass, Jay D.

2005-09-01

144

Photoelastic response of alkaline earth aluminosilicate glasses.  

PubMed

Understanding the structural origins of the photoelastic response in oxide glasses is important for discovering new families of zero-stress optic glasses and for developing a predictive physical model. In this Letter, we have investigated the composition dependence of the stress optic coefficient C of 32 sodium aluminosilicate glasses with different types of alkaline earth oxides (MgO, CaO, SrO, and BaO). We find that most of the composition dependence of the stress optic response can be captured by a linear regression model and that the individual contributions from the alkaline earths to C depend on the alkaline earth-oxygen bond metallicity. High bond metallicity is required to allow bonds to be distorted along both the bonding direction and perpendicular to it. These findings are valuable for understanding the photoelastic response of oxide glasses. PMID:22297330

Smedskjaer, Morten M; Saxton, Scott A; Ellison, Adam J; Mauro, John C

2012-02-01

145

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

146

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

147

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

Conrad Ingram

2003-09-03

148

Surface Modification of Sodium Aluminosilicate Glasses Using Microwave Energy.  

National Technical Information Service (NTIS)

Microwave energy has been used in ion exchange reactions for four sodium-aluminosilicate compositions. The exchangeable cation in the glass sodium (+) was replaced at the surface by a larger atomic radii cation Potassium (+). Secondary ion mass spectrosco...

Z. Fathi I. Ahmad J. H. Simmons D. E. Clark A. R. Loding

1992-01-01

149

Ionic Conductivity of Some Lithium Silicates and Aluminosilicates.  

National Technical Information Service (NTIS)

Lithium silicates and aluminosilicates exhibiting a variety of typical silicate structures have been synthesized, and their ionic conductivities measured over a wide range of temperature and frequency, using a-c methods and blocking electrodes. The freque...

I. D. Raistrick C. Ho R. A. Huggins

1975-01-01

150

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

Microsoft Academic Search

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 (0.54–0.80nm) were studied over the conversion of waste cooking palm oil, yields of Organic Liquid Product (OLP) and gasoline

Niken Taufiqurrahmi; Abdul Rahman Mohamed; Subhash Bhatia

2011-01-01

151

Crystallization of JBW, CAN, SOD and ABW type zeolite from transformation of meta-kaolin  

Microsoft Academic Search

The crystallization of low silica zeolites, including JBW, CAN, SOD and Li-ABW was investigated on the hydrothermal transformation of China meta-kaolin in alkaline medium at 473 K, and characterized with XRD, SEM and 29Si MAS NMR. The significant influence of the inorganic additives on the products formed was observed. The crystallization process of JBW zeolite with high crystallinity from the

De-Chang Lin; Xiao-Wen Xu; Feng Zuo; Ying-Cai Long

2004-01-01

152

Differences in Al distribution and acidic properties between RTH-type zeolites synthesized with OSDAs and without OSDAs.  

PubMed

In addition to the original preparation route of the RTH-type zeolites using 1,2,2,6,6-pentamethylpiperidine (PMP) as an organic structure directing agent (OSDA), we have found that simpler organic amines such as N-methylpiperidine and pyridine can be used as alternative OSDAs in place of PMP. Furthermore, we have established a synthesis method for preparing the RTH-type zeolites without using any OSDAs. In this study, RTH-type aluminosilicates were synthesized with different types of OSDA or without using any OSDAs. The obtained zeolites synthesized with different preparation methods were characterized by using various techniques, especially high-resolution (27)Al MAS NMR and in situ FT-IR techniques using CO adsorption. The relationship between the preparation method and the catalytic performance in the methanol to olefins (MTO) reaction was discussed. Finally, the distribution of Al species in the RTH-framework was clarified. PMID:24451998

Liu, Ming; Yokoi, Toshiyuki; Yoshioka, Masato; Imai, Hiroyuki; Kondo, Junko N; Tatsumi, Takashi

2014-03-01

153

Molecular dynamics simulation of reconstructive phase transitionson an anhydrous zeolite  

NASA Astrophysics Data System (ADS)

The structural transformation of a framework aluminosilicate, Li-ABW , is studied using molecular dynamics. The calculations are carried out by applying the method presented by

Marto?ák et al. [Phys. Rev. Lett. 90, 075503 (2003)
], that allows for the exploration of the Gibbs free energy as a function of the cell parameters by history-dependent dynamics. We show that this technique allows for an extensive exploration of the phase space also for complex polyatomic material, such as a zeolite, and allows for the successful prediction of a reconstructive phase transition at the pressure and temperature of experimental relevance. In particular, we observe a reconstructive transition from anhydrous Li-ABW to eucryptite at the temperature of ˜920 K , as experimentally observed. The steps initiating the transformation and the transition pathway are discussed.

Ceriani, C.; Laio, A.; Fois, E.; Gamba, A.; Marto?ák, R.; Parrinello, M.

2004-09-01

154

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

SciTech Connect

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

Conrad Ingram; Mark Mitchell

2005-03-21

155

Changes in the Vibrational Spectra of Zeolites Due to Sorption of Heavy Metal Cations  

NASA Astrophysics Data System (ADS)

This work presents the results of spectroscopic (MIR and Raman) studies of zeolite structures after immobilization of heavy metal cations from aqueous solutions. The sorption of Ag+, Cu2+, Cd2+, Pb2+, Zn2+, and Cr3+ ions has been conducted on zeolites belonging to different structural groups, i.e., sodium forms of natural chabazite, mordenite, ferrierite, and clinoptilolite, as well as on synthetic zeolite Y. Systematic changes in intensities and positions of the bands corresponding to the characteristic ring vibrations have been observed in the measured spectra. The most visible changes are observed in the FT-IR spectra of the samples in the range of 850-450 cm-1, and in the Raman spectra in the range of 600-250 cm-1. Depending on the zeolite structure, the bands, which can be regarded as a kind of indicator of ion exchange, were indentifi ed. For example, in the case of IR spectra, these bands are at 766, 703, 648, 578, and 506 cm-1 for zeolite Y, at 733 and 560 cm-1 for mordenite, at 675 cm-1 for clinoptilolite, etc. The degree of changes depends on both the type of cation and its concentration in the initial solution. This is connected with the way of binding of metal ions to the zeolite aluminosilicate framework, i.e., a proportion of the ion exchange and chemisorption in the process. Cations mainly undergoing ion exchange, such as Cd2+ or Pb2+, have the greatest impact on the character of the spectra. On the other hand, Cr3+ ions practically do not modify the spectra of zeolites. Results of IR and Raman spectroscopic studies have been compared with those obtained by atomic absorption spectroscopy (AAS), from which the proportion of ion exchange to chemisorption in the process and the effective cation exchange capacity of the individual samples have been estimated.

Król, M.; Mozgawa, W.; Barczyk, K.; Bajda, T.; Kozanecki, M.

2013-11-01

156

New mimic of zeolite: heterometallic organic host framework accommodating inorganic cations.  

PubMed

Presented here is a heterometallic organic framework [Na(2)(H(2)O)(10)](n)[CuZn(4)(mu(3)-OH)(4)(btec)(2)](n).2nH(2)O (1, btec = 1,2,4,5-benzenetetracarboxylate) that incorporates mixed Cu(2+)-Zn(2+) oxide chains and accommodates Na(+) cations as extraframework guest species; such a building mode is comparable to that of aluminosilicate zeolites where the porous framework combines two kinds of structural building units (such as [SiO(4)] and [AlO(4)]) and one kind of inorganic-templating cation. PMID:20424767

Chen, Yu-Biao; Kang, Yao; Zhang, Jian

2010-05-14

157

Advances in nanosized zeolites.  

PubMed

This review highlights recent developments in the synthesis of nanosized zeolites. The strategies available for their preparation (organic-template assisted, organic-template free, and alternative procedures) are discussed. Major breakthroughs achieved by the so-called zeolite crystal engineering and encompass items such as mastering and using the physicochemical properties of the precursor synthesis gel/suspension, optimizing the use of silicon and aluminium precursor sources, the rational use of organic templates and structure-directing inorganic cations, and careful adjustment of synthesis conditions (temperature, pressure, time, heating processes from conventional to microwave and sonication) are addressed. An on-going broad and deep fundamental understanding of the crystallization process, explaining the influence of all variables of this complex set of reactions, underpins an even more rational design of nanosized zeolites with exceptional properties. Finally, the advantages and limitations of these methods are addressed with particular attention to their industrial prospects and utilization in existing and advanced applications. PMID:23803972

Mintova, Svetlana; Gilson, Jean-Pierre; Valtchev, Valentin

2013-08-01

158

Microheterogeneous dispersion electrolysis with nanoscale electrode-modified zeolites 1 Dedicated to Professor K.B. Oldham on the occasion of his retirement from Trent University. 1  

Microsoft Academic Search

This study demonstrates the utility of supported nanoscale Pt or RuO2 particles as ensembles of ultramicroelectrodes for controlled potential electrolyses, including implications for their use in practical electrosyntheses. Microheterogeneous dispersions of nanoelectrode-modified aluminosilicate zeolites (M-Z) increase the effective electrode area of conventional large surface electrodes in electrolytes of customary ionic strength (??0.1 M). For [Fe(CN)6]3? solutions (in pH 6.86 phosphate

Carol A Bessel; Debra R Rolison

1997-01-01

159

Adsorption of aqueous Zn(II) species on synthetic zeolites  

NASA Astrophysics Data System (ADS)

To supply a good quality drinkable water tends to become a strategic task in both developed and under development countries in the world due to the number of potential contamination sources. One of the major problems is derived from the presence of heavy toxic metals like zinc or lead resulting from industrial activities. Zeolites are known as very efficient mineral substrates for fixing aqueous ionic species through their wide range of channels present in the crystalline structure and due to their strong surface reactivity. MicroPIXE coupled with microRBS (3.05 MeV 4He + ions) have been used to quantify the incorporation of zinc within two commercial zeolites containing alkali elements (zeolite X and clinoptilolite) in the concentration range of: 0.0002-0.05 M at neutral pH. At the beginning of the interaction between zeolite and Zn(II) solution, the adsorption process exhibits a direct proportionality between the content of zinc fixed on the mineral substrate and the aqueous concentration up to 0.01 M. Beyond this point a saturation effect seems to occur, indicating the strong decrease of available adsorption sites. Sodium or potassium ions are probably exchanged with Zn(II) ions during this process. The compared behaviour of the two zeolites is then discussed in terms of kinetic effects based on ionic radius values. A co-adsorption test carried on with a 50-50% Zn(II) 0.001 M-Pb(II) 0.001 M solution shows that lead does not occupy the same sites as zinc because the content of zinc fixed on the zeolite sample exactly corresponds to the result obtained with a pure 0.001 M Zn(II) solution. All these data clearly showed that zeolite surface reactivity is greatly influenced by the mineral cage-like structure and particularly the presence of pockets, spaces and channels.

Badillo-Almaraz, Véronica; Trocellier, Patrick; Dávila-Rangel, Ignacio

2003-09-01

160

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

SciTech Connect

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

Koh, Pei-Yoong; Yan, Jing; Ward, Jason; Koros, William J. [School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Drive NW, Atlanta, GA 30332-0100 (United States)] [School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Drive NW, Atlanta, GA 30332-0100 (United States); Teja, Amyn S., E-mail: amyn.teja@chbe.gatech.edu [School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Drive NW, Atlanta, GA 30332-0100 (United States); Xu, Bo [School of Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 801 Ferst Drive NW, Atlanta, GA 30332-0295 (United States)] [School of Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 801 Ferst Drive NW, Atlanta, GA 30332-0295 (United States)

2011-03-15

161

Influence of aluminum speciation on the stability of aluminosilicate glasses against crystallization  

NASA Astrophysics Data System (ADS)

In this letter, we investigate the correlation between glass microstructure and glass stability (GS) in soda lime aluminosilicates. We find a loss of GS (i.e., an onset of crystallization) in the glasses above a critical concentration of Al2O3 when heating at the standard rate of 20 K/min. This loss in GS may be attributed to formation of five-fold coordinated Al species when [Al2O3]/[Na2O] > 1. The primary crystalline phase is identified as nepheline, in which Al exists in four-fold coordination. This implies that the five-fold coordinated Al is energetically less stable compared to Al in a tetrahedral environment.

Zheng, Qiuju; Smedskjaer, Morten M.; Youngman, Randall E.; Potuzak, Marcel; Mauro, John C.; Yue, Yuanzheng

2012-07-01

162

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

163

Synthesis and characterization of zeolites prepared from industrial fly ash.  

PubMed

In this paper, we present the possibility of using fly ash to produce synthetic zeolites. The synthesis class F fly ash from the Stalowa Wola SA heat and power plant was subjected to 24 h hydrothermal reaction with sodium hydroxide. Depending on the reaction conditions, three types of synthetic zeolites were formed: Na-X (20 g fly ash, 0.5 dm(3) of 3 mol?·?dm(-3) NaOH, 75 °C), Na-P1 (20 g fly ash, 0.5 dm(3) of 3 mol?·?dm(-3) NaOH, 95 °C), and sodalite (20 g fly ash, 0.8 dm(3) of 5 mol?·?dm(-3) NaOH?+?0.4 dm(3) of 3 mol?·?dm(-3) NaCl, 95 °C). As synthesized materials were characterized to obtain mineral composition (X-ray diffractometry, Scanning electron microscopy-energy dispersive spectrometry), adsorption properties (Brunauer-Emmett-Teller surface area, N2 isotherm adsorption/desorption), and ion exchange capacity. The most effective reaction for zeolite preparation was when sodalite was formed and the quantitative content of zeolite from X-ray diffractometry was 90 wt%, compared with 70 wt% for the Na-X and 75 wt% for the Na-P1. Residues from each synthesis reaction were the following: mullite, quartz, and the remains of amorphous aluminosilicate glass. The best zeolitic material as characterized by highest specific surface area was Na-X at almost 166 m(2)?·?g(-1), while for the Na-P1 and sodalite it was 71 and 33 m(2)?·?g(-1), respectively. The ion exchange capacity decreased in the following order: Na-X at 1.8 meq?·?g(-1), Na-P1 at 0.72 meq?·?g(-1), and sodalite at 0.56 meq?·?g(-1). The resulting zeolites are competitive for commercially available materials and are used as ion exchangers in industrial wastewater and soil decontamination. PMID:24838802

Franus, Wojciech; Wdowin, Magdalena; Franus, Ma?gorzata

2014-09-01

164

Crystallization of lanthanum and yttrium aluminosilicate glasses  

NASA Astrophysics Data System (ADS)

The crystallization behaviour of aluminosilicate glasses of lanthanum (LAS) and yttrium (YAS) containing 2-8 mol% of Ln 2O 3 (Ln = La or Y), 12-30 mol% of Al 2O 3, and 64-80 mol% of SiO 2 has been studied by DTA, XRD and SEM-EDX analysis. X-ray diffraction results indicate the presence of the mullite phase and La 2Si 2O 7 in the monoclinic high-temperature G form (group space P2 1/c) for the LAS glasses, and mullite y-Y 2Si 2O 7 in the monoclinic structure (group space C2/m) and a small amount of ?-Y 2Si 2O 7 in the orthorhombic structure (space group Pna2) for the YAS. For both cases, very little tridymite phase is observed. The results also show that the values of Tg for YAS are higher than those for LAS glasses. The crystallization of LAS glasses is more difficult than that of YAS. For all samples, we observed only one kind of mullite (Al/Si = 3.14).

Sadiki, Najim; Coutures, Jean Pierre; Fillet, Catherine; Dussossoy, Jean Luc

2006-01-01

165

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

PubMed

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

Pinkert, Denise; Limberg, Christian

2014-07-21

166

Clinoptilolite zeolitized tuff from Central Alborz Range, North Iran  

NASA Astrophysics Data System (ADS)

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

Taghipour, Batoul

2010-05-01

167

Use of hydrogen sulfide to improve benzene production over zeolites  

Microsoft Academic Search

A process is described for producing aromatic hydrocarbons, the process comprising contacting a feedstock comprising one or more of ethylene, propane and propylene with a catalyst comprising a crystalline zeolite material having the structure of ZSM-5 or ZSM-11. The contacting takes place under sufficient aromatization conditions including a temperature of from about 100°C to about 700°C, a pressure of from

1986-01-01

168

Hydrophobic zeolites for biofuel upgrading reactions at the liquid-liquid interface in water/oil emulsions.  

PubMed

HY zeolites hydrophobized by functionalization with organosilanes are much more stable in hot liquid water than the corresponding untreated zeolites. Silylation of the zeolite increases hydrophobicity without significantly reducing the density of acid sites. This hydrophobization with organosilanes makes the zeolites able to stabilize water/oil emulsions and catalyze reactions of importance in biofuel upgrading, i.e., alcohol dehydration and alkylation of m-cresol and 2-propanol in the liquid phase, at high temperatures. While at 200 °C the crystalline structure of an untreated HY zeolite collapses in a few hours in contact with a liquid medium, the functionalized hydrophobic zeolites keep their structure practically unaltered. Detailed XRD, SEM, HRTEM, and BET analyses indicate that even after reaction under severe conditions, the hydrophobic zeolites retain their crystallinity, surface area, microporosity, and acid density. It is proposed that by preferentially anchoring hydrophobic functionalities on the external surface, the direct contact of bulk liquid water and the zeolite is hindered, thus preventing the collapse of the framework during the reaction in liquid hot water. PMID:22548687

Zapata, Paula A; Faria, Jimmy; Ruiz, M Pilar; Jentoft, Rolf E; Resasco, Daniel E

2012-05-23

169

Separations Using Zeolite Membranes  

Microsoft Academic Search

This overview describes some of the main features of the use of zeolite membranes for separation applications. Four different types of separations are considered: separation of non-adsorbing compounds, of organic molecules, of permanent gases from vapors, and of water (or polar molecules) from organic (or non-polar) species. Several factors, such as the limiting pore size and pore size distribution, surface

Joaquín Coronas; Jesús Santamaría

1999-01-01

170

Diffusion in zeolites  

Microsoft Academic Search

Recent developments in the study of intracrystalline diffusion in zeolites by novel macroscopic methods and the results obtained by some of these methods are reviewed. For many systems there is a significant discrepancy between the macroscopic and microscopic (QENS, PFG NMR) diffusivity values. A possible explanation is suggested.

Douglas M. Ruthven

1995-01-01

171

'Water Splitting' by Titanium Exchanged Zeolite A.  

National Technical Information Service (NTIS)

Visually detectable and chromatographically and mass spectrally identified hydrogen gas evolves from titanium (III) exchanged zeolite A immersed in water and illuminated with visible light. Titanium(III) exchanged zeolite X and zeolite Y do not produce th...

S. M. Kuznicki E. M. Eyring

1978-01-01

172

XPS analysis of aluminosilicate microspheres bioactivity tested in vitro  

NASA Astrophysics Data System (ADS)

The study aims to characterize surface properties of aluminosilicate microspheres incorporating yttrium, with potential biomedical applications. Micrometric particles of spherical shape were obtained by spray drying method. The behavior of aluminosilicate microspheres without yttrium and with yttrium was investigated under in vitro conditions, by seven days incubation in simulated body fluid (SBF). The surface elemental composition and the atomic environments on outermost layer of the microspheres, prior to and after incubation in SBF were evaluated by X-ray photoelectron spectroscopy (XPS) in order to investigate their bioactivity. The results were analyzed to underline the effect of yttrium addition on surface properties of the aluminosilicate microspheres and implicitly on the behavior of the samples in simulated body environments.

Todea, M.; Vanea, E.; Bran, S.; Berce, P.; Simon, S.

2013-04-01

173

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

174

The influence of sodium carbonate on sodium aluminosilicate crystallisation and solubility in sodium aluminate solutions  

Microsoft Academic Search

Isothermal batch precipitation experiments have been carried out in synthetic Bayer liquors to investigate the effects of sodium carbonate concentration on both silica solubility and the crystallisation of sodium aluminosilicates. At both 90 and 160°C cancrinite (generically defined as a sodium aluminosilicate of space group P63) is the stable solid phase. Sodalite (generically defined as a sodium aluminosilicate with space

Kali Zheng; Andrea R. Gerson; Jonas Addai-Mensah; Roger St. C. Smart

1997-01-01

175

Binding and catalytic reduction of NO by transition metal aluminosilicates  

SciTech Connect

Na, Co{sup 2+}, Ce{sup 3+}, and Co{sup 2+}Ce{sup 3+} exchanged A type zeolite have been tested for NO and N{sub 2}O adsorption and decomposition at room temperature. Dynamic temperature programmed desorption (TPD) studies were also carried out with these four zeolites, as well as with CeO{sub 2} and CoA zeolite mixed with CeO{sub 2}. It was demonstrated that NO was especially decomposed into N{sub 2}, with some N{sub 2}, with some N{sub 2}O, over the doubly ion exchanged CoCeA zeolite that contained 1.77 Co and 2 Ce per unit cell. Some segregation of CeO{sub 2} occurred during these experiments, and a lower content of Ce in the CoCeA zeolite might be utilizable.

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

1992-06-01

176

Zeolite exposure and associated pneumoconiosis  

SciTech Connect

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

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

1985-06-01

177

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

178

Luminescent properties of bismuth centres in aluminosilicate optical fibres  

SciTech Connect

The shape and spectral position of the luminescence bands of bismuth-doped aluminosilicate glass fibres are shown to depend on excitation power and wavelength. This indicates that the red and IR luminescence bands are composed of several components. The absorption and radiative transitions involved are identified, and a diagram of energy levels and transitions is obtained for four modifications of a bismuth centre in different environments in the aluminosilicate glass network. The effect of local environment on the optical properties of the bismuth centres is examined. (optical fibres and waveguides)

Bulatov, Lenar I [M. V. Lomonosov Moscow State University, Faculty of Physics, Moscow (Russian Federation); Mashinskii, Valerii M; Dvoirin, Vladislav V; Dianov, Evgenii M [Fiber Optics Research Center, Russian Academy of Sciences, Moscow (Russian Federation); Kustov, Evgenii F [Moscow Power Engineering Institute, Moscow (Russian Federation)

2010-02-28

179

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

180

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

SciTech Connect

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

Ogino, I.; Gates, B.C.

2009-05-22

181

Cesium Incorporation and Diffusion in Cancrinite, Soalite, Zeolite, and Allophane  

SciTech Connect

At the US Department of Energy?s Hanford site, high level nuclear waste has leaked from under4 ground storage tanks. The waste consists of hyperalkaline solutions, which upon contact with the 5 sediments, caused dissolution of silicate minerals and precipitation of secondary aluminosilicate minerals. Cancrinite, sodalite, LTA zeolite, and allophane have been identified as the new mineral phases 7 in laboratory simulations. Cesium, the major radionuclide in the waste solutions, may be incorporated 8 into the structural framework of the precipitates. The objectives of this study were to determine the 9 resistance of incorporated Cs to ion exchange and the mobility and diffusion coefficient of Cs in the 10 minerals. The minerals were synthesized in solutions mimicking the tank waste and were washed with 11 deionized water. Two sets of experiments were conducted to test the resistance of Cs to ion exchange. 12 In the first set, Cs was exchanged three times at 80 C by 0.5 N Na, K, or Ca. The Cs remaining in 13 minerals was quantified after acid digestion. In the second set, we studied the Cs desorption kinetics 14 by using 0.1 M Na as ion exchanger. Cesium concentration in the solution phase was measured as a 15 function of time for 23 days. Cesium incorporated in sodalite and cancrinite was far more difficult to 16 replace than that in LTA zeolite and allophane. Most of the incorporated Cs (94?99%) in LTA zeolite 17 and allophane was readily exchangeable with Na or K; less than 20% of Cs in sodalite and <55% of 2 Cs in cancrinite could be exchanged. The fraction of desorbed Cs was also affected by the exchanging 19 ions; the ion with lowest dehydration energy (K) was the most effective in replacing Cs. The results 20 of the desorption kinetics experiments showed that Cs desorbed quickly from LTA zeolite and the Cs 21 diffusion coefficient was close to that in solution; i.e., about 10?9 m2/s. Solid-state NMR analysis 22 supported the high mobility of Cs in LTA zeolite. Cesium desorption from cancrinite, sodalite, and 23 allophane, however, was slow, suggesting that Cs was trapped in cages and channels of these minerals. 24 Effective diffusion coefficients for Cs in cancrinite and sodalite were near 10?14 m2/s.

Mon, Jarai; Deng, Youjun; Flury, Markus; Harsh, James B.

2005-11-28

182

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

SciTech Connect

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

Conrad Ingram; Mark Mitchell

2005-03-31

183

Crystalline Beams  

NASA Astrophysics Data System (ADS)

Crystalline Beams are ordered stale of an ensemble of ions circulating in a Storage Ring with very small velocity fluctuations. They can be obtained from ordinary warm ion beams with the application of intense cooling techniques, namely electron and/or laser cooling. A phase transition occurs when sufficiently small velocity spreads are reached, freezing the particle-to-particle spacing in strings, zig-zags, and helices... The properties and feasibility of Crystalline Beams depend on the choice of the lattice of the Storage Ring. There are three issues closely related to the design of the Storage Ring, namely: the determination of Equilibrium Configurations, Confinement Conditions, and Stability Conditions. Of particular concern is the effect of the trajectory curvature and of the beam momentum spread. They both set the requirements on the amount of momentum cooling, on the focussing, and on the distribution of bending in the lattice of the Storage Ring. The practical demonstration of Crystalline Beams may create the basis for an advanced technology of particle accelerators. The limitations due to Coulomb intra-beam scattering and space-charge forces would be finally be brought under control, so that ordered beams of ions can be achieved for a variety of new applications.

Ruggiero, Alessandro G.

2000-12-01

184

Properties of zeolite Y in various forms and utilization as catalysts or supports for cerium oxide in ethanol oxidation  

Microsoft Academic Search

Zeolite Y in sodium form (NaY) was synthesized using silica source from rice husk, transformed to ammonium form (NH4Y), and calcined to convert to proton form (HY). The direct conversion of NH4Y to HY resulted in loss of the zeolite crystallinity and lower surface area. Thus, the NH4Y was further used in the preparation of cerium (Ce) catalysts. The NH4Y

Jan-Jezreel F. Saceda; Kamolwan Rintramee; Supattra Khabuanchalad; Sanchai Prayoonpokarach; Rizalinda L. de Leon; Jatuporn Wittayakun

185

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

186

Hydrogen bonding in hydrogen-substituted lithium aluminosilicates  

NASA Astrophysics Data System (ADS)

The infrared spectra of hydrogen-substituted lithium aluminosilicates are discussed. OH stretching bands of the ABC type are observed in keatite solid solution indicating a medium strength asymmetric hydrogen bond, whereas bands due to hydroxyl groups and water are observed for the high quartz-like structure (? eucryptite). Assignments are discussed in the light of previous crystallographic investigations.

Colomban, Ph.

1992-07-01

187

Porous Zeolite: A Potential Ecomaterial.  

National Technical Information Service (NTIS)

A new method of wastewater treatment of fertilizer plant by natural zeolite was set up. In this paper the natural zeolite is pretreated in high temperature to increase the capability of removing NH4+ in wastewater. The capability can be increased more tha...

D. Z. Wang Y. Jiang Z. Chen R. Fang

1994-01-01

188

Electrorheological characterization of zeolite suspensions  

Microsoft Academic Search

The rheological properties of the electrorheological (ER) fluids prepared from commercial zeolites 3A, 5A and 13X suspended in silicone oil were investigated through steady shear and oscillatory shear experiments. Dielectric spectra of the fluids were also measured to examine their possible correlation with the flow behavior of the ER fluids. Among the zeolite ER fluids investigated, the ER fluid using

M. S. Cho; H. J. Choi; I.-J. Chin; W.-S. Ahn

1999-01-01

189

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

190

Zeolite formation from coal fly ash and its adsorption potential  

SciTech Connect

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

Duangkamol Ruen-ngam; Doungmanee Rungsuk; Ronbanchob Apiratikul; Prasert Pavasant [Chulalongkorn University, Bangkok (Thailand). Department of Chemical Engineering

2009-10-15

191

Parameters influencing zeolite incorporation in PDMS membranes  

Microsoft Academic Search

The incorporation of several types of zeolite in PDMS membranes is studied, by measuring the tensile strength, xylene sorption, and density of the membranes. The zeolite is shown to be involved in the cross-linking of the membrane. The interaction between the PDMS matrix and the zeolites results in reinforced membranes in the case of zeolite Y. The parameters influencing the

Ivo F. J. Vankelecom; Else Scheppers; Robin Heus; Jan B. Uytterhoeven

1994-01-01

192

Verified Syntheses of Zeolitic Materials  

NSDL National Science Digital Library

From the International Zeolitic Association comes this online version of the special issue of Microporous and Mesoporous Materials, Volume 22, Issues 4-6, featuring a "cookbook" of "recipes" for making zeolites. Zeolites, of which there are over 100 structure types, occur naturally in some cases, but usually are prepared synthetically. Few are available commercially so researchers wanting to test a zeolite in a new application often must attempt the synthesis of the base zeolite in the laboratory. This book is intended to assist in this endeavor, says the editor, Dr. Harry Robson of Louisiana State University. The recipes can be accessed by material name or structure type. A preface, introductory and explanatory notes, and safety information are provided. The recipes include information on source materials, batch preparation and crystallization instructions, product phase, and XRD characterization. The contributor's name, date of entry, and references accompany each recipe.

193

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

194

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

195

Oxygen and hydrogen isotope geochemistry of zeolites  

NASA Astrophysics Data System (ADS)

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.

1990-05-01

196

Statistical thermodynamics of Si,Al ordering in aluminosilicate faujasites  

Microsoft Academic Search

The Si,Al distribution on the zeolitic framework of faujasite is analyzed by a Monte Carlo method, by following a ``simulated-annealing'' procedure. Equilibrium atom distributions are obtained at the formation temperature of synthetic X and Y zeolites (TF~350 K). The heat capacity cv is calculated from the energy fluctuations in the canonical ensemble, for framework compositions in the range of 48-96

Carlos P. Herrero; Luis Utrera; Rafael Ramírez

1992-01-01

197

The adsorption of fatty acids from vegetable oils with zeolites and bleaching clay\\/zeolite blends  

Microsoft Academic Search

The adsorption of model fatty acids (hepatnoic, oleic), using spiked vegetable oils, was studied using different kinds of\\u000a zeolites (A-zeolite, X, Y-zeolites, mordenite), Y-zeolite exchanged with different cations (alkali, alkaline earth, transition\\u000a metal ions), and with bleaching clay\\/zeolite blends. The adsorption process was shown to be governed by the molecular sieving\\u000a properties of the zeolites involved as well as the

D. R. Taylor; C. B. Ungermann; Z. Demidowicz

1984-01-01

198

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

199

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 4°C. 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 12°C 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 4°C. 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

200

Poorly Crystalline, Iron-Bearing Aluminosilicates and Their Importance on Mars.  

National Technical Information Service (NTIS)

Martian rocks and sediments contain weathering products including evaporite salts and clay minerals that only form as a result of interaction between rocks and water (1-6). These weathering products are key to studying the history of water on Mars because...

D. G. Strawn D. W. Ming J. L. Bishop L. L. Baker P. A. McDaniel R. N. Nickerosn R. V. Morris

2011-01-01

201

Hydrothermal interactions of cement or mortar with zeolites or montmorillonites  

SciTech Connect

Concretes, grouts, clays and/or zeolites are candidate borehole, shaft or tunnel plugging materials for any nuclear waste repository. Interactions between these plugging materials may take place under mild hydrothermal conditions during the life of a repository. Class H cement or motar (PSU/WES mixture) was reacted with one of two montmorillonites, clinoptilolite or mordenite at 100/sup 0/ and 200/sup 0/C for different periods under a confining pressure of 30 MPa. The solid reaction products were characterized by x-ray powder diffraction and scanning electron microscopy after the hydrothermal treatments. When zeolites were in contact (not intimate mixture) with class H cement, they did not seem to alter but clinoptilolite altered to analcime, and mordenite became poorly crystalline in the presence of mortar (containing NaCl) at both 100/sup 0/ and 200/sup 0/C. When cement or mortar was intimately mixed with zeolites or montmorillonites and reacted hydrothermally, the reaction resulted in the formation of Al substituted tobermorite (11A type) in all cases (this type of reaction is expected at the interface) at both 100/sup 0/ and 200/sup 0/C. The mechanism of tobermorite formation includes the decomposition of zeolites or montmorillonites in the presence of alkaline (pH approx. = 12) cement or mortar and recrystallization to form Al substituted tobermorite. Cesium sorption measurements in 0.01N CaCl/sub 2/ on the reaction products revealed that selective Cs sorption increased in most cases, even though little or none of the original zeolites and montmorillonites remained in the products. For example, Cs sorption K/sub d/ (mL/g) increased from 80 in the untreated mortar + Ca montmorillonite mixture to 1700 in the interaction product which is Al substituted tobermorite. Thus, we discover here that Al substituted tobermorite has good selectivity for Cs.

Komarneni, S.; Roy, D.M.

1983-01-01

202

Hydrocarbon conversion catalyst and process for preparing same  

SciTech Connect

Provided is a hydrocarbon conversion catalyst comprising 3 to 40 weight percent of a crystalline aluminosilicate zeolite and 60 to 97 weight percent of an aluminamagnesia matrix having a magnesia content of 2 to 50 weight percent.

Shioiri, T.; Ino, T.

1985-05-07

203

Radiation damage of a glass-bonded zeolite waste form using ion irradiation.  

SciTech Connect

Glass-bonded zeolite is being considered as a candidate ceramic waste form for storing radioactive isotopes separated from spent nuclear fuel in the electrorefining process. To determine the stability of glass-bonded zeolite under irradiation, transmission electron microscope samples were irradiated using high energy helium, lead, and krypton. The major crystalline phase of the waste form, which retains alkaline and alkaline earth fission products, loses its long range order under both helium and krypton irradiation. The dose at which the long range crystalline structure is lost is about 0.4 dpa for helium and 0.1 dpa for krypton. Because the damage from lead is localized in such a small region of the sample, damage could not be recognized even at a peak damage of 50 dpa. Because the crystalline phase loses its long range structure due to irradiation, the effect on retention capacity needs to be further evaluated.

Allen, T. R.; Storey, B. G.

1997-12-05

204

Studies of rubidium aluminosilicates as thermionic emitters of Rb+ ions  

NASA Astrophysics Data System (ADS)

Filament sources of Rb+ ions were created using 90% Pt-10% Rh gauze coated with synthetic rubidium aluminosilicate compounds of various compositions. The performance characteristics of these compounds as thermionic emission sources of Rb+ ions based on total emission current and purity of ion emission as functions of time were studied and compared. In addition, these characteristics were investigated of [beta]-eucryptite (Rb2O·Al2O3·2SiO2) and spodumene (Rb2O·Al2O3·4SiO2) samples at four different filament surface temperatures. It was concluded that the [beta]-eucryptite composition of rubidium aluminosilicate gives the most satisfactory results as a Rb+ ion emitter at a temperature of 1100°C.

Tan, T. L.; Ong, P. P.; Fong, T. M.; Soo, K. A.

1994-06-01

205

Towards the rational design of efficient organic structure-directing agents for zeolite synthesis.  

PubMed

Zeolites are crystalline microporous materials with application in diverse fields, especially in catalysis. The ability to prepare zeolites with targeted physicochemical properties for a specific catalytic application is a matter of great interest, because it allows the efficiency of the entire chemical process to be increased (higher product yields, lower undesired by-products, less energy consumption, and cost savings, etc). Nevertheless, directing the zeolite crystallization towards the material with the desired framework topology, crystal size, or chemical composition is not an easy task, since several variables influence the nucleation and crystallization processes. The combination of accumulated knowledge, rationalization, and innovation has allowed the synthesis of unique zeolitic structures in the last few years. This is especially true in terms of the design of organic and inorganic structure-directing agents (SDAs). In this Minireview we will present the rationale we have followed in our studies to synthesize new zeolite structures, while putting this in perspective with the advances made by other researchers of the zeolite community. PMID:24115577

Moliner, Manuel; Rey, Fernando; Corma, Avelino

2013-12-23

206

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 300°C. 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 200°C 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

207

Heat-insulating radiotransparent ceramics based on aluminosilicate microspheres  

Microsoft Academic Search

The possibility of using waste of coal combustion (hollow aluminosilicate microspheres, HASM) as a material for fabricating heat-insulating radiotransparent articles and coatings is considered. The effect of binders and technological factors on the physical and thermal properties of compositions based on HASM is investigated. The technological parameters for manufacturing HASM-base heat-insulating articles with a stable low thermal conductivity and radiotransparent

L. M. Aksel'rod; Z. E. Goryacheva; N. A. Chuprina; L. Ya. Kizil'shtein; A. L. Shpitsgluz

1996-01-01

208

Thermal Shock Resistance of a Kyanite-Based (Aluminosilicate) Ceramic  

Microsoft Academic Search

This paper presents the results of a combined experimental and theoretical study of microstructure and thermal shock resistance\\u000a of an aluminosilicate ceramic. Shock-induced crack growth is studied in sintered structures produced from powders with different\\u000a particle size ranges. The underlying crack\\/microstructure interactions and toughening mechanisms are elucidated via scanning\\u000a electron microscopy (SEM). The resulting crack-tip shielding levels (due to viscoelastic

N. Rahbar; B. O. Aduda; J. Zimba; S. K. Obwoya; F. W. Nyongesa; I. Yakub; W. O. Soboyejo

2011-01-01

209

Origin of dynamical heterogeneities in calcium aluminosilicate liquids.  

PubMed

We investigate the heterogeneous dynamics of calcium aluminosilicate liquids across both the peraluminous and peralkaline regimes. Using the isoconfigurational ensemble method we find a clear correlation between dynamical heterogeneities and concentration fluctuations. Regions of high dynamic propensity have higher concentrations of both calcium and aluminum, whereas low propensity regions are silica rich. The isoconfigurational ensemble is found to be a powerful tool for studying the origin of heterogeneous dynamics of industrially relevant glass-forming liquids. PMID:20499973

Vargheese, K Deenamma; Tandia, Adama; Mauro, John C

2010-05-21

210

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

211

Mesoporous aluminosilicate ropes with improved stability from protozeolitic nanoclusters  

SciTech Connect

Mesoporous aluminosilicate ropes with improved hydrothermal stability have been prepared through S{sup +}X{sup -}I{sup +} route via self-assembly of protozeolitic nanoclusters with cetyltrimethylammonium bromides (CTAB) template micelles in HNO{sub 3} solution. SEM observation confirmed that high-yield aluminosilicate ropes could be produced under proper HNO{sub 3} concentration. NO{sub 3} {sup -} ions had strong binding strength to the CTA{sup +} ions and tended to form more elongated surfactant micelles, thus fibrous products were fabricated under the direction of these long rod micelles in shearing flow. At the same time, the NO{sub 3} {sup -} ions combining with CTA{sup +} ions generated more active (CTA{sup +}NO{sub 3} {sup -}) assembly, which effectively catalysed the polymerization of protozeolitic nanoclusters with large volume into highly ordered mesostructures. Compared with normal MCM-41 silica synthesized through S{sup +}X{sup -}I{sup +} route in acidic media, the hydrothermal stability was improved considerably. These protozeolitic nanoclusters survived strongly acidic media and entered into mesostructured framework, which contributed to the improvement of hydrothermal stability. - Graphical abstract: Mesoporous aluminosilicate ropes with enhanced hydrothermal stability were fabricated from protozeolitic nanoclusters through S{sup +}X{sup -}I{sup +} route in HNO{sub 3} solution under the direction of CTAB templates.

Zheng Junlin [Shanghai Research Institute of Petrochemical Technology, SINOPEC, Shanghai 201208 (China); State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China); Kong Dejin [Shanghai Research Institute of Petrochemical Technology, SINOPEC, Shanghai 201208 (China); Yang Weimin [Shanghai Research Institute of Petrochemical Technology, SINOPEC, Shanghai 201208 (China); Xie Zaiku [Shanghai Research Institute of Petrochemical Technology, SINOPEC, Shanghai 201208 (China); Wu Dong [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China); Sun Yuhan [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China)], E-mail: mesozheng@hotmail.com

2007-02-15

212

Development of Li+ alumino-silicate ion source  

SciTech Connect

To uniformly heat targets to electron-volt temperatures for the study of warm dense matter, one strategy is to deposit most of the ion energy at the peak of energy loss (dE/dx) with a low (E< 5 MeV) kinetic energy beam and a thin target[1]. Lower mass ions have a peak dE/dx at a lower kinetic energy. To this end, a small lithium (Li+) alumino-silicate source has been fabricated, and its emission limit has been measured. These surface ionization sources are heated to 1000-1150 C where they preferentially emit singly ionized alkali ions. Alumino-silicates sources of K+ and Cs+ have been used extensively in beam experiments, but there are additional challenges for the preparation of high-quality Li+ sources: There are tighter tolerances in preparing and sintering the alumino-silicate to the substrate to produce an emitter that gives uniform ion emission, sufficient current density and low beam emittance. We report on recent measurements ofhigh ( up to 35 mA/cm2) current density from a Li+ source. Ion species identification of possible contaminants is being verified with a Wien (E x B) filter, and via time-of-flight.

Roy, P.K.; Seidl, P.A.; Waldron, W.; Greenway, W.; Lidia, S.; Anders, A.; Kwan, J.

2009-04-21

213

Alteration of biophysical activity of pulmonary surfactant by aluminosilicate nanoparticles.  

PubMed

The influence of five different types of aluminosilicate nanoparticles (NPs) on the dynamic surface activity of model pulmonary surfactant (PS) (Survanta) was studied experimentally using oscillating bubble tensiometry. Bentonite, halloysite and montmorillonite (MM) NPs, which are used as fillers of polymer composites, were characterized regarding the size distribution, morphology and surface area. Particle doses applied in the studies were estimated based on the inhalation rate and duration, taking into account the expected aerosol concentration and deposition efficiency after penetration of NPs into the alveolar region. The results indicate that aluminosilicate NPs at concentrations in the pulmonary liquid above 0.1?mg?cm(-3) are capable of promoting alterations of the original dynamic biophysical activity of the PS. This effect is indicated by deviation of the minimum surface tension, stability index and the size of surface tension hysteresis. Such response is dependent on the type of NPs present in the system and is stronger when particle concentration increases. It is suggested that interactions between NPs and the PS must be related to the surfactant adsorption on the suspended particles, while in the case of surface-modified clay NPs the additional washout of surface-active components may be expected. It is speculated that observed changes in surface properties of the surfactant may be associated with undesired health effects following extensive inhalation of aluminosilicate NPs in the workplace. PMID:23363039

Kondej, Dorota; Sosnowski, Tomasz R

2013-02-01

214

Preparation and characterization of superparamagnetic nanocomposites of aluminosilicate\\/silica\\/magnetite  

Microsoft Academic Search

Three types of SPASMs (i.e., aluminosilicate materials incorporated with superparamagnetic particles) comprised of magnetite, silica and aluminosilicate have been successfully synthesized via three sequential steps: chemical precipitation of nano-sized Fe3O4, coating of SiO2 on Fe3O4 using an acidifying method or sol–gel route, and further surface functionalization to form aluminosilicates adopting sol–gel or aluminum substitution methods. The characteristics of the resulting

Chiung-Fen Chang; Yi-Ling Wu; Sheng-Shu Hou

2009-01-01

215

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

216

Zeolites in complex nitrogen biofertilizers  

Microsoft Academic Search

A novel technology for producing complex, ecologically safe biofertilizer, combining advantageous properties of both zeolites and nitrogen-fixing microorganisms has been developed. The resulted biofertilizer is a complex of high-activity nitrogen-fixing strain of Azotobacter chroococcum, isolated from the soil in Armenia and the local zeolite modified by the new technology considering the specific features of this microorganism. The new technology for

Anahit Chakhalyan; Gayane Avetisova; Ashot Saghiyan; Leyli Chil-Akopyan; Lusine Melkonyan; Rudolf Gevorkyan; Hakob Sargsyan; Liana Ghazarian

2008-01-01

217

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.

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

2013-01-01

218

Mesoporous zeolite single crystal catalysts: Diffusion and catalysis in hierarchical zeolites  

Microsoft Academic Search

During the last years, several new routes to produce zeolites with controlled mesoporosity have appeared. Moreover, an improved catalytic performance of the resulting mesoporous zeolites over conventional zeolites has been demonstrated in several reactions. In most cases, the mesoporous zeolites exhibit higher catalytic activity, but in some cases also improved selectivity and longer catalyst lifetime has been reported. The beneficial

Claus Hviid Christensen; Kim Johannsen; Eric Törnqvist; Iver Schmidt; Henrik Topsøe; Christina Hviid Christensen

2007-01-01

219

Crystalline molecular sieve synthesis using quaternary ammonium-functionalized organosiliconate  

US Patent & Trademark Office Database

This invention relates to a method for preparing crystalline silicates such as zeolites from a forming mixture containing quaternary ammonium-functionalized organosiliconate as a directing agent. The products prepared depend, inter alia, on reaction conditions such as temperature, crystallization time, and pH. More particularly, this invention relates to the use of a quaternary ammonium-functionalized organosiliconate in the preparation of ZSM-5, ZSM-48, ZSM-51 and the ZSM-48 composition thus prepared.

1993-03-16

220

Separation of Cesium and Strontium with Zeolites.  

National Technical Information Service (NTIS)

Basic studies of separation of cesium and strontium were made with specimens of zeolite, including the synthetic zeolites A, X and Y, synthetic mordenite, natural modernite and clinoptilolite. Ammonium chloride, which is considered to be the most suitable...

T. Kanno H. Hashimoto

1976-01-01

221

Zeolite Ammonia Removal from Catfish Pond Waters,  

National Technical Information Service (NTIS)

The research focused on developing a zeolite filtration system which will prevent toxic ammonia build-up in catfish ponds. Zeolites are ion exchangers and some natural species are capable of selectively removing ammonia from various types of water systems...

W. R. Reynolds C. W. Williford

1987-01-01

222

Mining Environmental Target Investigation: Natural Zeolites.  

National Technical Information Service (NTIS)

Information on the mining and processing of zeolites is reviewed. Composition, structure, and varieties of zeolite, including erionite (12510428), mordenite (12043742), natrolite (1318952), ferrierite (12173307), and phillipsite (12174184) are presented. ...

A. Albers

1981-01-01

223

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

224

Mechanism of Microwave Heating of Zeolite A  

Microsoft Academic Search

The mechanism of microwave heating of A zeolite was studied by comparing the heating properties, cation distributions and dielectric properties of 3A, 4A and 5A zeolites. It was easy to heat hydrated 4A zeolite to a glowing (melting) temperature by microwave (2.45 GHz) radiation from room temperature but was difficult to heat the same zeolite with little hydration. When 4A

Tatsuo Ohgushi; Sridhar Komarneni; Amar S. Bhalla

2001-01-01

225

Isomerization of alkenes during drying over zeolites  

Microsoft Academic Search

We observed that zeolite 5A, a zeolite commonly used for drying, isomerized 1-butene and 1-hexene at room temperature. The activity for 1-butene isomerization on 3A, 4A, 5A and 13X zeolites at temperatures of 300 to 565 K is reported.

David T. Lynch; Sieghard E. Wanke

1994-01-01

226

Chapter 17 Hydrocarbon processing with zeolites  

Microsoft Academic Search

This chapter on hydrocarbon processing with zeolites covers both existing and new catalytic applications of zeolites in oil refining and gas conversion. By way of introduction some structural aspects related to these industries are discussed to provide some background in which to relate the current and future developments. Further, the unique opportunities and limitations of zeolites are discussed in order

I. E. Maxwell; W. H. J. Stork

2001-01-01

227

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

228

Joining of mullite ceramics with yttrium aluminosilicate glass interlayers  

Microsoft Academic Search

Pellets of yttrium aluminosilicate glass (Y2O3:Al2O3:SiO2=30:20:50mol%) powder were used as the filler interlayers (0.4mm thick) to join two mullite substrates. The glass interlayer partially melted at joining temperature to bond the substrates and then crystallized during cooling to have better bonding strength. The results showed that joining could be performed at 1390–1420°C for 1–5h with applied pressure of 0.02MPa. After

Yung-Jen Lin; Shin-Hua Tu

2009-01-01

229

Fluorination of alumino-silicate minerals: The example of lepidolite  

Microsoft Academic Search

The effect of fluorination on silicate and alumino-silicate minerals has been investigated, in particular on the lepidolite [K(Li,Al)3 [Si3AlO10] (F,OH)2] of the mica-type. The fluorination techniques included direct F2-gas and cold radio-frequency-plasma involving c-C4F8 or O2\\/CF4 mixtures. The modifications of the surface properties have been followed mostly by XPS. Depending of the fluorination route used, either a reactive etching process

Larisa P. Demyanova; Alain Tressaud

2009-01-01

230

New nanocomposites based on layered aluminosilicate and guanidine containing polyelectrolytes  

NASA Astrophysics Data System (ADS)

The new functional nanomaterials based on layered aluminosilicate and guanidine containing polyelectrolytes combining high bactericidal activity with an increased ability to bind to heavy metals and organic pollutants were received. To prove the chemical structure of the model compounds (zwitterionic delocalized resonance structures AG/MAG and PAG/PMAG), as well as the presence of such structures in nanocomposites received on their basis and the MMT, IR, 1H NMR spectroscopy, X-ray diffraction studies and nanoindentation/sclerometry followed by scanning the surface in the area of the indentation were used.

Khashirov, Azamat A.; Zhansitov, Azamat A.; Zaikov, Genadiy E.; Khashirova, Svetlana Yu.

2014-05-01

231

Parameters influencing zeolite incorporation in PDMS membranes  

SciTech Connect

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

Vankelecom, I.F.J.; Scheppers, E.; Heus, R.; Uytterhoeven, J.B. (Katholieke Universiteit Leuven (Belgium))

1994-11-24

232

Propylene oligomerization over zeolite catalysts  

SciTech Connect

Zeolites (ZSM-5, boralites, offretite, HY, mordenite, and omega) were bonded with 20 wt% sepiolite into composite catalysts to oligomerize propylene in a fixed-bed, automated pilot unit operating at 30-50 atm under isothermal conditions. Product distributions indicate that oligomer size and structure correlates well with the zeolite pore diameter. In addition to C/sub 6/-C/sub 12/ and higher oligomers, aromatics and branched saturates are formed, indicating the presence of cracking, hydrogen and methyl transfer, isomerization, and dehydrocyclization reactions. Offretite (and HY) minimize C/sub 7/ and C/sub 8/ formation, while the boralite used has shown better oligomerization activity and product yields than either ZSM-5 or the other zeolites tested.

Hsu, J.T.; Galya, L.G.; Occelli, M.L.

1984-08-01

233

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

234

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

235

Role of selected synthesis variables in nucleation and growth of zeolite ZSM-5  

NASA Astrophysics Data System (ADS)

Important reaction variables which affect the hydrothermal synthesis of ZSM-5 zeolites are reviewed. Nucleation and growth mechanisms of these materials are strongly dependent on the nature and concentration of the Al- and Si-bearing reactants, pH, and the type of autoclave used. The resulting ZSM-5 particles exhibit specific sizes and morphologies desired for various catalytic applications: large single crystals having a Si-rich core and an Al-enriched outer surface or polycrystalline aggregates composed of small and homogeneous particles. A close control of these variables enables the formation of a submicrocrystalline material, possibly ZSM-5-like, embedded in an Al-rich aluminosilicate gel phase. The major role of OH - species in controlling the formation of stable nuclei is emphasized. The competitive interaction between various alkali and organic cations with (alumino)silicate anionic species in the initial hydrogel affects the kinetics of crystallization, the product morphology, the particle size, and the Al radial distribution. In addition to zoning, for a given synthesis, the {Si}/{Al} ratio of different crystallites increases with their particle size.

Derouane, Eric G.; Gabelica, Zelimir

1986-10-01

236

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

237

Zeolitical materials for microbiological filtrations.  

PubMed

The paper presents some aspects about synthesis of new materials called zeolites which can be utilised as filters with wide application in clinical practice in microbiology and in pharmaceutical industry. The SAPO-5, SAPO-11 and SAPO-34 zeolites were synthesised by hydrothermal crystallisation and using different mixtures. The crystallisation was carried out in teflon-lined stainless steel autoclaves at 180-195 degrees C for 1-2 days, under autogenous pressure. Filtering properties of these materials are different because their pore diameters are different. PMID:12092241

Ciobanu, O; Ciobanu, G

2001-01-01

238

Observation of muonium in zeolites  

NASA Astrophysics Data System (ADS)

Muonium has been directly detected over a range of temperatures and fields by transverse field ?SR in different zeolites: 3A, 13X, USY, ZSM-5, and S-115 (a high-silica form of ZSM-5), as well as in silica gel. The polarizations determined from data at 75 and 150 G were independent of both field and temperature. The amounts of Mu seen vary from ?20% to 40%, with a large missing fraction seen in every case, which may be partly due to slow Mu formation. There is also a fast Mu relaxation rate seen in all samples. This is the first direct observation of Mu in zeolites.

Arseneau, D. J.; Fleming, D. G.; Fyfe, C. A.; Senba, M.

2003-02-01

239

Fundamentals and applications of pervaporation through zeolite membranes  

Microsoft Academic Search

Zeolite membranes have uniform, molecular-sized pores, and they separate molecules based on differences in the molecules’ adsorption and diffusion properties. Zeolite membranes are thus well suited for separating liquid-phase mixtures by pervaporation, and the first commercial application of zeolite membranes has been for dehydrating organic compounds. Because of the large number of zeolites that can be prepared, zeolite membranes have

Travis C. Bowen; Richard D. Noble; John L. Falconer

2004-01-01

240

Application of Synthetic Zeolites (molecular Sieves) to Catalysis  

Microsoft Academic Search

CONTENTS I. Introduction 904 II. General information on zeolites, and on some of their physicochemical properties 904 III. Preparation of zeolite catalysts 905 IV. Applications of zeolite catalysts 906 V. Selectivity of zeolite catalysts 911 VI. Operating mechanism of zeolite catalysts 912

Khabib M. Minachev; V. I. Garanin; Ya I. Isakov

1966-01-01

241

Nitride formation by the carbothermal reduction of a zeolite-polyacrylonitrile inclusion compound  

Microsoft Academic Search

An inclusion compound between zeolite and polyacrylonitrile has been applied as a precursor for the carbothermal reduction process. By heat treatment at 1400 to 1600° C in N2, ß-sialon was mainly obtained. The X phase, a-Si3N4, the 15R-AlN phase, AIN, and mullite also formed under certain firing conditions. On the other hand, a-Si2N4 was detected as the principal crystalline phases

Yoshiyuki Sugahara; Hiromitsu Hiraiwa; Kazuyuki Kuroda; Chuzo Kato

1988-01-01

242

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...

243

Tailored zeolites for the removal of metal oxyanions: overcoming intrinsic limitations of zeolites.  

PubMed

This review aims to present a global view of the efforts conducted to convert zeolites into efficient supports for the removal of heavy metal oxyanions. Despite lacking affinity for these species, due to inherent charge repulsion between zeolite framework and anionic species, zeolites have still received considerable attention from the scientific community, since their versatility allowed tailoring them to answer specific requirements. Different processes for the removal and recovery of toxic metals based on zeolites have been presented. These processes resort to modification of the zeolite surface to allow direct adsorption of oxyanions, or by combination with reducing agents for oxyanions that allow ion-exchange with the converted species by the zeolite itself. In order to testify zeolite versatility, as well as covering the wide array of physicochemical constraints that oxyanions offer, chromium and arsenic oxyanions were selected as model compounds for a review of treatment/remediation strategies, based on zeolite modification. PMID:24794984

Figueiredo, Hugo; Quintelas, Cristina

2014-06-15

244

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

245

SODIUM ALUMINOSILICATE FOULING AND CLEANING OF DECONTAMINATED SALT SOLUTION COALESCERS  

SciTech Connect

During initial non-radioactive operations at the Modular Caustic Side Solvent Extraction Unit (MCU), the pressure drop across the decontaminated salt solution coalescer reached {approx}10 psi while processing {approx}1250 gallons of salt solution, indicating possible fouling or plugging of the coalescer. An analysis of the feed solution and the 'plugged coalescer' concluded that the plugging was due to sodium aluminosilicate solids. MCU personnel requested Savannah River National Laboratory (SRNL) to investigate the formation of the sodium aluminosilicate solids (NAS) and the impact of the solids on the decontaminated salt solution coalescer. Researchers performed developmental testing of the cleaning protocols with a bench-scale coalescer container 1-inch long segments of a new coalescer element fouled using simulant solution. In addition, the authors obtained a 'plugged' Decontaminated Salt Solution coalescer from non-radioactive testing in the MCU and cleaned it according to the proposed cleaning procedure. Conclusions from this testing include the following: (1) Testing with the bench-scale coalescer showed an increase in pressure drop from solid particles, but the increase was not as large as observed at MCU. (2) Cleaning the bench-scale coalescer with nitric acid reduced the pressure drop and removed a large amount of solid particles (11 g of bayerite if all aluminum is present in that form or 23 g of sodium aluminosilicate if all silicon is present in that form). (3) Based on analysis of the cleaning solutions from bench-scale test, the 'dirt capacity' of a 40 inch coalescer for the NAS solids tested is calculated as 450-950 grams. (4) Cleaning the full-scale coalescer with nitric acid reduced the pressure drop and removed a large amount of solid particles (60 g of aluminum and 5 g of silicon). (5) Piping holdup in the full-scale coalescer system caused the pH to differ from the target value. Comparable hold-up in the facility could lead to less effective cleaning and precipitation of bayerite solid particles. (6) Based on analysis of the cleaning solutions from the full-scale test, the 'dirt capacity' of a 40 inch coalescer for these NAS solids was calculated to be 40-170 grams.

Poirier, M; Thomas Peters, T; Fernando Fondeur, F; Samuel Fink, S

2008-10-28

246

Selective laser densification of lithium aluminosilicate glass ceramic tapes  

NASA Astrophysics Data System (ADS)

Tapes, cast by blade deposition of a lithium aluminosilicate glass slurry, were sintered using a YAG-fiber laser, with the aim of finding suitable parameters for an additive manufacturing process based on layer-wise slurry deposition and selective laser densification. The influence of the laser parameters (output power and scan velocity) on the sintering was evaluated, by scanning electron microscopy and by X-ray diffraction, on the basis of the quality of the processed layer. Well densified samples could be obtained only in a small window of values for the output power and the scan velocity. The measurement of the width of a set of single scanned lines allowed also to estimate the minimum resolution of the system along the layer plane.

Zocca, Andrea; Colombo, Paolo; Günster, Jens; Mühler, Thomas; Heinrich, Jürgen G.

2013-01-01

247

Holographic Image Storage in Eu 3 +-Doped Alkali Aluminosilicate Glasses  

NASA Astrophysics Data System (ADS)

We demonstrate that holographic information can be stored in Eu3 +-doped alkali aluminosilicate glasses. The holograms were developed by a two-beam mixing configuration with a write-beam wavelength (465.8 nm) corresponding to the7F0 5D0 transition of the Eu3 + ions. The images were reconstructed either with the wavelength used to record them or with wavelengths below this transition (543.5 and 632.8 nm). We stored clear holographic images using a total writing power of 5 mW and an exposure time of 20 s. In addition, clear holograms were recorded with an exposure time of 200 ms when 100 mW of the writing power was used. The exposure time and the writing power required to obtain clear holographic images are dependent on the Eu3 +concentration.

Hamad, Abdulatif Y.; Wicksted, James P.

2001-04-01

248

Surface enrichment of aluminosilicate minerals and coal combustion ash particles  

NASA Astrophysics Data System (ADS)

Auger electron spectroscopy has been used to provide evidence of surface segregation in illite, an aluminosilicate mineral representative of those which produce coal combustion ash particles. For the temperature range of 150-1100°C., the segregation of Fe, K, Ca and S has been observed, and the temperature dependence of the segregation levels of these elements has been determined. A comparison of these results with the reported data for surface enrichment of coal combustion ash particles indicates that the segregation levels of Fe, K, Ca and S in heated illite are comparable to the levels observed for the ash particles. Order-of-magnitude calculations indicate that appreciable segregation may occur on a time scale compatible with the residence time of ash particles in the combustor. These results are particularly significant because the surface enrichment of coal combustion ash has been generally attributed solely to adsorption/condensation processes.

Stinespring, C. D.; Stewart, G. W.

249

Spin probes of chemistry in zeolites  

SciTech Connect

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

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

1997-09-01

250

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

251

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

252

Luminescent properties of Tb3+ and Gd3+ ions doped aluminosilicate oxyfluoride glasses.  

PubMed

Tb(3+) and Gd(3+) ions doped lithium-barium-aluminosilicate oxyfluoride glasses have been prepared. The transmission, emission and excitation spectra were measured. It has been found that those Tb(3+)-doped lithium-barium-aluminosilicate oxyfluoride glasses exhibit good UV-excited luminescence. The luminescence intensity of Tb(3+) ion increases for those (Tb(3+), Gd(3+))-codoped glasses. Energy transfer process from Gd(3+) ion to Tb(3+) ion is indicated. PMID:21831699

Zuo, Chenggang; Lu, Anxian; Zhu, Ligang; Zhou, Zhihua; Long, Woyun

2011-11-01

253

S{sup +}X{sup -}I{sup +} route to mesostructured materials from Fau and Beta zeolite precursors: A comparative study of their assembly behaviors in extremely acidic media  

SciTech Connect

Mesoporous molecular sieves were synthesized from Beta and Fau zeolite precursors through S{sup +}X{sup -}I{sup +} route under extremely acidic conditions in parallel (designated as M{sub Beta} and M{sub Fau}, respectively). The textural properties of M{sub Fau} were different from its M{sub Beta} counterpart but resembled normal MCM-41 silica from TEOS. Al content in M{sub Beta} was almost equivalent to that in the initial Beta zeolite precursors, whereas only trace Al species was present in M{sub Fau} from elemental analysis results. The hydrothermal stability of M{sub Beta} after post-synthesis ammonia treatment was considerably improved compared with normal MCM-41 aluminosilicates, whereas the M{sub Fau} after the same procedure was as unstable as normal MCM-41 silica. Thus, the assembly behaviors of Beta and Fau zeolite precursors were comparatively studied based on these results. The microstructure of Fau zeolite precursors were degraded by the extremely acidic condition, and Al species was dissolved into the synthesis mixture. However, Beta zeolite precursors survived the chemical attack of extremely acidic media and were incorporated into mesostructured framework as primary building units.

Zheng Junlin [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, P.O. Box 165, Taiyuan 030001 (China)]. E-mail: mesozheng@hotmail.com; Zhai Shangru [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, P.O. Box 165, Taiyuan 030001 (China); Wu Dong [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, P.O. Box 165, Taiyuan 030001 (China); Sun Yuhan [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, P.O. Box 165, Taiyuan 030001 (China)

2005-05-15

254

Observation of muonium in zeolites  

Microsoft Academic Search

Muonium has been directly detected over a range of temperatures and fields by transverse field muSR in different zeolites: 3A, 13X, USY, ZSM-5, and S-115 (a high-silica form of ZSM-5), as well as in silica gel. The polarizations determined from data at 75 and 150 G were independent of both field and temperature. The amounts of Mu seen vary from

D. J. Arseneau; D. G. Fleming; C. A. Fyfe; M. Senba

2003-01-01

255

Observation of muonium in zeolites  

Microsoft Academic Search

Muonium has been directly detected over a range of temperatures and fields by transverse field ?SR in different zeolites: 3A, 13X, USY, ZSM-5, and S-115 (a high-silica form of ZSM-5), as well as in silica gel. The polarizations determined from data at 75 and 150 G were independent of both field and temperature. The amounts of Mu seen vary from

D. J. Arseneau; D. G. Fleming; C. A. Fyfe; M. Senba

2003-01-01

256

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

257

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

258

An Electron Microprobe Study of Synthetic Aluminosilicate Garnets  

NASA Astrophysics Data System (ADS)

The aluminosilicate garnets represent an important mineral group. Common end-members are given by E3Al2Si3O12, where E=Fe2+ (almandine), Mn2+ (spessartine), Mg (pyrope), and Ca (grossular). End-members have been synthesized, but their exact compositions and stoichiometries are generally unknown. Synthetic aluminosilicate garnet can possibly contain minor Fe3+, Mn3+, F- and OH- and possibly vacancies. Slight atomic disorder over the 3 different cation sites may also occur. Natural crystals are considerably more complex. Electron probe microanalysis (EPMA) provides a method to determine garnet chemistry and stoichiometry. However, accurate determinations are not always a simple matter and uncertainties exist. We have started a study on well-characterized synthetic aluminosilicate garnets in order to i) determine more exactly their compositions and stoichiometries and ii) better understand possible complications in EPMA. Synthetic almandine, spessartine, pyrope, and grossular samples were synthesized under varying conditions both hydrothermally and dry and with different starting materials. A closed thermodynamic system was present and the bulk starting material composition represented the exact stoichiometric end-member garnet that was desired. IR, Raman and Mössbauer spectroscopy in some cases and X-ray diffraction were used to characterize the samples. Synthetic pyrope has been investigated with a SX51 with simple oxide/silicate standards (Fo90 olivine for Mg, wollastonite for Si, and both Al2O3 and kyanite for Al). Previously observed problems were reproduced: low stoichiometry for Al and high for Si and Mg. Fournelle (2007, AGU Fall Mtg) noted chemical peak shifts for Al and Mg Ka in garnets; this effect was eliminated here by proper peaking. Earlier suggestions for issues with mass absorption coefficients were not seen, and Probe for EPMA software demonstrated there was not much difference between the most recent FFAST values vs. the older Heinrich values. Similarly, a matrix correction based on CITZAF was compared with PAP, with little difference in Al (both low) and Mg values (both high), though PAP had higher Si values and CITZAF had lower ones. An assumption in EPMA is that the intensity of a single peak channel is representative of the integral of all x-ray counts under the total peak. It is known that this is not true for “light elements” (Be-F). We performed detailed wavescans of the complete peaks of Si, Al and Mg Ka of both standards and pyrope. Mg and Si peak scans showed little or no difference between pyrope and standard, but the Al scans had reproducible differences of 3% between the Al2O3 standard and unknown. This yielded an “area peak factor” correction of 1.03, which brings the Mg closer, but not all the way, to a stoichiometry of 2, Si to almost 3, and Mg closer to 3 but still too high. One possibility to be evaluated is whether there may be solid solution between pyrope and a minor majorite (Mg3(Mg,Si)Si3O12) component involving coupled substitution 2Al = Mg,Si at the octahedral site. In summary: Is this an EPMA analytical issue (peak fine structure differences), or an issue regarding a small amount of an unforseen component (majorite) in the garnet?

Fournelle, J.; Geiger, C. A.

2010-12-01

259

Synthesis, characterization, and application of novel microporous mixed metal oxides, and nanostructured layered material-polymer films  

Microsoft Academic Search

Zeolites are microporous crystalline aluminosilicates with pores and cavities of molecular dimension. They consist of interconnected aluminum and silicon tetrahedra to build a variety of 3D open framework structures. Due to their structure, stability, and activity, zeolites have been widely used in a broad variety of applications in industry. It is, therefore, of great interest to make new structures with

Hae-Kwon Jeong

2004-01-01

260

Mixing of zeolite powders and molten salt.  

National Technical Information Service (NTIS)

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 dis...

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

1996-01-01

261

Chemical interactions in multimetal\\/zeolite catalysts  

Microsoft Academic Search

Mechanistic explanations have been found for the migration of atoms and ions through the zeolite channels leading to specific distribution of ions and the metal clusters. In this report, we summarize the state of understanding attained on a number of topics in the area of mono- and multimetal\\/zeolite systems, to which our recent research has made significant contributions. The following

Sachtler; W. M. H

1992-01-01

262

Fly Ash Zeolites as Sulfur Dioxide Adsorbents  

Microsoft Academic Search

Air protection technologies generate massive amounts of solid wastes, including fly ash (FA). Zeolite synthesis from FA seems to be an effective method for FA utilization. In addition, fly ash zeolites (FAZs) could be used for sulfur dioxide (SO2) adsorption. Since there is a lack of sufficient information about SO2 uptake on FAZs, we investigated this phenomenon in detail. Two

T. T. Suchecki; T. Wa?ek; M. Banasik

263

Metal/zeolite catalysts of methane dehydroaromatization  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

264

[Morphology of pneumoconiosis induced by natural zeolite].  

PubMed

Pneumoconiosis was induced in white rats through intratracheal administration of natural zeolite. It was characterized by intensive phagocytosis of the specks of dust, moderate cytotoxic action on the macrophages, as well as inflammatory processes in the vascular system and alveolar epithelium. Zeolite induced fibrosis did not develop to the extent as in case with quartz induced massive collagen formation. PMID:2165972

Kruglikov, G G; Velichkovski?, B T; Garmash, T I

1990-01-01

265

Ion exchange equilibria in zeolite minerals  

Microsoft Academic Search

Cation exchange equilibria of the most common sedimentary zeolites are reviewed. Selected exchange isotherms and thermodynamic equilibrium constants are reported and interpreted in terms of selectivity of one cation over another. Selectivity sequences of various zeolites are compared with each other in the light of Eisenman's theory and utilized to predict or explain specific practical performances.

C. Colella; Napoli Federico; Piazzale V. Tecchio

1996-01-01

266

Octane-enhancing zeolitic FCC catalysts  

Microsoft Academic Search

While particular aspects of octane- enhancing catalysts and zeolites are often described in detail in different articles and patents, this book provides a comprehensive, unified view of this topic. The author has organized the wealth of disparate data and information from the literature by the frequent use of classifications. For example, high-silica Y zeolites were classified according to their preparation

Scherzer

1990-01-01

267

Synthesis of crystalline polyaniline  

SciTech Connect

The synthesis of crystalline polyaniline base using a water-in-oil type microemulsion as a medium of polymerization is reported. The polymer exhibits well defined crystalline phase whose observed orthorhombic lattice parameters are a = 7.65, b = 5.75, c = 10.22{angstrom} and V = 450{angstrom}{sup 3}. The polymer obtained has been characterized by XRD, FTIR, UV and Cyclic Voltammetry (CV) confirming the crystalline phase, surfactant stabilized nature, base form and dopability.

Selvan, S.T.; Mani, A.; Athinarayanasamy, K.; Phani, K.L.N.; Pitchumani, S. [Central Electrochemical Research Inst., Karaikudi (India)] [Central Electrochemical Research Inst., Karaikudi (India)

1995-06-01

268

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

269

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

SciTech Connect

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

Ohsuna, Tetsu; Watanabe, Denjiro [Iwaki Meisei Univ., Fukushima (Japan); Terasaki, Osamu [Tohoku Univ., Sendai (Japan); Anderson, M.W. [UMIST, Manchester (United Kingdom); Carr, S.W. [Unilever Research, Merseyside (United Kingdom)

1994-12-01

270

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, Bjørnar; Dynes, James J; Wang, Jian; Weckhuysen, Bert M

2014-02-01

271

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...

272

Silver supported on natural Mexican zeolite as an antibacterial material  

Microsoft Academic Search

The antimicrobial effect of the Mexican zeolitic mineral from Taxco, Guerrero exchanged with silver ions was investigated. The zeolitic mineral as well as sodium and silver zeolitic minerals were characterized by using X-ray diffraction, electron microscopy and IR spectroscopy techniques. The elementary composition of the zeolitic mineral was determined by atomic absorption and microanalyses (EDAX). Escherichia coli and Streptococcus faecalis

M Rivera-Garza; M. T Olgu??n; I Garc??a-Sosa; D Alcántara; G Rodr??guez-Fuentes

2000-01-01

273

What Is Crystalline Silica?  

MedlinePLUS

... loss, which often leads to death. Where are construction workers exposed to crystalline silica? Exposure occurs during many different construction activities. The most severe exposures generally occur during ...

274

Insulator-to-metal transition and magnetism of potassium metals loaded into regular cages of zeolite LSX  

NASA Astrophysics Data System (ADS)

Zeolite LSX (low-silica X) crystals have an aluminosilicate framework with regular supercages and ?-cages. They are arrayed in a double diamond structure. The loading density of guest K atoms per supercage (or ? cage), n, can be controlled from 0 to ? 9. At n < 2, samples are nearly nonmagnetic and insulating. The Curie constant has a clear peak at n = 3, and the electrical resistivity suddenly decreases simultaneously. The electrical resistivity suddenly decreases again at n = 6 and shows metallic phase at n > 6. These properties are explained by the polaron effect including the electron correlation. Ferrimagnetic properties are observed at n ? 9. A remarkable increase in the resistivity is observed at very low temperatures at n ? 9, and is discussed in terms of the hypothesis of a Kondo insulator.

Nakano, Takehito; Thi Hanh, Duong; Owaki, Akihiro; Nozue, Yasuo; Nam, Nguyen Hoang; Araki, Shingo

2013-08-01

275

Preliminary study on calcium aluminosilicate glass as a potential host matrix for radioactive 90Sr--an approach based on natural analogue study.  

PubMed

Given the environmental-, safety- and security risks associated with sealed radioactive sources it is important to identify suitable host matrices for (90)Sr that is used for various peaceful applications. As SrO promotes phase separation within borosilicate melt, aluminosilicate bulk compositions belonging to anorthite-wollastonite-gehlenite stability field are studied in this work. Tests for their homogeneity, microstructural characteristics and resistance to phase separation narrowed the choice down to the composition CAS11 (CaO=35 wt%, Al(2)O(3)=20 wt%, SiO(2)=45 wt%). We find that up to 30 wt% SrO can be loaded in this glass without phase separation (into Ca, Sr-rich and Sr-poor, Si-rich domains). Leaching behaviour of the glasses differs depending on the content and distribution of Sr. In general, the elemental leach rates determined from conventional PCT experimental procedure yield values better than 10(-7)gcm(-2)day(-1) for both CAS11 base glass as well as SrO doped glass. It was noted that leach rates calculated on the basis of Ca(2+) and Sr(2+) were of the same order and bit higher compared to those calculated on the basis of Si(4+) and Al(3+). During accelerated leaching tests, zeolite and zeolite+epidote were found to have developed on CAS11 base glass and SrO doped glasses respectively. The Sr bulk diffusion coefficients is found to vary from ? 10(-15) to 10(-13)cm(2)/s at temperature intervals as high as 725-850°C. Based on the experimental observations, it is suggested that CAS11 glass can be used as host matrix of (90)Sr for various applications of radioactive Sr-pencils. PMID:21477923

Sengupta, Pranesh; Fanara, Sara; Chakraborty, Sumit

2011-06-15

276

Coating crystalline nuclear waste forms to improve inertness  

SciTech Connect

Crystalline waste forms of high simulated waste loading were successfully coated with layers of pyrolytic carbon and silicon carbide. Sol-gel technology was used to produce microspheres that contained simulated waste. A separate process for cesium immobilization was developed, which loads 5 wt % Cs onto zeolite particles for subsequent coating. The chemical vapor deposition process was developed for depositing thin layers of carbon and silicon carbide onto particles in a fluidized-bed coater. Pyrolytic carbon-coated particles were extremely inert in numerous leach tests. Aqueous leach test results of coated waste forms were below detection limits of such sensitive analytical techniques as atomic absorption and inductively coupled plasma atomic emission.

Stinton, D.P.; Angelini, P.; Caputo, A.J.; Lackey, W.J.

1981-01-01

277

Coating of crystalline nuclear waste forms to improve inertness  

SciTech Connect

Microspheres of a crystalline waste form prepared by sol-gel processing were successfully coated with layers of pyrolytic carbon and silicon carbide to isolate the radioactive wastes from the biosphere. A separate process for cesium immobilization was developed, which loads 5 wt% Cs onto zeolite particles for subsequent coating. Pyrolytic carbon-coated particles showed leach rates approx. =2 to 4 orders of magnitude less than the candidate reference borosilicate glass waste form. Aqueous leach-test results of coated waste forms were below detection limits of such sensitive analytical techniques as atomic absorption and inductively coupled plasma atomic emission.

Stinton, D.P.; Angelini, P.; Caputo, A.J.; Lackey, W.J.

1982-08-01

278

SODIUM ALUMINOSILICATE SOLIDS AFFINITY FOR CESIUM AND ACTINIDES  

SciTech Connect

Washed sodium-aluminosilicate (NAS) solids at initial concentrations of 3.55 and 5.4 g/L sorb or uptake virtually no cesium over 288 hours, nor do any NAS solids generated during that time. These concentrations of solids are believed to conservatively bound current and near-term operations. Hence, the NAS solids should not have affected measurements of the cesium during the mass transfer tests and there is minimal risk of accumulating cesium during routine operations (and hence posing a gamma radiation exposure risk in maintenance). With respect to actinide uptake, it appears that NAS solids sorb minimal quantities of uranium - up to 58 mg U per kg NAS solid. The behavior with plutonium is less well understood. Additional study may be needed for radioactive operations relative to plutonium or other fissile component sorption or trapping by the solids. We recommend this testing be incorporated in the planned tests using samples from Tank 25F and Tank 49H to extend the duration to bound expected inventory time for solution.

Peters, T; Bill Wilmarth, B; Samuel Fink, S

2007-07-31

279

Surface functionalization of aluminosilicate nanotubes with organic molecules.  

PubMed

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; Takahara, Atsushi

2012-01-01

280

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

281

A new SiC-whisker-reinforced lithium aluminosilicate composite  

SciTech Connect

The glass-ceramic matrix of the well-known lithium aluminosilicate (LAS)/SiC composite is usually formulated near the spodumene composition. The authors report a new composition which is rich in alumina and lean in silica and lithia. This formulation offers a new option of converting the glass-ceramic matrix to a mullite/alumina matrix upon annealing above 1,400 C, and hence better creep resistance and other high-temperature mechanical properties. Using a transient-phase processing method that they developed previously for the superplastic forming of mullite, the authors are able to hot-press a composite containing 30 vol% SiC whiskers at [approximately]1,350 C to achieve full density. Flexural strength measurements up to 1,400 C have confirmed the improved high-temperature strength and creep resistance over conventional LAS. The fracture toughness is also higher than that of LAS. The results suggest that the new composition may be chosen as a better candidate matrix for SiC-fiber-reinforced composites.

Xue, L.A.; Chen, Iwei (Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Materials Science and Engineering)

1993-11-01

282

An ESCA study of rhodium(III)-exchanged zeolite catalysts  

SciTech Connect

An ESCA study of rhodium(III)-exchanged zeolite catalysts which are active in hydrogenation and other reactions, showed that activation at 300/sup 0/C and 0.002 mm Hg reduced rhodium(III) in Y zeolite to metallic rhodium but did not affect rhodium(III) in A zeolite. This reduction occurred under milder conditions than known for other metal ions in zeolites, and the reduced species is probably the active catalyst in rhodium-exchanged zeolite.

Kuznicki, S.M.; Eyring, E.M.

1980-09-01

283

Liquid crystalline cellulose derivatives  

SciTech Connect

Following the observation that (hydroxypropyl)cellulose in water forms an ordered cholesteric liquid crystalline phase at high polymer concentrations, reports that many other cellulose derivatives in a wide variety of solvents also form liquid crystalline solutions have appeared in the scientific and patent literature. A tabulation of cellulose-based liquid crystalline systems is presented. The formation of the ordered phase is attributed to the limited flexibility of the cellulose chain. However, some cellulose derivatives form liquid crystalline phases only in specific solvents; concentrated solutions in other solvents remain isotropic. Other cellulose derivatives, such as (hydroxypropyl)cellulose, appear to form liquid crystalline solutions in any solvent that dissolves sufficiently high concentrations of the polymer. It has been suggested that the role of flexible side-chain substituents is to allow the main chains to achieve their equilibrium orientational order. The presence of many large substituents on the cellulose backbone also increases the effective chain radius and may change the chain conformation. The effect of side-chain structure on the properties of cellulose liquid crystalline phases is thus of interest. A series of esters of (hydroxypropyl)cellulose have been prepared. In addition to forming liquid crystalline solutions in organic solvents, these materials also were found to form cholesteric thermotropic phases in the absence of solvent. The thermotropic phases show spontaneous molecular orientation and cholesteric reflection. On heating, a transformation to the isotropic melt occurs. The liquid crystalline state of cellulose and its derivatives is thus widely observed. 42 references, 4 figures, 3 tables.

Gray, D.G.

1983-01-01

284

Nanocrystalline zeolite beta and zeolite Y as catalysts in used palm oil cracking for the production of biofuel  

Microsoft Academic Search

Nanocrystalline zeolites with crystal size smaller than 100 nm are potential replacement for conventional zeolite catalysts\\u000a due to their unique characteristics and advantages. In this study, the synthesis of nanocrystalline zeolite Y (FAU) and nanocrystalline\\u000a zeolite beta (BEA) under hydrothermal conditions is reported. The effect of crystal size on the physico-chemical characteristics\\u000a of the zeolite, Y (FAU), and beta (BEA) is

Niken Taufiqurrahmi; Abdul Rahman Mohamed; Subhash Bhatia

285

Novel aluminosilicate hollow sphere as a catalyst support for methane decomposition to COx-free hydrogen production  

NASA Astrophysics Data System (ADS)

Novel Ni and Co supported on aluminosilicate hollow sphere catalysts were investigated to decompose methane into CO and CO2 free hydrogen and carbon nanotube. The hollow sphere structure was prepared by reverse microemulsion method and then Ni and Co were loaded by the impregnation method. The fresh catalysts and deposited carbon were characterized by several microscopic and spectroscopic techniques. The catalytic results showed that the Co based catalyst exhibited higher activity and durability at longer reaction time, due to the higher number and distribution of metal sites. The hollow sphere structure of the support could protect the metal particles against aggregation during the catalytic reactions. Accordingly, higher metal dispersion, stabilization and catalytic performance were achieved. The formation of nickel silicate is the main reason for the lower decomposition activity of Ni based catalyst at longer reaction time. TEM and Raman spectroscopic data revealed that the Co-based catalyst produced a relatively uniform diameter of MWCNTs with higher crystallinity and graphitization degree compared to the Ni-based catalyst.

Awadallah, A. E.; Ahmed, W.; El-Din, M. R. Noor; Aboul-Enein, A. A.

2013-12-01

286

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

287

Cracking Activity of Zeolite Y Catalysts Synthesized from a South African Kaolinite.  

National Technical Information Service (NTIS)

Rare earth cation exchanged zeolite Y catalysts, rare earth acidic exchanged zeolite Y catalysts, and ultrastable zeolite Y catalysts with or without exchanged rare earth cations were prepared from ceramic microspheres which contained 24% NaY zeolites. A ...

M. G. Howden

1981-01-01

288

Molecular-sieving effect of zeolite 3A on adsorption of H 2, HD and D 2  

Microsoft Academic Search

Synthetic zeolite 3A has the molecular-sieving windows of nominal diameter 0.3nm in its crystal lattice framework, which obstruct the crystalline adsorption of molecules of diameter larger than 0.3nm, except water, hydrogen and helium. The window's diameter slightly varies with temperature, however, that is endorsed in experimental results that hydrogen cannot be adsorbed at the liquid-nitrogen temperature. Authors measured the range

K. Kotoh; S. Takashima; Y. Nakamura

2009-01-01

289

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

290

Pulsed laser deposition of zeolitic membranes  

SciTech Connect

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

Peachey, N.M.; Dye, R.C. [Los Alamos National Lab., NM (United States); Ries, P.D. [Dow Chemical Co., Midland, MI (United States)

1995-02-01

291

Role of structural similarity between starting zeolite and product zeolite in the interzeolite conversion process.  

PubMed

GIS- and LTL- (the three capital characters indicate the framework type-code) type zeolites were obtained by organic structure-directing agent free hydrothermal conversion of FAU-type zeolite at 125 degrees C in the presence of NaOH and KOH, respectively. MOR-type zeolite was found coexisting with GIS-type when the hydrothermal conversion with NaOH was carried out at 140 degrees C. There was a common building unit consisting of four-membered ring chain such as d6r, dsc, and dcc (the three characters indicate the composite building unit-code) units present in both the starting zeolite (FAU-type zeolite) and the product zeolites (GIS- and LTL-type zeolites), which was the crucial factor for crystal growth through interzeolite conversion. In the case of severe hydrothermal synthesis conditions such as high temperature, however, the crystallization behavior was similar to that observed in conventional hydrothermal synthesis using amorphous materials because the starting zeolite was excessively decomposed. The hypothesis was confirmed by successful interzeolite conversion of *BEA- to MFI-type zeolite which shared the common composite building unit mor. PMID:23763196

Honda, Koutaro; Itakura, Masaya; Matsuura, Yumiko; Onda, Ayumu; Ide, Yusuke; Sadakane, Masahiro; Sano, Tsuneji

2013-04-01

292

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

293

Li{sup +} alumino-silicate ion source development for the neutralized drift compression experiment  

SciTech Connect

We report results on lithium alumino-silicate ion source development in preparation for warm dense matter heating experiments on the new neutralized drift compression experiment II. The practical limit to the current density for a lithium alumino-silicate source is determined by the maximum operating temperature that the ion source can withstand before running into problems of heat transfer, melting of the alumino-silicate material, and emission lifetime. Using small prototype emitters, at a temperature of {approx_equal}1275 deg. C, a space-charge limited Li{sup +} beam current density of J {approx_equal}1 mA/cm{sup 2} was obtained. The lifetime of the ion source was {approx_equal}50 h while pulsing at a rate of 0.033 Hz with a pulse duration of 5-6 {mu}s.

Roy, Prabir K.; Greenway, Wayne G.; Kwan, Joe W.; Seidl, Peter A.; Waldron, William L.; Wu, James K. [Lawrence Berkeley National Laboratory (LBNL), One Cyclotron Road, Berkeley, California 94720 (United States)

2011-01-15

294

Liquid Crystalline Polymers.  

National Technical Information Service (NTIS)

The remarkable mechanical properties and thermal stability of fibers fabricated from liquid crystalline polymers (LCPs) have led to the use of these materials in structural applications where weight savings are critical. Advances in processing of LCPs cou...

1990-01-01

295

Crystalline color superconductivity  

SciTech Connect

In any context in which color superconductivity arises in nature, it is likely to involve pairing between species of quarks with differing chemical potentials. For suitable values of the differences between chemical potentials, Cooper pairs with nonzero total momentum are favored, as was first realized by Larkin, Ovchinnikov, Fulde, and Ferrell (LOFF). Condensates of this sort spontaneously break translational and rotational invariance, leading to gaps which vary periodically in a crystalline pattern. Unlike the original LOFF state, these crystalline quark matter condensates include both spin-zero and spin-one Cooper pairs. We explore the range of parameters for which crystalline color superconductivity arises in the QCD phase diagram. If in some shell within the quark matter core of a neutron star (or within a strange quark star) the quark number densities are such that crystalline color superconductivity arises, rotational vortices may be pinned in this shell, making it a locus for glitch phenomena.

Alford, Mark; Bowers, Jeffrey A.; Rajagopal, Krishna

2001-04-01

296

Factors affecting drug adsorption on beta zeolites.  

PubMed

The adsorption behaviour of three commonly used drugs, namely ketoprofen, hydrochlorothiazide and atenolol, from diluted aqueous solutions on beta zeolites with different SiO2/Al2O3 ratio (i.e. 25, 38 and 360) was investigated by changing the ionic strength and the pH, before and after thermal treatment of the adsorbents. The selective adsorption of drugs was confirmed by thermogravimetry and X-ray diffraction. The adsorption capacity of beta zeolites was strongly dependent on both the solution pH and the alumina content of the adsorbent. Such a remarkable difference was interpreted as a function of the interactions between drug molecules and zeolite surface functional groups. Atenolol was readily adsorbed on the less hydrophobic zeolite, under pH conditions in which electrostatic interactions were predominant. On the other hand, ketoprofen adsorption was mainly driven by hydrophobic interactions. For undissociated molecules the adsorption capability increased with the increase of hydrophobicity. PMID:23436460

Pasti, Luisa; Sarti, Elena; Cavazzini, Alberto; Marchetti, Nicola; Dondi, Francesco; Martucci, Annalisa

2013-05-01

297

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

298

Crystalline Raman Lasers  

Microsoft Academic Search

In this paper, we review the developments of crystalline Raman lasers over the past five years. Average powers exceeding 5 W and pulse energies above 1 J in the near infrared have been demonstrated for larger scale devices. There has been a rapid development of all-solid-state sources based on the standard diode-pumped lasers, especially intracavity crystalline Raman lasers, which offer

James A. Piper; Helen M. Pask

2007-01-01

299

Terbium-activated lithium–lanthanum–aluminosilicate oxyfluoride scintillating glass and glass-ceramic  

Microsoft Academic Search

Terbium-activated lithium–lanthanum–aluminosilicate oxyfluoride scintillating glasses, 55SiO2·6Al2O3·28Li2O·11LaF3 doped with different TbF3 concentrations, have been fabricated and investigated. By appropriate heat treatment of the as-prepared glasses above, transparent glass-ceramics were obtained. Differential scanning calorimetry, X-ray diffraction, optical absorption, and luminescence under both UV and beta-particle excitation have been investigated on as-prepared glasses and glass-ceramics. It has been found that these terbium-activated lithium–lanthanum–aluminosilicate

Z. Pan; K. James; Y. Cui; A. Burger; N. Cherepy; S. A. Payne; R. Mu; S. H. Morgan

2008-01-01

300

The Yb-doped aluminosilicate fibers photodarkening mechanism based on the charge-transfer state excitation  

NASA Astrophysics Data System (ADS)

We have studied the photodarkening effect in fiber preforms with an ytterbium-doped aluminosilicate glass core. The room-temperature stable Yb2+ ions formation in the glass matrix under both UV- and NIR-pumping irradiation was revealed by the method of absorption spectra analysis and the fluorescence spectroscopy technique. Comparative studies of preforms and crystals samples luminescence spectra, obtained under UV-excitation, were performed. A general mechanism of Yb2+ ions and aluminium oxygen-hole centers (Al-OHC) formation as a result of photoinduced process of Yb3+ ions excitation to "charge-transfer state" (CTS) was found for both Yb:YAG crystal and aluminosilicate glass.

Rybaltovsky, A. A.; Bobkov, K. K.; Velmiskin, V. V.; Umnikov, A. A.; Shestakova, I. A.; Guryanov, A. N.; Likhachev, M. E.; Bubnov, M. M.; Dianov, E. M.

2014-03-01

301

Room-temperature persistent spectral hole burning of Eu(3+) in sodium aluminosilicate glasses.  

PubMed

Persistent spectral hole burning has been observed at 77 K, 180 K, and room temperature for Eu(3+) in sodium aluminosilicate glass melted under a reducing atmosphere. In particular, room-temperature persistent spectral hole burning is reported for the first time to our knowledge in Eu(3+) -doped materials. The persistent hole is accompanied by no antiholes and lasts for 1 h at least. The thermal stability of the hole is greater than that of a persistent hole burned for Eu(3+) in sodium aluminosilicate glass melted in air. PMID:18084571

Fujita, K; Tanaka, K; Hirao, K; Soga, N

1998-04-01

302

Photoinduced second-harmonic generation in rare-earth-doped aluminosilicate optical fibers.  

PubMed

The presence of defect states in the band gap is an essential ingredient of recent models of photoinduced second-harmonic generation (SHG) in fibers. We have created such states by doping aluminosilicate glass fibers that do not contain Ge with Ce or Eu and observed SHG from 1.06-microm light after preparation of the fibers with 0.532- and 1.06-microm light. In an aluminosilicate fiber doped with 0.008 wt. % Ce, the SHG conversion efficiency is as high as 1.5% at infrared (1.06-microm) peak powers of 200 W. PMID:19784097

Krol, D M; Simpson, J R

1991-11-01

303

Synthesis and structural characterization of Al-containing interlayer-expanded-MWW zeolite with high catalytic performance.  

PubMed

Treatment of the zeolitic layered precursor of Al-MWW, so-called Al-MWW(P), with diethoxydimethylsilane (DEDMS) in acidic media leads to the formation of an aluminosilicate-type interlayer-expanded zeolite MWW (Al-IEZ-MWW) with expanded 12-membered ring (12-MR) micropores. However, the silylation process under acidic conditions simultaneously causes dealumination from the MWW framework, resulting in a decrease in the acid amount. We have developed a method for preparing Al-IEZ-MWW without leaching of the Al species. The strategy is to conduct the silylation under weakly acidic conditions; the silylation was conducted in an aqueous solution of an ammonium salt, e.g., NH4Cl, instead of HNO3. Subsequent additional acid treatment led to the formation of Al-IEZ-MWW that shows a high catalytic performance in the acylation of anisole compared to typical Al-MWW as well as Al-IEZ-MWW directly prepared under acidic conditions. The change in the state of Al atoms during the preparation process was investigated by high-resolution solid-state (27)Al MAS NMR and (27)Al MQMAS NMR techniques. PMID:24798349

Yokoi, Toshiyuki; Mizuno, Shun; Imai, Hiroyuki; Tatsumi, Takashi

2014-07-21

304

Acetylene hydration on different Cd-zeolites  

Microsoft Academic Search

Various Cd-zeolite preparations, containing adsorbed water in controlled amounts, were contacted with acetylene in an IR cell at 0.03 bar. The activity of the zeolites was estimated from the formation rate of adsorbed acetaldehyde at 50 °C detected by FTIR. Cd-derivatives of MOR, MFI, and clinoptilolite were prepared by conventional ion exchange and by a novel method which is based

Gy. Onyestyák; G. Pál-Borbély; D. Kalló

2004-01-01

305

Thermodynamic modeling of natural zeolite stability  

SciTech Connect

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

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

1997-06-01

306

Zeolites: Structural Properties and Benchmarks of Feasibility  

NASA Astrophysics Data System (ADS)

Zeolites are a class of microporous materials that are immensely useful as molecular sieves and catalysts. While there exist millions of hypothetical zeolite topologies, only 206 have been recognized to exist in nature, and the question remains: What distinguishes known zeolite topologies from their hypothetical counterparts? It has been found that all 206 of the known zeolites can be represented as networks of rigid perfect tetrahedra that hinge freely at the connected corners. The range of configurations over which the corresponding geometric constraints can be met has been termed the "flexibility window". Only a small percentage of hypothetical types exhibit a flexibility window, and it is thus proposed that this simple geometric property, the existence of a flexibility window, provides a reliable benchmark for distinguishing potentially realizable hypothetical structures from their infeasible counterparts. As a first approximation of the behavior of real zeolite materials, the flexibility window provides additional useful insights into structure and composition. In this thesis, various methods for locating and exploring the flexibility window are discussed. Also examined is the assumption that the tetrahedral corners are force-free. This is a reasonable approximation in silicates for Si-O-Si angles above ˜135°. However, the approximation is poor for germanates, where Ge-O-Ge angles are constrained to the range ˜120°-145°. Lastly, a class of interesting low-density hypothetical zeolites is evaluated based on the feasibility criteria introduced.

Dawson, Colby

307

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

308

The zeolite deposits of Greece  

USGS Publications Warehouse

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

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

1996-01-01

309

Zeolite membranes for gas separations  

SciTech Connect

Silicalite-1, a pure silica zeolite, was deposited on a tubular, asymmetric, {gamma}-alumina support. Single gas permeation experiments with N{sub 2}, CH{sub 4}, and CO{sub 2} were carried out on the membrane. Separation experiments for N{sub 2}/CH{sub 4} mixtures were also conducted. Single-gas permeation of H{sub 2} and separation of H{sub 2}/SF{sub 6} mixture were also carried out with the membrane. Composite membranes of silicalite and Ni-SAPO-34 were also fabricated, but no CO{sub 2}/H{sub 2} selectivity was found. It is proposed to use these membranes for methanol synthesis and separation, and for separating H{sub 2} from gasification products for use as fuel cell fuel, etc.

Falconer, J.; Noble, R.

1995-06-01

310

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

311

Reaction of glassy sodium silicates and aluminosilicates with aqueous solutions 8. Action of acid solutions on glassy sodium aluminosilicates with variable acid number  

Microsoft Academic Search

1.The dependence of the acid resistance on the alteration of the oxygen number of sodium aluminosilicate glasses was studied in the region of compositions Na2O · Al2O3 · 2SiO2 - Na2O ·Al2O3 ·6SiO2.2.The acid resistance of glasses of feldspar type is practically unchanged with change of the oxygen number. The chemical resistance of glasses of the Jadeite types and glasses

S. K. Dubrovo

1958-01-01

312

An efficient synthesis of nanocrystalline MFI zeolite using different silica sources: A green approach  

SciTech Connect

Nanocrystalline MFI zeolite was synthesized with a very broad range of silica to alumina ratios using an autoclave for periods of 7 h at 473 K under autogeneous pressure without seeding gel, promoter, organic solvent or sulfuric acid. The procedure has been successfully employed for the synthesis of MFI samples using fumed silica, colloidal silica, aerosil and tetraethylorthosilicate as silica sources. The synthesized samples were characterized by different techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, Scanning electron microscopy. Their average crystallite size ranges from about 26 to 55 nm and they exhibit high crystallinity.

Kalita, Banani [Department of Chemistry, Gauhati University, Guwahati 781014, Assam (India); Talukdar, Anup K. [Department of Chemistry, Gauhati University, Guwahati 781014, Assam (India)], E-mail: anup_t@sify.com

2009-02-04

313

The human crystallin gene families  

PubMed Central

Crystallins are the abundant, long-lived proteins of the eye lens. The major human crystallins belong to two different superfamilies: the small heat-shock proteins (?-crystallins) and the ??-crystallins. During evolution, other proteins have sometimes been recruited as crystallins to modify the properties of the lens. In the developing human lens, the enzyme betaine-homocysteine methyltransferase serves such a role. Evolutionary modification has also resulted in loss of expression of some human crystallin genes or of specific splice forms. Crystallin organization is essential for lens transparency and mutations; even minor changes to surface residues can cause cataract and loss of vision.

2012-01-01

314

Hot isostatic pressing of glass-zeolite composites.  

National Technical Information Service (NTIS)

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. P...

M. C. Hash C. Pereira M. A. Lewis

1996-01-01

315

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

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

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

316

Branched vs. linear hydrocarbon separations with novel modified zeolites.  

SciTech Connect

The conclusions of this paper are: (1) Adsorption/desorption on bulk unmodified zeolites showed isoprene adsorbed by zeolite-L and n-pentane adsorbed by zeolite-Y and ZSM-5; (2) Bulk carbonization is used to passivate zeolite activity toward organic adsorption/decomposition; (3) Based on the bulk modified zeolite separation results, we have determined that the MFI type has the most potential for isoprene enrichment; (4) Modified MFI type membrane are jointly made by Sandia and the Univ. of Colorado. Separation experiments are performed by Goodyear Chemical; (5) Isoprene/n-pentane separations have been demonstrated by using both zeolite membranes and modified bulk zeolites at various temperatures on the Goodyear Pilot-scale unit; and (6) Target zeolite membrane separations values of 6.7% isoprene enrichment have been established by economic analysis calculations by Burns & McDonnell.

Gray, Gary R.; Noble, Richard D.; Nenoff, Tina Maria; Arruebo, Manuel; Ulutagay-Kartin, Mutlu; Johnston, Kaylynn; Anderson, Thomas M.

2005-06-01

317

Branched vs. linear hydrocarbon separations with novel modified zeolites.  

SciTech Connect

Conclusions of this paper are: (1) Adsorption/desorption on bulk unmodified zeolites showed isoprene adsorbed by zeolite-L and n-pentane adsorbed by zeolite-Y and ZSM-5; (2) Bulk carbonization is used to passivate zeolite activity toward organic adsorption/decomposition; (3) Based on the bulk modified zeolite separation results, we have determined that the MFI type has the most potential for isoprene enrichment; (4) Modified MFI type membranes are jointly made by Sandia and the Univ. of Colorado. Separation experiments are performed by Goodyear Chemical; (5) Isoprene/n-pentane separations have been demonstrated by using both zeolite membranes and modified bulk zeolites at various temperatures on the Goodyear Pilot-scale unit; and (6) Target zeolite membrane separations values of 6.7% isoprene enrichment have been established by economic analysis calculations by Burns & McDonnell.

Gray, Gary R.; Noble, Richard D.; Nenoff, Tina Maria; Arruebo, Manuel; Ulutagay-Kartin, Mutlu; Anderson, Thomas M.

2004-08-01

318

Densification and crystallisation behaviour of barium magnesium aluminosilicate glass powder compacts  

Microsoft Academic Search

The densification and crystallisation of barium magnesium aluminosilicate (BMAS) glass powder has been investigated. The aim of the study was to draw conclusions of value for the optimisation of the processing parameters for BMAS matrix ceramic composites. Pressureless sintering and hot-pressing techniques were investigated. The pressureless densification behaviour of cold-uniaxially pressed compacts was determined at isothermal and constant heating rate

K. Lambrinou; O. van der Biest; A. R. Boccaccini; D. M. R. Taplin

1996-01-01

319

Anisotropic shrinkage of barium-magnesium aluminosilicate glass powder compacts during sintering  

Microsoft Academic Search

The shrinkage behaviour of barium-magnesium aluminosilicate glass powder compacts has been measured at isothermal conditions using a heating microscope. The samples showed a varying shrinkage anisotropy during densification at a temperature of 930 °C. This behaviour could not be explained solely on the basis of the pore\\/solid interface orientation during sintering. The experimental values for the shrinkage behaviour are in

A. R. Boccaccini; P. A. Trusty; D. M. R. Taplin

1995-01-01

320

Sodium Sulfate Corrosion of Silicon Carbide Fiber-Reinforced Calcium Aluminosilicate Glass-Ceramic Matrix Composites.  

National Technical Information Service (NTIS)

Hot corrosion effects of Sodium Sulfate (NaSO4) coated Calcium Aluminosilicate (CAS)/Silicon Carbide (SiC) reinforced glass-ceramic matrix composite were investigated using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDX) and X-r...

P. J. Newton

1994-01-01

321

Sodium Sulfate Corrosion of Silicon Carbide Fiber-Reinforced Lithium Aluminosilicate Glass-Ceramic Matrix Composites.  

National Technical Information Service (NTIS)

Sodium sulfate hot corrosion of a SiC fiber-reinforced lithium aluminosilicate (LAS) glass-ceramic matrix composite was studied using Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD). Changes in the microstructural chemical composition of th...

L. C. Maldia

1993-01-01

322

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

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

2003-10-21

323

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...

324

The Kinetics of the Reactions Between Silica and AluminoSilicate Refractories and Molten Iron Alloys  

Microsoft Academic Search

The rate of corrosion of silica and alumino-silicate refractories in Armco iron and iron-carbon melts was measured. An interpretation of the rate data required an experimental investigation of the kinetics of the reactions between iron oxide and silica, and carbon and silica.\\u000aA standard \\

Sid Edward Feldman

1972-01-01

325

Effect of waste aluminosilicate material on cement hydration and properties of cement mortars  

Microsoft Academic Search

The effect of waste material (catalyst used previously in catalytic cracking of petroleum in fluidized bed—fluidized bed cracking catalyst denoted as FBCC) on cement hydration kinetics was investigated in terms of fineness of this admixture. The compressive strength and microstructure of cement mortars were also examined. Variable percentage of this aluminosilicate admixture, originating from batches of quite different grain size

B Pacewska; I Wili?ska; M Bukowska; W Nocu?-Wczelik

2002-01-01

326

Separation of xylene mixtures using polyurethane—zeolite composite membranes  

Microsoft Academic Search

Fractionation of o- and p-xylene isomeric mixtures was performed using pervaporation (PV) with polyurethane (PU) membranes containing ZSM zeolite. The xylene vapor sorption isotherms exhibited a Henry's law relationship in this PU–zeolite blend. In binary solutions the individual xylene uptake was also proportional to the solvent composition. Although incorporating zeolite into the PU–zeolite membrane rendered a decrease in xylene solubility

Shingjiang Jessie Lue; Tsai-hsin Liaw

2006-01-01

327

Preparation and characterization of zeolite framework stabilized cuprous oxide nanoparticles  

Microsoft Academic Search

Zeolite framework stabilized copper(I) oxide nanoparticles (4.8±2.6 nm) were prepared for the first time by using a four step procedure: the ion exchange of Cu2+ ions with the extra framework Na+ ions in Zeolite-Y, the reduction of the Cu2+ ions within the cavities of zeolite with sodium borohydride in aqueous solution, the dehydration of Zeolite-Y with the copper(0) nanoclusters, and the

Mehmet Zahmakiran; Saim Özkar

2009-01-01

328

Comparative sorption kinetic studies of ammonium onto zeolite  

Microsoft Academic Search

The sorption kinetics of ammonium onto three types of zeolite, natural zeolite, natural zeolite covered by biofilm and ammonium-bearing zeolite covered by biofilm, at two particle sizes were studied. The pseudo-first order and pseudo-second order models were fitted to the results by a non-linear method. The batch sorption model, based on a pseudo-second order mechanism, was applied to predict the

Donghui Wen; Yuh-Shan Ho; Xiaoyan Tang

2006-01-01

329

A designed organic–zeolite hybrid acid–base catalyst  

Microsoft Academic Search

An organic–zeolite hybrid catalyst was synthesised via solid-state impregnation of the zeolite with an amount of melamine corresponding to 20mol% of the aluminium content. A high density of basic sites is formed in the zeolite. From infrared spectroscopy and TGA measurements we infer that melaminium cations are formed in the zeolite which are highly thermally stable. IR spectroscopic and TGA

Andrew C. Brooks; Liam France; Cecile Gayot; Jerry Pui Ho Li; Ryan Sault; Andrew Stafford; John D. Wallis; Michael Stockenhuber

330

Monolithic nanoporous crystalline aerogels.  

PubMed

Monolithic aerogels can be easily obtained by drying physical gels formed by linear uncross-linked polymers. Preparation methods, structure, and properties of these physically cross-linked polymeric aerogels are reviewed, with particular emphasis to those whose cross-linking knots are crystallites and, more in particular, crystallites exhibiting nanoporous-crystalline forms. The latter aerogels present beside disordered amorphous micropores (typical of all aerogels) also all identical nanopores of the crystalline phases. Their outstanding guest transport properties combined with low material cost, robustness, durability, and ease of handling and recycle make these aerogels suitable for applications in chemical separations, purification, and storage as well as in biomedicine. Scientific, technological, and industrial perspectives for monolithic nanoporous-crystalline polymeric aerogels are also discussed. PMID:23913316

Daniel, Christophe; Longo, Simona; Ricciardi, Rosa; Reverchon, Ernesto; Guerra, Gaetano

2013-08-01

331

Crystalline molecular flasks  

NASA Astrophysics Data System (ADS)

A variety of host compounds have been used as molecular-scale reaction vessels, protecting guests from their environment or restricting the space available around them, thus favouring particular reactions. Such molecular 'flasks' can endow guest molecules with reactivities that differ from those in bulk solvents. Here, we extend this concept to crystalline molecular flasks, solid-state crystalline networks with pores within which pseudo-solution-state reactions can take place. As the guest molecules can spontaneously align along the walls and channels of the hosts, structural changes in the substrates can be directly observed by in situ X-ray crystallography during reaction. Recently, this has enabled observation of the molecular structures of transient intermediates and other labile species, in the form of sequential structural snapshots of the chemical transformation. Here, we describe the principles, development and applications of crystalline molecular flasks.

Inokuma, Yasuhide; Kawano, Masaki; Fujita, Makoto

2011-05-01

332

Fly ash zeolite catalyst support for Fischer-Tropsch synthesis  

NASA Astrophysics Data System (ADS)

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

Campen, Adam

333

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

334

Hydrogen isotope separation using molecular sieve of synthetic zeolite 3A  

SciTech Connect

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

Kotoh, K.; Kimura, K.; Nakamura, Y.; Kudo, K. [Faculty of Engineering, Kyushu Univ., 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan)

2008-07-15

335

Characterization and environmental application of a Chilean natural zeolite  

Microsoft Academic Search

The use of natural zeolites for environmental applications is gaining new research interests mainly due to their properties and significant worldwide occurrence. The present work describes the characterization of a natural Chilean zeolite and the results as adsorbent for ammonia from aqueous solutions. The zeolitic-rich tuff sample, mainly composed of clinoptilolite and mordenite, consisted of 13 ?m mean volumetric particle

A. H. Englert; J. Rubio

2005-01-01

336

Zeolite membranes – state of their development and perspective  

Microsoft Academic Search

An ideal zeolite membrane combines the general advantages of inorganic membranes (temperature stability, solvent resistance) with a perfect shape selectivity. Due to their “molecular sieve” function, zeolite membranes can principally discriminate the components of gaseous or liquid mixtures dependent on their molecular size. This molecular sieving principle requires a pinhole- and crack-free zeolite membrane. Remarkable separation effects can also be

J Caro; M Noack; P Kölsch; R Schäfer

2000-01-01

337

Removing nitrosamines from mainstream smoke of cigarettes by zeolites  

Microsoft Academic Search

The adsorption of volatile nitrosamines in mainstream smoke of cigarettes by the use of zeolites and other porous materials has been investigated. Zeolites are shown to possess the ability of selectively adsorbing nitrosamines from the mainstream (MS) smoke, and among them, zeolites NaY and ZSM-5 exhibit excellent capacities. The impact of the porous structure and acidity of the adsorbent, the

Yang Xu; Jian Hua Zhu; Li Li Ma; An Ji; Yi Lun Wei; Xi Yong Shang

2003-01-01

338

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

339

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

340

Formation of NaA and -X zeolites from waste solutions in conversion of coal fly ash to zeolites  

Microsoft Academic Search

Na-A and -X zeolites were synthesized from waste solutions in conversion of coal fly ash (Fa) to zeolite. The amorphous SiO2 and Al2O3 of Fa were completely dissolved to form Po, Pt, and Pc type zeolites in NaOH solutions at 85°C. Only 24% of Si4+ eluted from Fa were converted to the zeolites and the remaining waste solutions contained high

Hidekazu Tanaka; Yasuhiko Sakai; Ryozi Hino

2002-01-01

341

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

342

Controlling chemistry with cations: photochemistry within zeolites.  

PubMed

The alkali ions present in the supercages of zeolites X and Y interact with included guest molecules through quadrupolar (cation-pi), and dipolar (cation-carbonyl) interactions. The presence of such interactions can be inferred through solid-state NMR spectra of the guest molecules. Alkali ions, as illustrated in this article, can be exploited to control the photochemical and photophysical behaviors of the guest molecules. For example, molecules that rarely phosphoresce can be induced to do so within heavy cation-exchanged zeolites. The nature (electronic configuration) of the lowest triplet state of carbonyl compounds can be altered with the help of light alkali metal ions. This state switch (n pi*-pi pi*) helps to bring out reactivity that normally remains dormant. Selectivity obtained during the singlet oxygen oxidation of olefins within zeolites illustrates the remarkable control that can be exerted on photoreactions with the help of a confined medium that also has active sites. The reaction cavities of zeolites, like enzymes, are not only well-defined and confined, but also have active sites that closely guide the reactant molecule from start to finish. The examples provided here illustrate that zeolites are far more useful than simple shape-selective catalysts. PMID:12934881

Ramamurthy, V; Shailaja, J; Kaanumalle, Lakshmi S; Sunoj, R B; Chandrasekhar, J

2003-08-21

343

Zeolite-templated Pt/C electrocatalysts  

SciTech Connect

In an effort to reduce the amount of platinum required in low temperature fuel cells, we have prepared electrocatalysts of platinum nanoparticles-on-carbon through zeolite-templating methods. Several different zeolite structure-types, as well as clays and mesoporous silicas were investigated as hosts for the preparation of small Pt clusters through thermal decomposition of ion exchanged (NH{sub 3}){sub 4}Pt{sup 2+}. Several factors relating to cluster confinement and mobility influence cluster size, and clusters below 1 nm with narrow size distribution have been prepared. To enable electrochemical application, the pores of the Pt cluster-containing zeolite were filled with electrically conductive carbon via infiltration with carbon precursors, polymerization, and pyrolysis. The zeolite host was then removed by acid digestion, to leave a micro-/mesoporous Pt/C electrocatalyst possessing Pt clusters of controlled size. Preliminary electrochemical evaluation of these catalysts is reported. The energetics of thermal decomposition of (NH{sub 3}){sub 4}Pt{sup 2+} to form Pt clusters in zeolite X have been investigated through Differential Scanning Calorimetry, and apparent activation energies calculated. The relationship between (NH{sub 3}){sub 4}Pt{sup 2+} decomposition and conditions of calcination has been explored in an effort to better control Pt cluster sizes.

Coker, Eric N.; Steen, William A.; Miller, James E. (Sandia)

2008-06-16

344

High-pressure and -temperature ion exchange of aluminosilicate and gallosilicate natrolite.  

PubMed

The simultaneous application of high pressure and high temperature has been used to achieve direct ion exchange of large cesium cations for the small sodium cations found in the zeolite natrolite by putting it into a superhydrated state with increased pore size. The larger cations remain trapped upon pressure release, and thus, this method is a means of producing new cationic forms of zeolites. PMID:21819090

Hill, Gemma L; Bailey, Edward; Stennett, Martin C; Hyatt, Neil C; Maddrell, Ewan M; McMillan, Paul F; Hriljac, Joseph A

2011-09-01

345

Capturing Ultrasmall EMT Zeolite from Template-Free Systems  

NASA Astrophysics Data System (ADS)

Small differences between the lattice energies of different zeolites suggest that kinetic factors are of major importance in controlling zeolite nucleation. Thus, it is critical to control the nucleation kinetics in order to obtain a desired microporous material. Here, we demonstrate how careful investigation of the very early stages of zeolite crystallization in colloidal systems can provide access to important nanoscale zeolite phases while avoiding the use of expensive organic templates. We report the effective synthesis of ultrasmall (6- to 15-nanometer) crystals of the large-pore zeolite EMT from template-free colloidal precursors at low temperature (30°C) and very high yield.

Ng, Eng-Poh; Chateigner, Daniel; Bein, Thomas; Valtchev, Valentin; Mintova, Svetlana

2012-01-01

346

Crystal engineering of zeolites with graphene.  

PubMed

Achieving control over the morphology of zeolite crystals at the nanoscale is crucial for enhancing their performance in diverse applications including catalysis, sensors and separation. The complexity and sensitivity of zeolite synthesis processes, however, often make such control both highly empirical and difficult to implement. We demonstrate that graphene can significantly alter the morphology of titanium silicalite (TS-1) particles, in particular being able to reduce their dimensions from several hundreds to less than 10 nm. Through electron microscopy and molecular mechanics simulations we propose a mechanism for this change based on the preferential interaction of specific TS-1 surfaces with benzyl-alcohol-mediated graphene. These findings suggest a facile new means of controlling the zeolite morphology and thereby also further demonstrate the potential of graphene in hybrid materials. Moreover, the generality of the mechanism points the way to a new avenue of research in using two-dimensional materials to engineer functional inorganic crystals. PMID:24853328

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

2014-06-12

347

Reorientational dynamics of water confined in zeolites.  

PubMed

We present a detailed molecular-dynamics study of water reorientation and hydrogen-bond dynamics in a strong confinement situation, within the narrow pores of an all-silica Linde type A (LTA) zeolite. Two water loadings of the zeolite are compared with the bulk case. Water dynamics are retarded in this extreme hydrophobic confinement and the slowdown is more pronounced at higher water loading. We show that water reorientation proceeds mainly by large-amplitude angular jumps, whose mechanism is similar to that determined in the bulk. The slowdown upon hydrophobic confinement arises predominantly from an excluded-volume effect on the large fraction of water molecules lying at the interface with the zeolite matrix, with an additional minor contribution coming from a structuring effect induced by the confinement. PMID:24449592

Fogarty, Aoife C; Coudert, François-Xavier; Boutin, Anne; Laage, Damien

2014-02-24

348

Spontaneous proton transfer in Na zeolites  

NASA Astrophysics Data System (ADS)

First-principles room-temperature molecular dynamics (MD) simulations are conducted to investigate proton transfer (PT) in Na zeolites. The MD are performed on the unit cell containing two Al-sites, one of them saturated with H (acid site) and the second one with Na coordinated with three water molecules. The creation of the charged H 3O + cations is suppressed by the Na cation. Spontaneous barrierless PT between the O-sites in the zeolite, however, is possible. The lifetime of the hydronium cation is extremely short (?5 fs). The presence of Na + cations leads to a modified mechanism but does not suppress the proton transfer around the Al-site in zeolites.

Benco, L.; Demuth, T.; Hafner, J.; Hutschka, F.

2000-11-01

349

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; Król, M

2014-12-10

350

Crystal engineering of zeolites with graphene  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

351

Photophysical properties of metal ion functionalized NaY zeolite.  

PubMed

A series of luminescent ion exchanged zeolite are synthesized by introducing various ions into NaY zeolite. Monometal ion (Eu(3+), Tb(3+), Ce(3+), Y(3+), Zn(2+), Cd(2+), Cu(2+)) exchanged zeolite, rare-earth ion (Eu(3+), Tb(3+), Ce(3+)) exchanged zeolite modified with Y(3+) and rare-earth ion (Eu(3+), Tb(3+), Ce(3+)) exchanged zeolite modified with Zn(2+) are discussed here. The resulting materials are characterized by Fourier transform infrared spectrum radiometer (FTIR), XRD, scanning electronic microscope (SEM), PLE, PL and luminescence lifetime measurements. The photoluminescence spectrum of NaY indicates that emission band of host matrix exhibits a blueshift of about 70 nm after monometal ion exchange process. The results show that transition metal ion exchanged zeolites possess a similar emission band due to dominant host luminescence. A variety of luminescence phenomenon of rare-earth ion broadens the application of zeolite as a luminescent host. The Eu(3+) ion exchanged zeolite shows white light luminescence with a great application value and Ce(3+) exchanged zeolite steadily exhibits its characteristic luminescence in ultraviolet region no matter in monometal ion exchanged zeolite or bimetal ions exchanged zeolite. PMID:24392790

Duan, Tian-Wei; Yan, Bing

2014-01-01

352

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

353

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

354

Thermal properties of zeolites: effective thermal conductivity of dehydrated powdered zeolite 4A  

Microsoft Academic Search

The determination of the subambient effective thermal conductivity of evacuated powdered zeolite 4A is described. The results are modelled successfully in terms of boundary scattering, point defects and three-phonon Umklapp processes.

Vladimir V. Murashov; Mary Anne White

2002-01-01

355

Liquid crystalline composites containing phyllosilicates  

DOEpatents

The present invention provides barrier films having reduced gas permeability for use in packaging and coating applications. The barrier films comprise an anisotropic liquid crystalline composite layer formed from phyllosilicate-polymer compositions. Phyllosilicate-polymer liquid crystalline compositions of the present invention can contain a high percentage of phyllosilicate while remaining transparent. Because of the ordering of the particles in the liquid crystalline composite, barrier films comprising liquid crystalline composites are particularly useful as barriers to gas transport.

Chaiko; David J. (Naperville, IL) [Naperville, IL

2007-05-08

356

Coalescence of Crystalline Drops  

NASA Astrophysics Data System (ADS)

We present the first experimental analysis of drop coalescence in a case where the dynamics is not governed by viscous dissipation in the bulk nor by the inertia of the fluid flow, only by the geometry and mobility of surfaces. We found such a situation in the physics of 3He crystals near 0.32K where the latent heat of crystallization vanishes. Two crystalline drops of 3He coalesce if their crystalline orientations are identical: a neck forms after the contact at time t=0, and the shape evolves towards that of one convex crystal by local growth and melting in a fraction of a second. We have found that the neck radius initially increases as t1/3, as predicted by Maris. This behavior is also expected for superfluid drops. It is clearly distinguished from the logarithmic behavior and from the t1/2 power law which have been predicted by Eggers et al. in more usual situations.

Ishiguro, R.; Graner, F.; Rolley, E.; Balibar, S.

2004-11-01

357

Crystalline color superconductors  

NASA Astrophysics Data System (ADS)

Inhomogeneous superconductors and inhomogeneous superfluids appear in a variety of contexts including quark matter at extreme densities, fermionic systems of cold atoms, type-II cuprates, and organic superconductors. In the present review the focus is on properties of quark matter at high baryonic density, which may exist in the interior of compact stars. The conditions realized in these stellar objects tend to disfavor standard symmetric BCS pairing and may favor an inhomogeneous color superconducting phase. The properties of inhomogeneous color superconductors are discussed in detail and in particular of crystalline color superconductors. The possible astrophysical signatures associated with the presence of crystalline color superconducting phases within the core of compact stars are also reviewed.

Anglani, Roberto; Casalbuoni, Roberto; Ciminale, Marco; Ippolito, Nicola; Gatto, Raoul; Mannarelli, Massimo; Ruggieri, Marco

2014-04-01

358

Skeletal isomerization of 1-butene over ferrierite and ZSM-5 zeolites: influence of zeolite acidity  

Microsoft Academic Search

Three ferrierite (FER) and five ZSM-5 (MFI) zeolites with SiO2Al2O3 ratio ranging from 27 to 2000 are tested as catalysts for the skeletal isomerization of 1-butene at 350–450°C and atmospheric total pressure in order to study the influence of acidity and pore structure of zeolite on conversion and selectivity. The catalytic and NH3 temperature-programmed desorption results from FER and MFI

Gon Seo; Hwan Seok Jeong; Suk Bong Hong; Young Sun Uh

1996-01-01

359

Effect of zeolites on chitosan\\/zeolite hybrid membranes for direct methanol fuel cell  

Microsoft Academic Search

Zeolites including 3A, 4A, 5A, 13X, mordenite, and HZSM-5 were incorporated into chitosan (CS) matrix to fabricate the hybrid membranes for direct methanol fuel cell (DMFC). Due to the presence of hydrogen bonds between CS and zeolite, the hybrid membranes displayed desirable thermal and mechanical stabilities. Through free volume characteristics analysis by positron annihilation lifetime spectroscopy (PALS) technique, it was

Jingtao Wang; Xiaohong Zheng; Hong Wu; Bin Zheng; Zhongyi Jiang; Xiaopeng Hao; Baoyi Wang

2008-01-01

360

Formation and structure of Langmuir-Blodgett films of organo-modified aluminosilicate with high surface coverage.  

PubMed

We have developed an effective organo-modification method at the organic solvent/distilled water interface of natural aluminosilicate clay surfaces. We also investigated the molecular arrangement of organo-modified aluminosilicate with high surface coverage in Langmuir-Blodgett films (LB) by performing out-of-plane and in-plane X-ray diffraction (XRD) measurements. In addition, the surface morphology of mixed monolayers of organo-modified aluminosilicate and several biodegradable polymers (e.g., poly(L-lactide), PLLA) was also characterized by atomic force microscopy (AFM). The in-plane XRD results of multilayers of organo-modified aluminosilicate formed by the LB method indicate the formation of a two-dimensional lattice of hydrocarbons on the aluminosilicate surface. These hydrocarbons of organo-modified reagents packed hexagonal or orthorhombic in films. Based on our experimental findings, the LB technique enabled the formation of a densely packed organo-modified aluminosilicate monolayer at the water surface. Furthermore, for mixed monolayer systems comprising an organo-modified clay with high surface coverage and biodegradable polymers, a miscible surface was observed by AFM on a mesoscopic scale, whereas those with low surface coverage formed phase-separated structures. PMID:23141704

Fujimori, Atsuhiro; Arai, Shuntaro; Kusaka, Jun-ichi; Kubota, Munehiro; Kurosaka, Kei-ichi

2013-02-15

361

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

362

Crystalline beam ground state  

SciTech Connect

In order to employ molecular dynamics (MD) methods, commonly used in condensed matter physics, we have derived the equations of motion for a beam of charged particles in the rotating rest frame of the reference particle. We include in the formalism that the particles are confined by the guiding and focusing magnetic fields, and that they are confined in a conducting vacuum pipe while interacting with each other via a Coulomb force. Numerical simulations using MD methods has been performed to obtain the equilibrium crystalline beam structure. The effect of the shearing force, centrifugal force, and azimuthal variation of the focusing strength are investigated. It is found that a constant gradient storage ring can not give a crystalline beam, but that an alternating-gradient (AG) structure can. In such a machine the ground state is, except for one-dimensional (1-D) crystals, time dependent. The ground state is a zero entropy state, despite the time-dependent, periodic variation of the focusing force. The nature of the ground state, similar to that found by Schiffer et al. depends upon the density and the relative focusing strengths in the transverse directions. At low density, the crystal is 1-D. As the density increases, it transforms into various kinds of 2-D and 3-D crystals. If the energy of the beam is higher than the transition energy of the machine, the crystalline structure can not be formed for lack of radial focusing.

Wei, Jie [Brookhaven National Lab., Upton, NY (United States); Li, Xiao-Ping [Rutgers Univ., Piscataway, NJ (United States). Dept. of Physics; Sessler, A.M. [Lawrence Berkeley Lab., CA (United States)

1993-06-11

363

Immobilization of simulated high-level liquid wastes in sintered borosilicate, aluminosilicate and aluminoborosilicate glasses  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to report on the results obtained with different vitreous materials: a German borosilicate glass (VG98/12), its local counterpart (Símil VG), a natural aluminosilicate volcanic glass (VV), and two German aluminoborosilicate glasses (SG7 and SG8), with incorporated simulated high-level liquid wastes (HLLW), LWR and PHWR types. The optimal conditions for pressure and pressureless sintering are given, as well as the simulation, formulation and preparation of the simulated HLLW type PHWR, as well as the corrosion and thermal behavior of the waste forms obtained. Leaching rates of aluminosilicate (VV) and aluminoborosilicate (SG7) glasses were about 10 -2 g m -2 d -1, that is one order of magnitude lower than those for borosilicate glasses. The devitrification of aluminoborosilicate glass (SG7) increased leaching rate by a factor of 3 for Mo.

Bevilacqua, Arturo M.; Messi de Bernasconi, Norma B.; Russo, Diego O.; Audero, Miguel A.; Sterba, Mario E.; Heredia, Arturo D.

1996-04-01

364

Martian volatiles in shergottite EETA 79001 - New evidence from oxidized sulfur and sulfur-rich aluminosilicates  

NASA Astrophysics Data System (ADS)

This report summarizes initial results of a search for mineralogical and petrological clues to the origin of trapped gases in Lith-C. Evidence is presented that, although Antarctic weathering effects in EETA 79001 are more significant than has been previously recognized, it is possible to distinguish terrestrial from preterrestrial alteration effects through study of properly selected control samples. The major conclusion is that Lith-C formed in an atmosphere that was sufficiently oxidizing to form sulfate from sulfide and that at least a small portion of the sulfate probably exists as sulfur-rich, aluminosilicate mineraloids. The additional enrichment of chlorine in one variety of aluminosilicate denotes a possible petrogenetic link with the S- and Cl-rich, fine-grained materials that cover the Martian surface. Therefore, results reported here are consistent with the origin of EETA 79001 as a Martian rock.

Gooding, J. L.; Muenow, D. W.

1986-06-01

365

Phyllosilicates and nanophase aluminosilicates at Mawrth Vallis and their geochemical implications  

NASA Astrophysics Data System (ADS)

Modelling of TES data has shown the presence of allophane in several sites on Mars with the highest abundances in the Mawrth Vallis region [1]. Analyses of CRISM data at Mawrth Vallis are also consistent with the nanophase aluminosilicates allophane and imogolite in the upper Al/Si-rich phyllosilicatebearing unit [2,3]. We report here on recent lab analyses of several allophane and imogolite samples and new analyses of CRISM and TES data enabled with this larger spectral library. Clay-type components are modelled across the Mawrth Vallis region at ~50-75 vol% in bright units and ~35-55 vol% in dark units using TES data. Identification of nanophase aluminosilicates at Mawrth Vallis helps reconcile the NIR and TIR data of the region, and has important implications for understanding past pedogenic and igneous processes.

Bishop, J. L.; Rampe, E.

2013-09-01

366

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

PubMed

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 Brønsted 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. PMID:24566616

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

2014-01-01

367

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 Brønsted 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

368

FIBER LOADING OF HARDWOOD PULP BY IN-SITU PRECIPITATION OF ALUMINOSILICATE  

Microsoft Academic Search

Sodium aluminosilicate has been precipitated in-situ as filler on hard- wood bleached kraft pulp fibers using papermaker's alum and sodium silicate. The filler was produced in two ways, first in the absence of the fibers and second in the presence of fibers, i.e. in-situ precipitation of filler. The filler produced in absence of fiber was then added to the pulp

Vipul S. Chauhan; Surendra P. Singh; Pramod K. Bajpaib

369

Formation processes and main properties of hollow aluminosilicate microspheres in fly ash from thermal power stations  

Microsoft Academic Search

The main parameters of aluminosilicate microspheres formed at thermal power stations in Russia were studied; these parameters\\u000a are responsible for the prospective industrial application of these microspheres. A comparative analysis of the properties\\u000a of mineral coal components, the conditions of coal combustion, and the effects of chemical and phase-mineralogical compositions\\u000a of mineral impurities in coals from almost all of the

V. S. Drozhzhin; M. Ya. Shpirt; L. D. Danilin; M. D. Kuvaev; I. V. Pikulin; G. A. Potemkin; S. A. Redyushev

2008-01-01

370

Effects of Na2O on the Thermal Shock Resistance of Aluminosilicate Refractory Ceramics  

Microsoft Academic Search

This report presents the results of an experimental study of the effects of Na2O on the thermal shock resistance (number of cold shock cycles to failure) of aluminosilicate refractory ceramics. The addition of 4–6% mole is shown to improve the thermal shock resistance, which is characterized by the number of shock cycles to failure. The Na2O changes the viscosity-temperature characteristics,

W. O. Soboyejo; E. T. Akpan; I. B. Bashir; J. Zimba; N. Hosannah; S. Allameh

2007-01-01

371

Mesostructured aluminosilicate alkylation catalysts for the production of aromatic amine antioxidants  

Microsoft Academic Search

The conversion of diphenylamine (DPA) and ?-methylstyrene (AMS) to the antioxidants mono- and dicumenyldiphenylamine was carried out over mesostructured aluminosilicate catalysts with hexagonal (2% Al-MCM-41), wormhole (2% Al-HMS), and lamellar\\/vesicular (2% Al-MSU-G) framework structures. A commercial acid-treated clay catalyst, Engelhard F-20, was included for comparison perposes. The yields of the desired antioxidant, namely dicumenyldiphenylamine (DCDPA), increased in the order F-20

Yu Liu; Seong Su Kim; Thomas J Pinnavaia

2004-01-01

372

Comment on "Photodarkening in Yb-doped aluminosilicate fibers induced by 488 nm irradiation".  

PubMed

We present some strong evidence against the assignment of an ytterbium-related oxygen deficiency center (ODC) near 230 nm in Yb-doped aluminosilicate glass in the Letter by Yoo [Opt. Lett.32, 1626 (2007)]. The strong 230 nm absorption band is actually a charge-transfer band corresponding to the transfer of an electron from nearby oxygen ligands to the ytterbium ion and not related to ODCs. PMID:18516178

Engholm, M; Norin, L

2008-06-01

373

Highly nonlinear near-resonant photodarkening in a thulium-doped aluminosilicate glass fiber.  

PubMed

Permanent photoinduced optical attenuation has been observed in Tm(3+)-doped aluminosilicate glass fibers on exposure to near-resonance mode-locked 1064-nm radiation at 300 K. The rate of this darkening was observed to follow a 4.7 +/- 0.4 power dependence on the 1064-nm intensity. The result shows that absorption of infrared light of moderate intensity can lead to photoionization in rare-earth-doped glass, provided that a multiphoton stepwise excitation channel exists. PMID:19802277

Broer, M M; Krol, D M; Digiovanni, D J

1993-05-15

374

Arc-induced long-period gratings in aluminosilicate glass fibers.  

PubMed

Permanent long-period gratings were written using arc discharges in two aluminosilicate fibers, one of which was doped with erbium. Reversible gratings were also mechanically induced in both fibers. The thermal behavior of the arc-induced gratings was investigated at up to 1100 degrees C. It was found that the shift of the resonant wavelengths exhibited a well-defined linear dependence on temperature up to 700 degrees C. PMID:16127911

Rego, Gaspar; Falate, Rosane; Santos, José Luís; Salgado, Henrique M; Fabris, José Luís; Semjonov, Sergei L; Dianov, Eugene M

2005-08-15

375

ADSORPTION OF CHROMIUM IONS FROM AQUEOUS SOLUTION USING ACTIVATED CARBO-ALUMINOSILICATE MATERIAL  

Microsoft Academic Search

A novel activated carbo-aluminosilicate material prepared from oil shale was used as an adsorbent for chromium ions from aqueous\\u000a solutions. The maximum sorption capacity was found to be 92 mg\\/g. This value was obtained at pH 4 which is bellow the zero\\u000a point of charge (pHZPC) for this material. The pHZPC was estimated at different mass to solution ratios and

REYAD SHAWABKEH

376

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

377

Electrical properties of zeolitized volcaniclastic materials  

Microsoft Academic Search

The interpretation of electromagnetic anomalies associated with volcanic activity requires a good understanding of two rock properties, the electrical conductivity and the streaming potential coupling coefficient. We measured these properties on 22 consolidated tuff samples containing clays and zeolites typically found in hydrothermal systems or in other areas of high water-rock interactions associated with active volcanic areas. These rocks exhibit

A. Revil; D. Hermitte; E. Spangenberg; J. J. Cochemé

2002-01-01

378

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

379

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 ...

380

Reactions of aliphatic ketones on zeolites  

Microsoft Academic Search

Reactions of some ketones (acetone, methyl ethyl ketone and diethyl ketone) on the H-form of ZSM-5, ZSM-11, mordenite and erionite have been studied in an integral reactor. At a reaction temperature of 300 or 350°C acetone is selectively transformed on all these zeolites into isobutene, while with higher ketones substantial amounts of aromatics are formed.

K. Nedomová; S. Beran

1986-01-01

381

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...

382

Multicomponent liquid ion exchange with chabazite zeolites  

SciTech Connect

In spite of the increasing commercial use of zeolites for binary and multicomponent sorption, the understanding of the basic mass-transfer processes associated with multicomponent zeolite ion-exchange systems is quite limited. This study was undertaken to evaluate Na-Ca-Mg-Cs-Sr ion exchange from an aqueous solution using a chabazite zeolite. Mass-transfer coefficients and equilibrium equations were determined from experimental batch-reactor data for single and multicomponent systems. The Langmuir isotherm was used to represent the equilibrium relationship for binary systems, and a modified Dubinin-Polyani model was used for the multicomponent systems. The experimental data indicate that diffusion through the microporous zeolite crystals is the primary diffusional resistance. Macropore diffusion also significantly contributes to the mass-transfer resistance. Various mass-transfer models were compared to the experimental data to determine mass-transfer coefficients. Effective diffusivities were obtained which accurately predicted experimental data using a variety of models. Only the model which accounts for micropore and macropore diffusion occurring in series accurately predicted multicomponent data using single-component diffusivities. Liquid and surface diffusion both contribute to macropore diffusion. Surface and micropore diffusivities were determined to be concentration dependent.

Robinson, S.M.; Arnold, W.D. Jr.; Byers, C.W.

1993-10-01

383

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...

384

Coating of crystalline nuclear waste forms to improve inertness  

SciTech Connect

Microspheres of a crystalline waste form prepared by sol-gel processing were successfully coated with layers of pyrolytic carbon and silicon carbide to isolate the radioactive wastes from the biosphere. A separate process for cesium immobilization was developed which loads 5 wt% Cs onto zeolite particles for subsequent coating. Pyrolytic carbon-coated particles showed leach rates approx. =2 to 4 orders of magnitude less than the candidate reference borosilicate glass waste form. Aqueous leach-test results of coated waste forms were below detection limits of such sensitive analytical techniques as atomic absorption and inductively coupled plasma atomic emission. Significant progress was made in applying sol-gel and fluidized bed coating technology to the solidification of high-level nuclear wastes. The authors successfully prepared microspheres containing simulated wastes of Synroc-B, Synroc-D, a modified Synroc-D where alumina was previously removed from the waste, and a very high waste-loading composition containing 90% waste and 10% ZrO/sub 2/. Each of these compositions was sintered at 1000/sup 0/C and coated with pyrocarbon at temperatures as low as 1000/sup 0/C. Silicon carbide can be applied to these pyrocarbon-coated particles at temperatures as low as 900/sup 0/C for additional inertness or for oxidation resistance. Cesium was isolated by pyrocarbon-coating cesium-loaded zeolite. Pyrocarbon and SiC coatings successfully reduced the leach rates to below detection limits.

Stinton, D.P.; Angelini, P.; Caputo, A.J.; Lackey, W.J.

1982-08-01

385

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

386

The effects of intrapleural injections of alumina and aluminosilicate (ceramic) fibres.  

PubMed Central

Groups of rats, 24 male and 24 female, approximately 8 weeks old, were dosed by a single intrapleural injection with a saline suspension of refractory alumina fibres (Saffil fibres ICI plc) either as manufactured or after extensive thermal ageing; or one of two aluminosilicate ('ceramic') fibres with different diameter distributions. Similar groups were dosed with a suspension of UICC chrysotile A asbestos or saline solution to serve as positive and negative controls respectively. Rats were maintained to 85% mortality and all decedents and terminal sacrifices were closely examined for the presence of mesothelioma. Malignant mesothelioma was diagnosed in ten rats, seven dosed with asbestos and three dosed with aluminosilicate fibre B. No mesothelioma was detected in any rat dosed with Saffil fibres or aluminosilicate fibre A or in negative controls. The results support the predicted inert nature of Saffil alumina fibres and provide further evidence for the importance of fibre dimension in the induction of mesothelioma. The implication of the results for inhalation exposures is discussed.

Pigott, G. H.; Ishmael, J.

1992-01-01

387

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

388

Origins of saccharide-dependent hydration at aluminate, silicate, and aluminosilicate surfaces.  

PubMed

Sugar molecules adsorbed at hydrated inorganic oxide surfaces occur ubiquitously in nature and in technologically important materials and processes, including marine biomineralization, cement hydration, corrosion inhibition, bioadhesion, and bone resorption. Among these examples, surprisingly diverse hydration behaviors are observed for oxides in the presence of saccharides with closely related compositions and structures. Glucose, sucrose, and maltodextrin, for example, exhibit significant differences in their adsorption selectivities and alkaline reaction properties on hydrating aluminate, silicate, and aluminosilicate surfaces that are shown to be due to the molecular architectures of the saccharides. Solid-state (1)H, (13)C, (29)Si, and (27)Al nuclear magnetic resonance (NMR) spectroscopy measurements, including at very high magnetic fields (19 T), distinguish and quantify the different molecular species, their chemical transformations, and their site-specific adsorption on different aluminate and silicate moieties. Two-dimensional NMR results establish nonselective adsorption of glucose degradation products containing carboxylic acids on both hydrated silicates and aluminates. In contrast, sucrose adsorbs intact at hydrated silicate sites and selectively at anhydrous, but not hydrated, aluminate moieties. Quantitative surface force measurements establish that sucrose adsorbs strongly as multilayers on hydrated aluminosilicate surfaces. The molecular structures and physicochemical properties of the saccharides and their degradation species correlate well with their adsorption behaviors. The results explain the dramatically different effects that small amounts of different types of sugars have on the rates at which aluminate, silicate, and aluminosilicate species hydrate, with important implications for diverse materials and applications. PMID:21562207

Smith, Benjamin J; Rawal, Aditya; Funkhouser, Gary P; Roberts, Lawrence R; Gupta, Vijay; Israelachvili, Jacob N; Chmelka, Bradley F

2011-05-31

389

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 {approx}1275 deg. 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 6.35 mm diameter source with an alumino-silicate coating, {<=}0.25 mm thick, has a measured lifetime of {approx}40 h at {approx}1275 deg. C, when pulsed at 0.05 Hz and with pulse length of {approx}6 {mu}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. 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. [Lawrence Berkeley National Laboratory (LBNL), One Cyclotron Road, Berkeley, California 94720 (United States)

2012-04-15

390

Origins of saccharide-dependent hydration at aluminate, silicate, and aluminosilicate surfaces  

PubMed Central

Sugar molecules adsorbed at hydrated inorganic oxide surfaces occur ubiquitously in nature and in technologically important materials and processes, including marine biomineralization, cement hydration, corrosion inhibition, bioadhesion, and bone resorption. Among these examples, surprisingly diverse hydration behaviors are observed for oxides in the presence of saccharides with closely related compositions and structures. Glucose, sucrose, and maltodextrin, for example, exhibit significant differences in their adsorption selectivities and alkaline reaction properties on hydrating aluminate, silicate, and aluminosilicate surfaces that are shown to be due to the molecular architectures of the saccharides. Solid-state 1H, 13C, 29Si, and 27Al nuclear magnetic resonance (NMR) spectroscopy measurements, including at very high magnetic fields (19 T), distinguish and quantify the different molecular species, their chemical transformations, and their site-specific adsorption on different aluminate and silicate moieties. Two-dimensional NMR results establish nonselective adsorption of glucose degradation products containing carboxylic acids on both hydrated silicates and aluminates. In contrast, sucrose adsorbs intact at hydrated silicate sites and selectively at anhydrous, but not hydrated, aluminate moieties. Quantitative surface force measurements establish that sucrose adsorbs strongly as multilayers on hydrated aluminosilicate surfaces. The molecular structures and physicochemical properties of the saccharides and their degradation species correlate well with their adsorption behaviors. The results explain the dramatically different effects that small amounts of different types of sugars have on the rates at which aluminate, silicate, and aluminosilicate species hydrate, with important implications for diverse materials and applications.

Smith, Benjamin J.; Rawal, Aditya; Funkhouser, Gary P.; Roberts, Lawrence R.; Gupta, Vijay; Israelachvili, Jacob N.; Chmelka, Bradley F.

2011-01-01

391

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...

392

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

393

First Principles Simulations of Hydrocarbon Conversion Processes in Functionalized Zeolitic Materials  

NASA Astrophysics Data System (ADS)

With increasing demand for chemicals and fuels, and finite traditional crude oil resources, there is a growing need to invent, establish, or optimize chemical processes that convert gasifiable carbon-based feedstocks (e.g., coal, natural gas, oil sands, or biomass) into the needed final products. Catalysis is central to almost every industrial chemical process, including alkane metathesis (AM) and the methanol-to-hydrocarbons (MTH) process, which represent final steps in a sequence of hydrocarbon conversion reactions. An in depth understanding of AM and MTH is essential to the selective production of the desired end products. In this dissertation, ab initio density functional theory simulations provide unique mechanistic and thermodynamic insight of specific elementary steps involved in AM and MTH as performed on zeolite supports. Zeolites have been employed throughout the petroleum industry because of their ability to perform acid-catalyzed reactions (e.g., cracking or MTH). The crystalline structure of zeolites imparts regular microporous networks and, in turn, the selective passage of molecules based on shape and functionality. Many different elements can be grafted onto or substituted into zeolites, resulting in a broad range of catalytic behavior. However, due to the variety of competing and secondary reactions that occur at experimental conditions, it is often difficult to extract quantitative information regarding individual elementary steps. ab initio calculations can be particularly useful for this purpose. Alkane metathesis (i.e., the molecular redistribution or chain length averaging of alkanes) is typically performed by transition metal hydrides on amorphous alumina or silica supports. In Chapter 3, the feasibility of AM in zeolites is assessed by using a grafted Ta-hydride complex to explore the full catalytic cycle in the self-metathesis of ethane. The decomposition of a Ta-metallacyclobutane reaction intermediate that forms during olefin metathesis is responsible for the largest activation energy of the catalytic cycle. This assessment is similar to the findings of alkane metathesis studies on alumina/silica supports and indicates that the entire AM cycle can be performed in zeolites by isolated single-atom transition metal hydrides. Performed over acid form zeolites, MTH is used in the conversion of methanol into a broad range of hydrocarbons, including alkenes, alkanes, and aromatics. For reasons that are not yet rigorously quantified, product selectivities vary dramatically based on the choice of catalyst and reaction conditions. The methylation of species containing double bonds (i.e., co-catalysts) is central to the overall process. Distinct structure-function relationships were found with respect to the elementary steps in the methylation and beta-scission of olefins. In Chapter 4, the role of zeolite topology in the step-wise methylation of ethene by surface methoxides is investigated. Elementary steps are studied across multiple frameworks (i.e., BEA, CHA, FER, MFI, and MOR) constituting a wide variety of confinement environments. The reaction of surface methoxides with ethene is found to require a transition state containing a primary carbocation. The barrier height is found to decrease nearly monotonically with respect to the degree of dispersion interactions stabilizing the primary carbocationic species in the transition state. In addition, quantification of the ``local'' dispersion energy indicates that confinement effects can not be simply correlated to pore size. The beta-scission of olefins plays an important role in the product selectivities of many important chemical processes, including MTH. In Chapter 5, beta-scission modes involving C6 and C8 isomers are investigated at a single, isolated Bronsted acid site within H-ZSM-5. We find that the relative enthalpic barriers of beta-scission elementary steps can be rationalized by the substitution order of the two different carbocationic carbon atoms that are present in the reactant (C+) and transition states (betaC). In fact, the increase in c

Mazar, Mark Nickolaus

394

Zeolite catalysis in conversion of cellulosics. Annual report  

SciTech Connect

The authors have studied the kinetics of oxylose/xylulose isomerization in significant detail over a variety of zeolites and obtained the pseudo-first order reaction rate constants. The authors have found that HY zeolite is still the best material and zeolites are more selective than homogeneous acid catalysts where decomposition of the sugar compounds is much faster. They have completed, as described in the Year 2 Work Plan, the study of cellobiose hydrolysis with an ion exchange resin. The kinetics of the solid-catalyzed reaction is qualitatively similar to that for catalysis by homogeneous acids. The planned program of NMR studies has revealed the dynamics of sugar molecules within the zeolite cavities. Two chemisorbed and a physisorbed state have been identified in HY zeolite. A new state, accounting for as much as a half of the sugar, has been found in ZSM-5 zeolite.

Tsao, G.T.

1994-02-01

395

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.

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

2013-01-01

396

Preparation of Robust, Thin Zeolite Membrane Sheet for Molecular Separation  

SciTech Connect

This paper reports a feasibility study on the preparation of zeolite membrane films on a thin, porous metal support sheet (50-{micro}m thick). Zeolite sodium A (NaA) and silicalite zeolite frameworks are chosen to represent synthesis of respective hydrophilic-type and hydrophobic-type zeolite membranes on this new support. It is found that a dense, continuous inter-grown zeolite crystal layer at a thickness less than 2 {micro}m can be directly deposited on such a support by using direct and secondary growth techniques. The resulting membrane shows excellent adhesion on the metal sheet. Molecular-sieving functions of the prepared membranes are characterized with ethanol/water separation, CO2 separation, and air dehumidification. The results show great potential to make flexible metal-foil-like zeolite membranes for a range of energy conversion and environmental applications.

Liu, Wei; Zhang, Jian; Canfield, Nathan L.; Saraf, Laxmikant V.

2011-10-19

397

Necrotizing infundibular crystalline folliculitis.  

PubMed

We describe a 22-year-old woman with a background of acne who developed multiple folliculocentric facial papules associated with sharply demarcated waxy, keratotic plugs. Multiple skin biopsies showed umbilicated craters that were filled with dispersed bundles of eosinophilic filaments embedded in a pale amorphous matrix forming a plug. The plugs bulged into the upper dermis. Serial sections showed vacuolar and filamentous destruction of the infundibular and adjacent perifollicular epithelium and a close relationship of the crystalline necrosis to follicles. Electron microscopy revealed that the filamentous bundles were tonofilaments. No fresh material was available for polarization and the paraffin sections failed to polarize. The clinical and pathological findings of the lesions in our patient were identical to those reported as a new perforating disorder with urate-like crystals. Our case indicates that the process may represent crystalline folliculocentric necrosis rather than a primary perforating disorder. The nature and basis of the crystals that have a urate-like appearance remain to be determined. PMID:11453930

Kossard, S; Scurry, J; Killingsworth, M

2001-07-01

398

Development of low-cost integrated zeolite collector  

NASA Astrophysics Data System (ADS)

The optimum zeolite loading and the best zeolite for this purpose were determined by careful mathematical analysis, followed by experimental test, to confirm the theoretical results. The integrated collector design was then completed and the collector was constructed. After sealing and vacuum testing the zeolite panels and heat exchanges, the collector was coated with flat black paint and provided with double glazing, aluminum frame and insulation. Preliminary testing indicates close agreement with theoretical predictions of its performance.

Tchernev, D. I.

1981-07-01

399

Random walk theory of reaction kinetics in zeolites  

Microsoft Academic Search

We discuss application of the continuous-time random walk (CTRW) model to studying the kinetics of pseudo-first-order reactions in zeolites. The model includes distance-dependent reaction mechanism, details of the zeolite structure, and dynamics of migration of guest molecules between adsorption sites. Diffuse-reflectance transient-absorption study of triplet anthracene quenching by azulene in NaY zeolite shows that quenching can occur when reactants are

A. V. Barzykin; S. Hashimoto

2000-01-01

400

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

401

Abnormalities of cation movements in 3A zeolite  

Microsoft Academic Search

The dielectric spectra of dehydrated and partially hydrated 3A zeolites with the cation composition of Na6.1K5.9-A were measured to investigate movements of cations in the zeolite (‘A’ stands for the framework of A zeolite). The spectra of dehydrated state showed two relaxations (relax I in the lower frequency side and relax II in the higher frequency side) in the ranges

Tatsuo Ohgushi; Yuya Sakai; Yoshimichi Adachi

402

Polyfuran\\/zeolite LTA composites and adsorption properties  

Microsoft Academic Search

Composites of polyfuran (PFu) with LTA type (3A, 4A, 5A) zeolites were prepared via chemical oxidative polymerization of furan (Fu) in the presence of a dispersion of zeolites (powder) in ACN solvent using anhydrous FeCl3 oxidant at an ambient temperature. The composites were characterized by Fourier transform infrared spectroscopic (FTIR) analysis. FTIR results showed that the composites of 3A zeolite

Songül ?en; Belgin Bardakç?; Ay?e Gül Yavuz; Ay?egül Uygun Gök

2008-01-01

403

Adsorption of CO on LTA zeolite adsorbents: An IR investigation  

Microsoft Academic Search

The low temperature adsorption of CO on the zeolites K-LTA (3A) Na-LTA (4A) and Ca,Na-LTA (5A) has been investigated by IR spectroscopy. For comparison, the adsorption of CO on K-MOR, Na-MOR and Ca-MOR has also been studied. CO adsorption on K-LTA zeolite is mostly limited at the external surface. In the case of Na-LTA zeolite, terminal Na+ carbonyls are formed.

Tania Montanari; Isabel Salla; Guido Busca

2008-01-01

404

Predicting locations of non-framework species in zeolite materials  

Microsoft Academic Search

A new grid-based algorithm developed at Molecular Simulations, and molecular dynamics method have been applied to modeling the locations of non-framework species in zeolites. This new method locates the energy minima for various frameworks and populates these sites with the non-framework species. The cation locations were predicted in dehydrated zeolite adsorbents and catalysts, such as Na88X, Ca48X, mixed cation zeolite

V. V. Guliants; J. T. Mullhaupt; J. M. Newsam; A. M. Gorman; C. M. Freeman

1999-01-01

405

Methane partial oxidation in iron zeolites: theory versus experiment  

Microsoft Academic Search

The conversion of methane to methanol over zeolitic ?-oxygen sites has been demonstrated using Fe-ZSM-5. To discriminate between mono- and poly-nuclear active sites, we prepared the [Fe]-ZEO with iron in the ZEOlite lattice via direct synthesis and Fex-ZEO, by dispersion of xwt.% iron on the ZEOlite. Shape-selective formation of nano-clusters of iron oxides with various sizes is realized inside the

P. P. Knops-Gerrits; W. A. Goddard

2001-01-01

406

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 150°C 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 500°C prior to use in order to

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

2004-01-01

407

Zeolite-chrome tanning: From laboratory to pilot scale  

Microsoft Academic Search

Synthetic Na-zeolites (NaA, NaX, NaAX) were investigated as tanning agents in leather production from sheepskin and calfskin pelts. It was found in laboratory scale testing that the combined use of zeolite and chrome sulphate results in both higher float exhaustion and higher shrinkage temperatures in shorter time than in conventional chrome tannage. The best results were obtained with zeolite NaA.

P. Ciambelli; D. Sannino; B. Naviglio; A. M. Manna; V. Vaiano; G. Calvanese; G. Vietri; S. Gallo

2005-01-01

408

NMR Study on the Acidity of TS1 Zeolite  

Microsoft Academic Search

The acidic properties of TS-1 and Silicalite-1 zeolites have been investigated by the solid-state MAS NMR technique capable of in situ sample pretreatment. As shown by a combination of the 31P MAS NMR and 1H MAS NMR techniques with trimethylphosphine, not only Brønsted acid sites but also Lewis acid sites exist in the TS-1 zeolites. Moreover, TS-1 zeolite is more

Jianqin Zhuang; Zhimin Yan; Xiumei Liu; Xianchun Liu; Xiuwen Han; Xinhe Bao; Ulrich Mueller

2002-01-01

409

Synthesis of Hierarchical TS1 Zeolite from Silanized Seeds  

Microsoft Academic Search

Hierarchical TS-1 zeolites with a bimodal pore architecture, consisting of the typical MFI micropores and an additional mesoporosity,\\u000a have been synthesized by grafting an organosilane compound to the zeolitic seeds previously prepared from two different raw\\u000a materials: a liquid gel and an amorphous SiO2–TiO2 xerogel. These hierarchical TS-1 zeolites show an excellent catalytic behavior in olefin epoxidation reactions employing\\u000a organic

D. P. Serrano; R. Sanz; P. Pizarro; I. Moreno

2010-01-01

410

Zeolites are effective ROS-scavengers in vitro.  

PubMed

We report on the use of zeolites to limit the effects of reactive oxygen species (ROS) on human albumin under in vitro conditions. Zeolites of different structure type, channel size, channel polarity, and charge-compensating cation were screened for the elimination of ROS, notably HO(·), resulting from the Fenton reaction. A test based on ischemia-modified albumin (IMA) was used as a marker to monitor the activity of HO(·) after co-exposure of human serum to these zeolites. Two commercial zeolites, faujasite (FAU 13×, channel opening 0.74×0.74 nm with Na(+) as charge-compensating cation) and ferrierite (FER, channel opening 0.54×0.42 nm with H(+) as charge-compensating cation), were found to reduce IMA formation by more than 65% due to removal of HO(·) relative to reference values. It was established that partial ion exchange of the zeolites' respective charge-compensating cation vs. Fe(3+) implicated in the Fenton reaction plays a major role in HO(·) deactivation process. Moreover, our results show that no saturation of the respective zeolite active sites occurred. This is possible only when ROS are actively converted to water molecules within the zeolite void system, which generates H(+) ion transport. Because zeolites cannot be administered in blood, their use in medicine should be limited to extra corporeal circuits. Zeolites could be of use during cardiopulmonary bypass or hemodialysis procedures. PMID:21679693

Pellegrino, Perrine; Mallet, Bernard; Delliaux, Stéphane; Jammes, Yves; Guieu, Regis; Schäf, Oliver

2011-07-01

411

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

412

Coreactant-induced modifications of catalytic behavior in zeolitic systems  

SciTech Connect

The complex feed processing over zeolite catalysts, competitive reaction between the feed components results in observed rates and selectivities that cannot be predicted from pure component data alone. Hydroisomerization of paraffins over various Pt/zeolites in the presence of an aromatic cofeed is considered as an illustration. The aromatic affects paraffin reaction rates by occupying catalytic sites and perhaps also by partially blocking the pores. Analysis of Arrhenius plots helps in correlations of zeolite structure and the extent to which the paraffin reaction is affected. It is shown that the coreactant can induce selectivity to a zeolite that would otherwise not be shape selective.

Martin, A.M.; Chen, J.-K.; John, V.T. (Dept of Chemical Engineering, West Virginia Univ, Morgantown, WV (US))

1989-11-01

413

Method for the recovery of silver from silver zeolite  

DOEpatents

High purity silver is recovered from silver exchanged zeolite used to capture radioactive iodine from nuclear reactor and nuclear fuel reprocessing environments. The silver exchanged zeolite is heated with slag formers to melt and fluidize the zeolite and release the silver, the radioactivity removing with the slag. The silver containing metallic impurities is remelted and treated with oxygen and a flux to remove the metal impurities. About 98% of the silver in the silver exchanged zeolite having a purity of 99% or better is recoverable by the method.

Reimann, George A. (Idaho Falls, ID)

1986-01-01

414

Thermodynamic analysis of a solar zeolite refrigeration system  

SciTech Connect

A solar zeolite-water absorption refrigeration unit was studied. Thermodynamic expressions were derived to predict the system performance. The operating range and optimum design parameters for the zeolite system were determined. The main parameters governing performance were: solar collector type, ambient temperature, and absorber properties. Results are shown for various solar collector types and various zeolite types. A desorption initiation temperature is shown to exist. The analysis is not based on empirical heat of absorption data, but rather on a zeolite properties relationship (log P /SUB v/ versus 1/T /SUB z/ ) to determine system performance.

Chang, S.C.; Roux, J.A.

1985-08-01

415

LAYER-BY-LAYER ASSEMBLY OF NANOZEOLITE BASED ON POLYMERIC MICROSPHERE: ZEOLITE COATED SPHERE AND HOLLOW ZEOLITE SPHERE  

Microsoft Academic Search

Zeolite ?, silicalite-1, ZSM-5, and TS-1 coated spheres have been prepared successfully through layer-by-layer assembly of nanozeolite\\/polymer multilayers on polystyrene (PS) microspheres, and hollow zeolite spheres have been obtained by removal of the core by calcination. In the adsorption process of nanozeolites onto the polyelectrolyte-modified template spheres, it has been found that zeta potential of the zeolite colloidal solution that

Wuli Yang; Xingdong Wang; Yi Tang; Yajun Wang; Chen Ke; Shoukuan Fu

2002-01-01

416

Waveguides in Crystalline Materials  

NASA Astrophysics Data System (ADS)

Crystalline media offer a variety of unique properties, such as even order nonlinearities, birefringence, and broad transparency ranges, which make them of great interest for applications in integrated optics. However, the extension of femtosecond laser direct inscription techniques [Nolte et al., Appl. Phys. A 77, 109 (2003), J. Mod. Opt. 51, 2533 (2004); Itoh et al. MRS Bull. 31, 620 (2006); Gattass, Mazur, Nature 2, 219-225 (2008); Della Valle et al., J. Opt. A: Pure Appl. Opt. 11 (2009)] with their vast potential for the fabrication of buried three-dimensional structures of arbitrary shapes to crystals has proven to be a challenging task. Results achieved so far in direct writing of optical devices in crystals will be reviewed.

Heinrich, Matthias; Rademaker, Katja; Nolte, Stefan

417

Liquid crystalline polymers  

NASA Technical Reports Server (NTRS)

The remarkable mechanical properties and thermal stability of fibers fabricated from liquid crystalline polymers (LCPs) have led to the use of these materials in structural applications where weight savings are critical. Advances in processing of LCPs could permit the incorporation of these polymers into other than uniaxial designs and extend their utility into new areas such as nonlinear optical devices. However, the unique feature of LCPs (intrinsic orientation order) is itself problematic, and current understanding of processing with control of orientation falls short of allowing manipulation of macroscopic orientation (except for the case of uniaxial fibers). The current and desirable characteristics of LCPs are reviewed and specific problems are identified along with issues that must be addressed so that advances in the use of these unique polymers can be expedited.

1990-01-01

418

Crystalline Amorphous Semiconductor Superlattice  

NASA Astrophysics Data System (ADS)

A new class of superlattice, crystalline amorphous superlattice (CASL), by alternatively depositing two semiconductor materials, is proposed. CASL displays three states depending on the component materials’ phase: both polycrystalline phases, both amorphous phases, and one polycrystalline phase while another amorphous phase. Using materials capable of reversible phase transition, CASL can demonstrate reversibility among three states. GeTe/Sb2Te3 CASL has been synthesized and proved by x-ray reflectometry and TEM results. The reversible transition among three states induced by electrical and laser pulse was observed. The changes in the optical absorption edge, electrical resistivity, thermal conductivity, and crystallization temperature as a function of layer thickness are interpreted as quantum or nanoeffects. The unique properties of CASL enable the design of materials with specific properties.

Chong, T. C.; Shi, L. P.; Wei, X. Q.; Zhao, R.; Lee, H. K.; Yang, P.; Du, A. Y.

2008-04-01

419

Pf/Zeolite Catalyst for Tritium Stripping  

SciTech Connect

This report described promising hydrogen (protium and tritium) stripping results obtained with a Pd/zeolite catalyst at ambient temperature. Preliminary results show 90-99+ percent tritium stripping efficiency may be obtained, with even better performance expected as bed configuration and operating conditions are optimized. These results suggest that portable units with single beds of the Pd/zeolite catalyst may be utilized as ''catalytic absorbers'' to clean up both tritium gas and tritiated water. A cart-mounted prototype stripper utilizing this catalyst has been constructed for testing. This portable stripper has potential applications in maintenance-type jobs such as tritium line breaks. This catalyst can also potentially be utilized in an emergency stripper for the Replacement Tritium Facility.

Hsu, R.H.

2001-03-26

420

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

421

Electrical Response of PEDOT-PSS/FAU Zeolite Composites toward SO2: Controlling the Adsorption Properties of FAU Zeolite  

NASA Astrophysics Data System (ADS)

In our work, we propose to combine a conductive polymer, Poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonic acid) (PEDOT-PSS), with FAU zeolites to investigate the potential of the composites for use as SO2 sensing materials.Composites with PEDOT-PSS as a matrix containing faujasite zeolites of various cation types (divalent transition metal ions: Fe^2+, Co^2+, Ni^2+ and Cu^2+), were fabricated to investigate the effect of the cation type of the faujasite zeolites on the electrical conductivity response when exposed to SO2. The composite was tested through repeated sensing and recovery processes to investigate the reversibility and reproducibility. During the recovery process, the electrical conductivity of the composites were recovered, which proves that the sensing characteristics are repeatable. Responses and the interaction mechanism of the conductive polymer/zeolite composites were investigated. The composite with 20% (v/v) of zeolite content gives the highest sensitivity. The electrical conductivity responses of PEDOT-PSS/Zeolite composites can be altered due to the available adsorption sites for gas molecules. The addition of zeolites to the pristine PEDOT-PSS improved the electrical conductivity sensitivity of the composites by enhancing the interaction between PEDOT-PSS and SO2. The type of cation in the zeolite pores effected the sensitivity of the composites, depending on the acidity of the ion-exchanged zeolites.

Chanthaanont, Pojjawan; Sirivat, Anuvat

2012-02-01

422

Water splitting by titanium exchanged zeolite A  

Microsoft Academic Search

Analysis of the product resulting from the equilibration 25 g of zeolite A with 50 cc of unstirred 20% titanium chloride solution for 1 h at ambient temperature indicated that 75% of the potassium cations are replaced by titanium cations on the surface of the ¹\\/ââ in.-diameter Linde 3A particles; the cages probably remained intact since little aluminum leaching occurred.

Steven M. Kuznicki; Edward M. Eyring

1978-01-01

423

VS1 zeolite synthesized directly from silatrane  

Microsoft Academic Search

VS-1 zeolite was successfully synthesized using silatrane as the precursor via sol–gel processing and microwave heating methods. Various factors, which influence the product properties, were investigated, viz. water content, reaction temperature, sodium hydroxide concentration, and amount of vanadium loading. XRD, SEM, UV–visible and ESR were applied to characterize synthesized VS-1. Lower water content and higher temperature promote incorporation of vanadium

Phairat Phiriyawirut; Alexander M. Jamieson; Sujitra Wongkasemjit

2005-01-01

424

Solar energy application of natural zeolites  

Microsoft Academic Search

The utilization of solar energy for cooling is usually achieved by means of sorption-refrigeration cycles. However, the conventional cycles using ammonia-water or lithium bromide-water solutions are inefficient because of the low solution temperatures obtainable with solar radiation and the high condenser temperatures required by air-cooled condensers. Zeolites provide a unique opportunity for a solid-gas adsorption cooling system because of their

D. I. Tchernev

1978-01-01

425

Transformation of thiophenic compounds over HY zeolite  

Microsoft Academic Search

The transformation of thiophenic compounds (2-methylthiophene, 3-methylthiophene, 2-methylbenzothiophene and 3-methylbenzothiophene) was carried out in a fixed bed reactor at 350°C under atmospheric pressure in the presence of a HY zeolite with a Si\\/Al ratio equal to 16. All the reactants underwent both isomerization and disproportionation. The product selectivities obtained experimentally were rationalized on the basis of the calculated stabilities (B3LYP

F. Richard; T. Boita; M. Moreau; C. Bachmann; G. Pérot

2007-01-01

426

Transformation of thiophenic compounds over acidic zeolites  

Microsoft Academic Search

The transformation of thiophenic compounds (2-methylthiophene; 3-methylthiophene; 2,3-dimethylthiophene; 2,5-dimethylthiophene; 2-methylbenzothiophene; 3-methylbenzothiophene) was carried out over HY zeolite at 350°C under atmospheric pressure in a fixed bed reactor. The transformation of some of them was also carried out over H?, HZSM5 and H-mordenite (HMOR). In the presence of HY, all the reactants underwent both isomerization and disproportionation in various proportions depending

T. Boita; M. Moreau; F. Richard; G. Pérot

2006-01-01

427

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 Brønsted 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

428

Anchoring strategies for bimetallic species in zeolites  

SciTech Connect

We explore a new approach by introducing heterobinuclear organometallic compounds for linking catalytic functions to zeolite frameworks. With two different metals present, the complexes are being anchored to the support via one oxophilic metal, ligand exchange and catalytic reactions may proceed at the second metal center. Anchoring chemistry, thermal stability and reactivity of Me[sub 3]SnMn(CO)[sub 5] in zeolite NaY and acid forms of zeolite Y was studied with X-ray absorption spectroscopy (Sn, Mn edge EXAFS) and in-situ FTIR/TPD-MS techniques. Subsequently, the tin-cobalt complex Me[sub 3]SnCo(CO)[sub 4] has been a focus of detailed synthetic and spectroscopic studies. The reactivity of tricarbonyl (cyclopentadienyl) (trimethylstannyl) molybdenum in new mesoporous hosts has been explored. A recent development is the design of vanadium oxo species in different micro- and mesoporous hosts. These are of great interest for the selective reduction of nitrogen oxides by ammonia, and selective oxidation of different hydrocarbons, such as xylenes, olefines and alkanes. Combination analytical techniques used to probe local structural changes at the molecular level, include EXAFS (Extended X-Ray Absorption Fine Structure) spectroscopy utilizing synchrotron radiation, in situ FT-IR coupled to thermodesorption/MS, UV-NIR, and CCD Raman.

Bein, T.

1993-03-01

429

Characterization of active sites in zeolite catalysts  

SciTech Connect

This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Atomic-level details of the interaction of adsorbed molecules with active sites in catalysts are urgently needed to facilitate development of more effective and/or environmentally benign catalysts. To this end the authors have carried out neutron scattering studies combined with theoretical calculations of the dynamics of small molecules inside the cavities of zeolite catalysts. The authors have developed the use of H{sub 2} as a probe of adsorption sites by observing the hindered rotations of the adsorbed H{sub 2} molecule, and they were able to show that an area near the four-rings is the most likely adsorption site for H{sub 2} in zeolite A while adsorption of H{sub 2} near cations located on six-ring sites decreases in strength as Ni {approximately} Co > Ca > Zn {approximately} Na. Vibrational and rotational motions of ethylene and cyclopropane adsorption complexes were used as a measure for zeolite-adsorbate interactions. Preliminary studies of the binding of water, ammonia, and methylamines were carried out in a number of related guest-host materials.

Eckert, J. [Los Alamos National Lab., NM (United States); Bug, A. [Swarthmore Coll., PA (United States); Nicol, J.M. [MOLTECH (United States)] [and others

1997-11-01

430

Advanced NMR characterization of zeolite catalysts. Final technical report  

SciTech Connect

The effort described in this report involved a joint industry-university program between the Signal Research Center, Inc., and the University of Illinois, designed to advance the state of knowledge of zeolite catalyst characterization technology for application to zeolite catalysts useful in coal liquefaction related processes. The program involved the application of new and improved high resolution solid state nuclear magnetic resonance (NRM) techniques to the characterization of zeolite catalysts and other related microporous materials. The NMR experiments were performed in the state-of-the-art NMR laboratory at the University of Illinois. In this report the first comprehensive investigation of /sup 17/O NMR of A and Y zeolites by means of static, MASS and VASS (variable angle sample spinning) NMR techniques is presented. The determination of the /sup 17/O isotropic chemical shifts, nuclear quadrupole coupling constants and electric field gradient tensor asymmetry parameters provides valuable supplementary information on zeolite structure. As an extension of the /sup 17/O NMR investigation of zeolites, results for gallosilicates and for several aluminophosphate materials have also been obtained. The work presented in this study demonstrates the ability of using /sup 17/O NMR to observe chemical changes in the oxygen environment of zeolites. This has important implications for the study of zeolite based catalysts. Chemical modifications of catalysts, such as framework substitutions or ion exchange which are commonly used to modify zeolite catalyst activity can be directly studied for their effect on the oxygen rich surface of the zeolite. It is also possible that this technique could be used to directly probe the interactions between the zeolite surface and reactant molecules. 29 refs., 14 figs., 7 tabs.

Welsh, L.B.; Oldfield, E.

1986-03-01

431

Wetting of single crystal mullite by borosilicate and yttrium-aluminosilicate glasses and wetting phenomena of steels containing aluminum and titanium  

Microsoft Academic Search

This dissertation consists of two major sections. The first section concerns the wetting of single crystal mullite by borosilicate and yttrium-aluminosilicate glasses. The borosilicate glass showed poor wetting and interacted only moderately with the substrate. The yttrium-aluminosilicate glass interacted strongly with mullite and showed very good wetting. Balanced chemical equations between each glass and mullite were derived from EDS data.

Benjamin Todd Eldred

2004-01-01

432

Controlling crystal polymorphism in organic-free synthesis of Na-zeolites.  

PubMed

Controlling polymorphism is critical in areas such as pharmaceuticals, biomineralization, and catalysis. Notably, the formation of unwanted polymorphs is a ubiquitous problem in zeolite synthesis. In this study, we propose a new platform for controlling polymorphism in organic-free Na-zeolite synthesis that enables crystal composition and properties to be tailored without sacrificing crystal phase purity. Through systematic adjustment of multiple synthesis parameters, we identified ternary (kinetic) phase diagrams at specific compositions (i.e., Si, Al, and NaOH mole fractions) using colloidal silica and sodium aluminate. Our studies identify multiple stages of zeolite phase transformations involving the framework types FAU, LTA, EMT, GIS, SOD, ANA, CAN, and JBW. We report an initial amorphous-to-crystalline transition of core-shell particles (silica core and alumina shell) to low-density framework types and their subsequent transformation to more dense structures with increasing temperature and/or time. We show that reduced water content facilitates the formation of structures such as EMT that are challenging to synthesize in organic-free media and reduces the synthesis temperature required to achieve higher-density framework types. A hypothesis is proposed for the sequence of phase transformations that is consistent with the Ostwald rule of stages, wherein metastable structures dissolve and recrystallize into more thermodynamically stable structures. The ternary diagrams developed here are a broadly applicable platform for rational design that offers an alternative to time- and cost-intensive methods of ad hoc parameter selection without a priori knowledge of crystal phase behavior. PMID:23265176

Maldonado, Miguel; Oleksiak, Matthew D; Chinta, Sivadinarayana; Rimer, Jeffrey D

2013-02-20

433

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

434

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

435

DuraLith Alkali-Aluminosilicate Geopolymer Waste Form Testing for Hanford Secondary Waste  

SciTech Connect

The primary objective of the work reported here was to develop additional information regarding the DuraLith alkali aluminosilicate geopolymer as a waste form for liquid secondary waste to support selection of a final waste form for the Hanford Tank Waste Treatment and Immobilization Plant secondary liquid wastes to be disposed in the Integrated Disposal Facility on the Hanford Site. Testing focused on optimizing waste loading, improving waste form performance, and evaluating the robustness of the waste form with respect to waste variability.

Gong, W. L.; Lutz, Werner; Pegg, Ian L.

2011-07-21

436

Water solubility in aluminosilicate melts of haplogranite composition at 2 kbar  

Microsoft Academic Search

Holtz, F., Behrens, H., Dingwell, D.B. and Taylor, R.P., 1992. Water solubility in aluminosilicate melts of haplogranite composition at 2 kbar. In: Y. Bottinga, D.B. Dingwell and P. Richet (Guest-Editors), Silicate Melts. Chem. Geol., 96: 289-302. The compositional dependence of H20 solubility was investigated at 2 kbar and 800 °C in haplogranite melts (system SiO2-NaAISi3Os-KA1Si308 or Qz-Ab-Or). The sixteen investigated

F HOLTZ; H BEHRENS; D DINGWELL; R TAYLOR

1992-01-01

437

Two-photon holographic recording in aluminosilicate glass containing silver particles.  

PubMed

Recording of holographic gratings by 532-nm laser pulses in photochromic bulk aluminosilicate glass containing silver particles is demonstrated. A diffraction efficiency of 1.5% is achieved for readout at the same wavelength. The speed of grating formation as a function of pulse energy suggests that two-photon excitation is responsible for the recording. The light causes bleaching of an absorption peak near 417nm, which corresponds to the excitation of surface plasmons on the silver, and broad darkening throughout the visible to the near infrared. A likely mechanism for the photochromic effect is discussed. PMID:18185721

Akella, A; Honda, T; Liu, A Y; Hesselink, L

1997-07-01

438

Index profile control using Li(+) for Na(+) exchange in aluminosilicate glasses.  

PubMed

Two new techniques for altering the gradient-index profile shape are presented using ion exchange of Li(+) for Na(+) in an aluminosilicate glass. By varying the alkali concentration in the base glass and salt melt, the functional form of the index profile is modified to range in shape from convex to concave. The success of these techniques is attributed to the unusual characteristics of the initial system, which are shown to be caused by a nonlinear dependence of refractive index on dopant concentration. PMID:20577344

Haun, N; Kindred, D S; Moore, D T

1990-10-01

439

Evidence of two erbium sites in standard aluminosilicate glass for EDFA.  

PubMed

Site distributions of Er(3+)-doped aluminosilicate preforms of standard EDFA were studied by the low temperature Resonant Fluorescence Line Narrowing (RFLN) spectroscopy. Two erbium concentration samples with the same glass base were investigated. At very low erbium concentration, two classes of sites were identified, related to the number of AlO(6) octahedral linked by two oxygen edge-sharing to Er(3+) in the coordination sphere. As erbium concentration is increased, the high AlO(6) coordinated class of sites is smeared out by the optical response of the one AlO(6) coordinated class of sites. PMID:20940961

Peretti, R; Jurdyc, A M; Jacquier, B; Burov, E; Pastouret, A

2010-09-27

440

Long fluorescence lifetime of Ti3+-doped low silica calcium aluminosilicate glass.  

PubMed

This Letter reports the formation of Ti3+ in OH- free aluminosilicate glass melted under vacuum condition, with a very long lifetime (170 micros) and broad emission band shifted towards the visible region. This lifetime value was attributed to the trapping of the excited electrons by the glass defects and detrapping by thermal energy, and it is 2 orders of magnitude higher than those published for Ti3+ doped materials. Our results suggest that this glass is a promising system to overcome the challenge of extending the spectral range of traditional tunable solid state lasers towards the visible region. PMID:18232921

Andrade, L H C; Lima, S M; Novatski, A; Udo, P T; Astrath, N G C; Medina, A N; Bento, A C; Baesso, M L; Guyot, Y; Boulon, G

2008-01-18

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