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1

An ordered mesoporous aluminosilicate with completely crystalline zeolite wall structure.  

PubMed

An ordered mesoporous aluminosilicate with completely crystalline zeolite pore wall structure, denoted as OMZ-1, was successfully synthesized by recrystallization of SBA-15 using in situ formed CMK-5 as the hard template. The role of carbon material not only serves as a hard template to preserve ordered mesoporous structure but also kinetically controls the crystallization process to form large crystals. PMID:16910631

Fang, Yunming; Hu, Haoquan

2006-08-23

2

Structured carbon adsorbents from clay, zeolite and mesoporous aluminosilicate templates  

Microsoft Academic Search

Porous carbons templated from inorganic materials such as zeolites and mesoporous molecular sieves received considerable attention in the last decade. In this context, we discuss the effects of different templating structures on the carbons yielded. We describe templating using a commercial cationic clay (Wyoming bentonite), a commercial zeolite (Tosoh H-Beta) and a synthetic mesoporous aluminosilicate (Al-MCM-48), as exemplars of the

P. M Barata-Rodrigues; T. J Mays; G. D Moggridge

2003-01-01

3

Novel process for the preparation of ZSM-5 aluminosilicate zeolite  

Microsoft Academic Search

A method of manufacture of ZSM-5 aluminosilicate zeolite is described which consists of crystallizing, at a temperature of from about 185°C to about 250°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

Winquist; B. H. C

1989-01-01

4

Granulation of zeolite-containing aluminosilicate hydrogel  

SciTech Connect

The granulation of aluminosilicate hydrogel as an intermediate for the synthesis of cracking catalysts was investigated from the standpoint of eliminating the splitting cone from the granulator and eliminating coagulation directly on the cone surface. A method for forming the gel without a cone was developed by dispersion of jets of sol issuing directly from the mixer. Gel quality was considerably higher in dispersions of time-constant jets of the sol. The experimental mixer can be used as a design basis for a multijet granulator with a capacity equivalent to one or several splitting cones in commercial units.

Galimov, Z.F.; Vinkel'man, A.P.

1987-09-01

5

Investigation of the physicochemical changes preceding zeolite nucleation in a sodium-rich aluminosilicate gel.  

PubMed

All industrially available zeolites are obtained from hydrogel systems. Unfortunately the level of understanding of the events preceding zeolite crystallization is far from satisfactory. In this respect, revealing the nature of the processes taking place in the precursor gel is of paramount importance to understanding zeolite nucleation. The investigation of the gel structure, however, is a difficult task due to the complexity of the object in terms of both composition and topology. Therefore, a combination of hyperpolarized (HP) (129)Xe NMR-N(2) adsorption-high-resolution transmission electron microscopy-energy-dispersive spectrometry methods complemented by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, and chemical analyses has been employed to study the changes in composition and structure of sodium hydroxide rich aluminosilicate gel yielding zeolite A. The role of each component in the system and the entire sequence of events during the induction, nucleation, and crystallization stages have been revealed. The high concentration of sodium hydroxide in the studied system has been found to control the size and structure of the gel particles in the beginning stage. During the initial polymerization of aluminosilicate species a significant part of the sodium hydroxide is expelled from the gel into the solution, which restricts extensive polymerization and leads to formation of small aluminosilicate particles with open pore structure. The induction period that follows is marked by incorporation of Na back in the bulk gel. The combined action of the Na ion as a structure-directing agent and the hydroxyl group as a mobilizer results in partial depolymerization of the gel and formation of voids with mesopore sizes. The nucleation maximum coincides temporally with development of pores with sizes in the range of 2-5 nm. The amorphous gel undergoes into crystalline zeolite only after these pores have disappeared and the chemistry of the gel has evolved to reach the stoichiometric zeolite composition. It was established unambiguously by high-resolution transmission electron microscopy and HP (129)Xe NMR that the nucleation of zeolite occurs in the solid part of the system and the succeeding crystallization commences only after the nuclei are released into the liquid, which is consistent with the autocatalytic mechanism. Also this investigation has demonstrated the unrivaled sensitivity of HP (129)Xe NMR that is capable of identifying presence of small amounts of crystalline zeolite material in amorphous medium with detection limit extending below 1 wt %. PMID:19572709

Itani, Lama; Liu, Yong; Zhang, Weiping; Bozhilov, Krassimir N; Delmotte, Luc; Valtchev, Valentin

2009-07-29

6

Application of sol-gel process to H-zeolite synthesis over amorphous aluminosilicate materials  

Microsoft Academic Search

The impregnation preparation of H-zeolite over amorphous aluminosilicate solids (cracking catalysts) is compared with new synthesis procedures based on sol-gel process. The characterization results show that the H-zeolite reacts with the intermediates of the amorphous aluminosilicate.

T. Lpez; P. Bosch; R. Gmez; E. Basaldella; A. Kikot; E. Pereyra

1991-01-01

7

Predicting large CO2 adsorption in aluminosilicate zeolites for postcombustion carbon dioxide capture.  

PubMed

Large-scale simulations of aluminosilicate zeolites were conducted to identify structures that possess large CO(2) uptake for postcombustion carbon dioxide capture. In this study, we discovered that the aluminosilicate zeolite structures with the highest CO(2) uptake values have an idealized silica lattice with a large free volume and a framework topology that maximizes the regions with nearest-neighbor framework atom distances from 3 to 4.5 . These predictors extend well to different Si:Al ratios and for both Na(+) and Ca(2+) cations, demonstrating their universal applicability in identifying the best-performing aluminosilicate zeolite structures. PMID:23137005

Kim, Jihan; Lin, Li-Chiang; Swisher, Joseph A; Haranczyk, Maciej; Smit, Berend

2012-11-12

8

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

9

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

10

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

11

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

PubMed

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. PMID:12417479

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

2002-11-01

12

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

13

Crystalline galliosilicate with the zeolite omega structure  

SciTech Connect

This patent describes a process for preparing a crystalline, galliosilicate molecular sieve free of an organic templating agent and having the zeolite omega structure. It comprises mixing a hydrogel free of an organic templating agent and having the following oxide mole ratios of components: SiO{sub 2}/Ga{sub 2}O{sub 3} = 5 to 40, M{sub 2}O/Ga{sub 2}O{sub 3} = 2 to 10, H{sub 2}O/Ga{sub 2}O{sub 3} = 80 to 800 with a galliosilicate solution free of an organic templating agent and substantially free of alumina, the solution having the following oxide mole ratios of components SiO{sub 2}/Ga{sub 2}O{sub 3} = 5 to 30, M{sub 2}O/Ga{sub 2}O{sub 3} = 6 to 20, H{sub 2}O/Ga{sub 2}O{sub 3} = 200 to 800 to form a mixture of the hydrogel and the solution, wherein M is an alkali metal and the mixture has oxide mole ratios of components falling within the same ranges as the oxide mole ratios of components in the hydrogel; and crystallizing the mixture to form a galliosilicate molecular sieve free of an organic templating agent and having the zeolite omega structure.

Occelli, M.L.

1991-07-09

14

Secondary Ion Mass Spectrometry of Zeolite Materials: Observation of Abundant Aluminosilicate Oligomers Using an Ion Trap  

SciTech Connect

Oligomeric oxyanions were observed in the secondary ion mass spectra (SIMS) of zeolite materials. The oxyanions have the general composition AlmSinO2(m+n)H(m-1)- (m + n = 2 to 8) and are termed dehydrates. For a given mass, multiple elemental compositions are possible because (Al + H) is an isovalent and isobaric substitute for Si. Using 18 keV Ga+ as a projectile, oligomer abundances are low relative to the monomers. Oligomer abundance can be increased by using the polyatomic projectile ReO4- (~5 keV). Oligomer abundance can be further increased using an ion trap (IT-) SIMS; in this instrument, long ion lifetimes (tens of ms) and relatively high He pressure result in significant collisional stabilization and increased high-mass abundance. The dehydrates rapidly react with adventitious H2O present in the IT-SIMS to form mono-, di-, and trihydrates. The rapidity of the reaction and comparison to aluminum oxyanion hydration suggest that H2O adds to the aluminosilicate oxyanions in a dissociative fashion, forming covalently bound product ions. In addition to these findings, it was noted that production of abundant oligomeric aluminosilicates could be significantly increased by substituting the countercation (NH4+) with the larger alkali ions Rb+ and Cs+. This constitutes a useful tactic for generating large aluminosilicate oligomers for surface characterization and ion-molecule reactivity studies.

Groenewold, Gary Steven; Kessinger, Glen Frank; Scott, Jill Rennee; Gianotto, Anita Kay; Appelhans, Anthony David; Delmore, James Edward

2000-12-01

15

Case Series Describing Thermal Injury Resulting From Zeolite Use for Hemorrhage Control in Combat Operations.  

National Technical Information Service (NTIS)

Four cases are presented to illustrate cutaneous burns sustained with the use of zeolite in the treatment of major hemorrhage secondary to combat wounds. Zeolite, a microporous crystalline aluminosilicate granular hemostatic agent, can cause secondary the...

A. Pusateri J. McManus K. J. Knoop T. Hurtado

2007-01-01

16

Zealous zeolites  

SciTech Connect

Zeolites have made significant inroads in fluid cracking catalysts for gasoline and have pushed phosphates out of laundry detergents. But these crystalline aluminosilicate structures are just beginning to make their mark in chemical processes and environmental applications. Ideally suited for work as molecular sieves and catalysts, zeolites sport uniform surface pores and channels that are receptive only to molecules of a specific size and shape. This high selectivity makes zeolites a good alterative to some of the conventional products used for chemical reaction and filtration. One of the most potentially lucrative markets for zeolites is chemical catalyst replacements for liquid acids, such as hydrofluoric acid and sulfuric acid, and aluminum chloride in a number of alkylation and acrylation reactions. Zeolites are also being considered for oligomerization,isomerization, amination and condensation processes for the manufacture of chemical intermediates. The paper discusses the market and manufacturers of zeolites, justifying the cost of converting to zeolite catalysts, and natural zeolites.

Hairston, D.W.

1996-07-01

17

The mechanism of isobutane cracking over amorphous and crystalline aluminosilicates  

SciTech Connect

The acid catalyzed cracking of isobutane over a silica-alumina catalyst and several zeolites was studied. The activity of these catalysts, for whatever reason, increased in the order silica-alumina < H-ZSM-5 < H-Y < H-M, i.e., the same order found in a closely related study of neopentane. The higher the activity the lower was the temperature required to achieve a given conversion, the higher was the paraffin-to-olefin ratios, and the greater was the isomerization of iso- to normal hydrocarbons. It was demonstrated that with all these catalysts two primary reactions occurred resulting in the formation of CH{sub 4} and H{sub 2} and concomitantly the t-butyl and isopropyl cations. The latter either desorbed as the corresponding olefins or underwent secondary reactions. So long as the latter were relatively unimportant the C{sub 3} + C{sub 4} hydrocarbons formed nearly equaled the isobutane reacted. However, the sum of the CH{sub 4} and H{sub 2} produced was generally less than this values. Evidently hydrogen transfer is more important in the conversion of isobutane than of neopentane. This chemistry is discussed.

Lombardo, E.A.; Hall, W.K. (Univ. of Pittsburgh, PA (USA))

1988-08-01

18

Metal-supported aluminosilicate ultrathin films as a versatile tool for studying the surface chemistry of zeolites.  

PubMed

The application of a variety of "surface-science" techniques to elucidate surface structures and mechanisms of chemical reactions at zeolite surfaces has long been considered as almost impossible because of the poor electrical and thermal conductivity of those materials. Here, we show that the growth of a thin aluminosilicate film on a metal single crystal under controlled conditions results in adequate and well-defined model systems for zeolite surfaces. In principle, silicate films that contain metals other than Al (e.g. Ti, Fe, etc) may be prepared in a similar way. We believe that this approach opens up a new playground for experimental and theoretical modeling of zeolites, aimed at a fundamental understanding of structure-reactivity relationships in such materials. PMID:23143912

Shaikhutdinov, Shamil; Freund, Hans-Joachim

2012-11-09

19

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

2009-01-29

20

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 40 nm in the channel direction

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

1995-01-01

21

Hydrocarbon cracking with catalyst containing a CO oxidation promoter in ultra-stable zeolite particles  

Microsoft Academic Search

A cracking catalyst for promoting the oxidation of carbon monoxide to carbon dioxide during regeneration of the catalyst by the burning of coke therefrom, comprises two distinct crystalline aluminosilicate zeolite particles embedded in an inorganic porous oxide matrix material. The first zeolite is the ultra-stable variety of Y-type zeolite which contains a CO oxidation promoter, such as a Group VIII

Gladrow

1979-01-01

22

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

Microsoft Academic Search

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

David A. Lindquist; Alison L. Smoot

1997-01-01

23

Radiation and thermal effects on zeolites, smectites and crystalline silicotitanates  

NASA Astrophysics Data System (ADS)

Long-term radiation and thermal effects on materials in the near-field of a nuclear waste repository have been evaluated using accelerated laboratory experiments by energetic electron or ion beam irradiations. The materials studied include: zeolites, smectites, and crystalline silicotitanates (CST). In situ transmission electron microscopy (TEM) during irradiation by 200 keV electrons has shown that all of the studied materials are susceptible to radiation-induced amorphization. At room temperature, complete amorphization was observed after ionizing doses of 101010 12 Gy or displacement doses of 0.1 dpa. The critical amorphization dose increased with temperature for CST. A peak amorphization dose was found at 400C for the smectites. A new experimental approach was developed using a combination of proton irradiation, TEM, and electron microprobe analysis techniques to overcome the difficulties in studying the chemical properties in the radiation-damaged region. A clear correlation between the structural damage and changes in ion-exchange and desorption capacities has been established for zeolite-Y, which maybe useful for predicting the long-term behavior of the near-field materials in a nuclear waste repository. Radiation-induced decrease in the release rate of radionuclides has been observed for the first time in the damaged materials, indicating that the structural damage in near-field materials may be beneficial for retarding the release of radionuclides from geologic disposal repository into biosphere. Possible mechanisms for radiation-induced changes in structure, ion exchange and desorption capacities have been proposed.

Gu, Binxi

24

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

25

RBS and PIXE study of gallium depth profiling in ZSM-5 gallo-aluminosilicate zeolites  

NASA Astrophysics Data System (ADS)

Gallium concentration depth profiling in various as-synthesised and post-synthesis thermally treated Ga- and (Ga,Al)-ZSM-5 zeolites was quantitatively evaluated by RBS. This technique proved for the first time that Ga-ZSM-5 synthesised in the presence of methylamine involves a homogeneous Ga framework distribution. When both Al and Ga are present in the gel precursor, they form mixed complexes with methylamine and incorporate the zeolite lattice at different rates while some unreacted Ga-amino complex overcoats the outer rim of the crystals. Gallosilicates synthesised in the fluoride medium show a fairly homogeneous Ga incorporation with an increased Ga concentration on surface due to its overcoating by residual Ga fluoro complexes. Post-synthesis thermal treatments result in a partial degalliation of the framework that could be quantified by RBS. The nature, mobility and location of the extra framework Ga species markedly depend on the calcination conditions. A rapid calcination in dry conditions leads to the formation of extra framework Ga oxides that migrate towards the crystal core. Under milder heating, these species stay homogeneously partitioned within the crystal channels. Under a humid atmosphere, the extra framework Ga species migrate towards the crystal surface, the migration being enhanced by a partial reduction of Ga during non-oxidative treatments. Humid air treatment maintains the homogeneous distribution of both Ga2O3 and residual Ga3+ framework ions.

Gabelica, Zelimir; Demortier, Guy

1998-03-01

26

Fluorine-19 NMR Results on Crystalline Models for Fluoride Sites in Silicate and Aluminosilicate Glasses and Melts.  

NASA Astrophysics Data System (ADS)

As part of an ongoing effort to apply Fluorine-19 NMR to understanding the effects of fluoride on the structures and properties of silicate glasses and melts, the local environment of fluorine anions in several fluorosilicate and fluoroaluminate crystals and silicate glasses has been explored using F-19 MAS NMR. A compilation of this work with recent F-19 NMR chemical shift data has yielded several trends in the chemical shift. The chemical shift generally increases with the radius of the adjoining cation, which is qualitatively similar to the trends for oxygen anions in simple metal oxides and chlorine anions in crystalline chlorides. This effect was less pronounced in the fluoroaluminates and fluorosilicates (about 220 ppm from NaF to CsF versus about 60 ppm from Na2SiF6 to Cs2SiF6), implying that the strong bond to the Al or Si dominates the electron distribution around the fluorine anion. Another effect on the chemical shift was the coordination number of the fluorine, although it was difficult to establish a simple relationship between coordination number and chemical shift. In F-La(n) and F-Ca(n) sites (where "n" is the coordination number), increasing the coordination of the fluorine atom shifts the chemical shift to lower frequencies. In Na, Ca, and Ba fluoroaluminates, however, increasing coordination in Al-F-M(n) sites (where "M" is the coordinating cation) increases the chemical shift. The latter is also observed in Al-F-Al sites in Ba fluoroaluminates; as the number of coordinating Ba atoms increased, the position of peak maximum increased from -173 to -145.9 ppm. This may not have been due solely to the increasing coordination by Ba atoms, however, since the Al-F-Al bond angle decreases as the number of surrounding cations increases. Using this compilation of crystalline model compound F-19 peak positions, we were able to analyze spectra for several silicate and aluminosilicate glasses and identify the coordination environments of the fluorine anions. The major feature in the barium silicate glass spectrum is a broad peak (at -19 ppm) near that of crystalline BaF2 (-15 ppm). This implies that the Ba silicate glass contains a similar coordination environment as BaF2 (F-Ba(4)) but with a range of bond lengths and, possibly, coordination numbers. A low intensity shoulder at -131 ppm was attributed to the structural unit Si-F-Ba(n) due to its proximity to the Si-F-Ba(2) site in crystalline BaSiF6 ( -112 ppm). The main feature in the Ba aluminosilicate glass overlapped the ranges for Al-F-Ba(n), Si-F-Ba(n), and Al-F-Al structural units, so assignment of this peak to a particular structural unit is impossible. However, it is possible to say that this glass has a minimal amount of F-Ba(n) structural units. The studied Ca aluminosilicate glass contains a different fluorine environment than the Ba aluminosilicate. Our data for Ca aluminosilicate glass corroborates previous work on glasses of this composition, with the major feature of the spectrum (-152 ppm) within the observed range for Al-F-Ca(n) structural units (-143 to -154 ppm). There was also an unresolved shoulder centered at -126 ppm near the ranges of Si-F-Ca(n) (-123.4 to -134.5 ppm) and F-Ca(n) (-104 to -112.4 ppm) structural units. An additional intensity in the higher frequency spinning sidebands also suggests a considerable contribution from sites similar to those found in the Ca silicate glass (F-Ca(n) sites). The presence of F-M(n) sites in the Ca aluminosilicate but not in the Ba aluminosilicate suggests that the higher field strength cation can more effectively compete with Al cations for bonding with F anions. This supports previous conclusions about partial ordering of F anions around higher field strength cations.

Kiczenski, T. J.; Stebbins, J. F.

2001-12-01

27

Methodology for synthesizing crystalline metallosilicates with expanded pore windows through molecular alkoxysilylation of zeolitic lamellar precursors.  

PubMed

Postalkoxysilylation with diethoxydimethylsilane has been carried out on the zeolitic lamellar precursors of various topologies such as MWW, FER, CDO and MCM-47 aiming to construct new crystalline structures with expanded pore apertures between the layers. The silylation process and the crystalline and pore structures of the resulting materials have been investigated with the techniques of XRD, IR, (13)C and (29)Si MAS NMR, ICP, SEM, HRTEM, elemental analyses, and N 2 adsorption. In contrast to forming known three-dimensional zeolite structures after direct calcination of the lamellar precursors, the silylation led to new crystalline structures with opener pores, as evidenced by the shift of layer-related diffractions to the lower-angle region in XRD patterns and the enlarged interlayer pores found by HRTEM images. After optimizing the treatment conditions, particularly the amount of silane agent, a maximum and homogeneous silylation was realized, which guaranteed the phase purity in interlayer expanded zeolites. The expanded structures were well preserved after calcination at 823 K or reflux in water for 1 to 2 weeks, indicating a high thermal stability and also a hydrothermal stability. The interlayer expanded zeolites prepared from the metallosilicate precursors of MWW topology exhibited higher catalytic activities in the redox and solid acid-catalyzed reactions of bulky molecules than that of their counterparts with conventional MWW topology. PMID:18528990

Wu, Peng; Ruan, Juanfang; Wang, Lingling; Wu, LeiLei; Wang, Yong; Liu, Yueming; Fan, Weibin; He, Mingyuan; Terasaki, Osamu; Tatsumi, Takashi

2008-06-04

28

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

29

Mossbauer, infrared and magnetic characterization of iron/cobalt species in cage structure alumino-silicates (Zeolites)  

SciTech Connect

Magnetic, Mossbauer, and I.R. studies on S.P. (superparamagnetic) or M.D. (multidomain) particles of Fe and Co species dispersed in cage structure aluminosilicates in relation to syngas (CO+H/sub 2/) Fischer-Tropsch conversion are reported. The difference in the catalytic activity of such species has been shown to depend upon their degree of dispersion. The carbonyl impregnation gave ultra-fine S.P. Fe/sub 3/O/sub 4/, whereas the nitrate impregnation gave M.D. Fe/sub 3/O/sub 4/ or omicron-Fe/sub 2/O/sub 3/. The active Fe/sub 5/C/sub 2/ component was converted to Fe/sub 3/C during the above reaction.

Pannaparayil, T.; Lo, C.; Mulay, L.N.; Oskooie-Tabrizi, M.

1984-11-01

30

Nanoscale Encapsulation : The Structure of Cations in Hydrophobic Microporous Aluminosilicates  

Microsoft Academic Search

Hydrophobic microporous aluminosilicates created by the modification of zeolites and clays are currently being investigated as storage media for hazardous cations. Addition of an organic monolayer to the surface of an aluminosilicate after introduction of an ion into the zeolite or clay reduces the interaction of water with the material. The resuItant systems are approximately 20 times more resistant to

S. R. Wassew; S. E. Yuchs; D. Giaquinta; L. Soderholm; K. Song

1997-01-01

31

Synthesis and properties of crystalline silver nanoparticles supported in natural zeolite chabazite  

NASA Astrophysics Data System (ADS)

A simple, low-temperature, hydrothermal method for the synthesis of silver nanoparticles supported on the surfaces of the natural zeolite chabazite has been developed. The synthesis method includes two ion exchange processes: the first is a conditioning process to exchange the natural cations included in the chabazite tuff with NH4 ions, and the second exchanges the latter ions with silver. The precipitation of silver nanoparticles is achieved by thermal annealing of the silver-exchanged chabazite at 400 C for 1 h. The samples were studied with X-ray diffraction, Fourier-transform infrared spectroscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy and diffuse reflectance spectroscopy. The results show the presence of both silver cations and nanoparticles in the chabazite matrix, the silver nanoparticles being located at the surface of the chabazite microcrystals. The silver nanoparticles are crystalline with an average size of 8 nm and show cube-truncated shapes. The absorption spectra of the silver nanoparticles display several plasmon resonance transitions due to their geometry. The silver-supporting chabazite powders have bactericide properties against several types of bacteria as was shown by the inhibition of bacteria growth on conventional agar medium.

Flores-Lpez, N. S.; Castro-Rosas, J.; Ramrez-Bon, R.; Mendoza-Crdova, A.; Larios-Rodrguez, E.; Flores-Acosta, M.

2012-11-01

32

Directing zeolite structures into hierarchically nanoporous architectures.  

PubMed

Crystalline mesoporous molecular sieves have long been sought as solid acid catalysts for organic reactions involving large molecules. We synthesized a series of mesoporous molecular sieves that possess crystalline microporous walls with zeolitelike frameworks, extending the application of zeolites to the mesoporous range of 2 to 50 nanometers. Hexagonally ordered or disordered mesopores are generated by surfactant aggregates, whereas multiple cationic moieties in the surfactant head groups direct the crystallization of microporous aluminosilicate frameworks. The wall thicknesses, framework topologies, and mesopore sizes can be controlled with different surfactants. The molecular sieves are highly active as catalysts for various acid-catalyzed reactions of bulky molecular substrates, compared with conventional zeolites and ordered mesoporous amorphous materials. PMID:21764745

Na, Kyungsu; Jo, Changbum; Kim, Jeongnam; Cho, Kanghee; Jung, Jinhwan; Seo, Yongbeom; Messinger, Robert J; Chmelka, Bradley F; Ryoo, Ryong

2011-07-15

33

Catalytic dewaxing of oils containing ammonia over highly siliceous porous crystalline materials of the zeolite ZSM-5 type  

SciTech Connect

Straight-chain hydrocarbons and slightly branched chain hydrocarbons are selectively converted utilizing highly siliceous porous crystalline materials of the zeolite type having SiO/sub 2//Al/sub 2/O/sub 3/ ratio of greater than 200, unique molecular sieving properties and superior resistance to ammonia deactivation. The catalyst preferably contains acidic cations and can also contain a component having a hydrogenation/dehydrogenation function. The process of this invention is particularly useful for the dewaxing of hydrocarbon oils, including removal of high freezing point paraffins from jet fuel to lower freezing point, as well as improving the octane rating of naphtha fractions.

Dwyer, F.G.; Garwood, W.E.

1984-04-10

34

Adsorption of Dye from Wastewater by Zeolites Synthesized from Fly Ash: Kinetic and Equilibrium Studies  

Microsoft Academic Search

The removal performance of a basic dye, methylene blue (MB), in aqueous solution was investigated by adsorption process on single-phase and high-crystalline zeolite A (FA-ZA) and X (FA-ZX). Both adsorbents FA-ZA and FA-ZX were synthesized from fly ash prepared aluminosilicate gel followed by the hydrothermal treatment at 100C with the control of Si\\/Al molar ratio, respectively. The properties of the

Chunfeng WANG; Jiansheng LI; Lianjun WANG; Xiuyun SUN; Jiajia HUANG

2009-01-01

35

Diffusive characterization of large pore mesoporous materials with semi- crystalline zeolitic framework  

Microsoft Academic Search

Diffusion (kinetics) characterization of composite mesoporous materials that contain nano- zeolite particles in the mesoporous walls (UL-zeolite) is considered very important to further assess their potential as unique materials for separation and catalysis. Two different bimodal materials were investigated using two probe molecules, i.e., n-heptane and toluene of different kinetic diameter. Results showed varied behavior with respect to diffusion rates,

H. V. Thang; A. Malekian; M. Ei?; D. Trong On; S. Kaliaguine

2003-01-01

36

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

SciTech Connect

Solid-state 29Si, 27Al, and 23Na MAS (magic angle spinning) NMR techniques in combination with x-ray powder diffraction (XRD) are used to characterize aluminosilicate gels as a function of composition, pH, and reaction times. These gels were prepared at 80 C using initial solutions with low Si/Al ratios, high alkaline and salt concentrations that are characteristic of nuclear tank wastes. XRD data show that cancrinite and sodalite are the main crystalline phases in the aluminosilicate gels produced. It is found that the pH and the salt content have significant effects on the nature of the aluminosilicate gels. Higher pH appears to increase the rate of crystallization, the degree of overall crystallinity and the percentage of cancrinite phases in aluminosilicate gels, whereas the high salt concentration promotes the formation of cancrinite and sodalite and prohibits the formation of other zeolites. Complementary to XRD, NMR is extremely useful for providing the information on the structure of amorphous intermediate gels with no long-range order.

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

2005-11-01

37

Evaluation of Uranium Coprecipitation with Sodium Aluminosilicate Phases  

SciTech Connect

Batch laboratory experiments performed to evaluate uranium incorporation into aluminosilicate structures during synthesis are described. This research was conducted in response to plant problems related to the accumulation of uranium with aluminosilicates in low-level radioactive waste evaporators. Conditions that favor precipitation of aluminosilicates also foster uranium solid precipitation, so it is difficult to attribute problems with uranium accumulation to, for example, only the formation of the aluminosilicates. Infrared spectra show that sodium uranates, uranium silicates, and other uranium solids are formed during the synthesis of sodium aluminosilicates structures in the presence of uranium. Both amorphous and sodalite aluminosilicate phases, unlike the zeolite A phase, show appreciable affinity for uranium incorporation during their formation in the presence of uranium.

Oji, Lawrence N.; Williams, Adrienne L. [Westinghouse Savannah River Company (United States)

2004-02-15

38

Zeolites US market to reach $1 billion by 2000  

SciTech Connect

This article describes the growth of the U.S. market for zeolites, specifically sodium aluminosilicate. The largest application for zeolites is for petrochemical and petroleum catalysts; however, detergents are also a specific application addressed in the article.

Morris, G.D.L.

1997-02-05

39

Catalytic properties of crystalline titanium silicalites. 1. Synthesis and characterization of titanium-rich zeolites with MFI structure  

SciTech Connect

Crystalline titanium silicalites with the MFI structure and high titanium content (Si/Ti{double bond}10) have been prepared using improved synthesis procedures. The monoclinic lattice symmetry of silicalite-1 changes to orthorhombic on introduction of titanium. The titanium silicalites retain their orthorhombic symmetry even after calcination in air. On progressive incorporation of titanium, (1) the unit cell dimensions and volume (from XRD) increase linearly, (2) the crystal size decreases progressively, (3) the intensity of the framework IR band at 960 cm{sup {minus}1} increases, (4) a band around 47,000 c{sup {minus}1} appears in the electronic spectra due to charge transfer transitions involving Ti(IV) sites, (5) the hydrophilicity of the zeolite (from water adsorptions measurements) increases, (6) the adsorption capacity for cyclohexane increases, (7) the {sup 29}Si MAS NMR lines exhibit progressive broadening, and finally (8) the catalytic activity in the hydroxylation of phenol to catechol and hydroquinone also increases markedly. Based on these observations, it is concluded that a significant fraction of titanium in these samples is situated in framework positions. The catalytic properties of these well-defined titanium-modified zeolites will be described in more detail in the subsequent parts of this series.

Thangaraj, A.; Kumar, R.; Mirajkar, S.P.; Ratnasamy, P. (National Chemical Lab., Pune (India))

1991-07-01

40

Zeolite catalysis  

SciTech Connect

This patent describes a process for preparing hydrocarbons boiling in the gasoline and/or distillate range by contacting a feedstock comprising lower molecular weight olefins in a reaction zone under conditions of elevated temperature and pressure with a shape selective crystalline aluminosilicate catalyst, comprising: reducing the non-shape selective surface-cracking and/or surface isomerization activity of the aluminosilicate catalyst by a process comprising: preparing an aqueous solution comprising colloidal silica, optionally an organic directing agent, and a source of hydroxide ions; mixing the aqueous solution with an aqueous dispersion of shape-selective crystalline aluminosilicate to form a homogeneous mixture which is subsequently heated; adding an aqueous solution comprising a source of fluoride ions to the homogeneous mixture to form a reactive composition; heating the reactive composition at a temperature to effectively form a surface-deactivated catalyst comprising a crystalline fluoride-containing silica outer shell on an aluminosilicate; withdrawing the surface-deactivated catalyst from the reactive composition for washing, drying, and calcining of the catalyst; and removing the catalyst to the reaction zone for contact with the olefin feedstock.

Chu, P.; Garwood, W.E.; Schwartz, A.B.

1988-11-29

41

Chemically feasible hypothetical crystalline networks.  

PubMed

Our systematic enumeration of 4-connected crystalline networks (that is, networks in which each atom is connected to exactly four neighbours) used recent advances in tiling theory to evolve over 900 topologies. The results are relevant to the structures of zeolites and other silicates, aluminophosphates (AlPOs), oxides, nitrides, chalcogenides, halides, carbon networks, and even to polyhedral bubbles in foams. Given their importance as molecular sieves, ion exchangers, catalysts and catalyst supports, we have applied the results to microporous aluminosilicates and aluminophosphates (zeolites). Zeolite chemistry has to date produced 152 distinct types of structure. However, it was always clear that although many further structures can be synthesised, only a fraction of the mathematically generated networks would be chemically feasible (many are 'strained' frameworks requiring unrealistic bond lengths and bond angles), and that an effective 'filtering' process is needed to identify the most plausible frameworks. Here, we describe the use of computational chemistry methods to calculate optimized structural parameters, framework energies relative to alpha-quartz, volumes accessible to sorption, and X-ray diffraction patterns for systematically enumerated hypothetical 4-connected crystalline frameworks. Structures were treated as silica polymorphs with the empirical formula SiO(2), and their energies were minimized. PMID:15048108

Foster, Martin D; Simperler, Alexandra; Bell, Robert G; Friedrichs, Olaf Delgado; Paz, Filipe A Almeida; Klinowski, Jacek

2004-03-28

42

Determination of the bulk modulus of hydroxycancrinite, a possible zeolitic precursor in geopolymers, by high-pressure synchrotron X-ray diffraction  

Microsoft Academic Search

Crystalline zeolitic materials, such as hydroxycancrinite, hydroxysodalite, herschelite and nepheline, are often synthesized from geopolymerization using fly-ash and solutions of NaOH at high temperatures. Comprised mainly of 6-membered aluminosilicate rings that act as basic building units, their crystal structures may provide insight into the reaction products formed in NaOH-activated fly ash-based geopolymers. Recent research indicates that the hydroxycancrinite and hydroxysodalite

Jae Eun Oh; Simon M. Clark; Paulo J. M. Monteiro

2011-01-01

43

Methyl rotational tunneling dynamics of p-xylene confined in a crystalline zeolite host  

NASA Astrophysics Data System (ADS)

The methyl rotational tunneling spectrum of p-xylene confined in nanoporous zeolite crystals has been measured by inelastic neutron scattering (INS) and proton nuclear magnetic resonance (NMR), and analyzed to extract the rotational potential energy surfaces characteristic of the methyl groups in the host-guest complex. The number and relative intensities of the tunneling peaks observed by INS indicate the presence of methyl-methyl coupling interactions in addition to the methyl-zeolite interactions. The INS tunneling spectra from the crystals (space group P212121 with four crystallographically inequivalent methyl rotors) are quantitatively interpreted as a combination of transitions involving two coupled methyl rotors as well as a transition involving single-particle tunneling of a third inequivalent rotor, in a manner consistent with the observed tunneling energies and relative intensities. Together, the crystal structure and the absence of additional peaks in the INS spectra suggest that the tunneling of the fourth inequivalent rotor is strongly hindered and inaccessible to INS measurements. This is verified by proton NMR measurements of the spin-lattice relaxation time which reveal the tunneling characteristics of the fourth inequivalent rotor.

Nair, Sankar; Dimeo, Robert M.; Neumann, Dan A.; Horsewill, Anthony J.; Tsapatsis, Michael

2004-09-01

44

Multiple minima hypersurfaces studies of aluminosilicate hydration  

NASA Astrophysics Data System (ADS)

Hydrothermal zeolite synthesis is a complex process that is difficult to analyze experimentally. In this work, the role of water as solvent on the formation of aluminate and aluminosilicate clusters is described by quantum chemical calculations. The multiple minima hypersurfaces approach was used. It combines quantum chemical Hamiltonians for the calculation of the internal energy with statistical modeling and formulae for the calculation of thermodynamic functions of association. The structures of most probable hydration clusters are proposed and some of their association properties are calculated. Ab initio and semiempirical calculations of the structures and relevant reactions of aluminate and aluminosilicate fragments were reported. The results could be employed for an interpretation of the aluminosilicate synthesis. Calculations demonstrate the importance of considering other than the deepest minimum structures, giving a significant role to consider entropy of association.

Prez-Badell, Yoana; Montero, Luis A.

45

Evaluation of Uranium Co-precipitations with Sodium Aluminosilicate Phases  

SciTech Connect

This paper describes batch laboratory experiments performed to evaluate uranium incorporation into aluminosilicate structures during synthesis. This research was conducted in response to plant problems related to the accumulation of uranium with aluminosilicates in low-level radioactive waste evaporators. We have found that conditions which favor precipitation of aluminosilicates also foster uranium solid precipitation, so it is difficult to attribute problems with uranium accumulation to say just the formation of the aluminosilicates. Infrared spectra shows that sodium uranates, uranium silicates and other uranium solids are formed during the synthesis of sodium aluminosilicates structures in the presence of uranium. Both amorphous and sodalite aluminosilcate phases, unlike zeolite A phase, show appreciable affinity for uranium incorporation during their formation in the presence of uranium.

Oji, L.N.

2003-06-24

46

Influence of aluminum content, crystallinity and crystallite size of zeolite Pd\\/H-ZSM-5 on the catalytic performance in the dehydroalkylation of toluene with ethane  

Microsoft Academic Search

Pd\\/H-ZSM-5 zeolites with different aluminum contents and nSi\\/nAl ratios between 11 and 122, different crystallinities and crystallite sizes, including a nanocrystalline sample, were used as catalysts in the dehydroalkylation of toluene with ethane to the isomeric ethyltoluenes. This reaction was chosen as an industrially relevant test reaction for the non-oxidative activation of light alkanes. The catalysts were physicochemically characterized using

Arne Bressel; Thomas Donauer; Sarah Sealy; Yvonne Traa

2008-01-01

47

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

48

Aluminosilicates as Carriers of Phosphate-accumulating Bacteria  

Microsoft Academic Search

Five different aluminosilicate materials: natural altered tuff, synthetic mordenite, ammonium-exchanged mordenite, synthetic perlite and zeolite A were used for the immobilisation of metabolically active P-accumulating bacteria A. ju- nii. After 24 h of bacterial cultivation in reactors containing different carriers, one part of the total cell population was immobilised onto the carriers by means of adsorptive growth while the other

Jasna Hrenovic; Darko Tibljas; Lavoslav Sekovanic

49

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

50

High temperature synthesis of high silica zeolite Y with good crystallinity in the presence of N-methylpyridinium iodide.  

PubMed

A novel synthetic route is designed, employing both high temperature and a nontoxic organic structure-directing agent (SDA), for the synthesis of high silica zeolite Y. The N-methylpyridinium used as an organic SDA is stable during the synthesis, and the high silica zeolite Y shows high hydrothermal stability and good catalytic performance, as well as excellent adsorptive properties. PMID:24087828

Zhu, Longfeng; Ren, Limin; Zeng, Shangjing; Yang, Chengguang; Zhang, Haiyan; Meng, Xiangju; Rigutto, Marcello; Made, Alexander van der; Xiao, Feng-Shou

2013-10-15

51

Comportamiento de zeolitas y arcillas en presencia de soluciones radioactivas. (Zeolites and clays behavior in presence of radioactive solutions).  

National Technical Information Service (NTIS)

Natural aluminosilicates have found application as selective ion exchangers for radioactive cations in liquid wastes. Co is a common constituent of liquid radioactive wastes. Two types of zeolites (Y zeolite, and natural mexican erionite), and two types o...

L. M. Carrera Garcia

1991-01-01

52

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

PubMed

Zeolites-microporous crystalline aluminosilicates-are widely used in petrochemistry and fine-chemical synthesis because strong acid sites within their uniform micropores enable size- and shape-selective catalysis. But the very presence of the micropores, with aperture diameters below 1 nm, often goes hand-in-hand with diffusion limitations that adversely affect catalytic activity. The problem can be overcome by reducing the thickness of the zeolite crystals, which reduces diffusion path lengths and thus improves molecular diffusion. This has been realized by synthesizing zeolite nanocrystals, by exfoliating layered zeolites, and by introducing mesopores in the microporous material through templating strategies or demetallation processes. But except for the exfoliation, none of these strategies has produced 'ultrathin' zeolites with thicknesses below 5 nm. Here we show that appropriately designed bifunctional surfactants can direct the formation of zeolite structures on the mesoporous and microporous length scales simultaneously and thus yield MFI (ZSM-5, one of the most important catalysts in the petrochemical industry) zeolite nanosheets that are only 2 nm thick, which corresponds to the b-axis dimension of a single MFI unit cell. The large number of acid sites on the external surface of these zeolites renders them highly active for the catalytic conversion of large organic molecules, and the reduced crystal thickness facilitates diffusion and thereby dramatically suppresses catalyst deactivation through coke deposition during methanol-to-gasoline conversion. We expect that our synthesis approach could be applied to other zeolites to improve their performance in a range of important catalytic applications. PMID:19741706

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

2009-09-10

53

Applications of NMR spectroscopy to the Study of Zeolite Synthesis.  

National Technical Information Service (NTIS)

NMR spectroscopy is a powerful technique for identifying the structure and concentration of silicate and aluminosilicate anions in gels and solution used for zeolite synthesis. A review is presented of the types of species that have been observed and the ...

A. T. Bell

1989-01-01

54

Microprobes aluminosilicate ceramic membranes  

DOEpatents

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

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

1993-01-01

55

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

NASA Astrophysics Data System (ADS)

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

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

2010-07-01

56

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

SciTech Connect

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

Grutzeck, Michael W.

2005-06-27

57

Ionic liquids and eutectic mixtures as solvent and template in synthesis of zeolite analogues  

Microsoft Academic Search

The challenges associated with synthesizing porous materials mean that new classes of zeolites (zeotypes)-such as aluminosilicate zeolites and zeolite analogues-together with new methods of preparing known zeotypes, continue to be of great importance. Normally these materials are prepared hydrothermally with water as the solvent in a sealed autoclave under autogenous pressure. The reaction mixture usually includes an organic template or

Emily R. Cooper; Christopher D. Andrews; Paul S. Wheatley; Paul B. Webb; Philip Wormald; Russell E. Morris

2004-01-01

58

Influence of the porous structure of zeolite-containing catalysts on their activity and selectivity. Zeolite-containing catalysts based on a Y zeolite  

SciTech Connect

The catalytic activity and selectivity of zeolite-containing catalysts based on zeolite CaY-78 and amorphous aluminosilicates with various compositions and porous structures in the conversion of n-hexane at 400/sup 0/C have been determined. The differences in the activity and selectivity of the zeolite in the zeolite-containing catalysts in comparison to the zeolite without a matrix have been attributed to the blocking of part of the zeolite by the matrix material and matrix-zeolite cation jumps, whose rate is influenced by the macroporous structure of the matrix. The activity and selectivity of such zeolite-containing catalysts with an inactive matrix are determined by the effects of a mixture of CaY zeolites with different cationic compositions.

Rosolovskaya, E.N.; Barsukov, O.V.

1985-10-01

59

Use of natural zeolite as a supplementary cementitious material  

Microsoft Academic Search

Natural zeolite, a type of frame-structured hydrated aluminosilicate mineral, is used abundantly as a type of natural pozzolanic material in some regions of the world. In this work, the effectiveness of a locally quarried zeolite in enhancing mechanical and durability properties of concrete is evaluated and is also compared with other pozzolanic admixtures. The experimental tests included three parts: In

Babak Ahmadi; Mohammad Shekarchi

2010-01-01

60

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

SciTech Connect

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

Dutta, Prabir K.

2001-09-30

61

Raman spectroscopic study of the synthesis of zeolite Y  

SciTech Connect

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

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

1987-04-23

62

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

63

Properties and applications of zeolites.  

PubMed

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

Rhodes, Christopher J

2010-01-01

64

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

2013-02-01

65

Splitting Aluminosilicates with Silicate Bacteria.  

National Technical Information Service (NTIS)

An experiment was conducted to demonstrate the ability of silicate bacteria to break down the aluminosilicate nucleus in soils and the subsequent liberation of potassium. The equipment and procedures used in the experiment are described along with the res...

M. I. Ternovskaya R. N. Blagodyr V. G. Aleksandrov

1973-01-01

66

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

67

Process for preparing silicon substituted zeolite compositions  

SciTech Connect

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

Skeels, G.W.

1991-02-26

68

A high-silica zeolite with a 14-tetrahedral-atom pore opening  

Microsoft Academic Search

ZEOLITES (microporous aluminosilicates) and related molecular sieves have found wide application as catalysts, sorbents and ion-exchange materials. New zeolites with large pores are much in demand1-4, and have been sought for several decades4-7. All known zeolites, both natural and synthetic, contain pores comprised of 12 or fewer tetrahedrally coordinated silicon or aluminium atoms (T-atoms), but several microporous aluminophosphates with wider

C. C. Freyhardt; M. Tsapatsis; R. F. Lobo; K. J. Balkus; M. E. Davis

1996-01-01

69

Production of high-density aviation fuels via novel zeolite catalyst routes. Final report, December 1985-May 1987  

SciTech Connect

The production of high density aviation fuels from reliable, domestic fossil fuel sources is of considerable importance to the United States Air Force. The production of high density aviation fuels can be achieved by a number of alternative process sequences, for example, shape selective cracking of normal paraffins from an appropriate boiling range fraction of a napthenic crude; saturation of an aromatic FCC cycle stock of the appropriate boiling range; saturation of an appropriate boiling range fraction from a hydrocracker recycle stream when the feed to the hydrotreater is aromatic in nature; synthesis of the appropriate boiling range aromatic species from oxygenates over crystalline aluminosilicates followed by hydrogenation of the aromatic species; and direct synthesis of the aromatic hydrocarbons from hydrogen and carbon monoxide over crystalline aluminosilicate-supported metal catalysis followed by hydrogenation of the aromatic species. This report summarizes a research program aimed at developing catalyst and processing concepts for the production of high density aviation turbine fuels via novel zeolite catalyst routes.

Hanson, F.V.

1989-10-23

70

Characterization of Uranium Solids Precipitated with Aluminosilicates  

SciTech Connect

At the Savannah River Site (SRS), the High-Level Waste (HLW) Tank Farms store and process high-level liquid radioactive wastes from the Canyons and recycle water from the Defense Waste Processing Facility. The waste is concentrated using evaporators to minimize the volume of space required for HLW storage. Recently, the 2H Evaporator was shutdown due to the crystallization of sodium aluminosilicate (NAS) solids (such as cancrinite and sodalite) that contained close to 10 weight percent of elementally-enriched uranium (U). Prior to extensive cleaning,the evaporator deposits resided on the evaporator walls and other exposed internal surfaces within the evaporator pot. Our goal is to support the basis for the continued safe operation of SRS evaporators and to gain more information that could be used to help mitigate U accumulation during evaporator operation. To learn more about the interaction between U(VI) and NAS in HLW salt solutions, we performed several fundamental studies to examine the mechanisms of U accumulation with NAS in highly caustic solutions. This larger group of studies focused on the following processes: co-precipitation/structural incorporation, sorption, and precipitation (with or without NAS), which will be reviewed in this presentation. We will present and discuss local atomic structural characterization data about U that has been co-precipitated with NAS solids (such as amorphous zeolite precursor material and sodalite) using X-ray absorption fine-structure (XAFS) spectroscopic techniques.

DUFF, MC

2004-01-09

71

In-situ growth of porous alumino-silicates and fabrication of nano-porous membranes  

Microsoft Academic Search

Feasibility of depositing continuous films of nano-porous alumino-silicates, primarily zeolites and MCM-41, on metallic and non-metallic substrates was examined with an aim to develop membranes for separation of gaseous mixtures and also for application as hydrogen storage material. Mesoporous silica was deposited in-side the pores of these nano-porous disks with an aim to develop membranes for selective separations. Our study

Pradeep Kodumuri

2009-01-01

72

Flexibility of ideal zeolite frameworks.  

PubMed

We explore the flexibility windows of the 194 presently-known zeolite frameworks. The flexibility window represents a range of densities within which an ideal zeolite framework is stress-free. Here, we consider the ideal zeolite to be an assembly of rigid corner-sharing perfect tetrahedra. The corner linkages between tetrahedra are hard-sphere oxygen atoms, which are presumed to act as freely-rotating, force-free, spherical joints. All other inter-tetrahedral forces, such as coulomb interactions, are ignored. Thus, the flexibility window represents the null-space of the kinematic matrix that governs the allowable internal motions of the ideal zeolite framework. We show that almost all of the known aluminosilicate or aluminophosphate zeolites exhibit a flexibility window. Consequently, the presence of flexibility in a hypothetical framework topology promises to be a valuable indicator of synthetic feasibility. We describe computational methods for exploring the flexibility window, and discuss some of the exceptions to this flexibility rule. PMID:20589266

Kapko, V; Dawson, C; Treacy, M M J; Thorpe, M F

2010-06-29

73

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

74

Adsorption, Diffusion and Reaction Studies of Hydrocarbons on Zeolite Catalysts  

Microsoft Academic Search

Zeolites are crystalline microporous materials that are widely applied as catalysts in industries like oil refining, basic petrochemistry and fine chemistry. The major benefit of the use of zeolites as catalysts lies in their unique microporous structures. However, in some cases the presence of micropores limits the catalytic performance of zeolites due to diffusion limitation. This is caused by the

Sander van Donk

2002-01-01

75

Structural characteristics of modified natural zeolite  

Microsoft Academic Search

Natural zeolite of Slovak provenience has been modified with magnetic nanoparticles at selected temperatures of 20, 50 and\\u000a 85C with the aim to enhance its sorption properties. The pore, surface and structural properties of zeolite\\/iron oxide composite\\u000a were characterized using nitrogen adsorption measurements, electron probe microanalysis and powder X-ray diffraction. The\\u000a crystallinity of the host zeolite was strongly influenced by

Annamria Mockov?iakov; Marek Matik; Zuzana Orolnov; Pavol Hudec; Erika Kmecov

2008-01-01

76

Water solubility in aluminosilicate melts  

Microsoft Academic Search

We have compiled water solubility data for a wide range of natural and synthetic aluminosilicate melts in a search for correlations between melt composition and solubility. The published data reveal some interesting systematics. For example, molar water solubility increases with decreasing silica content in binary and pseudobinary silicates, and much higher solubilities are associated with alkali systems compared to alkaline

Paul F. McMillan; John R. Holloway

1987-01-01

77

Synthesis, characterization and energetics of zeolites  

NASA Astrophysics Data System (ADS)

Zeolites are microporous aluminosilicates, and Al or Si can be substituted by other elements, such as Ge, Ga, or P. Zeolites have been studied for more than two hundred years, because of their wide application and importance in mineralogy and technology. With high acidity and special pore system, zeolite beta (IZA code BEA) receives much attention. In the dissertation, the formation and dehydration enthalpy of cation exchanged zeolite beta, Li/Na/K/Rb/Cs/Mg/Ca/Sr/Ba -BEA 14 (14 is the Si/Al ratio), Mg/Ca - BEA 4 (4 is the Si/Al ratio), were studied by high-temperature oxide melt solution calorimetry. From an energetic point of view, zeolites beta are less stable than other zeolites of similar Si/Al ratio and cation content. Their enthalpies of formation and dehydration become more endothermic with increasing average ionic potential of the cations in the channels. The unfavorable enthalpy of low silica Mg-BEA 4 and Ca-BEA 4 suggests a possible energy barrier in their direct synthesis. The formation and partial molar dehydration enthalpy of Li-BEA 3 and Na-BEA 3.67 are also investigated by high temperature calorimetry. The partial molar dehydration enthalpies are a linear function of water content. Molecular mechanics simulations explore the cation and water molecule positions in the framework at several water contents. Ga substitution is of great interest due to the special catalytic character of Ga zeolites and the directing agent effect of Ga atoms. The energetics of gallosilicate zeolites Ga-NaSOD, Ga-NaFAU, Ga-NaNAT, Ga-KNAT, Ga-KLTL and Ga-KTUN-1 were studied. The lattice parameters and adsorbed water content increase after Ga substitution of Al. Compared to analogous aluminosilicate zeolites, the gallosilicate zeolites have a similar dehydration enthalpy per mole of tetrahedra, but a less endothermic dehydration enthalpy per mole of water. The gallosilicate zeolites also have less exothermic formation enthalpies from oxide components. The energetics of Ga zeolites are further discussed in terms of Si/Ga ratio, framework density and cation effects.

Sun, Pingping

78

Template synthesis and characterization of mesoporous zeolites  

Microsoft Academic Search

Well-crystalline ZSM-5 and zeolite Y having uniform mesopores were synthesized with template route method using carbon aerogels of different mesoporosities. These mesoporous zeolites were characterized with X-ray diffraction, FT-IR spectroscopy, field emission scanning electron microscopy, and N2 adsorption. ZSM-5 having mesopore volume of 0.21cm3g?1 was obtained. Mesoporous ZSM-5 synthesized by heating at 423K for 96h was well-crystalline, which had mesopores

Yousheng Tao; H Kanoh; Y Hanzawa; K Kaneko

2004-01-01

79

Binding and catalytic reduction of NO by transition metal aluminosilicates  

SciTech Connect

The objective of this research is to provide the scientific understanding of processes that actively and selectively reduce NO in dilute exhaust streams, as well as in concentrated streams, to N{sub 2}. Experimental studies of NO chemistry in transition metal-containing aluminosilicate catalysts are being carried out with the aim of determining the chemical rules for NO reduction on non- precious metals. The catalysts supports chosen for this investigation are A and Y zeolites, mordenite, and monoliths based on cordierite. The supported transition metal cations that will be examined are principally the first row redox metals, e.g. Cr(II), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Cu(I). The reactions of interest are the reductions of NO by H{sub 2} CO, and CH{sub 4} as well as the disproportionation of NO.

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

1991-12-01

80

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

81

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

82

Calcium aluminosilicate glass corrosion by phosphoric acid  

Microsoft Academic Search

The corrosion rates of a series of calcium aluminosilicate and sodium calcium aluminosilicate glasses were determined in three phosphoric acids at several temperatures. The effect of temperature on corrosion rate was determined for one glass in 30 wt % HPO; an activation energy was determined as well. The glasses are virtually insoluble at silica concentrations of >55 wt % SiO

N. C. Thakore; T. J. Rockett

1980-01-01

83

Synthesis and characterization of a new zeolite of the offretite type  

SciTech Connect

Offretite is an hexagonal zeolite first discovered by Professor Gonnard in 1890 in amygdaloidal basalt at Mount Semiouse near Montbreson, France. Offretite has been synthesized by Rubin and Aiello and Barrer from aluminosilicate hydrogels in a TMA (tetramethylammonium)-KOH-NaOH mixed base system. Aiello and Barrer noted that this zeolite can be grown from gels in the presence of KOH-TMAOH but not in the presence of NaOH-TMAOH. Sand has shown that offretite can be synthesized without TMA-OH from NaOH-KOH solutions. The synthesis of offretite crystals always included the presence of potassium ions until fairly recently when Barrer and Sieber were able to crystallize this zeolite from a LiOH-CsOH-TMAOH containing hydrogel. It is the purpose of this paper to describe the Perrotta synthesis of a new zeolite of the offretite type crystallized from a potassium free, aluminosilicate hydrogel in the presence of Rb-TMA ions.

Occelli, M.L.; Perrotta, A.J.

1982-03-01

84

Dry gel conversion synthesis of shape controlled MFI type zeolite materials  

Microsoft Academic Search

Acid treated silica fibers, coming either from asbestos cord waste or calcium aluminosilicate glass, were engaged as reactants\\u000a to product MFI type zeolite fibers applying a dry gel conversion (DGC) type synthesis. The impact of amorphous silica fiber\\u000a shape and synthesis conditions on morphology of the final product was investigated. Enhanced zeolite nucleation and restricted\\u000a crystal growth are necessary to

Simone Goergen; Mohamed Ali Saada; Michel Soulard; Loc Rouleau; Jol Patarin

2010-01-01

85

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

86

Structural interpretations of aluminosilicate glasses  

NASA Astrophysics Data System (ADS)

This manuscript presents a theoretical analysis of the correlation between the bulk moduli and the structure of a series of multicomponent aluminosilicate glasses in terms of the bond compression model. The main parameters in the analysis were the computed elastic moduli, the average stretching-force constant and the average atomic ring size. These parameters were calculated for every glass series and for every glass composition. The results showed that the average force constant of these glasses increases and the elastic moduli decrease with the increase in the SiO2 content (pure covalent bonds). This behaviour was attributed to the decrease in the molar volume, and the role of both CaO and Al2O3. The average atomic ring size of the studied glasses are about two-thirds of pure SiO2, whilst the elastic moduli of pure SiO2 glass are about two thirds of these glasses.

Saddeek, Yasser B.

2005-06-01

87

Synthesis of NaY zeolite on preformed kaolinite spheres. Evolution of zeolite content and textural properties with the reaction time  

SciTech Connect

The synthesis of NaY zeolite was carried out on fired kaolinite microspheres. Changes in porosity, chemical composition, and crystallinity of the solid show zeolite growth on both internal and external microsphere surfaces. It was also observed that, as a consequence of the alkaline treatment, the SiO[sub 2]/Al[sub 2]O[sub 3] ratio in the solid diminishes prior to the appearance of the zeolite, but increases when the zeolite begins to crystallize.

Basaldella, E.I.; Bonetto, R.; Tara, J.C. (Centro de Investigacion y Desarrollo en Procesos Cataliticos, La Plata (Argentina))

1993-04-01

88

Decomposition of Aluminosilicates by Soil Bacteria.  

National Technical Information Service (NTIS)

The formation of many types of soils is accompanied by decomposition of aluminosilicates including feldspars and kaolinites. Such decomposition if usually attributed to the effect of acid soil solutions, even though the experimental data failed to yield a...

L. E. Novorossova N. P. Remezov N. N. Sushkina

1968-01-01

89

Activated cation motions in zeolites  

NASA Astrophysics Data System (ADS)

We apply a Monte Carlo technique specialized for the simulation of rare events to study the activated counterions motions in the aluminosilicate Na+-mordenite. Mean activation barriers are obtained from minimum energy paths calculated on realistic potential energy surfaces by using a Metropolis algorithm. Energy barriers for Na+ hops calculated for lattices with various Si/Al ratio are found in good agreement with the Na+ detrapping energies measured by thermally stimulated current spectroscopy. One shows that the dielectric activated motions of Na+ proceed between degenerated many-body ground states with different dipolar moment by either sequential or collective hopping motions. This provides a first microscopic description of dielectric relaxation measured in zeolites.

Maurin, G.; Devautour, S.; Henn, F.; Giuntini, J. C.; Senet, P.

2002-07-01

90

Pressure-dependent hydrogen encapsulation in Na[sub 12]-zeolite A  

SciTech Connect

The hydrogen encapsulation capacities of Na[sub 12]-zeolite A with respect to pressure ranging from 10 to 150 atm at an isotherm of 623 K were calculated and compared with experimentally measured values. For the calculation, the hydrogen gas molecules encapsulated in the zeolite A were treated as three-dimensional lattice gas distributed in the cavities which lie in the three-dimensional aluminosilicate lattice of the zeolite A. The results indicated that the lattice gas theory is good enough both quantitatively and qualitatively to predict the hydrogen encapsulation capacities. 13 refs., 3 figs., 1 tab.

Yoon, J.H. (Kyungpook Sanup Univ., Taegu (Korea, Republic of))

1993-06-03

91

Chemically feasible hypothetical crystalline networks  

Microsoft Academic Search

Our systematic enumeration of 4-connected crystalline networks (that is, networks in which each atom is connected to exactly four neighbours) used recent advances in tiling theory to evolve over 900 topologies. The results are relevant to the structures of zeolites and other silicates, aluminophosphates (AlPOs), oxides, nitrides, chalcogenides, halides, carbon networks, and even to polyhedral bubbles in foams. Given their

Martin D. Foster; Alexandra Simperler; Robert G. Bell; Olaf Delgado Friedrichs; Filipe A. Almeida Paz; Jacek Klinowski

2004-01-01

92

Synthesis and structure of zeolite ZSM-5: a Raman spectroscopic study  

SciTech Connect

The Raman spectra of the solution and solid phases present during various stages of ZSM-5 synthesis were examined by monitoring the vibrations of the tetrapropylammonium ion. It was found that this cation is trapped into the amorphous solid phase at the earliest stages of the synthesis in the all-trans configuration. Upon crystallization of the zeolite, there is a forced change in the conformation of the trapped tetrapropylammonium cation, such that it can fit into the zig-zag zeolite channels. The Raman spectra of the aluminosilicate zeolite framework is also distinct from other zeolites, such as A, X, and Y, and exhibits a band at 385 cm/sup -1/ characteristic of the five-membered building units of this zeolite.

Dutta, P.K.; Puri, M.

1987-07-30

93

Calcium aluminosilicate glass corrosion by phosphoric acid  

SciTech Connect

The corrosion rates of a series of calcium aluminosilicate and sodium calcium aluminosilicate glasses were determined in three phosphoric acids at several temperatures. The effect of temperature on corrosion rate was determined for one glass in 30 wt % H/sub 3/PO/sub 4/; an activation energy was determined as well. The glasses are virtually insoluble at silica concentrations of >55 wt % SiO/sub 2/ and show extreme solubility at silica concentrations <50 wt %. At the trsnsition composition, a silica-gel layer is formed on the surface.

Thakore, N.C.; Rockett, T.J.

1980-11-01

94

Formulation of cracking catalyst based on zeolite and natural clays  

SciTech Connect

Domestically manufactured cracking catalysts are based on a synthetic amorphous aluminosilicate matrix and Y zeolite. A multistage {open_quotes}gel{close_quotes} technology is used in manufacturing the catalysts. The process includes mixing solutions of sodium silicate and acidic aluminum sulfate, forming, syneresis, and activation of the beaded gel. In the manufacture of bead catalysts, the next steps in the process are washing, drying, and calcining; in the manufacture of microbead catalysts, the next steps are dispersion and formation of a hydrogel slurry, spray-drying, and calcining. The Y zeolite is either introduced into the alumina-silica sol in the stage of forming the beads, or introduced in the dispersion stage. With the aim of developing an active and selective cracking catalyst based on Y zeolite and natural clays, with improved physicomechanical properties, the authors carried out a series of studies, obtaining results that are set forth in the present article.

Aliev, R.R.; Lupina, M.I.

1995-11-01

95

Molecular simulations and experimental studies of zeolites  

NASA Astrophysics Data System (ADS)

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

Moloy, Eric C.

96

Catalytic dewaxing of light and heavy oils in dual parallel reactors  

SciTech Connect

An integrated process is described for catalytically dewaxing relatively light petroleum chargestocks, comprising: contacting the relatively light petroleum chargestocks in the first dewaxing reactor with a crystalline aluminosilicate zeolite; simultaneously maintaining under regeneration conditions, in a second dewaxing reactor, a crystalline aluminosilicate zeolite; subsequently contacting the crystalline aluminosilicate zeolite in the second reactor with the relatively heavy petroleum chargestock; and hydrotreating the effluent from the first and second dewaxing reactors in a downstream hydrotreating reactor.

Chester, A.W.; Garwood, W.E.; Vartuli, J.C.

1989-03-07

97

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

98

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

2006-04-19

99

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

100

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

NASA Astrophysics Data System (ADS)

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

Beving, Derek Eugene

101

Microscopic and Spectroscopic Characterization of Aluminosilicate Waste Form with Cs/Sr/Ba Loading Using Scanning Electron Microscopy, Transmission Electron Microscopy, and X-Ray Diffraction  

NASA Astrophysics Data System (ADS)

An aluminosilicate waste form has been proposed for the storage and disposal of cesium and strontium isolated from recycled nuclear fuel. To examine the impact of sintering temperature on the waste form product, thermal analysis (thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC)) was used to identify key transition temperature ranges. Samples were produced in each temperature range to examine the impact on phase formation and microstructure. Examination of the synthesized materials by X-ray diffraction (XRD) confirmed the formation of the expected Cs- and Sr-aluminosilicate crystalline phases. However, microscopic characterization by scanning electron microscopy (SEM) revealed a spongelike, glassy morphology with high porosity and no observed crystallinity. This discrepancy was investigated by transmission electron microscopy (TEM) and high-resolution TEM (HRTEM), which identified the presence of discrete, submicron, crystalline phases within the bulk amorphous matrix. Elemental analysis by energy-dispersive X-ray (EDX) indicated that the strontium and barium were incorporated into the crystalline phase, while the cesium was incorporated into the amorphous matrix. Further analysis of samples synthesized without barium or strontium allowed for the identification of submicron crystalline phases within the amorphous matrix, identifying the source of the cesium aluminosilicate crystal peaks in the XRD patterns, with elemental analysis showing that the cesium was present in both the crystalline inclusions and the amorphous bulk phase.

Cerefice, Gary; Ma, Longzhou; Kaminski, Michael

2009-12-01

102

Characterization of Uranium Solids Precipitated with Aluminosilicates  

Microsoft Academic Search

At the Savannah River Site (SRS), the High-Level Waste (HLW) Tank Farms store and process high-level liquid radioactive wastes from the Canyons and recycle water from the Defense Waste Processing Facility. The waste is concentrated using evaporators to minimize the volume of space required for HLW storage. Recently, the 2H Evaporator was shutdown due to the crystallization of sodium aluminosilicate

M. C. Duff; D. B. Hunter; L. N. Oji; W. R. Wilmarth

2004-01-01

103

Thermal expansion of aluminosilicate refractory brick  

Microsoft Academic Search

¹ Thermal expansion measurements of 11 types of commercially available aluminosilicate refractory brick containing 31--93% ALO were made by dilatometry from room temperature to 1400°C. 2) The linear expansion coefficient correlates linearly with corundum content for high alumina brick containing greater than or equal to60% ALO. 3) Generally, reversible thermal expansion occurs before the start of softening, whereas irreversible thermal

K. J. Chen; H. Y. Chang; Y. C. Ko; T. F. Lee

1982-01-01

104

Flotation of aluminosilicate minerals using alkylguanidine collectors  

Microsoft Academic Search

The flotation mechanism of aluminosilicate minerals using alkylguanidine collectors was studied through flotation experiments, Zeta potential measurements and FT-IR spectrum analysis. It is shown that kaolinite, illite and pyrophyllite all exhibit good floatability with alkylguanidines as collectors at pH 412. The flotation recoveries rise with the increase of the carbon chain length. Isoelectric point(IEP) is determined to be 3.5, 3.0

Feng GUAN; Hong ZHONG; Guang-yi LIU; Sheng-gui ZHAO; Liu-yin XIA

2009-01-01

105

The structure of actinide ions exchanged into native and modified zeolites and clays  

SciTech Connect

X-ray absorption spectroscopy (XAS) has been used to investigate the structure and valence of thorium (Th{sup 4+}) and uranyl (UO{sub 2}{sup 2+}) cations exchanged into two classes of microporous aluminosilicate minerals: zeolites and smectite clays. XAS is also employed to examine the fate of the exchanged cations after modification of the mineral surface using self-assembled organic films and/or exposure to hydrothermal conditions. These treatments serve as models for the forces that ultimately determine the chemical fate of the actinide cations in the environment. The speciation of the cations depends on the pore size of the aluminosilicate, which is fixed for the zeolites and variable for the smectites.

Wasserman, S. R.; Soderholm, L.; Giaquinta, D. M.

2000-02-16

106

The effects of surface modification on the speciation of metal ions intercalated into aluminosilicates  

SciTech Connect

Microporous aluminosilicates, including clay minerals and zeolites, are ion-exchange materials. In their most common forms, they have the ability to incorporate cationic species within their matrices. Because of this property, microporous aluminosilicates have been proposed as storage media for hazardous waste. In this paper the authors use X-ray absorption spectroscopy (XAS) to examine the structure of cations held within smectite clay minerals and to determine how modification of the surface of the clay using an organic monolayer affects the coordination of the stored cation. The effects of hydrothermal and thermal processing on the coordination of the ions contained within these systems are also investigated. The presence of the monolayer changes the surface of the clay from hydrophilic to hydrophobic. It inhibits the interlayer ions from exchanging freely into environmental water and reduces the leach rate of cations out of the clay by approximately a factor of 20. Significant changes are observed when these coated samples are treated under hydrothermal and thermal conditions. Reductions of uranium (VI), in the form of uranyl, and cupric ions occur. In addition, the uranium aggregates, forming small particles that appear similar to UO{sub 2}. Comparable conglomeration occurs with lead cations and with the reduced copper species.

Wasserman, S.R.; Giaquinta, D.M.; Yuchs, S.E.; Soderholm, L. [Argonne National Lab., IL (United States). Chemistry Div.

1996-12-31

107

Isomerization of ?-pinene over dealuminated ferrierite-type zeolites  

Microsoft Academic Search

Isomerization of ?-pinene was performed on a series of dealuminated ferrierite (FER)-type zeolites in liquid phase at 363 K using a batch reactor. The course of zeolite dealumination was followed in detail using 29Si, 27Al, 1H MAS NMR, XRD, FTIR, and sorption of nitrogen. The ammonium form of FER was dealuminated with aqueous solutions of HCl. While retaining the crystallinity

Rafal Rachwalik; Zbigniew Olejniczak; Jian Jiao; Jun Huang; Michael Hunger; Bogdan Sulikowski

2007-01-01

108

Skeletal isomerization of 1?butene on synthetic clinoptilolite zeolite  

Microsoft Academic Search

A pure, highly crystalline clinoptilolite (CLI) zeolite with a Si\\/Al ratio of 5.8 has been synthesized using a small amount\\u000a (1%) of seed crystals and tested as a catalyst for the skeletal isomerization of 1?butene at 623723 K at atmospheric pressure.\\u000a The catalytic results are compared to those obtained from a ferrierite (FER) zeolite with a Si\\/Al ratio of 7.6.

Gon Seo; Byung Joon Ahn; Suk Bong Hong; Young Sun Uh

1998-01-01

109

Selective toluene disproportionation over pore size controlled MFI zeolite  

SciTech Connect

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

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

1994-02-01

110

Fluorine-19 NMR Study of the Environment of Fluorine in Silicate and Aluminosilicate Oxyfluoride Glasses.  

NASA Astrophysics Data System (ADS)

Using a compilation of F-19 NMR chemical shift values for crystalline model compounds, we have explored the local fluorine environment in several silicate and aluminosilicate oxyfluoride glasses. The F-19 MAS NMR spectrum of the Mg-silicate glass consists of a broad peak centered at -170 ppm, which encompasses the F-Mg(3) environments (where "3" is the number of Mg neighbors) of crystalline MgF2 (-195 ppm) and phlogopite (-175 ppm). The predominant environment in the glass is consequently assigned to F-Mg(n), where "n" indicates an unknown number of nearest neighbors. The magnesium aluminosilicate glass spectra all consist of a major feature at about -175 ppm and a shoulder at approximately -145 ppm. Based on the model compound data, the shoulder lies in the region attributed to Al-F-M2+ sites, and it was observed that glasses with a higher Al/Mg ratio featured extra intensity in the high-frequency shoulder. The shoulder is consequently assigned to Al-F-Mg(n), while the major feature is attributed to F-Mg(n) sites. This indicates that Mg is decidedly more effective in bonding to fluorine than either Ca or Ba in aluminosilicate glasses, following the trend established in our previous work on the Ba- and Ca-aluminosilicate glasses (the higher field strength modifier cation is more effective in competing with Al). Fluorine preferentially bonding with the modifier cation over aluminum has, to our knowledge, never been previously observed in aluminosilicate glasses. Spectra for Na-La-silicate glasses are characterized by an extremely wide peak (hundreds of ppm) and a relatively narrow peak at -220 ppm. The narrow peak at -220 ppm is assigned to F-Na(n) due to its proximity to the chemical shift of F-Na(6) (-225 ppm, from crystalline NaF). The small relative area of the F-Na(n) peak indicates a pronounced preference for F-La bonds over F-Na bonds, which is consistent with the findings of the previously discussed aluminosilicates. The massive, broad feature encapsulates the region described by the mixed fluorine environments of crystalline NaLaF4 (-30 to -63 ppm), and has therefore been assigned to a wide variety of fluorine environments, consisting of F-La bonds in a mixed environment with some number of F-Na bonds. In order to explore La-F clustering we have employed "echo" experiments, which can provide information about F-F distances. In the Na-La-silicates, the broad feature decays much faster than the F-Na(n) peak, indicating a shorter F-F distance in the sites associated with La. This is not consistent with random anion distribution but can be easily explained by the formation of fluorine-rich clusters. This may provide insight into the mechanism for the onset of crystallization in glass ceramics. In the long echo-time experiments on the Na-La-silicate glasses, the intensity of the broad feature was virtually gone, and the intensity of the F-Na(n) peak was largely decreased. This allowed us to clearly observe another peak centered at -140 ppm. This is near the peak found for the Si-F-Na(2) structure (-152 ppm) in the model compounds. Further examination of the original one-pulse spectra revealed the presence of this peak in small quantities in all compositions. Its relative intensity (about 2 percent of the total intensity) is comparable to that of Si-F-Ba(n) and Si-F-Na(n) bonding found in the fluorine containing Ba-silicate and Na-silicate glasses (respectively) from our previous studies. This suggests that Si-F bonding is independent of composition and may be an intrinsic characteristic of fluorine-containing silicate glasses.

Kiczenski, T. J.; Stebbins, J. F.

2002-12-01

111

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

Microsoft Academic Search

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

G. T. KOKOTAILO; C. A. FYFE

112

Viscoelastic characterisation of zeolite modified asphalt binder considering phase transformation and air void interaction  

Microsoft Academic Search

A recent warm mix asphalt technology uses zeolite powders as an additive to reduce production temperature and improve workability. With an increase in temperature, water is released from the zeolite crystalline structure and vaporised into bubbles within the binder, and thus gas, fluid, and solid phases simultaneously exist in the modified binders. The effective complex modulus of the modified binders

H. M. Yin; B. Lai

2012-01-01

113

Zeolite collapse and polyamorphism  

Microsoft Academic Search

The phenomenology of zeolite collapse is outlined, drawing on recent synchrotron x-ray diffraction experiments and computer simulations of low density cage structures like zeolite A and zeolite Y. Attention is drawn to the importance of polyamorphism in destabilizing this type of microporous crystal and its role in order disorder as well as amorphous amorphous transitions, together with associated differences in

G. Neville Greaves; F. Meneau; F. Kargl; D. Ward; P. Holliman; F. Albergamo

2007-01-01

114

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...

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

Double rotation NMR studies of zeolites and aluminophosphate molecular sieves  

SciTech Connect

Goal is to study the organization and structures of guest atoms and molecules and their reactions on internal surfaces within pores of zeolites and aluminophosphate molecular sieves. {sup 27}Al and {sup 23}Na double rotation NMR (DOR) is used since it removes the anisotropic broadening in NMR spectra of quadrupolar nuclei, thus increasing resolution. This work concentrates on probing aluminum framework atoms in aluminophosphate molecular sieves and sodium extra framework cations in porous aluminosilicates. In aluminophosphates, ordering and electronic environments of the framework {sup 27}Al nuclei are modified upon adsorption of water molecules within the channels; a relation is sought between the sieve channel topology and the organization of adsorbed water, as well as the interaction between the Al nuclei and the water molecules. Extra framework Na{sup +} cations are directly involved in adsorption processes and reactions in zeolite cavities.

Jelinek, R. [California Univ., Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley Lab., CA (United States)

1993-07-01

117

Computational studies of Bronsted acid sites in zeolites  

NASA Astrophysics Data System (ADS)

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 H2O 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.; Zygmunt, S. A.

1995-01-01

118

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

119

Plant Growth Experiments in Zeoponic Substrates: Applications for Advanced Life Support Systems.  

National Technical Information Service (NTIS)

A zeoponic plant-growth system is defined as the cultivation of plants in artificial soils, which have zeolites as a major component (Allen and Ming, 1995). Zeolites are crystalline, hydrated aluminosilicate minerals that have the ability to exchange cons...

C. Galindo D. J. Barta D. L. Henninger D. W. Ming J. E. Gruener K. E. Henderson S. L. Steinberg

2001-01-01

120

Zeolite catalysis: technology  

SciTech Connect

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

Heinemann, H.

1980-07-01

121

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

122

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

2010-10-01

123

Hydrated sodium calcium aluminosilicate: a high affinity sorbent for aflatoxin.  

PubMed

Aluminas, silicas and aluminosilicates were evaluated for their ability to sorb radiolabeled aflatoxin B1 (AFB1) from aqueous solution (in vitro). Hydrated sodium calcium aluminosilicate (HSCAS) was selected for testing in vivo due to its high affinity for AFB1, because of its stable association with AFB1, and its GRAS (generally recognized as safe) status as an anticaking agent. The HSCAS, when added to the diet of Leghorn and broiler chicks at a level of .5%, significantly diminished the adverse effects of feeding 7.5 mg AFB1/kg of feed. Thus, this agent (and other aluminosilicate congeners) may prove effective in the preventive management of aflatoxicosis. PMID:2837754

Phillips, T D; Kubena, L F; Harvey, R B; Taylor, D R; Heidelbaugh, N D

1988-02-01

124

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

SciTech Connect

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

Iton, L.E.; Brun, T.O.; Epperson, J.E. (Argonne National Lab., IL (USA). Materials Science and Technology Div.); Trouw, F. (Argonne National Lab., IL (USA). Intense Pulsed Neutron Source (IPNS) Program); White, J.W.; Henderson, S.J. (Australian National Univ., Canberra (Australia))

1988-03-01

125

Zeolite collapse and polyamorphism  

NASA Astrophysics Data System (ADS)

The phenomenology of zeolite collapse is outlined, drawing on recent synchrotron x-ray diffraction experiments and computer simulations of low density cage structures like zeolite A and zeolite Y. Attention is drawn to the importance of polyamorphism in destabilizing this type of microporous crystal and its role in order disorder as well as amorphous amorphous transitions, together with associated differences in entropy and density between polyamorphic phases and the precursor zeolite. Magic angle spinning NMR and inelastic x-ray scattering are used to highlight changes in structural order and mechanical rigidity between the starting zeolite and the final high density polyamorph. In conclusion, two-level systems detected with inelastic neutron scattering are described and their involvement in dictating the dynamics of the collapse of zeolitic cage structures.

Neville Greaves, G.; Meneau, F.; Kargl, F.; Ward, D.; Holliman, P.; Albergamo, F.

2007-10-01

126

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

127

Effect of high-pressures on the electrical resistivity of natural zeolites from Deccan Trap, Maharashtra, India  

Microsoft Academic Search

We report here the electrical resistivity measurements on two natural zeolitesnatrolite and scolecite (from the Killari borehole, Maharashtra, India) as a function of pressure up to 8 GPa at room temperature. High-pressure electrical resistivity studies on hydrous alumino-silicate minerals are very helpful in understanding the role of water in deep crustal conductivities obtained from geophysical models. The results obtained by

G. Parthasarathy

2006-01-01

128

Sodium clusters in zeolites  

NASA Astrophysics Data System (ADS)

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

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

1989-03-01

129

Binding and catalytic reduction of NO by transition metal aluminosilicates. Technical progress report, September 1991--November 1991  

SciTech Connect

The objective of this research is to provide the scientific understanding of processes that actively and selectively reduce NO in dilute exhaust streams, as well as in concentrated streams, to N{sub 2}. Experimental studies of NO chemistry in transition metal-containing aluminosilicate catalysts are being carried out with the aim of determining the chemical rules for NO reduction on non- precious metals. The catalysts supports chosen for this investigation are A and Y zeolites, mordenite, and monoliths based on cordierite. The supported transition metal cations that will be examined are principally the first row redox metals, e.g. Cr(II), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Cu(I). The reactions of interest are the reductions of NO by H{sub 2} CO, and CH{sub 4} as well as the disproportionation of NO.

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

1991-12-01

130

Investigation of aluminosilicate refractory for solid oxide fuel cell applications  

NASA Astrophysics Data System (ADS)

Stationary solid oxide fuel cells (SOFCs) have been demonstrated to provide clean and reliable electricity through electro-chemical conversion of various fuel sources (CH4 and other light hydrocarbons). To become a competitive conversion technology the costs of SOFCs must be reduced to less than $400/kW. Aluminosilicate represents a potential low cost alternative to high purity alumina for SOFC refractory applications. The objectives of this investigation are to: (1) study changes of aluminosilicate chemistry and morphology under SOFC conditions, (2) identify volatile silicon species released by aluminosilicates, (3) identify the mechanisms of aluminosilicate vapor deposition on SOFC materials, and (4) determine the effects of aluminosilicate vapors on SOFC electrochemical performance. It is shown thermodynamically and empirically that low cost aluminosilicate refractory remains chemically and thermally unstable under SOFC operating conditions between 800C and 1000C. Energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) of the aluminosilicate bulk and surface identified increased concentrations of silicon at the surface after exposure to SOFC gases at 1000C for 100 hours. The presence of water vapor accelerated surface diffusion of silicon, creating a more uniform distribution. Thermodynamic equilibrium modeling showed aluminosilicate remains stable in dry air, but the introduction of water vapor indicative of actual SOFC gas streams creates low temperature (<1000C) silicon instability due to the release of Si(OH)4 and SiO(OH) 2. Thermal gravimetric analysis and transpiration studies identified a discrete drop in the rate of silicon volatility before reaching steady state conditions after 100-200 hours. Electron microscopy observed the preferential deposition of vapors released from aluminosilicate on yttria stabilized zirconia (YSZ) over nickel. The adsorbent consisted of alumina rich clusters enclosed in an amorphous siliceous layer. Silicon penetrated the YSZ along grain boundaries, isolating grains in an insulating glassy phase. XPS did not detect spectra shifts or peak broadening associated with formation of new Si-Zr-Y-O phases. SOFC electrochemical performance testing at 800-1000C attributed rapid degradation (0.1% per hour) of cells exposed to aluminosilicate vapors in the fuel stream predominately to ohmic polarization. EDS identified silicon concentrations above impurity levels at the electrolyte/active anode interface.

Gentile, Paul Steven

131

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

132

Coating of silica sand with aluminosilicate clay.  

PubMed

The objective of this work was to coat aluminosilicate clays on an inert silica support, and to characterize the properties and stability of the clay-silica coating. Two polymers, polyacrylamide (PAM) and polyvinyl alcohol (PVA), were used to bind kaolinite, illite, and smectite onto silica grains. The clay-polymer composites were studied by X-ray diffraction, FTIR, and electrophoretic mobility. Clay coatings on silica grains were characterized by mass coverage, scanning electron microscopy, specific surface area, and pH stability. Silica sand was successfully coated with clays by using the two polymers, but with PVA, the clay coating had a greater mass coverage and was more stable against pH variations. Less polymer was needed for the clay coating using PVA as compared to using PAM. Clay-polymer complexes and pure clay minerals had similar cation exchange capacities and electrophoretic mobilities, indicating that overall surface charge of the clays was little affected by the polymers. Some decrease in hydrophilicity was observed for illite and smectite when clays where coated with the polymers. The methodology reported here allows the generation of a clay-based porous matrix, with hydraulic properties that can be varied by adjusting the grain size of the inert silica support. PMID:16085082

Jerez, Jorge; Flury, Markus; Shang, Jianying; Deng, Youjun

2005-08-08

133

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

134

Molecular chemistry in a zeolite: genesis of a zeolite Y-supported ruthenium complex catalyst.  

PubMed

Dealuminated zeolite Y was used as a crystalline support for a mononuclear ruthenium complex synthesized from cis-Ru(acac)2(C2H4)2. Infrared (IR) and extended X-ray absorption fine structure spectra indicated that the surface species were mononuclear ruthenium complexes, Ru(acac)(C2H4)2(2+), tightly bonded to the surface by two Ru-O bonds at Al(3+) sites of the zeolite. The maximum loading of the anchored ruthenium complexes was one complex per two Al(3+) sites; at higher loadings, some of the cis-Ru(acac)2(C2H4)2 was physisorbed. In the presence of ethylene and H2, 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)(C2H4)2(2+) species was dissociated and captured by an Al(3+) site. Ethylene dimerization proceeded approximately 600 times faster with a cofeed of ethylene and H2 than without H2. These results provide evidence of the importance of the cooperation of the Al(3+) sites in the zeolite and the H2 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. PMID:18785737

Ogino, Isao; Gates, Bruce C

2008-09-12

135

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

136

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

137

Selective sorption by zeolites  

SciTech Connect

An improved adsorptive separation process by the selective sorption properties of certain members of a novel class of zeolites is provided. The novel class of zeolites is characterized by a silica to alumina mole ratio greater than 12 and a Constraint Index within the approximate range of greater than 2 to about 12. The process of this invention involves selective separation of waxy paraffinic compounds in admixture with stocks containing paraffinic compounds, e.g. crude oils, heavy oils, distillate oils and lube base oils, by contacting the mixture with a zeolite having a SiO/sub 2//Al/sub 2/O/sub 3/ mole ratio of at least about 12 and a Constraint Index within the range of greater than 2 to about 12 to effect the selective sorption of said waxy paraffinic compounds by said zeolite.

Dessau, R.M.

1984-05-15

138

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

139

Zeolites for reforming catalysts  

Microsoft Academic Search

This patent describes a reforming catalyst exhibiting enhanced selectivity, activity, and activity maintenance. It comprises: zeolite crystals having a pH within the range of 9.4 to 10.0, wherein the pH is determined by measuring pH of supernatent liquid from a mixture of one part of the zeolite crystals with ten parts of dionized water by weight, and comprising exchangeable cations

J. L. Kao; M. Nadler; M. J. Potter; R. V. Martir

1991-01-01

140

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

141

Determining the aluminium occupancy on the active T-sites in zeolites using X-ray standing waves  

NASA Astrophysics Data System (ADS)

Zeolites are microporous crystalline materials that find wide application in industry, for example, as catalysts and gas separators, and in our daily life, for example, as adsorbents or as ion exchangers in laundry detergents. The tetrahedrally coordinated silicon and aluminium atoms in the zeolite unit cell occupy the so-called crystallographic T-sites. Besides their pore size, the occupation of specific T-sites by the aluminium atoms determines the performance of the zeolites. Despite its importance, the distribution of aluminium over the crystallographic T-sites remains one of the most challenging, unresolved issues in zeolite science. Here, we report how to determine unambiguously and directly the distribution of aluminium in zeolites by means of the X-ray standing wave technique using brilliant, focused X-rays from a third-generation synchrotron source. We report in detail the analysis of the aluminium distribution in scolecite, which demonstrates how the aluminium occupancy in zeolites can systematically be determined.

van Bokhoven, Jeroen A.; Lee, Tien-Lin; Drakopoulos, Michael; Lamberti, Carlo; Thie, Sebastian; Zegenhagen, Jrg

2008-07-01

142

In-situ growth of porous alumino-silicates and fabrication of nano-porous membranes  

NASA Astrophysics Data System (ADS)

Feasibility of depositing continuous films of nano-porous alumino-silicates, primarily zeolites and MCM-41, on metallic and non-metallic substrates was examined with an aim to develop membranes for separation of gaseous mixtures and also for application as hydrogen storage material. Mesoporous silica was deposited in-side the pores of these nano-porous disks with an aim to develop membranes for selective separations. Our study involves supported zeolite film growth on substrates using in-situ hydrothermal synthesis. Faujasite, Silicalite and Mesoporous silica have been grown on various metallic and non-metallic supports. Metallic substrates used for film growth included anodized titanium, sodium hydroxide treated Titanium, Anodized aluminum, and sintered copper. A non-metallic substrate used was nano-porous aluminum oxide. Zeolite film growth was characterized using Scanning Electron Microscope (AMRAY 1820) and High Resolution Transmission electron microscope. Silicalite was found to grow uniformly on all the substrates to form a uniform and closely packed film. Faujasite tends to grow in the form of individual particles which do not inter-grow like silicalite to form a continuous film. Mesoporous silica was found to grow uniformly on anodized aluminum compared to growth on sintered copper and anodized titanium. Mesoporous silica growth on AnodiscRTM was found to cover more than half the surface of the substrate. Commercially obtained AnodiscRTM was found to have cylindrical channels of the pore branching into each other and since we needed pore channels of uniform dimension for Mesoporous silica growth, we have fabricated nano-porous alumina with uniform pore channels. Nano-porous alumina membranes containing uniform distribution of through thickness cylindrical pore channels were fabricated using anodization of aluminum disks. Free-standing nano-porous alumina membranes were used as templates for electro-deposition in order to fabricate nickel and palladium nano-wire mesh with large surface area to volume ratio. Such nano-wire metallic alloy meshes have a strong potential for application as advanced hydrogen storage material. Statistical image analysis techniques were used to determine the dependence of the pore morphology and distribution on the crystal orientation by anodizing single crystal aluminum disks that were oriented with their surface normal along [111], [110] and [111] directions. The [100] oriented disks were found to have the highest tendency to anodize in oxalic acid electrolytic solutions.

Kodumuri, Pradeep

143

Acid zeolites as catalysts in organic reactions. tert-Butylation of anthracene, naphthalene and thianthrene  

Microsoft Academic Search

Liquid phase tert-butylation of anthracene, naphthalene and thianthrene to afford 2-tert-butyl plus 2,6- and 2,7-di tert-butyl derivatives were carried out at atmospheric pressure and moderate temperatures (below 100C) in the presence of a series of large pore zeolites and mesoporous aluminosilicates including HY-100 (Si\\/Al 2.6), HY-D1 (Si\\/Al 2.75), HY-D2 (Si\\/Al 15), H?, HMor and MCM-41. The activity increases from MCM-41

Elvira Armengol; Avelino Corma; Hermenegildo Garca; Jaime Primo

1997-01-01

144

Bromides in zeolite synthesis \\/ zeolites in bromide synthesis and conversion  

Microsoft Academic Search

Quaternary ammonium bromides and hydroxides (quats) are applied as templates in the synthesis of zeolites with relatively high Si\\/Al ratio. Examples will be given of the use of mon-, di-, poly- and associated quats as templates in zeolite growth. Templated zeolites of the MFI-type can be grown in a lateral or in an axial way onto metal supports, providing promising

H. Van Bekkum

1995-01-01

145

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

146

Structure of soda-lime aluminosilicate glasses  

NASA Astrophysics Data System (ADS)

The SiO2-CaO-Na2O-Al2O3 system is one of the most important in glass industry or geological processses but there have been relatively few structural studies in this system and, in particular, on the environment around non-network former cations (Na and Ca). Calcium and sodium in presence of alumina have a double structural role either as modifier, participating to the network depolymerization, or as charge compensator, near the (AlO4)- tetrahedra. The local and medium range environment may be affected by the structural role played in the network by these cations. Here we present experimental and simulation results on this system. We investigated several glasses to study the Si/Al substitution with a constant Na2O/CaO ratio, in order to determine the structural modifications between cations acting as pure modifiers and cations acting progressively as modifiers. Moreover, the Ca/Na substitution has been studied in silicate and aluminosilicate glasses to assess the effect of replacing Ca by Na. X-ray absorption data have been obtained at the Na and Ca K-edge at LURE (Orsay, France). XANES spectra indicate that the Ca environment in the studied glasses is close to the distorted site observed for c-anorthite, which corresponds to a coordination number of 6-7. A structural relaxation around Ca, with a decrease of the site distortion, is observed as SiO2 content increases. The two main peaks in the Na XANES spectra become broader as Na is replacing Ca. Conversely, the Si/Al substitution as little effect on both the Na and Ca XANES spectra. Raman spectra were collected with a T64000 spectrometer of Jobin-Yvon. When replacing Al by Si with constant Na2O/CaO ratio, a rapid decrease of the high frequency region (1100 cm-1) is observed. These decrease can be attributed to the substitution of Si by Al. The anionic units are Q4, Q3 and Q2 where tetrahedrally coordinated Al3+ is probably partitioned between these units. These experimental results are coupled with Molecular Dynamics simulations performed with Born-Mayer Huggins potentials and three body terms, in order to better assess the chemical dependence of the polymerized network and of the cations environment.

Cormier, L.; Neuville, D. R.

2003-04-01

147

Multicomponent aluminosilicate glasses: Structure and acid corrosion  

NASA Astrophysics Data System (ADS)

The structure, acid durability, and surface layer formation of two series of fully polymerized aluminosilicate glasses with (CaO+Na2O):(Al 2O3) molar ratios of unity were examined. In particular, the effects of varying the network composition (Al2O3:SiO 2) on bulk glass structure, acid dissolution rate, and surface layer structure were determined. Surface layer formation and structure was investigated using a host of analytical techniques as a function of these compositional variables. It is shown that although the (CaO+Na2O):(Al2O 3) molar ratio remains unity throughout the series, a fully polymerized structure (expected based on "traditional" glass structure models) could not be validated. Bulk glass structures were determined experimentally with ultra-violet Raman spectroscopy (UV-Raman), infrared absorption spectroscopy (IR-absorption), and 29Si magic angle spinning nuclear magnetic resonance (29Si MAS-NMR), and were modeled with molecular dynamic (MD) simulations. The relative concentration of network bonding structures including: non-bridging oxygen (NBO) species, Al-O-Al bonding, and oxygen triclusters, were determined. These characteristics were used to explain dissolution rate, modifier release rate, and surface layer formation of the glasses when exposed to acid. Dissolution rate decreases with increasing Si-O-Si concentration. Dissolution and surface layer formation were the result of breaking network forming bonds (Al-O-Si and Al-O-Al), release of aluminum, sodium, and calcium at equal rates, and rapid re-polymerization of insoluble silica. The surface layers did not form through diffusion-limited ion-exchange between proton-bearing solution species and modifier ions within the glass. The transformed surface layers were found to be microporous, more structurally ordered than the bulk glass, and to contain primarily 3-membered and 4-membered silicate rings (with terminal silanols and trapped molecular water). The processes involved in the layer transformation were simulated using MD, and the resultant layer structures were consistent with the experimental 29Si MAS-NMR results; specifically localized condensation (relaxation) of insoluble silica as the reaction proceeds into the bulk glass.

Mellott, Nathan Petteys

148

Preparation of functionalized zeolitic frameworks  

SciTech Connect

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

149

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

PubMed

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

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

2008-10-11

150

Quench Rate Studies of Aluminum Coordination and Oxygen Speciation in Calcium Aluminosilicate Glasses: Implications for Temperature Effects on the Structure of Aluminosilicate Melts  

Microsoft Academic Search

The atomic-scale structure of aluminosilicate glasses and melts is subject to temperature-induced rearrangement, which in turn controls variations in measurable thermodynamic properties. In order to investigate the effect of temperature on the structure of calcium aluminosilicate melts, we have used Al-27 MAS NMR, Al-27 3QMAS NMR, and O-17 MAS NMR to study fast- and slow-quenched calcium aluminosilicate glasses. Our previous

E. V. Dubinsky; J. F. Stebbins

2006-01-01

151

Crystalline solids.  

PubMed

Many drugs exist in the crystalline solid state due to reasons of stability and ease of handling during the various stages of drug development. Crystalline solids can exist in the form of polymorphs, solvates or hydrates. Phase transitions such as polymorph interconversion, desolvation of solvate, formation of hydrate and conversion of crystalline to amorphous form may occur during various pharmaceutical processes, which may alter the dissolution rate and transport characteristics of the drug. Hence it is desirable to choose the most suitable and stable form of the drug in the initial stages of drug development. The current focus of research in the solid-state area is to understand the origins of polymorphism at the molecular level, and to predict and prepare the most stable polymorph of a drug. The recent advances in computational tools allow the prediction of possible polymorphs of the drug from its molecular structure. Sensitive analytical methods are being developed to understand the nature of polymorphism and to characterize the various crystalline forms of a drug in its dosage form. The aim of this review is to emphasize the recent advances made in the area of prediction and characterization of polymorphs and solvates, to address the current challenges faced by pharmaceutical scientists and to anticipate future developments. PMID:11325474

Vippagunta, S R; Brittain, H G; Grant, D J

2001-05-16

152

Adamantanes from petroleum with zeolites  

Microsoft Academic Search

Experiments with zeolite Beta and zeolite Y demonstrate that adamantane and methyl adamantanes can be isolated very effectively from modern refinery streams by mild hydrocracking over Pt-and Pd-containing large pore zeolites. Yield depends importantly on individual refinery crude source and process configuration. Heavy crudes and refineries with conventional hydrocracking and FCC feed hydrotreater facilities are particularly desirable, and an ideal

L. Deane Rollmann; Larry A. Green; Robert A. Bradway; Hye Kyung C. Timken

1996-01-01

153

Estudio de zeolitas de hierro por el efecto Moessbauer y la resonancia paramagnetica electronica. (Study of iron exchanged zeolites by Moessbauer effect and electron spin resonance spectroscopy).  

National Technical Information Service (NTIS)

Crystalline iron exchanged NaY zeolites, prepared from aqueous solutions and calcined at atmospheric conditions, have been studied and characterized by XRD, Moessbauer and EPR spectroscopies and TGA analysis. Three iron sites are clearly distinguished fro...

C. E. Aguirre Campuzano

1993-01-01

154

Lactic acid production on liquid distillery stillage by Lactobacillus rhamnosus immobilized onto zeolite.  

PubMed

In this study, lactic acid and biomass production on liquid distillery stillage from bioethanol production with Lactobacillus rhamnosus ATCC 7469 was studied. The cells were immobilized onto zeolite, a microporous aluminosilicate mineral and the lactic acid production with free and immobilized cells was compared. The immobilization allowed simple cell separation from the fermentation media and their reuse in repeated batch cycles. A number of viable cells of over 10(10) CFU g(-1) of zeolite was achieved at the end of fourth fermentation cycle. A maximal process productivity of 1.69 g L(-1), maximal lactic acid concentration of 42.19 g L(-1) and average yield coefficient of 0.96 g g(-1) were achieved in repeated batch fermentation on the liquid stillage without mineral or nitrogen supplementation. PMID:23186681

Djuki?-Vukovi?, Aleksandra P; Mojovi?, Ljiljana V; Joki?, Bojan M; Nikoli?, Svetlana B; Pejin, Jelena D

2012-10-23

155

The physicochemical properties of micro/mesoporous materials prepared by the recrystallization of zeolite BEA  

NASA Astrophysics Data System (ADS)

Micro-mesoporous materials with various ratios between micro- and mesopores were prepared by the recrystallization of zeolite BEA in an alkaline medium in the presence of cetyltrimethylammonium bromide. The materials were characterized by X-ray diffraction, low-temperature nitrogen adsorption, and IR spectroscopy. Recrystallization under mild conditions did not cause substantial changes in the number of acid centers but increased the accessibility of acid centers to large-sized molecules because of the creation of mesopores. An increase in the degree of recrystallization caused first partial and then complete zeolite transformation into MSM-41 mesoporous aluminosilicate, which was accompanied by a decrease in the number of acid centers. The IR spectra were used to determine the diffusion coefficients of cumene in the initial and recrystallized samples. Recrystallization increased the diffusion coefficient by 3-4 times.

Ordomskii, V. V.; Monakhova, Yu. V.; Knyazeva, E. E.; Nesterenko, N. S.; Ivanova, I. I.

2009-06-01

156

Thermochemical treatment of zeolitic cracking catalysts containing rare-earth elements  

SciTech Connect

The authors report on the optimization of process conditions in the thermochemical treatment in commercial production of the catalyst KMTsR-N. Freshly molded zeolitic hydrogel beads, with or without specially introduced aluminum hydroxide, were treated successively with a nitrate solution of rare-earth elements (REE) and an ammonium nitrate solution. A simplified flow plan for the thermochemical treatment is shown. The dynamics of the variation and concentration of the treating solutions and the composition of the hydrogen beads during thermochemical treatment is shown. The studies show that in order to obtain a uniform distribution of REE cations in zeolitic aluminosilicate hydrogel beads, the beads must be treated with a solution containing a mixture of ammonium and REE cations.

Baiburskii, V.L.; Kosolapova, A.P.; Rabinovich, S.I.; Bol'shakova, T.A.

1987-01-01

157

Structural Environments of Chloride in Silicate and Aluminosilicate Glasses: Cl-35 NMR of a Volatile Species  

NASA Astrophysics Data System (ADS)

As a volatile species, chloride behavior affects the nature and timing of magmatic degassing. Chloride is also recognized as an important complexing agent for metals in hydrothermal ore fluids and is directly related to many mineral deposits. In silicate melts, chloride solubilities have been observed to be strongly dependent on melt composition, and from these studies chlorine speciation has been inferred. However, little direct spectroscopic data is available to constrain the chemical and structural environments of chlorine in these systems. As such, the local environments of chlorine anions in several silicate and aluminosilicate glasses were probed using chlorine-35 MAS NMR. NMR spectra were obtained at 14.1 and 18.8 T fields for a series of Na- and Ca- silicate and aluminosilicate glasses with 1 wt % Cl. Peaks are roughly Gaussian in shape, much narrower than the total chemical shift range for the nuclei, and contributions to peak widths are primarily from quadrupole interactions (Wq) and to a lesser extent chemical shift distribution (Wcsd). Peak widths (FWHM), Wq, and Wcsd at 14.1 T, isotropic chemical shifts (relative to 1 M aq. NaCl), and mean quadrupole coupling constants (? =.7) for the samples probed are: Na-silicate (6210+/-80 Hz, 92+/-3 ppm, 50+/-2 ppm, -70+/-5 ppm, 3.3+/-.1 Hz), Ca-Na-silicate (11750+/-70 Hz, 186+/-4 ppm, 72+/-5 ppm, -50+/-15ppm, 3.2+/-.4 Hz), Ca-silicate (11250+/-590 Hz, 175+/-16 ppm, 78+/-6 ppm, 81+/-20 ppm, 4.4+/-.4 Hz), and Ca-aluminosilicate (12900+/-240 Hz, 217+/-6 ppm, 33+/-10 ppm, 14+/-39 ppm, 3.5+/-.9 Hz). Modeling of the mixed cation (Ca-Na) silicate glass suggests that most (>60%) Cl in the sample is in a mixed bonding environment with a significant amount (~25%) completely Na-coordinated and a minor amount (<10%) completely Ca-coordinated. There is no evidence for significant Cl-Al bonding and quantization of peak intensities suggests that there is little to no "NMR-invisible" Cl in the samples due to peak broadening caused by a large quadrupolar coupling constant. This observation is mirrored in the relative instability of Cl-Al bonds in crystalline solids.

Sandland, T. O.; Du, L.-; Stebbins, J. F.

2002-12-01

158

The structural behavior of ferric and ferrous iron in aluminosilicate glass near meta-aluminosilicate joins  

NASA Astrophysics Data System (ADS)

Iron-57 resonant absorption Mssbauer spectroscopy was used to describe the redox relations and structural roles of Fe 3+ and Fe 2+ in meta-aluminosilicate glasses. Melts were formed at 1500 C in equilibrium with air and quenched to glass in liquid H 2O with quenching rates exceeding 200 C/s. The aluminosilicate compositions were NaAlSi 2O 6, Ca 0.5AlSi 2O 6, and Mg 0.5AlSi 2O 6. Iron oxide was added in the form of Fe 2O 3, NaFeO 2, CaFe 2O 4, and MgFe 2O 4 with total iron oxide content in the range 0.9 to 5.6 mol% as Fe 2O 3. The Mssbauer spectra, which were deconvoluted by assuming Gaussian distributions of the hyperfine field, are consistent with one absorption doublet of Fe 2+ and one of Fe 3+. From the area ratios of the Fe 2+ and Fe 3+ absorption doublets, with corrections for differences in recoil-fractions of Fe 3+ and Fe 2+, the Fe 3+/?Fe is positively correlated with increasing total iron content and with decreasing ionization potential of the alkali and alkaline earth cation. There is a distribution of hyperfine parameters from the Mssbauer spectra of these glasses. The maximum in the isomer shift distribution function of Fe 3+, ?Fe 3+, ranges from about 0.25 to 0.49 mm/s (at 298 K relative to Fe metal) with the quadrupole splitting maximum, ?Fe 3+, ranging from 1.2 to 1.6 mm/s. Both ?Fe 3+ and ?Fe 2+ are negatively correlated with total iron oxide content and Fe 3+/?Fe. The dominant oxygen coordination number Fe 3+ changes from 4 to 6 with decreasing Fe 3+/?Fe. The distortion of the Fe 3+-O polyhedra of the quenched melts (glasses) decreases as the Fe 3+/?Fe increases. These polyhedra do, however, coexist with lesser proportions of polyhedra with different oxygen coordination numbers. The ?Fe 2+ and ?Fe 2+ distribution maxima at 298 K range from 0.95 to 1.15 mm/s and 1.9 to 2.0 mm/s, respectively, and decrease with increasing Fe 3+/?Fe. We suggest that these hyperfine parameter values for the most part are more consistent with Fe 2+ in a range of coordination states from 4- to 6-fold. The lower ?Fe 2+-values for the most oxidized melts are consistent with a larger proportion of Fe 2+ in 4-fold coordination compared with more reduced glasses and melts.

Mysen, Bjorn O.

2006-05-01

159

Tumbling approach towards template-free synthesis of EMT zeolite  

Microsoft Academic Search

The zeolite EMT has been synthesized with 18-crown-6\\/Al2O3 ratios as low as 0.14, by applying continuous tumbling of the synthesis mixture during the entire aging and crystallization period. The crystalline product contained only two crown ether molecules per unit cell, and the mother liquor was essentially free of crown ether. It was found that the lower the amount of crown

Rune Wendelbo; Michael Stcker; Hanne Junggreen; Helle B Mostad; Duncan E Akporiaye

1999-01-01

160

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

161

The Influence of Reactants and Al/Ga/Si Ratios on the Synthesis of CGS Structured Zeolites  

SciTech Connect

ECR-9 (CGS) zeolites have been synthesized from gallosilicate and gallo-aluminosilicate gels at between 100 {sup o}C and 220 {sup o}C using several Al and Si reactant types. Aluminum was substituted for gallium in the framework at levels up to 20% in seeded syntheses, but higher Al substitutions promote the crystallization of impurities. This is the first report of a gallo-aluminosilicate CGS composition. We successfully used the Simulated Framework Annealing method to solve the structural topology as if ECR-9 was a novel gallosilicate. The structure was refined using Rietveld full profile analysis (wRp = 14.6%) of powder synchrotron X-ray diffraction data.

Strohmaier,K.; Vaughan, D.; Zhang, B.

2007-01-01

162

Zeolite-Hydraulic Cement Containment Medium.  

National Technical Information Service (NTIS)

The invention generally relates to a zeolite-hydraulic cement containment medium for hazardous wastes. In particular, the invention relates to a process for preparing a zeolite-portland cement containment medium from a paste prepared by mixing zeolite in ...

P. M. Brown M. A. Maginnis C. R. Furlong M. G. Bakker G. L. Turner

1994-01-01

163

Enhanced ion mobility in aluminosilicate/polysiloxane network polyelectrolytes  

SciTech Connect

A new series of polysiloxane-based single-ion conductors was prepared. These contain solvating oligoether sidechains and covalently linked aluminosilicate or alkoxy/siloxy-aluminate anions attached to the polysiloxane backbone. Of these two systems, the polymers containing aluminosilicate [(SiO){sub 4}Al]{sup {minus}} anions show higher room temperature conductivities (10{sup {minus}6} S/cm) than those with alkoxy/siloxyaluminate [(SiO){sub 2}(CH{sub 2}O){sub 2}Al]{sup {minus}} anions (10{sup {minus}7} S/cm). The incorporation of longer covalent tethers between the alkoxy/siloxyaluminate anion and the polymer backbone results in enhanced room temperature conductivities at high ion loadings. Differential scanning calorimetry data provide a rationale for the high conductivity.

Siska, D.P.; Shriver, D.F.

2000-07-01

164

Binding and catalytic reduction of NO by transition metal aluminosilicates  

SciTech Connect

The objective of this research is to provide the scientific understanding of processes that actively and selectively reduce NO in dilute exhaust streams, as well as in concentrated streams, to N{sub 2}. Experimental studies of NO chemistry in transition metal-containing aluminosilicate catalysts are being carried out with the aim of determining the chemical rules for NO reduction on non- precious metals.

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

1990-01-01

165

Binding and catalytic reduction of NO by transition metal aluminosilicates  

SciTech Connect

The objective of this research is to provide the scientific understanding of processes that actively and selectively reduce NO in dilute exhaust streams, as well as in concentrated streams, to N{sub 2}. Experimental studies of NO chemistry in transition metal- containing aluminosilicate catalysts are being carried out with the aim of determining the chemical rules for NO reduction on non-precious metals.

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

1992-03-01

166

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

167

Origin of dynamical heterogeneities in calcium aluminosilicate liquids  

NASA Astrophysics Data System (ADS)

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.

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

2010-05-01

168

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

169

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

170

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

171

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

172

Relationship between texture and acidic properties of aluminosilicates and the conditions of their preparation  

SciTech Connect

A study has been made of the method of pH adjustment in the precipitation of hydrogel in relation to its influence on the texture and acidic properties of alumino-silicates. It has been established that large-pore aluminosilicates can be obtained from neutral solutions. X-ray diffraction analysis of aluminosilicates has shown that the method of pH adjustment also affects their phase composition.

Grzechowiak, E.R.; Masalska, A.

1986-04-01

173

Elucidation of the role of potassium fluoride in the chemical and physical nature of ZSM-5 zeolite  

Microsoft Academic Search

This investigation synthesized the ZSM-5 zeolite using sodium silicate, aluminum sulfate and tetrapropylammonium bromide. In addition to examining how the KF additive affected the crystal structure, crystallinity, crystal size and crystal morphology by XRPD and SEM measurements, this work investigated how the KF additive affected the specific surface area, Al contents and zeolite framework through BET, ICP-MS, SIMS, 29Si, 27Al-MAS

Jun-An Ke; Ikai Wang

2001-01-01

174

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

175

Experimental Proof for Resonant Diffusion of Normal Alkanes in LTL and ZSM-12 Zeolites  

Microsoft Academic Search

The intra-crystalline diffusion of normal alkanes in LTL and ZSM-12 zeolite was experimentally studied via gravimetric measurements performed at different temperatures. A periodic dependence of the diffusion coefficient on the number of carbon atoms in alkane was detected, which is an experimental proof for resonant diffusion. The present observations were described on the base of the existing theory of the

Kyesang Yoo; Roumen Tsekov; P. G. Smirniotis

2003-01-01

176

Monoethanol amine modified zeolite 13X for CO adsorption at different temperatures  

Microsoft Academic Search

Zeolite 13X has been modified with monoethanol amine (MEA). MEA loadings of 0.5-25 wt % have been achieved using the impregnation method in different solvents. The mode of incorporation based on methanol with stirring at room temperature appears to be the most feasible. The adsorbent has been characterized for crystallinity, surface area, pore volume, and pore size. The thermal stability

P. D. Jadhav; R. V. Chatti; R. B. Biniwale; N. K. Labhsetwar; S. Devotta; S. S. Rayalu

2007-01-01

177

Resonant diffusion of normal alkanes in zeolites: effect of the zeolite structure and alkane molecule vibrations  

Microsoft Academic Search

Diffusion of normal alkanes in one-dimensional zeolites is theoretically studied on the basis of the stochastic equation formalism. The calculated diffusion coefficient accounts for the vibrations of the diffusing molecule and zeolite framework, molecule-zeolite interaction, and specific structure of the zeolite. It is shown that when the interaction potential is predominantly determined by the zeolite pore structure, the diffusion coefficient

Roumen Tsekov; Panagiotis G. Smirniotis

1998-01-01

178

Improved zeolitic isocracking catalysts  

SciTech Connect

Chevron Research Company introduced the first low pressure, low temperature catalytic hydrocracking process--ISOCRACKING--in 1959. Within the last four years, Chevron has developed and commercialized three new zeolitic ISOCRACKING catalysts. ICR 209 is Chevron`s latest noble metal ISOCRACKING catalyst. It offers improved liquid yield stability, longer life, and superior polynuclear aromatics control compared to its predecessor. ICR 209`s high hydrogenation activity generates the highest yields of superior quality jet fuel of any zeolitic ISOCRACKING catalyst. The second new ISOCRACKING catalyst, ICR 208, is a base metal catalyst which combines high liquid selectivity and high light naphtha octane in hydrocrackers operating for maximum naphtha production. ICR 210 is another new base metal catalyst which offers higher liquid yields and longer life than ICR 208 by virtue of a higher hydrogenation-to-acidity ratio. Both ICR 208 and ICR 210 have been formulated to provide higher liquid yield throughout the cycle and longer cycle length than conventional base metal/zeolite catalysts. This paper will discuss the pilot plant and commercial performances of these new ISOCRACKING catalysts.

Dahlberg, A.J.; Habib, M.M.; Moore, R.O. [Chevron Research and Technology Co., Richmond, CA (United States); Law, D.V. [Chevron International Oil Co., San Francisco, CA (United States); Convery, L.J. [ABB Lummus Crest, Bloomfield, NJ (United States)

1995-09-01

179

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

SciTech Connect

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

Iton, L.E.; Trouw, F.; Brun, T.O. [Argonne National Lab., IL (United States)] [and others

1992-04-01

180

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

181

Zeolite modification II - direct fluorination  

Microsoft Academic Search

Over the past thirty years, zeolite science has grown into a major branch of chemistry. A large number of new zeolite materials have been made by both direct hydrothermal synthesis and by post-synthesis modification. This has led to a large number of new applications in such diverse fields as catalysis, adsorption and ion exchange. In synthesis alone, over one hundred

B. M. Lok; F. P. Gortsena; P. J. Izod; C. A. Messina; H. Rastelli

1982-01-01

182

Zeolitic basanite from southeastern California  

Microsoft Academic Search

In a belt of Quaternary volcanism within the Mojave Desert, California, lavas of alkali-olivine basalt have been extruded from many centers. Also three small volcanoes erupted alkaline lavas similar to basanite, except that the zeolites phillipsite and chabazite crystallized in the groundmass instead of the usual feldspathoid. These zeolite-bearing lavas, more alkaline than the olivine basalts, brought many peridotitic nodules

W. S. Wise

1966-01-01

183

Sulfidation of lead-loaded zeolite microparticles and flotation by amylxanthate.  

PubMed

The possibility of recovering lead-loaded zeolite Y microparticles (PbY) by flotation after sulfidation was investigated using amyl xanthate (AMX) as the collector. The sulfidation process (by aqueous Na2S) was first studied as a function of the medium composition (Na2S concentration, pH), and the solid phases were characterized by various physicochemical techniques (X-ray photoelectron spectroscopy, high-frequency impedance measurements, and electrochemistry). Progressively increasing the sulfidation level resulted in the concomitant transformation of Pb(II) species ion-exchanged in the zeolite into PbS clusters that were mostly located at the external boundaries of the zeolite particles while remaining attached to the aluminosilicate (PbS-Y). Similar to what occurred for galena particles, the zeolite-supported PbS clusters were likely to adsorb the AMX collector, the remaining (nonsulfided) ion-exchanged Pb(II) species being transformed into a Pb(AMX)2 precipitate when using AMX in large excess. Owing to such AMX adsorption on PbS-Y, the zeolite particles were found to flocculate and to float in the presence of air bubbles. If rather high AMX concentrations (>5 x 10(-3) M) were necessary to ensure the flotation of nonsulfided PbY particles (Walcarius, A.; Lamdaouar, A. M.; El Kacemi, K.; Marouf, B.; Bessiere, J. Langmuir 2001, 17, 2258), significantly lower concentrations (down to 1 x 10(-4) M) gave rise to high flotation yields (ca. 95%) upon PbY sulfidation. It is noteworthy that the sulfidation level should be maintained at a value high enough (>10%) to produce the minimal PbS amount ensuring flotation but not too high (<75%) to avoid conditions that are too reducing and are not compatible with the flotation process. Finally, depression tests seemed to indicate that PbS-Y flotation occurs according to a mechanism similar to that described for the galena mineral. PMID:16460090

Walcarius, Alain; Marouf, Bouchab; Lamdaouar, Ali M; Chlihi, Khadija; Bessiere, Jacques

2006-02-14

184

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

PubMed

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

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

2012-07-30

185

Enhancing Nitrification at Low Temperature with Zeolite in a Mining Operations Retention Pond  

PubMed Central

Ammonium nitrate explosives are used in mining operations at Diavik Diamond Mines Inc. in the Northwest Territories, Canada. Residual nitrogen is washed into the mine pit and piped to a nearby retention pond where its removal is accomplished by microbial activity prior to a final water treatment step and release into the sub-Arctic lake, Lac de Gras. Microbial removal of ammonium in the retention pond is rapid during the brief ice-free summer, but often slows under ice cover that persists up to 9?months of the year. The aluminosilicate mineral zeolite was tested as an additive to retention pond water to increase rates of ammonium removal at 4C. Water samples were collected across the length of the retention pond monthly over a year. The structure of the microbial community (bacteria, archaea, and eukarya), as determined by denaturing gradient gel electrophoresis of PCR-amplified small subunit ribosomal RNA genes, was more stable during cold months than during JulySeptember, when there was a marked phytoplankton bloom. Of the ammonia-oxidizing community, only bacterial amoA genes were consistently detected. Zeolite (10?g) was added to retention pond water (100?mL) amended with 5?mM ammonium and incubated at 12C to encourage development of a nitrifying biofilm. The biofilm community was composed of different amoA phylotypes from those identified in gene clone libraries of native water samples. Zeolite biofilm was added to fresh water samples collected at different times of the year, resulting in a significant increase in laboratory measurements of potential nitrification activity at 4C. A significant positive correlation between the amount of zeolite biofilm and potential nitrification activity was observed; rates were unaffected in incubations containing 120?mM ammonium. Addition of zeolite to retention ponds in cold environments could effectively increase nitrification rates year-round by concentrating active nitrifying biomass.

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

2012-01-01

186

Nonbridging Oxygens in Calcium Aluminosilicate Glass From Per-calcic to Peraluminous Compositions  

Microsoft Academic Search

The role of non-bridging oxygen (NBO) and its effects on the thermodynamic and transport properties of aluminosilicate melts are not fully understood, although this species clearly must have a major influence on configurational entropy, viscosity, etc. Its existence along metaluminous joins in alkali- and alkaline-earth aluminosilicates was first postulated from viscosity measurements (Toplis et al., 1996, 2004) and then directly

L. Thompson; J. Stebbins

2008-01-01

187

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

188

Elastic interpretation of the glass transition in aluminosilicate liquids  

NASA Astrophysics Data System (ADS)

One of the remaining puzzles of the glass transition is the origin of a glass-forming liquid's fragility, which quantifies the departure of its relaxation time from Arrhenius-activated kinetics. According to the shoving model proposed by Dyre, fragility is controlled by the instantaneous shear modulus of the liquid, since any flow event requires a local volume increase, and the related activation energy is equal to the work done in shoving aside the surrounding atoms. Here, we present an in situ high-temperature Brillouin spectroscopy test of the shoving model near the glass transition of eight aluminosilicate glass-forming systems. We find that the measured viscosity data agree qualitatively with the measured temperature dependence of shear moduli, as predicted by the shoving model. However, the model systematically underpredicts the values of fragility for our aluminosilicate liquids. This suggests that the dynamics of the glass transition are governed by additional factors beyond the evolution of the shear modulus, such as configurational entropy. We have also compared the glass transition temperature (Tg,vis) obtained from viscosity (temperature at 1012 Pa s) with the onset temperatures of the decrease in elastic moduli (Tg,elas) and increase in the thermal expansion coefficient (Tg,CTE) during heating. While we find an approximate one-to-one correlation between Tg,vis and Tg,CTE, it is clear that the elastic moduli probe a different frequency response of the glass structure, since Tg,elas is systematically lower than Tg,vis.

Smedskjaer, Morten M.; Huang, Liping; Scannell, Garth; Mauro, John C.

2012-04-01

189

Thermionic aluminosilicate sources of Tl{sup +} ions  

SciTech Connect

Thermionic filament sources of Tl{sup +} ions were made using tungsten wire coated with synthetic thallium aluminosilicates in the {beta}-eucryptite (Tl{sub 2}OAl{sub 2}O{sub 3}2SiO{sub 2}) and two other compositions (2Tl{sub 2}OAl{sub 2}O{sub 3}2SiO{sub 2} and 2Tl{sub 2}OAl{sub 2}O{sub 3}4SiO{sub 2}). Three different methods for the production of aluminosilicate melts were used. The performance characteristics as thermionic emission sources of Tl{sup +} ions based on total emission current and purity of ion emission as functions of time and filament surface temperature were studied and compared. Our results indicated that the sample of composition ratio of 2Tl{sub 2}OAl{sub 2}O{sub 3}2SiO{sub 2}, which was produced by resistance heating under atmospheric pressure in air, is an optimum Tl{sup +} ion source at temperatures between 1150 and 1350 {degree}C after 150 h of continuous heating. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Zhou, Z.L.; Tan, T.L.; Ong, P.P. [National University of Singapore, Department of Physics, Faculty of Science, Lower Kent Ridge Road, Singapore 0511 (Singapore)

1995-11-01

190

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

191

Crystallinity in starch bioplastics  

Microsoft Academic Search

Thermoplastic starch (TPS) materials have been prepared by kneading, extrusion, compression moulding and injection moulding of several native starches with the addition of glycerol as a plasticizer. Two types of crystallinity can be distinguished in TPS directly after processing: (i) residual crystallinity: native A-, B- or C-type crystallinity caused by incomplete melting of starch during processing; (ii) processing-induced crystallinity: amylose

Jeroen J. G. van Soest; S. H. D. Hulleman; D. de Wit; J. F. G. Vliegenthart

1996-01-01

192

Two stage process for improving the catalyst life of zeolites in the synthesis of lower olefins from alcohols and their ether derivatives  

SciTech Connect

A process is described for converting an alcohol and/or ether feed as hereinafter defined to a hydrocarbon mixture rich in olefins which comprises contacting, under conversion conditions at a conversion reaction temperature of from about 300/sup 0/ to 350/sup 0/C., a feed comprising one or more monohydric alcohols having from about 1 to about 4 carbon atoms, ethers derived therefrom, or mixtures of the alcohols and ethers, with a modified crystalline metalosilicate shape selective acidic zeolite. The metalosilicate is selected from the group consisting of aluminum, gallium, and mixtures thereof, and the zeolite, prior to modification and in the absence of any coke deposited thereon, possesses: (a) the capability of catalyzing the alcohol and/or other conversion reaction; (b) a channel size and structure such as to permit (i) entry of the feed into the zeolite and diffusion to the active acid sites within the zeolite, and (ii) formation of olefin products within the zeolite and diffusion of the products out of the zeolite; and (c) hydrothermal stability at temperatures of at least about 290/sup 0/C. The modification of the zeolite is conducted in a manner sufficient to increase the catalyst life of the zeolite, relative to the absence of the modification when the zeolite is employed as a catalyst for the alcohol and/or ether conversion reaction.

Pieters, W.J.M.; Okumura, Y.

1987-01-20

193

Absence of Non-Bridging Oxygen on the Metaluminous Join in Potassium Aluminosilicate Glasses  

NASA Astrophysics Data System (ADS)

In aluminosilicate melts and glasses, non-bridging oxygen (NBO) have a significant influence on thermodynamic and transport properties such as configurational entropy and viscosity. However, both its role and the extent of its influence are not yet fully understood, particularly in metaluminous and peraluminous compositions. Viscosity measurements from sodium, calcium, and magnesium aluminosilicate melts first suggested the presence of NBO on the metaluminous join (e.g. CaAl2O4-SiO2) (Toplis et al., 1996, 2004); direct observation with 17O nuclear magnetic resonance (NMR) spectroscopy has so far been limited to calcium aluminosilicate glasses, where it has been observed in both metalumious and peraluminous compositions (Stebbins et al., 2008). Potassium aluminosilicate glasses are another candidate for exploring the possibility of NBO on the metaluminous join, as the NBO peak is partially resolved from the bridging oxygen peak even in the one dimensional magic angle spinning (MAS) spectrum. However, preliminary analysis of 17O NMR spectra of slightly peraluminous potassium aluminosilicate glasses shows no detectable signal (<1% of total oxygen) in the area expected for NBO. Calcium aluminosilicate glasses of similar compositions have an NBO content of approximately 4.5%. This comparison shows an influence by the field strength of the network modifying cation on the presence of NBO and fraction of five-coordinated aluminum at the glass transition. However, understanding the extent of this impact in melts requires additional work exploring the temperature effects on speciation in the potassium aluminosilicate glasses.

Thompson, L. M.; Stebbins, J. F.

2009-12-01

194

Electron microscopy study of zeolite ZK-14; a synthetic chabazite  

NASA Astrophysics Data System (ADS)

The defect structure of zeolite (K+, TMA+) ZK-14, a synthetic chabazite, has been studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM together with TEM bright field (BF) and dark field (DF) micrographs indicate that the hexagonal, platelet ZK-14 crystals are built up of crystalline blocks joined by twinning along (00.1). High resolution transmission electron microscopy (HRTEM) reveals faulting of the ideal AABBCC single 6-ring stacking sequence of ZK-14. This is consistent with an observed line broadening in its X-ray powder diffraction profile. Channel apertures are imaged, even for thick specimens.

Cartlidge, S.; Wessicken, R.; Nissen, H.-U.

1983-03-01

195

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

196

Effects of step-change of synthesis temperature on synthesis of zeolite 4A from coal fly ash  

Microsoft Academic Search

Pure form, single phase and high crystalline zeolite 4A samples were synthesized by applying step-change of synthesis temperature during hydrothermal treatment of coal fly ash prepared solution. The results indicate that step-change of synthesis temperature during hydrothermal treatment plays an important role in reducing the overall synthesis time while maintaining a high degree of crystallinity for the samples. In order

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

2006-01-01

197

Stimulated short-wave emission of charged particles in natural hollow crystalline channels  

Microsoft Academic Search

A quantum theory of the spontaneous and stimulated emission of relativistic and nonrelativistic charged particles moving in natural hollow cylindrical crystalline channels is elaborated with reference to the development of X-ray and gamma lasers. The example of channels in zeolite and chrysolite-asbestos is used to illustrate the features of the quantized motion of particles in such structures, as well as

V. I. Vysotskii; P. N. Kuzmin

1983-01-01

198

Zeolitic basanite from southeastern California  

Microsoft Academic Search

In a belt of Quaternary volcanism within the Mojave Desert, California, lavas of alkali-olivine basalt have been extruded\\u000a from many centers. Also three small volcanoes erupted alkaline lavas similar to basanite, except that the zeolites phillipsite\\u000a and chabazite crystallized in the groundmass instead of the usual feldspathoid. These zeolite-bearing lavas, more alkaline\\u000a than the olivine basalts, brought many peridotitic nodules

W. S. Wise

1966-01-01

199

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

200

Nonsaturable absorption in alumino-silicate bismuth-doped fibers  

NASA Astrophysics Data System (ADS)

We report an experimental and theoretical investigation of fluorescence decay and transmission coefficient at ~1 ?m pumping for a series of bismuth (Bi) doped alumino-silicate fibers with different concentrations of Bi centers. By modeling the experimental data, we show that the excited-state absorption (ESA) and up-conversion (UC) processes are responsible for a growth of nonsaturable absorption and deviation from exponential the fluorescence decay in the fibers with an increase in Bi centers content. Assuming that Bi centers ensemble is composed of subsystems of single and paired centers, and an increase in partial weight of the latter with a Bi centers concentration growth, we can successfully explain the experimental data. Also, these assumptions allow us to estimate the constants characterizing the ESA and both homogeneous and inhomogeneous UC processes in the fibers.

Kir'yanov, A. V.; Dvoyrin, V. V.; Mashinsky, V. M.; Barmenkov, Yu. O.; Dianov, E. M.

2011-01-01

201

Drying and calcining fine-bead aluminosilicate adsorbent  

SciTech Connect

Under normal fabrication conditions for aluminosilicate adsorbents intended for lube oil treatment the yield of the desired 0.28-0.8 mm bead size is usually low. To determine the reasons for this and to develop guidelines for improving the yield of this size range, a three-day plant test was carried out under steady-state conditions in a commercial reactor. Attention was focused on drying and calcining conditions since the most severe breakdown of adsorbent particles was assumed to occur at these stages of synthesis. The main reasons for breakdown were found to be severe and extended mixing of the hydrogel slurry by air in the collectors ahead of the spray dryers, pneumatic transport from the spray dryer to the calcining vessel while the product is still structurally weak, and intense backmixing in the fluidized bed of the calcining vessel.

Sokolov, V.P.; Golovanov, V.N.; Moroz, A.A.; Zaitsev, V.A.; Poezd, D.F.; Mezentsev, N.V.

1988-05-01

202

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; Gnster, Jens; Mhler, Thomas; Heinrich, Jrgen G.

2013-01-01

203

Structure and properties of low-silica calcium aluminosilicate glasses  

Microsoft Academic Search

The structure of three calcium aluminosilicate glasses with low-silica content (61CaO39Al2O3 (Ca0.39), 55CaO35Al2O310SiO2 (Ca10.35) and 49CaO31Al2O320SiO2 (Ca20.31)), synthesized by a standard quenching technique, were studied by X-ray and neutron diffraction. The data are consistent with the hypothesis that Si and Al are present in tetrahedral sites and Ca in octahedral sites for all compositions. SiT (T=Si or Al) and SiO2

Laurent Cormier; Daniel R Neuville; Georges Calas

2000-01-01

204

Synthesis and Structure Solution of Zeolite SSZ-65  

SciTech Connect

This report describes the synthesis and structure solution of the new zeolite SSZ-65. SSZ-65 may be prepared as either a borosilicate (Si52.5B1.5O108) or an aluminosilicate using 1-[1-(4-chloro-phenyl)-cyclopropylmethyl]-1-ethyl-pyrrolidinium as a structure-directing agent. The structure of SSZ-65 was determined with the FOCUS Fourier recycling method. The framework of SSZ-65 possesses a two-dimensional system of intersecting 12-ring channels with pore apertures of 6.9 Angstroms x 5.9 Angstroms . The topological symmetry of SSZ-65 is P6/mmm, but improvements in the Rietveld refinement of the powder diffraction data are obtained in space group P6/m (a = 16.8009(2) Angstroms and c = 12.6154(1) Angstroms ). The agreement values improve from Rwp = 0.116, Rp = 0.094, and R(F2) = 0.142 in P6/mmm to Rwp = 0.103, Rp = 0.085, and R(F2) = 0.092 in P6/m.

Elomari,S.; Burton, A.; Ong, K.; Pradhan, A.; Chan, I.

2007-01-01

205

Aftereffects in zeolite-encapsulated 57Co-complexes  

NASA Astrophysics Data System (ADS)

Tris(2,2'-bipyridyl)-57CoII and bis(2,2':6',2'-terpyridine)-57CoII complexes were synthesised in the supercages of zeolite-Y in order to study the effect of molecular isolation on the aftereffects of the 57Co(EC)57Fe decay. As compared to the regular crystalline salts of the complex ions where, according to the emission Mssbauer spectra, the most abundant species is low-spin FeII, the molecular isolation in the zeolite resulted in a larger fraction of low-spin FeIII and a varying amount of high-spin Fe2+ species. In the investigated temperature range, 20 K to 295 K, the majority of the changes was observed above 80 K. In the case of tris (2,2'-bipyridyl)-57CoII-Y, the most characteristic change occurred in valence states, while for bis (2,2':6',2'-terpyridine)-57CoII-Y, the temperature dependence of the spin states was more prominent. The change in the low spin valence states is explained partly by donor-acceptor properties of the zeolite lattice. The variation in the high spin fraction is explained by radiation damage of the ligand sphere and/or fragmentation of the complex ion followed by incomplete recombination in the supercage. Molecular isolation itself did not seem to increase the chance of fragmentation (as a consequence of charge neutralization following Auger ionization) of these highly conjugated complex molecules.

Homonnay, Z.; Vank, Gy.; Vrtes, A.; Nath, A.; Spiering, H.; Gtlich, P.

1998-08-01

206

Sodium Sulfate Hot Corrosion of Silicon Carbide Fiber-Reinforced Calcium Aluminosilicate.  

National Technical Information Service (NTIS)

The effects of sodium sulfate hot corrosion on the microstructure of silicon carbide fiber-reinforced calcium aluminosilicate glass-ceramic matrix composite were investigated using optical microscopy, scanning electron microscopy (SEM) and x-ray diffracti...

M. A. Oppici

1995-01-01

207

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

208

Binding and catalytic reduction of NO by transition metal aluminosilicates  

SciTech Connect

Extensive series of experiments were carried out with CO(II)A zeolites containing 2.6 and 3.9 Co[sup 2+] ions per unit cell in which NO and N[sub 2]0 were separately adsorbed, and subsequent temperature programmed desorption (TPD) and optical spectroscopy analyses were carried out to study the desorption and decomposition behavior of these catalysts toward the adsorbates. The solid phase was monitored by optical diffuse reflectance (UV-Vis-NIR), while the gas phase was monitored by mass spectrometry. The experimental data are summarized here, and interpretation of these results is being carried out.

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

1992-09-01

209

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

210

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

PubMed

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

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

2006-09-11

211

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

212

Cation siting in low-silica zeolites with potential applications in pressure swing adsorption technology and structural studies of novel tectosilicates  

NASA Astrophysics Data System (ADS)

Adsorption and catalytic phenomena in zeolites are influenced by coulombic interactions within zeolite structure as well as by size restrictions imposed by zeolitic micropores. In the first part of this thesis, we investigate materials with potential applications in the selective adsorption of nitrogen. Studies have indicated the performance of LiX adsorbents correlates with the number of accessible lithium cations in the zeolite. However, in zeolite LiX only one-third of the lithium cations interact with adsorbed molecules. This prompted our investigation of other low-silica zeolites. The first zeolite examined was a cancrinite prepared in the presence of 1,3-butanediol. Neutron diffraction studies on the lithium-exchanged cancrinite suggest most of the lithium cations are ideally positioned within the micropores. However, our experiments show that carbonate anions are occluded within the micropores of this cancrinite. Another material examined in this study was zeolite (Ba,K)-GL. Neutron diffraction experiments show that 49 of the extraframework charges are located in the micropores. Unfortunately, less than 20% of these cations are replaced after lithium-exchange. We also attempted to directly synthesize a (Ba,Li)-GL. However, diffraction experiments and chemical analyses show that most of the extraframework charge is compensated by barium. Because of molecular size restrictions imposed by currently known zeolites, there is continued interest in the synthesis of materials that can be used for processing large molecules. This motivated our investigation of two tectosilicates MCM-61 and MCM-47. MCM-61 is an aluminosilicate made in the presence of the potassium-18-Crown-6 complex. Our structure solution shows MCM-61 is formed from novel [610412] polyhedral cage units that connect to form 18-membered-ring cages. The structure of MCM-61 suggests that crown ethers, azamacrocycles, and cryptands may be useful for the syntheses of extra-large pore zeolites. MCM-47 is prepared in the presence of tetramethylene bis(N-methylpyrrolidinium) dibromide. The structure solution of MCM-47 shows it is composed of noncovalently bound layers. The structure refinement and 1H MAS NMR experiment indicate these layers are bound together by strong hydrogen bonds between siloxy and silanol groups. MCM-47 can be delaminated to yield a high surface area material with potential applications in the catalysis of large molecules.

Burton, Allen Wayne

213

Dehydration, dehydroxylation, and rehydroxylation of single-walled aluminosilicate nanotubes.  

PubMed

Single-walled metal oxide (aluminosilicate) nanotubes are excellent candidates for addressing the long-standing issue of functionalizing nanotube interiors, due to their high surface reactivity and controllable dimensions. However, functionalization of the nanotube interior is impeded by its high surface silanol density (9.1 -OH/nm(2)) and resulting hydrophilicity. Controlled dehydration of the nanotubes is critical for the success of functionalization efforts. We employ a range of solid-state characterization tools to elucidate dehydration and dehydroxylation phenomena in the nanotubes as a function of heat treatment up to 450 degrees C. Vibrational spectroscopy (Fourier transform infrared, FT-IR), thermogravimetric analysis-mass spectrometry (TGA-MS), nitrogen physisorption, solid-state NMR, and X-ray diffraction (XRD) reveal that a completely dehydrated condition is achieved at 250 degrees C under vacuum and that the maximum pore volume is achieved at 300 degrees C under vacuum due to partial dehydroxylation of the dehydrated nanotube. Beyond 300 degrees C, further dehydroxylation partially disorders the nanotube wall structure. However, a unique rehydroxylation mechanism can partially reverse these structural changes upon re-exposure to water vapor. Finally, detailed XRD simulations and experiments allow further insight into the nanotube packing, the dimensions, and the dependence of nanotube XRD patterns on the water content. PMID:20684571

Kang, Dun-Yen; Zang, Ji; Wright, Elizabeth R; McCanna, Arthur L; Jones, Christopher W; Nair, Sankar

2010-08-24

214

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

215

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

216

Osmium(0) nanoclusters stabilized by zeolite framework; highly active catalyst in the aerobic oxidation of alcohols under mild conditions.  

PubMed

Osmium(0) nanoclusters stabilized by zeolite-Y framework were reproducibly prepared by a simple two step procedure involving the incorporation of osmium(III) cations into the zeolite matrix by ion-exchange, followed by their reduction within the cavities of zeolite with sodium borohydride in aqueous solution all at room temperature. The composition and morphology of osmium(0) nanoclusters stabilized by zeolite framework, as well as the integrity and crystallinity of the host material were investigated by using ICP-OES, XRD, XPS, SEM, TEM, HRTEM, TEM/EDX, mid-IR, far-IR spectroscopies, and N(2)-adsorption/desorption technique. The results of the multiprong analysis reveal the formation of osmium(0) nanoclusters within the cavities of zeolite-Y without causing alteration in the framework lattice, formation of mesopores, or loss in the crystallinity of the host material. More importantly, far-IR studies showed that after the reduction of Os(3+) cations by sodium borohydride the Na(+) cations reoccupy their authentic cation sites restoring the integrity of zeolite-Y. The catalytic activity of osmium(0) nanoclusters stabilized by zeolite framework was tested in the aerobic oxidation of activated, unactivated and heteroatom containing alcohols to carbonyl compounds and was found to provide high activity and selectivity even under mild conditions (80 degrees C and 1 atm O(2) or air). Moreover, they were found to be stable enough to be isolated and bottled as solid material, which can be reused as active catalyst under the identical conditions of the first run. PMID:20614055

Zahmakiran, Mehmet; Akbayrak, Serdar; Kodaira, Tetsuya; Ozkar, Saim

2010-07-07

217

Superior performance of metal-organic frameworks over zeolites as solid acid catalysts in the Prins reaction: green synthesis of nopol.  

PubMed

The catalytic performance of a set of metal-organic frameworks [CuBTC, FeBTC, MIL-100(Fe), MIL-100(Cr), ZIF-8, MIL-53(Al)] was investigated in the Prins condensation of ?-pinene with formaldehyde and compared with the catalytic behavior of conventional aluminosilicate zeolites BEA and FAU and titanosilicate zeolite MFI (TS-1). The activity of the investigated metal-organic frameworks (MOFs) increased with the increasing concentration of accessible Lewis acid sites in the order ZIF-8zeolites BEA and FAU, which showed significantly lower selectivity to the target nopol than the MOFs. Its high activity, the preservation of its structure and active sites, and the possibility to use it in at least three catalytic cycles without loss of activity make MIL-100 (Fe) the best performing catalyst of the series for the Prins condensation of ?-pinene and paraformaldehyde. Our report exemplifies the advantages of MOFs over zeolites as solid catalysts in liquid-phase reactions for the production of fine chemicals. PMID:23592600

Opanasenko, Maksym; Dhakshinamoorthy, Amarajothi; Hwang, Young Kyu; Chang, Jong-San; Garcia, Hermenegildo; ?ejka, Ji?

2013-04-16

218

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 725-850C. 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

2011-03-17

219

Influence of the size of extraframework monovalent cations in X-type zeolite on their thermal behavior  

Microsoft Academic Search

Pure and well crystalline NaX zeolite with Si\\/Al=1.5 was prepared by hydrothermal crystallization from the Na2OAl2O3SiO2H2O system. The hydrothermal crystallization was carried out under autogeneous pressure and at static condition at 368K. The post-synthesis modification was achieved by following conventional ion-exchange technique to obtain K+, Rb+ and Cs+-exchanged forms of NaX zeolite. Compositional and structural investigations of parent sample and

U. D. Joshi; P. N. Joshi; S. S. Tamhankar; V. P. Joshi; B. B. Idage; V. V. Joshi; V. P. Shiralkar

2002-01-01

220

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

221

Structure of Ca and Mg aluminosilicate melts under pressure  

NASA Astrophysics Data System (ADS)

Viscosity and density are important physical properties to control the transportation of magma in the Earth's interior, which are affected by microscopic structure of magma. Magmas have been considered to be densified by structural change with increasing pressure. Recently, Allwardt et al. (2005) found the structure change in auminosilicate glasses quenched under pressure using the NMR spectroscopy, in which an average coordination number of aluminium increases from four to five up to about 10 GPa. We carried out direct observation of structural change in aluminsilicate melts by using in-situ X-ray diffraction method. High-pressure and high-temperature experiments were conducted using MAX80 installed at AR-NE5C of Photon Factory, Tsukuba, Japan. Energy dispersive X-ray diffraction method is applied to acquire diffraction patterns from molten samples. X-ray diffraction spectra were acquired for Ca3Al2Si6O18 and Mg3Al2Si6O18 composition melts up to 5 GPa and 2000 K. Signs of pressure-induced structural change are observed in radial distribution functions as well as in diffraction patterns. The first sharp diffraction peaks (FSDP) shift to higher-Q side with increasing pressure, indicating reduction of the size of the intermediate rage structure, such as rings or chains composed of SiO4 and AlO4 tetrahedra. Radial distribution function also changes with pressure. The nearest neighbour T-O peak (composed of Si-O and Al-O interactions) becomes asymmetric, indicating the coordination increase of the nearest neighbour ions. These observations are consistent with the densification of high-pressure quenched aluminosilicate glasses.

Urakawa, S.; Kikegawa, T.

2007-12-01

222

CRYSTALLINE HEXOKINASE (HETEROPHOSPHATESE)  

PubMed Central

1. Crystalline hexokinase has been isolated from baker's yeast. 2. Crystalline hexokinase is a protein of albumin type of a molecular weight of 96,000. Its isoelectric point is at about pH 4.8. 3. The method of isolation consists in separating the proteins of an aqueous extract of toluene-treated yeast by means of fractional precipitation with ammonium sulfate and with alcohol. 4. The procedure involves also the separation of several crystalline proteins, including one yellow crystalline protein, which do not possess hexokinase activity. The biological and the physicochemical properties of these proteins are still under investigation. 5. The crystallization of hexokinase proceeds at about 5C. in the presence of ammonium sulfate and dilute phosphate buffer pH 7.0. 6. Crystalline hexokinase becomes relatively pure after 2 or 3 recrystallizations as tested by solubility, sedimentation in the ultracentrifuge, and electrophoresis. The enzymatic activity remains constant on repeated crystallization. 7. The enzymatic activity is associated with the protein nature of the material. Inactivation is accompanied by denaturation of the protein. 8. Crystalline hexokinase is relatively stable when stored in the form of crystalline filter cake. Solutions of hexokinase in dilute buffers are most stable at pH 5.0. 9. Crystalline hexokinase requires the presence of magnesium ions for its catalytic activity.

Kunitz, M.; McDonald, Margaret R.

1946-01-01

223

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

224

Characterization of ion distributions near the surface of sodium-containing and sodium-depleted calcium aluminosilicate glass melts  

Microsoft Academic Search

The distribution of cation and anion components of sodium containing calcium aluminosilicate glass was studied by classical molecular dynamics simulations in a high temperature melt in the bulk and at the vacuum-melt interface. A significant redistribution of the sodium and non-bridging oxygen ions was observed. Subsequently, a sodium depleted calcium aluminosilicate glass melt was simulated to determine the sensitivity of

Louis R. Corrales; Jincheng Du

2006-01-01

225

Li+ alumino-silicate ion source development for the Neutralized Drift Compression Experiment (NDCX)  

SciTech Connect

We report results on lithium alumino-silicate ion source development in preparation for warmdense-matter heating experiments on the new Neutralized Drift Compression Experiment (NDCXII). 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 ~;;1275 oC, a space-charge-limited Li+ beam current density of J ~;;1 mA/cm2 was obtained. The lifetime of the ion source was ~;;50 hours 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.

2010-10-01

226

Quench Rate Studies of Aluminum Coordination and Oxygen Speciation in Calcium Aluminosilicate Glasses: Implications for Temperature Effects on the Structure of Aluminosilicate Melts  

NASA Astrophysics Data System (ADS)

The atomic-scale structure of aluminosilicate glasses and melts is subject to temperature-induced rearrangement, which in turn controls variations in measurable thermodynamic properties. In order to investigate the effect of temperature on the structure of calcium aluminosilicate melts, we have used Al-27 MAS NMR, Al-27 3QMAS NMR, and O-17 MAS NMR to study fast- and slow-quenched calcium aluminosilicate glasses. Our previous work using O-17 3QMAS NMR to study lithium and sodium aluminosilicate glasses demonstrates disordering of bridging oxygen species with increasing sample fictive temperature, indicating temperature-induced rearrangement of framework units in the melt. Simple thermodynamic calculations using these results illustrate that while these structural changes may account for a portion of the experimentally-determined heat capacity of the melt, other modifications must occur to produce the observed temperature dependence of this property (Dubinsky and Stebbins 2006). The new data presented here allow us to observe changes in four-and five-coordinated aluminum and bridging and non- bridging oxygen (NBO) populations with fictive temperature in two calcium aluminosilicate glass compositions (CASx.y, where x=mol% Al2O3 and y=mol% SiO2) prepared by slow- and fast-quenching. We find that in CAS25.50 glasses, the percentage of five-coordinated Al per total Al increases from 7.61.9 to 9.42.4 and the percentage of NBO per total oxygen increases from 7.21.8 to 8.92.2 over a 150 to 200 degree fictive temperature interval. In CAS10.60 glasses representing a similar fictive temperature interval, we find that the percentage of five-coordinated Al per total Al increases from 4.01.0 to 4.91.2 and the percentage of non-bridging oxygen (NBO) per total oxygen increases from 22.82.3 to 23.02.3. Uncertainties in fitting procedures producing overlap in quantification of species in fast- and slow-quenched samples do not preclude the conclusion that robust changes in their relative proportions are visible in NMR spectra. Normalizing for sample composition, in both CAS25.50 and CAS10.60 glasses the increase in NBO over the studied fictive temperature interval exceeds the increase in five-coordinated Al, indicating that formation of these species is not necessarily coupled in a simple stoichiometric ratio. These results signify that complex structural changes involving high-coordinated Al and multiple high-coordinated oxygen species must be included in consideration of temperature effects on aluminosilicate melt structure.

Dubinsky, E. V.; Stebbins, J. F.

2006-12-01

227

Cation field strength effects on high pressure aluminosilicate glass structure: Multinuclear NMR and La XAFS results  

NASA Astrophysics Data System (ADS)

We examined aluminosilicate glasses containing a variety of network modifying to intermediate cations (Li, La, Sc, and Fe), quenched from melts at 1 atm to 8 GPa, to further investigate the role of cation field strength in Al coordination changes and densification. 27Al Nuclear Magnetic Resonance Spectroscopy (NMR) reveals that the mean Al coordination increases with increasing pressure in the Li-containing glasses, which can be explained by a linear dependence of fractional change in Al coordination number on cation field strengths in similar K-, Na-, and Ca-containing aluminosilicate glasses (K < Na < Li < Ca). Measured recovered densities follow a similar linear trend. In contrast, the La-containing glasses have significantly lower mean Al coordination numbers at given pressures than the cation field strength of La and glass density would predict. La L 3 X-ray absorption fine structure (XAFS) spectroscopy results indicate a significant increase with pressure in average La-O bond distances, suggesting that La and Al may be "competing" for higher coordinated sites and hence that both play a significant role in the densification of these glasses, especially in the lower pressure range. However, in Na aluminosilicate glasses with small amounts of Sc, 45Sc NMR reveals only modest Sc coordination changes, which do not seem to significantly affect the mean Al coordination values. For a Li aluminosilicate glass, 17O MAS and multiple quantum magic angle spinning (3QMAS) NMR data are consistent with generation of more highly coordinated Al at the expense of non-bridging oxygen (NBO), whereas La aluminosilicate glasses have roughly constant O environments, even up to 8 GPa. Finally, we demonstrate that useful 23Na and 27Al MAS NMR spectra can be collected for Ca-Na aluminosilicate glasses containing up to 5 wt.% Fe oxide. We discuss the types of structural changes that may accompany density increases with pressure and how these structural changes are affected by the presence of different cations.

Kelsey, Kimberly E.; Stebbins, Jonathan F.; Singer, David M.; Brown, Gordon E., Jr.; Mosenfelder, Jed L.; Asimow, Paul D.

2009-07-01

228

Calculation of the Aluminosilicate Half-Life Formation Time in the 2H Evaporator  

SciTech Connect

The 2H Evaporator contains large quantities of aluminosilicate solids deposited on internal fixtures. The proposed cleaning operations will dissolve the solids in nitric acid. Operations will then neutralize the waste prior to transfer to a waste tank. Combining recent calculations of heat transfer for the 2H Evaporator cleaning operations and laboratory experiments for dissolution of solid samples from the pot, the authors estimated the re-formation rate for aluminosilicates during cooling. The results indicate a half-life formation of 17 hours when evaporator solution cools from 60 degrees C and 9 hours when cooled from 90 degrees C.

Fondeur, F.F.

2000-09-21

229

Tribochemical reactions of erionite and Na-LTA zeolites with Fe2(SO4)3.5H2O: A mssbauer study  

NASA Astrophysics Data System (ADS)

The tribochemical reactions between Na-LTA and natural erionite with Fe2(SO4)35H2O were studied by Mssbauer spectroscopy, X-ray powder diffraction, IR spectroscopy and NH3 adsorption experiments. The reactions occur with the consequent zeolite dealumination and the formation of a crystalline compound, a product of the extracted aluminum and the sulfate.

de Oate Martnez, J.; Aguila, C. Daz; Bertrn, J. Fernndez; Ruz, E. Reguera; Vergara, C. Portilla; Malherbe, R. Roque

1992-10-01

230

Liquid crystalline bispropargyl thermosets  

SciTech Connect

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

Langlois, D.A.; Benicewicz, B.C. [Los Alamos National Lab., NM (United States). Polymers and Coatings Group; Douglas, E.P. [Univ. of Florida, Gainesville, FL (United States). Dept. of Materials Science and Engineering

1998-11-01

231

Liquid-crystalline terpyridines.  

PubMed

5,5"-Disubstitution of the terpyridine core leads to the first inherently liquid-crystalline terpyridines. Mesophases characteristic of bent-core and calamitic systems may be obtained depending on the core structure employed. PMID:18217660

Kozhevnikov, Valery N; Whitwood, Adrian C; Bruce, Duncan W

2007-10-01

232

Liquid Crystalline Polymers.  

National Technical Information Service (NTIS)

This research produced the first quantitative approach to the elucidation of the structure-properties relationship in the field of side chain liquid crystalline polymers via a molecular engineering approach. The elucidation of the mechanisms required for ...

V. Percec

1995-01-01

233

The potential application of natural zeolite for greywater treatment  

Microsoft Academic Search

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

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

2008-01-01

234

Synthesis of Higher Aluminum Content Hexagonal and Cubic Mesoporous Aluminosilicates toward Catalysts  

Microsoft Academic Search

High aluminum content (Si\\/Al 27A1 MAS NMR, temperature-programmed desorption of ammonia and element analysis. The in situNMR technique was used to investigate the mechanism of the formation of the high aluminum content mesoporous aluminosilicates. The salt effect was also discussed in this work.

Chunlei Wang; Guangshan Zhu; Xiaohui Cai; Tiecun Shang; Lan Zhao; Nan Li; Runwei Wang; Yuhong Wei; Jian Li; Shilun Qiu

2005-01-01

235

Sol-gel zirconia coatings aimed at dust suppression in aluminosilicate high temperature insulating blankets  

Microsoft Academic Search

The feasibility of reducing the amount of loftable fibres in aluminosilicate blankets by coating with sol-gel zirconia was studied. A zirconium alkoxide based solution was employed to coat small samples of blanket using a dip-coating technique. The zirconia coatings and two grades of blanket were analysed using DTA, XRD, SEM and optical microscopy techniques to characterize any reactions and phase

B. Ben-Nissan; D. Martin

1996-01-01

236

Adsorption of small organic pollutants from aqueous streams by aluminosilicate-based microporous materials  

Microsoft Academic Search

Organic pollution in industrial waste streams is of growing environmental concern. Adsorption has been applied to remove organics from aqueous solutions. Activated carbon and polymer resin are the most commonly used adsorbents. In this work, a novel class of aluminosilicate-based microporous materials with good adsorption capacity and high selectivity are investigated.In order to adsorb organic molecules selectively from aqueous solution,

Huai-Te Shu; Danyun Li; Alfred A. Scala; Yi Hua Ma

1997-01-01

237

State-of-the-art alumino-silicate refractories for al electrolysis cells  

NASA Astrophysics Data System (ADS)

The refractory material of choice for aluminum cell bottom linings worldwide is alumino-silicates, due to high availability, relatively low cost, and empirically good performance. During operation of aluminum electrolysis cells, the alumino-silicates are subjected to infiltration and attack by molten electrolyte components. The penetration of sodium and molten fluorides through the cathode causes significant mineralogical transformation in the refractory, and, in extreme situations, it may terminate the pot life. This paper reviews the current understanding of deterioration mechanisms for refractory materials used in bottom lining of aluminum reduction cells. The silica content of the alumino-silicate refractories is the major single factor affecting deterioration rates through the formation of viscous melts and a glass-like barrier in the reacted lining. In addition, reactions between metallic sodium and alumino-silicate refractories may cause volume expansions in the exposed lining. The present review concludes that firebricks with an optimum silica content are probably still the best penetration barriers available.

Siljan, Ole-Jacob; Schoning, Christian; Grande, Tor

2002-05-01

238

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

PubMed

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

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

2003-10-21

239

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

240

Fictive temperature-independent density and minimum indentation size effect in calcium aluminosilicate glass  

Microsoft Academic Search

Using the calcium aluminosilicate system a glass was developed that exhibits fictive temperature-independent density by creating an intermediate glass between normal and anomalous glasses. Normal glass, such as soda-lime silicate glass, exhibits decreasing density with increasing fictive temperature while anomalous glass, such as silica glass, exhibits increasing density with increasing fictive temperature. This intermediate glass composition was found to exhibit

T. M. Gross; M. Tomozawa

2008-01-01

241

Long Fluorescence Lifetime of Ti3+-Doped Low Silica Calcium Aluminosilicate Glass  

Microsoft Academic Search

This Letter reports the formation of Ti3+ in OH- free aluminosilicate glass melted under vacuum condition, with a very long lifetime (170mus) 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

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

2008-01-01

242

Surface of a calcium aluminosilicate glass by classical and ab initio molecular dynamics simulations  

Microsoft Academic Search

We present the structural properties of thin films of a calcium aluminosilicate glass generated by classical molecular dynamics (MD). The films are generated by two methods: in the first, the films are created in the liquid state and quenched to 300K; in the second, the films are generated at room temperature. Depending on the method, film thickness and surface roughness

Patrick Ganster; Magali Benoit; Jean-Marc Delaye; Walter Kob

2008-01-01

243

Physical performances of blended cements containing calcium aluminosilicate glass powder and limestone  

Microsoft Academic Search

This work explores the suitability of calcium aluminosilicate (CAS) glass particles as an alternative to conventional supplementary cementitious materials (SCMs) such as fly ash and blast furnace slag. The reason for adding CAS glass particles to the cement blend is to reduce the CO2 emission of cement production at the same level of performance. For this purpose, blended cement mortars

Mette Moesgaard; Duncan Herfort; Mette Steenberg; Lise Frank Kirkegaard; Yuanzheng Yue

2011-01-01

244

Interface characterization and fracture of calcium aluminosilicate glass-ceramic reinforced with nicalon fibres  

Microsoft Academic Search

An investigation of the structure and properties of a calcium aluminosilicate glass-ceramic reinforced with Nicalon fibres is described. Microstructural analysis of the interface showed that during manufacture of the composite a reaction zone rich in carbon formed between the Nicalon fibre and the anorthite matrix. Tensile strengths were approximately 330 MPa for unidirectional material and around 210 MPa for a

S. M. Bleay; V. D. Scott; B. Harris; R. G. Cooke; F. A. Habib

1992-01-01

245

Chemical dependence of network topology of calcium aluminosilicate glasses: a computer simulation study  

Microsoft Academic Search

Molecular dynamics and reverse Monte Carlo simulations are used to investigate the structure of calcium aluminosilicate glasses with low silica content. The polymerized network is close to that expected from a random distribution for all compositions with important amount of AlOAl linkages. Minor species such as triclusters and free oxygen atoms are present. The main structural variations are the changes

Laurent Cormier; Dominique Ghaleb; Daniel R. Neuville; Jean-Marc Delaye; Georges Calas

2003-01-01

246

Rare-earth doped low silica calcium aluminosilicate glasses for near and mid infrared applications  

Microsoft Academic Search

The combination of properties such as chemical durability, transformation temperature, thermo-mechanical properties, refractory properties, phonon energy of about 800 cm?1 and infrared transparency up to 6 ?m, recommend low silica (<7 wt%) calcium aluminosilicate glasses as hosts for laser applications. We have been investigating the physical properties of these glasses prepared by melting under vacuum conditions. This preparation procedure ensured

M. L. Baesso; A. C. Bento; L. C. M. Miranda; D. F. de Souza; J. A. Sampaio; L. A. O. Nunes

2000-01-01

247

Lithium aluminosilicate reinforced with carbon nanofiber and alumina for controlled-thermal-expansion materials  

Microsoft Academic Search

Materials with a very low or tailored thermal expansion have many applications ranging from cookware to the aerospace industry. Among others, lithium aluminosilicates (LAS) are the most studied family with low and negative thermal expansion coefficients. However, LAS materials are electrical insulators and have poor mechanical properties. Nanocomposites using LAS as a matrix are promising in many applications where special

Amparo Borrell; Olga Garca-Moreno; Ramn Torrecillas; Victoria Garca-Rocha; Adolfo Fernndez

2012-01-01

248

Mesoporous aluminosilicate nanocage-catalyzed three-component coupling reaction: an expedient synthesis of ?-aminophosphonates  

Microsoft Academic Search

Here we demonstrate for the first time the synthesis of ?-aminophosphonates through the three-component coupling reaction of aldehydes, amines, and diethyl phosphite by using highly acidic 3D mesoporous aluminosilicate nanocage catalyst, which gave excellent yield with a high selectivity in a short reaction time due to its high acidity, 3D pores, and a huge space in the nanocages.

Ajayan Vinu; Pranjal Kalita; Veerappan V. Balasubramanian; Hamid Oveisi; Tamil Selvan; Ajayan Mano; Murugulla A. Chari; B. V. Subba Reddy

2009-01-01

249

Zeolite-based discriminating gas sensors  

Microsoft Academic Search

The use of zeolites to enhance the discriminating power of solid state gas sensors is demonstrated. Screen printed tungsten trioxide (WO3) and chromium titanium oxide (CTO) thick films overlaid and admixed (CTO only) with different forms of zeolites are shown to give different and in some cases, enhanced responses to a variety of gases. We attempt to rationalise the noted

Sheena Dungey; Ayo Afonja; Dewi W. Lewis; Russell Binions; Ivan P. Parkin; Themis Paraskeva; David E. Williams

2008-01-01

250

Hydrophilic and hydrophobic adsorption on Y zeolites  

Microsoft Academic Search

The uniform large micropores of hydrothermally stable Y zeolites are used widely to confine both polar and non-polar molecules. This paper compares the physisorption of water, methanol, cyclohexane, benzene and other adsorbates over various Y zeolites. These adsorbents are commercial products with reproducibly controllable physical and chemical characteristics. Results indicate that the type I isotherms typical for micropore adsorption can

Istvan Halasz; Song Kim; Bonnie Marcus

2002-01-01

251

The flexibility of zeolites for Hydrogen storage  

NASA Astrophysics Data System (ADS)

The flexibility window is a newly discovered theoretical measure which can provide a valuable selection criterion when evaluating hypothetical zeolite framework structures as potential synthetic targets. Today synthetic zeolites are the most important catalysts in petrochemical refineries. There have been considerable efforts to synthesize new zeolites with specific pore geometries, to add to the 167 available at present. Millions of hypothetical structures have been generated on the basis of energy minimization, and there is an ongoing search for criteria capable of predicting new zeolite structures. The flexibility window appears to be a property of existing zeolite frameworks not shared by many hypothetical structures. It provides a valuable selection criterion when evaluating hypothetical zeolite framework structures as potential synthetic targets. We are investigating the use of zeolites as hydrogen storage materials, as small molecules such as molecular hydrogen and ammonia can be easily absorbed into a flexible framework of zeolites. An exiting possibility is the use of framework flexibility to control hydrogen uptake, storage and release. This would allow a safe use of hydrogen for fuel cells.

Sartbaeva, Asel; Wells, Stephen Anthony; Edwards, Peter P.

2008-03-01

252

Chemical Interactions in Multimetal\\/Zeolite Catalysts  

Microsoft Academic Search

This two-year project has led to a significant improvement in the fundamental understanding of the catalytic action of zeolite-supported redox catalysts. It turned out to be essential that we could combine four strategies for the preparation of catalysts containing transition metal (TM) ions in zeolite cavities: (1) ion exchange from aqueous solution; (2) chemical vapor deposition (CVD) of a volatile

Sachtler; Wolfgang M. H

2004-01-01

253

Design of zeolite by inverse sigma transformation  

NASA Astrophysics Data System (ADS)

Although the search for new zeolites has traditionally been based on trial and error, more rational methods are now available. The theoretical concept of inverse ? transformation of a zeolite framework to generate a new structure by removal of a layer of framework atoms and contraction has for the first time been achieved experimentally. The reactivity of framework germanium atoms in strong mineral acid was exploited to selectively remove germanium-containing four-ring units from an UTL type germanosilicate zeolite. Annealing of the leached framework through calcination led to the new all-silica COK-14 zeolite with intersecting 12- and 10-membered ring channel systems. An intermediate stage of this inverse ? transformation with dislodged germanate four-rings still residing in the pores could be demonstrated. Inverse ? transformation involving elimination of germanium-containing structural units opens perspectives for the synthesis of many more zeolites.

Verheyen, Elke; Joos, Lennart; van Havenbergh, Kristof; Breynaert, Eric; Kasian, Nataliia; Gobechiya, Elena; Houthoofd, Kristof; Martineau, Charlotte; Hinterstein, Manuel; Taulelle, Francis; van Speybroeck, Veronique; Waroquier, Michel; Bals, Sara; van Tendeloo, Gustaaf; Kirschhock, Christine E. A.; Martens, Johan A.

2012-12-01

254

Entropic inflation of ideal zeolitic frameworks  

NASA Astrophysics Data System (ADS)

Ideal zeolites can be viewed as flexible networks of rigid, corner-sharing tetrahedra. Recent studies have shown that such systems can exist at a range of densities (termed the "flexibility window") without breaking topology or deforming the comprising tetrahedra. They also have shown that densities of real zeolites almost always correspond to the lowest densities within this range. This anomalous behavior is usually attributed to coulombic repulsion between oxygen atoms in framework cavities and channels. In this paper we show that the inflation of ideal zeolites can be driven by entropy. This effect is closely related to displacive phase transitions often observed in zeolites and related materials like quartz, which cannot be explained by potential energy minimization alone. We show that periodicity and high symmetry in ideal zeolites is a result of entropy maximization. An estimation of entropy using a harmonic oscillator model with a realistic force field is given.

Kapko, Vitaliy; Dawson, Colby; Treacy, Michael

2011-03-01

255

Evidence of energy transfer in an aluminosilicate glass codoped with Si nanoaggregates and Er{sup 3+} ions  

SciTech Connect

The enhancement of the Er{sup 3+} ions' photoluminescence (PL) emission at 1.54 {mu}m in a Si and Er coimplanted aluminosilicate glass is investigated in detail. A postimplantation thermal treatment has been performed to recover the damage induced by the implantation process and to promote Si aggregation. It will be shown that 1 h treatment in N{sub 2} atmosphere is not sufficient to induce Si precipitation for temperatures up to 500 deg. C. Nevertheless, the most intense Er{sup 3+} PL emission at 1.54 {mu}m is achieved after a thermal treatment at 400 deg. C. Such emission has been investigated by pumping in and out of resonance, showing a very efficient energy transfer process in the whole excitation wavelength range (360-515 nm). These results suggest that good energy transfer mediators could be small Si aggregates and not only crystalline clusters. For the best performing sample, the effective Er excitation cross section has been measured to be higher than 10{sup -17} cm{sup 2} at 379 and 390 nm and about 2x10{sup -16} cm{sup 2} at 476 nm, that is, several orders of magnitude higher than the Er direct absorption cross section (of the order of 10{sup -21} cm{sup 2} in this glass). Moreover the coefficient of cooperative upconversion has been evaluated to be 2.7x10{sup -18} cm{sup 3} s{sup -1}. The structural and optical properties of this material are discussed and compared to those found for Si and Er codoped silica.

Enrichi, F.; Mattei, G.; Sada, C.; Trave, E.; Pacifici, D.; Franzo, G.; Priolo, F.; Iacona, F.; Prassas, M.; Falconieri, M.; Borsella, E. [INFM, Dipartimento di Fisica, Universita di Padova, via Marzolo 8, 35131 Padova (Italy); INFM-MATIS, Dipartimento di Fisica e Astronomia, Universita di Catania, via S. Sofia 64, 95123 Catania (Italy); CNR-IMM, Stradale Primosole 50, I-95121 Catania (Italy); Advanced Materials for Photonics, Corning SA, 7 bis Avenue de Vilvins Boite Postale No. 3, Avon (France); ENEA, via Anguillarese 301, 00060 Casaccia (Italy); ENEA, via E. Fermi 45, 00044 Frascati (Italy)

2004-10-01

256

Zeolite inorganic supports for BSA immobilization: comparative study of several zeolite crystals and composite membranes.  

PubMed

Zeolites due to their low toxicity and high compatibility are considered new biomaterials for medical applications. The surface adsorption behaviour of zeolite crystals and composite membranes was discussed in this research. The zeolite materials were synthesized by hydrothermal syntheses using different reaction gels to modulate the Brnsted acidity of the microporous structures. Spectrophotometric analyses were used to evaluate protein adsorption on these surfaces. This study revealed that zeolite chemical composition and structure influenced the kinetics of protein adsorption. Zeolite Y surface adsorbed greater amount of BSA than the other structures. The percentage of adsorption increases with temperature and depends on the pH of the solution, being highest at the pI of the protein. The influence of the membrane configuration on the protein adsorption was studied using different zeolite structures and crystallization types. It seems that the observed differences could depend on the type of hydrothermal crystallization inside the inorganic support. PMID:17194574

Tavolaro, Adalgisa; Tavolaro, Palmira; Drioli, Enrico

2006-11-17

257

Zeolite catalyst deactivation by coking  

SciTech Connect

Deactivation of a lanthanum exchanged zeolite Y catalyst for isopropylbenzene (cumene) cracking was studied with a thermobalance. The kinetics of coke formation and the main reaction were determined. The Froment Bischoff approach to modeling catalyst deactivation was used. The deactivation function giving the best fit to both the cracking and coking reaction data was an exponential one related to the coke content of the catalyst. The kinetic mechanism for coking that gave the best fit was one in which parallel and consecutive coking reactions occurred simultaneously. Apparently, more coke forms from products than reactants, especially at higher temperature.

Lin, C.C.; Hatcher, W.J.; Park, S.W.

1983-10-01

258

17O NMR Studies of Zeolites  

NASA Astrophysics Data System (ADS)

Multiple-quantum magic-angle spinning (MQMAS) and double rotation (DOR) techniques were applied in the fields of 17.6 T and 11.7 T to the study the 17O NMR of oxygen-17 enriched zeolites A, LSX and sodalite. In addition, some 29Si and 1H MAS NMR experiments were performed. Zeolites with the ratio Si/Al = 1 were chosen, in order to have an alternating distribution of silicon and aluminum atoms. A linear correlation between the isotropic value of the chemical shift and the Si-O-Al bond angle (taken from X-ray data) could be found for the zeolites A and LSX, but not for sodalites. Hydration of the zeolites causes a downfield 17O NMR chemical shift of about 8 ppm with respect to the dehydrated zeolites. Ion exchange of the hydrated zeolites generates stronger chemical shift effects. The increase of the basicity of the oxygen framework of the zeolite LSX is reflected by a downfield shift of ca. 10 ppm going from the lithium to the cesium form, and the substitution of sodium by thallium in the zeolite A causes a shift of 34 ppm for the O3 site. 17O DOR NMR spectra are superior to 17O 3QMAS NMR spectra, featuring a resolution increase by a factor of two and are about equal with respect to the sensitivity. The residual linewidths of the signals in the 17O DOR and 17O 5QMAS NMR spectra can be explained by a distribution of the Si-O-Al angles in the zeolites.

Freude, Dieter; Loeser, Thomas

259

Influence of Boehmite Precursor on Aluminosilicate Aerogel Pore Structure, Phase Stability and Resistance to Densification at High Temperatures.  

National Technical Information Service (NTIS)

Aluminosilicate aerogels are of interest as constituents of thermal insulation systems for use at temperatures higher than those attainable with silica aerogels. It is anticipated that their effectiveness as thermal insulators will be influenced by their ...

F. I. Hurwitz H. Guo K. N. Newlin

2011-01-01

260

Thermomechanical Fatigue Behavior of a Silicon Carbide Fiber-Reinforced Calcium Aluminosilicate Glass-Ceramic Matrix Composite.  

National Technical Information Service (NTIS)

Isothermal fatigue and in-phase thermomechanical fatigue (TMF) tests were performed on a unidirectional, continuous-fiber, Nicalon - reinforced calcium aluminosilicate glass-ceramic composite (10116, SiC/CAS-II). Monotonic tensile tests were performed; at...

L. M. Butkus

1992-01-01

261

Multinuclear NMR Study of Aluminosilicate Sol-Gel Synthesis Reasons for the Homogeneous Gelation Using the Prehydrolysis Method.  

National Technical Information Service (NTIS)

Aluminosilicate gels have been utilized in numerous optical, dielectric, and catalytic applications. These applications require a high degree of molecular homogeneity, but reproducible means of achieving this remain unobtainable for many compositions. In ...

G. A. Pozarnsky A. V. McCormick

1993-01-01

262

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

263

Photoinduced electron transfer reactions in zeolite cages  

SciTech Connect

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

Dutta, P.K.

1992-01-01

264

Zeolite based arsine storage and delivery system  

SciTech Connect

A method of storing and subsequently delivering arsine is described, which comprises the steps of: (a) contacting arsine at a temperature of between about -30/sup 0/C and about +30/sup 0/C with a zeolite having a pore size of between about 5 and about 15 angstroms to provide arsine-adsorbed zeolite suitable to be stored, and (b) heating the arsine-adsorbed zeolite to an elevated temperature of no greater than about 175/sup 0/C for a time sufficient to release at least a portion of the adsorbed arsine to provide free arsine.

Knollmueller, K.O.

1988-05-17

265

Gas adsorption isotherm for dealuminated zeolites  

SciTech Connect

Adsorption is a current technique to remove volatile organic compounds from process gas streams. In industrial applications hydrophobic dealuminated zeolites are often used as adsorbents, because of their specific advantages in comparison to activated carbon or polar zeolites. A new equation for complex adsorption isotherms was developed by using a mathematical method well-known in control engineering. On the basis of this analogy, it is possible to describe the transitional region between Langmuir isotherms and isotherms following Henry`s law. Development and verification of the equation are based on experimental data of the system zeolite DAY-ethanol-air.

Bathen, D.; Schmidt-Traub, H.; Simon, M. [Univ. of Dortmund (Germany). Dept. of Chemical Engineering

1997-09-01

266

Luminescence quenching measurements on zeolite L monolayers  

NASA Astrophysics Data System (ADS)

The luminescence quenching of the oxygen sensitive Ru2+ complex (Ru-ph4-TMS) used as a stopcock and attached to a zeolite L monolayer has been investigated. The luminescence lifetime of the attached Ru-ph4-TMS was the same under N2 and under O2 atmosphere. This remarkable result is attributed to the shielding provided by the channels of the zeolite L crystals arranged as a monolayer. The emitting 3MLCT state of the Ru-ph4-TMS stopcock is localized on the ligand bearing the phenyl groups forming the tail of this complex, which deeply penetrates into the zeolite L channel.

Albuquerque, Rodrigo Q.; Zabala Ruiz, Arantzazu; Li, Huanrong; De Cola, Luisa; Calzaferri, Gion

2006-05-01

267

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

Microsoft Academic Search

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

Farouq A. Twaiq; Abdul Rahman Mohamed; Subhash Bhatia

2003-01-01

268

Temperature effects on non-bridging oxygen and aluminum coordination number in calcium aluminosilicate glasses and melts  

Microsoft Academic Search

Configurational changes with temperature are important for the thermodynamic and transport properties of most aluminosilicate melts, but in general are not well understood. Here, we present high-resolution 27Al and 17O NMR data on several calcium aluminosilicate glasses prepared with varying quench rates and thus with fictive temperatures that span ranges up to about 200K. In all compositions the content of

Jonathan F. Stebbins; Emily V. Dubinsky; Koji Kanehashi; Kimberly E. Kelsey

2008-01-01

269

Room-temperature hole-burning and sublinear hole-growth dynamics in an Sm 2+-doped aluminosilicate glass  

Microsoft Academic Search

Aluminosilicate glasses doped with Sm2+-ion can exhibit hole-burning at room temperature. In this paper, we investigate the hole-growth dynamics of Sm2+-ion-doped aluminosilicate glasses prepared by the solgel method to reveal the hole-formation at room temperature. We found that the spectral holes exhibit Lorenz profiles. Hole-growth dynamics can be well fitted by the function H(t)=?t?. The hole-growth rate Kt decreases with

Hongwei Song; Masayuki Nogami

2002-01-01

270

An x-ray diffraction study of zeolite-containing metal silicates  

SciTech Connect

An x-ray diffraction study of zeolites and zeolite-containing metal silicates showed that a reaction occurs in the preparation of zeolite-containing systems between the zeolite crystallites and the metal silicate base, which depends on the means of the introduction of the zeolite in the chemical composition of the base and the zeolite.

Mel'nikov, V.B.; Chukin, G.D.; Netedov, B.K.

1986-10-01

271

Diffusion in crystalline materials  

Microsoft Academic Search

Recently nuclear scattering of synchrotron radiation proved to be a powerful new method to study the elementary diffusion jump in crystalline solids. The scattered radiation decays faster when atoms move on the time scale of the excited-state lifetime of a Mssbauer isotope because of a loss of coherence. The acceleration of the decay rate differs for different crystal orientations relative

G. Vogl; B. Sepiol

1999-01-01

272

Crystalline Xenon Particle Detector  

Microsoft Academic Search

The sensitivity necessary to measure single photon electrons may be achieved through ionization produced in a crystalline xenon based particle detector. Following crystal formation and the application of an electric field, the ionization drifts to the surface and can be extracted from the solid xenon. Quantification of the ions is accomplished by utilizing a silicon PIN diode scintillation detector with

J. A. Maxin; R. Blessitt; J. Gao; J. Miller; G. Salinas; J. Seifert; J. T. White

2004-01-01

273

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

274

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

SciTech Connect

The main parameters of aluminosilicate microspheres formed at thermal power stations in Russia were studied. These parameters are responsible for the prospective industrial application of these microspheres. A comparative analysis of the properties of mineral coal components, the conditions of coal combustion, and the effects of chemical and phase-mineralogical compositions of mineral impurities in coals from almost all of the main coal deposits on the formation of microspheres was performed. The effects of thermal treatment conditions on gas evolution processes in mineral particles and on the fraction of aluminosilicate microspheres in fly ash were considered. It was found that the yield of microspheres was higher in pulverized coal combustion in furnaces with liquid slag removal, all other factors being equal. The regularities of microsphere formation were analyzed, and the mechanism of microsphere formation in fly ash during the combustion of solid fuels was considered.

V.S. Drozhzhin; M.Ya. Shpirt; L.D. Danilin; M.D. Kuvaev; I.V. Pikulin; G.A. Potemkin; S.A. Redyushev [Russian Federal Nuclear Center VNIIEF, Nizhegorodskaya oblast (Russia)

2008-04-15

275

Molecular orbital calculations for modeling acetate-aluminosilicate adsorption and dissolution reactions  

SciTech Connect

Possible molecular configurations of acetic acid and acetate adsorbed onto aluminosilicate minerals are examined. Molecular orbital calculations were performed on molecules and dimers; that are intended to mimic inner sphere and outer sphere adsorption complexes on mineral surfaces. The results predict the structure, energetics, and vibrational spectra of the acetic acid and acetate bonded to alumino-silicate groups. The most likely surface complexes are determined by reaction energetics and comparison of theoretical to experimental vibrational spectra. In addition, a reaction pathway of Si-O-Al cleavage by acetic acid and chemisorption of acetate with tetrahedral Al{sup 3+} is predicted. An activation energy for this reaction is estimated from constrained energy minimizations of the reactants along a reaction pathway. 89 refs., 6 figs., 6 tabs.

Kubicki, J.D.; Apitz, S.E. [Naval Command Control and Surveillance Center, San Diego, CA (United States); Blake, G.A. [California Institute of Technology, Pasadena, CA (United States)

1997-03-01

276

Model for leaching behavior of aluminosilicate glasses developed as matrices for immobilizing high-level wastes  

SciTech Connect

A field trial initiated in 1960 has shown very low release rates of /sup 137/Cs and /sup 90/Sr from aluminosilicate glasses developed as potential matrices for the immobilization of radioactive fission products. Recent laboratory work in closed glass-water systems shows that certain sodium-calcium aluminosilicate glasses effectively cease to dissolve in water after a short time. This behavior is thought to be associated with the formation of a protective mineralized surface layer. Models were developed for the release of radionuclides from a glass covered by a mineralized surface layer, with leaching in both closed and open systems. The leaching equation for release in an open system is fitted to /sup 90/Sr release data.

Harvey, K.B.; Litke, C.D.

1984-08-01

277

Comparison of synthetic zeolite catalysts and alumina binders administered intratracheally to rats.  

PubMed

An intratracheal (IT) screening assay was performed in rats on a series of aluminosilicate catalysts (synthetic zeolites) and alumina binders to compare their relative ability to cause pulmonary fibrosis and related changes. Before initiation of IT screens, both the uniformity of deposition and residence time of a prototype catalyst in the lung were determined. Subsequently, the test materials were instilled and animals were evaluated 6 mo later for lung volumes, pulmonary pressure-volume curves, pulmonary hydroxyproline (OHPro) content, lung weights, and histopathology. Negative controls were saline and glass beads; the positive control was quartz. The test materials were organic-free ZSM-5 crystals, organic form of ZSM-5 crystals, alumina-bound ZSM-5, nickel/ZSM-5/ Al2O3 binder, used nickel/ZSM-5/Al2O3 binder, nickel-tungsten/ZSM-5/Al2O3 binder, and Bayer pseudoboehmite. For each, groups of 12 male rats were dosed once with either 25 or 50 mg of ground particles (> or =95% less than 2.4 microm). Second to quartz, the sample of alumina caused the most pronounced pulmonary reactions at 6 mo after dosing. Therefore, the effects of four aluminas were subsequently compared (Bayer pseudoboehmite, Bayer gammaAl2O3, Ziegler pseudoboehmite, and Ziegler gammaAl2O3). The results support the idea of a lack of long-term effects from exposure to normal concentrations of these materials in the workplace. Also, the IT assay proved to be a very useful tool for ranking the relative effects of this series of zeolites and aluminas. PMID:10912588

Dalbey, W E; Pulkowski, C

2000-07-14

278

Crystalline plutonium hosts derived from high-level waste formulations.  

SciTech Connect

The Department of Energy has selected immobilization for disposal in a repository as one approach for disposing of excess plutonium (1). Materials for immobilizing weapons-grade plutonium for repository disposal must meet the ''spent fuel standard'' by providing a radiation field similar to spent fuel (2). Such a radiation field can be provided by incorporating fission products from high-level waste into the waste form. Experiments were performed to evaluate the feasibility of incorporating high-level waste (HLW) stored at the Idaho Chemical Processing Plant (ICPP) into plutonium dispositioning materials to meet the spent fuel standard. A variety of materials and preparation techniques were evaluated based on prior experience developing waste forms for immobilizing HLW. These included crystalline ceramic compositions prepared by conventional sintering and hot isostatic pressing (HIP), and glass formulations prepared by conventional melting. Because plutonium solubility in silicate melts is limited, glass formulations were intentionally devitrified to partition plutonium into crystalline host phases, thereby allowing increased overall plutonium loading. Samarium, added as a representative rare earth neutron absorber, also tended to partition into the plutonium host phases. Because the crystalline plutonium host phases are chemically more inert, the plutonium is more effectively isolated from the environment, and its attractiveness for proliferation is reduced. In the initial phase of evaluating each material and preparation method, cerium was used as a surrogate for plutonium. For promising materials, additional preparation experiments were performed using plutonium to verify the behavior of cerium as a surrogate. These experiments demonstrated that cerium performed well as a surrogate for plutonium. For the most part, cerium and plutonium partitioned onto the same crystalline phases, and no anomalous changes in oxidation state were observed. The only observed difference in behavior between cerium and plutonium was that plutonium partitioned more completely into the major host phases than cerium. Where cerium was sometimes observed at up to a few atom percent in crystalline or glassy phases, plutonium could not be detected in these phases. The crystalline plutonium host phases identified in this work included zirconolite, cubic zirconia, sphene, and an anorthite-like calcium aluminosilicate. Zirconia has been suggested as a possible material for immobilizing actinides (3), but this appears to be the first synthesis of such a material. Plutonium appears to stabilize the cubic (fluorite) structure through abroad solid solution range. Samarium can also be incorporated into this material, but is not necessary to stabilize the cubic structure. Plutonium leach rates, as measured by the Product Consistency Test (4), were on the order of 10{sup {minus}5} to 10{sup {minus}6} g/m{sup 2}/day.

O'Holleran, T. P.

1998-04-24

279

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

280

Pressure dependence of elastic properties of low-silica calcium alumino-silicate glasses  

Microsoft Academic Search

The hydrostatic and uni-axial pressure dependence of elastic properties of a low-silica calcium alumino-silicate glass (LSCAS) is determined by ultrasonic pulse-echo techniques at room temperature. The experimental results are used to obtain the third-order elastic constants (TOECs) of these glasses. The pressure dependence of fractal bond connectivity of these glasses is discussed. The normal behavior of positive pressure dependence of

W. C. Chao; Paul. W. Wang; L. G. Hwa

2008-01-01

281

Radiative properties of Nd-doped transparent glass-ceramics in the lithium aluminosilicate system  

Microsoft Academic Search

We have studied the optical (absorption, luminescence) properties of Nd3+-doped transparent glass-ceramics obtained in the lithium aluminosilicate system. Phase composition of the glass-ceramics has been determined to affect their luminescent characteristics. We have found out that concentration quenching of neodymium fluorescence decreases upon recrystallization of ?-eucryptite solid solutions (SS) into ?-spodumene ones. The effect is due to partitioning of the

U. Kang; T. I Chuvaeva; A. A Onushchenko; A. V Shashkin; A. A Zhilin; Hee-Je Kim; Yung-Gi Chang

2000-01-01

282

``Central Atoms'' models for ternary silicate and alumino-silicate melts  

NASA Astrophysics Data System (ADS)

The Central Atoms model presented by the authors in an earlier paper is extended to ternary silicate and alumino-silicate melts. The model is applied to the CaO-FeO-SiO2 and the CaO-Al2O3-SiO2 system. Use is made of the parameters from the relevant binaries only. The agreement between experimental and calculated isoactivity curves is good in all cases.

Sastri, P.; Lahiri, A. K.

1986-01-01

283

Aluminosilicate ceramic proppant for gas and oil well fracturing and method of forming same  

Microsoft Academic Search

An aluminosilicate ceramic product or article and a method of forming the article from as-mined ore. The product is useful as a proppant in gas and oil well fracturing. The ratio, on a calcined basis, of alumina to silica is between approximately 2.2 to 4.0. The amount of iron in the product is controlled as a function of the alumina

D. R. Watson; V. G. Carithers; L. T. McDaniel

1985-01-01

284

Sodium sulfate hot corrosion of silicon carbide fiber-reinforced calcium aluminosilicate. Master`s thesis  

Microsoft Academic Search

The effects of sodium sulfate hot corrosion on the microstructure of silicon carbide fiber-reinforced calcium aluminosilicate glass-ceramic matrix composite were investigated using optical microscopy, scanning electron microscopy (SEM) and x-ray diffraction (XRD). Hot corrosion of samples at 900 deg C for 50 hours in both air and argon was investigated. SEM and XRD investigations of the sample exposed in air

Oppici

1995-01-01

285

A Comparative Study of Surface Characteristics of Nickel Supported on Silica Gel, ?-Alumina, Aluminosilicate  

Microsoft Academic Search

Surface characteristics of the prepared nickel catalysts containing 7, 10, and 13 wt% Ni w\\/w over different supportssilica gel, ?-alumina, and aluminosilicatewere investigated. Surface areas, total pore volumes, and average pore radii were determined for all catalysts. Pore analysis was discussed based on Vl-t plots and pore size distribution. The measured surface areas and pore volumes of pure supports increased

H. M. Gobara; S. A. Hassan

2009-01-01

286

Synthesis of co-containing aluminosilicates with a microporous layered columnar structure from montmorillonite clays  

NASA Astrophysics Data System (ADS)

The conditions of synthesis of cobalt-containing aluminosilicates with a microporous layered columnar structure from montmorillonite clays were correlated with their texture characteristics. The main factors governing the texture properties of the material were shown to be the montmorillonite content in natural clay, the calcination temperature, and the type of hydrolyzing agent and OH-: Me n+ ratio during the preparation of the modifying solution.

Kon'kova, T. V.; Alekhina, M. B.; Rysev, A. P.

2013-10-01

287

27Al and 29Si MASNMR studies of structural changes in hybrid aluminosilicate gels  

Microsoft Academic Search

Aluminosilicate gels with stoichiometric and nonstoichiometric compositions were synthesized by means of colloidal sol-gel method and their mullitization behavior was studied by X-ray diffraction (XRD), 27Al and 29Si magic angle spinning nuclear magnetic resonance (MASNMR) experiments. Particular attention was given to the structural changes of matrix accompanying the formation of mullite. The various coordinated Al occupancies were clarified by simulating

Hailei Zhao; Keisuke Hiragushi; Yasuo Mizota

2002-01-01

288

Aluminum speciation, vibrational entropy and short-range order in calcium aluminosilicate glasses  

Microsoft Academic Search

The heat capacity and vibrational entropy of a calcium aluminate and three peraluminous calcium aluminosilicate glasses have been determined from 2 to 300K by heat-pulse relaxation calorimetry. Together with previous adiabatic data for six other glasses in the system CaOAl2O3SiO2, these results have been used to determine partial molar heat capacities and entropies for five species namely, SiO2, CaO and

Pascal Richet; Atsusi Nidaira; Daniel R. Neuville; Tooru Atake

2009-01-01

289

Laser emission at 1077nm in Nd3+-doped calcium aluminosilicate glass  

Microsoft Academic Search

Laser emission at 1077nm ( 4 F 3\\/2? 4 I 11\\/2) was demonstrated in Nd 3+-doped low silica content calcium aluminosilicate (LSCA) glass under 810-nm pumping by a Ti:sapphire laser. The slope efficiency of the laser emission was found to be 34% with a 20-mW threshold power. The excited-state absorption (ESA) and stimulated emission were measured between 850 and 1520nm.

D. F. de Sousa; L. A. O. Nunes; J. H. Rohling; M. L. Baesso

2003-01-01

290

The elevated temperature compression creep behavior of a calcium-aluminosilicate(anorthite) glass ceramic  

Microsoft Academic Search

An experimental investigation of compression creep in a calcium-aluminosilicate glass ceramic revealed that the deformation can be expressed as [epsilon][alpha][sigma][sup 1]exp([minus]650 kJ mol[sup [minus]1]\\/RT), where [epsilon] is the steady state strain rate, [sigma] is the imposed stress, R is the gas constant and T is the absolute temperature. The high activation energy, a stress exponent of unity and microstructural observations

R. F. Mercer; A. H. Chokski

1993-01-01

291

Spectroscopic properties of water free Nd 2O 3-doped low silica calcium aluminosilicate glasses  

Microsoft Academic Search

In this work, low silica calcium aluminosilicate glasses (LSCA) doped with different concentrations of Nd2O3 were prepared under vacuum conditions and investigated through spectroscopic measurements. UV, visible and near IR optical absorption spectra, IR luminescence spectra, and fluorescent time decay were measured. JuddOfelt model was used in conjunction with these data to calculate intensity parameters (?2,?4 and ?6), emission cross-section,

E. Pecoraro; J. A. Sampaio; L. A. O. Nunes; S. Gama; M. L. Baesso

2000-01-01

292

Aluminum coordination and density of 4 and 5 component high-pressure aluminosilicate glasses  

NASA Astrophysics Data System (ADS)

The density and viscosity of silicate melts are strongly dependent on pressure and composition, owing in part to atomic-scale structural changes that occur at high pressure. In an attempt to further understand these changes, we have used Al-27 MAS NMR to determine the speciation of the aluminum cations and measured the density of glasses quenched from four and five component aluminosilicate melts in the pressure range of 2 to 8 GPa. Our previous work on ternary aluminosilicate glasses (Allwardt et al., 2005) established that high field strength (i.e., Ca) modifier cations induce more high-coordinated Al than lower field strength (i.e., Na and K) cations and the amount of high-coordinated Al gradually increases with increasing synthesis pressure to percentages as high as 81 % for the Ca-aluminosilicate glass at 10 GPa. Density determinations show that they are also up to 16 % more dense than the ambient pressure glass and that the density and the Al-coordination show a linear correlation. Quantification of spectra from the present study shows an increasing Al-coordination with increasing average field strength of modifier cation. These data also show that when multiple modifier cations are present (e.g. Ca and K), the Al coordination is lower than what would be expected due to linear mixing of the appropriate aluminosilicate endmembers. This experimental observation likely suggests that mixing of modifier cations in specific structural sites influences the formation of high coordinated Al in high-pressure glasses and melts.

Allwardt, J. R.; Stebbins, J. F.; Du, L.; Frost, D. J.; Withers, A. C.; Hirschmann, M. M.

2005-12-01

293

Nd2O3 doped low silica calcium aluminosilicate glasses: Thermomechanical properties  

Microsoft Academic Search

The effects of Nd2O3 doping on the thermal and mechanical properties of vacuum melted, low silica, calcium aluminosilicate glasses are presented. For the doped glasses, the vitrification limit was found to correspond to a maximum load of 5 wt % Nd2O3. The influence of the rare earth doping on the thermal diffusivity, thermal conductivity, and Vickers hardness was such that

M. L. Baesso; A. C. Bento; A. R. Duarte; A. M. Neto; L. C. M. Miranda; J. A. Sampaio; T. Catunda; S. Gama; F. C. G. Gandra

1999-01-01

294

Defect-mediated self-diffusion in calcium aluminosilicate glasses: A molecular modeling study  

Microsoft Academic Search

The mechanism of self-diffusion in calcium aluminosilicate glasses is investigated at the atomistic level using molecular dynamics (MD) simulations. We study nine glass compositions having the fixed ratio R=[CaO]\\/[Al2O3]=1 and the concentration of SiO2 varied from 11.8 to 76.5mol%. The diffusion coefficient is calculated for each composition at different temperatures from 300 to 6000K in steps of 300K. The self-diffusivities

Adama Tandia; Nikolay T. Timofeev; John C. Mauro; K. Deenamma Vargheese

2011-01-01

295

Fluorescence quantum efficiency in Nd2O3-doped aluminosilicate glasses by multiwavelength thermal lens method  

NASA Astrophysics Data System (ADS)

In this work the multiwavelength thermal lens method is applied to determine the absolute value of fluorescence quantum efficiency of low silica calcium aluminosilicate glasses doped with different concentrations of neodymium dioxide melted under vacuum condition. The experiments were performed using five different excitation wavelengths: 514, 532, 750, 810 and 890 nm. The results were in agreement with those provided by the Judd-Ofelt model.

Astrath, N. G. C.; Rohling, J. H.; Bento, A. C.; Baesso, M. L.; Jacinto, C.; Lima, S. M.; Nunes, L. A. O.; Catunda, T.

2005-06-01

296

Rare earth doping effect on the elastic moduli of low silica calcium aluminosilicate glasses  

Microsoft Academic Search

Elastic moduli (E, G, K, ?) of calcium aluminosilicate glasses with <10 mol% of SiO2 doped with Er2O3 and Yb2O3, melted in air and under vacuum conditions, have been measured using the pulse echo ultrasonic technique. There was a decrease of the elastic properties, <5%, as rare earth oxide replaces Al2O3 from 0.2 to 1.5 mol% (about 8 wt%). The

J. A. Sampaio; M. L. Baesso; S. Gama; A. A. Coelho; J. A. Eiras; I. A. Santos

2002-01-01

297

Thermomechanical and optical properties of calcium aluminosilicate glasses doped with Er 3+ and Yb 3+  

Microsoft Academic Search

In this work a series of Er2O3 and Yb2O3 doped and Er2O3Yb2O3 co-doped low silica calcium aluminosilicate glasses have been melted at 1470C under vacuum conditions. Measurements of optical absorption coefficient, mass density, refractive index, Vickers micro-hardness, glass transformation temperature (Tg) and crystallization temperature (Tx) have been carried out. The results showed that these glasses dissolved ?1.5 mol% Er2O3 and

J. A Sampaio; T Catunda; A. A Coelho; S Gama; A. C Bento; L. C. M Miranda; M. L Baesso

2000-01-01

298

One-step synthesis of hydrothermally stable mesoporous aluminosilicates with strong acidity  

SciTech Connect

Using tetraethylorthosilicate (TEOS), polymethylhydrosiloxane (PMHS) and aluminium isopropoxide (AIP) as the reactants, through a one-step nonsurfactant route based on PMHS-TEOS-AIP co-polycondensation, hydrothermally stable mesoporous aluminosilicates with different Si/Al molar ratios were successfully prepared. All samples exclusively showed narrow pore size distribution centered at 3.6 nm. To assess the hydrothermal stability, samples were subjected to 100 deg. C distilled water for 300 h. The boiled mesoporous aluminosilicates have nearly the same N{sub 2} adsorption-desorption isotherms and the same pore size distributions as those newly synthesized ones, indicating excellent hydrothermal stability. The {sup 29}Si MAS NMR spectra confirmed that PMHS and TEOS have jointly condensed and CH{sub 3} groups have been introduced into the materials. The {sup 27}Al MAS NMR spectra indicated that Al atoms have been incorporated in the mesopore frameworks. The NH{sub 3} temperature-programmed desorption showed strong acidity. Due to the existence of large amount of CH{sub 3} groups, the mesoporous aluminosilicates obtained good hydrophobicity. Owing to the relatively large pore and the strong acidity provided by the uniform four-coordinated Al atoms, the excellent catalytic performance for 1,3,5-triisopropylbenzene cracking was acquired easily. The materials may be a profitable complement for the synthesis of solid acid catalysts. - Graphical abstract: Based on the nonsurfactant method, a facile one-step synthesis route has been developed to prepare methyl-modified mesoporous aluminosilicates that possessed hydrothermal stability and strong acidity.

Yang Dongjiang [Chinese Academy of Sciences, State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Taiyuan 030001 (China); School of Physical and Chemical Sciences, Queensland University of Technology, Brisbane, QLD 4001 (Australia); Xu Yao [Chinese Academy of Sciences, State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Taiyuan 030001 (China)], E-mail: xuyao@sxicc.ac.cn; Wu Dong; Sun Yuhan [Chinese Academy of Sciences, State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Taiyuan 030001 (China)

2008-09-15

299

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

Microsoft Academic Search

57Fe Mssbauer spectra of iron bearing alumino-silicate glasses are analysed by two complementary methods (SID and x-VBF) especially\\u000a adapted for the analysis of disordered systems by taking into account distributions of hyperfine Mssbauer parameters. Qualitative\\u000a and quantitative information about the oxidation state of iron are obtained as well as information about the distribution\\u000a of local environments of iron. The possibility

S. Rossano; H. Behrens; M. Wilke

2008-01-01

300

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 46% 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

301

Methylcyclohexane conversion over ZSM-11 zeolite  

Microsoft Academic Search

ZSM-11 zeolite samples differing by their active sites (H+ and Zn2+) have been studied in the conversion of methylcyclohexane. It was observed that both the conversion and the selectivity to aromatic hydrocarbons are increased with the zinc content. It has been shown that dehydrogenation of the hydrocarbon, leading directly to toluene, is the initial stage for Zn-ZSM-11 zeolite showing very

Oscar A. Anunziata; Liliana B. Pierella; Raul G. Marino

1995-01-01

302

Strategies for high throughput, templated zeolite synthesis  

Microsoft Academic Search

The design and redesign of high throughput experiments for zeolite synthesis are addressed. A model that relates materials function to the chemical composition of the zeolite and the structure directing agent is introduced. Using this model, several Monte Carlo-like design protocols are evaluated. Multi-round protocols are bound to be effective, and strategies that use a priori information about the structure-directing

Ligang Chen; Michael W. Deem

2002-01-01

303

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

304

Surface-complex formation between Zn ions and amorphous aluminosilicate in aquatic systems  

SciTech Connect

Surface-complex formation on oxides, especially clay minerals, significantly contributes to determining the composition of river, ground, and soil water. To understand the fate of heavy metals in natural aquatic systems it is important to accumulate information about the surface-complex formation of heavy metals at low concentrations of the solid. Surface-complex formation between synthesized amorphous aluminosilicate and Zn ions has been studied by potentiometry. A batch adsorption experiment was performed at 25 {+-} 0.1 C while the pH value of the suspension was kept at 6.50 and the solid concentration was kept at 0.1 g/liter. The amount of Zn adsorbed on the aluminosilicate and the amount of H{sup +} released from the solid were determined. The observed molar ratio of released H{sup +} to adsorbed Zn was 2 when the total concentration of Zn in the system was relatively high (1.5--13 mmol/liter). This was consistent with the charge balance. However, when the total concentration of Zn in the system was relatively low (0--1.5 mmol/liter), the molar ratio of Zn to H{sup +} was found not to be 2, but near 1. This observation suggests the possibility of surface complex formation between amorphous aluminosilicate and a monovalent Zn complex ion, such as Zn(NO{sub 3}){sup +} and Zn(OH){sup +}.

Miyazaki, Akane; Matsuo, Motoyuki [Univ. of Tokyo (Japan); Tsurumi, Makoto [Hirosaki Univ., Aomori (Japan). Dept. of Earth Science

1996-02-10

305

STUDIES OF POTENTIAL INHIBITORS OF SODIUM ALUMINOSILICATE SCALES IN HIGH-LEVEL WASTE EVAPORATION  

SciTech Connect

The Savannah River Site (SRS) has 49 underground storage tanks used to store High Level Waste (HLW). The tank space in these tanks must be managed to support the continued operation of key facilities. The reduction of the tank volumes in these tanks are accomplished through the use of three atmospheric pressure HLW evaporators. For a decade, evaporation of highly alkaline HLW containing aluminum and silicates has produced sodium aluminosilicate scales causing both operation and criticality hazards in the 2H Evaporator System. Segregation of aluminum-rich wastes from silicate-rich wastes minimizes the amount of scale produced and reduces cleaning expenses, but does not eliminate the scaling nor increases operation flexibility in waste process. Similar issues have affected the aluminum refining industry for many decades. Over the past several years, successful commercial products have been identified to eliminate aluminosilicate fouling in the aluminum industry, but have not been utilized in a nuclear environment. Laboratory quantities of three proprietary aluminosilicate scale inhibitors have been produced and been shown to prevent formation of scales. SRNL has been actively testing these potential inhibitors to examine their radiation stability, radiolytic degradation behaviors, and downstream impacts to determine their viability within the HLW system. One of the tested polymers successfully meets the established criteria for application in the nuclear environment. This paper will describe a summary of the methodology used to prioritize laboratory testing protocols based on potential impacts/risks identified for inhibitor deployment at SRS.

Wilmarth, B; Lawrence Oji, L; Terri Fellinger, T; David Hobbs, D; Nilesh Badheka, N

2008-02-27

306

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

307

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)

2007-05-08

308

Zeolite-based catalysts for hydrocracking  

SciTech Connect

A zeolite/amorphous dual catalyst system was developed which effectively hydrocracked feeds with wide boiling range to extinction. In this dual catalyst system, the zeolite and the amorphous catalysts operate complementally. The good character of zeolite catalyst can be realized without its bad features. Feeds with higher nitrogen content can be hydrocracked, and product yield with good selectivity for naphthas can be obtained. This scheme was derived from diagnosis of the problems associated with zeolite-based hydrocracking catalysts. A zeolitic hydrocracking catalyst, nickel tungsten on rare earth exchanged X-type zeolite (NiW/REX), was found to be ineffective for extinction recycle hydrocracking of feeds containing heavy components. The process performance was poor as indicated by high catalyst aging rate and poor naphtha selectivity and high hydrogen consumption. The polynuclear ring compounds are refractory to NiW/REX due to steric hindrance resulting from the small pore size of the catalyst, but they are easily hydrocracked with high selectivity to naphtha by amorphous catalyst.

Yan, T.Y.

1983-01-01

309

Preparation of an asymmetric zeolite L film  

SciTech Connect

Zeolites and molecular sieves are widely used for catalysis and gas separations. An elusive but highly rewarding goal is the fabrication of zeolite films for selective membranes, electrodes, sensors, and optoelectronic devices. Recently, a variety of techniques tailored to specific applications has emerged (postsynthesis preparations as well as in situ film deposition); however, to date, no general preparative methods exist. Here we report on a new processing scheme which involves the use of zeolite nanosols (colloidal suspensions of zeolite nanoparticles) for film casting, combined with controlled secondary growth of the nanoparticles. Decoupling film deposition from crystal growth provides added flexibility for tailoring the film microstructure and ease for scaleup. Implementation of this scheme, using zeolite L nanosols, led to the preparation of self-supported asymmetric zeolite L films. These films exhibit a regular decrease in crystal grain size and an increase in interzeolitic porosity proceeding from the intergrown surface of the film down into the bulk of the film. In this regard, we refer to these films as asymmetric, using the term as applied in membrane technology. 35 refs., 4 figs.

Lovallo, M.C.; Tsapatsis, M. [Univ. of Massachusetts, Amherst, MA (United States); Okubo, T. [Univ. of Tokyo (Japan)

1996-08-01

310

Kinetics of zeolite dealumination in steam  

SciTech Connect

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

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

1998-08-01

311

Method for the preparation of catalyst composition for use in cracking hydrocarbons  

SciTech Connect

A method is described for preparing a catalyst composition for cracking hydrocarbons, which consists essentially of: spray drying an aqueous slurry containing (i) flash calcined alumina particles which have been prepared by contacting aluminum hydroxide which has been made by the Bayer process, with hot air having a temperature in the range of 350/sup 0/ to 700/sup 0/C., for 5 seconds or less, (ii) kaolin, (iii) a precursor of a siliceous inorganic oxide matrix, and (iv) a crystalline aluminosilicate zeolite, to obtain catalyst particles consisting essentially of from 10 to 30 wt. % of the flash-calcined alumina, from 30 to 55 wt. % of the kaolin, from 3 to 40 wt. % crystalline aluminosilicate zeolite and the balance is the siliceous inorganic oxide matrix. A method is also described in which the zeolite is rare earth exchange zeolite Y or hydrogen exchanged zeolite Y.

Nishimura, Y.; Ogata, M.; Ida, T.

1987-01-13

312

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

313

Comparison absorption of new methylene blue dye in zeolite and nanocrystal zeolite  

Microsoft Academic Search

Mordenite and mordenite nanocrystal, were employed as effective adsorbents for new methylene blue (NMB) from an aqueous solution. The adsorption kinetics was investigated. The adsorption capacity of mordenite nanocrystal zeolite for NMB dye is more than that of the mordenite zeolite. Kinetic and adsorption isotherm studies demonstrate that the adsorption follows the pseudo second-order kinetics. The intraparticle diffusion rate coefficient

Sh. Sohrabnezhad; A. Pourahmad

2010-01-01

314

Crystalline oxides on silicon.  

PubMed

This review outlines developments in the growth of crystalline oxides on the ubiquitous silicon semiconductor platform. The overall goal of this endeavor is the integration of multifunctional complex oxides with advanced semiconductor technology. Oxide epitaxy in materials systems achieved through conventional deposition techniques is described first, followed by a description of the science and technology of using atomic layer-by-layer deposition with molecular beam epitaxy (MBE) to systematically construct the oxide-silicon interface. An interdisciplinary approach involving MBE, advanced real-space structural characterization, and first-principles theory has led to a detailed understanding of the process by which the interface between crystalline oxides and silicon forms, the resulting structure of the interface, and the link between structure and functionality. Potential applications in electronics and photonics are also discussed. PMID:20432223

Reiner, James W; Kolpak, Alexie M; Segal, Yaron; Garrity, Kevin F; Ismail-Beigi, Sohrab; Ahn, Charles H; Walker, Fred J

2010-07-20

315

Crystalline titanate catalyst supports  

DOEpatents

A series of new crystalline titanates (CT) are shown to have considerable potential as catalyst supports. For Pd supported catalyst, the catalytic activity for pyrene hydrogenation was substantially different depending on the type of CT, and one was substantially more active than Pd on hydrous titanium oxide (HTO). For 1-hexene hydrogenation the activities of the new CTs were approximately the same as for the hydrous metal oxide supports.

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

1993-01-01

316

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

317

Fenten chemistry of Fe(III)-exchanged zeolitic minerals treated with antioxidants.  

PubMed

Respirable mineral fibers, such as asbestos, are known to cause pleural mesothelioma, pulmonary fibrosis, and bronchial carcinoma, often years after exposure. Erionite and mordenite, two mineral aluminosilicates (zeolites) with different toxicities, can be used as models to help understand asbestos toxicity. Erionite is carcinogenic, while mordenite is relatively benign. No iron is typically present in erionite or mordenite, but because of their ion-exchange properties they can acquire iron after inhalation. The iron is typically in the Fe(III) form and will need to be reduced prior to any Fenton activity. Lung lining fluid contains antioxidants, such as glutathione (GSH) and ascorbic acid (AA), which can reduce Fe(III) to Fe(II). In this study, we have compared the Fenton reactivity of Fe(III)-exchanged erionite and mordenite after treatment with antioxidants. The Fenton assay involved the reaction of hydroxyl radicals with dimethyl sulfoxide. Fenton reactivity was most marked with AA followed by GSH, and hydrogen peroxide also exhibited minor reactivity. Erionite generated an order of magnitude greater hydroxyl radicals than mordenite, normalized to the surface iron content, providing support for the hypothesis that the iron coordination at the mineral surface plays a significant role in bioactivity. PMID:16173575

Ruda, Toni A; Dutta, Prabir K

2005-08-15

318

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

2011-08-24

319

Photoassisted catalytic oxidation of isopropyl alcohol by uranyl-exchanged zeolites  

SciTech Connect

Suspensions of uranyl-exchanged zeolites mixed with solutions of isopropyl alcohol and acetonitrile undergo selective photocatalytic conversion of the alcohol to acetone. The photoassisted catalytic oxidation is sustained for over 300 h. Bulk photolysis experiments show that aging does occur. X-ray photoelectron spectroscopy experiments indicate the uranyl ions on the surface are slightly reduced with respect to the bulk. Luminescence lifetime measurements yield a range of long-lived components between 10 and 700 ..mu..s for the different zeolites. Quenching experiments show that the shortest lived components of crystalline uranyl-exchanged zeolites are responsible for this conversion to acetone. Liquid nitrogen and liquid helium temperature luminescence emission spectra show splitting of the vibrational rotational fine structure as the temperature is diminished. These splittings are indicative of site symmetry, and in the case of the uranyl-exchanged HZSM-5 with the isopropyl alcohol mixture, evidence is presented that the isopropyl alcohol binds to the excited uranyl ion. The nature of the active site and factors that are important in the mechanism of this reaction are described.

Suib, S.L.

1984-03-21

320

Determination of water content in natural zeolites by reflection method.  

National Technical Information Service (NTIS)

Water content in natural zeolites collected from different site places in Cuba has been determined by neutron reflection method. Results show that it is possible to separate the minerals abundant in zeolite from the surrounding barren rocks. Water content...

L. P. Sarria V. Desdin Garcia V. Freixas Lemus O. Dominguez Ley G. Csikai

1989-01-01

321

Dual zeolite fluid cracking catalyst composition for improved gasoline octane  

SciTech Connect

A fluid cracking catalyst is described useful for the production of high octane gasoline comprising a hydrothermally or chemically stabilized Y zeolite component and a stabilized Omega zeolite component having a silica to alumina ratio greater than 15 wherein the weight ratio of the Y zeolite to the stabilized Omega zeolite is 1:3 to 20: 1, said catalyst not having a hydrogenation component. A fluid cracking catalyst is described according to claim 1, wherein the fluid cracking catalyst comprises either (a) a composite of a Y zeolite and a stabilized Omega zeolite in an inorganic matrix, or (b) a mixture of a matrixed Y zeolite component and a matrixed stabilized Omega zeolite component.

Gatte, R.R.

1993-08-17

322

Catalytic Oxidation by Transition Metal Ions in Zeolites.  

National Technical Information Service (NTIS)

The regular cavities of zeolites form a unique environment for carrying out both stoichiometric and catalytic oxidation reactions. Transition metal ions such as molybdenum and cobalt may be introduced into the zeolite, and, as well, the acidity may be var...

J. H. Lunsford

1988-01-01

323

Experiments on Photochemical Energy Storage with Metal-Coated Zeolites.  

National Technical Information Service (NTIS)

Photo-oxidation of water to oxygen using silver zeolite catalysts resulted in a pH-dependence and inherent sensitivity of the photo-redox system depending on the type of zeolite used. (ERA citation 09:037443)

B. Sulzberger

1983-01-01

324

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

325

Absorption and desorption characteristic of zeolites in gas sensor system  

Microsoft Academic Search

Nanosized zeolites as a novel absorbent were investigated targeting for the nerve agent sarin stimulant gas DMMP. Quartz crystal microbalance (QCM) gas sensors modified with Silicalite-1 or Cu-ZSM-5 zeolites synthesized as micro-porous absorbents were fabricated and their gas response characteristics were examined to study the absorption capability of zeolites. The results indicated that Cu-ZSM-5 zeolite has stronger absorption capacity than

Wei Yao; Yuanyuan Hu; Xinming Ji; Nan Ren; Jia Zhou; Yiping Huang; Yi Tang

2008-01-01

326

Zeolite catalysis in the synthesis of isobutylene from hydrous ethanol  

Microsoft Academic Search

This work deals with the synthesis of isobutylene from a hydrous ethanol feedstock over zeolites. The synthesis is accomplished in three steps: (1) low-temperature direct ethanol conversion to ethylene on H-ZSM-5 zeolite, (2) ethylene conversion to butene products over metal-exchanged zeolites, and (3) butene skeletal rearrangement to isobutylene over FER zeolites. The key to understanding and optimizing each synthesis step

Cory Bernard Phillips

1999-01-01

327

Basic sites in zeolites followed by IR studies of NO +  

Microsoft Academic Search

The basic properties of zeolitic oxygens were examined by IR studies of NO+ ions. NO+ were formed by the disproportionation of N2O4 (N2O4?NO++NO3?). NO+ were stabilized by zeolitic oxygens and NO3? by the zeolitic cations or positively charged extraframework Al species. The spectra of NO+ in zeolite NaY show three maxima that indicate the presence of oxygens of various negative

Barbara Gil; Karolina Mierzy?ska; Monika Szczerbi?ska; Jerzy Datka

2007-01-01

328

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

SciTech Connect

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

Clayden, Nigel J. [School of Chemical Sciences and Pharmacy, University of East Anglia, NR4 7TJ (United Kingdom)]. E-mail: N.Clayden@uea.ac.uk; Esposito, Serena [Laboratorio Materiali del Dipartimento di Meccanica, Strutture, Ambiente e Territorio, Facolta di Ingegneria dell'Universita di Cassino, Via G. Di Biasio 43, 03043 Cassino (FR) (Italy); Ferone, Claudio [Laboratorio Materiali del Dipartimento di Meccanica, Strutture, Ambiente e Territorio, Facolta di Ingegneria dell'Universita di Cassino, Via G. Di Biasio 43, 03043 Cassino (FR) (Italy); Pansini, Michele [Laboratorio Materiali del Dipartimento di Meccanica, Strutture, Ambiente e Territorio, Facolta di Ingegneria dell'Universita di Cassino, Via G. Di Biasio 43, 03043 Cassino (FR) (Italy)

2006-07-15

329

Crystalline oxyfluorinated open-framework compounds: Silicates, metal phosphates, metal fluorides and metal-organic frameworks (MOF)  

Microsoft Academic Search

This contribution is dedicated to a short overview on the utilization of fluorine for the preparation of crystalline microporous frameworks including different families of solids: zeolites, metal phosphates and metal-organic frameworks (MOF-type). Beside the silicates compounds, this presentation is focused on the different types of fluorinated aluminum or gallium phosphates hydrothermally obtained in the presence of organic structure-directing agent or

Thierry Loiseau; Grard Frey

2007-01-01

330

Zeolites as transformation elements in discriminating semiconductor metal oxide sensors  

Microsoft Academic Search

The effectiveness of using zeolites as a method of introducing variance in the gas responses of semiconductor metal oxide gas sensors is demonstrated. Screen printed tungsten trioxide (WO3) and chromium titanium oxide (CTO) thick films overlaid with the hydrogen form of different zeolites were exposed to organic vapours with similar functional groups. The composite metal oxide-zeolite gas sensors responses exhibit

A. Afonja; R. Binions; S. Dungey; I. P. Parkin; D. W. Lewis; D. E. Williams

2010-01-01

331

Computer modeling of the infrared spectra of zeolite catalysts  

Microsoft Academic Search

The paper describes the applications of computer modeling methods to the interpretation of the infrared spectra of zeolite frameworks. The correlation of the breathing vibration of ring structures in zeolitic lattices with their infrared spectra was investigated by the molecular dynamics method. The calculations reveal that in periodic zeolite lattices the ring-breathing vibrations participate in many normal modes. Despite the

Konstantin S. Smirnov; Daniel Bougeard

2001-01-01

332

Nanostructured zeolite 4A molecular sieving air separation membranes.  

PubMed

A novel membrane forming strategy is reported to probe the intrinsic O2/N2 selectivity of zeolite 4A membrane and to fabricate highly selective nanocomposite membranes by using a nanocrystal-derived hierarchical porous zeolite 4A membrane whose non-zeolitic mesoporsity is filled with a nonpermeable polymer material (polyfurfuryl alcohol). PMID:12196960

Wang, Huanting; Huang, Limin; Holmberg, Brett A; Yan, Yushan

2002-08-21

333

Synthesis of ionic liquid templated zeolite like structures  

Microsoft Academic Search

This study describes the utilization of the alkyl substituted imidazolium based ionic liquid as a structure directing agent of the MFI type zeolite structure in water rich environment. The resulted zeolite like structure presents some similarities with the parent MFI structure, but grows preferentially in 1D leading to zeolite like nanofibers.

Amando Martn; Svetlana Ivanova; Francisca Romero Sarria; Miguel ngel Centeno; Jose Antonio Odriozola

2010-01-01

334

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 85C. 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

335

On the exceptional time-on-stream stability of HZSM-12 zeolite: relation between zeolite pore structure and activity  

Microsoft Academic Search

ZSM-12 and several other 12-membered ring large-pore zeolites have been tested for the reforming of naphthenic hydrocarbon\\u000a mixtures. It was found that ZSM-12 possesses a surprisingly higher coking resistance than other large pore zeolites tested\\u000a such as USY, L-zeolite, mordenite, and ?=zeolite for reforming of hydrocarbon mixtures. This superior performance is due to\\u000a the unique non-interconnecting tubular-like linear channels of

Wenmin Zhang; Panagiotis G. Smirniotis

1999-01-01

336

A new active zeolite structure for the selective catalytic reduction (SCR) of nitrogen oxides: ITQ7 zeolite  

Microsoft Academic Search

The activity of a new zeolite material, ITQ7, has been studied for the selective catalytic reduction (SCR) of NO. The pore topology of this material is similar to the structure of a beta zeolite, with a tridirectional system with 12-member rings. ITQ7 exchanged with copper or cobalt shows a catalytic behaviour very similar to a beta zeolite exchanged with copper

Antonio E Palomares; J. G Prato; A Corma

2002-01-01

337

Italian zeolitized rocks of technological interest  

NASA Astrophysics Data System (ADS)

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

de'Gennaro, M.; Langella, A.

1996-09-01

338

Molecular simulation of alkene adsorption in zeolites  

NASA Astrophysics Data System (ADS)

The adsorption isotherms of various alkenes and their mixtures in zeolites such as silicalite-1 (MFI-type), theta-1 (TON-type), and deca-dodecasil 3R (DDR-type) were calculated using the grand canonical Monte Carlo (GCMC) approach. Additionally, the adsorption of alkene-alkane mixtures was simulated. The GCMC approach was combined with the configurational-bias Monte Carlo (CBMC) method. Effective Lennard-Jones parameters for the interaction between the oxygen atoms of all-silica zeolites and the sp2-hybridized groups of linear alkenes were determined using a united atom force field. They were adjusted to the experimental adsorption data of silicalite-1 (MFI). The inflection behaviour of the 1-heptene isotherm was investigated in detail. It is shown that, in the inflection region, the 1-heptene molecules alter their end-to-end length depending on their location. The occurrence of a maximum in the mixture adsorption isotherms is attributed to two effects: entropic effects and non-ideality effects. From the mixture simulations some general conclusions concerning the separation of hydrocarbons with silicalite-1 can be drawn. The transferability of the Lennard-Jones parameters to other zeolites was investigated. Simulations of adsorption isotherms in the zeolites theta-1 and DD3R and their comparison with experimental data indicate the possibility of transferring the parameters to other all-silica zeolites.

Jakobtorweihen, Sven; Hansen, Niels; Keil, Frerich J.

339

Molecular recognition in cation-exchanged zeolites  

NASA Astrophysics Data System (ADS)

The concepts of confinement- and molecular recognition-driven chemical reactivity of cation-exchanged zeolites is illustrated by our recent results from periodic and cluster density functional theory (DFT) calculations. The reactivity of alkali-earth- and alkaline-exchanged low-silica zeolites for selective photo-oxidation of alkenes with molecular oxygen and for N2O4 disproportionation is shown to be mainly due to the specific arrangement and the size of the cations in the zeolite cage. An attempt is made to separate the effects of basicity of the framework, the Lewis acidity of the extra-framework cations and the electrostatic field in the zeolite cage as well as its geometrical properties for the respective reactions. The importance of the favorable adsorption fashion of the reagents controlled by noncovalent interactions with the microporous matrix is shown. The role of the weak interactions with the zeolite walls and the factors, which determine the preference for a particular adsorption mode, are discussed by the example of light alkanes adsorption to Mg- and Ca-exchanged faujasites.

Pidko, Evgeny A.; van Santen, Rutger A.

340

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

341

Calculation of the 13 C NMR shieldings of the C0 2 complexes of aluminosilicates  

NASA Astrophysics Data System (ADS)

13 C NMR shieldings have been calculated using the random-phase-approximation, localized-orbital local-origins version of ab initio coupled Hartree-Fuck perturbation theory for CO 2 and and for several complexes formed by the reaction of CO 2 with molecular models for aluminosilicate glasses, H 3 TOT'H3 3 -n , T,T' = Si,Al. Two isomeric forms of the CO 2 -aluminosilicate complexes have been considered: (1) "CO 2 -like" complexes, in which the CO 2 group is bound through carbon to a bridging oxygen and (2) "CO 3 -like" complexes, in which two oxygens of a central CO 3 group form bridging bonds to the two TH 3 groups. The CO 2 -like isomer of CO 2 -H 3 SiOSiH 3 is quite weakly bonded and its 13 C isotropic NMR shielding is almost identical to that in free CO 2 . As Si is progressively replaced by Al in the --H terminated aluminosilicate model, the CO 2 -like isomers show increasing distortion from the free CO 2 geometry and their 13 C NMR shieldings decrease uniformly. The calculated 13 C shielding value for H 3 AlO(CO 2 )AlH 3 -2 is only about 6 ppm larger than that calculated for point charge stabilized CO 3 -2 . However, for a geometry of H 3 SiO(CO 2 ) AlH 3 -1 , in which the bridging oxygen to C bond length has been artificially increased to that found in the --OH terminated cluster (OH) 3 SiO(CO 2 )Al(OH) 3 -1 , the calculated 13 C shielding is almost identical to that for free CO 2 . The CO 3 -like isomers of the CO 2 -aluminosili-cate complexes show carbonate like geometries and 13 C NMR shieldings about 4-9 ppm larger than those of carbonate for all T,T' pairs. For the Si,Si tetrahedral atom pair the CO 2 -like isomer is more stable energetically, while for the Si,Al and Al,Al cases the CO 3 -like isomer is more stable. Addition of Na + ions to the CO 3 -2 or H 3 AlO(CO 2 )AlH 3 -2 complexes reduces the 13 C NMR shieldings by about 10 ppm. Complexation with either Na + or CO 2 also reduces the 29 Si NMR shieldings of the aluminosilicate models, while the changes in 27 Al shielding with Na + or CO 2 complexation are much smaller. Complexation with CO 2 greatly increases the electric field gradient at the bridging oxygen of H 3 AlOAlH 3 -2 , raising it to a value similar to that found for Si---O---Si linkages. Comparison of these results with the experimental 13 C NMR spectra support the formation of CO 2 -like complexes at SiOSi bridges in albite glasses and CO 3 -like complexes at SiOAl and AlOAl bridges in albite and nepheline glasses. Changes in the calculated shieldings as Na + ions are added to the complexes suggest that some of the observed complexes may be similar in their CO 2 -aluminosilicate interactions, but different with respect to the positions of the charge-compensating Na + ions.

Tossell, J. A.

1995-04-01

342

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

SciTech Connect

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

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

2008-10-28

343

Phenylalanine and arginine adsorption in zeolites X, Y, and Beta.  

PubMed

This paper documents a continuation of work published in Langmuir 2005, 21, 8743-8750. We report new aspects of this amino acid adsorption study, including the effect of changing zeolite framework type and results from adsorption of mixed amino acids. In single-amino-acid adsorption experiments, zeolite Y (Si/Al=2.5) was found to adsorb no phenylalanine while admitting arginine to a similar extent as observed with zeolite beta. Using this zeolite Y, we measured mixed-amino-acid separation selectivities for arginine/phenylalanine as large as 25,000 or 2 orders of magnitude larger than the corresponding selectivities measured with zeolite beta. PMID:17042553

Krohn, John E; Tsapatsis, Michael

2006-10-24

344

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 (30C) and very high yield.

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

2012-01-01

345

(Na{sub 4}BH{sub 4}){sup 3+} guests inside aluminosilicate, gallosilicate and aluminogermanate sodalite host frameworks studied by {sup 1}H, {sup 11}B, and {sup 23}Na MAS NMR spectroscopy  

SciTech Connect

We report tetrahydroborate aluminosilicate, gallosilicate and aluminogermanate sodalites studied by {sup 11}B, {sup 1}H and {sup 23}Na MAS NMR spectroscopy. The spectral parameters are consistent with the local environments of each investigated nucleus obtained from the crystal structures. The {sup 11}B MAS NMR spectra exhibit a sharp narrow line at about -49.0 ppm, which is assigned to BH{sub 4}{sup -} enclathrated into the sodalite framework matrix. The lineshape of the signal shows no quadrupolar interactions due to discreteness and high symmetry of the BH{sub 4}{sup -} unit as well as possible fast dynamic site exchange of hydrogen atoms. The {sup 23}Na MAS NMR signals also show a narrow Gaussian lineshape, which clearly indicates a single type of sodium coordination, and a centrosymmetrical charge distribution around the sodium atom. The {sup 1}H MAS NMR spectra can clearly distinguish between hydrogen in BH{sub 4}{sup -} anions (-0.6 ppm), H{sub 3}O{sub 2}{sup -} anions (1.2 ppm) and H{sub 2}O molecules (5.0 ppm). The structural properties of BH{sub 4}{sup -} intercalation into sodalite framework matrix help connect the microporous materials to hydride-containing A, X and Y type zeolites.

Buhl, J.-Ch. [Institut fuer Mineralogie, Universitaet Hannover, Callinstrasse 3, 30167 Hannover (Germany); Murshed, M.M., E-mail: mmurshe@uni-goettingen.de [Department of Crystallography, Georg-August-University of Goettingen, Goldschmidtstrasse 1, 37077 Goettingen (Germany)

2009-07-01

346

Optical absorption and luminescence study of cobalt-doped magnesium aluminosilicate glass ceramics  

NASA Astrophysics Data System (ADS)

Linear and nonlinear optical properties of cobalt-doped magnesium aluminosilicate transparent glass ceramics that were prepared under different conditions have been studied. It has been shown that absorption and luminescence spectra and absorption bleaching of these glass ceramics are defined mainly by tetrahedrally coordinated Co 2+ ions located in magnesium aluminum spinel nanocrystals. The lifetimes of the 4 T 1 ( 4 F) and 4 T 2 ( 4 F) excited states of the tetrahedral Co 2+ ions were found to be in the ranges 2540 and 120450 ns, respectively, depending on the Co concentration. 2002 Optical Society of America

Malyarevich, A. M.; Denisov, I. A.; Yumashev, K. V.; Dymshits, O. S.; Zhilin, A. A.

2002-08-01

347

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

348

Creep anisotropy of a continuous-fiber-reinforced silicon carbide/calcium aluminosilicate composite  

SciTech Connect

Creep studies conducted on a unidirectional silicon carbide/calcium aluminosilicate composite indicate that the Nicalon fibers provide longitudinal creep strengthening at 1,200 C. The deformation is transient in nature because grain growth in the fibers enhances their creep resistance. The transverse creep strength is considerably smaller, being dominated by the matrix, resulting in appreciable creep anisotropy. This anisotropy leads to severe distortion when off-axis loadings are imposed. Residual stresses develop upon unloading after creep, and cause superficial matrix cracking.

Weber, C.H.; Loefvander, J.P.A.; Evans, A.G. (Univ. of California, Santa Barbara, CA (United States). Materials Dept.)

1994-07-01

349

Water solubility in calcium aluminosilicate glasses investigated by first principles techniques  

Microsoft Academic Search

First-principles techniques have been employed to study the reactivity of water into a calcium aluminosilicate glass. In addition to the well known hydrolysis reactions SiOSi+H2O?SiOH+SiOH and SiOAl+H2O?SiOH+AlOH, a peculiar mechanism is found, leading to the formation of an AlO3H2O entity and the breaking of AlOSi bond. In the glass bulk, most of the hydrolysis reactions are endothermic. Only a few

Frdric Bouyer; Grgory Geneste; Simona Ispas; Walter Kob; Patrick Ganster

2010-01-01

350

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

NASA Astrophysics Data System (ADS)

Chlorine-35 magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra were collected at 14.1 and 18.8 Tesla fields to determine the atomic scale structural environments of the chloride ions in anhydrous and hydrous silicate and aluminosilicate glasses containing 0.2 to 0.7 wt% Cl. NMR peaks are broad and featureless, but are much narrower than the total chemical shift range for the nuclide in inorganic chlorides. Peak widths are primarily due to quadrupole interactions and to a lesser extent to chemical shift distributions. Peak positions are quite different for the Na- and Ca-containing glasses, suggesting that most Cl - coordination environments contain network modifier cations. Comparison of peak positions and shapes for silicate and aluminosilicate glasses containing either Na or Ca suggests that there is no obvious contribution from Cl - bonded to Al, and relative quantitation of peak areas indicates that there is no systematic undercounting of 35Cl spins in the aluminous vs. the Al-free samples. In Ca-Na silicate glasses with varying Ca/(Ca + Na), the mixed-cation glasses have intermediate chemical shifts between those of the end members, implying that there is not a strong preference of either Ca 2+ or of Na + around Cl -. Hydrous Na-aluminosilicate glasses with H 2O contents up to 5.9 wt% show a shift to higher frequency NMR signal with increasing H 2O content, while the quadrupole coupling constant ( CQ) remains constant at 3.3 MHz. However, the change in frequency is much smaller than that expected if H 2O systematically replaced Na + in the first-neighbor coordination shell around Cl -. A series of hydrous Ca-aluminosilicate glasses with H 2O contents up to 5.5 wt% show no shift in NMR signal with increasing H 2O content. The CQ remains constant at 4.4 MHz, again suggesting no direct interaction between Cl - and H 2O in these samples.

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

2004-12-01

351

Long Fluorescence Lifetime of Ti3+-Doped Low Silica Calcium Aluminosilicate Glass  

NASA Astrophysics Data System (ADS)

This Letter reports the formation of Ti3+ in OH- free aluminosilicate glass melted under vacuum condition, with a very long lifetime (170?s) 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.

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.

2008-01-01

352

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

353

Concentration-dependent luminescence of Tb 3+ ions in high calcium aluminosilicate glasses  

Microsoft Academic Search

This study deals with the results on the concentration-dependent fluorescence properties of Tb3+-doped calcium aluminosilicate (CAS) glasses of composition (100?x)(58SiO223CaO5Al2O34MgO10NaF in mol%)-x Tb2O3 (x=0, 0.25, 0.5, 1, 2, 4, 8, 16, 24, 32, 40 in wt%). The FTIR reflectance spectra suggested the role of dopant ions as network modifiers in the glass network. The fluorescence spectra of low Tb3+-doped glasses

Atul D. Sontakke; Kaushik Biswas; K. Annapurna

2009-01-01

354

Non-bridging Oxygens in Calcium Aluminosilicate Glass From Per-calcic to Peraluminous Compositions  

NASA Astrophysics Data System (ADS)

The role of non-bridging oxygen (NBO) and its effects on the thermodynamic and transport properties of aluminosilicate melts are not fully understood, although this species clearly must have a major influence on configurational entropy, viscosity, etc. Its existence along metaluminous joins in alkali- and alkaline-earth aluminosilicates was first postulated from viscosity measurements (Toplis et al., 1996, 2004) and then directly observed in several metaluminous calcium aluminosilicates by 17O nuclear magnetic resonance (NMR) spectroscopy. Much of the recent work has concentrated on glasses with an M+n/(M+nAl) ratio greater than or equal to 0.5 (metaluminous to peralkaline or per-alkaline earth); however, the observed viscosity maxima in several ternary systems occur when this ratio is less than 0.5 (peraluminous). Using NMR spectroscopy, this study investigates the effects of the Ca/Al ratio on the amount of NBO present in calcium aluminosilicate (CAS) glasses. 17O MAS NMR spectra of glasses with 60 mol% SiO2 show a decrease in NBO as the ratio R=Ca+2/(Ca+2Al) decreases, from 6.9% at R=0.56 to 1.0% at R=0.44. Measurable amounts of NBO thus persist well into the peraluminous region of the CAS system, but the species becomes undetectable (<0.5%) when R reaches 0.38 and 0.33. 27Al MAS NMR spectra of these glasses show an increase in the amount of five-coordinated aluminum as compositions become more peraluminous, as is well-known from previous studies (Neuville et al. 2006). Comparison with published viscosity measurements measured at both higher and lower mol % SiO2 (Toplis et al. 2004) suggests that the viscosity maximum does not correspond exactly with the disappearance of NBO from the glasses, but effects of temperature on speciation will need to be taken into account to accurately link glass structure with melt properties: recent work has shown, for example, that NBO content increases with temperature in CaAl2Si2O8 melt (Stebbins et al. 2008).

Thompson, L.; Stebbins, J.

2008-12-01

355

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

PubMed

Among indoor pollutants, ozone is recognised to pose a threat to human health. Recently, low cost natural zeolites have been applied as alternative materials for ozone abatement. In this work, the effect of compensating cation content of natural zeolite on ozone removal is studied. A Chilean natural zeolite is used here as starting material. The amount of compensating cations in the zeolite framework was modified by ion exchange using an ammonium sulphate solution (0.1 mol L(-1)). Characterisation of natural and modified zeolites were performed by X-ray powder diffraction (XRD), nitrogen adsorption at 77K, elemental analysis, X-ray fluorescence (XRF), thermogravimetric analysis coupled with mass spectroscopy (TGA-MS), and temperature-programmed desorption of ammonia (NH(3)-TPD). Ozone adsorption and/or decomposition on natural and modified zeolites were studied by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Results show that the zeolite compensating cation content affects ozone interaction with zeolite active sites. Ammonium ion-exchange treatments followed by thermal out-gassing at 823 K, reduces ozone diffusion resistance inside the zeolite framework, increasing ozone abatement on zeolite surface active sites. Weak and strong Lewis acid sites of zeolite surface are identified here as the main active sites responsible of ozone removal. PMID:22633878

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

2012-05-05

356

Endo- to exo-isomerization of tetrahydrodicyclopentadiene catalyzed by commercially available zeolites  

Microsoft Academic Search

This paper presents the results of catalytic endo- to exo-isomerization of tetrahydrodicyclopentadiene. Several zeolites were tested and influences of calcinations temperatures, Si\\/Al ratio and cations of the zeolites on the reaction were investigated. The results showed that HY zeolites were more active than other zeolites and Y zeolites with other cations, because of its large pore size and relative strong

Enhui Xing; Zhentao Mi; Chengwei Xin; Li Wang; Xiangwen Zhang

2005-01-01

357

Effect of Zeolite Chemical Surface Properties on Catalytic Ozonation of Methylene Blue Contaminated Waters  

Microsoft Academic Search

Heterogeneous catalytic ozonation using natural zeolite has been recently reported. However, there is a lack in the information related to the influence of zeolite active surface sites in this combined system. This work presents experimental results on the effect of zeolite chemical surface properties on catalytic ozonation. Zeolite samples with different chemical surface compositions were prepared from natural zeolite. The

Hctor Valds; Rolando F. Tardn; Claudio A. Zaror

2010-01-01

358

Characterization of ion distributions near the surface of sodium-containing and sodium-depleted calcium aluminosilicate glass melts  

SciTech Connect

The distribution of cation and anion components of sodium containing calcium aluminosilicate glass was studied by classical molecular dynamics simulations in a high temperature melt in the bulk and at the vacuum-melt interface. A significant redistribution of the sodium and non-bridging oxygen ions was observed. Subsequently, a sodium depleted calcium aluminosilicate glass melt was simulated to determine the sensitivity of the redistribution of ions near the vacuum-melt interface to the presence of sodium ions. It is found that the thermodynamic equilibrium condition near a surface favors the enrichment of non-bridging oxygen ions that is closely associated with enrichment of the sodium ions.

Corrales, Louis R.; Du, Jincheng

2006-01-01

359

Metals contamination of aluminosilicate cracking catalysts by Ni- and VO-tetraphenylporphin  

SciTech Connect

The interaction of nickel and vanadyl tetraphenylporphin with amorphous silica-alumina, Y zeolite, and a cracking catalyst containing 15% Y zeolite has been studied with a variety of techniques. For the porphins on the silica-alumina and the cracking catalyst, electronic photoacoustic absorption spectrometry, electron paramagnetic resonance on V, X-ray photoelectron spectroscopy, and plasma desorption mass spectrometry confirm interaction of molecularly dispersed porphin molecules with the support but show no demetallation at temperatures below 120/sup 0/C. Since the large porphin molecules cannot fit into the intracrystalline pore structure of the zeolite, the effective loading of those samples was several monolayers. Spectroscopic measurements showed, and scanning electron microscopy confirmed that the porphins form crystallites in this case. Blockage of a substantial portion of the external surface of the zeolite particles was indicated, however, by a large reduction in the measured intracrystalline pore volume after porphin impregnation. Infrared spectroscopy showed that porphin decomposition during calcination in air begins at 200-300/sup 0/C. On the amorphous silica-alumina-containing materials, the decomposition extends over a 150/sup 0/C range during programmed heating. Metal porphins on the zeolite support showed a sharp, apparently catalytic, exotherm and weight loss at a temperature more than 100/sup 0/C higher than that for the onset of loss of molecular structure. These results show that interactions of metal porphins with cracking catalysts and their individual components are a strong function of coverage and that the decomposition of the porphins can be influenced by that interaction. 63 references.

Roth, S.A.; Iton, L.E.; Fleisch, T.H.; Meyers, B.L.; Marshall, C.L.; Delgass, W.N.

1987-11-01

360

Zeolites as supports for enzymatic hydrolysis reactions. Comparative study of several zeolites  

Microsoft Academic Search

Fusarium solani pisi recombinant cutinase was immobilised by adsorption on different zeolites and its activity towards the hydrolysis reaction of tricaprylin was measured. It was observed that the enzyme immobilised over most of the zeolites used (NaA, NaX, NaY, NaUSY and modified forms) was active for this reaction, although the specific activity depended strongly on the structure and composition of

A. P. V. Gonalves; J. M. Lopes; F. Lemos; F. Rama Ribeiro; D. M. F. Prazeres; J. M. S. Cabral; M. R. Aires-Barros

1996-01-01

361

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

USGS Publications Warehouse

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

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

1986-01-01

362

Fate of Uranium during Sodium Aluminosilicate Formation under Waste Tank Conditions  

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. 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 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. Lastly, analysis of the uranium speciation in a Tank 49H set of samples showed the uranium to be soluble. Analysis of the solution composition and subsequent use of the Hobb's uranium solubility model indicated a uranium solubility limit of 32 mg/L. The measured value of uranium in the Tank 49H matched the model prediction.

Wilmarth, B

2005-06-22

363

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

PubMed

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

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

2005-03-29

364

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

SciTech Connect

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

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

2011-03-23

365

Development of a New Ferrous Aluminosilicate Refractory Material for Investment Casting of Aluminum Alloys  

NASA Astrophysics Data System (ADS)

Investment casting is a time-consuming, labour intensive process, which produces complex, high value-added components for a variety of specialised industries. Current environmental and economic pressures have resulted in a need for the industry to improve current casting quality, reduce manufacturing costs and explore new markets for the process. Alumino-silicate based refractories are commonly used as both filler and stucco materials for ceramic shell production. A new ceramic material, norite, is now being produced based on ferrous aluminosilicate chemistry, having many potential advantages when used for the production of shell molds for casting aluminum alloy. This paper details the results of a direct comparison made between the properties of a ceramic shell system produced with norite refractories and a typical standard refractory shell system commonly used in casting industry. A range of mechanical and physical properties of the systems was measured, and a full-scale industrial casting trial was also carried out. The unique properties of the norite shell system make it a promising alternative for casting aluminum based alloys in the investment foundry.

Yuan, Chen; Jones, Sam; Blackburn, Stuart

2012-12-01

366

Water solubility in calcium aluminosilicate glasses investigated by first principles techniques  

SciTech Connect

First-principles techniques have been employed to study the reactivity of water into a calcium aluminosilicate glass. In addition to the well known hydrolysis reactions Si-O-Si+H{sub 2}O{yields}Si-OH+Si-OH and Si-O-Al+H{sub 2}O{yields}Si-OH+Al-OH, a peculiar mechanism is found, leading to the formation of an AlO{sub 3}-H{sub 2}O entity and the breaking of Al-O-Si bond. In the glass bulk, most of the hydrolysis reactions are endothermic. Only a few regular sites are found reactive (i.e. in association with an exothermic reaction), and in that case, the hydrolysis reaction leads to a decrease of the local disorder in the amorphous vitreous network. Afterwards, we suggest that ionic charge compensators transform into network modifiers when hydrolysis occurs, according to a global process firstly suggested by Burnham in 1975. Our theoretical computations provide a more general model of the first hydrolysis steps that could help to understand experimental data and water speciation in glasses. -- Graphical Abstract: Reactivity within glass bulk: structures obtained after hydrolyses reactions (endothermic and exothermic processes) and mechanisms involving Si-OH, Al-OH, Si-OH-Al groups within aluminosilicates glasses (through ab initio molecular dynamics): formation of the Si-OH-Al entity coupled with an H exchange-Frederic Bouyer and Gregory Geneste. Display Omitted

Bouyer, Frederic, E-mail: frederic.bouyer@cea.f [Laboratoire d'etude du Comportement a Long Terme, Commissariat a l'Energie Atomique et aux Energies Alternatives, Centre de Marcoule, SECM - LCLT, BP 17171, 30207 Bagnols-sur-Ceze Cedex (France); Geneste, Gregory [CEA, DAM, DIF, F-91297 Arpajon (France); Ispas, Simona; Kob, Walter [Laboratoire des Colloides, Verres et Nanomateriaux, UMR CNRS-UM2 5587, Universite Montpellier II, Place Eugene Bataillon, 34095 Montpellier Cedex 5 (France); Ganster, Patrick [Centre SMS, UMR CNRS 5146, Ecole des Mines de Saint-Etienne, 158 cours Fauriel, 42023 Saint-Etienne Cedex 2 (France)

2010-12-15

367

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. Cochem

2002-01-01

368

Zeolite 5A Catalyzed Etherification of Diphenylmethanol  

ERIC Educational Resources Information Center

|An experiment for the synthetic undergraduate laboratory is described in which zeolite 5A catalyzes the room temperature dehydration of diphenylmethanol, (C[subscript 6]H[subscript 5])[subscript 2]CHOH, producing 1,1,1',1'-tetraphenyldimethyl ether, (C[subscript 6]H[subscript 5])[subscript 2]CHOCH(C[subscript 6]H[subscript 5])[subscript 2]. The

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

2009-01-01

369

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

370

Dispersion enhanced metal/zeolite catalysts  

DOEpatents

Dispersion stabilized zeolite supported metal catalysts are provided as bimetallic catalyst combinations. The catalyst metal is in a reduced zero valent form while the dispersion stabilizer metal is in an unreduced ionic form. Representative catalysts are prepared from platinum or nickel as the catalyst metal and iron or chromium dispersion stabilizer.

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

1987-03-31

371

Adsorption of pyridine on dealuminated zeolite HY  

Microsoft Academic Search

Infrared spectra showed that over 80% of aluminum atoms on the surface of zeolite HY were extracted by a exposure of SiCl4 vapor at elevated temperatures. The dealumination of the HY surface resulted in an appreciable change in its acidic properties. Infrared spectra of adsorbed pyridine indicated the formation of various kinds of Lewis acid sites on the delauminated HY

H. Paul Wang

1999-01-01

372

On the templating of curvature in zeolites  

Microsoft Academic Search

The cage and tunnel descriptions of some zeolite crystal structures have previously been shown to be succinctly described as structural networks lying on periodic minimal surfaces, which are saddle-shaped surfaces whose average curvature vanishes everywhere on the surface. The authors establish here that the vanishing average curvature of these structures is due to the templating effect of typical cations (e.g.,

Z. Blum; S. Hyde

2009-01-01

373

Polyphosphonium Salts as Templates for New Zeolites  

Microsoft Academic Search

Zelites have conventionally been prepared using quaternary ammonium salts as templates which control the pore size nnd structure of the resulting material. A range of polyammonium and -phoaphonium salts of the types shown have been prepared for evaluation in directing the formation of new zeolite structiires, particularly those with large pore sizes which may be useful a, ciitalysts for organic

R. Alan Aitken; Vronique Patinec; Paul A. Wright

1999-01-01

374

Zeolite synthesis from pre-treated coal fly ash in presence of soil as a tool for soil remediation  

Microsoft Academic Search

The study reports the synthesis of zeolites from pre-treated coal fly ash in presence of a natural agricultural soil. The synthetic process of zeolites formation in soil was studied for a period of 6 months at 30 and 60 C. The synthesis of zeolite P (zeolite belonging to the Gismondine series) and zeolite X (zeolite belonging to the Faujasite series)

R. Terzano; M. Spagnuolo; L. Medici; F. Tateo; P. Ruggiero

2005-01-01

375

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

PubMed

The benzene methylation with methane over zeolite catalysts was previously shown in our laboratory to require the presence of oxygen. Thus, a two-step mechanism involving the intermediate formation of methanol by partial oxidation of methane followed by the methylation of benzene with methanol in the second step, was postulated. This paper now reports the results of the characterisation of the zeolite catalysts used for the oxidative benzene methylation reaction in order to provide some information about their composition, structure, properties and their behaviour before and after the reaction. The catalysts were characterised by X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray fluorescence (XRF), FT-IR and solid state NMR. XRD results indicate that the crystalline structures of all the ZSM-5 and H-beta catalysts remained unchanged after batch reaction of benzene with methane over the catalysts in agreement with the observation that the catalysts recovered from the reactor could be reused without loss of activity. Elemental analyses and FT-IR data show that as the level of metal ion exchange increases, the Brnsted acid concentration decreases but this metal ion exchange does not totally remove Brnsted acidity. FT-IR results further show that only a small amount of acid sites is actually necessary for a catalyst to be active since used catalysts containing highly reduced Brnsted acidity are found to be reusable without any loss of their activity. 29Si and 27Al magic angle spinning (MAS) NMR together with FT-IR spectra also show that all the active zeolites catalysts contain some extra-framework octahedral aluminium in addition to the normal tetrahedral framework aluminium. The presence of this extra-lattice aluminium does not, however, have any adverse effect on the crystallinity of the catalysts both before and after oxidative benzene methylation reaction. There appears also to be no significant dealumination of the zeolite catalysts during reaction since their catalytic performance was retained after use. PMID:15036089

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

2004-03-01

376

Deactivation Behavior of Bifunctional Pt\\/H-Zeolite Catalysts during Cyclopentane Hydroconversion  

Microsoft Academic Search

Cyclopentane hydroconversion was used as a probe reaction to study the coking behavior of selected large-pore zeolites loaded with 0.5% Pt under identical conditions. The zeolites studied, namely, Y zeolite, zeolite beta, mordenite, LTL, and ZSM-12, were also tested at several different Si\\/Al ratios. The zeolite pore structure was the most important factor determining the deactivation behavior. Zeolites like Y

Srikant Gopal; Panagiotis G. Smirniotis

2002-01-01

377

Synthesis and properties of barium aluminosilicate glassceramic composites reinforced with in situ grown Si 3N 4 whiskers  

Microsoft Academic Search

BAS\\/Si3N4 composites with different barium aluminosilicate (BAS) content have been prepared by hot pressing. The results showed that BAS severed as an effective liquid-phase-sintering aid to attain full densification and promote the ?-Si3N4??-Si3N4 phase transformation. The crystallized BAS significantly benefited the high-temperature mechanical properties of the composites.

Feng Ye; Sheng Chen; Mikio Iwasa

2003-01-01

378

The H{sup +}/Zn{sup 2+} exchange stoichiometry of surface complex formation on synthetic amorphous aluminosilicate  

SciTech Connect

Surface complex formation between synthetic amorphous aluminosilicate and Zn{sup 2+} ion in 0.1 N NaNO{sub 3} was studied at 25 {+-} 0.1 C by potentiometry. The concentration of Zn{sup 2+} in the suspension was varied, while the concentration of the aluminosilicate was kept constant at 1 g air-dried aluminosilicate in 11. The pH value of the suspension was kept constant at 6.50 by 0.01 N NaOH with an automatic titration system to neutralize H{sup +} released from the solid phase. The amount of Zn(II) retained on the solid phase was calculated from the difference between the total Zn{sup 2+} concentration in the suspension and the equilibrated concentration of Zn{sup 2+} in the liquid phase. The molar ratio of Zn(II) retained on the solid surface to H{sup +} released from the solid phase is 1:2, suggesting ion exchange of two surface H{sup +} and one aqueous Zn{sup 2+} ion with conservation of charge balance. The surface complex formation between synthetic amorphous aluminosilicate and Zn{sup 2+} ion in aqueous solution can be described as 2 [Al, Si-OH] + Zn{sup 2+} (aq) = [(Al, Si-O){sub 2}Zn] + 2H{sup +}(aq), where [] represents the chemical species on the solid surface.

Miyazaki, Akane; Tsurumi, Makoto [Tokyo Inst. of Tech., Yokohama (Japan)

1995-06-15

379

Thermo-optical properties of iron-doped low silica calcium aluminosilicate glasses determined by photothermal methods  

Microsoft Academic Search

The aim of this work is to investigate Fe3+ and Fe2+ influence on the thermo-optical properties of low silica calcium aluminosilicate glass. Conventional optical absorption spectroscopy, thermal relaxation calorimetry and thermal lens spectrometry were applied to analyze the samples. The results provided the specific heat, the thermal diffusivity and the optical absorption coefficient as a function of the ions concentration.

R. K. Miura; P. T. Udo; J. H. Rohling; E. A. Falco; A. N. Medina; J. R. D. Pereira; A. C. Bento; M. L. Baesso; S. L. Oliveira; L. A. O. Nunes

2005-01-01

380

Microanalysis of calcium-aluminosilicate glass films grown on α-AlO by pulsed-laser ablation  

Microsoft Academic Search

Pulsed-laser ablation has been used to deposit amorphous calcium- aluminosilicate films on α-AlO single-crystal substrates. The microstructure and composition of each glass film was characterized using analytical electron microscopy. Composition was dependent on substrate temperature during deposition and thickness of the deposited glass layer.

M. P. Mallamaci; C. B. Carter; J. Bentley

1992-01-01

381

Assessment of nonradiative relaxation time and characteristic diffusion time of neodymium, erbium and cobalt doped low silica calcium aluminosilicate glasses  

Microsoft Academic Search

Nonradiative relaxation time (?) and characteristic diffusion time (??) of Nd, Er and Co doped low silica calcium aluminosilicate (LSCA) glasses were assessed by means of photoacoustic spectroscopy. The results are interpreted in terms of frequency dependence predicted by the theory of Rosencwaig and Gersho. Whereas ? varied between 7.2ms and 36ms, the values of ?? lied between 0.25ms and

L. Mota; J. A. Sampaio; M. G. da Silva; H. Vargas

2011-01-01

382

The protective effect of hydrated sodium calcium aluminosilicate against haematological, biochemical and pathological changes induced by Zearalenone in mice  

Microsoft Academic Search

Hydrated sodium calcium aluminosilicate (HSCAS), an anticaking agent for mixed feed, was added alone or simultaneously with a toxic Zearalenone (ZEN) dose to balb\\/c mice and was evaluated for its ability to restore damages induced by ZEN. The latter is a mycotoxin produced by fusarium genera; it is mainly known to induce several toxic effects such as hepatotoxicity, immunotoxicity and

Samir Abbs; Zouhour Ouanes; Jalila ben Salah-Abbs; Zohra Houas; Ridha Oueslati; Hassen Bacha; Omar Othman

2006-01-01

383

X-Ray Emission Spectroscopy Study of Iron Silicate Catalyst FeZSM-5.  

National Technical Information Service (NTIS)

Iron silicate analogs of the zeolite ZMS-5 may be directly synthesized from iron silicate gels in a manner which differs slightly from the alumino-silicate ZSM-5. The resultant white, crystalline iron silicate is referred to as FeZSM-5 in the as-synthesiz...

R. Csencsits C. E. Lyman R. Gronsky

1988-01-01

384

Density of mechanisms within the flexibility window of zeolites.  

PubMed

By treating idealized zeolite frameworks as periodic mechanical trusses, we show that the number of flexible folding mechanisms in zeolite frameworks is strongly peaked at the minimum density end of their flexibility window. 25 of the 197 known zeolite frameworks exhibit an extensive flexibility, where the number of unique mechanisms increases linearly with the volume when long wavelength mechanisms are included. Extensively flexible frameworks therefore have a maximum in configurational entropy, as large crystals, at their lowest density. Most real zeolites do not exhibit extensive flexibility, suggesting that surface and edge mechanisms are important, likely during the nucleation and growth stage. The prevalence of flexibility in real zeolites suggests that, in addition to low framework energy, it is an important criterion when searching large databases of hypothetical zeolites for potentially useful realizable structures. PMID:22107389

Kapko, V; Dawson, C; Rivin, I; Treacy, M M J

2011-10-12

385

Zeolite and swine inoculum effect on poultry manure biomethanation  

NASA Astrophysics Data System (ADS)

Poultry manure is an ammonia-rich substrate that inhibits methanogenesis, causing severe problems to the anaerobic digestion process. In this study, the effect of different natural zeolite concentrations on the mesophilic anaerobic digestion of poultry waste inoculated with well-digested swine manure was investigated. A significant increase in methane production was observed in treatments where zeolite was added, compared to the treatment without zeolite.Methane production in the treatment with 10 g dm-3 of natural zeolite was found to be 109.75% higher compared to the treatment without zeolite addition. The results appear to be influenced by the addition of zeolite, which reduces ammonia toxicity in anaerobic digestion and by the ammonia-tolerant swine inoculum.

Kougias, P. G.; Fotidis, I. A.; Zaganas, I. D.; Kotsopoulos, T. A.; Martzopoulos, G. G.

2013-03-01

386

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

SciTech Connect

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

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

1981-07-01

387

Compositional effects on aluminum and silicon coordination changes in high pressure aluminosilicate glasses: NMR results  

NASA Astrophysics Data System (ADS)

Understanding the structure of high pressure aluminosilicate glasses can better constrain the macroscopic properties and igneous processes in the upper mantle. As melts densify, bond angles and distances change and the average coordination number (CN) for the cations increases. Both Al and Si can increase CN, and are affected by the type and amount of network modifying cation (i.e. Ca, Mg, Na, K, etc...) present. This study uses nuclear magnetic resonance (NMR) spectroscopy to investigate several aspects of the compositional controls on the structure of aluminosilicate glasses quenched from liquids at high pressure. 29Si MAS NMR spectra of 6GPa Na2Si4O9 glasses show the presence of 2 % [5]Si and 2 % [6]Si. A similar glass with 1.2 wt % Al2O3 and the same nominal NBO/T has very similar Si coordinations, even though the Al has an average CN of 5.4. Thus, although Al increases CN more readily than does Si, the addition of Al does not inhibit the formation of high coordination Si. Extending the previously investigated range of modifier cation field strength, 27Al MAS NMR spectra of LaAlSi3O9 glasses show a substantial increase in average Al CN, from about 4.21 to 5.07 from ambient P to 8GPa, while Li3AlSi3O9 glasses have consistently lower average Al CN, increasing from 4.02 to 4.48 from ambient P to 6 GPa. This agrees with previously noted trends with modifier cation field strength. However, at 6 and 8 GPa the average Al CN is less than expected in the La-containing glasses, suggesting that the La3+ environment changes as well. 17O 3QMAS NMR spectra of the Li-containing glasses are consistent with previously proposed mechanisms for the generation of [5],[6]Al at the expense of non-bridging oxygen, but the La-containing glasses have nearly unchanged oxygen environments with increasing pressure. Finally, we present 27Al MAS NMR spectra of Na+Ca-bearing aluminosilicate glasses with up to 5 wt % FeO quenched from melts at 5 GPa and conclude that the substitution of small amounts of Fe2+ for Ca2+ does not significantly affect the average Al CN.

Kelsey, K. E.; Stebbins, J. F.; Asimow, P. D.; Mosenfelder, J. L.

2007-12-01

388

Aluminum coordination and density in high-pressure aluminosilicate glasses: Significance for the structural changes and densification in basaltic magmas  

NASA Astrophysics Data System (ADS)

Densities of aluminosilicate melts are strongly pressure-dependent, owing in part to atomic-scale structural changes. Glasses are commonly used as a first approximation for melts because the structure of a glass is that of the liquid at the glass transition temperature. This study used 27Al MAS NMR to determine the speciation of aluminum ions in glasses quenched from simple basalt-like melts at pressures up to 10 GPa. The spectra establish that high field strength (i.e., Ca) modifier cations induce more high-coordinated Al than lower field strength (i.e., Na and K) cations. The amount of high-coordinated Al gradually increases with increasing synthesis pressure to percentages as high as 81 % for the Ca-aluminosilicate glass at 10 GPa, which yields an average Al-coordination of 5.25. Densities of glasses synthesized at 10 GPa are 8 % (K-aluminosilicate) to 16 % (Ca-aluminosilicate) higher than those quenched at ambient pressure. Additionally, a rapidly decompressed ( 1 second) Ca-aluminosilicate glass (5GPa) was densified by about 14 % relative to the ambient pressure sample, compared to 11 % for the conventionally decompressed 5 GPa glass ( 14 hours). Previous density measurements show that MORB melts at pressures between 5 and 10 GPa are roughly 20 to 30 percent more dense than the ambient pressure melt, which suggests that rapidly decompressed glasses retain much or even most of the total densification and structural changes that occur in the high-pressure melts. The observed increases in Al coordination and density show linear trends, which suggests that this structural change is a major part of the densification mechanism of high-pressure melts. In detail, the data reveal that other changes, such as the compression of modifier cation sites and/or decreased network bond angles, must also contribute to the densification of the melt, especially at low pressure (< 3 GPa).

Allwardt, J. R.; Stebbins, J. F.; Schmidt, B. C.; Frost, D. J.; Withers, A. C.; Hirschmann, M. M.

2004-12-01

389

Reduction of nitrogen oxides with catalytic acid resistant aluminosilicate molecular sieves and ammonia  

Microsoft Academic Search

Noxious nitrogen oxides in a waste gas stream such as the stack gas from a fossil-fuel-fired power generation plant or other industrial plant off-gas stream is catalytically reduced to elemental nitrogen and\\/or innocuous nitrogen oxides employing ammonia as reductant in the presence of a zeolite catalyst in the hydrogen or sodium form having pore openings of about 3 to 10

D. T. Pence; T. R. Thomas

1980-01-01

390

Chemical Interactions in Multimetal/Zeolite Catalysts  

SciTech Connect

This two-year project has led to a significant improvement in the fundamental understanding of the catalytic action of zeolite-supported redox catalysts. It turned out to be essential that we could combine four strategies for the preparation of catalysts containing transition metal (TM) ions in zeolite cavities: (1) ion exchange from aqueous solution; (2) chemical vapor deposition (CVD) of a volatile halide onto a zeolite in its acidic form; (3) solid state ion exchange; and (4) hydrothermal synthesis of a zeolite having TM ions in its lattice, followed by a treatment transporting these ions to ''guest positions''. Technique (2) enables us to position more TM ions into cavities than permitted by the conventional technique (1).viz one positive charge per Al centered tetrahedron in the zeolite lattice. The additional charge is compensated by ligands to the TM ions, for instance in oxo-ions such as (GaO){sup +} or dinuclear [Cu-O-Cu]{sup 2+}. While technique (3) is preferred over CVD where volatile halides are not available, technique (4) leads to rather isolated ''ex lattice'' oxo-ions. Such oxo-ions tend to be mono-nuclear, in contrast to technique (2) which preferentially creates dinuclear oxo-ions of the same TM element. A favorable element for the present research was that the PI is also actively engaged in a project on the reduction of nitrogen oxides, sponsored by EMSI program of the National Science Foundation and the US Department of Energy, Office of Science. This combination created a unique opportunity to test and analyze catalysts for the one step oxidation of benzene to phenol and compare them with catalysts for the reduction of nitrogen oxides, using hydrocarbons as the reductant. In both projects catalysts have been used which contain Fe ions or oxo-ions in the cavities the zeolite MFI, often called ZSM-5. With Fe as the TM-element and MFI as the host zeolite we found that catalysts with high Fe content, prepared by technique (2) were optimal for the De-NO{sub x} reaction, but extremely unselective for benzene oxidation to phenol. Conversely, the catalysts prepared with (4) had the highest turnover frequency for benzene oxidation, but performed very poorly for NO{sub x} reduction with so-butane. In fact the Fe concentration in the former catalysts were so low that it was necessary to design a special experimental program for the sole purpose of showing that it is really the Fe which catalyzes the benzene oxidation, not some acid center as has been proposed by other authors. For this purpose we used hydrogen sulfide to selectively poison the Fe sites, without deactivating the acidic sites. In addition we could show that the hydrothermal treatment of catalysts prepared by technique (4) is essential to transform iron ions in the zeolite lattice to ''ex lattice ions'' in guest positions. That line of the work required very careful experimentation, because a hydrothermal treatment of a zeolite containing Fe ions in its cavities can also lead to agglomeration of such ions to nano-particles of iron oxide which lowers the selectivity for the desired formation of phenol. This part of the program showed convincingly that indeed Fe is responsible for the benzene oxidation catalysis. The results and conclusion of this work, including the comparison of different catalysts, was published in a number of papers in the scientific literature, listed in the attached list. In these papers also our analysis of the reaction orders and the possible mechanism of the used test reaction are given.

Sachtler, Wolfgang M. H.

2004-04-16

391

Behavior and sitting of sodium ion in ZSM-5 zeolite  

Microsoft Academic Search

The behavior of sodium ion in ZSM-5 zeolite was studied by MAS-NMR, ion-exchange, thermal analyses and energy dispersive X-ray analysis (EDX). The samples used were free from surface defects and hence the Na ion in the zeolite was not present in a form of Si-O-Na. In the ion-exchange of the Na ion in the ZSM-5 zeolite with tetramethylammonium (TMA) or

Tatsuo Ohgushi; Toshiyuki Niwa; Hiromi Araki; Satomi Ichino

1997-01-01

392

Separation of water\\/UDMH mixtures using hydroxysodalite zeolite membranes  

Microsoft Academic Search

Dehydration of water\\/1-1-dimethylhydrazine (UDMH) mixtures using hydroxysodalite (HS) zeolite membranes is presented and its performance during separation of water\\/UDMH mixtures was evaluated. HS zeolite was coated on an external surface of porous supports by hydrothermal synthesis. The tubular supports were made of mullite. Water\\/UDMH mixtures were separated at ambient temperature and atmospheric pressure by pervaporation using the HS zeolite membranes.

Mansoor Kazemimoghadam; Toraj Mohammadi

2005-01-01

393

Preparation and characterization of antibacterial zeolite-polyurethane composites  

Microsoft Academic Search

In this study, antibacterial properties were induced in polyurethane (PU) films by the incorporation of Ag-loaded zeolites as fillers. The mechanical and ther- mal properties of the prepared composites were also investigated. For this purpose, two different types of zeo- lite microparticles, high-silica zeolite beta crystals and low-silica zeolite A crystals, were synthesized. Ag was added by ion exchange, and

K. Kamsog; E. A. Aksoy; B. Akata; N. Hasirci; N. Bac

2008-01-01

394

Effects of zeolites on cultures of marine micro-algae  

Microsoft Academic Search

Goal, Scope and BackgroundThe cation-exchange capacity of zeolites is well known and has been increasingly explored in different fields with both economic\\u000a and environmental successes. In aquatic medium with low salinity, zeolites have found multiple applications. However, a review\\u000a of the literature on the applications of zeolites in salt waters found relatively few articles, including some recently published\\u000a papers. The

Adriano Fachini; Maria Teresa S. D. Vasconcelos

2006-01-01

395

Retention of molecular oxygen in zeolites at high temperature  

Microsoft Academic Search

X-ray photoelectron spectroscopy and residual gas analysis experiments were carried out on NaY zeolite at temperatures between -196 and 400°C. The objective of this work was to further understand the 0 1s transition for zeolites since contributions can arise from zeolitic oxygen as well as trapped water. The residual gas analysis data show that molecular oxygen is retained by NaY

S. L. Suib; B. E. Morse

2009-01-01

396

Tetrahedrally coordinated cupric ion in A-zeolites  

Microsoft Academic Search

Electron spin resonance and electron spin echo studies on Cu2+ in four A-zeolites exchanged with K+, Cs+ and NH4+ indicate the formation of a new tetrahedral species, Cu(Oz)3(H2O)2+ where Oz is a zeolite oxygen and the water molecule is probably in the beta cage. The preferential formation of this tetrahedral species in these zeolites instead of the usually observed Cu(H2O)62+

M. Narayana; L. Kevan

1983-01-01

397

Reactivity of trimethyltin manganese pentacarbonyl in zeolite cavities  

Microsoft Academic Search

The anchoring chemistry, thermal stability, and reactivity of MeSnMn(CO) 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. In the NaY host, the precursor is physically adsorbed from hexane solution into the dehydrated zeolite cages at room temperature without further chemical reaction. Symmetry changes of

A. Borvornwattananont; Thomas Bein

1992-01-01

398

Influence of zeolite additive on properties of autoclaved aerated concrete  

Microsoft Academic Search

In this experimental study, the effect of zeolite on the properties of autoclaved aerated concrete (AAC) was investigated. Zeolite was used as a quartzite replacement in conventional AAC mixtures. The zeolite containing AAC (ZAAC) specimens were prepared at bulk densities of 270500kg\\/m3. The specimens were examined by X-ray diffraction, X-ray fluorescence, and thermal analysis. Bulk density, compressive strength and thermal

Mustafa Albayrak; Abdulkerim Yrko?lu; Serdar Karahan; Sema Atl?han; H. Y?lmaz Arunta?; ?smail Girgin

2007-01-01

399

Preparation, characterization and catalytic properties of Pd-Fe-zeolite and Pd-Ce-zeolite composite catalysts.  

PubMed

Highly effective composite catalysts for removal of CO by catalytic oxidation have been designed through constructing active centers on the support of zeolite. Performances of the derived Pd-Fe-zeolite and Pd-Ce-zeolite composite catalysts for CO removal under different heterogeneous conditions were studied. The results indicate that the two kinds of promoted catalysts, including special chemical states of Pd and surface active oxygen, show high catalytic activities not only for the low temperature oxidation of CO, but also for CO electro-oxidation. The typical light-off temperatures of Pd-Fe-zeolite and Pd-Ce-zeolite for low temperature CO oxidation are 270 and 273 K. Their characteristic peak potentials for CO electro-oxidation are both around 0.70 V. The promotional effects are associated with the special interaction among Pd, modifier and zeolite, which can be firmly supported by the detailed characterizations using XRD, BET, XPS, TPD and TPR. PMID:22727393

Bi, Yu-Shui; Dang, Guang-Yao; Zhao, Xiao-Hong; Meng, Xian-Feng; Lu, Hui-Jie; Jin, Jian-Tao

2012-06-06

400

Ion exchange properties of Japanese natural zeolites in seawater.  

PubMed

Ion exchange properties of five different Japanese natural zeolites in seawater were examined. Sodium ions could be reduced by all zeolites, although anions, Cl(-) and SO(4)(2-), in seawater showed barely changes. Natural zeolite desalination treatment mainly depends on the ion exchange between Na(+), K(+) and Mg(2+) in seawater and Ca(2+) in natural zeolite. This study found that mordenite is superior to clinoptilolite for use in Na(+) reduction. Mordenite with high cation exchange capacity containing Ca(2+) resulted in the highest Na(+) reduction from seawater. PMID:23303099

Wajima, Takaaki

2013-01-01

401

Regeneration of zeolite catalysts of isobutane alkylation with butenes  

SciTech Connect

The industrial adoption of alkylation of isoalkanes with alkenes is held back by the rapid and irreversible deactivation of the zeolite catalysts appropriate to the process. This paper is aimed specifically at the restoration of the catalytic activity and increase in the service life of zeolite alkylation catalysts. The catalyst chosen for the investigation was HLaCaNaX zeolite both unmodified and modified with various multivalence cations. The thermochemical and oxidative regeneration process as well as the equipment utilized are described. Both the advantages and the drawbacks of the method are given; explanations for the possibly irreversible losses of the catalytic properties in the regenerated zeolites are also put forward.

Manza, I.A.; Tsupryk, I.N.; Bartyshevskii, V.A.; Gaponenko, O.I.; Petrilyak, K.I.

1986-12-10

402

Influencing the selectivity of zeolite Y for triglycine adsorption.  

PubMed

In prior work we studied the adsorption of triglycine on zeolite Y under reference conditions. This study aims to solve the question of which adsorbent properties and process conditions influence the adsorption triglycine from an aqueous solution by zeolite Y. Relevant zeolite parameters to study are: the amount of acidic sites (Si/Al(2) ratio), counter ion, micropore structure. Process conditions that may influence triglycine adsorption are pH, other components such as sugars, amino acids and salts, and temperature. Adsorption of triglycine on zeolite HY is dominated by ionic interaction. The capacity and selectivity of zeolite HY for triglycine can be changed by choosing different Si/Al(2) ratios or changing the counter ion. The presence of cations and basic anions in solutions reduces triglycine adsorption. Fructose and glycine have no significant influence on triglycine adsorption. Temperature only has a slight influence. The pore structure of zeolite Y is not a critical factor for triglycine adsorption, provided pores are accessible to triglycine and in the micropore range (<2 nm). While this allows other zeolites than zeolite Y to be applied, the presence of the supercage structure of zeolite Y is beneficial to obtain better adsorption of triglycine in its neutral form. PMID:17092513

Wijntje, R; Bosch, H; de Haan, A B; Bussmann, P J T

2006-11-07

403

Dry method for recycling iodine-loaded silver zeolite  

DOEpatents

Fission product iodine is removed from a waste gas stream and stored by passing the gas stream through a bed of silver-exchanged zeolite until the zeolite is loaded with iodine, passing dry hydrogen gas through the bed to remove the iodine and regenerate the bed, and passing the hydrogen stream containing the hydrogen iodide thus formed through a lead-exchanged zeolite which adsorbs the radioactive iodine from the gas stream and permanently storing the lead-exchanged zeolite loaded with radioactive iodine.

Thomas, Thomas R. (Idaho Falls, ID); Staples, Bruce A. (Idaho Falls, ID); Murphy, Llewellyn P. (Idaho Falls, ID)

1978-05-09

404

Synthesis and characterization of ionic liquid-functionalized alumino-silicate MCM-41 hybrid mesoporous materials  

NASA Astrophysics Data System (ADS)

Ionic liquid-functionalized alumino-silicate MCM-41 hybrid mesoporous materials have been synthesized with two-step approach, by means of in situ skeleton doping with aluminium and post surface grafting with N-methylimidazole ionic liquid groups. The samples were characterized by X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), N 2 adsorption-desorption, Fourier transform infrared (FTIR) spectra, 27Al and 13C MAS NMR spectra and temperature-programmed desorption (TPD) of NH 3. The results indicated that the bifunctionalized MCM-41 possessed ordered mesostructure. Aluminium was efficiently introduced into the framework of the mesostructure, generating Lewis and Brnsted acid sites. N-methylimidazole ionic liquid groups were covalently grafted onto the surface of mesoporous materials. The as-synthesized bifunctional MCM-41 showed good catalytic performance in the coupling reaction of CO 2 and propylene oxide.

Cai, Chao; Wang, Hua; Han, Jinyu

2011-09-01

405

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

NASA Astrophysics Data System (ADS)

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

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

2008-04-01

406

Passive Q-switching of erbium glass laser by magnesium aluminosilicate sitall with cobalt ions  

NASA Astrophysics Data System (ADS)

We have studied the radiation output parameters for an erbium glass laser, lasing at a wavelength of 1.54 m, with passive Q-switching by means of a cobalt-containing magnesium aluminosilicate sitall compared with a saturable absorber based on a magnesium aluminum spinel crystal with cobalt ions. We have shown that the output characteristics of the laser emission when using sitall are not inferior to the analogous characteristics of a laser based on a spinel crystal, and are practically independent of the temperature of the saturable absorber in the range 0C 80C. The duration (energy) of the output pulses was 70 nsec (4 mJ), the energy dispersion of the radiation pulse relative to the average value was no greater than 3%, the beam divergence was 2.8 mrad, the laser beam quality factor was M2 = 1.2.

Volk, Yu. V.; Malyarevich, A. M.; Yumashev, K. V.; Dymshits, O. S.; Shashkin, A. V.; Zhilin, A. A.

2007-01-01

407

Surface roughness of yttria-containing aluminosilicate glass-ceramics as indicative of their machinability  

SciTech Connect

Several series of Y[sub 2]O[sub 3]-containing aluminosilicate glasses were prepared by an ordinary melting method, and their physical properties, such as density and Vickers hardness, were measured. Heat treatment of these glasses at 1,200C precipitated tubular and hexagonal Ca[sub 4]Y[sub 4]O(SiO[sub 4])[sub 6] oxyapatite crystals which were characterized by scanning electron microscopy and X-ray diffraction analysis. The homogeneously crystallized glass-ceramics were lathed, and the machinabilities of these samples were estimated by measuring the lathed surface roughness. Then, the relationship between surface roughness and other properties was analyzed to optimize the glass composition. Substitution of BaO for CaO was conducted and the physical properties were examined.

Morita, Kazuki; Umezawa, Akira; Yamato, Shinji; Makishima, Akio (Univ. of Tokyo, Tokyo (Japan). Dept. of Materials Science)

1993-07-01

408

Sodium sulfate hot corrosion of silicon carbide fiber-reinforced calcium aluminosilicate. Master`s thesis  

SciTech Connect

The effects of sodium sulfate hot corrosion on the microstructure of silicon carbide fiber-reinforced calcium aluminosilicate glass-ceramic matrix composite were investigated using optical microscopy, scanning electron microscopy (SEM) and x-ray diffraction (XRD). Hot corrosion of samples at 900 deg C for 50 hours in both air and argon was investigated. SEM and XRD investigations of the sample exposed in air revealed a complex mixture of wollastonite, nepheline and albite whereas exposure in argon showed pseudowollastonite, nepheline and calcium sulfide. It was observed that the presence of Na2SO4 enhanced the oxidation of the silicon carbide fiber to silica which further reacted to form the products of corrosion.

Oppici, M.A.

1995-03-01

409

Micro-Raman and EPR studies of /?-radiation damages in aluminosilicate glass  

NASA Astrophysics Data System (ADS)

Structural changes under /?-irradiation have been investigated by means of micro-Raman and electron paramagnetic resonance (EPR) spectroscopies on a calcium aluminosilicate glass with the composition 48.22 SiO2, 12.64 Al2O3, 2.48 Na2O, 3.45 Cs2O, 0.46 Rb2O, 32.75 CaO. The Raman spectra of this sample show no significant structural changes up to 4109 Gy. This result could be correlated to the fact that alkaline and alkaline earth migration under /?-irradiation are reduced for this glass composition because these ions are trapped close to aluminium ions for charge compensating reasons. EPR spectra of these irradiated glasses indicate the creation of three paramagnetic centres (Al-OHC, Oxy and E' defects) which increase with dose.

Chah, K.; Boizot, B.; Reynard, B.; Ghaleb, D.; Petite, G.

2002-05-01

410

Fictive temperature-independent density and minimum indentation size effect in calcium aluminosilicate glass  

SciTech Connect

Using the calcium aluminosilicate system a glass was developed that exhibits fictive temperature-independent density by creating an intermediate glass between normal and anomalous glasses. Normal glass, such as soda-lime silicate glass, exhibits decreasing density with increasing fictive temperature while anomalous glass, such as silica glass, exhibits increasing density with increasing fictive temperature. This intermediate glass composition was found to exhibit the minimum indentation size effect during indentation hardness testing. It appears that the indentation size effect is correlated with a deformation-induced fictive temperature increase, which is accompanied by a density change and hardness change in the vicinity of the indentation. It is suggested from these observations that indentation size effect originates from the energy required to create interfaces and defects such as shear bands, subsurface cracks, and point defects near the indenter-specimen boundary, which accompany the volume change.

Gross, T. M.; Tomozawa, M. [Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180-3593 (United States)

2008-09-15

411

The elevated temperature compression creep behavior of a calcium-aluminosilicate(anorthite) glass ceramic  

SciTech Connect

An experimental investigation of compression creep in a calcium-aluminosilicate glass ceramic revealed that the deformation can be expressed as [epsilon][alpha][sigma][sup 1]exp([minus]650 kJ mol[sup [minus]1]/RT), where [epsilon] is the steady state strain rate, [sigma] is the imposed stress, R is the gas constant and T is the absolute temperature. The high activation energy, a stress exponent of unity and microstructural observations indicate that creep deformation is enhanced by the presence of a liquid phase. The occurrence of significant cavitation at low strains suggests that the material is not likely to exhibit superplastic-like large elongations when tested in tension, although it exhibits Newtonian-viscous behavior.

Mercer, R.F.; Chokski, A.H. (Univ. of California, San Diego (United States))

1993-05-15

412

Fictive temperature-independent density and minimum indentation size effect in calcium aluminosilicate glass  

NASA Astrophysics Data System (ADS)

Using the calcium aluminosilicate system a glass was developed that exhibits fictive temperature-independent density by creating an intermediate glass between normal and anomalous glasses. Normal glass, such as soda-lime silicate glass, exhibits decreasing density with increasing fictive temperature while anomalous glass, such as silica glass, exhibits increasing density with increasing fictive temperature. This intermediate glass composition was found to exhibit the minimum indentation size effect during indentation hardness testing. It appears that the indentation size effect is correlated with a deformation-induced fictive temperature increase, which is accompanied by a density change and hardness change in the vicinity of the indentation. It is suggested from these observations that indentation size effect originates from the energy required to create interfaces and defects such as shear bands, subsurface cracks, and point defects near the indenter-specimen boundary, which accompany the volume change.

Gross, T. M.; Tomozawa, M.

2008-09-01

413

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

SciTech Connect

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

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

1998-09-01

414

Structural and dynamic properties of calcium aluminosilicate melts: A molecular dynamics study  

NASA Astrophysics Data System (ADS)

The structural and dynamic properties of calcium aluminosilicate (CaO-Al2O3)1-x(SiO2)x melts with low silica content, namely, along the concentration ratio R = 1 are studied by classical molecular dynamics. An empirical potential has been developed here on the basis of our previous ab initio molecular dynamics. The new potential gives a description of the structural as well as the dynamics with a good accuracy. The self-intermediate scattering function and associated ?-relaxation times are analyzed within the mode-coupling theory. Our results indicate a decrease of the fragility whose structural origin is a reduction of the number of fivefold coordinated Al atoms and non-bridging oxygen.

Bouhadja, M.; Jakse, N.; Pasturel, A.

2013-06-01

415

Aluminum speciation, vibrational entropy and short-range order in calcium aluminosilicate glasses  

NASA Astrophysics Data System (ADS)

The heat capacity and vibrational entropy of a calcium aluminate and three peraluminous calcium aluminosilicate glasses have been determined from 2 to 300 K by heat-pulse relaxation calorimetry. Together with previous adiabatic data for six other glasses in the system CaO-Al 2O 3-SiO 2, these results have been used to determine partial molar heat capacities and entropies for five species namely, SiO 2, CaO and three different sorts of Al 2O 3 in which Al is 4-, 5- and 6-fold coordinated by oxygen. Given the determining role of oxygen coordination on low-temperature heat capacity, the composition independent entropies found for SiO 2 and CaO indicate that short-range order around Si and Ca is not sensitive to aluminum speciation up to the highest fraction of 25% observed for VAl by NMR spectroscopy. Because of the higher room-temperature vibrational entropy of IVAl 2O 3 (72.8 J/mol K) compared to VAl 2O 3 (48.5 J/mol K), temperature-induced changes from IVAl to VAl give rise to a small negative contribution of the order of 1 J/mol K to the partial molar configurational heat capacity of Al 2O 3 in melts. Near 0 K, pure SiO 2 glass distinguishes itself by the importance of the calorimetric boson peak. On a g atom basis, the maximum of this peak varies with the composition of calcium aluminosilicate glasses by a factor of about 2. It does not show smooth variations, however, either as a function of SiO 2 content, at constant CaO/Al 2O 3 ratio, or as a function of Al 2O 3 content, at constant SiO 2 content.

Richet, Pascal; Nidaira, Atsusi; Neuville, Daniel R.; Atake, Tooru

2009-07-01

416

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

SciTech Connect

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

Rodewald, P.G.

1993-06-15

417

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

418

Zeolitic catalyst with improved regeneration properties  

Microsoft Academic Search

An experimental batch of Tseokar-4 bead catalyst was prepared from the zeolitic catalyst Tseokar-2 by adding 0.15% chromic oxide by weight. Finds that the use of the Tseokar-4 (with better regeneration properties because of the addition of chromium), in a commercial unit made it possible to increase the coke burnoff rate in the regenerator quite substantially, particularly in the upper

V. R. Zinovev; L. V. Bryzgalina; S. N. Khadzhiev; A. P. Kosolapova

1983-01-01

419

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

420

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

SciTech Connect

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

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

2010-02-15

421

Monoethanol amine modified zeolite 13X for CO{sub 2} adsorption at different temperatures  

SciTech Connect

Zeolite 13X has been modified with monoethanol amine (MEA). MEA loadings of 0.5-25 wt % have been achieved using the impregnation method in different solvents. The mode of incorporation based on methanol with stirring at room temperature appears to be the most feasible. The adsorbent has been characterized for crystallinity, surface area, pore volume, and pore size. The thermal stability of the adsorbent is studied using a thermal analyzer. The CO{sub 2} adsorption capacity of adsorbents is evaluated using the breakthrough adsorption method with a packed column on a 10 g scale. The adsorption capacities of adsorbents are estimated in the temperature range 30-120{sup o}C. The adsorbents show improvement in CO{sub 2} adsorption capacity over the unmodified zeolite by a factor of ca. 1.6 at 30{sup o}C, whereas at 120{sup o}C the efficiency improved by a factor of 3.5. For adsorption at these temperatures, different MEA loading levels were found to be suitable as per the governing adsorption phenomena, that is, physical or chemical. The adsorbent is also studied for CO{sub 2} selectivity over N{sub 2} at 75{sup o}C. The MEA-modified adsorbent shows better CO{sub 2} selectivity, which was improved further in the presence of moisture. 25 refs., 6 figs., 3t abs.

P.D. Jadhav; R.V. Chatti; R.B. Biniwale; N.K. Labhsetwar; S. Devotta; S.S. Rayalu [National Environmental Engineering Research Institute, Nagpur (India)]. s_rayalu@neeri.res.in

2007-12-15

422

Zeolite compositions as proxies for eruptive paleoenvironment  

NASA Astrophysics Data System (ADS)

We report chemical compositions of authigenic alteration minerals in subglacially erupted hyaloclastite breccias from James Ross Island, Antarctica, which provide a geochemical proxy for paleoenvironment. Analyses of zeolites (phillipsite and chabazite) from several lava-fed deltas on the island were compared with published compositions of zeolites from known freshwater and marine environments. Using values of (Na + K)/Ca = 3.0 (for phillipsites) and 1.0 (for chabazites), the data successfully distinguish between marine and freshwater alteration. However, our study also suggests that volcanic breccias may not be sealed to fluids, even when the pore spaces are completely filled. The James Ross Island data show that, at higher elevations in lava-fed deltas, the zeolites preserve their original freshwater-influenced (i.e., glacial) compositions, whereas at lower elevations, (Na + K)/Ca ratios are generally higher and indicate a later marine influence. We suggest that water may penetrate several kilometers into the volcanic pile by movement along fractures and/or grain boundaries.

Johnson, Joanne S.; Smellie, John L.

2007-03-01

423

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

424

Solar energy storage by natural zeolites: I. Dehydration of zeolitic tuff  

SciTech Connect

In the perspective of a possible utilization of natural zeolites in the solar energy exploitation as materials suitable for heat storage, the behaviours of chabazitic and phillipsitic tuffs in the isothermal dehydration have been studied, evaluating the influence of temperature, heating rate and cationic form of the zeolite on the water desorption process. The possibility of achieving an almost complete desorption at temperatures of 200/250/sup 0/C in times of the order of two hours or less has been emphasized and indications on the heat amount storable by a chabazitic tuff in its original cationic form have been at last given.

Nastro, A.; Aiello, R.; Colella, C.; Conte, M.; Fittipaldi, F.

1980-12-01

425

Process wastewater treatment with hydrogen-form CST and chabazite zeolite  

SciTech Connect

Ion-exchange materials have been investigated for the removal of radionuclides from near-neutral-pH wastewaters containing competing cations at concentrations greater than those of the targeted species. Natural chabazite zeolite was chosen as the baseline material for the removal of fission products, namely {sup 90}Sr and {sup 137}Cs, from wastewater and groundwater. The sorbent IONSIV{reg_sign} IE-911, a crystalline silicotitanate manufactured by UOP, was recently tested in this capacity and found to compare extremely well against the baseline material in removing {sup 90}Sr and {sup 137}Cs from process wastewater. This paper presents results of similar column tests performed using both materials, as well as results from batch experiments on actual wastewaters using IONSIV{reg_sign} IE-911.

DePaoli, S.M.; Bostick, D.T.

1998-05-01

426

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

National Technical Information Service (NTIS)

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

M. G. Howden

1981-01-01

427

Influence of zeolites in PDMS membranes. Pervaporation of water\\/alcohol mixtures  

Microsoft Academic Search

A strong influence of the zeolite was found on the pervaporation of alcohol\\/water mixtures using filled PDMS membranes. In all cases, the zeolites reduced the swelling of the PDMS. Incorporation of the hydrophilic zeolite Y increased water fluxes, while ZSM-5 reduced both water and alcohol fluxes due to a partial retention of these molecules in the zeolite. For branched alcohols,

Ivo F. J. Vankelecom; Dirk Depre; Stijn De Beukelaer; Jan B. Uytterhoeven

1995-01-01

428

Influence of Chemical Surface Characteristics of Natural Zeolite on Catalytic Ozone Abatement  

Microsoft Academic Search

In this article, the effect of zeolite chemical surface properties on gaseous ozone removal was investigated. Zeolite samples with different surface chemical composition were prepared from a Chilean natural zeolite. Such treatments included acid de-alumination, and thermal treatment at 400 C and 550 C prior to contact with ozone. Chemical modification of natural zeolite showed that the generation of new

Hctor Valds; Eder E. Padilla; Claudio A. Zaror

2011-01-01

429

Removal of Ca and Zn from aqueous solutions by zeolites NaP and KP  

Microsoft Academic Search

Zeolites P in sodium (NaP) and potassium (KP) forms were used as adsorbents for the removal of calcium (Ca) and zinc (Zn) cations from aqueous solutions. Zeolite KP was prepared by ion exchange of K with Na which neutralizes the negative charge of the zeolite P framework structure. The ion exchange capacity of K on zeolite NaP was determined through

Alias Mohd Yusof; Nik Ahmad Nizam Nik Malek; Nurul Asyikin Kamaruzaman; Muhammad Adil

2010-01-01

430

Separation of 1-butanol\\/2,3-butanediol using ZSM-5 zeolite-filled polydimethylsiloxane membranes  

Microsoft Academic Search

Mixed matrix membranes were prepared by incorporating ZSM-5 zeolite particles into polydimethylsiloxane. A uniform dispersion of the zeolite in the membrane was obtained. The membranes were characterized with scanning electron microscopy, and the effects of zeolite loading on membrane performance were evaluated. It was found that 80wt.% ZSM-5 loading was optimal for selectivity. Further increase in the zeolite loading either

Pinghai Shao; Ashwani Kumar

2009-01-01

431

Diverse topics in crystalline beams  

SciTech Connect

Equations of motion are presented, appropriate to interacting charged particles of diverse charge and mass, subject to the external forces produced by various kinds of magnetic fields and radio-frequency (rf) electric fields in storage rings. These equations are employed in the molecular dynamics simulations to study the properties of crystalline beams. The two necessary conditions for the formation and maintenance of crystalline beams are summarized. The transition from ID to 2D, and from 2D to 3D is explored, and the scaling behavior of the heating rates is discussed especially in the high temperature limit. The effectiveness of various cooling techniques in achieving crystalline states has been investigated. Crystalline beams made of two different species of ions via sympathetic cooling are presented, as well as circulating ``crystal balls`` bunched in all directions by magnetic focusing and rf field. By numerically reconstructing the original experimental conditions of the NAP-M ring, it is found that only at extremely low beam intensities, outside of the range of the original measurement, proton particles can form occasionally-passing disks. The proposed New ASTRID ring is shown to be suitable for the formation and maintenance of crystalline beams of all dimensions.

Wei, Jie [Brookhaven National Lab., Upton, NY (United States); Draeseke, A.; Sessler, A.M. [Lawrence Berkeley Lab., CA (United States); Li, Xiao-Ping [BIOSYM Technologies Inc., San Diego, CA (United States)

1995-11-27

432

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

PubMed

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

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

2009-07-01

433

Synthesis of zeolites from coal fly ash: an overview  

Microsoft Academic Search

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

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

2002-01-01

434

Support effects on CO hydrogenation over Ru/zeolite catalysts  

SciTech Connect

Hydrogenation of carbon monoxide at 101.3 kPa has been studied over a series of ion-exchanged Ru catalysts supported on NaX, NaY, KL, Na mordenite, and HY zeolites. The type of zeolite had pronounced effects on the activity and selectivity of the Ru. The specific activity would appear to be related to the dispersion of reduced ruthenium in the zeolite. Methane selectivity, however, seems to be strongly influenced by the type and concentration of alkali cations remaining in the ion-exchanged zeolite. These cations appear to promote chain growth much as traditional alkali promoters would, though perhaps more indirectly. Due to bifunctional properties of the zeolite-supported catalysts, a significant fraction of C/sub 4/ was in the form of isobutane. Formation of isobutane seems to be related to either the Si/Al ratio in the zeolites or the concentration of the remaining alkali cations, but not to the OH concentration. In addition, H/sub 2/ chemisorption at 25/sup 0/C was increasingly suppressed as the Se/Al ratio of the zeolite support increased. Both the formation of isobutane and the suppression of H/sub 2/ chemisorption may be related to the acid strength of the OH groups present, which is a function of the Si/Al ratio of the zeolite.

Chen, Y.W.; Wang, H.T.; Goodwin, J.G. Jr.

1984-02-01

435

Ion exchange in a zeolite-molten chloride system  

SciTech Connect

Electrometallurgical treatment of spent nuclear fuel results in a secondary waste stream of radioactive fission products dissolved in chloride salt. Disposal plans include a waste form that can incorporate chloride forms featuring one or more zeolites consolidated with sintered glass. A candidate method for incorporating fission products in the zeolites is passing the contaminated salt over a zeolite column for ion exchange. To date, the molten chloride ion-exchange properties of four zeolites have been investigated for this process: zeolite A, IE95{reg_sign}, clinoptilolite, and mordenite. Of these, zeolite A has been the most promising. Treating zeolite 4A, the sodium form of zeolite A , with the solvent salt for the waste stream-lithium-potassium chloride of eutectic melting composition, is expected to provide a material with favorable ion-exchange properties for the treatment of the waste salt. The authors constructed a pilot-plant system for the ion-exchange column. Initial results indicate that there is a direct relationship between the two operating variable of interest, temperature, and initial sodium concentration. Also, the mass ratio has been about 3--5 to bring the sodium concentration of the effluent below 1 mol%.

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

1997-07-01

436

The adsorption of SO by zeolites synthesized from fly ash  

Microsoft Academic Search

Zeolites X, Y, and Na-Pl (90 C) and analcime and sodalite (150 C) were synthesized from Class F fly ash using 3 M sodium hydroxide solutions and autogenous pressures. The partially zeolitized fly ashes were dried overnight in air at room temperature and then characterized using X-ray diffraction and SEM. On occasion, a few samples were dried to constant weight

Anand Srinivasan; Michael W. Grutzeck

1999-01-01

437

Zeolitic coatings and their potential use in catalysis  

Microsoft Academic Search

The formation of zeolitic coatings and their properties, such as the thickness, continuity and orientation of the crystals, are related to the presence and macro-organization of a precursor phase. Based on this view, preshaped zeolitic coatings can be prepared which may be either active catalysts themselves or an inert thin membrane on an existing catalyst. They can be applied in

J. C. Jansen; J. H. Koegler; H. van Bekkum; H. P. A. Calis; C. M. van den Bleek; F. Kapteijn; J. A. Moulijn; E. R. Geus; N. van der Puil

1998-01-01

438

Investigation of zeolites by solid state quadrapole NMR.  

National Technical Information Service (NTIS)

The subject of this thesis is the NMR investigation of zeolites. The nature and properties of zeolites are discussed. Some of the basic priniples of NMR techniques on quadrupole nuclei are presented. A special technique, namely a two-dimensional nutation ...

R. Janssen

1990-01-01

439

Removal of ammonium from greywater using natural zeolite  

Microsoft Academic Search

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

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

2011-01-01

440

Preparation and characterization of ton type zeolite catalysts  

Microsoft Academic Search

The reduction of air pollutants emitted at the engine exhaust is an imperative goal for the coming years. The traditional Pt-Rh three-way catalysts are not able to operate in lean burn condition working engines. Copper and cobalt zeolites show high activity and selectivity for both reduction of NOx and hydrocarbon combustion. The TON type zeolite presents a high hydrophobicity and

F. Cosentino; A. Katovic; G Giordano; P. Lentz; J. B. Nagy

1999-01-01

441

Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen  

DOEpatents

A process is described for selective thermal oxidation or photooxidation of hydrocarbons adsorbed onto zeolite matrices. A highly selective thermal oxidation and photooxidation of unsubstituted or alkyl substituted alkanes, alkenes, aromatics and cycloalkyls in solvent free zeolites under dark thermal conditions or under irradiation with visible light. The process oxidizes hydrocarbons almost completely selectively without substantial production of byproducts. 19 figs.

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

1999-06-22

442

Co-ZSM-5 Zeolites: Characterization and Magnetic Properties  

Microsoft Academic Search

ZSM-5 zeolites modified with Co cations were synthesized. They were characterized by AA, XRD, Raman Spectroscopy, TPR, FTIR and BET. The Co ions were introduced in the zeolitic matrix by wet impregnation or ion-exchange methods, followed by thermal treatments. The incorporation of cobalt ions into ZSM-5 does not affect the high degree of purity, cristallinity and orthorhombic symmetry of the

L. B. Pierella; M. Fernndez Garca; P. Bercoff; H. R. Bertorello

443

Adsorption of Pb and Cd by amine-modified zeolite  

Microsoft Academic Search

Natural zeolites, known for their excellent sorption properties towards metal cations, are widely used for the purification of wastewaters. The selectivity of clinoptilolite, a common zeolite mineral, for Pb is known to be particularly high, whereas its selectivity for Cd is often lower. Extraordinarily high sorption capacities for soft metal cations were observed in the case of thiol-functionalized silica gels

Ulla Wingenfelder; Bernd Nowack; Gerhard Furrer; Rainer Schulin

2005-01-01

444

Antibacterial activity of heavy metal-loaded natural zeolite.  

PubMed

The antibacterial activity of natural zeolitized tuffs containing 2.60wt.% Cu(2+), 1.47 Zn(2+) or 0.52 Ni(2+) were tested. Antibacterial activities of the zeolites against Escherichia coli and Staphylococcus aureus were tested after 1h and 24h of exposure to 1g of the zeolite in 100mL of three different media, namely Luria Bertani, synthetic wastewater and secondary effluent wastewater. The antibacterial activities of the zeolites in Luria Bertani medium were significantly lower than those in the other media and negatively correlated with the chemical oxygen demand of the media. The Ni-loaded zeolite showed high leaching of Ni(2+) (3.44-9.13wt.% of the Ni(2+) loaded) and weak antibacterial activity in the effluent water. Since Cu-loaded zeolite did not leach Cu(2+) and the leaching of Zn(2+) from Zn-loaded zeolite was low (1.07-1.61wt.% of the Zn(2+) loaded), the strong antibacterial activity classified the Cu- and Zn-loaded zeolite as promising antibacterial materials for disinfection of secondary effluent water. PMID:22178285

Hrenovic, Jasna; Milenkovic, Jelena; Ivankovic, Tomislav; Rajic, Nevenka

2011-12-01

445

Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen  

Microsoft Academic Search

A process is described for selective thermal oxidation or photooxidation of hydrocarbons adsorbed onto zeolite matrices. A highly selective thermal oxidation and photooxidation of unsubstituted or alkyl substituted alkanes, alkenes, aromatics and cycloalkyls in solvent free zeolites under dark thermal conditions or under irradiation with visible light. The process oxidizes hydrocarbons almost completely selectively without substantial production of byproducts. 19

H. Frei; F. Blatter; H. Sun

1999-01-01

446

CHARACTERISTICS OF ZEOLITE WASHCOATS ON CORDIERITE MONOLITHS FOR ENVIRONMENTAL APPLICATIONS  

Microsoft Academic Search

Several preparation variables were analyzed which might affect the characteristics of zeolite coatings on cordierite monolith structures obtained by was hcoating. It was found that zeolite type, suspension concentration, number of immersions, solvent, particle size, and additives impinge on coating quality. When the suspension concentration is increased, a non-linear increment of the load is obtained. At the same time, the

J. M. Zamaro; M. A. Ulla; E. E. Mir

447

Exploratory study of mesopore templating with carbon during zeolite synthesis  

Microsoft Academic Search

Here we present an exploratory study on the generation of mesopores in zeolite crystals by templating with carbon during synthesis. With nitrogen physisorption, scanning electron microscopy and (three-dimensional) transmission electron microscopy we have studied the influence of the carbon source and zeolite synthesis conditions on the mesopores generated after the carbon has been burned off. In particular, silicalite-1 crystals have

A. H. Janssen; I. Schmidt; C. J. H. Jacobsen; A. J. Koster; K. P. de Jong

2003-01-01

448

Raman studies of the templated synthesis of zeolites  

Microsoft Academic Search

The application of confocal Raman and FT-Raman in the understanding of zeolite synthesis is a goal that can be reached by studying different levels of complexity. First, the Raman properties of TEOS and its polymerization products under acid conditions is investigated. Structural characterization of zeolite framework vibrations is related to their building blocks such as prisms and sodalite cages. The

P. P. H. J. M. Knops-Gerrits; M. G. L. J. Cuypers

2000-01-01

449

Structure descriptors for organic templates employed in zeolite synthesis  

Microsoft Academic Search

A structural analysis has been carried out upon 130 organic templating agents employed in the synthesis of zeolites from 18 different framework types. The orthogonal principal axes of inertia of these molecules provide quantitative structure descriptors which can be plotted to produce three-dimensional shape-space diagrams. Groups of templates which produce different zeolite framework architectures plot in discrete areas of these

R. E. Boyett; A. P. Stevens; M. G. Ford; P. A. Cox

1997-01-01

450

Preparation of a Versatile Bifunctional Zeolite for Targeted Imaging Applications  

PubMed Central

Bifunctional zeolite Y was prepared for use in targeted in vivo molecular imaging applications. The strategy involved functionalization of the external surface of zeolite Y with chloropropyltriethoxysilane followed by reaction with sodium azide to form azide-functionalized NaY, which is amenable to copper(1) catalyzed click chemistry. In this study, a model alkyne (4-pentyn-1-ol) was attached to the azide-terminated surface via click chemistry to demonstrate feasibility for attachment of molecular targeting vectors (e.g., peptides, aptamers) to the zeolite surface. The modified particle efficiently incorporates the imaging radioisotope gallium-68 (68Ga) into the pores of the azide-functionalized NaY zeolite to form a stable bifunctional molecular targeting vector. The result is a versatile clickable zeolite platform that can be tailored for future in vivo