Sample records for crystalline aluminosilicate zeolite

  1. Catalytic conversion of an organic charge using new crystalline aluminosilicate

    SciTech Connect

    Chu, P.; Herbst, J.A.; Klocke, D.J.; Vartuli, J.

    1991-07-09

    This patent describes a process for effecting catalytic conversion of an organic charge. It comprises contacting the charge under catalytic conversion conditions with a catalyst comprising a synthetic porous crystalline aluminosilicate zeolite material having a silica to alumina molar ratio of from about 5 to about 500, the porous crystalline material in the uncalcined state being characterized by an x-ray diffraction pattern.

  2. Catalytic pyrolysis using UZM-44 aluminosilicate zeolite

    DOEpatents

    Nicholas, Christopher P; Boldingh, Edwin P

    2014-04-29

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

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

    Microsoft Academic Search

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

    2006-01-01

    Zeolites are a family of crystalline aluminosilicate materials widely used as shape-selective catalysts, ion exchange materials, and adsorbents for organic compounds. In the present work, zeolites were synthesized by adding a rationally designed amphiphilic organosilane surfactant to conventional alkaline zeolite synthesis mixtures. The zeolite products were characterized by a complementary combination of X-ray diffraction (XRD), nitrogen sorption, scanning electron microscopy

  4. Calorimetric determination of the acidic character of amorphous and crystalline aluminosilicates

    Microsoft Academic Search

    Brindusa Dragoi; Antonella Gervasini; Emil Dumitriu; Aline Auroux

    2004-01-01

    Aluminosilicates can present different structures such as crystalline true zeolite molecular sieves or amorphous silica–aluminas. With a large surface area available, both can be involved as catalysts, adsorbents or catalyst supports, and the determination of their surface acidic properties is an important parameter in the study of such materials.The number, strength and strength distribution of the acidic sites were determined

  5. Structured carbon adsorbents from clay, zeolite and mesoporous aluminosilicate templates

    Microsoft Academic Search

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

    2003-01-01

    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

  6. Comparative investigation of the catalytic properties of crystalline aluminosilicates of various types. Communication 3. Selectivity of the conversion of methanol on zeolites of various types

    SciTech Connect

    Stepanov, V.G.; Gonyshev, A.P.; Ione, K.G.

    1983-02-10

    Zeolites of types A, X, and Y are used as catalysts for the dehydration of alochols to olefins. In view of the interest in the synthesis of fuel from nonpetroleum raw material, the process of high-temperature conversion of alcohol is considered as a promising method for obtaining gasolines. In particular, a method has been developed for obtaining high-octane fuels from methanol using silica-rich zeolites of the ZSM type. In the present investigation a comparative study has been made of the selectivity of the action of zeolites of the type of mordenite and erionite and of silica-rich zeolites (TsVK) in reactions of methanol at various contact times.

  7. Catalytic pyrolysis using UZM-39 aluminosilicate zeolite

    DOEpatents

    Nicholas, Christopher P; Boldingh, Edwin P

    2014-10-07

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

  8. Facile synthesis of mesoporous aluminosilicates constructed with crystalline microporous frameworks

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

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

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

    Microsoft Academic Search

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

    2007-01-01

    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

  10. Simple strategies for fabrication of a periodic mesoporous aluminosilicate with crystalline walls.

    PubMed

    Do, Manh Huy; Wang, Tuo; Cheng, Dang-guo; Chen, Fengqiu; Zhan, Xiaoli; Rioux, Robert M; Gong, Jinlong

    2014-11-12

    An alkali-assisted cooperative assembly process of two different templating systems with aluminosilicate precursors is described. A highly ordered mesoporous zeolite with the 2D hexagonal symmetry mesospores and MFI zeolitic framework walls is synthesized. This method also allows the preparation of ZSM-5 with c- or b-axis-aligned mesopores. The materials have promising catalytic activities for organic reactions involving bulky molecules. PMID:25049062

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

    PubMed

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

    2002-11-01

    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

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    Martian rocks and sediments contain weathering products including evaporite salts and clay minerals that only form as a result of interaction between rocks and water [1-6]. These weathering products are key to studying the history of water on Mars because their type, abundance and location provide clues to past conditions on the surface of the planet, as well as to the possible location of present-day reservoirs of water. Weathering of terrestrial volcanic rocks similar to those on Mars produces nano-sized, variably hydrated aluminosilicate and iron oxide minerals [7-10] including allophane, imogolite, halloysite, hisingerite, and ferrihydrite. The nanoaluminosilicates can contain isomorphically substituted Fe, which affects their spectral and physical properties. Detection and quantification of such minerals in natural environments on earth is difficult due to their variable chemical composition and lack of long-range crystalline order [9, 11, 12]. Despite the difficulty in characterizing these materials, they are common on Earth, and data from orbital remote sensing and rover-based instruments suggest that they are also present on Mars [9, 10, 13-17]. Their accurate detection and quantification require a better understanding of how composition affects their spectral properties. We present here the results of XAFS spectroscopy; these results will be corroborated with planned Mossbauer and reflectance spectroscopy.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  14. One-pot synthesis of hierarchical FeZSM-5 zeolites from natural aluminosilicates for selective catalytic reduction of NO by NH3.

    PubMed

    Yue, Yuanyuan; Liu, Haiyan; Yuan, Pei; Yu, Chengzhong; Bao, Xiaojun

    2015-01-01

    Iron-modified ZSM-5 zeolites (FeZSM-5s) have been considered to be a promising catalyst system to reduce nitrogen oxide emissions, one of the most important global environmental issues, but their synthesis faces enormous economic and environmental challenges. Herein we report a cheap and green strategy to fabricate hierarchical FeZSM-5 zeolites from natural aluminosilicate minerals via a nanoscale depolymerization-reorganization method. Our strategy is featured by neither using any aluminum-, silicon-, or iron-containing inorganic chemical nor involving any mesoscale template and any post-synthetic modification. Compared with the conventional FeZSM-5 synthesized from inorganic chemicals with the similar Fe content, the resulting hierarchical FeZSM-5 with highly-dispersed iron species showed superior catalytic activity in the selective catalytic reduction of NO by NH3. PMID:25791958

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  16. Influence of starting zeolite on synthesis of RUT type zeolite by interzeolite conversion method

    NASA Astrophysics Data System (ADS)

    Itakura, Masaya; Ota, Kai; Shibata, Shohei; Inoue, Takayuki; Ide, Yusuke; Sadakane, Masahiro; Sano, Tsuneji

    2011-01-01

    In this study, hydrothermal conversions of *BEA and FAU type zeolites using various structure-directing agents were carried out. Highly crystalline and pure RUT type zeolites were obtained from both zeolites in the presence of tetramethylammonium hydroxide. There were no major differences between the characteristics of the RUT type zeolites obtained from the two starting zeolites. However, the Si/Al ratio and the crystallization rate of the RUT type zeolites were strongly dependent on both the framework structure and the Si/Al ratio of the starting zeolite. That is, the crystallization rate of the RUT type zeolite from the *BEA type zeolite did not depend on the Si/Al ratio of the starting *BEA type zeolite, whereas the crystallization rate of the RUT type zeolite from the FAU type zeolite was dependent on the Si/Al ratio of the starting FAU type zeolite. This suggests that the chemical structure and the concentration of locally ordered aluminosilicate species produced by the decomposition/dissolution of the starting zeolite can be altered by changing the framework structure of the zeolite.

  17. Co-development of crystalline and mesoscopic order in mesostructured zeolite nanosheets.

    PubMed

    Messinger, Robert J; Na, Kyungsu; Seo, Yongbeom; Ryoo, Ryong; Chmelka, Bradley F

    2015-01-12

    Mesoporous zeolites are a new and technologically important class of materials that exhibit improved diffusion and catalytic reaction properties compared to conventional zeolites with sub-nanometer pore dimensions. During their syntheses, the transient developments of crystalline and mesoscopic order are closely coupled and challenging to control. Correlated solid-state NMR, X-ray, and electron microscopy analyses yield new molecular-level insights on the interactions and distributions of complicated organic structure-directing agents with respect to crystallizing zeolite frameworks. The analyses reveal the formation of an intermediate layered silicate phase, which subsequently transforms into zeolite nanosheets with uniform nano- and mesoscale porosities. Such materials result from coupled surfactant self-assembly and inorganic crystallization processes, the interplay between which governs the onset and development of framework structural order on different length and time scales. PMID:25412768

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

    ERIC Educational Resources Information Center

    Saini, Vipin K.; Pires, Joao

    2012-01-01

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

  19. Dietary supplementation with the tribomechanically activated zeolite clinoptilolite in immunodeficiency: Effects on the immune system

    Microsoft Academic Search

    Slavko Ivkovic; Ulrich Deutsch; Angelika Silberbach; Erwin Walraph; Marcus Mannel

    2004-01-01

    Natural zeolites are crystalline aluminosilicates with unique adsorption, cationexchange, and catalytic properties that have\\u000a multiple uses in industry and agriculture. TMAZ®, a natural zeolite clinoptilolite with enhanced physicochemical properties,\\u000a is the basis of the dietary supplements Megamin® and Lycopenomin®, which have demonstrated antioxidant activity in humans.\\u000a The aim of this prospective, open, and controlled parallel-group study was to investigate the

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

    SciTech Connect

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

    1984-11-01

    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.

  1. Sodium Aluminosilicate Solid Phase Specific Fouling Behaviour

    Microsoft Academic Search

    Jonas Addai-Mensah; Jun Li; Marek Zbik; Scott Rosencrance

    2004-01-01

    Process heat transfer equipment fouling due to sodium aluminosilicate precipitation is a serious problem that confronts high-level nuclear waste liquor and Bayer process alumina processing plants. The fouling of 316 stainless steel substrate by thermodynamically stable and unstable sodium aluminosilicate polytypes: amorphous solid, zeolite A, sodalite and cancrinite crystals, been has studied in an isothermal, batch precipitation system at 65

  2. Direct Probe Fourier Transform Far-Infrared Spectroscopy of Metal Atoms, Metal Ions, and Metal Clusters in Zeolites

    Microsoft Academic Search

    Mark D. Baker; Geoffrey A. Ozin; John Godber

    1985-01-01

    A class of crystalline aluminosilicates, known as the zeolites, are widely used as effective heterogeneous catalysts in the chemical industry. They possess excellent stability, activity and selectivity patterns for a wide range of hydrocarbon transformations [1–10]. X-ray diffraction studies have shown that zeolites are giant macromolecules formed by AlO4 and SiO4 tetrahedra joined by shared oxygens, and the structures of

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

    Microsoft Academic Search

    F. G. Dwyer; W. E. Garwood

    1984-01-01

    Straight-chain hydrocarbons and slightly branched chain hydrocarbons are selectively converted utilizing highly siliceous porous crystalline materials of the zeolite type having SiOâ\\/AlâOâ 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

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

    PubMed

    Hui, K S; Chao, C Y H

    2006-09-01

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

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

    Microsoft Academic Search

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

    2011-01-01

    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

  6. Comparative investigation of the catalytic properties of crystalline aluminosilicates of different types. 2. Selectivity in the cracking of n-octane

    SciTech Connect

    Stepanov, V.G.; Mastikhin, V.M.; Ione, K.G.

    1982-09-20

    This investigation examines the dependence of the rate and selectivity of the cracking of n-octane over zeolites of the above-mentioned types on the state of the aluminum atoms present. To ensure the correctness of the comparative determinations of the catalytic properties of the zeolites, the contact times were varied over a range of three to four orders of magnitude. Results indicated that the cracking of paraffins over decationized type Y zeolites, mordenites, erionite, and high-silica zeolites (HSZ) occurs by the same route: paraffins ..-->.. unsaturated fragments ..-->.. paraffinic fragments and monoaromatic hydrocarbons ..-->.. polyalkylaromatic (nondesorbed) compounds. The extent of conversion of the intermediate products, and hence the selectivity of cracking, was determined for erionite by the geometrical parameters of the pore structure, and for type Y zeolites, mordenites, and HSZ, by the concentration of groups which include aluminum atoms in cationic positions. Results also indicated that on type Y zeolites with the greatest concentration of aluminum atoms in cationic positions, conversion of the hydrocarbons proceeds as far as the formation of nondesorbed compounds, and on HSZ with the lowest concentration of such sites, it proceeds as far as the formation of monaromatic compounds.

  7. A comparative investigation of the catalytic properties of crystalline aluminosilicates of different types. 2. Selectivity in the cracking of n-octane

    SciTech Connect

    Stepanov, V.G.; Mastikhin, V.M.; Ione, K.G.

    1982-03-01

    This investigation examines the dependence of the rate and selectivity of the cracking of n-octane over zeolites on the state of the aluminum atoms present. To ensure the correctness of the comparative determinations of the catalytic properties of the zeolites, the contact times were varied over a range of three to four orders of magnitude. The cracking of paraffins over decationized type Y zeolites, mordenites, erionite, and high-silica zeolites (HSZ) occurs by the same route: paraffins ..-->.. unsaturated fragments ..-->.. paraffinic fragments and monoaromatic hydrocarbons ..-->.. polyalkylaromatic (nondesorbed) compounds. The extent of conversion of the intermediate products, and hence the selectivity of cracking, is determined for erionite by the geometrical parameters of the pore structure, and for type Y zeolites, mordenites, and HSZ, by the concentration of groups which include aluminum atoms in cationic positions. On type Y zeolites with greatest concentration of aluminum atoms in cationic positions, conversion of the hydrocarbons proceeds as far as the formation of nondesorbed compounds, and on HSZ with the lowest concentration of such sites, it proceeds as far as the formation of monoaromatic compounds.

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

    NASA Astrophysics Data System (ADS)

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

    2004-09-01

    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.

  9. Molecular simulations and experimental studies of zeolites

    Microsoft Academic Search

    Eric C. Moloy

    2004-01-01

    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,

  10. Calibration analysis of zeolites by laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

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

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

    PubMed

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

    2009-09-10

    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

  12. Zeolite Beta nanosized assemblies

    Microsoft Academic Search

    G. Majano; S. Mintova; O. Ovsitser; B. Mihailova; T. Bein

    2005-01-01

    Nanosized zeolite Beta assemblies are prepared by a steam assisted conversion (SAC) method from micron-sized porous amorphous silica grains soaked in clear solutions containing the alumina source and organic template. The zeolite Beta assemblies are built of closely packed uniform nanocrystals (100nm) and retain the size and morphological features of the primary silica grains. The crystallinity and the phase purity

  13. Microprobes aluminosilicate ceramic membranes

    DOEpatents

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

    1993-01-01

    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.

  14. Sorption of {sup 239}Np and {sup 235}U fission products by zeolite Y, Mexican natural erionite, and bentonite

    SciTech Connect

    Olguin, M.T.; Solache, M.; Iturbe, J.L. [Instituto Nacional de Investigaciones Nucleares, C.P. (Mexico)]|[Universidad Autonoma Metropolitana, C.P. (Mexico)] [and others

    1996-09-01

    Zeolite Y, erionite, and bentonite have been used in this work to remove {sup 239}Np and {sup 235}U fission products from aqueous solutions at various pH values. It was found that the sorption of fission products by aluminosilicates takes place by different mechanisms, mainly ion exchange, precipitation, and electrostatic surface interaction. The radionuclides content was determined by {gamma}-spectrometry, and X-ray diffraction was used to learn whether the solids maintained their crystallinity at different pH values.

  15. Spectroscopic signatures of nitrogen-substituted zeolites.

    PubMed

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

    2008-11-12

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

  16. Demonstrating the benefits and pitfalls of various acidity characterization techniques by a case study on bimodal aluminosilicates.

    PubMed

    Van Oers, Cynthia J; Góra-Marek, Kinga; Prelot, Bénédicte; Datka, Jerzy; Meynen, Vera; Cool, Pegie

    2014-02-25

    A new combination of a volumetric with a dynamic method to investigate the acidity properties of aluminosilicates is introduced. In the first step, the total acidity is determined volumetrically by the measurement of two-cycle adsorption (TCA) isotherms with ammonia as a probe, directly followed by a dynamic temperature-programmed desorption (TPD) experiment to define the acid strength distribution. Furthermore, the results obtained by the new direct combination of TCA and TPD are validated by comparison with an in-situ FTIR (Fourier transform infrared) study with the same probe molecule on the same materials. Both acidity characterization techniques are compared, and we comment on their complementarity, benefits, and pitfalls. The material under investigation is a new type of bimodal microporous and mesoporous material with zeolitic characteristics, synthesized by a mesotemplate-free method. The acidic nature of the novel material is compared to two reference materials: a crystalline zeolite and a mesoporous aluminum incorporated mesocellular foam (Al-MCF) with amorphous characteristics. PMID:24471941

  17. Uranium and Aluminosilicate Surface Precipitation Tests

    SciTech Connect

    Hu, M.Z.

    2002-11-27

    The 2H evaporator at the Savannah River Site has been used to treat an aluminum-rich waste stream from canyon operations and a silicon-rich waste stream from the Defense Waste Processing Facility. The formation of aluminosilicate scale in the evaporator has caused significant operational problems. Because uranium has been found to accumulate in the aluminosilicate solids, the scale deposition has introduced criticality concerns as well. The objective of the tests described in this report is to determine possible causes of the uranium incorporation in the evaporator scale materials. The scope of this task is to perform laboratory experiments with simulant solutions to determine if (1) uranium can be deposited on the surfaces of various sodium aluminosilicate (NAS) forms and (2) aluminosilicates can form on the surfaces of uranium-containing solids. Batch experiments with simulant solutions of three types were conducted: (1) contact of uranium solutions/sols with NAS coatings on stainless steel surfaces, (2) contact of uranium solutions with NAS particles, and (3) contact of precipitated uranium-containing particles with solutions containing aluminum and silicon. The results show that uranium can be incorporated in NAS solids through encapsulation in bulk agglomerated NAS particles of different phases (amorphous, zeolite A, sodalite, and cancrinite) as well as through heterogeneous deposition on the surfaces of NAS coatings (amorphous and cancrinite) grown on stainless steel. The results also indicate that NAS particles can grow on the surfaces of precipitated uranium solids. Particularly notable for evaporator operations is the finding that uranium solids can form on existing NAS scale, including cancrinite solids. If NAS scale is present, and uranium is in sufficient concentration in solution to precipitate, a portion of the uranium can be expected to become associated with the scale. The data obtained to date on uranium-NAS affinity are qualitative. A necessary next step is to quantitatively determine the amounts of uranium that may be incorporated into NAS scale solids under differing conditions e.g., varying silicon/aluminum ratio, uranium concentration, temperature, and deposition time.

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

    PubMed

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

    2010-01-19

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

  19. Salt-occluded zeolite waste forms: Crystal structures and transformability

    SciTech Connect

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

    1996-12-31

    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.

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

    SciTech Connect

    THOMA,STEVEN G.; NENOFF,TINA M.

    2000-07-14

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

  1. 21 CFR 582.2727 - Sodium aluminosilicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...SAFE Anticaking Agents § 582.2727 Sodium aluminosilicate. (a) Product. Sodium aluminosilicate (sodium silicoaluminate). (b) Tolerance...substance is generally recognized as safe for use at a level not exceeding 2 percent in...

  2. 21 CFR 582.2727 - Sodium aluminosilicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...SAFE Anticaking Agents § 582.2727 Sodium aluminosilicate. (a) Product. Sodium aluminosilicate (sodium silicoaluminate). (b) Tolerance...substance is generally recognized as safe for use at a level not exceeding 2 percent in...

  3. 21 CFR 182.2727 - Sodium aluminosilicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...SAFE Anticaking Agents § 182.2727 Sodium aluminosilicate. (a) Product. Sodium aluminosilicate (sodium silicoaluminate). (b) Tolerance...substance is generally recognized as safe for use at a level not exceeding 2 percent in...

  4. Crystalline Membranes

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

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

  5. Binding and catalytic reduction of NO by transition metal aluminosilicates

    SciTech Connect

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

    1991-09-01

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

  6. Mesoporous MCM-41 aluminosilicates as model silica-alumina catalysts: Spectroscopic characterization of the acidity

    SciTech Connect

    Di Renzo, F.; Chiche, B.; Fajula, F. [ENSCM, Montpellier (France); Viale, S.; Garrone, E. [Universita di Torino (Italy)

    1996-12-31

    The synthesis procedure brings about a low threshold value for the surface concentration of Al species and renders MCM-41 a model system for the study of silica-alumina phases. On severely outgassed samples, two types of Lewis sites are present, differing in their protrusion from the surface, as well as Bronsted sites engaged in lateral H-bonding, evidenced by the interaction with NH{sub 3} and CO. The conversion of Lewis sites into Bronsted ones by water adsorption shows that the Bronsted species are Si(OH)Al, typical of zeolites, and Si-Al(OH)-Si, found in dealuminated zeolites. The flexibility of the amorphous framework accounts for the differences with zeolitic aluminosilicates.

  7. Smart zeolites: New forms of tungsten and molybdenum oxides

    SciTech Connect

    Ozin, G.A.; Prokopowicz, R.A. (Univ. of Toronto, Ontario (Canada)); Oezkar, S. (Middle East Technical Univ., Ankara (Turkey))

    1992-12-01

    In this Account, the authors describe their recent research efforts involving the use of volatile hexacarbonylmolybdenum and -tungstem compounds, as precursors in the synthesis of highly organized assemblies of molecular dimension molybdenum and tungsten oxides, encapsulated within the diamond network of 13-[Angstrom] supercages found in zeolite Y. These assemblies are extremely uniform in terms of their nuclearity and structure, and their exclusive internal confinement inside of and lack of significant perturbation of the zeolite Y host. In these materials, the bulk form of the metal oxide has essentially been reconstituted within the nanoscale void spaces of a crystalline aluminosilicate framework host. The electronic and structural properties of these molecular metal oxide arrays can be easily manipulated as a result of their facile redox interconvertibility, and the further capability of fine tuning their electronic enviornment by choosing which charge-balancing cation is present in the supercage. Bulk forms of WO[sub 3] and MoO[sub 3], which possess octahedral building blocks arranged into open framework, layer, and tunnel structures, are probably most famous for their ability to reversibly accept metal cations and protons into their internal void spaces and electron-charge-transfer equivalents into their conduction bands. This fascinating property enables them to function as intelligent materials in, for example, electrochromic windows, mirrors and displays, rechargeable solid-state batteries, pH-microelectrochemical transistors, and chemical sensors. In addition, their narrow-band-gap semiconductor properties allow them to be usefully exploited in liquid junction solar and electrochemical cells.23 refs., 5 figs., 1 tab.

  8. 21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2010-04-01 false Hydrated sodium calcium aluminosilicate. 582.2729 Section...Agents § 582.2729 Hydrated sodium calcium aluminosilicate. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

  9. 21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 2012-04-01 false Sodium calcium aluminosilicate, hydrated. 182...Anticaking Agents § 182.2729 Sodium calcium aluminosilicate, hydrated. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

  10. 21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 2011-04-01 false Sodium calcium aluminosilicate, hydrated. 182...Anticaking Agents § 182.2729 Sodium calcium aluminosilicate, hydrated. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

  11. 21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2010-04-01 2009-04-01 true Sodium calcium aluminosilicate, hydrated. 182...Anticaking Agents § 182.2729 Sodium calcium aluminosilicate, hydrated. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

  12. 21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 2014-04-01 false Sodium calcium aluminosilicate, hydrated. 182...Anticaking Agents § 182.2729 Sodium calcium aluminosilicate, hydrated. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

  13. 21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 false Hydrated sodium calcium aluminosilicate. 582.2729 Section...Agents § 582.2729 Hydrated sodium calcium aluminosilicate. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

  14. 21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 false Hydrated sodium calcium aluminosilicate. 582.2729 Section...Agents § 582.2729 Hydrated sodium calcium aluminosilicate. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

  15. 21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 false Hydrated sodium calcium aluminosilicate. 582.2729 Section...Agents § 582.2729 Hydrated sodium calcium aluminosilicate. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

  16. 21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...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...

  17. 21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...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...

  18. Synthesis and characterization of a new zeolite of the offretite type

    SciTech Connect

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

    1982-03-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

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

  20. Density of molten sodium aluminosilicates

    SciTech Connect

    Stein, D.J.; Stebbins, J.F.; Carmichael, I.S.E.

    1986-05-01

    In order to address controversial discrepancies among earlier measurements, the densities of eight sodium aluminosilicate melts were measured at 1100/sup 0/ to 1550/sup 0/C. The double-bob Archimedean method was used; it is the most accurate available technique and one not used in previous density measurements in this system. The results of a regression of molar volume with temperature and composition in terms of oxides are presented. The variation of molar volume with composition is linear within the range of the data. The standard error of the fit is <0.2%.

  1. Zeolite guest-host interactions: Implications in formation, catalysis, and photochemistry

    Microsoft Academic Search

    Prabir K. Dutta

    1995-01-01

    This review primarily focuses on contributions of our research group in the area of zeolite guesthost chemistry. The perturbation of the Raman spectra of the organic structure-directing-agents during synthesis of zeolites ZK-4, ZSM-5, and ferrierite show clearly the entrapment of the organic by the aluminosilicate framework. The microordering around the organic coincides with the development of longrange-order typical of crystal

  2. Mesoporous materials with zeolite framework: remarkable effect of the hierarchical structure for retardation of catalyst deactivation.

    PubMed

    Srivastava, Rajendra; Choi, Minkee; Ryoo, Ryong

    2006-11-21

    Hierarchical MFI zeolite was synthesized following a synthesis route using organic-inorganic hybrid surfactants; the resultant zeolite with mesoporous/microporous hierarchical structure exhibited remarkably high resistance to deactivation in catalytic activity of various reactions such as isomerization of 1,2,4-trimethylbenzene, cumene cracking, and esterification of benzyl alcohol with hexanoic acid, as compared with conventional MFI and mesoporous aluminosilicate MCM-41. PMID:17283794

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

    Microsoft Academic Search

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

    1997-01-01

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

  4. Amphiphilic Organic-Inorganic Hybrid Zeotype Aluminosilicate like a Nanoporous Crystallized Langmuir-Blodgett Film.

    PubMed

    Ikeda, Takuji; Hiyoshi, Norihito; Matsuura, Shun-Ichi; Kodaira, Tetsuya; Nakaoka, Takuma; Irisa, Ami; Kawano, Miki; Yamamoto, Katsutoshi

    2015-06-26

    A new organic-inorganic hybrid zeotype compound with amphiphilic one-dimensional nanopore and aluminosilicate composition was developed. The framework structure is composed of double aluminosilicate layers and 12-ring nanopores; a hydrophilic layer pillared by Q(2) silicon atom species and a lipophilic layer pillared by phenylene groups are alternately stacked, and 12-ring nanopores perpendicularly penetrate the layers. The framework topology looks similar to that of an AFI-type zeolite but possesses a quasi-multidimensional pore structure consisting of a 12-ring channel and intersecting small pores equivalent to 8-rings. The hybrid material with alternately laminated lipophilic and hydrophilic nanospaces can be assumed as a crystallized Langmuir-Blodgett film. It demonstrates microporous adsorption for both hydrophilic and lipophilic adsorptives, and its outer surface tightly adsorbs lysozyme whose molecular size is much larger than its micropore opening. Our results suggest the possibility of designing porous adsorbent with high amphipathicity. PMID:26012531

  5. Regenerative Cu/La zeolite supported desulfurizing sorbents

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  6. Formulation of cracking catalyst based on zeolite and natural clays

    Microsoft Academic Search

    R. R. Aliev; M. I. Lupina

    1995-01-01

    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,

  7. Sorption of Np and U Fission Products by Zeolite Y, Mexican Natural Erionite, and Bentonite

    Microsoft Academic Search

    M. T. Olguín; M. Solache; J. L. Iturbe; P. Bosch; S. Bulbulian

    1996-01-01

    Zeolite Y, erionite, and bentonite have been used in this work to remove Np and U fission products from aqueous solutions at various pH values. It was found that the sorption of fission products by aluminosilicates takes place by different mechanisms, mainly ion exchange, precipitation, and electrostatic surface interaction. The radio nuclides content was determined by ?-spectrometry, and x-ray diffraction

  8. Coal rank and illite crystallinity associated with the zeolite facies of Southland and the pumpellyite-bearing facies of Otago, southern New Zealand

    Microsoft Academic Search

    Hanan J. Kisch

    1981-01-01

    Coal rank (vitrinite reflectance) and clay mineralogy from the North Range Group of the Southland Syncline, and illite crystallinity in pumpellyite- and lawsonite-bearing terranes in the textural zone I of the Caples and Torlesse terranes were studied.Vitrinite reflectances range from 0.60 to 1.33% R (high-volatile C to medium-volatile bituminous coal ranks) in 31 out of 34 samples studied; in the

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

    PubMed

    Vai?iukynien?, Danut?; Kantautas, Aras; Vaitkevi?ius, Vitoldas; Jakevi?ius, Leonas; Rudžionis, Žymantas; Paškevi?ius, Mantas

    2015-11-01

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

  10. Microporous and mesoporous aluminosilicates as catalysts for the cracking of Fischer-Tropsch waxes towards the production of “clean” bio-fuels

    Microsoft Academic Search

    K. S. Triantafyllidis; V. G. Komvokis; M. C. Papapetrou; I. A. Vasalos; A. A. Lappas

    2007-01-01

    The potential utilization of various microporous (zeolites H-Y and H-ZSM-5) and mesoporous (amorphous silica-alumina and Al-MCM-41) aluminosilicates as catalysts or active matrices in the cracking of Fischer-Tropsch waxes towards the production of liquid fuels was the subject of this study. Focus was placed on the effect of porous and acidic characteristics of the materials on products yields and properties. Both

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

    SciTech Connect

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

    2000-02-16

    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.

  12. 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...

  13. Aluminosilicate melts: structure, composition and temperature

    Microsoft Academic Search

    Bjorn Mysen

    1997-01-01

    The anionic structure of aluminosilicate melts of intermediate degree of polymerization (NBO\\/T = 0.5) and with along the composition join (LS4-LA4) has been examined in-situ to ˜1480?°C, and compared with recent data for melts along the analog composition join\\u000a and with less polymerized melts along the join and O_5. With , the anionic equilibrium, (1) , adequately describes the structure.

  14. Pervaporation performance of PDMS-Ni 2+Y zeolite hybrid membranes in the desulfurization of gasoline

    Microsoft Academic Search

    Ben Li; Dan Xu; Zhongyi Jiang; Xiongfei Zhang; Wanpeng Liu; Xiao Dong

    2008-01-01

    PDMS-Ni2+Y zeolite hybrid membranes were fabricated and used for the pervaporation removal of thiophene from model gasoline system. The structural morphology, mechanical stability, crystallinity, and free volume characteristics of the hybrid membranes were systematically investigated. Molecular dynamics simulation was employed to calculate the diffusion coefficients of small penetrants in the polymer matrix and the zeolite. The effect of Ni2+Y zeolite

  15. 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)

    Cerefice, Gary; Ma, Longzhou; Kaminski, Michael

    2009-12-01

    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.

  16. Controlling size and yield of zeolite Y nanocrystals using tetramethylammonium bromide

    Microsoft Academic Search

    Brett A. Holmberg; Huanting Wang; Joseph M. Norbeck; Yushan Yan

    2003-01-01

    In this study, we developed an alternative synthesis technique for the production of small colloidal zeolite Y nanocrystals. By adding tetramethylammonium bromide as a second source of organic template, we were able to decouple and investigate the effect of two important synthesis parameters, tetramethylammonium concentration and anion concentration. Optimizing these two parameters allowed us to hydrothermally synthesize highly crystalline zeolite

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

    PubMed

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

    2015-07-14

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

  18. Colossal cages in zeolitic imidazolate frameworks as selective carbon dioxide reservoirs

    Microsoft Academic Search

    Bo Wang; Adrien P. Côté; Hiroyasu Furukawa; Michael O'Keeffe; Omar M. Yaghi

    2008-01-01

    Zeolitic imidazolate frameworks (ZIFs) are porous crystalline materials with tetrahedral networks that resemble those of zeolites: transition metals (Zn, Co) replace tetrahedrally coordinated atoms (for example, Si), and imidazolate links replace oxygen bridges. A striking feature of these materials is that the structure adopted by a given ZIF is determined by link-link interactions, rather than by the structure directing agents

  19. Exceptional chemical and thermal stability of zeolitic imidazolate frameworks

    PubMed Central

    Park, Kyo Sung; Ni, Zheng; Côté, Adrien P.; Choi, Jae Yong; Huang, Rudan; Uribe-Romo, Fernando J.; Chae, Hee K.; O’Keeffe, Michael; Yaghi, Omar M.

    2006-01-01

    Twelve zeolitic imidazolate frameworks (ZIFs; termed ZIF-1 to -12) have been synthesized as crystals by copolymerization of either Zn(II) (ZIF-1 to -4, -6 to -8, and -10 to -11) or Co(II) (ZIF-9 and -12) with imidazolate-type links. The ZIF crystal structures are based on the nets of seven distinct aluminosilicate zeolites: tetrahedral Si(Al) and the bridging O are replaced with transition metal ion and imidazolate link, respectively. In addition, one example of mixed-coordination imidazolate of Zn(II) and In(III) (ZIF-5) based on the garnet net is reported. Study of the gas adsorption and thermal and chemical stability of two prototypical members, ZIF-8 and -11, demonstrated their permanent porosity (Langmuir surface area = 1,810 m2/g), high thermal stability (up to 550°C), and remarkable chemical resistance to boiling alkaline water and organic solvents. PMID:16798880

  20. The geopolymerisation of alumino-silicate minerals

    Microsoft Academic Search

    Hua Xu; J. S. J. Van Deventer

    2000-01-01

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

  1. Y zeolite from kaolin taken in Yen Bai-Vietnam: Synthesis, characterization and catalytic activity for the cracking of n-heptane

    Microsoft Academic Search

    Ta Ngoc Don; Vu Dao Thang; Pham Thanh Huyen; Pham Minh Hao; Nguyen Khanh Dieu Hong

    2006-01-01

    This paper is concerned with the synthesis of Y zeolite with SiO2\\/Al2O3 ratio of 4.5 from kaolin taken in Yen Bai-Vietnam and their catalytic activity for the cracking of n-heptane. The synthesized sample (NaY1) showed the Y zeolite crystallinity of 53% and P1 zeolite crystallinity of 32%, and exhibited good thermal stability up 880°C. The activity and the stability of

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

    PubMed Central

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

    2013-01-01

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

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

    SciTech Connect

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

    1997-10-01

    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.

  4. Synthesis, characterization and reactivity of transition-metal-containing zeolites

    SciTech Connect

    Rossin, J.A.

    1986-01-01

    Transition metal containing zeolites (zeolite A and ZSM-5) were prepared by addition of various transition metal containing substrates to zeolite synthesis gels. Crystal growth data were recorded in order to determine the influence of the transition metal species on the rate of crystal growth. X-ray diffraction, oxygen adsorption, FTIR and SEM were utilized to evaluate crystal purity. X-ray photoelectron spectroscopy (XPS), chemical analysis and electron microprobe analysis were performed in order to ascertain the position (intrazeolitic versus surface) and homogeneity of the transition metal. It was concluded that intrazeolitic transition metals are produced by the novel procedure presented in this work. 1-Hexane hydroformylation by rhodium zeolite A showed intrazeolitic rhodium to migrate to the external surface of the zeolite. However, in the presence of a solution and surface rhodium poison, intrazeolitic rhodium was found to hydroformylate 1-hexene exclusively to heptanal. Ruthenium containing zeolite A was evaluated under CO-hydrogenation conditions. No migration of intrazeolitic ruthenium to the external surface of the zeolite was observed over the course of the reaction. The product distribution obtained for this catalyst did not follow a log normal behavior. Also, loss of zeolite crystallinity was observed following the reaction. Cobalt ZSM-5 was evaluated under CO-hydrogenation conditions. No migration of cobalt to the external surface of the zeolite occurred. XPS analysis of the catalyst following various stages of the reaction indicated that intrazeolitic cobalt was not reduced to the zero valent state. Consequently, the non-zero valent cobalt was not capable of hydrogenating carbon monoxide.

  5. Synthesis of multiwall carbon nanotubes by using mesoporous aluminosilicates

    Microsoft Academic Search

    Vanessa Gallego; Luis F. Giraldo; Betty L. López; Ligia Sierra

    2008-01-01

    Multiwall carbon nanotubes (MWCNTs) have been synthesized by catalytic chemical vapor deposition (CCVD) of ethylene on several mesoporous aluminosilicates impregnated with iron. The aluminosilicates were synthesized by sol-gel method optimizing the Si\\/Al ratios from 6 to 80. The catalysts are characterized by nitrogen adsorption, X-ray diffraction, 27Al NMR, thermogravimetric analysis (TGA) and infrared. The MWCNTs are characterized by TGA and

  6. Reaction of vitreous silicates and sodium aluminosilicates with aqueous solutions

    Microsoft Academic Search

    S. K. Dubrovo

    1954-01-01

    Summary 1.A study was made of the reaction with solutions of hydrochloric, nitric and sulfuric acids of vitreous sodium aluminosilicates composed of disilicate with additions of 0.15 to 1 mole Al2O3.2.Increasing hydrogen ion concentration when using one and the same acid is accompanied by increasing decomposability of those aluminosilicate glasses whose skeleton, due to depolymerization of their silica content, is

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

    PubMed

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

    2014-03-12

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

  8. Synthesis of colloidal suspensions of zeolite ZSM-2

    SciTech Connect

    Schoeman, B.J.; Sterte, J.; Otterstedt, J.E. [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Engineering Chemistry] [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Engineering Chemistry

    1995-03-15

    Discrete colloidal particles of zeolite ZSM-2 with crystal sizes less than 100 nm, in the form of aqueous suspensions, have been synthesized in tetramethylammonium (TMA)-aluminosilicate solutions in the presence of either lithium or a combination of lithium and sodium hydroxide. The well-crystallized ZSM-2 has a specific surface area of 781 m{sup 2}/g after purification and removal of the organic base by calcination. Synthesis times (t) are as short as 3 < t < 12 h and in certain cases, less than 3 h, less than those previously reported in the literature. Prolonged hydrothermal treatment of sols in the presence of sodium cations (>12 h) results in the phase transformation of ZSM-2 to the nitrogeneous edingtonite zeolite (Li,Na)-E. The synthesis of nitrogeneous (Li,Na)-E is also favored by a high TMA content in conjunction with sodium, whereas synthesis of zeolite N-A is favored by a high sodium content. Furthermore, it is shown that colloidal suspensions of TMA sodalite with crystal sizes less than 40 nm are synthesized in the absence of alkali cations.

  9. Hierarchical zeolites from class F coal fly ash

    NASA Astrophysics Data System (ADS)

    Chitta, Pallavi

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

  10. Investigation of aluminosilicate refractory for solid oxide fuel cell applications

    NASA Astrophysics Data System (ADS)

    Gentile, Paul Steven

    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 800°C and 1000°C. 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 1000°C 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 (<1000°C) 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 800-1000°C 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.

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

    PubMed

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

    2009-10-30

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

  12. Sorption effects in zeolite catalysis

    SciTech Connect

    Haag, W.O.

    1996-10-01

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

  13. Reactions of bicyclo(2,2. 1)hepta-2,5-diene in the presence of zeolites

    SciTech Connect

    Azbel', B.I.; Gol'dshleger, N.F.; Isakov, Ya.I.; Epel'baum, E.T.; Yampol'skii, Yu.Yu.; Minachev, Kh.M.

    1986-12-10

    In the interaction of bicyclo(2.2.1)hepta-2,5-diene with decationized and rare-earth zeolites (H-TsVM, H-Ultrasil, H-mordenite, NaNdY), including the dealuminized NdNaY', wide-pore aluminosilicates and filled zeolite (AShNTs), activated under conditions such that sorbed water remains in (or is added to) the catalyst, alcohols are formed - 3-hydroxynortricyclane and 3-dehydronorborneol - together with ethers 3-(tricyclo(2.2.1.0/sup 2,6/)-3'-heptyloxy)-bicyclo(2.2.1)hept-5-ene and 3,3'-oxydinortricyclane. With aromatic compounds in the presence of wide-pore REE-Y zeolites and also AShNTs, activated at 500/sup 0/C, norbornadiene forms alkylated products such as endo-5-phenyl-2-norbornene from benzene.

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

    PubMed

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

    2014-03-01

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

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

    SciTech Connect

    Schneider, E.

    1985-11-01

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

  16. UV-Raman and NMR spectroscopic studies on the crystallization of zeolite A and a new synthetic route.

    PubMed

    Ren, Limin; Li, Caijin; Fan, Fengtao; Guo, Qiang; Liang, Desheng; Feng, Zhaochi; Li, Can; Li, Shougui; Xiao, Feng-Shou

    2011-05-23

    UV-Raman and NMR spectroscopy, combined with other techniques, have been used to characterize crystallization of zeolite A. In situ UV-Raman spectroscopy shows that the starting gel for crystallization of zeolite A contains a lot of four-ring (4R) building units and the appearance of six-ring (6R) building blocks is the signal for crystal formation. (29)Si NMR spectroscopy results suggest that the starting gel is double four-ring (D4R) rich and during crystallization of zeolite A both ? and ? cages appear. (27)Al NMR spectroscopy results indicate the absence of Al (2Si) species in the starting gel, suggesting the absence of single 4R building units in the starting gel. Furthermore, composition analysis of both solid and liquid samples shows that the solid rather than liquid phase predominates for the crystallization of zeolite A. Therefore, it is proposed that the crystallization of zeolite A mainly occurs in the solid phase by self-assembly or rearrangement starting from the zeolite building units mainly consisting of D4R. The essential role of D4R is directly confirmed by successful conversion from a solution of D4R to zeolite A in the presence of NaCl, and the importance of solid phase is reasonably demonstrated by the successful synthesis of zeolite A from a dry aluminosilicate gel. By considering that the solid phase has a major contribution to crystallization, a novel route was designed to synthesizing zeolite A from the raw materials water glass (Na(2)SiO(3) in aqueous solution) and NaAlO(2), without additional water and NaOH; this route not only simplifies synthetic procedures, but reduces water consumption. PMID:21491521

  17. Pressure-induced hydration and cation migration in a Cs + exchanged gallosilicate zeolite LTL: Synchrotron X-ray powder diffraction study at ambient and high pressures

    Microsoft Academic Search

    Dong-hoon Seoung; Yongmoon Lee; Sun Jin Kim; Hyun-Hwi Lee; Docheon Ahn; Nam-Soo Shin; Thomas Vogt; Yongjae Lee

    2010-01-01

    The ambient and high pressure structures of a partially cesium-exchanged K-gallosilicate with a zeolite LTL framework topology (Cs0.65K0.35–GaSi–LTL) was studied using synchrotron X-ray powder diffraction. In contrast to the cation distribution present in the aluminosilicate analogues, the larger cesium cations replace part of the potassium cations in the narrow 8-ring channel as well as in the main 12-ring channel of

  18. XPS analysis of aluminosilicate microspheres bioactivity tested in vitro

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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.

  19. Hypothetical binodal zeolitic frameworks.

    PubMed

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

    2005-06-01

    Hypothetical binodal zeolitic structures (structures containing two kinds of tetrahedral sites) were systematically enumerated using tiling theory and characterized by computational chemistry methods. Each of the 109 refineable topologies based on "simple tilings" was converted into a silica polymorph and its energy minimized using the GULP program with the Sanders-Catlow silica potential. Optimized structural parameters, framework energies relative to alpha-quartz and volumes accessible to sorption have been calculated. Eleven of the 30 known binodal topologies listed in the Atlas of Zeolite Framework Types were found, leaving 98 topologies that were unknown previously. The chemical feasibility of each structure as a zeolite was evaluated by means of a feasibility factor derived from the correlation between lattice energy and framework density. Structures are divided into 15 families, based on common structural features. Many "feasible" structures contain only small pores. Several very open structures were also enumerated, although they contain three-membered rings which are thermodynamically disfavoured and not found in conventional zeolites. We believe that such topologies may be realizable as framework materials, but with different elemental compositions to those normally associated with zeolites. PMID:15914891

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

    NASA Astrophysics Data System (ADS)

    Kodumuri, Pradeep

    2009-12-01

    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.

  1. Effects of aluminosilicate minerals on copper–molybdenum flotation from Sarcheshmeh porphyry ores

    Microsoft Academic Search

    E. Jorjani; H. R. Barkhordari; M. Tayebi Khorami; A. Fazeli

    2011-01-01

    The presence of aluminosilicate minerals adversely affects the floatability of copper during processing of Sarcheshmeh porphyry ores. In this work, ores containing different types and quantities of aluminosilicate minerals, as well as copper sulfides (i.e., chalcopyrite and chalcocite), were examined in the laboratory to determine how aluminosilicate minerals affect the floatability of copper and to find ways to decrease their

  2. A high acid mesoporous USY zeolite prepared by alumination

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

  3. The influence of metakaulinite crystallinity on the properties of a geopolymer

    Microsoft Academic Search

    E. N. M. G. Pinto; M. A. F. Melo; A. E. Martinelli

    Geopolymers is a result of polymers condensation of alkali aluminosilicates and silicates causing three- dimensional polymer structures. The chemical and physico-chemical properties of their precursors influence directly on the properties of the material hardened. To understand what happens in geopolymerics pastes, this work studies the crystallinity of metakaulinite on the rheological and mechanical properties of geopolymer. It was hereby concluded

  4. Zeolite-based catalysts for chemicals synthesis

    Microsoft Academic Search

    M. E. Davis

    1998-01-01

    A survey of the types of active sites and reaction chemistries possible with zeolite-based catalyst systems is presented. Several trends in zeolite catalysis for chemicals synthesis are enumerated and suggestions for work provided. Two emerging areas of zeolite catalysis for fine chemicals preparation, namely, extra-large pore zeolite catalysts and chiral zeolite catalysis, are described.

  5. Heterostructured layered aluminosilicate-itraconazole nanohybrid for drug delivery system.

    PubMed

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

    2013-11-01

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

  6. ALUMINOSILICATE-COATED SILICA SAND FOR REACTIVE TRANSPORT EXPERIMENTS

    E-print Network

    Flury, Markus

    ALUMINOSILICATE-COATED SILICA SAND FOR REACTIVE TRANSPORT EXPERIMENTS By JORGE ANTONIO JEREZ transport experiments; Dr. Barbara Williams and Jason Shira from University of Idaho for providing access technical support and constructive iii #12;suggestions during my experiments, and Dr. Gang Chen who

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

    NASA Astrophysics Data System (ADS)

    Mysen, Bjorn O.

    2006-05-01

    Iron-57 resonant absorption Mössbauer 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 Mössbauer 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 Mössbauer 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.

  8. SO2 REMOVAL FROM FLUE GASES USING UTILITY SYNTHESIZED ZEOLITES

    SciTech Connect

    MICHAEL GRUTZECK

    1998-10-31

    It is well known that natural and synthetic zeolites (molecular sieves) can adsorb gaseous SO2 from flue gas and do it more efficiently than lime based scrubbing materials. Unfortunately their cost ($500-$800 per ton) has deterred their use in this capacity. It is also known that zeolites are easy to synthesize from a variety of natural and man-made materials. The overall objective of the current work has been to evaluate the feasibility of having a utility synthesize its own zeolites, on-site, from fly ash and other recycled materials and then use these zeolites to adsorb SO2 from their flue gases. Work to date has shown that the efficiency of the capture process is related to the degree of crystallinity and the type of zeolite that forms in the samples. Normally, those samples cured at 150°C contained a greater proportion of zeolite and as such were more SO2 adsorptive than their low-temperature counterparts. However, in order for the project to be successful, on site synthesis must remain an option, i.e. _100°C synthesis. In light of this, the experimental focus now has two aspects. First, compositions of the starting materials are being altered by blending the current suite of fly ashes with other fly ashes, ground glass cullet and silica fume to promote the formation and growth of well crystallized and highly adsorptive zeolites. Second, greater degrees of reaction at significantly lower temperatures are being promote by ball milling the fly ash prior to use, by the use of more concentrated caustic solutions, and by the addition of zeolite seeds to the reactants. In all cases studies will focus on the effect of structure type and degree of conversion on SO2 adsorption. Future work will concentrate on the study of the effect of weathering on the suitability of converting fly ash into zeolites. This is an especially important study, considering the acres of fly ash now in storage throughout the country.

  9. SO2 REMOVAL FROM FLUE GASES USING UTILITY SYNTHESIZED ZEOLITES

    SciTech Connect

    Michael Grutzeck

    1999-04-30

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

  10. Solvent-free syntheses of hierarchically porous aluminophosphate-based zeolites with AEL and AFI structures.

    PubMed

    Jin, Yinying; Chen, Xian; Sun, Qi; Sheng, Na; Liu, Yan; Bian, Chaoqun; Chen, Fang; Meng, Xiangju; Xiao, Feng-Shou

    2014-12-22

    Development of sustainable routes for synthesizing aluminophosphate-based zeolites are very important because of their wide applications. As a typical sustainable route, solvent-free synthesis of zeolites not only decreases polluted wastes but also increases product yields. Systematic solvent-free syntheses of hierarchically porous aluminophosphate-based zeolites with AEL and AFI structures is presented. XRD patterns and SEM images show that these samples have high crystallinity. N2 sorption isotherm tests show that these samples are hierarchically porous, and their surface areas are comparable with those of corresponding zeolites from hydrothermal route. Chosen as an example, catalytic oxidation of ethylbenzene with O2 shows that cobalt substituted APO-11 from the solvent-free route (S-CoAPO-11) is more active than conventional CoAPO-11 from hydrothermal route owing to the sample hierarchical porosity. PMID:25348837

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

    Microsoft Academic Search

    Jun-An Ke; Ikai Wang

    2001-01-01

    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

  12. Removal of Ammonium from Wastewater by Pure Form Low-Silica Zeolite Y Synthesized from Halloysite Mineral

    Microsoft Academic Search

    Yafei Zhao; Bing Zhang; Yanwu Zhang; Jinhua Wang; Jindun Liu; Rongfeng Chen

    2010-01-01

    Pure form, single phase, and highly crystalline low-silica zeolite Y was synthesized from natural nanotubular halloysite mineral by the hydrothermal method. In the synthesis process, the halloysite consisted of SiO2 and Al2O3 was used as starting material with adding supplementary silica and alumina sources. Ammonium adsorption properties of the as-synthesized zeolite Y were studied using batch experiments and the results

  13. Ni–Pt\\/H–Y Zeolite Catalysts for Disproportionation of Toluene and 1,2,4-trimethylbenzene

    Microsoft Academic Search

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

    2005-01-01

    Ni–Pt\\/H–Y zeolite catalysts with different Ni contents were prepared and applied to the disproportionation of toluene and 1,2,4-trimethylbenzene in the temperature range 250–400 °C. The line broadening XRD analysis indicates that the increasing Ni addition decreases the crystallinity of zeolites. ESCA studies show the complete reduction of Ni species up to 0.3 wt.% Ni addition over 0.1 wt.% Pt\\/H-Y and further

  14. Enhanced ion mobility in aluminosilicate/polysiloxane network polyelectrolytes

    SciTech Connect

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

    2000-07-01

    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.

  15. Quick Activation of Optimized Zeolites with Microwave Heating and Utilization of Zeolites for Reusable Desiccant

    Microsoft Academic Search

    Tatsuo Ohgushi; Mayumi Nagae

    2003-01-01

    Effectiveness of microwave heating in an activation treatment of zeolites was studied and utilization of zeolites for reusable desiccant was examined. X zeolite was chosen as a target material for its large adsorption capacity. Na-X zeolite easily caused a thermal runaway by microwave radiation of 500 W but Ca contained X zeolite merely reached ca. 573 K under the same

  16. Preparation and characterization of zinc aluminosilicate transparent glass-ceramics

    Microsoft Academic Search

    Hou Zhaoxia; Zhang Yongming; Zhang Hongbo; Su Chunhui

    2006-01-01

    Zinc aluminosilicate glosses containing Li2 O, ZnO, Al2O3 and SiO2 were prepared by conventional melting and quenching technique, and subsequently converted to transparent glass-ceramics by\\u000a controlled nucleation and crystallization. The glass was melted in a platinum crucible at 1 600 °C for 2 h and then two-step\\u000a heat treated for the nucleation and the crystal growth. The nucleation and crystallization

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

    Microsoft Academic Search

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

    2011-01-01

    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

  18. Microstructural aspects of zeolite formation in alkali activated cements containing high levels of fly ash

    Microsoft Academic Search

    A. A. Kruger; A. R. Brough; A. Katz; T. Bakharev; G. K. Sun; R. J. Kirkpatrick; L. J. Struble; J. F. Young

    1995-01-01

    Wasteforms made by reaction at elevated temperature of a highly e simulated low level nuclear waste solution, having high sodium ion concentration, with a cementitious blend high in fly ash have been studied. Significant formation of Na-P1 zeolite (gismondine framework) and of a sodalite occurred. The time evolution of the crystalline phases over the first 28 days is reported for

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

    DOEpatents

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

    1992-01-01

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

  20. Composition-solubility-structure relationships in calcium (alkali) aluminosilicate hydrate (C-(N,K-)A-S-H).

    PubMed

    Myers, Rupert J; L'Hôpital, Emilie; Provis, John L; Lothenbach, Barbara

    2015-07-21

    The interplay between the solubility, structure and chemical composition of calcium (alkali) aluminosilicate hydrate (C-(N,K-)A-S-H) equilibrated at 50 °C is investigated in this paper. The tobermorite-like C-(N,K-)A-S-H products are more crystalline in the presence of alkalis, and generally have larger basal spacings at lower Ca/Si ratios. Both Na and K are incorporated into the interlayer space of the C-(N,K-)A-S-H phases, with more alkali uptake observed at higher alkali and lower Ca content. No relationship between Al and alkali uptake is identified at the Al concentrations investigated (Al/Si ? 0.1). More stable C-(N,K-)A-S-H is formed at higher alkali content, but this factor is only significant in some samples with Ca/Si ratios ?1. Shorter chain lengths are formed at higher alkali and Ca content, and cross-linking between (alumino)silicate chains in the tobermorite-like structure is greatly promoted by increasing alkali and Al concentrations. The calculated solubility products do not depend greatly on the mean chain length in C-(N,K-)A-S-H at a constant Ca/(Al + Si) ratio, or the Al/Si ratio in C-(N,K-)A-S-H. These results are important for understanding the chemical stability of C-(N,K-)A-S-H, which is a key phase formed in the majority of cements and concretes used worldwide. PMID:26134354

  1. Inelastic neutron scattering from tetramethylammonium cations occluded within zeolites

    SciTech Connect

    Brun, T.O.; Curtiss, L.A.; Iton, L.E.; Kleb, R.; Newsam, J.M.; Beyerlein, R.A.; Vaughan, D.E.W.

    1987-06-24

    The use of organic bases, for example, tetraalklylammonium hydroxides, and other organic reagents has greatly enhanced the scope of gel/solution synthesis routes to crystalline microporous materials such as zeolites. The role of these organic components, however, continues to be the topic of considerable debate. The organic components first modify the gel structural chemistry. The presence of tetramethylammonium (TMA) hydroxide, for example, promotes the formation of double four-ring units in silicate solutions. Occlusion of organic gel components in zeolite crystal structures, however, leads also to the concept of a templating effect in which the organic component provides a basis around which the developing zeolite cages form. The mechanism of this templating process remains somewhat ill defined and must, at least, be of variable specificity. The authors describe here the use of inelastic neutron scattering (INS) to measure TMA template torsional vibrations, vibrations that provide to be sensitive to the strength of the interaction between the template cation and the enclosing zeolite cage.

  2. Zeolite modification II - direct fluorination

    Microsoft Academic Search

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

    1982-01-01

    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

  3. Thermal behavior of natural zeolites

    SciTech Connect

    Bish, D.L.

    1993-09-01

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

  4. Ruthenium on Beta Zeolite in Cinnamaldehyde Hydrogenation

    Microsoft Academic Search

    M. Lashdaf; M. Tiitta; T. Venäläinen; H. Österholm; A. O. I. Krause

    2004-01-01

    The behaviour of ruthenium was studied in relation to the acidity of beta zeolite. The impregnation of beta zeolite with ruthenium chloride decreased the crystallite size of beta zeolite. The acidity of the beta zeolite influenced the particle size of ruthenium. The particle size of ruthenium increased with decreasing acidity. Even catalysts with large particle size of ruthenium were selective

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

    PubMed

    Sprung, Christoph; Weckhuysen, Bert M

    2014-03-24

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

  6. Morphological control of silicalite-1 crystals using microemulsion mediated growth 

    E-print Network

    Lee, Seung Ju

    2005-11-01

    Zeolites are crystalline, microporous aluminosilicates that have been extensively used in heterogeneous catalysis, separations, and ion-exchange operations. It has long been understood that particle size and morphology ...

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

    NASA Technical Reports Server (NTRS)

    Ahlborg, Nadia L.; Zhu, Dongming

    2013-01-01

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

  8. Removal of radionuclides using zeolites

    SciTech Connect

    Reddy, R.G.; Cai, Z. [Univ. of Nevada, Reno, NV (United States)

    1996-10-01

    Adsorption of uranium(VI) from aqueous solutions on natural zeolites, i.e., chabazite, clinoptilolite, erionite and mordenite, was investigated. The influence of time and pH of the solution were studied. The results showed that uranium(VI) species are strongly adsorbed on the zeolites between pH 6 to 9. The amount of uranium adsorption is strongly dependent on pH and, to some extent, on the type of zeolites. For pH {ge} 6 and at 25 C, more than 92% of uranium from solution was removed in 10 minutes. Adsorption mechanism of uranium is discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

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

    SciTech Connect

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

    2006-08-21

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

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

    NASA Astrophysics Data System (ADS)

    Shamzhy, Mariya; Opanasenko, Maksym; Shvets, Oleksiy; ?ejka, Ji?í

    2013-08-01

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

  12. Copper-containing zeolite catalysts

    DOEpatents

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

    1996-01-01

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

  13. Copper-containing zeolite catalysts

    DOEpatents

    Price, G.L.; Kanazirev, V.

    1996-12-10

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

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

    NASA Astrophysics Data System (ADS)

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

    1983-03-01

    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.

  15. Brillouin scattering properties of lanthano-aluminosilicate optical fiber.

    PubMed

    Dragic, P D; Kucera, C; Ballato, J; Litzkendorf, D; Dellith, J; Schuster, K

    2014-09-01

    Utilizing measurements on a lanthano-aluminosilicate core optical fiber, the specific effects of lanthana (La2O3) on the Brillouin characteristics of silica-based oxide glass optical fibers are described. Lanthana is an interesting species to investigate since it possesses a wide transparency window covering the common fiber laser and telecom system wavelengths. As might be expected, it is found that the properties of lanthana are very similar to those of ytterbia (Yb2O3), namely, low acoustic velocity, wide Brillouin spectral width, and a negative photoelastic constant, with the latter two properties affording significant reductions to the Brillouin gain coefficient. However, lanthana possesses thermo-acoustic and strain-acoustic coefficients (acoustic velocity versus temperature or strain, TAC and SAC, respectively) with signs that are opposed to those of ytterbia. The lanthano-aluminosilicate (SAL) fiber utilized in this study is Brillouin-athermal (no dependence of the Brillouin frequency on temperature), but not atensic (is dependent upon the strain), which is believed to be, to the best of our knowledge, the first demonstration of such a glass fiber utilizing a compositional engineering approach. PMID:25321361

  16. Mechanism of Microwave Heating of Zeolite A

    Microsoft Academic Search

    Tatsuo Ohgushi; Sridhar Komarneni; Amar S. Bhalla

    2001-01-01

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

  17. Metal loading and reactivity of Zeolite

    E-print Network

    Sa?enz, Marc Gerard

    1988-01-01

    of experiments, increasing the amount of base increased the amount of cation deposited on the zeolite. In D'Aniello's experiments, increasing the amount of acid increased the amount of anion deposited on the alumina. However, alumina and zeolite Y... products with lower hydrogen to carbon atomic ratios. The zeolite based catalyst also exhibited a strong non-hydrogenative cracking function. The ability to control the ion exchange of zeolites by adjusting the pH of the exchanging slurry proved useful...

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

    PubMed

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

    2014-05-15

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

  19. Experimental proof for resonant diffusion of normal alkanes in LTL and ZSM-12 zeolites

    E-print Network

    Yoo, K; Smirniotis, P G

    2015-01-01

    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 resonant diffusion and several important parameters of the alkane-zeolite interaction and zeolite vibrations were obtained. In the considered temperature region the diffusion coefficient follows the Arrhenius law with periodic dependences of the pre-exponential factor and activation energy on the number of carbon atoms in alkanes. A compensation effect of simultaneous increases of the pre-exponential factor and the activation energy was also established.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    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.

  2. SODIUM ALUMINOSILICATE FOULING AND CLEANING OF DECONTAMINATED SALT SOLUTION COALESCERS

    SciTech Connect

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

    2008-10-28

    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.

  3. Bonding Preferences of Non-Bridging Oxygens in Calcium Aluminosilicate Glass: Evidence from O-17 MAS and 3QMAS NMR on Calcium Aluminate Glass

    NASA Astrophysics Data System (ADS)

    Allwardt, J. R.; Lee, S.; Stebbins, J.

    2001-12-01

    Non-bridging oxygens (NBO's) play a significant role in the thermodynamic and transport properties in glasses and silicate melts. Previous oxygen-17 (O-17) triple quantum magic angle spinning (3QMAS NMR) data have shown the presence of NBO's in several calcium aluminosilicate (CAS) glasses on the CaAl2O4-SiO2 join (Stebbins and Xu 1997). The observed chemical shifts of these glasses are similar to those for the NBO in calcium silicate glasses (Stebbins et al. 1997 and Stebbins et al 1999); however, a recent O-17 MAS NMR study of crystalline CaAl2O4 showed that the NBO peak in an associated impurity phase is shifted to a higher frequency by 30 to 40 ppm from that of CAS and Ca-silicate glasses (Stebbins et al. in press). This finding suggests that Si is the preferred network cation for NBO's in aluminosilicate glasses and melts at the glass transition temperature. The preference for Si over that of Al as the network cation host for NBO's has also been suggested by Raman and other spectroscopic techniques (Mysen 1988). To investigate this apparent preference for Si-NBO, O-17 3QMAS and MAS experiments were conducted to examine the location of the NBO peak in the spectra of a calcium aluminate glass. Since the CaAl2O4 glass is difficult to make by conventional cooling methods, the binary eutectic composition (63CaO-37Al2O3) was chosen. The resulting O-17 MAS spectrum shows an intense, relatively narrow peak centered at 72 ppm, which nearly coincides with the peak location and width of the Al-O-Al peak in the crystalline Ca-aluminates (Stebbins et al. in press.) (70 ppm). There is a broader, less intense peak centered at 155 ppm that is assigned to the Al-NBO peak. This peak is in approximately the same location as that for a Ca-aluminate phase reported by Stebbins et al. (in press) (137 ppm). In addition, our 3QMAS data show that the peak maximum of the NBO in the Ca-aluminate (-85 and 150 ppm in isotropic and MAS dimensions, respectively) differs significantly from that of the calcium aluminosilicates and Ca-silicates of Stebbins et al. (1997 and 1999) (approximately -61 and 95 ppm in isotropic and MAS dimensions, respectively). Our data, when combined with previous data on CAS and CS glasses, strongly suggests that most of the NBO's in calcium aluminosilicate glasses are bonded to Si, not Al.

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

    NASA Astrophysics Data System (ADS)

    Jeong, H. Y.; Lee, K.

    2013-12-01

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

  5. Organically modified aluminosilicate mesostructures from block copolymer phases

    PubMed

    Templin; Franck; Du Chesne A; Leist; Zhang; Ulrich; Schadler; Wiesner

    1997-12-01

    Organically modified aluminosilicate mesostructures were synthesized from two metal alkoxides with the use of poly(isoprene-b-ethyleneoxide) block copolymers (PI-b-PEO) as the structure-directing molecules. By increasing the fraction of the inorganic precursors with respect to the polymer, morphologies expected from the phase diagrams of diblock copolymers were obtained. The length scale of the microstructures and the state of alignment were varied using concepts known from the study of block copolymers. These results suggest that the use of higher molecular weight block copolymer mesophases instead of conventional low-molecular weight surfactants may provide a simple, easily controlled pathway for the preparation of various silica-type mesostructures that extends the accessible length scale of these structures by about an order of magnitude. PMID:9388181

  6. Suspending Zeolite Particles In Tanks

    SciTech Connect

    Poirier, M.R.

    1999-01-19

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

  7. Enhanced selectivity of zeolites by controlled carbon deposition

    DOEpatents

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

    2006-05-09

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

  8. STUDIES OF THE SURFACE CHARGE OF AMORPHOUS ALUMINOSILICATES USING SURFACE COMPLEXATION MODELS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Synthetic noncrystaline aluminosilicates with variable charge, similar to allophanes present naturally in volcanic soils, were studied. The surface charge behavior was determined by zero point charge (ZPC) measured by electrophoretic mobility (isoelectric points, IEP) and determined by potentiometr...

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

    PubMed

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

    2011-11-01

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

  10. Microscopic characterization of crystalline phases in waste forms

    SciTech Connect

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

    1995-07-01

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

  11. Hydrodewaxing with mixed zeolite catalysts

    SciTech Connect

    Chester, A.W.; McHale, W.D.; Yen, J.H.

    1986-03-11

    A process is described for catalytically dewaxing a hydrocarbon lubricating oil feedstock comprising contacting the feedstock with a dewaxing catalyst, the dewaxing catalyst comprising, in combination: (a) a zeolite catalyst having a Constraint Index not less than 1, (b) an acidic catalytic material selected from the group consisting of Mordenite, TEA Mordenite, Dealuminized Y, Ultrastable Y, Rare Earth Y, amorphous silica-alumina chlorinated alumina, ZSM-4 and ZSM-20, and (c) a hydrogenation component, and recovering a dewaxed product. A process is also described for catalytically dewaxing a hydrocarbon lubricating oil feedstock comprising contacting the feedstock with a dewaxing catalyst, the dewaxing catalyst comprising, in combinations: (a) a first zeolite catalyst selected from the group consisting of ZSM-5, ZMS-11, ZSM-12, ZSM-22, ZSM-23, ZSM-34, ZSM-35, ZSM-38, ZSM-48, TMA Offretite and Erionite, (b) a second catalyst selected from the group consisting of ZSM-12, ZSM-22, ZSM-38 and ZSM-48, the second zeolite catalyst being different from the first zeolite catalyst, and (c) a hydrogenation component, and recovering a dewaxed product.

  12. Zeolite Mineralogy and Cappadocian Erionite

    Microsoft Academic Search

    A. Umran Dogan

    2003-01-01

    The discovery some 30 years ago that erionite, a fibrous zeolite mineral, induced mesotheliomas in those living in certain villages in Cappadocia engendered a vast amount of both geological\\/mineralogical and clinical\\/epidemiological work. Studies initially concentrated on three villages where the incidence of this normally rare tumour correlated with the presence of erionite, and has extended to some new villages also

  13. Hydrogen Selective Exfoliated Zeolite Membranes

    SciTech Connect

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

    2014-09-30

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

  14. Resonant diffusion of normal alkanes in zeolites: Effect of the zeolite structure and alkane molecule vibrations

    E-print Network

    Tsekov, R

    2015-01-01

    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 varies periodically with the number of carbon atoms of the alkane molecule, a phenomenon called resonant diffusion. A criterion for observable resonance is obtained from the balance between the interaction potentials of the molecule due to the atomic and pore structures of the zeolite. It shows that the diffusion is not resonant in zeolites without pore structure, such as ZSM-12. Moreover, even in zeolites with developed pore structure no resonant dependence of the diffusion constant can be detected if the pore structure energy barriers are not at least three times high...

  15. Process for producing zeolite adsorbent and process for treating radioactive liquid waste with the zeolite adsorbent

    SciTech Connect

    Motojima, K.; Kawamura, F.

    1984-05-15

    Zeolite is contacted with an aqueous solution containing at least one of copper, nickel, cobalt, manganese and zinc salts, preferably copper and nickel salts, particularly preferably copper salt, in such a form as sulfate, nitrate, or chloride, thereby adsorbing the metal on the zeolite in its pores by ion exchange, then the zeolite is treated with a water-soluble ferrocyanide compound, for example, potassium ferrocyanide, thereby forming metal ferrocyanide on the zeolite in its pores. Then, the zeolite is subjected to ageing treatment, thereby producing a zeolite adsorbent impregnated with metal ferrocyanide in the pores of zeolite. The adsorbent can selectively recover cesium with a high percent cesium removal from a radioactive liquid waste containing at least radioactive cesium, for example, a radioactive liquid waste containing cesium and such coexisting ions as sodium, magnesium, calcium and carbonate ions at the same time at a high concentration. The zeolite adsorbent has a stable adsorbability for a prolonged time.

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

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2006-09-30

    The addition of hydrothermally-aged zeolite Y precursor to an SBA-15 synthesis mixture under a mildly acidic condition resulted in the formation of mesoporous aluminosilicate catalyst, Al-SBA-15, containing strong Broensted acid sites and aluminum (Al) stabilized in a totally tetrahedral coordination. The physicochemical characteristics of the catalyst varied as a function of the synthesis conditions. The catalyst possessed surface areas ranging between 690 and 850 m{sup 2}/g, pore sizes ranging from 5.6 to 7.5 nm, and pore volumes up 1.03 cm{sup 3}, which were comparable to the parent SBA-15 synthesized under similar conditions. Two wt% Al was present in the catalyst that was obtained from the reaction mixture that contained the highest Al content. The Al remained stable in totally tetrahedral coordination after calcination at 550 C. The Al-SBA-15 mesoporous catalyst showed significant catalytic activity for cumene dealkylation, and the activity increased as the amount of zeolite precursor added to the SBA-15 mixture was increased. In preparation for the final phase of the project, the catalyst was embedded into psuedoboemite alumina (catapal B) matrix and then formed into pellets. In the final phase of the project, the pelletized catalyst will be evaluated for the conversion of heavy petroleum feedstocks to naphtha and middle distillates.

  17. Zeolites for fixation of cesium and strontium from radwastes by thermal and hydrothermal treatments

    SciTech Connect

    Komarneni, S.; Roy, R.

    1981-01-01

    Several zeolites were heated in air up to 100/degree/C for 4 h or heated hydrothermally at 300/degree/C for 4 weeks under a confining pressure of 300 bar after loading with Cs or Sr to determine the extent and nature of Cs and Sr fixation. Cs-loaded zeolites leached with 0.1 N KCl solution indicated that clinoptilolite, chabazite, erionite, and mordenite fixed only 7% to 26% of their Cs after heat treatment up to 800/degree/C. However, analcite and phillipsite fixed 84% and 81% of their Cs by heat treatments to only 200 and 500/degree/C, respectively. The fixation in analcite may be attributed to its dehydration, while in phillipsite the fixation is attributed to its transformation to cesium aluminosilicate minerals. Analcite and phillipsite were also very effective in Sr fixation just as they were in Cs fixation. Analcite and phillipsite fixed 86% and 91% of their Sr by heat treatment to 420 and 600/degree/C, respectively. Phillipsite may be ideally suited for radioactive waste decontamination followed by thermal or hydrothermal treatment to fix the sorbed Cs and Sr. 17 refs.

  18. Hydrophobic high surface area zeolites derived from fly ash for oil spill remediation.

    PubMed

    Sakthivel, Tamilselvan; Reid, David L; Goldstein, Ian; Hench, Larry; Seal, Sudipta

    2013-06-01

    Fly ash, a coal combustion byproduct with a predominantly aluminosilicate composition, is modified to develop an inexpensive sorbent for oil spill remediation. The as-produced fly ash is a hydrophilic material with poor sorption capacity. A simple two-step chemical modification process is designed to improve the oil sorption capacity. First, the fly ash was transformed to a zeolitic material via an alkali treatment, which increased the specific surface area up to 404 m(2) g(-1). Then, the material was surface functionalized to form a hydrophobic material with high contact angle up to 147° that floats on the surface of an oil-water mixture. The reported oil sorption capacities of X-type zeolite sorbent with different surface functionalization (propyl-, octyl-, octadecyl-trimethoxysilane and esterification) were estimated to 1.10, 1.02, 0.86, and 1.15 g g(-1), respectively. Oil sorption was about five times higher than the as-received fly ash (0.19 g g(-1)) and also had high buoyancy critical for economic cleanup of oil over water. PMID:23634731

  19. Spin probes of chemistry in zeolites

    SciTech Connect

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

    1997-09-01

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

  20. Compressibility of the calcium aluminosilicate, CAS, phase to 44 GPa

    NASA Astrophysics Data System (ADS)

    Ono, Shigeaki; Iizuka, Tsuyoshi; Kikegawa, Takumi

    2005-06-01

    In situ X-ray diffraction measurements on a calcium aluminosilicate (CAS) phase have been carried out using a laser-heated diamond anvil cell up to a pressure of 44 GPa, employing a synchrotron radiation source. CAS is the major mineral formed from sediments subducted into the Earth's mantle. The sample was heated using a YAG laser after each pressure increment to relax the deviatoric stress in the sample. X-ray diffraction measurements were carried out at T = 300 K using an angle-dispersive technique. The pressure was calculated using an internal platinum metal pressure calibrant. The Birch-Murnaghan equation of state for the CAS phase obtained from the experimental unit cell parameters showed a density of ?0 = 3.888 g/cm 3 and a bulk modulus of K0 = 229 ± 9 GPa for K0 = 4.7 ± 0.7. When the first pressure derivative of the bulk modulus was fixed at K0 = 4, then the value of K0 = 239 ± 2 GPa. From the experimental compressibility, the density of the CAS phase was observed to be lower than the density of co-existing Al-bearing stishovite, calcium perovskite, calcium ferrite-type phases, and (Fe,Al)-bearing Mg-perovskite in subducted sediments in the lower mantle. Therefore, the density of subducted sediments in the lower mantle decreases with increasing mineral proportion of the CAS phase.

  1. Zeolite synthesis in hydrated silicate ionic liquids.

    PubMed

    van Tendeloo, Leen; Haouas, Mohamed; Martens, Johan A; Kirschhock, C E A; Breynaert, Eric; Taulelle, Francis

    2015-01-01

    Hydrated alkali silicate ionic liquids (HSIL) were prepared by hydrolysis of tetraethoxysilane (TEOS) in alkali hydroxide-water mixtures, inducing coacervation and phase separation. The resulting optically clear, homogenous silicate ionic liquid offers exceptional potential for monitoring zeolite crystallisation. This enhanced synthesis route provides access to analysis of speciation, mechanistic details of zeolite formation, and brings organic-template-free zeolite synthesis by design within reach. PMID:25886652

  2. Attempts to Synthesize Zeolitic Composites from Stellerite

    Microsoft Academic Search

    Ming Bo Yue; Li Huang; Xin Dong; Jia Hui Xu; Jian Hua Zhu

    2007-01-01

    A feasible method to synthesize NaA and NaY zeolite from stellerite, the very cheap raw material found in China, was reported in this article to reduce the cost of zeolite synthesis for the first time. After stellerite is calcined above 973 K with sodium carbonate, this natural zeolite can be slowly dissolved in alkali solution and partly forms the gels, then

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

    PubMed

    Sengupta, Pranesh; Fanara, Sara; Chakraborty, Sumit

    2011-06-15

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

  4. 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

    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

    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.

  5. Increased thermal conductivity monolithic zeolite structures

    DOEpatents

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

    2008-11-25

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

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

    SciTech Connect

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

    2007-01-01

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

  7. Crystalline inorganic frameworks with 56-ring, 64-ring, and 72-ring channels.

    PubMed

    Lin, Hsin-Yau; Chin, Chih-Yuan; Huang, Hui-Lin; Huang, Wen-Yen; Sie, Ming-Jhe; Huang, Li-Hsun; Lee, Yuan-Han; Lin, Chia-Her; Lii, Kwang-Hwa; Bu, Xianhui; Wang, Sue-Lein

    2013-02-15

    The development of zeolite-like structures with extra-large pores (>12-membered rings, 12R) has been sporadic and is currently at 30R. In general, templating via molecules leads to crystalline frameworks, whereas the use of organized assemblies that permit much larger pores produces noncrystalline frameworks. Synthetic methods that generate crystallinity from both discrete templates and organized assemblies represent a viable design strategy for developing crystalline porous inorganic frameworks spanning the micro and meso regimes. We show that by integrating templating mechanisms for both zeolites and mesoporous silica in a single system, the channel size for gallium zincophosphites can be systematically tuned from 24R and 28R to 40R, 48R, 56R, 64R, and 72R. Although the materials have low thermal stability and retain their templating agents, single-activator doping of Mn(2+) can create white-light photoluminescence. PMID:23348508

  8. Nanocrystalline Zeolites: Synthesis, Mechanism, and Applications

    NASA Astrophysics Data System (ADS)

    Severance, Michael Andrew

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

  9. Structure-Entropy Relationships in Aluminosilicate Garnets (Invited)

    NASA Astrophysics Data System (ADS)

    Geiger, C. A.; Dachs, E.

    2013-12-01

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

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

    Microsoft Academic Search

    J. de Oñate Martínez; C. Díaz Aguila; J. Fernández Bertrán; E. Reguera Ruíz; C. Portilla Vergara; R. Roque Malherbe

    1992-01-01

    The tribochemical reactions between Na-LTA and natural erionite with Fe2(SO4)3·5H2O were studied by Mössbauer 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.

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

    NASA Astrophysics Data System (ADS)

    de Oñate Martínez, J.; Aguila, C. Díaz; Bertrán, J. Fernández; Ruíz, E. Reguera; Vergara, C. Portilla; Malherbe, R. Roque

    1992-10-01

    The tribochemical reactions between Na-LTA and natural erionite with Fe2(SO4)3·5H2O were studied by Mössbauer 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.

  12. Electron density distributions and bonded interactions for the fibrous zeolites natrolite, mesolite and scolecite and related materials

    Microsoft Academic Search

    A. Kirfel; G. V. Gibbs

    2000-01-01

    For the fibrous zeolites natrolite, Na2[Al2Si3O10]·2H2O, mesolite, Na2Ca2[Al2Si3O10]3·8H2O, and scolecite, Ca[Al2Si3O10]·3H2O, with topologically identical aluminosilicate framework structures, accurate single-crystal X-ray diffraction data have\\u000a been analyzed by least-squares refinements using generalized scattering factor (GSF) models. The final agreement indices were\\u000a R(F?)?=?0.0061, 0.0165, and 0.0073, respectively. Ensuing calculations of static deformation [??(r)], and total, [?(r)], model electron density distributions served to study

  13. Influence of polyelectrolytes on crystallization of zeolite Y

    NASA Astrophysics Data System (ADS)

    Köro?lu, Hansu Jülide; Hande Öz, Pembe; Nusret Bulutçu, A.

    2012-09-01

    In this study, the influence of polyelectrolytes on the crystallization of zeolite Y is investigated. The prepared synthesis mixtures are aged at room temperature for 24 h and then left to crystallize. The compositional and structural information are provided by elemental analysis obtained by ICP, X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), particle size analyzer and adsorption and desorption isotherms of nitrogen by a volumetric adsorption instrument. The first group of synthesis studies is conducted by using solutions containing no additive (WA), nonionic (NI), 100% anionic (100A), and 100% cationic (100C) polyelectrolytes. The crystallization temperature and crystallization time are kept at 100 ºC and 48 h, respectively. The experimental results show that nonionic polyelectrolyte has the most influence on the crystallization of zeolite NaY. In the second group of synthesis studies, the effects of polyelectrolytes with various degrees of anionic properties (10%, 50% and 70%) of the same chemical structure are investigated by conducting crystallization experiments at 100 °C for a duration of 48 h. The results suggest that; particle size, crystallinity and BET surface area (SBET) can be controlled by adding anionic polyelectrolytes to the solution.

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

    PubMed

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

    2012-04-01

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

  15. Li+ alumino-silicate ion source development for the neutralized drift compression experiment.

    PubMed

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

    2011-01-01

    We report results on lithium alumino-silicate ion source development in preparation for warm dense matter heating experiments on the new neutralized drift compression experiment II. The practical limit to the current density for a lithium alumino-silicate source is determined by the maximum operating temperature that the ion source can withstand before running into problems of heat transfer, melting of the alumino-silicate material, and emission lifetime. Using small prototype emitters, at a temperature of ?1275 °C, a space-charge limited Li(+) beam current density of J ?1 mA/cm(2) was obtained. The lifetime of the ion source was ?50 h while pulsing at a rate of 0.033 Hz with a pulse duration of 5-6 ?s. PMID:21280822

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

    PubMed

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

    2012-04-01

    A space-charge-limited beam with current densities (J) exceeding 1 mA/cm(2) have been measured from lithium alumino-silicate ion sources at a temperature of ?1275 °C. At higher extraction voltages, the source appears to become emission limited with J ? 1.5 mA/cm(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 ?40 h at ?1275 °C, when pulsed at 0.05 Hz and with pulse length of ?6 ?s each. At this rate, the source lifetime was independent of the actual beam charge extracted due to the loss of neutral atoms at high temperature. 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. PMID:22559528

  17. 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)

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

    2006-12-01

    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 7.6±1.9 to 9.4±2.4 and the percentage of NBO per total oxygen increases from 7.2±1.8 to 8.9±2.2 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 4.0±1.0 to 4.9±1.2 and the percentage of non-bridging oxygen (NBO) per total oxygen increases from 22.8±2.3 to 23.0±2.3. 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.

  18. Metal/zeolite catalysts of methane dehydroaromatization

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  19. Selective anisotropic growth of zeolite crystals

    E-print Network

    Desai, Tasha April

    2013-02-22

    . To achieve this end we are attempting to grow zeolite particles in the confined water spaces formed in water/surfactant systems, using these "nanoreactors" to modulate zeolite growth. Our work to date has focused on the synthesis of two-dimensional (5x100x...

  20. The flexibility of zeolites for Hydrogen storage

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

    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.

  1. Cracking of naphtha range alkanes and naphthenes over zeolites

    Microsoft Academic Search

    Hayim Abrevaya

    2007-01-01

    Naphtha range alkanes and naphthenes can be activated over H-form of zeolites, which provide low temperature cracking pathways that are otherwise unavailable during conventional steam cracking. A range of zeolitic catalysts were tested for cracking naphtha. Due to their relatively larger kinetic diameter, isoalkanes and naphthenes exhibited lower reactivity than linear alkanes over 8-MR zeolites. 12-MR zeolites favored bimolecular hydride

  2. Orthogonal Experiment of Modified Zeolite for Wastewater Treatment

    Microsoft Academic Search

    Zuo Jinlong

    2010-01-01

    In order to improve ammonia removal capability from wastewater, zeolite was modified in this paper. Some results for virgin zeolite were revealed by SEM, and its structure showed some ions such NH4+ enter into the pore way in the zeolite. The best results could be attained by combined modification with orthogonal experiment. The adsorption capacity of modified zeolite could be

  3. Thermal degradation of epoxy\\/natural zeolite composites

    Microsoft Academic Search

    Jae-Young Lee; Mi-Ja Shim; Sang-Wook Kim

    2001-01-01

    The characteristics of thermal degradation of epoxy system filled with natural zeolite were studied by thermogravimetry analysis (TGA). All the epoxy composites were degraded in one stage regardless of the zeolite content. In the Freeman & Carroll equation, the activation energy at 20 phr of zeolite was lower than that at any other content of zeolite and these values decreased

  4. Zeolitic materials with hierarchical porous structures.

    PubMed

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

    2011-06-17

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

  5. Nitric oxide adsorbed on zeolites: EPR studies

    NASA Astrophysics Data System (ADS)

    Yahiro, Hidenori; Lund, Anders; Shiotani, Masaru

    2004-05-01

    CW-EPR studies of NO adsorbed on sodium ion-exchanged zeolites were focused on the geometrical structure of NO monoradical and (NO) 2 biradical formed on zeolites. The EPR spectrum of NO monoradical adsorbed on zeolite can be characterized by the three different g-tensor components and the resolved y-component hyperfine coupling with the 14N nucleus. Among the g-tensor components, the value of g zz is very sensitive to the local environment of zeolite and becomes a measure of the electrostatic field in zeolite. The temperature dependence of the g-tensor demonstrated the presence of two states of the Na-NO adduct, in rigid and rotational states. The EPR spectra of NO adsorbed on alkaline metal ion-exchanged zeolite and their temperature dependency are essentially the same as that on sodium ion-exchanged zeolite. On the other hand, for NO adsorbed on copper ion-exchanged zeolite it is known that the magnetic interaction between NO molecule and paramagnetic copper ion are observable in the spectra recorded at low temperature. The signals assigned to (NO) 2 biradical were detected for EPR spectrum of NO adsorbed on Na-LTA. CW-EPR spectra as well as their theoretical calculation suggested that the two NO molecules are aligned along their N?O bond axes. A new procedure for automatical EPR simulation is described which makes it possible to analyze EPR spectrum easily. In the last part of this paper, some instances when other nitrogen oxides were used as a probe molecule to characterize the zeolite structure, chemical properties of zeolites, and dynamics of small molecules were described on the basis of selected literature data reported recently.

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

    Microsoft Academic Search

    Thomas Bein; Peter A. Jacobs

    1983-01-01

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

  7. Preparation and mechanical behaviour of some chemically strengthened lithium magnesium alumino-silicate glasses

    Microsoft Academic Search

    I. W. Donald; M. J. C. Hill

    1988-01-01

    Chemically strengthened lithium magnesium alumino-silicate glasses have been prepared by ion-exchange in sodium nitrate at 385° C, and the stress profiles of the resultant materials have been measured using the scattered light and etching technique. Unusual stress profiles have been obtained for some of the materials, with the outermost layers of the surface being in tension, rather than compression. This

  8. EFFECT OF IMPURITIES ASSOCIATED WITH ALUMINOSILICATES ON ARSENIC SORPTION AND OXIDATION

    EPA Science Inventory

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

  9. Aluminosilicate and borosilicate single 4-rings: Effects of counterions and water on structure, stability, and spectra

    Microsoft Academic Search

    J. A. Tossell; G. Saghi-Szabo

    1997-01-01

    Rings containing four tetrahedrally coordinated atoms connected by bridging O atoms in a single four ring (S4R) geometry have been used to model the properties of ring species occurring in aluminosilicate and borosilicate crystals, glasses, and melts. We recently established a molecular basis for the Al avoidance, or “Loewenstein's rule,” using molecular quantum mechanical methods applied to the non-Loewenstein paired,

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

    Microsoft Academic Search

    Amparo Borrell; Olga García-Moreno; Ramón Torrecillas; Victoria García-Rocha; Adolfo Fernández

    2012-01-01

    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

  11. Photoinduced electron transfer reactions in zeolite cages

    SciTech Connect

    Dutta, P.K.

    1992-01-01

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

  12. Modified 8-ring zeolites as catalysts

    SciTech Connect

    Bergna, H.E.; Corbin, D.R.; Sonnichsen, G.C.

    1988-06-21

    A catalyst composition is described for conversion of methanol and/or dimethylether and ammonia to dimethylamine, comprising at least one modified acidic zeolite selected from the group consisting of chabazite erionite, ZK-5, and rho, the zeolite having been modified by treatment with one or more compounds containing at least one element selected from the group consisting of silicon, aluminum, phosphorus, and boron, to deposit substantially on the external surfaces thereof at least 0.5 weight percent of the element.

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

  14. Kinetics of zeolite dealumination in steam

    SciTech Connect

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

    1998-08-01

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

  15. Three Mile Island zeolite vitirification demonstration program

    SciTech Connect

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

    1981-06-01

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

  16. Thermodynamic modeling of natural zeolite stability

    SciTech Connect

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

    1997-06-01

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

  17. Zeolites: Structural Properties and Benchmarks of Feasibility

    NASA Astrophysics Data System (ADS)

    Dawson, Colby

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

  18. Microstructural aspects of zeolite formation in alkali activated cements containing high levels of fly ash

    SciTech Connect

    Kruger, A.A. [Westinghouse Hanford Co., Richland, WA (United States); Brough, A.R.; Katz, A.; Bakharev, T.; Sun, G.K.; Kirkpatrick, R.J.; Struble, L.J.; Young, J.F. [Univ. of Illinois, Urbana, IL (United States). Center for Advanced Cement Based Materials

    1995-02-01

    Wasteforms made by reaction at elevated temperature of a highly e simulated low level nuclear waste solution, having high sodium ion concentration, with a cementitious blend high in fly ash have been studied. Significant formation of Na-P1 zeolite (gismondine framework) and of a sodalite occurred. The time evolution of the crystalline phases over the first 28 days is reported for both adiabatic and isothermal curing, and the role of these phases in microstructure development is discussed. The level of carbonate ions in solution was found to have a substantial effect on strength evolution and chemistry.

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

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2007-03-31

    The addition of hydrothermally-aged zeolite Y precursor to an SBA-15 synthesis mixture under a mildly acidic condition resulted in the formation of a mesoporous aluminosilicate catalyst, AlSBA-15. The Al-SBA-15 mesoporous catalyst contains strong Br{umlt o}nsted acid sites and aluminum (Al) stabilized in a totally tetrahedral coordination. The physicochemical characteristics of the catalyst varied as a function of the synthesis conditions. The catalyst possessed surface areas ranging between 690 and 850 m{sup 2}/g, pore sizes ranging from 5.6 to 7.5 nm, and pore volumes up 1.03 cm{sup 3}, which were comparable to the parent SBA-15 synthesized under similar conditions. Two wt % Al was present in the catalyst that was obtained from the reaction mixture that contained the highest Al content. The Al remained stable in totally tetrahedral coordination after calcination at a temperature of 550 C. The Al-SBA-15 mesoporous catalyst showed significant catalytic activity for cumene dealkylation, and the activity increased as the amount of zeolite precursor added to the SBA-15 mixture was increased. In preparation for the final phase of the project, the catalyst was embedded into a psuedoboemite alumina (catapal B) matrix and then formed into pellets. In the final phase of the project, the pelletized catalyst is being evaluated for the conversion of a heavy petroleum feedstock to naphtha and middle distillates. This phase was significantly delayed during the past six months due to a serious malfunction of the fume hoods in the Clark Atlanta University's Research Center for Science and Technology, where the project is being conducted. The fume hood system was repaired and the catalyst evaluation is now underway.

  20. Studies of the surface charge of amorphous aluminosilicates using surface complexation models.

    PubMed

    Jara, Alejandra A; Goldberg, Sabine; Mora, M L

    2005-12-01

    Synthetic noncrystalline aluminosilicates with variable charge, similar to allophanes present naturally in volcanic soils, were studied. The surface charge behavior was determined by zero point charge (ZPC) measured by electrophoretic mobility (isoelectric points, IEP) and determined by potentiometric titration (point of zero salt effect, PZSE). The ZPC calculated by Parks model (ZPC(c)), compared with IEP values, showed that the aluminosilicate (AlSi) surface was slightly enriched by AlOH (34% Al(2)O(3) and 66% SiO(2)) compared with the bulk composition (29% Al(2)O(3) and 71% SiO(2)). For aluminosilicate coated with iron oxide (AlSiFe) the ZPC(c) (4.4) was lower than the IEP (8.46), showing that the surface composition is formed mainly from iron oxide. The PZSE values for AlSi and AlSiFe were 6.2 and 4.8, respectively. The differences between the IEP and PZSE are attributed to the formation of Si-O-Fe or Si-O-Al bonds; therefore, the reactivity of Fe and Al atoms was modified on the surface. Two mechanistic models, the constant capacitance model (CCM) and the triple layer model (TLM), using the program FITEQL 3.2 were able to describe the surface behavior of both synthetic aluminosilicates. The acidity constants determined using both models for the aluminosilicates showed differences with respect to pure oxide, mainly attributed to the presence of SiOH sites on the internal surfaces. The ionic strength showed a good relation with the parameters obtained using the CCM (pK(int)(a1), pK(int)(a2) and capacitance values) and the TLM (pK(int)(a1), pK(int)(a2), pK(int)(Cl-), pK(int)(K+), and inner capacitance) for both aluminosilicates. However, the TLM was able to describe the acidity and complexation constants better since it considered the formation of the outer sphere complex between the background electrolyte and the surface. Then, the TLM makes it possible to describe real systems. PMID:16051258

  1. Effects of aluminosilicate minerals in clay soil fractions on pore water hydroxide ion concentrations in soil/cement matrices 

    E-print Network

    Cook, Evan Russell

    1998-01-01

    between clay minerals and calcium hydroxide. Pozzolanic reactions between aluminosilicate minerals in soils and portiandite or calcium silicate hydrate, generated by cement hydration, may significantly reduce the hydroxide ion concentration in soi...

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

    Microsoft Academic Search

    Farouq A. Twaiq; Abdul Rahman Mohamed; Subhash Bhatia

    2003-01-01

    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 (sol–gel and hydrothermal) and post-synthesis (ion-exchange and grafting) methods. The synthesized

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

    Microsoft Academic Search

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

    2008-01-01

    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

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

    NASA Technical Reports Server (NTRS)

    Hurwitz, Frances I.; Guo, Haiquan; Newlin, Katy N.

    2011-01-01

    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 morphology, pore size distribution, physical and skeletal densities. The present study focuses on the synthesis of aluminosilicate aerogel from a variety of Boehmite (precursors as the Al source, and tetraethylorthosilicate (TEOS) as the Si source, and the influence of starting powder on pore structure and thermal stability.

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

    SciTech Connect

    Corma, A.; Iborra, S.; Miquel, S.; Primo, J. [Instituto de Tecnologia Quimica, Valencia (Spain)] [Instituto de Tecnologia Quimica, Valencia (Spain)

    1996-07-01

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

  6. Branched vs. linear hydrocarbon separations with novel modified zeolites.

    SciTech Connect

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

    2004-08-01

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

  7. Branched vs. linear hydrocarbon separations with novel modified zeolites.

    SciTech Connect

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

    2005-06-01

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

  8. Separation of xylene mixtures using polyurethane—zeolite composite membranes

    Microsoft Academic Search

    Shingjiang Jessie Lue; Tsai-hsin Liaw

    2006-01-01

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

  9. Femtosecond laser direct writing of embedded optical waveguides in aluminosilicate glass

    NASA Astrophysics Data System (ADS)

    Low, D. K. Y.; Xie, H.; Xiong, Z.; Lim, G. C.

    2005-12-01

    Using tightly focused femtosecond laser pulses to irradiate lines in aluminosilicate glass, embedded lines with increased refractive index, which function as optical waveguides were observed. The pulse energy (4.5 11.2 ?J) and writing speed (50 700 ?m/s) were shown to affect the resultant optical properties of the waveguides such as the magnitude of refractive index change, core diameter and propagation mode. At pulse energies above 5 ?J, two types of structures were observed, namely an inhomogeneous void-like structure and a cross-sectional crack-like structure. These structures were found to affect significantly the resultant waveguiding properties of the irradiated lines. Using pulse energy of 5 ?J or below, single mode waveguides were fabricated. Raman spectroscopy showed that the fs laser pulses generated structural changes to the aluminosilicate glass. The fabrication of a 1×4 splitter was also demonstrated.

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

    PubMed

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

    2014-03-15

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

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

    SciTech Connect

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

    2008-07-15

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

  12. Magnetic and Mössbauer study of metal-zeolite interaction in catalysts

    NASA Astrophysics Data System (ADS)

    Pannaparayil, Thomas; Oskooie-Tabrizi, M.; Lo, C.; Mulay, L. N.; Melson, G. A.; Rao, V. U. S.

    1984-03-01

    Molecular sieve aluminosilicates, such as ZSM-5 and mordenite, when impregnated with highly dispersed Fe, yield catalysts for the selective conversion of coal-derived syngas (CO+H2) to liquid hydrocarbon fuels. Fe performs the primary Fischer-Tropsch (FT) syngas to yield light olefins which are converted by the acidic (H+) and shape-selective function of the zeolite to high octane gasoline components. The physical aspects of the Fe-mordenite interaction studied by magnetic measurements, Mössbauer, and IR spectroscopy are reported and correlations with the catalytic properties are drawn. Mordenite samples with [SiO2/Al2O3] ratio in the range 12 - 60 were impregnated with 15 wt. % Fe using Fe3(CO)12; decarbonylation yielded superparamagmetic dispersions of ?-Fe2O3, in the range 1.4-5.0 nm; the smallest particles were obtained for a ratio=17. Hydrogen chemisorption also revealed a similar trend in Fe dispersions. No samples, other than the one with a ratio=60 and containing the largest particles could be carbided under usual conditions. The acidity of the mordenite and the aromatics fraction in liquid hydrocarbons from syngas conversion also showed maxima at a ratio=17. The presence of a strong metal-support interaction between Fe and mordenite was thus influenced by the varying ratios in the mordenite in a manner that paralleled the acidity and catalytic activity.

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

    PubMed

    Ruda, Toni A; Dutta, Prabir K

    2005-08-15

    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

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

    Microsoft Academic Search

    Jonathan Tailby; Kenneth J. D. MacKenzie

    2010-01-01

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

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

    PubMed

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

    2005-08-15

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

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

    Microsoft Academic Search

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

    2008-01-01

    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

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

    SciTech Connect

    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

    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.

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

    Microsoft Academic Search

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

    2007-01-01

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

  19. Durability of Zeolite Against Repeated Activation Treatments with Microwave Heating

    Microsoft Academic Search

    Tatsuo Ohgushi; Mayumi Nagae

    2005-01-01

    The durability of zeolite X against repeated treatments with microwave heating was studied, and properties of the zeolite as desiccant were compared and assessed with those of the most popular commercial desiccants (calcium chloride) for home use. Mixed cationic forms of zeolite with a ratio of Na-X\\/Ca-X = 5 g\\/45 g in a full hydration was used to achieve desirable

  20. New vistas in zeolite and molecular sieve catalysis

    Microsoft Academic Search

    Mark E. Davis

    1993-01-01

    There is a close connection between the microscopic structures and the macroscopic properties of zeolite catalysts. The ability to control the zeolite properties through synthetic efforts will continue to be of great importance. At present, the control of zeolite properties mainly involves molecular level manipulations of structural features, e.g., pore size and location of active sites. That is to say,

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

    NASA Astrophysics Data System (ADS)

    Stoeger, Jared Andrew

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

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

    Microsoft Academic Search

    Hidekazu Tanaka; Yasuhiko Sakai; Ryozi Hino

    2002-01-01

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

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

    SciTech Connect

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

    2012-02-10

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

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

    SciTech Connect

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

    2012-03-05

    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.

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

    NASA Astrophysics Data System (ADS)

    Yang, Dongjiang; Xu, Yao; Wu, Dong; Sun, Yuhan

    2008-09-01

    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 °C distilled water for 300 h. The boiled mesoporous aluminosilicates have nearly the same N 2 adsorption-desorption isotherms and the same pore size distributions as those newly synthesized ones, indicating excellent hydrothermal stability. The 29Si MAS NMR spectra confirmed that PMHS and TEOS have jointly condensed and CH 3 groups have been introduced into the materials. The 27Al MAS NMR spectra indicated that Al atoms have been incorporated in the mesopore frameworks. The NH 3 temperature-programmed desorption showed strong acidity. Due to the existence of large amount of CH 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.

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

    SciTech Connect

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

    2008-02-27

    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.

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

    PubMed Central

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

    2011-01-01

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

  8. Topological crystalline insulator nanostructures.

    PubMed

    Shen, Jie; Cha, Judy J

    2014-11-01

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

  9. Role of high-resolution electron microscopy in the identification and characterization of new crystalline, microporous materials: Reading off the structure and symmetry elements of pentasil molecular sieves

    Microsoft Academic Search

    Osamu Terasaki; John M. Thomas; G. Robert Millward; D. Watanabe

    1989-01-01

    The advantages of establishing the structure of new microporous, crystalline solids such as zeolites, porosils, and aluminum phosphates by using high-resolution electron microscopy are assessed and illustrated with reference to ZSM-5. In particular, it is shown that the structure and symmetry elements of this member of the pentasil family may, by comparison of computed and observed (at 200 and 1000

  10. Determination of trace elements in zeolites by laser ablation ICP-MS.

    PubMed

    Pickhardt, C; Brenner, I B; Becker, J S; Dietze, H J

    2000-09-01

    Laser ablation inductively coupled plasma mass spectrometry using a quadrupole-based mass spectrometer (LA-ICP-QMS) was applied for the analysis of powdered zeolites (microporous aluminosilicates) used for clean-up procedures. For the quantitative determination of trace element concentrations three geological reference materials, granite NIM-G, lujavrite NIM-L and syenite NIM-S, from the National Institute for Metallurgy (South Africa) with a matrix composition corresponding to the zeolites were employed. Both the zeolites and reference materials were fused with a lithium borate mixture to increase the homogeneity and to eliminate mineralogical effects. In order to compare two different approaches for the quantification of analytical results in LA-ICP-MS relative sensitivity coefficients (RSCs) of chemical elements and calibration curves were measured using the geostandards. The experimentally obtained RSCs are in the range of 0.2-6 for all elements of interest. Calibration curves for trace elements were measured without and with Li or Ti as internal standard element. With a few exceptions the regression coefficients of the calibration curves are better than 0.993 with internal standardization. NIM-G granite reference material was employed to evaluate the accuracy of the technique. Therefore, the measured concentrations were corrected with RSCs which were determined using lujavrite reference material NIM-L. This quantification method provided analytical results with deviations of 1-11% from the recommended and proposed values in granite reference material NIM-G, except for Co, Cs, La and Tb. The relative standard deviation (RSD) of the determination of the trace element concentration (n = 5) is about 1% to 6% using Ti as internal standard element. Detection limits of LA-ICP-QMS in the lower microg/g range (from 0.03 microg/g for Lu, Ta and Th to 7.3 microg/g for Cu, with the exception of La) have been achieved for all elements of interest. Under the laser ablation conditions employed (lambda: 266 nm, repetition frequency: 10 Hz, pulse energy: 10 mJ, laser power density: 6 x 10(9) W/cm2) fractionation effects of the determined elements relative to the internal standard element Ti were not observed. PMID:11220836

  11. Chemical evaluation of hypothetical uninodal zeolites.

    PubMed

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

    2004-08-11

    Optimized structural parameters, framework energies relative to alpha-quartz, and volumes accessible to sorption have been calculated for the systematically enumerated hypothetical uninodal zeolitic structures (structures in which all tetrahedral sites are equivalent). The structures were treated as silica polymorphs, and their energies were minimized using the GULP program with the Sanders-Catlow silica potential. Results are given for 164 structures, which include all 21 known uninodal zeolites, two known minerals (tridymite and cristobalite), and 78 unknown zeolite topologies. Twenty-three hypothetical structures were identified as chemically feasible. Complete structural information is provided, and several structures are discussed in detail. The results will assist in the design of new synthetic routes and in the identification of newly synthesized materials. PMID:15291580

  12. Triamterene crystalline nephropathy.

    PubMed

    Nasr, Samih H; Milliner, Dawn S; Wooldridge, Thomas D; Sethi, Sanjeev

    2014-01-01

    Medications can cause a tubulointerstitial insult leading to acute kidney injury through multiple mechanisms. Acute tubular injury, a dose-dependent process, occurs due to direct toxicity on tubular cells. Acute interstitial nephritis characterized by interstitial inflammation and tubulitis develops from drugs that incite an allergic reaction. Other less common mechanisms include osmotic nephrosis and crystalline nephropathy. The latter complication is rare but has been associated with several drugs, such as sulfadiazine, indinavir, methotrexate, and ciprofloxacin. Triamterene crystalline nephropathy has been reported only rarely, and its histologic characteristics are not well characterized. We report 2 cases of triamterene crystalline nephropathy, one of which initially was misdiagnosed as 2,8-dihydroxyadenine crystalline nephropathy. PMID:23958399

  13. Studies of anions sorption on natural zeolites.

    PubMed

    Barczyk, K; Mozgawa, W; Król, M

    2014-12-10

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

  14. Crystal engineering of zeolites with graphene

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

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

    SciTech Connect

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

    2010-12-15

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

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

    PubMed

    Valdés, Héctor; Alejandro, Serguei; Zaror, Claudio A

    2012-08-15

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

  17. Tribochemical reactions of erionite and Na-LTA zeolites with Fe 2 (SO 4 ) 3 .5H 2 O: A mössbauer study

    Microsoft Academic Search

    J. de Oñate Martínez; C. Díaz Aguila; J. Fernández Bertrán; E. Reguera Ruíz; C. Portilla Vergara; R. Roque Malherbe

    1992-01-01

    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\\u000a compound, a product of the extracted aluminum and the sulfate.

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

    PubMed

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

    2014-01-01

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

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

    SciTech Connect

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

    2008-10-28

    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.

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

    NASA Astrophysics Data System (ADS)

    Tossell, J. A.

    1995-04-01

    13C 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 3TOT'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 3SiOSiH 3 is quite weakly bonded and its 13C 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 13C NMR shieldings decrease uniformly. The calculated 13C shielding value for H 3AlO(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 3SiO(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) 3SiO(CO 2)Al(OH) 3-1, the calculated 13C 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 13C 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 3AlO(CO 2)AlH 3-2 complexes reduces the 13C NMR shieldings by about 10 ppm. Complexation with either Na + or CO 2 also reduces the 29Si NMR shieldings of the aluminosilicate models, while the changes in 27Al 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 3AlOAlH 3-2, raising it to a value similar to that found for Si?O?Si linkages. Comparison of these results with the experimental 13C 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.

  1. Chemical interactions in multimetal/zeolite catalysts

    SciTech Connect

    Sachtler, W.M.H.

    1992-02-07

    Mechanistic explanations have been found for the migration of atoms and ions through the zeolite channels leading to specific distribution of ions and the metal clusters. In this report, we summarize the state of understanding attained on a number of topics in the area of mono- and multimetal/zeolite systems, to which our recent research has made significant contributions. The following topics are discussed: (1) Formation of isolated metal atoms in sodalite cages; (2) differences of metal/zeolite systems prepared by ion reduction in channels or via isolated atoms; (3) rejuvenation of Pd/NaY and Pd/HY catalysts by oxidative redispersion of the metal; (4) formation of mono- or bimetal particles in zeolites by programmed reductive decomposition of volatile metal complexes; (5) cation-cation interaction as a cause of enhanced reducibility; (6) formation of palladium carbonyl clusters in supercages; (7) enhanced catalytic activity of metal particle-proton complexes for hydrocarbon conversion reactions; (8) stereoselectivity of catalytic reactions due to geometric constraints of particles in cages.

  2. MERCURY SEPARATION FROM POLLUTANT WATER USING ZEOLITES

    EPA Science Inventory

    Arsenic is known to be a hazardous contaminant in drinking water that causes arsenical dermatitis and skin cancer. In the present work, the potential use of a variety of synthetic zeolites for removal of arsenic from water has been examined at room temperature. Experiments have...

  3. Silver clusters and chemistry in zeolites

    Microsoft Academic Search

    Tao Sun; Karl Seff

    1994-01-01

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

  4. Silver clusters and chemistry in zeolites

    SciTech Connect

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

    1994-06-01

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

  5. Conversion of Ethanol to Hydrocarbons on Hierarchical HZSM-5 Zeolites

    SciTech Connect

    Ramasamy, Karthikeyan K.; Zhang, He; Sun, Junming; Wang, Yong

    2014-12-15

    This study reports synthesis, characterization, and catalytic activity of the nano-size hierarchical HZSM-5 zeolite with high mesoporosity produced via a solvent evaporation procedure. Further, this study compares hierarchical zeolites with conventional HZSM-5 zeolite with similar Si/Al ratios for the ethanol-to-hydrocarbon conversion process. The catalytic performance of the hierarchical and conventional zeolites was evaluated using a fixed-bed reactor at 360 °C, 300 psig, and a weight hourly space velocity of 7.9 h-1. For the low Si/Al ratio zeolite (~40), the catalytic life-time for the hierarchical HZSM-5 was approximately 2 times greater than the conventional HZSM-5 despite its coking amount deposited 1.6 times higher than conventional HZSM-5. For the high Si/Al ratio zeolite (~140), the catalytic life-time for the hierarchical zeolite was approximately 5 times greater than the conventional zeolite and the amount of coking deposited was 2.1 times higher. Correlation was observed between catalyst life time, porosity, and the crystal size of the zeolite. The nano-size hierarchical HZSM-5 zeolites containing mesoporosity demonstrated improved catalyst life-time compared to the conventional catalyst due to faster removal of products, shorter diffusion path length, and the migration of the coke deposits to the external surface from the pore structure.

  6. (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

    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

    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.

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

    NASA Astrophysics Data System (ADS)

    Thompson, L.; Stebbins, J.

    2008-12-01

    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).

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

    SciTech Connect

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

    2011-07-21

    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.

  9. Direct (17)O NMR experimental evidence for Al-NBO bonds in Si-rich and highly polymerized aluminosilicate glasses.

    PubMed

    Jaworski, Aleksander; Stevensson, Baltzar; Edén, Mattias

    2015-07-01

    By using solid-state (17)O NMR spectroscopy, we provide the first direct experimental evidence for bonds between Al and non-bridging oxygen (NBO) ions in aluminosilicate glasses based on rare-earth (RE) elements, where RE = {Lu, Sc, Y}. The presence of ?10% Al-NBO moieties out of all NBO species holds regardless of the precise glass composition, at odds with the conventional structural view that Al-NBO bonds are absent in highly polymerized and Si-rich aluminosilicate glass networks. PMID:26118845

  10. Interaction of Microwaves with Synthetic Type A Zeolite Containing Water

    NASA Astrophysics Data System (ADS)

    Tanaka, Masahiro; Takayama, Sadatsugu; Sano, Saburo

    2013-11-01

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

  11. Zeolite and swine inoculum effect on poultry manure biomethanation

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  12. Zeolite catalysis in conversion of cellulosics. Annual report

    SciTech Connect

    Tsao, G.T.

    1994-02-01

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

  13. Advanced zeolites used in FCC catalysts boost motor octane number

    SciTech Connect

    Letzsch, W.S.; Magee, J.S.; Upson, L.L.; Valeri, F. (Katalistiks International, Baltimore, MD (US))

    1988-10-31

    Fluid catalytic cracking catalysts that contain an advanced zeolite called LZ-210, have been shown, by commercial trials, to increase the motor octane number (MON) of the FCC gasoline produced. The zeolite crystal utilizes lower unit cell size, lower sodium in the zeolite, less alumina debris in the zeolite structure, and silica reinsertion into the zeolite structure to accomplish the MON increase. Data from commercial trials are presented to support the MON increases, along with some explanations of how the advanced zeolite accomplishes them. A strong gasoline market and the removal of lead have combined to place a premium on clear gasoline octanes. Because gasoline from fluid catalytic cracking units is the largest segment of the refinery pool (up to 40%), its octane numbers are particularly important. Traditional emphasis has been on the research octance number (RON) but motor octanes frequently limit the blending process.

  14. Atomic sites and stability of Cs+ captured within zeolitic nanocavities

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    Zeolites have potential application as ion-exchangers, catalysts and molecular sieves. Zeolites are once again drawing attention in Japan as stable adsorbents and solidification materials of fission products, such as 137Cs+ from damaged nuclear-power plants. Although there is a long history of scientific studies on the crystal structures and ion-exchange properties of zeolites for practical application, there are still open questions, at the atomic-level, on the physical and chemical origins of selective ion-exchange abilities of different cations and detailed atomic structures of exchanged cations inside the nanoscale cavities of zeolites. Here, the precise locations of Cs+ ions captured within A-type zeolite were analyzed using high-resolution electron microscopy. Together with theoretical calculations, the stable positions of absorbed Cs+ ions in the nanocavities are identified, and the bonding environment within the zeolitic framework is revealed to be a key factor that influences the locations of absorbed cations.

  15. Atomic sites and stability of Cs+ captured within zeolitic nanocavities

    PubMed Central

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

    2013-01-01

    Zeolites have potential application as ion-exchangers, catalysts and molecular sieves. Zeolites are once again drawing attention in Japan as stable adsorbents and solidification materials of fission products, such as 137Cs+ from damaged nuclear-power plants. Although there is a long history of scientific studies on the crystal structures and ion-exchange properties of zeolites for practical application, there are still open questions, at the atomic-level, on the physical and chemical origins of selective ion-exchange abilities of different cations and detailed atomic structures of exchanged cations inside the nanoscale cavities of zeolites. Here, the precise locations of Cs+ ions captured within A-type zeolite were analyzed using high-resolution electron microscopy. Together with theoretical calculations, the stable positions of absorbed Cs+ ions in the nanocavities are identified, and the bonding environment within the zeolitic framework is revealed to be a key factor that influences the locations of absorbed cations. PMID:23949184

  16. Chemical Interactions in Multimetal/Zeolite Catalysts

    SciTech Connect

    Sachtler, Wolfgang M. H.

    2004-04-16

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

  17. Treatment of Acid Mine Drainage Using Fly Ash Zeolite

    Microsoft Academic Search

    Bably Prasad; Robert J. G. Mortimer

    2011-01-01

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

  18. Zeolite-combined plasma reactor for decomposition of toluene

    Microsoft Academic Search

    S.-M. Oh; H.-H. Kim; H. Einaga; A. Ogata; S. Futamura; D.-W. Park

    2006-01-01

    Toluene was decomposed in a surface-discharge plasma reactor and the combined effect of zeolite in the plasma reactor was studied. The decomposition of toluene and the product compositions depended on the reactor configuration and the capacity of zeolite to adsorb toluene. Toluene adsorbed on the zeolite (micro-pores) was not properly decomposed in the head of the plasma (P1), while it

  19. Heat of adsorption of ammonia by type E zeolites

    Microsoft Academic Search

    S. S. Khvoshchev; V. E. Skazyvaev; S. P. Zhdanov; I. V. Karetina

    1978-01-01

    Conclusions 1.Measurement has been made of the heat evolved in the adsorption of ammonia on calcium, calcium-sodium, and sodium forms of type E zeolites.2.The Ca2+ cations of type E zeolites are more active which respect to adsorbing ammonia molecules than are the Ca2+ ions of synthetic faujasites and type A zeolites.3.The results obtained are analyzed in terms of lattice position

  20. Modified zeolites as catalysts in the Friedel-Crafts acylation

    Microsoft Academic Search

    Kristin Gaare; Duncan Akporiaye

    1996-01-01

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

  1. Microwave synthesis of LTA zeolite membranes without seeding

    Microsoft Academic Search

    Yanshuo Li; Hongliang Chen; Jie Liu; Weishen Yang

    2006-01-01

    A new method called “in-situ aging—microwave synthesis” was developed for zeolite membrane synthesis. High quality LTA zeolite membranes were successfully microwave-synthesized without seeding by this method. It was found that the formed zeolite layer was composed of sphere grains with undefined crystal facets. The necessity of in-situ aging was discussed. The effects of synthesis parameters including in-situ aging temperature, time

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

    NASA Astrophysics Data System (ADS)

    Yuan, Chen; Jones, Sam; Blackburn, Stuart

    2012-12-01

    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.

  3. Barrier properties of hydrogenated acrylonitrile-butadiene rubber composites containing modified layered aluminosilicates

    NASA Astrophysics Data System (ADS)

    Krzemi?ska, S.; Rzymski, W. M.

    2011-12-01

    The resistance to permeation by the selected solvents of flat membranes made of cured hydrogenated acrylonitrile-butadiene rubber (HNBR) materials without any fillers and containing 5 phr of layered aluminosilicate nanofiller (bentonite), modified with various types of ammonium salts or N330 type carbon black, was investigated. The barrier properties were assessed on the basis of the breakthrough time of a liquid with low (cyclohexane) or average (butyl acetate) thermodynamic affinity to HNBR, determined according to EN 6529:2001, through a cured elastomer sample. The addition of bentonite, irrespectively of the method of modification of its particles, was found to increase the cured HNBR breakthrough time by 20 - 35 % in the case of slowly permeating non-polar cyclohexane, and by 50 - 130 % in the case of polar butyl acetate permeating more rapidly, in comparison with the barrier material containing no filler. The layered aluminosilicate nanofillers increased the breakthrough time of the material sample for both the tested solvents. In particular, the breakthrough time for polar butyl acetate was even longer than for conventional carbon black. Additionally, the increase of the breakthrough time was observed to depend on the modifier of bentonite particle surface.

  4. Ordered hexagonal mesoporous aluminosilicates with low Si/Al ratio: synthesis, characterization, and catalytic application.

    PubMed

    Liu, Aifeng; Che, Hongwei; Liu, Chuanzhi; Fu, Quanrong; Jiang, Ruijiao; Wang, Cheng; Wang, Liang

    2014-06-01

    Ordered hexagonal mesoporous aluminosilicates with lower Si/Al ratio below 5 have been successfully synthesized via the co-assembly of preformed aluminosilicate precursors with Gemini surfactant [C12H25N+(CH3)2(CH2)6N+(CH3)2C12H25] x 2Br(-) as the template. Powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, N2 adsorption-desorption isotherm measurements, Fourier transform infrared spectroscopy, 27Al nuclear magnetic resonance, thermogravimetric analysis, and temperature-programmed desorption of cyclohexylamine are employed to characterize the resulting samples. The phenol alkylation reaction is carried out to evaluate their catalytic performances. These studies indicate that the sample with a low Si/Al ratio of 3 still retains a highly ordered hexagonal mesoporous structure. And it also possesses the highest acidity of 0.96 mmol among the samples with lower Si/Al ratios below 5 due to its higher specific surface area together with more content of tetrahedrally coordinated Al in the framework. The catalytic tests confirm that the acidity of the samples plays a key role in determining their catalytic performances. PMID:24738433

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

    SciTech Connect

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

    2011-03-23

    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.

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

    USGS Publications Warehouse

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

    1986-01-01

    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.

  7. Viscosity-temperature relations and structure in fully polymerized aluminosilicate melts from ion dynamics simulations

    SciTech Connect

    Scamehorn, C.A.; Angell, C.A. (Arizona State Univ., Tempe (United States))

    1991-03-01

    Results of a series of molecular dynamics simulations indicate that the Al:Si ratio present in aluminosilicate melts induces a chemical pressure that significantly influences the temperature dependence of the melt viscosity. The temperature dependence of the T-O bond length and T-O-T angle in the melt has been calculated for albite, anorthite, nepheline, and MgAl{sub 2}Si{sub 2}O{sub 8} (a magnesium analog of anorthite) at their experimental melt densities at atmospheric pressure and for pure silica at two different densities corresponding to V/V{sub 0} = 1.0 (1atm) and V/V{sub 0} = 0.8 ({approximately}4 GPa). These simulations show that melt fragility can be correlated to increasing T-O length and decreasing T-O-T angle, both of which are characteristics of silicate melts under increasing pressure. Framework cations with coordination numbers greater than four are observed in these aluminosilicate melts and are shown to be related to fragile behavior. Finally, for nepheline and anorthite we infer a large contribution to fragility from configurational disordering of Al-O-Si links which are known to be dominant in the glasses but are found to be absent from the simulated melts.

  8. Fate of Uranium during Sodium Aluminosilicate Formation under Waste Tank Conditions

    SciTech Connect

    Wilmarth, B

    2005-06-22

    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.

  9. Electromagnetic and Mechanical Properties of Silica-Aluminosilicates Plasma Sprayed Composite Coatings

    NASA Astrophysics Data System (ADS)

    Cipri, F.; Bartuli, C.; Valente, T.; Casadei, F.

    2007-12-01

    The physico-chemical and thermo-mechanical properties of aluminosilicate ceramics (high-melting point, low thermal expansion coefficient, excellent thermal shock resistance, low-density and good corrosion resistance) make this class of materials a good option for high-temperature structural applications. Al2O3-SiO2 compounds show an excellent refractory behavior allowing a wide use as wear-resistant thermal barrier coatings, in metallurgical and glass plants and in high temperature heat exchangers. Moreover, the low values of thermal expansion coefficient and of complex permittivity allow to extend the use of this ceramic for microelectronic devices, radome for antennas and electromagnetic windows for microwaves and infrared. The present article presents the results of an extensive experimental activity carried out to produce thick aluminosilicate coatings by plasma-spray technique. The APS deposition parameters were optimized on the basis of a surface response approach, as specified by design of experiments (DoE) methodologies. Samples were tested for phase composition, total porosity, microstructure, microhardness, deposition efficiency, fracture toughness, and modulus of rupture. Finally, coatings were characterized for their particularly interesting electromagnetic properties: complex permittivity was measured at microwave frequency using a network analyzer with wave guide.

  10. The Brillouin gain coefficient of Yb-doped aluminosilicate glass optical fibers

    NASA Astrophysics Data System (ADS)

    Dragic, Peter D.; Ballato, John; Morris, Stephanie; Hawkins, Thomas

    2013-07-01

    Provided herein is a detailed analysis of the Brillouin spectroscopy of the ytterbia (Yb2O3) dopant in aluminosilicate glass optical fibers. Yb-doped fiber lasers have become ubiquitous, and the results presented here may be used to design lasers and amplifiers for narrow linewidth systems and applications. It is found, with a high degree of certainty, that Yb2O3 has an acoustic velocity that is lower than that of silica, a Brillouin spectral width (or material acoustic damping coefficient) that is about 80 times greater than that of silica, and photoelastic constants (Pockels' coefficients) that are negative. It is found that the primary influence of ytterbia in concentrations typical of active fibers is to broaden the Brillouin gain spectrum, thereby reducing the peak Brillouin gain. A set of design curves is provided outlining the Brillouin gain coefficient as a function of alumina concentration for several ytterbia concentrations, which can be utilized to design fiber structures with reduced Brillouin gain. The Yb-doped aluminosilicate fiber system is compared to the Yb-doped phosphosilicate system, and a high degree of similarity is found between them at low Al2O3 or P2O5 doping levels. However, for fiber produced utilizing conventional techniques, the phosphosilicates are found to have the potential for lower Brillouin gain since more P2O5 can be reliably incorporated into the glassy matrix.

  11. Tetraethylenepentamine embedded zeolite A for carbon dioxide adsorption.

    PubMed

    Kim, Young-Ki; Mo, Yong-Hwan; Lee, Jun; You, Hyo-Sang; Yi, Chang-Keun; Park, Young Cheol; Park, Sang-Eon

    2013-04-01

    Tetraethylenepentamine (TEPA) embedded zeolite A crystals were synthesized by using TEPA and the preformed zeolite A precursor under the microwave irradiation. The presence of TEPA in zeolite A crystal was confirmed by TG analysis and FTIR, Raman spectra. The CO2 adsorptive behavior of TEPA embedded zeolite A samples was investigated by CO2 isotherms measured at 25 degrees C comparing with zeolite A. The optimum CO2 sorption capacity was found in the case of 7.5% TEPA embedded zeolite A, which showed 3.75 mmol g(-1) where as the zeolite A showed less CO2 adsorption capacity of 2.88 mmol g(-1). The adsorption capacity of TEPA embedded Zeolite A was sustained up to 90% during 4 cycles of temperature swing adsorption (TSA) from 40 degrees C to 140 degrees C, indicating that the TEPA embedded Zeolite A was found to be useful as one of the application to solid amine adsorbent for CO2. PMID:23763147

  12. Aluminosilicate and borosilicate single 4-rings: Effects of counterions and water on structure, stability, and spectra

    NASA Astrophysics Data System (ADS)

    Tossell, J. A.; Sághi-Szabó, G.

    1997-03-01

    Rings containing four tetrahedrally coordinated atoms connected by bridging O atoms in a single four ring (S4R) geometry have been used to model the properties of ring species occurring in aluminosilicate and borosilicate crystals, glasses, and melts. We recently established a molecular basis for the Al avoidance, or "Loewenstein's rule," using molecular quantum mechanical methods applied to the non-Loewenstein paired, i.e., Al … Al … Si … Si …, and the Loewenstein alternating, i.e., Al … Si … Al … Si …, geometric isomers of the Si 2Al 2O 4H 8-2 molecular anion. We here extend this model to the Si 2Al 2O 4H 8-2 and Si 2B 2O 4H 8-2 molecules neutralized by various counterions such as H +, CH 3+, Na +, and Ca 2+. Our calculations show that the paired geometry isomer can be strongly stabilized by coordination of counterions to the underbonded bridging O in the Al?O?Al or B?O?B linkages. For the Si 2Al 2 … case, coordination of H + or Ca 2+ to the underbonded O actually makes the paired geometry isomer more stable than the alternating geometry one. This result helps us to explain why the energy penalty for Al?O?Al bonds is smaller in Ca aluminosilicates than in Na aluminosilicates. For the Si 2B 2O 4H 8(CH 3) 2 and Si 2B 2O 4H 8Ca molecules the paired geometry is again the more stable. Underbonded O atoms in B?O?B linkages are found to be stabilized more strongly by counterions than are those in Al?O?Al linkages. This provides an explanation for the different T,T' ordering patterns in anorthite, CaAl 2Si 2O 8, and danburite, CaB 2Si 2O 8. Our results also indicate that it may be possible to systematically synthesize gas phase and condensed phase species in which the Al avoidance rule is violated. We have also used the S4R species to model rings in Na aluminosilicate glasses and their reaction with H 2O. Calculated NMR shieldings are reduced (deshielded) by about 5-6 ppm for both Si and Al when two Na + ions are coordinated to Si 2Al 2O 12H 8-2. Reaction of H 2O with Si 2Al 2O 12H 8Na 2 does not cause hydrolysis of the Si?O?Al bond or protonation of the bridging O, rather the H 2O coordinates strongly to Na + while H-bonding to the bridging O. This reaction is exoergic by about 35 kJ/mol and produces a slight shielding of the Si and a reduction in the quadrupole coupling constant of the Al. No single species was found to be consistent with all the NMR spectral data for hydrous aluminosilicate glasses.

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

    Microsoft Academic Search

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

    2002-01-01

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

  14. Pf/Zeolite Catalyst for Tritium Stripping

    SciTech Connect

    Hsu, R.H.

    2001-03-26

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

  15. Olefins from methanol by modified zeolites

    SciTech Connect

    Inui, T.; Takegami, Y.

    1982-11-01

    Compares the effects of modified catalysts (ZSM-34 and ZSM-5 class zeolites) on methanol conversion to olefins (MTO) with regard to olefin selectivity and cost. Presents tables with prices of olefins in the US and Japan; comparison of methanol-cracking with naphtha cracking; methanol conversion data for Type-1, Type-II and reference catalysts; hydrocarbon distribution from MTO processes; and speculative economics for MTO processes of Concept-1 and 2. Diagrams the proposed MTO process scheme. Scanning electron micrographs of the zeolite catalysts are shown. Graphs indicate the change of ethylene prices in the US since 1978 and forecast ethylene prices in several countries. Concludes that the prices of ethylene for both MTO processes examined compare favorably with products of conventional processes.

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

    NASA Astrophysics Data System (ADS)

    Chanthaanont, Pojjawan; Sirivat, Anuvat

    2012-02-01

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

  17. Modified ruthenium exchanged zeolites for enantioselective hydrogenation

    Microsoft Academic Search

    V. I. Pârvulescu; S. Coman; C. Radu; D. Macovei; Em Angelescu; R. Russu

    1995-01-01

    Preparation of modified ruthenium molecular sieves has been investigated in two steps-depositionof ruthenium and modifying of ruthenium molecular sieves in presence of ligands. As support sieve there were used two molecular sieves with large pore apertures and low acidity strength (zeolite L and APO-34). Correlation of in situ UV-VIS ruthenium deposition measurements with catalyst characterisation revealed that ruthenium deposition takes

  18. Physical properties of Eu^3+ doped sodium magnesium alumino-silicate glasses studied by light scattering spectroscopy

    Microsoft Academic Search

    Guoqing Shen; Zhandos Utegulov; James P. Wicksted; Abdur Rahman

    2001-01-01

    Brillouin scattering and absorption measurements on various Al and Na concentrations of Europium doped sodium magnesium alumino-silicate glasses (ESMAS) were performed to study the glass structures and optical properties of ESMAS. The linewidth, frequency shift, and intensity of Brillouin peaks were determined to calculate the phonon attenuation, elastic constants, photo-elastic coefficients, and the bond polarizability parameter. The parameters obtained from

  19. Crystalline titanate catalyst supports

    SciTech Connect

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

    1991-12-31

    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.

  20. Crystalline titanate catalyst supports

    DOEpatents

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

    1993-01-01

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

  1. Crystalline titanate catalyst supports

    DOEpatents

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

    1993-01-05

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

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

    SciTech Connect

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

    2012-01-01

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

  3. Crystalline beam ground state

    SciTech Connect

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

    1993-06-11

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

  4. Highly attrition resistant mesoporous catalytic cracking catalysts

    Microsoft Academic Search

    1993-01-01

    A catalytic cracking catalyst is described for converting a hydrocarbon feedstock at elevated temperature in the substantial absence of hydrogen, into lower average molecular weight, lower boiling hydrocarbon transportation fuel which comprises a crystalline aluminosilicate zeolite having a silica:alumina mole ratio greater than 2:1, and uniform pore diameters ranging from about 4 Angstroms to about 15 Angstroms in diameter, in

  5. Aluminosilicate and borosilicate single 4-rings: Effects of counterions and water on structure, stability, and spectra

    SciTech Connect

    Tossell, J.A.; Saghi-Szabo, G. [Univ. of Maryland, College Park, MD (United States)] [Univ. of Maryland, College Park, MD (United States)

    1997-03-01

    Rings containing four tetrahedrally coordinated atoms connected by bridging O atoms in a single four ring (S4R) geometry have been used to model the properties of ring species occurring in aluminosilicate and borosilicate crystals, glasses, and melts. We recently established a molecular basis for the Al avoidance, or {degrees}Loewenstein`s rule,{close_quotes} using molecular quantum mechanical methods applied to the non-Loewenstein paired, i.e., Al...Al...Si...Si..., and the Loewenstein alternating, i.e., Al...Si...Al...Si..., geometric isomers of the Si{sub 2}Al{sub 2}O{sub 4}H{sub 8}{sup {minus}2} molecular anion. We here extend this model to the Si{sub 2}Al{sub 2}O{sub 4}H{sub 8}{sup {minus}2} and Si{sub 2}B{sub 2}O{sub 4}H{sub 8}{sup {minus}2} molecules neutralized by various counterions such as H{sup +}, CH{sub 3}{sup +}, Na{sup +}, and Ca{sup 2+}. Our calculations show that the paired geometry isomer can be strongly stabilized by coordination of counterions to the underbonded bridging O in the Al-O-Al or B-O-B linkages. For the Si{sub 2}Al{sub 2}...case, coordination of H{sup +} or Ca{sup 2+} to the underbonded O actually makes the paired geometry isomer more stable than the alternating geometry one. This result helps us to explain why the energy penalty for Al-O-Al bonds is smaller in Ca aluminosilicates than in Na aluminosilicates. For the Si{sub 2}B{sub 2}O{sub 4}H{sub 8}(CH{sub 3}){sub 2} and Si{sub 2}B{sub 2}O{sub 4}H{sub 8}Ca molecules the paired geometry is again the more stable. Underbonded O atoms in B-O-B linkages are found to be stabilized more strongly by counterions than are those in Al-O-Al linkages. This provides an explanation for the different T.T. {prime} ordering patterns in anorthite. CaAl{sub 2}Si{sub 2}O{sub 8}, and danburite, CaB{sub 2}Si{sub 2}O{sub 8}. Our results also indicate that it may be possible to systematically synthesize gas phase and condensed phase species in which the Al avoidance rule is violated. 44 refs., 4 figs., 1 tab.

  6. Some observations on the synthesis of fully-dispersible nanocrystalline zeolite ZSM-5.

    PubMed

    Selvin, Rosilda; Chiang, Anthony S T

    2014-09-01

    A facile method for the rapid synthesis of fully-dispersible ZSM-5 (Si/Al = 100) of about 30 nm size in high yield (about 91%) is described. The method comprises three steps, viz., concentration of an initial clear solution, low-temperature (80 degrees C) ageing of concentrated sol, and high-temperature (175 degrees C) hydrothermal treatment or microwave heating (175 degrees C) of aged concentrated sol. A simple vacuum-concentration method was used for the extraction of pure NPs of ZSM-5 in solution. XRD, FT-IR, TGA and ASAP characterizations showed that the NPs were partially crystalline. The concentration step accelerated the aggregation of primary units, which helps in the production of a large number of nucleation centers protected by TPA+ ions against aggregation. During low-temperature ageing, the number of critical sized nuclei increases, growing into zeolite. The high-temperature heating results in the complete growth of unreacted silica, giving high yields. A key factor for generating small non-aggregated zeolite crystals is the amount of water in the synthesis sol. The three-step method presented here produces a target material of small and uniform sized, non-aggregated ZSM-5 of about 30 nm in a short reaction time. The results are significant, as the synthesis method adopted here produces much uniform, non-aggregated nanocrystalline ZSM-5 in a shorter time with high yield. PMID:25924414

  7. Molecular Heterogeneous Catalysis: a Single-Site Zeolite-Supported Rhodium Complex for Acetylene Cyclotrimerization

    SciTech Connect

    Kletnieks, P.W.; Liang, A.J.; Craciun, R.; Ehresmann, J.O.; Marcus, D.M.; Bhirud, V.A.; Klaric, M.M.; Hayman, M.J.; Guenther, D.R.; Bagatchenko, O.P.; Dixon, D.A.; Gates, B.C.; Haw, J.F.

    2009-06-01

    By anchoring metal complexes to supports, researchers have attempted to combine the high activity and selectivity of molecular homogeneous catalysis with the ease of separation and lack of corrosion of heterogeneous catalysis. However, the intrinsic nonuniformity of supports has limited attempts to make supported catalysts truly uniform. We report the synthesis and performance of such a catalyst, made from [Rh(C{sub 2}H{sub 4}){sub 2}(CH{sub 3}COCHCOCH{sub 3})] and a crystalline support, dealuminated Y zeolite, giving {l_brace}Rh(C{sub 2}H{sub 4}){sub 2}{r_brace} groups anchored by bonds to two zeolite oxygen ions, with the structure determined by extended X-ray absorption fine structure (EXAFS) spectroscopy and the uniformity of the supported complex demonstrated by {sup 13}C NMR spectroscopy. When the ethylene ligands are replaced by acetylene, catalytic cyclotrimerization to benzene ensues. Characterizing the working catalyst, we observed evidence of intermediates in the catalytic cycle by NMR spectroscopy. Calculations at the level of density functional theory confirmed the structure of the as-synthesized supported metal complex determined by EXAFS spectroscopy. With this structure as an anchor, we used the computational results to elucidate the catalytic cycle (including transition states), finding results in agreement with the NMR spectra.

  8. Design of composite photocatalyst of TiO2 and Y-zeolite for degradation of 2-propanol in the gas phase under UV and visible light irradiation.

    PubMed

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

    2014-01-01

    Hydrophobic Y-zeolite (SiO2/Al2O3 = 810) and TiO2 composite photocatalysts were designed by using two different types of TiO2 precursors, i.e., titanium ammonium oxalate and ammonium hexafluorotitanate. The porous structure, surface property and state of TiO2 were investigated by various characterization techniques. By using an ammonium hexafluorotitanate as a precursor, hydrophobic modification of the Y-zeolite surface and realizing visible light sensitivity was successfully achieved at the same time after calcination at 773 K in the air. The prepared sample still maintained the porous structure of Y-zeolite and a large surface area. Highly crystalline anatase TiO2 was also formed on the Y-zeolite surface by the role of fluorine in the precursor. The usages of ammonium hexafluorotitanate were effective for the improvement of the photocatalytic performance of the composite in the degradation of 2-propanol in the gas phase under UV and visible light (? > 420 nm) irradiation. PMID:25314607

  9. In Situ SAXS/WAXS of Zeolite Microwave Synthesis: NaY, NaA, and Beta Zeolites

    SciTech Connect

    Panzarella,B.; Tompsett, G.; Conner, W.; Jones, K.

    2007-01-01

    A custom waveguide apparatus is constructed to study the microwave synthesis of zeolites by in situ small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). The WR-284 waveguide is used to heat precursor solutions using microwaves at a frequency of 2.45 GHz. The reaction vessels are designed to include sections of thin-walled glass, which permit X-rays to pass through the precursor solutions with minimal attenuation. Slots were machined into the waveguide to provide windows for X-ray energy to enter and scatter from solutions during microwave heating. The synthesis of zeolites with conventional heating is also studied using X-ray scattering in the same reactor. SAXS studies show that the crystallization of beta zeolite and NaY zeolite is preceded by a reorganization of nanosized particles in their precursor solutions or gels. The evolution of these particles during the nucleation and crystallization stages of zeolite formation depends on the properties of the precursor solution. The synthesis of NaA and NaX zeolites and sodalite from a single zeolite precursor is studied by microwave and conventional heating. Microwave heating shifts the selectivity of this synthesis in favor of NaA and NaX over sodalite; conventional heating leads to the formation of sodalite for synthesis from the same precursor. The use of microwave heating also led to a more rapid onset of NaA zeolite product crystallization compared to conventional heating. Pulsed and continuous microwave heating are compared for zeolite synthesis. The resulting rates of formation of the zeolite products, and the relative amounts of the products determined from the WAXS spectra, are similar when either pulsed or continuous microwave heating is applied in the reactor while maintaining the same synthesis temperature. The consequences of these results in terms of zeolite synthesis are discussed.

  10. FUNDAMENTALS AND APPLICATIONS OF PERVAPORATION THROUGH ZEOLITE MEMBRANES

    EPA Science Inventory

    Zeolite membranes are well suited for separating liquid-phase mixtures by pervaporation because of their molecular-sized pores and their hydrophilic/hydrophobic nature, and the first commercial application of zeolite membranes has been for dehydrating organics [1]. Because of ...

  11. Crystal chemistry of the zeolites erionite and offretite

    Microsoft Academic Search

    E. PASSAGLIA; G. ARTIOLI; A. GUALTIERI

    Many known occurrences of the zeolites erionite and offretite have been characterized by electron probe microanalysis, X-ray powder diffraction, and optical microscopy. For the first time, a substantial amount of experimentally consistent and homogeneous chemical and crystallographic data have been evaluated for these natural zeolites. Systematic anal- ysis of the data, performed by statistical multivariate analysis, leads to the following

  12. Generation, Characterization, and Impact of Mesopores in Zeolite Catalysts

    Microsoft Academic Search

    Sander van Donk; Andries H. Janssen; Johannes H. Bitter; Krijn P. de Jong

    2003-01-01

    Amongst the current developments in the field of hierarchical pore structures, the creation of mesopores in zeolite crystals is the most frequently employed way to combine micropores with mesopores in one material. In this review an overview is presented of the different approaches to generate and characterize mesopores in zeolite crystals and establish their impact on the catalytic action. Mesopores

  13. Autocatalytic cure kinetics of natural zeolite filled epoxy composites

    Microsoft Academic Search

    Jae-Young Lee; Mi-Ja Shim; Sang-Wook Kim

    1997-01-01

    The effect of natural zeolite on the cure kinetics of epoxy resin system was studied by autocatalytic cure kinetics. In the thermograms obtained from dynamic analysis, the exothermic peak separated into two peaks by the addition of natural zeolite, and the exothermic peak temperatures and the reaction starting temperatures decreased. In the autocatalytic cure rate, the maximum cure rate appeared

  14. Effects of heating on salt-occluded zeolite

    SciTech Connect

    Lewis, M.A.; Hash, M.C.; Pereira, C.; Ackerman, J.P.

    1996-05-01

    The electrometallurgical treatment of spent nuclear fuel generates a waste stream of fission products in the electrolyte, LiCl-KCl eutectic salt. Argonne National Laboratory is developing a mineral waste form for this waste stream. The waste form consists of a composite formed by hot pressing salt-occluded zeolite and a glass binder. Pressing conditions must be judiciously chosen. For a given pressure, increasing temperatures and hold times give denser products but the zeolite is frequently converted to sodalite. Reducing the temperature or hold time leads to a porous zeolite composite. Therefore, conditions that affect the thermal stability of salt-occluded zeolite both with and without glass are being investigated in an ongoing study. The parameters varied in this stage of the work were heating time, temperature, salt loading, and glass content. The heat-treated samples were examined primarily by X-ray diffraction. Large variations were found in the rate at which salt-occluded zeolite converted to other phases such as nepheline, salt, and sodalite. The products depended on the initial salt loading. Heating times required for these transitions depended on the procedure and temperature used to prepare the salt-occluded zeolite. Mixtures of glass and zeolite reacted much faster than the pure salt-occluded zeolite and were almost always converted to sodalite.

  15. Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen

    DOEpatents

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

    1999-06-22

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

  16. Hydrogen atom addition to hydrocarbon guests in radiolyzed zeolites

    Microsoft Academic Search

    D. W. Werst; P. Han; S. C. Choure; E. I. Vinokur; L. Xu; A. D. Trifunac; L. A. Eriksson

    1999-01-01

    The formation of H adducts during radiolysis of zeolites containing olefinic and aromatic hydrocarbon guests was demonstrated to occur by H atom transfer from the zeolite to the adsorbed molecules. The H adducts and other paramagnetic radiolysis products (radical cations and H-loss radicals) were detected by EPR spectroscopy. The mechanism of H adduct formation was confirmed by, inter alia, H\\/D

  17. Middle distillate hydrotreatment zeolite catalysts containing Pt/Pd or Ni 

    E-print Network

    Marin-Rosas, Celia

    2009-05-15

    A study on middle distillate hydrotreatment zeolite catalysts containing Pt/Pd and/or Ni was performed. The effect of the addition of the corresponding CoMo, CoMoPd, CoMoPtPd and CoMoNi in PdNiPt-zeolite, Pt-zeolite, Ni-zeolite, and Pd...

  18. Density Functional Theory Study of Transformations of Nitrogen Oxides Catalyzed by Cu-Exchanged Zeolites

    E-print Network

    Adams, James B

    chemistry of nitrogen oxides. The catalyst active site is considered to be an isolated, zeolite (Z)-bound Cu zeolite catalyst chemistry. In a high silica zeolite such as Cu-ZSM-5, exchanged Cu is believed to exist-Exchanged Zeolites W. F. Schneider* and K. C. Hass Ford Research Laboratory, MD 3083/SRL, Dearborn, Michigan 48121

  19. An investigation of plant growth in an organo-zeolitic substrate and its ecological significance

    Microsoft Academic Search

    Peter J. Leggo

    2000-01-01

    This work concerns a series of experiments designed to test and understand the effect of ammoniated zeolite on plant growth. The affinity of the zeolite mineral clinoptilolite for NH4+ is utilised in organo-zeolitic substrates to enhance plant growth. By comparing plants grown in substrates with and without ammoniated zeolite, an increase in plant dry weight of some 19% was shown

  20. Formation of superacid centers in the structure of zeolite ZSM-5

    NASA Astrophysics Data System (ADS)

    Kitaev, L. E.; Kolesnikova, E. E.; Biryukova, E. N.; Kolesnichenko, N. V.; Khadzhiev, S. N.

    2013-04-01

    The structural changes and acid characteristics of the zeolite ZSM-5 modified with titanium and sulfur were studied. The modifier components were chemically bonded to the zeolite structure. The acid characteristics of zeolite changed and superacid centers appeared. A physicochemical study showed that treatment of zeolite with titanium tetrachloride and sulfuryl chloride did not change its structure and molecular-sieve properties.

  1. Tailoring of Boehmite-Derived Aluminosilicate Aerogel Structure and Properties: Influence of Ti Addition

    NASA Technical Reports Server (NTRS)

    Hurwitz, Frances I.; Guo, Haiquan; Sheets, Erik J.; Miller, Derek R.; Newlin, Katy N.

    2010-01-01

    Aluminosilicate aerogels offer potential for extremely low thermal conductivities at temperatures greater than 900 C, beyond where silica aerogels reach their upper temperature limits. Aerogels have been synthesized at various Al:Si ratios, including mullite compositions, using Boehmite (AlOOH) as the Al source, and tetraethoxy orthosilicate as the Si precursor. The Boehmite-derived aerogels are found to form by a self-assembly process of AlOOH crystallites, with Si-O groups on the surface of an alumina skeleton. Morphology, surface area and pore size varies with the crystallite size of the starting Boehmite powder, as well as with synthesis parameters. Ternary systems, including Al-Si-Ti aerogels incorporating a soluble Ti precursor, are possible with careful control of pH. The addition of Ti influences sol viscosity, gelation time pore structure and pore size distribution, as well as phase formation on heat treatment.

  2. Oxidation behavior of a Si-C-O-fiber-reinforced magnesium aluminosilicate

    SciTech Connect

    Kumar, A.; Knowles, K.M. [Univ. of Cambridge (United Kingdom). Dept. of Materials Science and Metallurgy

    1996-09-01

    The oxidation behavior of a Si-C-O-fiber-reinforced magnesium aluminosilicate has been investigated in the temperature range 1,000--1,200 C. Parabolic weight gain, together with other experimental observations, has suggested that the oxidation process was controlled by the outward diffusion of carbon monoxide gas. The matrix and fibers reacted to form enstatite and forsterite. During the initial stages of oxidation, an interlayer containing a mixture of silica and turbostratic carbon was formed. This interlayer was modified progressively over time to create interface morphologies near the surface and near the center of the oxidized samples that were different from one another. A mechanism explaining the morphological evolution of the fiber-matrix interfaces has been proposed.

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

    SciTech Connect

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

    1993-05-15

    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.

  4. Mesoporous nickel-aluminosilicate nanocomposite: a solid acid catalyst for ether synthesis.

    PubMed

    Neelakandeswari, N; Karvembu, R; Dharmaraj, N

    2013-04-01

    Mesoporous nickel aluminosilicate, a solid acid catalyst prepared by sol-gel technique was utilized as a heterogeneous catalyst for the synthesis of symmetrical ethers by dehydro-condensation of alcohols. The prepared catalysts were characterized by Fourier-transform infra red spectroscopy (FT-IR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), N2 adsorption-desorption analysis, temperature programmed desorption of ammonia (TPD) and X-ray photoelectron spectroscopic techniques. The presence of the catalyst assisted the etherification reaction in 30 minutes. Ethers formed in these reactions were quantified by gas chromatography (GC) and the identities of few of them were confirmed by nuclear magnetic resonance spectral data (NMR). PMID:23763171

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

    NASA Astrophysics Data System (ADS)

    González, C. P.; Montaño, A. M.; González, A. K.; Ríos, C. A.

    2014-06-01

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

  6. Surface metal ion enhancement of thermally treated zeolites

    SciTech Connect

    Willis, W.S.; Suib, S.L.

    1986-09-03

    During the past several years the area of zeolite science has received increasingly intense attention owing to the preparation of new molecular sieves and the availability of modern spectroscopic methods for the study of these materials. The majority of spectroscopic studies of zeolites have focused on measurements of bulk magnetic, electronic, and structural properties, but few surface studies have been reported. Surface-inhomogeneous aluminum and silicon species have recently been reported by Barr and co-workers. In this study the authors have heated metal ion containing zeolites under controlled conditions in order to probe interactions between the zeolite and the metal ion. Here they present preliminary results for Ag/sup +//NaY and Cs/sup +//NaY zeolites studied by X-ray photoelectron spectroscopy (XPS), static secondary ion mass spectrometry (SSIMS), and ion scattering spectroscopy (ISS).

  7. Influence of NaA Zeolite Crystal Expansion/Contraction on Zeolite Membrane Separations

    SciTech Connect

    Sorenson, Stephanie G [University of Colorado, Boulder; Payzant, E Andrew [ORNL; Gibbons, Will T [University of Colorado, Boulder; Soydas, Belma [University of Colorado, Boulder; Kita, Hidetoshi [Yamaguchi University, Japan; Noble, Richard D [University of Colorado, Boulder; Falconer, John L. [University of Colorado, Boulder

    2011-01-01

    In-situ powder XRD measurements showed that the NaA zeolite unit cell contracts and expands upon adsorption, and these changes in zeolite crystal size correlate with permeation changes through NaA zeolite membranes. These membranes had high pervaporation selectivities, even though gas permeation was mainly through defects, as indicated by Knudsen selectivities for gases. At 300 K and a thermodynamic activity of 0.03, water contracted the NaA crystals by 0.22 vol%, and this contraction increased the helium flux through two NaA membranes by approximately 80%. Crystal contraction also increased the fluxes of i-butane during vapor permeation and i-propanol (IPA) during pervaporation (~ 0.03 wt% water). At activities above 0.07, water expanded NaA crystals and correspondingly decreased the membrane fluxes of helium, i-butane, and IPA. Similarly, methanol contracted NaA crystals by 0.05 vol% at an activity of 0.02, and this contraction slightly increased the helium and i-butane fluxes through a NaA membrane. Above an activity of 0.06, methanol expanded the crystals, and the fluxes of helium and i-butane through a NaA membrane decreased. The adsorbate-induced changes explain some pervaporation behavior reported by others, and they indicate that crystal expansion and contraction may increase or decrease zeolite NaA membrane selectivity by changing the defect sizes.

  8. Carbon dioxide and methane transport in DDR zeolite: insights from molecular simulations into carbon dioxide separations in small pore zeolites

    Microsoft Academic Search

    Sang Eun Jee; David S. Sholl

    2009-01-01

    Zeolites are good candidates as a membranes for chemical separations because of their excellent chemical and thermal stability. Cage type zeolites are promising materials for gas separation since their narrow windows are expected to control molecular transport. DDR is one of the strongest candidates for light gas separations because of its narrow 8MR window. In our study, we examined the

  9. Aluminum coordinations for aluminosilicate glasses at 1 atm. and 3GPa: a 27Al MAS NMR study

    NASA Astrophysics Data System (ADS)

    Allwardt, J. R.; Stebbins, J. F.; Withers, A. C.; Hirschmann, M. M.

    2003-12-01

    In this study, we used 27Al MAS NMR to investigate the distribution of different aluminum coordinations in ambient pressure and moderate pressure (3GPa) aluminosilicate glasses with compositions of Mx+(9-3x)Al2Si6O18, where M= Ca2+, Na+, and K+. These spectra were collected at 18.8 Tesla to minimize the peak broadening due to second-order quadrupolar effects, which causes overlapping peaks for different coordinations of Al. Aluminum is thought to be mostly tetrahedrally coordinated in ambient-pressure aluminosilicate glasses where M+(2-x)O >= Al2O3, but 27Al NMR studies have shown that small concentrations of high-coordinated Al are present in both charge balanced (Toplis et al. 2000; Stebbins et al. 2001) and "depolymerized" (M+(2-x)O > Al2O3) aluminosilicate glasses (Stebbins and Farnan 1992). The 27Al spectra of samples of this study show that these ambient pressure glasses all contain [5]Al. Interestingly, the NAS (Na-aluminosilicate) glass contains more [5]Al than the KAS glass (0.6 vs. 0.3, respectively), which is opposite of that observed for SiO[5] groups in binary silicate glasses (Stebbins and McMillan 1993). The CAS glass spectrum shows a shoulder at 25 ppm, but the [4]Al peak is too broad to assign a reliable percentage for the amount of [5]Al. Previous studies of high-pressure glasses have shown that Al transforms to higher coordinations with increasing pressures (Yarger et al. 1995). In this study, we observe that the 27Al MAS spectrum of the 3 GPa NAS glass shows that 7% [5]Al and 1% [6]Al species exist. Additionally, the spectra of the KAS glass shows that 2% [5]Al and possibly some [6]Al are present at 3 GPa. These spectra clearly show for the first time that pressure induced Al-coordination changes occur in aluminosilicate glasses at pressures of 3 GPa. Recent 27Al NMR spectra of high-pressure "depolymerized" aluminosilicate glasses with different fictive temperatures have shown that the amount of high-coordinated Al increases with increasing temperature, which suggests that these results represent a minimum value for the melt (Allwardt et al 2003). Further work will focus on obtaining data at higher pressures to determine the pressure dependence for the generation of these species.

  10. High pressure synthesis of novel, zeolite based nano-composite materials

    NASA Astrophysics Data System (ADS)

    Santoro, Mario

    2013-06-01

    Meso/micro-porous solids such as zeolites are complex materials exhibiting an impressive range of applications, including molecular sieve, gas storage, catalysis, electronics and photonics. We used these materials, particularly non catalytic zeolites in an entirely different fashion. In fact, we performed high pressure (0.5-30 GPa) chemical reactions of simple molecules on a sub-nanometer scale in the channels of a pure SiO2 zeolite, silicalite to obtain unique nano-composite materials with drastically modified physical and chemical properties. Our material investigations are based on a combination of X-ray diffraction and optical spectroscopy techniques in the diamond anvil cell. I will first briefly show how silicalite can be easily filled by simple molecules such as Ar, CO2 and C2H4 among others from the fluid phase at high pressures, and how this efficient filling removes the well known pressure induced amorphization of the silica framework (Haines et al., JACS 2010). I will then present on a silicon carbonate crystalline phase synthesized by reacting silicalite and molecular CO2 that fills the nano-pores, at 18-26 GPa and 600-980 K; after the synthesis the compound is temperature quenched and it results to be slightly metastable at room conditions (Santoro et al., PNAS 2011). On the other hand, a stable at room condition spectacular crystalline nano-composite is obtained by photo-polymerizing ethylene at 0.5-1.5 GPa under UV (351-364 nm) irradiation in the channels of silicalite (Santoro et al., Nat. Commun, in press 2013). For this composite we obtained a structure with single polyethylene chains adapting very well to the confining channels, which results in significant increases in bulk modulus and density, and the thermal expansion coefficient changes sign from negative to positive with respect to the original silicalite host. Mechanical properties may thus be tuned by varying the amount of polymerized ethylene. We then think our findings could allow the high pressure, catalyst free synthesis of a unique generation of technological, functional materials based on simple hydrocarbons polymerized in confining meso/micro-porous solids.

  11. Carbon dioxide sensitivity of zeolitic imidazolate frameworks.

    PubMed

    Mottillo, Cristina; Friš?i?, Tomislav

    2014-07-14

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

  12. Distribution of metal and adsorbed guest species in zeolites

    SciTech Connect

    Chmelka, B.F.

    1989-12-01

    Because of their high internal surface areas and molecular-size cavity dimensions, zeolites are used widely as catalysts, shape- selective supports, or adsorbents in a variety of important chemical processes. For metal-catalyzed reactions, active metal species must be dispersed to sites within the zeolite pores that are accessible to diffusing reactant molecules. The distribution of the metal, together with transport and adsorption of reactant molecules in zeolite powders, are crucial to ultimate catalyst performance. The nature of the metal or adsorbed guest distribution is known, however, to be dramatically dependent upon preparatory conditions. Our objective is to understand, at the molecular level, how preparatory treatments influence the distribution of guest species in zeolites, in order that macroscopic adsorption and reaction properties of these materials may be better understood. The sensitivity of xenon to its adsorption environment makes {sup 129}Xe NMR spectroscopy an important diagnostic probe of metal clustering and adsorbate distribution processes in zeolites. The utility of {sup 129}Xe NMR depends on the mobility of the xenon atoms within the zeolite-guest system, together with the length scale of the sample heterogeneity being studied. In large pore zeolites containing dispersed guest species, such as Pt--NaY, {sup 129}Xe NMR is insensitive to fine structural details at room temperature.

  13. Investigation of structural charge transfer in zeolites by ultraviolet spectroscopy

    SciTech Connect

    Garbowski, E.D.; Mirodatos, C.

    1982-01-07

    Charge-transfer processes in various zeolites (faujasite, mordenite, ZSM5, erionite, and offretite) are evidenced by means of UV spectroscopy. UV bands at 240 and 320 nm are assigned to two different Al-O units. The band at 240 nm, present whatever the zeolite and whatever the chemical or thermal treatment, is related to framework Al-O units which are ''inert'' toward catalysis and easily removed by dealumination or dehydroxylation. The band at 320 nm, more stable toward dealumination and dehydroxylation, is specifically detected or significantly enhanced for catalytically active samples (methanol conversion, hydrocarbon cracking, and disproportionation). This band could be related to oxoaluminum structures inside the zeolite matrix.

  14. Method of preparing sodalite from chloride salt occluded zeolite

    DOEpatents

    Lewis, M.A.; Pereira, C.

    1997-03-18

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

  15. Method of preparing sodalite from chloride salt occluded zeolite

    DOEpatents

    Lewis, Michele A. (Naperville, IL); Pereira, Candido (Lisle, IL)

    1997-01-01

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

  16. Method of preparing sodalite from chloride salt occluded zeolite A

    SciTech Connect

    Lewis, M.A.; Pereira, C.

    1995-12-31

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

  17. Liquid crystalline polymers

    NASA Technical Reports Server (NTRS)

    1990-01-01

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

  18. Crystalline ion beams

    NASA Astrophysics Data System (ADS)

    Schramm, U.; Habs, D.

    2004-10-01

    Threading ions like pearls on a string in an ion storage ring by freezing out the inter-particle motion opens opportunities far beyond the means of standard accelerator physics. The usual heating due to collisions of particles within the beam almost completely vanishes, giving rise to a state of unprecedented brilliance and exceptional stability. Only recently, this long anticipated crystalline state of an ion beam could be realized experimentally in the rf quadrupole storage ring PALLAS in Munich, bridging the gap between ion trap experiments and high energy ion storage rings. The progress of this experiment and its implications on larger scale machines will be reported in detail and compared to the present situation at the heavy ion storage rings TSR (Heidelberg) and ASTRID (Aarhus) as well as ESR (GSI) and CRYring (Stockholm).

  19. Single crystalline magnetite nanotubes.

    PubMed

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

    2005-01-12

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

  20. Colliding Crystalline Beams

    SciTech Connect

    Haffmans, A.F.; Maletic, D.; Ruggiero, A.G.

    1995-06-01

    Crystalline Beams* are an ordered state 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 powerful cooling techniques (stochastic, electron, laser, ...). Depending on the focussing properties and dimensions of the storage ring, and on the ion beam density, several ground states are possible. All of them can be visualized as a bundle of n{sub s} symmetrically distributed, parallel strings. The longitudinal ion separation {lambda} is the same for all strings. The minimum temperature that can be achieved depends on die background noise of the cooling technique used. It is required for stability that the vibration amplitude of the ions is only a fraction of the separation {lambda}.

  1. Determination of the origin and magnitude of Al\\/Si ordering enthalpy in framework aluminosilicates from ab initio calculations

    Microsoft Academic Search

    J. D. C. McConnell; A. De Vita; S. D. Kenny; V. Heine

    1997-01-01

    Ab initio total energy calculations based on a new optimised oxygen pseudopotential has been used to determine the enthalpy\\u000a of disorder for the exchange of Al and Si in tetrahedral coordination in simple derivative aluminosilicate structures based\\u000a on the high temperature tridymite structure. The problem has been studied as a function of defect interaction, and defect\\u000a concentration, and the results

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

    Microsoft Academic Search

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

    2003-01-01

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

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

    Microsoft Academic Search

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

    1994-01-01

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

  4. Effect of Al Sources on the Synthesis and Acidic Characteristics of Mesoporous Aluminosilicates of MCM-41 Type

    Microsoft Academic Search

    Kondam Madhusudan Reddy; Chunshan Song

    1998-01-01

    This paper reports the synthesis of four series of mesoporous aluminosilicates (Al-MCM-41) and their acidic characteristics. Four different Al compounds were examined as Al source in the hydrothermal synthesis of Al-MCM-41, including pseudo boehmite, aluminum sulfate, aluminum isopropoxide, and sodium aluminate. Synthesized samples were characterized by XRD, chemical analysis, nitrogen adsorption, and 27Al MAS NMR. The acidic characteristics of the

  5. Efficacy of hydrated sodium calcium aluminosilicate and activated charcoal in reducing the toxicity of dietary aflatoxin to mink

    Microsoft Academic Search

    R. J. Bonna; R. J. Aulerich; S. J. Bursian; R. H. Poppenga; W. E. Braselton; G. L. Watson

    1991-01-01

    Mink were fed diets that contained 0, 34, or 102 ppb (µg\\/kg) aflatoxins with or without 0.5% hydrated sodium calcium aluminosilicate (HSCAS) and\\/or 1.0% activated charcoal (AC) for 77 days. Consumption of the diet that contained 34 ppb aflatoxins was lethal to 20% of the mink, while 102 ppb dietary aflatoxins resulted in 100% mortality within 53 days. The addition

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

    SciTech Connect

    LBNL; Roy, P.K.; Greenway, W.; Kwan, J.W.; Seidl, P.A.; Waldron, W.

    2011-04-20

    To heat targets to electron-volt temperatures for the study of warm dense matter with intense ion beams, low mass ions, such as lithium, have an energy loss peak (dE/dx) at a suitable kinetic energy. The Heavy Ion Fusion Sciences (HIFS) program at Lawrence Berkeley National Laboratory will carry out warm dense matter experiments using Li{sup +} ion beam with energy 1.2-4 MeV in order to achieve uniform heating up to 0.1-1 eV. The accelerator physics design of Neutralized Drift Compression Experiment (NDCX-II) has a pulse length at the ion source of about 0.5 {micro}s. Thus for producing 50 nC of beam charge, the required beam current is about 100 mA. Focusability requires a normalized (edge) emittance {approx}2 {pi}-mm-mrad. Here, lithium aluminosilicate ion sources, of {beta}-eucryptite, are being studied within the scope of NDCX-II construction. Several small (0.64 cm diameter) lithium aluminosilicate ion sources, on 70%-80% porous tungsten substrate, were operated in a pulsed mode. The distance between the source surface and the mid-plane of the extraction electrode (1 cm diameter aperture) was 1.48 cm. The source surface temperature was at 1220 C to 1300 C. A 5-6 {micro}s long beam pulsed was recorded by a Faraday cup (+300 V on the collector plate and -300 V on the suppressor ring). Figure 1 shows measured beam current density (J) vs. V{sup 3/2}. A space-charge limited beam density of {approx}1 mA/cm{sup 2} was measured at 1275 C temperature, after allowing a conditioning time of about {approx} 12 hours. Maximum emission limited beam current density of {ge} 1.8mA/cm{sup 2} was recorded at 1300 C with 10-kV extractions. Figure 2 shows the lifetime of two typical sources with space-charge limited beam current emission at a lower extraction voltage (1.75 kV) and at temperature of 1265 {+-} 7 C. These data demonstrate a constant, space-charge limited beam current for 20-50 hours. The lifetime of a source is determined by the loss of lithium from the alumino-silicate material either as ions or as neutral atoms. Our measurements suggest that for the low duty factor ({approx}10{sup -8}) required for NDCX-II, the lifetime of an emitter depends mostly on the duration that the emitter spends at elevated temperature, that is, at {ge} 1250 C. At this temperature, lithium loss is due mostly to neutral loss (not charged ion extraction). Extension of the lifetime of the source may be possible by lowering the temperature between beam pulses, when the idling time is sufficiently long between shots. The NDCX-II design seeks to operate the ion source at the maximum current density without running into heat management and lifetime problems. In preparation to fabricate a large (10.9 cm in diameter) source for the NDCXII experiment, recently a 7.6 cm diameter source has been fabricated. The method of fabrication of this larger source is similar to that of fabrication of a 6.3mm diameter source, except a longer furnace heating time was used due to mass differences. NDCX-II construction is in progress. Progress of lithium source study for NDCX-II is available in literature.

  7. Alkaline hydrothermal conversion of fly ash filtrates into zeolites 2: utilization in wastewater treatment.

    PubMed

    Somerset, Vernon; Petrik, Leslie; Iwuoha, Emmanuel

    2005-01-01

    Filtrates were collected using a codisposal reaction wherein fly ash was reacted with acid mine drainage. These codisposal filtrates were then analyzed by X-ray Fluorescence spectrometry for quantitative determination of the SiO2 and Al2O3 content. Alkaline hydrothermal zeolite synthesis was then applied to the filtrates to convert the fly ash material into zeolites. The zeolites formed under the experimental conditions were faujasite, sodalite, and zeolite A. The use of the fly ash-derived zeolites and a commercial zeolite was explored in wastewater decontamination experiments as it was applied to acid mine drainage in different dosages. The concentrations of Ni, Zn, Cd, As, and Pb metal ions in the treated wastewater were investigated. The results of the treatment of the acid mine drainage with the prepared fly ash zeolites showed that the concentrations of Ni, Zn, Cd, and Hg were decreased as the zeolite dosages of the fly ash zeolite (FAZ1) increased. PMID:15991728

  8. Structural Studies of Crystalline Polyaniline

    Microsoft Academic Search

    M. J. Winokur; B. R. Mattes

    1997-01-01

    The structural ordering within crystalline polyaniline (PANI) powders as emeraldine (i.e., at 50% oxidation) in both its base (EB) and (ES) salt forms has been studied using x-ray diffraction and these data reinforce the general belief that the local structure is extremely sensitive to the environmental conditions. PANI powders precipitated as ES immediately following synthesis lead to reasonably crystalline materials

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

    SciTech Connect

    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

    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.

  10. Alkylcarbenium Ion Concentrations in Zeolite Pores During Octane Hydrocracking on Pt\\/H-USY Zeolite

    Microsoft Academic Search

    Joris W. Thybaut; C. S. Laxmi Narasimhan; Guy B. Marin; Joeri F. M. Denayer; Gino V. Baron; Pierre A. Jacobs; Johan A. Martens

    2004-01-01

    Hydroconversion of octane over platinum loaded acid zeolites was simulated using a single-event microkinetic model. Significantly different values for the alkene standard protonation enthalpies, i.e., -59.2 and –94 kJ mol-1 for the charging of secondary and tertiary carbon atoms respectively, were obtained. This difference is in favor of a carbocationic nature of the reactive intermediates on the acid sites rather

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

    Microsoft Academic Search

    Thomas Bein; Peter A. Jacobs

    1984-01-01

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

  12. Xenon NMR studies of dynamics and exchange in zeolites

    SciTech Connect

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

    1996-10-01

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

  13. 12. INTERIOR OF BUILDING 2, ORIGINAL ZEOLITE PLANT, AT WEYMOUTH ...

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

    12. INTERIOR OF BUILDING 2, ORIGINAL ZEOLITE PLANT, AT WEYMOUTH LOOKING WEST TO FOUNTAIN. STAIRWAY RUNS DOWN TO FILTRATION BAYS. - F. E. Weymouth Filtration Plant, 700 North Moreno Avenue, La Verne, Los Angeles County, CA

  14. Single and Multiple Heteroatom Incorporation in MFI Zeolites 

    E-print Network

    Garcia Vargas, Nataly

    2012-11-05

    realistic scenarios for industrial implementation. The main objective of this dissertation was to study the single and simultaneous framework incorporation of tin, boron, germanium and aluminum in MFI zeolites under synthesis conditions that are more...

  15. High-silica zeolite nucleation from clear solutions

    E-print Network

    Cheng, Chil-Hung

    2006-04-12

    . This work initially tried to apply the insights developed from the TPAsilicalite- 1 clear solution synthesis by investigating the nanoparticles formation and zeolite growth in several tetraethyl orthosilicate (TEOS)-organocation-water solutions heated at 368...

  16. Investigation of Zeolite Nucleation and Growth Using NMR Spectroscopy 

    E-print Network

    Rivas Cardona, Alejandra

    2012-02-14

    and control of the zeolite properties. The primary objective of this dissertation is to determine the strength of organicinorganic interactions (i.e., the adsorption Gibbs energy) in transparent synthesis mixtures using PFG NMR spectroscopy, in order...

  17. Hydrogen Adsorption in Zeolite Studied with Sievert and Thermogravimetric Methods

    NASA Astrophysics Data System (ADS)

    Lesnicenoks, P.; Sivars, A.; Grinberga, L.; Kleperis, J.

    2012-08-01

    Natural clinoptilolite (mixture from clinoptilolite, quartz and muscovite) is activated with palladium and tested for hydrogen adsorption capability at temperatures RT - 200°C. Thermogravimetric and volumetric methods showed that zeolite activated with palladium (1.25%wt) shows markedly high hydrogen adsorption capacity - up to 3 wt%. Lower amount of adsorbed hydrogen (~1.5 wt%) was found for raw zeolite and activated with higher amount of palladium sample. Hypothesis is proposed that the heating of zeolite in argon atmosphere forms and activates the pore structure in zeolite material, where hydrogen encapsulation (trapping) is believed to occur when cooling down to room temperature. An effect of catalyst (Pd) on hydrogen sorption capability is explained by spillover phenomena were less-porous fractions of natural clinoptilolite sample (quartz and muscovite) are involved.

  18. High-silica zeolite nucleation from clear solutions 

    E-print Network

    Cheng, Chil-Hung

    2006-04-12

    . This work initially tried to apply the insights developed from the TPAsilicalite- 1 clear solution synthesis by investigating the nanoparticles formation and zeolite growth in several tetraethyl orthosilicate (TEOS)-organocation-water solutions heated at 368...

  19. Theoretical models for NO decomposition in Cu-exchanged zeolites

    E-print Network

    Tsekov, R

    2015-01-01

    A unified description of the catalytic effect of Cu-exchanged zeolites is proposed for the decomposition of NO. A general expression for the rate constant of NO decomposition is obtained by assuming that the rate-determining step consists of the transferring of a single atom associated with breaking of the N-O bond. The analysis is performed on the base of the generalized Langevin equation and takes into account both the potential interactions in the system and the memory effects due to the zeolite vibrations. Two different mechanisms corresponding to monomolecular and bimolecular NO decomposition are discussed. The catalytic effect in the monomolecular mechanism is related to both the Cu+ ions and zeolite O-vacancies, while in the case of the bimolecular mechanism the zeolite contributes through dissipation only. The comparison of the theoretically calculated rate constants with experimental results reveals additional information about the geometric and energetic characteristics of the active centers and con...

  20. Adsorption of trichlorophenol on zeolite and adsorbent regeneration with ozone.

    PubMed

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

    2014-04-30

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

  1. Synthesis and characterization of zeolite-type materials: Germanates and zirconogermanates

    NASA Astrophysics Data System (ADS)

    Smith, Rebeca

    The great importance that zeolites have in the industry accounting for 40 billion US dollars a year to the petroleum cracking industry alone has attracted the interest of synthesizing and developing new crystalline microstructures. This work presents the unique structural properties of germanates, zeolite-type materials, by first reviewing five unique structure building units (SBUs) that include: 4=1 units, D4R units and large clusters with 7-, 9-, and 10-germanium atoms. Then, the work of the syntheses and characterization of different germanate structures is presented. The synthesis and characterization of four zirconogermanates constructed from the same cluster consisting of five tetrahedral germanium atoms and one zirconium atom in octahedral coordination is presented. The structures were prepared using different amines as structure directing agents (SDA); ASU-23 (using 1,4-bis(3-aminopropyl) consists of one layered structure, ASU-24 (using hexamethylenediamine) is a pillared layered structure with exceptionally low framework density (FD=8.48 metal atoms per nanometer cubed), ASU-25 and ASU-26 (using 1,3-diaminopropane and ethylenediamine respectively) have 3-dimensional (3D) frameworks. The layer germanate (ASU-22) is built from 7-germanium clusters. X-ray structural analysis [P6(3)cm, a =28.794(2), c=20.603(4), V=14793(3) (unit cell parameters are in angstroms, volume in angstroms cubed)] revealed that the framework exhibits the kagome (kgm) topology. The extensive series of syntheses demonstrated the key role played by HF in the condensation of the 7-germanium clusters (these clusters have not been synthesized without HF). The zirconogermanate, ASU-17, in the 1,4-diaminobutane-HF system, was synthesized as crystalline powder and identified in the cubic crystals system with space group Ia-3d and unit cell parameter a =51.3 (angstroms) and corresponds to the SU-M structure reported by a group in Sweden. Exploratory work leading to the discovery this 3D cubic framework built from 10-germanium clusters showing pore size reaching the mesoporous range is presented. The synthesis and characterization of ASU-21, a crystalline germanate displaying large rigid cylinders, was also synthesized in the presence of hexamethylenediamine. The single crystal X-ray analysis [Ibam, a=49.257(10), b=28.439(6), c=14.866(3), V=20825(7) (unit cell parameters in angstroms and volume in angtrom cubed)] revealed the novel open-framework built form the same 10-germanium clusters found in ASU-17.

  2. Non-bridging Oxygen and Five-coordinated Aluminum in Aluminosilicate Glasses: A Cation Field Strength Study

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    Linda M. Thompson Jonathan F. Stebbins Dept. of Geological and Environmental Sciences, Stanford University, Stanford CA 94305 Although it is understood in aluminosilicate melts and glasses that non-bridging oxygens (NBO) have significant influence on thermodynamic and transport properties, questions remain about its role and the extent of its influence, particularly in metaluminous and peraluminous compositions. One major question persists regarding whether the formation of NBO is in any way coupled with the formation of VAl (AlO5), which is significantly impacted by cation field strength (defined as the cation charge divided by the square of the distance between the cation and oxygen atoms) (Kelsey et al., 2009). Previous work on calcium and potassium aluminosilicate glasses has shown the presence of NBO on the metaluminous join and persisting into the peraluminous region, with significantly more NBO present in Ca glasses compared to K glasses of similar composition (Thompson and Stebbins, 2011). However, it is unclear if there is any systematic impact on NBO content by cation field strength similar to the impact on VAl. Expanding on the previous study, barium aluminosilicate glasses were synthesized covering a range of compositions crossing the metaluminous (e.g. BaAl2O4-SiO2) join to observe changes in the NBO for comparison against the calcium aluminosilicate glasses, thus looking at the impact of cation size on NBO versus cation charge. In the barium glasses on the 30 mol% SiO2 isopleth, the highest NBO content was 6.9% for the barium rich glass (R = 0.51, where R is Ba2+ / (Ba2+ + 2Al3+)) while the most peraluminous glass (R = 0.45) had an NBO content of 1.9%. Comparison of these results to earlier data shows these numbers are similar to what is observed in the Ca glasses, indicating cation size alone does not have a significant impact on NBO content. However the VAl content does show a decrease (compared to calcium aluminosilicate glasses at similar R values and Si/Al ratios) with decreasing cation field strength. This suggests that the NBO content is much less sensitive to the cation size than the VAl content and indicates that NBO formation across the metaluminous join cannot be completely explained by linking VAl and NBO but that independent mechanisms of formation must exist. Temperature studies are ongoing to offer additional insight into the relationship between VAl and NBO.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  4. Removal of dilute benzene using zeolite-hybrid plasma reactor

    Microsoft Academic Search

    Atsushi OGATA; Daisuke Ito; Koichi MIZUNO; Satoshi KUSHIYAMA; Toshiaki YAMAMOTO

    1999-01-01

    The decomposition of benzene was carried out using a plasma reactor packed with a mixture of BaTiO3 and zeolite pellets, the zeolite-hybrid reactor. The reactor performance was characterized by measuring COx formed during plasma discharge and COx adsorbed on the solid surface. The decomposition efficiency of benzene in the hybrid reactor was 1.4 to 2.1 times higher than that in

  5. Simulating Microwave-Heated Diffusion in Zeolite Nanopores

    Microsoft Academic Search

    Cristian Blanco; Scott M. Auerbach

    We have performed equilibrium molecular dynamics and microwave (MW) heated molecular dynamics simulations to explore how MW heating influences self-diffusion in zeolite nanopores. We have applied these simulations to methanol and\\/or benzene in de-aluminated Y zeolite. We have found that even under the non-equilibrium conditions of MW heating, center-of-mass motions can be associated with effective temperatures. However, we find that

  6. The safety of synthetic zeolites used in detergents

    Microsoft Academic Search

    Claudia Fruijtier-Pölloth

    2009-01-01

    Synthetic zeolites are replacing phosphates as builders in laundry detergents; workers and consumers may, therefore, increasingly\\u000a be exposed to these materials and it is important to assess their safety. This article puts mechanistic, toxicological and\\u000a exposure data into context for a safety assessment. Zeolites are hygroscopic compounds with ion-exchanging properties. They\\u000a may partially decompose under acidic conditions such as in

  7. Tribomechanical micronization and activation of whey protein concentrate and zeolite

    Microsoft Academic Search

    Z. Herceg; V. Lelas; M. Brn?i?; B. Tripalo; D. Jezek

    2004-01-01

    Tribomechanics is a part of physics that is concerned with the study of phenomena that appear during milling under dynamic\\u000a conditions. Tribomechanical micronization and activation (TMA) of whey protein concentrates (WPC) and zeolites (type clinoptilolite)\\u000a were carried out. Samples of powdered WPC and zeolite were treated with the laboratory TMA equipment. The treatment was carried\\u000a out at two various rotor

  8. Metal Oxide/Zeolite Combination Absorbs H2S

    NASA Technical Reports Server (NTRS)

    Voecks, Gerald E.; Sharma, Pramod K.

    1989-01-01

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

  9. Synthesis and characterization of an offretite\\/erionite type zeolite

    Microsoft Academic Search

    Sanyuan Yang; N. P. Evmiridis

    1996-01-01

    A novel method is described for the preparation of offretite\\/erionite type zeolites without use of nitrogen-containing templates. It is based on the introduction of a certain amount of potassium ions into a synthesis system leading to the formation of an omega type zeolite. The synthesized product is characterized by X-ray diffraction and scanning electron microscopy and is identified as a

  10. Transport of C 6 isomers through ZSM-5 zeolite membranes

    Microsoft Academic Search

    Stefan Sommer; Thomas Melin; John L. Falconer; Richard D. Noble

    2003-01-01

    The separation of binary mixtures of hexane isomers using ZSM-5 zeolite membranes on porous stainless steel and alumina tubes was modeled for both vapor permeation and pervaporation. The fluxes and selectivities for single-component and mixture permeation of n-hexane, 3-methylpentane (3-MP), and 2,2-dimethylbutane (DMB) were described by combining two diffusion mechanisms. The flux through zeolite pores was modeled by Maxwell–Stefan diffusion

  11. High resolution argon adsorption isotherms for various zeolites

    Microsoft Academic Search

    K. Nakai; J. Sonoda; M. Yoshida; M. Hakuman; H. Naono

    2007-01-01

    Ar isotherms (87.3 K) and N2 isotherms (77.4 K) were measured for two silicas with different silanol content and two MFI zeolites with different alumina (proton) content. Silanols or protons give the significant effect on 2 isotherms, but has little influence on Ar isotherms. Ar isotherms for seven zeolites of various micropore size were measured in the pressure range of

  12. Pd–Zeolites as Heterogeneous Catalysts in Heck Chemistry

    Microsoft Academic Search

    M. Dams; L. Drijkoningen; B. Pauwels; G. Van Tendeloo; D. E. De Vos; P. A. Jacobs

    2002-01-01

    Heck reactions were performed with 4-bromoacetophenone and n-butyl acrylate, yielding the trans-arylated acrylate ester with high selectivity. Pd–zeolite catalysts were compared with supported Pd metal catalysts. In order to obtain an active and heterogeneous catalyst, the preformed or in situ-formed catalytically active Pd0 species and the PdII intermediates must be sufficiently stabilized on the zeolites against leaching and against aggregation

  13. Cadmium adsorption on vermiculite, zeolite and pumice: Batch experimental studies

    Microsoft Academic Search

    Maria Rosaria Panuccio; Agostino Sorgonà; Marcella Rizzo; Giovanni Cacco

    2009-01-01

    Batch experiments were performed to evaluate the combined effects of ionic activity, pH, and contact time on the cadmium sorption in three different minerals, vermiculite, zeolite, and pumice, commonly employed as substrata in nurseries and recently considered for their potential use in remediation methods. The extent of cadmium sorption was vermiculite>zeolite>pumice, as shown by the Langmuir and Freundlich parameters, and

  14. Lightweight and Thermal Blocks from Zeolites as Aggregated

    Microsoft Academic Search

    G. T. Munive; A. L. Leal-Cruz; M. I. Pech-Canul; J. A. Rodríguez-García; E. Rocha-Rangel

    2011-01-01

    The present research is focused on the design of mixtures containing zeolite (Z), as an alternative aggregate and their use in the production of blocks with lightweight and insulating properties that comply with the specific requirements of standards for its application in construction. To improve lightweight and insulating properties in blocks, first mixtures zeolitic sand-cement-lime (ZS\\/C\\/L) were prepared and their

  15. Influence of synthetic sodium aluminosilicate on laying hens fed different phosphorus levels.

    PubMed

    Fethiere, R; Miles, R D; Harms, R H

    1990-12-01

    Two 28-day experiments were conducted utilizing 360 and 180 Leghorn-type hens, 60 and 40 wk of age in Experiments 1 and 2, respectively. In both experiments, a corn-soybean meal basal diet containing no supplemental P was formulated. Dicalcium phosphate was added to the basal diet to supply 0, .05, and .13% supplemental P in Experiment 1 and 0, .13, and .35% supplemental P in Experiment 2. In both experiments, diets were fed with 0 and .75% synthetic sodium aluminosilicate (SAS). The basal diet was calculated to contain .30% P. In Experiment 1, egg production was significantly increased by the addition of .13% supplemental P. When SAS was added to each diet, a decline in egg production and feed consumption was observed. Egg specific gravity increased and egg weight decreased in the presence of SAS. In Experiment 2, egg production was significantly depressed by SAS in the absence of supplemental P and returned to normal with supplemental P. Feed consumption was significantly depressed by adding SAS to diets containing 0 to .13% supplemental P but not to diets containing .35% supplemental P. Egg weight decreased and specific gravity increased when SAS was supplemented to the diet. Data from these two experiments indicate that adequate P intake is advised when using SAS because feed consumption, egg production, and egg weight were decreased in the presence of SAS. PMID:1964737

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

    PubMed

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

    2010-11-01

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

  17. Retention of monodisperse or polydisperse aluminosilicate particles inhaled by dogs, rats, and mice

    SciTech Connect

    Snipes, M.B.; Boecker, B.B.; McClellan, R.O.

    1983-07-01

    This study compared long-term retention of /sup 134/Cs-labeled fused aluminosilicate particles inhaled by three animal species. Dogs, rats, and mice were briefly exposed to 0.7-, 1.5-, or 2.8-micron activity median aerodynamic diameter (AMAD) monodisperse particles or a polydisperse aerosol with 1.5 to 2.0 micron AMAD and geometric standard deviation of 1.5 to 2.0. Tissues and excreta were collected for up to 850 days after exposure to determine retention and clearance patterns of the inhaled particles. Simulation models were developed for each animal species and aerosol. Solubilization was the dominant factor in long-term lung clearance for most of the particles inhaled by dogs; mechanical clearance was dominant in rats and mice. After accounting for solubility, physical clearance from the lung to the gastrointestinal tract and to lung-associated lymph nodes (LALNs) was independent of particle size within the size range investigated. Rats and mice demonstrated a rapid clearance from the pulmonary region, with most of the mechanically cleared particles going to the gastrointestinal tract; significant translocation to the LALNs occurred for only a few days. The dogs cleared deposited particles at a slower rate, with most of the long-term clearance going to LALNs. A small portion of the initial deposit was retained in the upper respiratory tract of all three species. Results from the data for dogs were used to make long-term predictions for chronic inhalation of particles by humans.

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

    SciTech Connect

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

    2011-06-01

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

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

    NASA Astrophysics Data System (ADS)

    Borrell, Amparo; García-Moreno, Olga; Torrecillas, Ramón; García-Rocha, Victoria; Fernández, Adolfo

    2012-02-01

    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 properties are achieved by the addition of one or two more phases. The main scope of this work is to study the sinterability of carbon nanofiber (CNFs)/LAS and CNFs/alumina/LAS nanocomposites, and to adjust the ratio among components for obtaining a near-zero or tailored thermal expansion. Spark plasma sintering of nanocomposites, consisting of commercial CNFs and alumina powders and an ad hoc synthesized ?-eucryptite phase, is proposed as a solution to improving mechanical and electrical properties compared with the LAS ceramics obtained under the same conditions. X-ray diffraction results on phase compositions and microstructure are discussed together with dilatometry data obtained in a wide temperature range (-150 to 450 °C). The use of a ceramic LAS phase makes it possible to design a nanocomposite with a very low or tailored thermal expansion coefficient and exceptional electrical and mechanical properties.

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

    SciTech Connect

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

    1995-12-01

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

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

    SciTech Connect

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

    2012-09-15

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

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

    SciTech Connect

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

    2003-02-20

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

  3. Moderate-temperature zeolitic alteration in a cooling pyroclastic deposit

    USGS Publications Warehouse

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

    1989-01-01

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

  4. Nanosized zeolites as a perspective material for conductometric biosensors creation

    NASA Astrophysics Data System (ADS)

    Kucherenko, Ivan; Soldatkin, Oleksandr; Kasap, Berna Ozansoy; Kirdeciler, Salih Kaan; Kurc, Burcu Akata; Jaffrezic-Renault, Nicole; Soldatkin, Alexei; Lagarde, Florence; Dzyadevych, Sergei

    2015-05-01

    In this work, the method of enzyme adsorption on different zeolites and mesoporous silica spheres (MSS) was investigated for the creation of conductometric biosensors. The conductometric transducers consisted of gold interdigitated electrodes were placed on the ceramic support. The transducers were modified with zeolites and MSS, and then the enzymes were adsorbed on the transducer surface. Different methods of zeolite attachment to the transducer surface were used; drop coating with heating to 200°C turned out to be the best one. Nanozeolites beta and L, zeolite L, MSS, and silicalite-1 (80 to 450 nm) were tested as the adsorbents for enzyme urease. The biosensors with all tested particles except zeolite L had good analytical characteristics. Silicalite-1 (450 nm) was also used for adsorption of glucose oxidase, acetylcholinesterase, and butyrylcholinesterase. The glucose and acetylcholine biosensors were successfully created, whereas butyrylcholinesterase was not adsorbed on silicalite-1. The enzyme adsorption on zeolites and MSS is simple, quick, well reproducible, does not require use of toxic compounds, and therefore can be recommended for the development of biosensors when these advantages are especially important.

  5. Nanocellulose-Zeolite Composite Films for Odor Elimination.

    PubMed

    Keshavarzi, Neda; Mashayekhy Rad, Farshid; Mace, Amber; Ansari, Farhan; Akhtar, Farid; Nilsson, Ulrika; Berglund, Lars; Bergström, Lennart

    2015-07-01

    Free standing and strong odor-removing composite films of cellulose nanofibrils (CNF) with a high content of nanoporous zeolite adsorbents have been colloidally processed. Thermogravimetric desorption analysis (TGA) and infrared spectroscopy combined with computational simulations showed that commercially available silicalite-1 and ZSM-5 have a high affinity and uptake of volatile odors like ethanethiol and propanethiol, also in the presence of water. The simulations showed that propanethiol has a higher affinity, up to 16%, to the two zeolites compared with ethanethiol. Highly flexible and strong free-standing zeolite-CNF films with an adsorbent loading of 89 w/w% have been produced by Ca-induced gelation and vacuum filtration. The CNF-network controls the strength of the composite films and 100 ?m thick zeolite-CNF films with a CNF content of less than 10 vol % displayed a tensile strength approaching 10 MPa. Headspace solid phase microextraction (SPME) coupled to gas chromatography-mass spectroscopy (GC/MS) analysis showed that the CNF-zeolite films can eliminate the volatile thiol-based odors to concentrations below the detection ability of the human olfactory system. Odor removing zeolite-cellulose nanofibril films could enable improved transport and storage of fruits and vegetables rich in odors, for example, onion and the tasty but foul-smelling South-East Asian Durian fruit. PMID:26061093

  6. Asymmetric printing of molecules and zeolites on self assembled monolayers

    NASA Astrophysics Data System (ADS)

    Kehr, Nermin Seda; Schäfer, Andreas; Ravoo, Bart Jan; de Cola, Luisa

    2010-04-01

    Microcontact printing (mCP) is used to immobilize dyes and peptides asymmetrically, by a ``peptide coupling'' reaction, on monolayers of zeolite L crystals in the contact area between the stamp and the surface of the monolayer. Chemically patterned surfaces of monolayers of zeolite L crystals are obtained by using patterned stamps with different ink solutions. Additional printing of functionalized nano-objects on SAMs of zeolite L crystals is demonstrated.Microcontact printing (mCP) is used to immobilize dyes and peptides asymmetrically, by a ``peptide coupling'' reaction, on monolayers of zeolite L crystals in the contact area between the stamp and the surface of the monolayer. Chemically patterned surfaces of monolayers of zeolite L crystals are obtained by using patterned stamps with different ink solutions. Additional printing of functionalized nano-objects on SAMs of zeolite L crystals is demonstrated. Electronic supplementary information (ESI) available: Details of XPS spectra are given. See DOI: 10.1039/b9nr00285e

  7. Removal of metal cations from water using zeolites

    SciTech Connect

    Zamzow, M.J.; Murphy, J.E. (U.S. Bureau of Mines, Reno, NV (United States))

    1992-11-01

    Zeolites from abundant natural deposits were investigated by the Bureau of Mines for efficiently cleaning up mining industry wastewaters. Twenty-four zeolite samples were analyzed by x-ray diffraction and inductively coupled plasma. These included clinoptilolite, mordenite, chabazite, erionite, and phillipsite. Bulk densities of a sized fraction ([minus]40, +65 mesh) varied from 0.48 to 0.93 g/ml. Attrition losses ranged from 1 to 18% during an hour-long shake test. The 24 zeolites and an ion-exchange resin were tested for the uptake of Cd, Cu, and Zn. Of the natural zeolites, phillipsite proved to be the most efficient, while the mordenites had the lowest uptakes. Sodium was the most effective exchangeable ion for exchange of heavy metals. Wastewater from an abandoned copper mine in Nevada was used to test the effectiveness of clinoptilolite for treating a multi-ion wastewater. The metal ions Fe[sup 3+], Cu[sup 2+], and Zn[sup 2+] in the copper mine wastewater were removed to below drinking water standards, but Mn[sup 2+] and Ni[sup 2+] were not. Calcium and NH[sub 4][sup +] interfered with the uptake of heavy metals. Adsorbed heavy metals were eluted from zeolites with a 3% NaCl solution. Heavy metals were concentrated in the eluates up to 30-fold relative to the waste solution. Anions were not adsorbed by the zeolites.

  8. Solvent Evaporation Assisted Preparation of Oriented Nanocrystalline Mesoporous MFI Zeolites

    SciTech Connect

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

    2011-07-01

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

  9. Photocatalyzed oxidation of hydrocarbons in zeolite cages

    SciTech Connect

    Frei, H.; Blatter, F.; Sun, H. [Lawrence Berkeley National Lab., CA (United States)

    1996-06-01

    Oxidation of hydrocarbons by molecular oxygen is a key process in chemical industry. But reactions that use O{sub 2} as the primary oxidant often produce large amounts of unwanted byproducts. One major reason that selectivities are low is that the desired products (such as alcohols or carbonyls) are more easily oxidized by O{sub 2} than the parent hydrocarbon. The authors recently discovered a simple method that gives partial oxidation of small alkenes, alkanes, and alkyl-substituted benzenes by O{sub 2} at unprecedented selectivity, even at high conversion of the hydrocarbon. The approach is based on visible light-induced chemistry of hydrocarbon-O{sub 2} collisional pairs in the cages of large-pore zeolites. Reactions are conducted at ambient temperature in the absence of solvent or photosensitizer. Here the authors describe the most interesting reactions established thus far and define issues that pertain to scale-up of the method.

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

    SciTech Connect

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

    1990-12-01

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

  11. Adsorption and isothermal models of atrazine by zeolite prepared from Egyptian kaolin

    NASA Astrophysics Data System (ADS)

    Jamil, Tarek S.; Gad-Allah, Tarek A.; Ibrahim, Hanan S.; Saleh, Tamer S.

    2011-01-01

    The adsorption behavior of Atrazine on zeolites, prepared from Egyptian kaolin, has been studied in order to consider the application of these types of zeolites in water purification. The batch mode has been employed, using atrazine solution of concentration ranging from 2 to 10 mg /l. The adsorption capacity and distribution coefficients ( Kd) were determined for the adsorption system as a function of sorbate concentration. It was found that, under the studies concentrations, the percent of adsorbed atrazine on both zeolites match to Langmuir and Freundlich adsorption models. The constants of each model were calculated to assess the adsorption behavior of atrazine on each type of zeolite. According to the equilibrium studies, adsorption of atrazine on zeolite X at lower concentrations is much better than that on zeolite A. The application of Dublin-Kaganer-Radushkevich model revealed physisorption endothermic adsorption process for both zeolites. These results show that natural zeolites hold great potential to remove hazardous materials such as atrazine from water.

  12. Alkali metal crystalline polymer electrolytes.

    PubMed

    Zhang, Chuhong; Gamble, Stephen; Ainsworth, David; Slawin, Alexandra M Z; Andreev, Yuri G; Bruce, Peter G

    2009-07-01

    Polymer electrolytes have been studied extensively because uniquely they combine ionic conductivity with solid yet flexible mechanical properties, rendering them important for all-solid-state devices including batteries, electrochromic displays and smart windows. For some 30 years, ionic conductivity in polymers was considered to occur only in the amorphous state above Tg. Crystalline polymers were believed to be insulators. This changed with the discovery of Li(+) conductivity in crystalline poly(ethylene oxide)(6):LiAsF(6). However, new crystalline polymer electrolytes have proved elusive, questioning whether the 6:1 complex has particular structural features making it a unique exception to the rule that only amorphous polymers conduct. Here, we demonstrate that ionic conductivity in crystalline polymers is not unique to the 6:1 complex by reporting several new crystalline polymer electrolytes containing different alkali metal salts (Na(+), K(+) and Rb(+)), including the best conductor poly(ethylene oxide)(8):NaAsF(6) discovered so far, with a conductivity 1.5 orders of magnitude higher than poly(ethylene oxide)(6):LiAsF(6). These are the first crystalline polymer electrolytes with a different composition and structures to that of the 6:1 Li(+) complex. PMID:19543313

  13. Alkali metal crystalline polymer electrolytes

    NASA Astrophysics Data System (ADS)

    Zhang, Chuhong; Gamble, Stephen; Ainsworth, David; Slawin, Alexandra M. Z.; Andreev, Yuri G.; Bruce, Peter G.

    2009-07-01

    Polymer electrolytes have been studied extensively because uniquely they combine ionic conductivity with solid yet flexible mechanical properties, rendering them important for all-solid-state devices including batteries, electrochromic displays and smart windows. For some 30 years, ionic conductivity in polymers was considered to occur only in the amorphous state above Tg. Crystalline polymers were believed to be insulators. This changed with the discovery of Li+ conductivity in crystalline poly(ethylene oxide)6:LiAsF6 (refs 4, 5). However, new crystalline polymer electrolytes have proved elusive, questioning whether the 6:1 complex has particular structural features making it a unique exception to the rule that only amorphous polymers conduct. Here, we demonstrate that ionic conductivity in crystalline polymers is not unique to the 6:1 complex by reporting several new crystalline polymer electrolytes containing different alkali metal salts (Na+, K+ and Rb+), including the best conductor poly(ethylene oxide)8:NaAsF6 discovered so far, with a conductivity 1.5 orders of magnitude higher than poly(ethylene oxide)6:LiAsF6. These are the first crystalline polymer electrolytes with a different composition and structures to that of the 6:1 Li+ complex.

  14. Adsorption properties of Fe-containing dealuminated BEA zeolites as revealed by FTIR spectroscopy

    Microsoft Academic Search

    Konstantin Hadjiivanov; Elena Ivanova; Radoslav Kefirov; Janusz Janas; Anna Plesniar; Stanislaw Dzwigaj; Michel Che

    2010-01-01

    Adsorption properties of Fe-containing dealuminated BEA zeolites were investigated by FTIR spectroscopy of adsorbed CO and NO. Two Fe-containing SiBEA zeolite samples were prepared by a two-step post-synthesis method: creation of vacant T-atom sites (T=Si, Al) by dealumination of tetraethylammonium BEA zeolite with nitric acid followed by impregnation of the resulting SiBEA zeolite with an aqueous solution of Fe(NO3)3. The

  15. Removal of organobromine compounds from the pyrolysis oils of flame retarded plastics using zeolite catalysts

    Microsoft Academic Search

    William J. Hall; Paul T. Williams

    2008-01-01

    Two flame retarded plastics have been pyrolysed in the presence of two zeolite catalysts to remove the organobromine compounds from the derived pyrolysis oil. The flame retarded plastics were, acrylonitrile–butadiene–styrene (ABS) that was flame retarded with tetrabromobisphenol A and high impact polystyrene (HIPS) that was flame retarded with decabromodiphenyl ether. The two catalysts investigated were zeolite ZSM-5 and zeolite Y-Zeolite.

  16. Highly dispersed metal atoms in zeolites. Progress report. [Hydroformylation

    SciTech Connect

    Suib, S.L.

    1985-04-15

    Our studies this past year have involved work in the following areas: preparation of highly dispersed metal atoms in molecular sieves via microwave discharge methods, hydroformylation of l-pentene with rhodium zeolites and Rutherford backscattering studies of zeolites. The microwave discharge method has been developed by us to provide a synthetic route to produce highly dispersed iron and cobalt atom clusters in several molecular sieves such as zeolites, aluminophosphates, pillared clays and clays. We have done ferromagnetic resonance, infrared, Mossbauer and scanning electron microscopy experiments on these materials. Generalizations that can be made so far are that these particles are extremely small, reactive and their formation is governed by the type of support. They are all active in Fischer-Tropsch reactions although cobalt materials are more selective and stable than iron materials. Superparamagnetic iron clusters have been observed for the incorporation of iron into zeolites, ALPO's and pillared clays. These results are unique in that iron (0) is usually oxidized in a zeolite environment. The second project deals with Wilkinson's catalyst and the preparation of phosphine rhodium zeolite catalysts. These catalysts are selective towards aldehyde formation and the normal to branched aldehyde ratio can be controlled. EXAFS, Fourier transform infrared and x-ray powder diffraction experiments have been carried out on these catalysts. The third project deals with Rutherford backscattering studies of zeolites. We have shown that Rutherford backscattering methods can be used to distinguish metal ions on the surface of a porous support from internal metal ions exchanged into the pores of the support.

  17. The role of zeolite beta nanoparticles solutions in the synthesis of zeolite-functionalised materials with bimodal porosity

    NASA Astrophysics Data System (ADS)

    Van Oers, Cynthia J.

    The last decade, much attention has been devoted to the development of bimodal materials with zeolitic properties, with the intention to combine the beneficial properties of zeolites with these of mesoporous structures. Various synthesis methods have been developed, of which several are using zeolite nanoparticles solutions as silica-alumina source to form the mesoporous material. Extensive research has been conducted to the properties and the formation mechanism of both the nanoparticles solution and the final bimodal materials. However, still little is known about the correlation between the characteristics of the initial nanoparticles solution and the structural, chemical and physico-chemical properties of the final materials. The focus of this research is to acquire this lacking knowledge, which would allow tailoring of the final material characteristics, depending on the application requirements. In this PhD work, two types of bimodal materials with zeolitic features are investigated, i.e. a mesotemplate-free method and an impregnation on a mesoporous substrate, both using a zeolite beta nanoparticles solution as precursor. The main focus is put on how the synthesis conditions of the zeolite beta nanoparticles solution influence the final material properties. It is shown that the hydrothermal synthesis temperature (373K--393K--413K--423K/24h) of the zeolite beta nanoparticles solution has a direct impact on the porosity and zeolitic features of the final materials. Moreover, a clear threshold is observed: Synthesis temperatures below or equal to 413K result in bimodal materials without clear zeolitic properties, while a higher temperature of 423K gives materials with clear zeolitic features. Furthermore, this difference in material properties gives better results for the materials above the threshold regarding the acidity, stability and catalytic activity. A transmission electron microscopy and advanced electron tomography study showed that the mesotemplate-free structures are possessing a wormhole-like mesoporous structure, formed by the condensation of nanoparticles via neck formation. Furthermore, the study revealed a 2D growth of the nanoparticles under the threshold and a change towards 3D growth at the threshold temperature of 413K. This suggests a standard sol-mechanism below and at the threshold, and indicates an interruption of this mechanism by the start of the crystallisation process above 413K.

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1994-09-01

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

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

    PubMed

    Bonelli, Barbara; Armandi, Marco; Garrone, Edoardo

    2013-08-28

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

  1. Fast dynamics of H2 O in hydrous aluminosilicate glasses studied with quasielastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Indris, Sylvio; Heitjans, Paul; Behrens, Harald; Zorn, Reiner; Frick, Bernhard

    2005-02-01

    We studied the dynamics of dissolved water in aluminosilicate glasses with the compositions NaAlSi3O8·0.3H2O , NaAlSi3O8·1.3H2O and Ca0.5AlSi3O8·1.3H2O using quasielastic neutron scattering. As shown by near-infrared spectroscopy on these samples, H2O molecules are the predominant hydrous species in the water-rich glasses whereas OH groups bound to tetrahedrally coordinated cations are predominant at low water contents. Backscattering and time-of-flight methods were combined to investigate motional correlation times in the range between 0.2ps and 2ns . For the water-rich glasses an elastic scan between 2K and 420K shows that the dynamical processes set in at lower temperatures in the Ca -bearing glass than in the Na -bearing glass. This is corroborated by the broadening of the inelastic spectra S(Q,?) . The shape of the scattering function S(Q,t) suggests a distribution of activation barriers for the motion of hydrous species in the disordered structure of the glass. The distribution is narrower and the average activation energy is smaller in the Ca -bearing glass than in the Na -bearing glass. No indication for dynamics of hydrous species was found at temperatures up to 520K in the water-poor glass NaAlSi3O8·0.3H2O containing dissolved water mainly in the form of OH groups. It is concluded that H2O molecules are the dynamic species in the above-mentioned time regime in the water-rich glasses. The dynamic process is probably a rotation of H2O molecules around their bisector axis.

  2. Studies on catalytic cracking catalyst of hydrocarbons with a new type of zeolite L

    Microsoft Academic Search

    Huifang Pan; Guoyou Wei; Hailiang Yuan; Quan Huo; Qiang Li; Xinghong Pan; Wenhong Wang; Xiangzhen Yu

    2007-01-01

    A new catalyst which exhibits superior activity, stability and selectivity in fluid catalytic cracking (FCC) reactions of hydrocarbons is defined as a new type of zeolite L, ultra stable zeolite L (USL), as an active additive component of catalyst. The zeolite L was synthesized by hydrothermal crystallization method and characterized by means of XRD, SEM, FTIR and N2 isotherm adsorption.

  3. Competitive adsorption of malachite green and Pb ions on natural zeolite

    Microsoft Academic Search

    Shaobin Wang; Eko Ariyanto

    2007-01-01

    A natural zeolite was employed as adsorbent for removal of malachite green and Pb2+ ions from aqueous solution. A batch system was applied to study the adsorption behaviour of the dye and heavy metal in single and binary systems on the natural zeolite. Kinetic studies indicate that malachite green and Pb2+ adsorption on the natural zeolite in a single component

  4. Dealumination–aging pattern of REUSY zeolites contained in fluid cracking catalysts

    Microsoft Academic Search

    Francisco Hernández-Beltrán; Juan Carlos Moreno-Mayorga; Mar??a de Lourdes Guzmán-Castillo; Juan Navarrete-Bolaños; Montserrat González-González; Brent E. Handy

    2003-01-01

    The evolution of the properties of a REUSY zeolite contained in a fluid cracking catalyst was investigated under laboratory steam deactivation procedures and in age fractions of the corresponding equilibrium catalyst (Ecat). The aging pattern, defined by the evolution of the zeolite surface area (ZSA) related to the decrease of the unit cell size (UCS), was similar between lab-steamed zeolites

  5. Thermal Conductivity in Zeolites Studied by Non-equilibrium Molecular Dynamics Simulations

    NASA Astrophysics Data System (ADS)

    Schnell, Sondre K.; Vlugt, Thijs J. H.

    2013-07-01

    The thermal conductivity of zeolites is an important material property. For example, this is the case for catalysis, where chemical reactions release heat either inside zeolites or at zeolite surfaces. At zeolite surfaces, heat is released during the adsorption of guest molecules. Unfortunately, it can be difficult to determine the thermal conductivity of zeolites from experiments or from equilibrium molecular dynamics simulations. Non-equilibrium molecular dynamics (NEMD) simulation is an interesting approach to determine thermal conductivities. Inducing a thermal gradient by moving kinetic energy between different parts of the simulation box, and then studying the resulting thermal gradient, will lead to direct access to the thermal conductivity of the zeolite. In this work, we have used NEMD simulations to determine the thermal conductivity of several pure silica zeolites. The zeolites are modeled using the Demontis force field, making it possible to screen many zeolite frameworks, and study finite-size effects. In addition, we have studied the influence of adsorbed guest molecules on the thermal conductivity. The thermal conductivity of zeolites is usually in order of 0.6 to almost 4 , with large differences between different crystallographic directions. We find that the loading of guest molecules adsorbed inside the zeolite has a minor influence on the thermal conductivity, and that in general the thermal conductivity increases with increasing framework density of the zeolite.

  6. Significant reduction of carcinogenic compounds in tobacco smoke by the use of zeolite catalysts

    Microsoft Academic Search

    W. M Meier; K Siegmann

    1999-01-01

    Zeolites play an increasingly important role in toxicology and the life sciences. A new example is the removal of significant amounts of carcinogenic compounds from cigarette smoke. These compounds, particularly nitrosamines and polycyclic aromatics (PAHs), are well known to constitute a serious health risk. Most effective in reducing toxic compounds are zeolite catalysts placed directly on the tobacco. The zeolite

  7. Strategies for total NOx measurement with minimal CO interference utilizing a microporous zeolitic catalytic filter

    E-print Network

    Dutta, Prabir K.

    at temperatures greater than 400 8C. By using a Pt-loaded zeolite Yas a catalyst filter bed placed before a sensor a layer of the Pt-zeolite catalyst filter material directly onto a Pt electrode, a pseudo-reference to NOxStrategies for total NOx measurement with minimal CO interference utilizing a microporous zeolitic

  8. Zeolite Membrane for Dehydration of Isopropylalcohol-Water Mixture by Vapor Permeation.

    PubMed

    Sawamura, Ken-Ichi; Furuhata, Taisuke; Sekine, Yasushi; Kikuchi, Eiichi; Subramanian, Bharathi; Matsukata, Masahiko

    2015-07-01

    Highly stable FAU-type zeolite membrane for the separation of isopropanol (IPA)-water mixture by pervaporation is described. FAU membrane showed high water permselectivity and permeance. Comparison of FAU membrane with a conventional LTA-type zeolite membrane revealed superior stability of FAU zeolite membrane in a mixture containing a large water content. PMID:26076213

  9. Role of acidity in hydrogenation of cinnamaldehyde on platinum beta zeolite

    Microsoft Academic Search

    Mohamed Lashdaf; Ville-Veikko Nieminen; Marja Tiitta; Tapani Venäläinen; Heidi Österholm; Outi Krause

    2004-01-01

    A series of platinum beta zeolites with different well-defined acid properties were tested in cinnamaldehyde hydrogenation. The acetal formation was found to be related to the amount of acid sites on the external surface of the zeolite. The acidity of the beta zeolite influenced the platinum dispersion, and the activity of the catalysts increased with total acidity of the beta

  10. Acidity and catalytic activity of zeolite catalysts bound with silica and alumina

    E-print Network

    Wu, Xianchun

    2004-09-30

    -framework alumina in zeolites to form a new protonic acid. SiO2-bound catalysts have less strong acidity, Bronsted acidity and Lewis acidity than the zeolite powder. Also, the strength of strong acid sites of the zeolites is reduced when silica is embedded...

  11. The structural stability of AlPO4-5 zeolite under pressure: Effect of the pressure transmission medium

    NASA Astrophysics Data System (ADS)

    Lv, Hang; Yao, Mingguang; Li, Quanjun; Liu, Ran; Liu, Bo; Lu, Shuangchen; Jiang, Linhai; Cui, Wen; Liu, Zhaodong; Liu, Jing; Chen, Zhiqiang; Zou, Bo; Cui, Tian; Liu, Bingbing

    2012-06-01

    The structural stability of AlPO4-5 zeolite (AFI) has been studied as a function of pressure up to 34.4 GPa in a diamond anvil cell by using synchrotron x-ray diffraction. It is found that the AFI structural stability can be enhanced significantly when a mixture of silicone oil and liquid nitrogen is used as pressure transmission medium (PTM). In this case, the crystalline-to-amorphous transition pressure for AFI increased to be 15.9 GPa, much higher than that of 8.5 GPa observed in the experiment by using silicone oil as PTM. We found that the average distance of the interplanar crystal spacing along to most planes was expanded obviously when liquid nitrogen is used as one component in the PTM. The presence of liquid nitrogen in the PTM also affects the structural evolution of the AFI channel under pressure. The results demonstrated that nitrogen molecules can be inserted into the channels of porous zeolite AFI single crystals, exerting a supporting effect against the structure collapse of AFI and thus improving their structural stability.

  12. Synthesis of nano-zeolite from coal fly ash and its potential for nutrient sequestration from anaerobically digested swine wastewater.

    PubMed

    Chen, Xiaoyan; Wendell, Khunjar; Zhu, Jun; Li, Jiangli; Yu, Xianxian; Zhang, Zhijian

    2012-04-01

    The treatment of anaerobically digested swine wastewater (ADSW) is problematic due to its high nutrient concentration. This study investigated the simultaneous sequestration of ammonium (N) and phosphate (P) from ADSW using nano-zeolites synthesized from fly ash (ZFA). The nanometer-scale crystalline structures plentiful of zeolite-NaP1 coating on ZFA particle increased the levels of specific surface area and cation exchange capacity at times of 40 and 104, compared to raw fly ash. Kinetic N and P sorption experiments with ZFA were well described by both the Langmuir and Freundlich models, suggesting the co-existence of homogeneous and heterogeneous sorption mechanisms. N and P removal efficiencies ranged from 41% to 95% and 75% to 98%, respectively, across a range of ZFA doses (from 0.25 to 8g/100ml). Collectively, application of the laboratory-synthesized ZFA can alleviate the nutrient loads in ADSW and therefore modify the ratio of N:P in wastewater beneficial for subsequent biological treatment. PMID:22330598

  13. Electrical behavior of aluminosilicate glass-ceramic sealants and their interaction with metallic solid oxide fuel cell interconnects

    Microsoft Academic Search

    Ashutosh Goel; Dilshat U. Tulyaganov; Vladislav V. Kharton; Aleksey A. Yaremchenko; José M. F. Ferreira

    2010-01-01

    A series of alkaline-earth aluminosilicate glass-ceramics (GCs) were appraised with respect to their suitability as sealants for solid oxide fuel cells (SOFCs). The parent composition with general formula Ca0.9MgAl0.1La0.1Si1.9O6 was modified with Cr2O3 and BaO. The addition of BaO led to a substantial decrease in the total electrical conductivity of the GCs, thus improving their insulating properties. BaO-containing GCs exhibited

  14. Development of glass-ceramics by sintering and crystallization of fine powders of calcium-magnesium-aluminosilicate glass

    Microsoft Academic Search

    D. U. Tulyaganov; M. J. Ribeiro; J. A. Labrincha

    2002-01-01

    Natural raw materials normally used in the ceramic and glass industry were studied for the production of calcium–magnesium–aluminosilicate glass or glass-ceramic materials. Sintering and crystallization processes of fine powders of parent glass with chemical composition (wt.%) 46.00 SiO2, 15.90 Al2O3, 1.20 Fe2O3, 0.42 TiO2, 23.50 CaO, 9.37 MgO, 0.04 Na2O, 0.98 K2O, 1.95 P2O5 and 0.35 CaF2 were studied. Crystallization

  15. Physical properties of Eu^3+ doped sodium magnesium alumino-silicate glasses studied by light scattering spectroscopy

    NASA Astrophysics Data System (ADS)

    Shen, Guoqing; Utegulov, Zhandos; Wicksted, James P.; Rahman, Abdur

    2001-03-01

    Brillouin scattering and absorption measurements on various Al and Na concentrations of Europium doped sodium magnesium alumino-silicate glasses (ESMAS) were performed to study the glass structures and optical properties of ESMAS. The linewidth, frequency shift, and intensity of Brillouin peaks were determined to calculate the phonon attenuation, elastic constants, photo-elastic coefficients, and the bond polarizability parameter. The parameters obtained from this study shows that the glass structures become more rigid and ionic with increasing Al content, while the glass structures show more ionic and less rigid with increasing Na concentration. The Judd-Ofelt intensity parameter, ?_6, obtained from absorption measurements agrees with the Brillouin scattering results.

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

    NASA Astrophysics Data System (ADS)

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

    2000-06-01

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

  17. Zeolites for the selective adsorption of sulfur hexafluoride.

    PubMed

    Matito-Martos, I; Álvarez-Ossorio, J; Gutiérrez-Sevillano, J J; Doblaré, M; Martin-Calvo, A; Calero, S

    2015-07-01

    Molecular simulations have been used to investigate at the molecular level the suitability of zeolites with different topology on the adsorption, diffusion and separation of a nitrogen-sulfur hexafluoride mixture containing the latter at low concentration. This mixture represents the best alternative for the sulfur hexafluoride in industry since it reduces the use of this powerful greenhouse gas. A variety of zeolites are tested with the aim to identify the best structure for the recycling of sulfur hexafluoride in order to avoid its emission to the atmosphere and to overcome the experimental difficulties of its handling. Even though all zeolites show preferential adsorption of sulfur hexafluoride, we identified local structural features that reduce the affinity for sulfur hexafluoride in zeolites such as MOR and EON, providing exclusive adsorption sites for nitrogen. Structures such as ASV and FER were initially considered as good candidates based on their adsorption features. However, they were further discarded based on their diffusion properties. Regarding operation conditions for separation, the range of pressure that spans from 3 × 10(2) to 3 × 10(3) kPa was identified as the optimal to obtain the highest adsorption loading and the largest SF6/N2 selectivity. Based on these findings, zeolites BEC, ITR, IWW, and SFG were selected as the most promising materials for this particular separation. PMID:26099734

  18. Bendable Zeolite Membranes: Synthesis and Improved Gas Separation Performance.

    PubMed

    Wang, Bo; Ho, W S Winston; Figueroa, Jose D; Dutta, Prabir K

    2015-06-23

    Separation and sequestration of CO2 emitted from fossil energy fueled electric generating units and industrial facilities will help in reducing anthropogenic CO2, thereby mitigating its adverse climate change effects. Membrane-based gas separation has the potential to meet the technical challenges of CO2 separation if high selectivity and permeance with low costs for large-scale manufacture are realized. Inorganic zeolite membranes in principle can have selectivity and permeance considerably higher than polymers. This paper presents a strategy for zeolite growth within the pores of a polymer support, with crystallization time of an hour. With a thin coating of 200-300 nm polydimethylsiloxane (PDMS) on the zeolite-polymer composite, transport data for CO2/N2 separation indicate separation factors of 35-45, with CO2 permeance between 1600 and 2200 GPU (1 GPU = 3.35 × 10(-10) mol/(m(2) s Pa)) using dry synthetic mixtures of CO2 and N2 at 25 °C. The synthesis process results in membranes that are highly reproducible toward transport measurements and exhibit long-term stability (3 days). Most importantly, these membranes because of the zeolite growth within the polymer support, as contrasted to conventional zeolite growth on top of a support, are mechanically flexible. PMID:26030505

  19. Removal of BTEX from produced water using tailored zeolites

    SciTech Connect

    Cadena, F. [New Mexico State Univ., Las Cruces, NM (United States)

    1995-12-31

    The exchangeable cations in four natural zeolites (Bowie, CH, Winston and Tilden) were replaced with organic cations (quaternary amines). Two types of organic cations were used to create an organophilic environment suitable for adsorption of single-ring aromatics from water: small organic cations and long- alkyl chain cations. Both types of organic cations displace the natural exchangeable cations in the zeolite during the modification process. An organic layer covers the external surface of the zeolite after the natural inorganic cations are replaced by organic molecules. Two different pollutant adsorption mechanisms are observed in organozeolites. The first mechanism is prevalent when the zeolites are modified with small organic cations. The steric properties of adsorbed compounds are controlled by the intermolecular distance between the organic cations in the first mechanism. Benzene can be preferentially removed from solution over closely-related compounds (toluene and o-xylene) when the distance between organic cations is sufficient to allow this simple planar pollutant to enter into the intermolecular organic gaps. However, intermolecular distances that are significantly smaller than the benzene molecule prevent access to the adsorption sites. Organozeolites with long intermolecular gaps produce insufficient organic-organic interactions to hold the pollutants onto the solid-organic matrix. The selective adsorption produced by small organic cations is benzene >> toluene > xylene. The second mechanism is exhibited by zeolites modified with long-alkyl chains.

  20. Zeolite thin film-coated fiber sensors based on Fabry-Perot interferometer for detection of chemical vapors

    NASA Astrophysics Data System (ADS)

    Ning, Xiangping; Zhao, Chunliu; Shi, Feifei; Kang, Juan

    2015-06-01

    A novel zeolite-coated fiber sensors for detection of volatile organic compounds (VOCs) based on the Fabry-Perot interferometer was proposed and demonstrated. The sensor comprised a polycrystalline silicalite thin film grown up on the cleaved end face of a standard single-mode fiber. The inline Fabry-Perot cavity was composed by the end face of the single-mode fiber and the thin film. The sensor device operated by measuring the interference signal, which was a function of the amount of chemical vapor adsorption in its crystalline micro porous structure. Experimental results showed that the proposed VOC sensor worked well and the sensitivities were 2.78×10-3 dB/ppm when the concentration ranged from 350 ppm to 2100 ppm and 1.23×10-3 dB/ppm when the concentration ranged from 2100 ppm to 5250 ppm.

  1. Molecular composites from liquid crystalline polymers and liquid crystalline thermosets

    SciTech Connect

    Benicewicz, B.C.; Douglas, E.P.; Hjelm, R.P. Jr.

    1993-07-01

    We propose a new approach to molecular composites. This approach uses a mixture of a liquid crystalline polymer and a liquid crystalline thermoset to enhance the miscibility. Preliminary neutron scattering data is presented on a system of short and long rod aromatic amides. The data is interpreted using the interpenetrating phase model of Debye and Bueche. The analysis indicates that the scattering is consistent with this model and shows a characteristic length scale in the range of 70 to 80 A. The intensity of the scattering is lower than calculated for the strong segregation limit, suggesting that there is some intermixing of the components.

  2. Rotationally Molded Liquid Crystalline Polymers

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  3. Diverse topics in crystalline beams

    SciTech Connect

    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

    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.

  4. Synthesis of chiral polymorph A-enriched zeolite Beta with an extremely concentrated fluoride route.

    PubMed

    Tong, Mingquan; Zhang, Daliang; Fan, Weibin; Xu, Jun; Zhu, Liangkui; Guo, Wen; Yan, Wenfu; Yu, Jihong; Qiu, Shilun; Wang, Jianguo; Deng, Feng; Xu, Ruren

    2015-01-01

    Chiral zeolitic materials with intrinsically chiral frameworks are highly desired because they can combine both shape selectivity and enantioselectivity. In the field of zeolite, the synthesis of chiral polymorph A of zeolite Beta or chiral polymorph A-enriched zeolite Beta is one of the biggest challenges. We demonstrate here a generalized extremely concentrated fluoride route for the synthesis of chiral polymorph A-enriched zeolite Beta in the presence of five achiral organic structure-directing agents. The polymorph A-enriched Ti-Beta shows a higher enantioselectivity for the asymmetric epoxidation of alkenes than the normal Ti-Beta. PMID:26096214

  5. Synthesis of chiral polymorph A-enriched zeolite Beta with an extremely concentrated fluoride route

    PubMed Central

    Tong, Mingquan; Zhang, Daliang; Fan, Weibin; Xu, Jun; Zhu, Liangkui; Guo, Wen; Yan, Wenfu; Yu, Jihong; Qiu, Shilun; Wang, Jianguo; Deng, Feng; Xu, Ruren

    2015-01-01

    Chiral zeolitic materials with intrinsically chiral frameworks are highly desired because they can combine both shape selectivity and enantioselectivity. In the field of zeolite, the synthesis of chiral polymorph A of zeolite Beta or chiral polymorph A-enriched zeolite Beta is one of the biggest challenges. We demonstrate here a generalized extremely concentrated fluoride route for the synthesis of chiral polymorph A-enriched zeolite Beta in the presence of five achiral organic structure-directing agents. The polymorph A-enriched Ti-Beta shows a higher enantioselectivity for the asymmetric epoxidation of alkenes than the normal Ti-Beta. PMID:26096214

  6. Synthetic Zeolites and Other Microporous Oxide Molecular Sieves

    NASA Astrophysics Data System (ADS)

    Sherman, John D.

    1999-03-01

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

  7. Safe trapping of Cs in heat-treated zeolite matrices

    NASA Astrophysics Data System (ADS)

    Bosch, P.; Caputo, D.; Liguori, B.; Colella, C.

    2004-01-01

    Cesium retention performances of two different natural zeolites (an Italian phillipsite-rich tuff and a Mexican erionite-rich tuff), pre-exchanged in Cs form and heat-treated, are compared. After thermal treatment at 1000 °C both zeolites satisfactorily retain Cs during back-exchange tests with NaCl solution or by a prolonged contact with distilled water. The different mechanisms of Cs encapsulation are elucidated. The Cs-exchanged phillipsite, a less siliceous and less heat-stable zeolite, tends to form pollucite on heating. Pollucite is a naturally occurring mineral phase which contains and irreversibly traps cesium. The Cs-exchanged erionite tends to form an amorphous phase on heating and Cs is immobilized through glass formation.

  8. Synthesis of self-pillared zeolite nanosheets by repetitive branching.

    PubMed

    Zhang, Xueyi; Liu, Dongxia; Xu, Dandan; Asahina, Shunsuke; Cychosz, Katie A; Agrawal, Kumar Varoon; Al Wahedi, Yasser; Bhan, Aditya; Al Hashimi, Saleh; Terasaki, Osamu; Thommes, Matthias; Tsapatsis, Michael

    2012-06-29

    Hierarchical zeolites are a class of microporous catalysts and adsorbents that also contain mesopores, which allow for fast transport of bulky molecules and thereby enable improved performance in petrochemical and biomass processing. We used repetitive branching during one-step hydrothermal crystal growth to synthesize a new hierarchical zeolite made of orthogonally connected microporous nanosheets. The nanosheets are 2 nanometers thick and contain a network of 0.5-nanometer micropores. The house-of-cards arrangement of the nanosheets creates a permanent network of 2- to 7-nanometer mesopores, which, along with the high external surface area and reduced micropore diffusion length, account for higher reaction rates for bulky molecules relative to those of other mesoporous and conventional MFI zeolites. PMID:22745424

  9. Single crystalline mesoporous silicon nanowires

    SciTech Connect

    Hochbaum, Allon; Dargas, Daniel; Hwang, Yun Jeong; Yang, Peidong

    2009-08-18

    Herein we demonstrate a novel electroless etching synthesis of monolithic, single-crystalline, mesoporous silicon nanowire arrays with a high surface area and luminescent properties consistent with conventional porous silicon materials. The photoluminescence of these nanowires suggest they are composed of crystalline silicon with small enough dimensions such that these arrays may be useful as photocatalytic substrates or active components of nanoscale optoelectronic devices. A better understanding of this electroless route to mesoporous silicon could lead to facile and general syntheses of different narrow bandgap semiconductor nanostructures for various applications.

  10. Single crystalline mesoporous silicon nanowires

    SciTech Connect

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

    2009-08-04

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

  11. Monodispersed Ultrafine Zeolite Crystal Particles by Microwave Hydrothermal Synthesis

    SciTech Connect

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

    2008-01-01

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

  12. Maximizing ammonium nitrogen removal from solution using different zeolites.

    PubMed

    Penn, Chad J; Warren, Jason G; Smith, Savannah

    2010-01-01

    Zeolite minerals are ideal for removing ammonium nitrogen (NH4(+)-N) from animal wastes, leachates, and industrial effluents. The objectives of this study were to compare NH4+ removal and kinetics among several commercially available zeolites under various conditions and determine if calorimetry could provide information regarding kinetics of NH4+ removal. Ammonium sorption onto potassium (K) saturated zeolites was compared using synthetic vs. natural swine effluent and with either traditional batch-shaken system or a "tea bag" approach in which zeolites were contained in a mesh sack and suspended in a solution of swine effluent. Ammonium sorption was measured at four retention times using a flow-through system, and the resulting heat response was measured using isothermal calorimetry. Ammonium removal was not significantly different in synthetic vs. natural swine effluent. Ammonium removal was lower in batch-stirred compared to batch-shaken systems, suggesting that diffusion between particles was rate-limiting in the former system. Flow-through cells possessing contact times > 100 s displayed greater NH4+ sorption than batch systems, suggesting that maintaining high NH4+ concentration in solution, removal of exchange products, and sufficient reaction time are critical to maximizing NH4+ removal by zeolites. Within 100 s after NH4+ addition, endothermic heat responses indicated that NH4(+)-K+ exchange had peaked; this was followed by significant heat rate reduction for 50 min. This confirmed findings of an initial fast NH4(+)-K+ exchange followed by a slower one and suggests the 100-s period of rapid reaction is an indicator of the minimum flow through retention time required to optimize NH4+ sorption to zeolites used in this study. PMID:20830934

  13. Novel modified zeolites for energy-efficient hydrocarbon separations.

    SciTech Connect

    Arruebo, Manuel (University of Colorado, Boulder, CO); Dong, Junhang; Anderson, Thomas (Burns and McDonnell, Kansas City, MO); Gu, Xuehong; Gray, Gary (Goodyear Chemical Company, Akron, OH); Bennett, Ron (Goodyear Chemical Company, Akron, OH); Nenoff, Tina Maria; Kartin, Mutlu; Johnson, Kaylynn (Goodyear Chemical Company, Akron, OH); Falconer, John (University of Colorado, Boulder, CO); Noble, Richard (University of Colorado, Boulder, CO)

    2006-11-01

    We present synthesis, characterization and testing results of our applied research project, which focuses on the effects of surface and skeletal modification of zeolites for significant enhancements in current hydrocarbon (HC) separations. Zeolites are commonly used by the chemical and petroleum industries as catalysts and ion-exchangers. They have high potential for separations owing to their unique pore structures and adsorption properties and their thermal, mechanical and chemical properties. Because of zeolites separation properties, low cost, and robustness in industrial process, they are natural choice for use as industrial adsorbents. This is a multidisciplinary effort to research, design, develop, engineer, and test new and improved materials for the separation of branched vs. linear organic molecules found in commercially important HC streams via adsorption based separations. The focus of this project was the surface and framework modification of the commercially available zeolites, while tuning the adsorption properties and the selectivities of the bulk and membrane separations. In particular, we are interested with our partners at Goodyear Chemical, on how to apply the modified zeolites to feedstock isoprene purification. For the characterization and the property measurements of the new and improved materials powder X-ray diffraction (PXRD), Residual Gas Analyzer-Mass Spectroscopy (RGA-MS), Electron Microscopy (SEM/EDAX), temperature programmed desorption (TPD) and surface area techniques were utilized. In-situ carbonization of MFI zeolite membranes allowed for the maximum separation of isoprene from n-pentane, with a 4.1% enrichment of the binary stream with n-pentane. In four component streams, a modified MFI membrane had high selectivities for n-pentane and 1-3-pentadiene over isoprene but virtually no separation for the 2-methyl-2-butene/isoprene pair.

  14. Effects of TS1 zeolite structures on physical properties and enzymatic degradation of Poly (butylene succinate) (PBS)\\/TS1 zeolite hybrid composites

    Microsoft Academic Search

    Sung Yeon Hwang; Eui Sang Yoo; Seung Soon Im

    2011-01-01

    The objective of this study was to investigate how the water uptake features and carrier characteristics of the TS-1 zeolite affected the physical and rheological properties, morphological parameters, and enzymatic hydrolysis of Poly (butylene succinate) (PBS). The introduction of TS-1 zeolite as catalyst was developed for the preparation of PBS\\/TS-1 zeolite hybrid composites (PTHC) without heavy metal toxic substance in

  15. Systems including catalysts in porous zeolite materials within a reactor for use in synthesizing hydrocarbons

    DOEpatents

    Rolllins, Harry W. (Idaho Falls, ID); Petkovic, Lucia M. (Idaho Falls, ID); Ginosar, Daniel M. (Idaho Falls, ID)

    2012-07-24

    Catalytic structures include a catalytic material disposed within a zeolite material. The catalytic material may be capable of catalyzing a formation of methanol from carbon monoxide and/or carbon dioxide, and the zeolite material may be capable of catalyzing a formation of hydrocarbon molecules from methanol. The catalytic material may include copper and zinc oxide. The zeolite material may include a first plurality of pores substantially defined by a crystal structure of the zeolite material and a second plurality of pores dispersed throughout the zeolite material. Systems for synthesizing hydrocarbon molecules also include catalytic structures. Methods for synthesizing hydrocarbon molecules include contacting hydrogen and at least one of carbon monoxide and carbon dioxide with such catalytic structures. Catalytic structures are fabricated by forming a zeolite material at least partially around a template structure, removing the template structure, and introducing a catalytic material into the zeolite material.

  16. Methods of using structures including catalytic materials disposed within porous zeolite materials to synthesize hydrocarbons

    DOEpatents

    Rollins, Harry W. (Idaho Falls, ID); Petkovic, Lucia M. (Idaho Falls, ID); Ginosar, Daniel M. (Idaho Falls, ID)

    2011-02-01

    Catalytic structures include a catalytic material disposed within a zeolite material. The catalytic material may be capable of catalyzing a formation of methanol from carbon monoxide and/or carbon dioxide, and the zeolite material may be capable of catalyzing a formation of hydrocarbon molecules from methanol. The catalytic material may include copper and zinc oxide. The zeolite material may include a first plurality of pores substantially defined by a crystal structure of the zeolite material and a second plurality of pores dispersed throughout the zeolite material. Systems for synthesizing hydrocarbon molecules also include catalytic structures. Methods for synthesizing hydrocarbon molecules include contacting hydrogen and at least one of carbon monoxide and carbon dioxide with such catalytic structures. Catalytic structures are fabricated by forming a zeolite material at least partially around a template structure, removing the template structure, and introducing a catalytic material into the zeolite material.

  17. Motion of organic species occluded or sorbed within zeolites

    SciTech Connect

    Newsam, J.M.; Silbernagel, B.G.; Melchior, M.T.; Brun, T.O.; Trouw, F.

    1988-01-01

    Containment of organic species within microporous materials such as zeolites influences their modes of molecular motion. This manifests itself in a range of ways, including a reduction in the volume that is readily accessible to the molecules by translation, constraints upon the molecular conformational space, restricted modes of molecular reorientation, or altered vibrational frequencies. The perspectives on certain of the motional properties of sorbates and of tetramethylammonium cations within zeolites provided by simple molecular modeling, neutron powder diffraction, /sup 13/C and /sup 2/H(D), and inelastic and quasielastic neutron scattering are outlined and illustrated by selected recent results. 56 refs., 5 figs.

  18. Single and Multiple Heteroatom Incorporation in MFI Zeolites

    E-print Network

    Garcia Vargas, Nataly

    2012-11-05

    International Zeolite Association MAS Magic Angle Spinning ix MFI Code for the structure of Zeolite Socony Mobil - Five (ZSM-5) MPV, MPVO Meerwein-Ponndorf-Verley, Meerwein-Ponndorf-Verley- Oppenauer NMR Nuclear Magnetic Resonance ONIOM Our Own N.................................................................................................91 3.9 27Al MAS NMR (left) and 29Si MAS NMR (right) of Ge-Al-MFI with a target composition of Si/Ge = 10 and Si/Al = 50 .........................................92 3.10 X-ray absorption near edge spectra of reference GeO2, Ge-Silicalite-1 and Ge...

  19. CO2 adsorption on LTA zeolites: Effect of mesoporosity

    NASA Astrophysics Data System (ADS)

    Chen, Chao; Ahn, Wha-Seung

    2014-08-01

    Highly mesoporous LTA zeolite (Meso-LTA) was prepared using an organosilane surfactant, dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, as a mesopore-generating agent. Meso-LTA was characterized by X-ray powder diffraction, N2 adsorption-desorption isotherm at 77 K, scanning electron microscopy equipped with an energy dispersive X-ray spectroscopy, and then investigated for CO2 adsorption at 298 K. Compared to a solely microporous LTA zeolite (Micro-LTA), Meso-LTA showed faster CO2 adsorption kinetics at 1 bar and higher CO2 adsorption capacities under high pressure conditions (>10 bar).

  20. Progress in crystalline silicon research

    SciTech Connect

    Arvizu, D.E.; King, D.L.

    1989-01-01

    This paper discusses progress in US sponsored crystalline silicon photovoltaic cell technology for one-sun and concentrating applications, from the research laboratory to the production line. A summary of field experience, present economics, projected utility requirements, cell efficiency status, and the US DOE research direction will be presented. 26 refs., 4 figs., 2 tabs.

  1. Ductile crystalline–amorphous nanolaminates

    PubMed Central

    Wang, Yinmin; Li, Ju; Hamza, Alex V.; Barbee, Troy W.

    2007-01-01

    It is known that the room-temperature plastic deformation of bulk metallic glasses is compromised by strain softening and shear localization, resulting in near-zero tensile ductility. The incorporation of metallic glasses into engineering materials, therefore, is often accompanied by complete brittleness or an apparent loss of useful tensile ductility. Here we report the observation of an exceptional tensile ductility in crystalline copper/copper–zirconium glass nanolaminates. These nanocrystalline–amorphous nanolaminates exhibit a high flow stress of 1.09 ± 0.02 GPa, a nearly elastic-perfectly plastic behavior without necking, and a tensile elongation to failure of 13.8 ± 1.7%, which is six to eight times higher than that typically observed in conventional crystalline–crystalline nanolaminates (<2%) and most other nanocrystalline materials. Transmission electron microscopy and atomistic simulations demonstrate that shear banding instability no longer afflicts the 5- to 10-nm-thick nanolaminate glassy layers during tensile deformation, which also act as high-capacity sinks for dislocations, enabling absorption of free volume and free energy transported by the dislocations; the amorphous–crystal interfaces exhibit unique inelastic shear (slip) transfer characteristics, fundamentally different from those of grain boundaries. Nanoscale metallic glass layers therefore may offer great benefits in engineering the plasticity of crystalline materials and opening new avenues for improving their strength and ductility. PMID:17592136

  2. Effects of the zeolite framework on the adsorption of ethylene and benzene on alkali-exchanged zeolites: an ONIOM study

    Microsoft Academic Search

    Karan Bobuatong; Jumras Limtrakul

    2003-01-01

    The density functional theory (B3LYP\\/6-31G(d,p)) and our-own-N-layered integrated molecular orbital + molecular mechanics (ONIOM) approach utilizing two-layer ONIOM schemes (B3LYP\\/6-31G(d,p): UFF) have been employed to investigate the structures of alkali-exchanged faujasite (FAU) and ZSM-5 zeolites, and their interactions with ethylene and benzene. Inclusion of the extended zeolite framework has an effect on the structure and energetics of the adsorption complexes

  3. Chemical interactions in multimetal/zeolite catalysts

    SciTech Connect

    Sachtler, W.M.H.

    1992-02-07

    For Pt/NaY catalysts our analysis of the mechanism of metal particle formation has enabled us to produce at will samples which contain either the majority of the Pt particles in supercages, without filling these cages completely, or the Pt particles bulge into neighboring cages. The catalytic selectivity is distinctly different for these preparations, in the former case molecules can enter a supercage which is partially filled by the Pt cluster, in the second case adsorption takes place through the cage window. Applying the same principles of catalyst preparation of bimetallic catalysts enables us to produce PtCu particles in supercages of NaY, which contain, initially a Pt core, surrounded by a Cu mantle. Earlier we have found that Ni ions migrate into hexagonal prisms during calcination of Ni/NaY; this process can be partially suppressed by first filling these prisms with Mn or Cr ions. In more recent work we found that addition of Pt strongly lowers the temperature of Ni reduction. Part of the Ni ions is reduced by hydrogen while still inside the smaller cages. This reduction process is, however, reversible; at elevated temperature and in an inert atmosphere protons re-oxidize the Ni atoms and dihydrogen gas is developed. In this way it seems possible to count the Ni atoms in small cages. The calcination stage in the preparation of zeolite supported metals has been studied in considerable detail for Pd/NaY. The Pd is introduced as a tetrammin complex; during calcination the ammine ligands are successively oxidized. Once three ammine ligands are destroyed, the Pd ions which carry only one ligand, surprisingly jump from the supercages to the sodalite cage.

  4. Computational studies of polyelectrolytes containing zeolite fragments.

    SciTech Connect

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

    1999-08-05

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

  5. Computational studies of polyelectrolytes containing zeolitic fragments

    SciTech Connect

    Lee, Y.C.; Ratner, M.A.; Shriver, D.F. [Northwestern Univ., Evanston, IL (United States)] [Northwestern Univ., Evanston, IL (United States); Curtiss, L.A. [Argonne National Lab., IL (United States). Materials Science Div.] [Argonne National Lab., IL (United States). Materials Science Div.

    1999-08-05

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

  6. Dietary Hydrated Sodium Calcium Aluminosilicate Reduction of Aflatoxin M, Residue in Dairy Goat Milk and Effects on Milk Production and Components'r2

    Microsoft Academic Search

    Ernest E. Smith; Timothy D. Phillips; Jeffery A. Ellis; Roger B. Harvey; Leon F. Kubena; Jennifer Thompson; Gary Newton

    2009-01-01

    Lactating dairy goats were exposed to aflatoxin (100 and 200 ppb) and hydrated sodium calcium aluminosilicate at 1, 2, and 4% in two separate experiments. Naturally occurring low levels of aflatoxin M1 (.009 ppb) were found in the milk of the control diet, whereas there were no detectable levels of aflatoxin M1 in the milk of diets containing hydrated sodium

  7. 2D Zeolite Coatings: Langmuir-Schaefer Deposition of 3?nm Thick MFI Zeolite Nanosheets.

    PubMed

    Rangnekar, Neel; Shete, Meera; Agrawal, Kumar Varoon; Topuz, Berna; Kumar, Prashant; Guo, Qiang; Ismail, Issam; Alyoubi, Abdulrahman; Basahel, Sulaiman; Narasimharao, Katabathini; Macosko, Christopher W; Mkhoyan, K Andre; Al-Thabaiti, Shaeel; Stottrup, Benjamin; Tsapatsis, Michael

    2015-05-26

    Stable suspensions of zeolite nanosheets (3?nm thick MFI layers) were prepared in ethanol following acid treatment, which partially removed the associated organic structure-directing agent. Nanosheets from these suspensions could then be dispersed at the air-water interface and transferred to silicon wafers using Langmuir-Schaefer deposition. Using layer-by-layer deposition, control on coating thickness was demonstrated. In-plane X-ray diffraction (XRD) revealed that the deposited nanosheets contract upon calcination similar to bulk MFI crystals. Different methods for secondary growth resulted in preferentially oriented thin films of MFI, which had sub-12-nm thickness in certain cases. Upon calcination, there was no contraction detectable by in-plane XRD, indicating well-intergrown MFI films that are strongly attached to the substrate. PMID:25864539

  8. Characterization of natural zeolite clinoptilolite for sorption of contaminants

    NASA Astrophysics Data System (ADS)

    Xingu-Contreras, E.; García-Rosales, G.; García-Sosa, I.; Cabral-Prieto, A.; Solache-Ríos, M.

    2015-05-01

    The nanoparticles technology has received considerable attention for its potential applications in groundwater treatment for the removal of various pollutants as Cadmium. In this work, iron boride nanoparticles were synthesized in pure form and in presence of homo-ionized zeolite clinoptilolite, as support material. These materials were used for removing Cd (II) from aqueous solutions containing 10, 50, 100, 150, 200, 250, 300 and 400 mg/L. The characterization of these materials was made by using X-ray Diffraction, Scanning Electron Microscopy and Mössbauer Spectroscopy. Pure iron boride particles show a broad X-ray diffraction peak centered at 45? (2𝜃), inferring the presence of nanocrystals of Fe2B as identified from Mössbauer Spectroscopy. The size of these Fe2B particles was within the range of 50 and 120 nm. The maximum sorption capacities for Cd (II) of iron boride particles and supported iron boride particles in homo-ionized zeolitic material were nearly 100 %. For homo-ionized zeolite and homo-ionized zeolite plus sodium borohydride was ? 95 %.

  9. DIFFUSION MEASUREMENTS DURING PERVAPORATION THROUGH A ZEOLITE MEMBRANE

    EPA Science Inventory

    An isotopic-transient technique was used to directly measure diffusion times of H2O, methanol, ethanol, 2-propanol, and acetone in pure and binary mixture feeds transporting through a zeolite membrane under steady-state pervaporation conditions. Diffusivities can be determ...

  10. Synthesis and Properties of Nano Zeolitic Imidazolate Frameworks

    Microsoft Academic Search

    Satish K. Nune; Praveen K. Thallapally; Alice Dohnalkova; Chongmin Wang; Jun Liu; Gregory J. Exarhos

    2010-01-01

    Nano sized zeolitic imidazolate frameworks [nZIF-8] with excellent chemical and thermal stability has been synthesized at room temperature by simple mixing of 2-methylimidazole and zinc nitrate hexahydrate in methanol\\/ 1% high molecular weight poly(diallyldimethylammonium chloride) solution for 24 hrs

  11. Synthesis and Properties of Nano Zeolitic Imidazolate Frameworks

    SciTech Connect

    Nune, Satish K.; Thallapally, Praveen K.; Dohnalkova, Alice; Wang, Chong M.; Liu, Jun; Exarhos, Gregory J.

    2010-07-21

    Nano sized zeolitic imidazolate frameworks [nZIF-8] with excellent chemical and thermal stability has been synthesized at room temperature by simple mixing of 2-methylimidazole and zinc nitrate hexahydrate in methanol/ 1% high molecular weight poly(diallyldimethylammonium chloride) solution for 24 hrs

  12. USE OF SYNTHETIC ZEOLITES FOR ARSENATE REMOVAL FROM POLLUTANT WATER

    EPA Science Inventory

    Arsenic is known to be a hazardous contaminant in drinking water that causes arsenical dermatitis and skin cancer. In the present work, the potential use of a variety of synthetic zeolites for removal of arsenic from water below the current and proposed EPA MCL has been examined...

  13. ADSORPTION AND CATALYTIC DESTRUCTION OF TRICHLOROETHYLENE IN HYDROPHOBIC ZEOLITES

    EPA Science Inventory

    Several chromium exchanged ZSM-5 zeolites of varying SiO2/Al2O3 ratio were prepared and investigated for ambient (23 ?C) adsorption and subsequent oxidative destruction (250-400 ?C) of gaseous trichloroethylene (TCE, Cl2C=CHCl) in a humid air stream. With an increase in the SiO2...

  14. Use of synthetic zeolites for arsenate removal from pollutant water

    Microsoft Academic Search

    Siddhesh Shevade; Robert G. Ford

    2004-01-01

    Arsenic is known to be a hazardous contaminant in drinking water that causes arsenical dermatitis and skin cancer. In the present work, the potential use of a variety of synthetic zeolites for removal of arsenic from water below the current and proposed EPA MCL has been examined at room temperature. Experiments have been conducted to examine the extent of arsenic

  15. Chemisorption of alkenes on copper-exchanged ZSM-5 zeolite

    Microsoft Academic Search

    H. W. Jen; K. Otto

    1994-01-01

    On Cu-ZSM-5 zeolite at room temperature, propane is physisorbed, while propene shows characteristics of chemisorption. The chemisorption mode has certain advantages for the catalytic control of automotive emissions. Alkane and alkene adsorption equilibria and kinetics are compared on Cu-ZSM-5 and on ZSM-5 free of alumina. The results are discussed in terms of the Langmuir adsorption isotherm.

  16. Fenton Chemistry of FeIII Zeolitic Minerals Treated with

    E-print Network

    Dutta, Prabir K.

    Fenton Chemistry of FeIII -Exchanged Zeolitic Minerals Treated with Antioxidants T O N I A . R U D Fenton activity. Lung lining fluid contains antioxidants, such as glutathione (GSH) and ascorbic acid (AAIII- exchanged erionite and mordenite after treatment with antioxidants. The Fenton assay involved the reaction

  17. [Denitrification water treatment with zeolite composite filter by intermittent operation].

    PubMed

    Qing, Cheng-Song; Bao, Tao; Chen, Tian-Hu; Chen, Dong; Xie, Jing-Jing

    2012-12-01

    The zeolite composite filters (ZCF) with the size of4-8 mm were prepared using raw zeolite (0.15-0.18 mm) as the main material and the cement as binder. After a combination of material characterizations, such as the void fraction, apparent density, compression strength and surface area, the optimal prepared conditions of composite filters were obtained as follow: weight ratio of m (zeolite): m (cement) = 7 : 3, curing for 15 d under the moisture condition and ambient temperature. Through upflow low-concentration ammonia nitrogen wastewater, ZCF filled in the experimental column was hung with the biological membrane. Thus, intermittent dynamic experiments were conducted, the intermittent operation cycle included adsorption, biological regeneration and drip washing. Until concentration of ammonia nitrogen was more than 2 mg x L(-1) of effluent standards, water in experiment column was firstly emptied, and then blast biological regeneration was conducted. After the filters were bathed with water, the zeolite adsorption-biological regeneration cycle was performed repeatedly. The experimental results show that under conditions of 24 h blast and 5 d of continuous operation period, ammonia nitrogen removal rate is up to 87.6% on average, total nitrogen removal rate reaches 51.2% on average. PMID:23379168

  18. Binary diffusion of unequal sized molecules in zeolites

    Microsoft Academic Search

    Narasimhan Sundaram; Ralph T Yang

    2000-01-01

    Multicomponent diffusivities in zeolites are predicted using the framework of the theory of irreversible thermodynamics, for which the information on equilibrium mixture adsorption isotherms is a critical requirement. Two thermodynamically consistent mixture isotherms, a multi-site Langmuir model and a modified Dubinin-type expansion facilitate quantification of the thermodynamic effect. In both these isotherms, saturation capacities of the species are allowed to

  19. Smart zeolites: New forms of tungsten and molybdenum oxides

    Microsoft Academic Search

    Geoffrey A. Ozin; R. A. Prokopowicz; S. Oezkar

    1992-01-01

    In this Account, the authors describe their recent research efforts involving the use of volatile hexacarbonylmolybdenum and -tungstem compounds, as precursors in the synthesis of highly organized assemblies of molecular dimension molybdenum and tungsten oxides, encapsulated within the diamond network of 13-[Angstrom] supercages found in zeolite Y. These assemblies are extremely uniform in terms of their nuclearity and structure, and

  20. Studies of photochemically and electrochemically driven electron transport in zeolites

    NASA Astrophysics Data System (ADS)

    Mallouk, T. E.

    1988-04-01

    Electron transfer reactions in zeolites and related solid-state materials are being studied. Some particular areas of study are: Electron transfer reactions of linked sensitizer-acceptor molecules. We have studied via laser flash photolysis transient absorbance the photochemistry of linked Ru(bpy)3--diquat molecules exchanged onto the outer surface of zeolite L powder. Electron-donor quenching of excited-state RuL3 complexes was also examined. We have studied electron transfer reactions between cyanometallate anions M(CN)8(sup 4 minus)(M = Mo,W), M(CN)6(sup 4 minus)(M = Fe,Os) and excited state ruthenium complexes. Quantum-size TiO2 in zeolite L was next examined. We are attempting to prepare systems in which the conduction band of an oxide semiconductor is used to convey electrons from a sensitizer to a catalyst within a zeolite L particle. Internal platinization of pillared clays. We have photoplatinized dispersed Na(+) montmorillonite, using PtCl6(sup 2 minus) as the platinum source, and then pillared the clay with Al(OH)2C1 solutions. We are currently investigating the size and charge selectivity of these catalytic materials.

  1. Desulfurization of Transportation Fuels with Zeolites Under Ambient Conditions

    Microsoft Academic Search

    Ralph T. Yang; Arturo J. Hernández-Maldonado; Frances H. Yang

    2003-01-01

    Deep desulfurization of transportation fuels (gasoline, diesel, and jet fuels) is being mandated by U.S. and foreign governments and is also needed for future fuel cell applications. However, it is extremely difficult and costly to achieve with current technology, which requires catalytic reactors operated at high pressure and temperature. We show that Cu+ and Ag+ zeolite Y can adsorb sulfur

  2. Catalase-like activity studies of the manganese(II) adsorbed zeolites

    NASA Astrophysics Data System (ADS)

    ?içek, Ekrem; Dede, Bülent

    2013-12-01

    Preparation of manganese(II) adsorbed on zeolite 3A, 4A, 5A. AW-300, ammonium Y zeolite, organophilic, molecular sieve and catalase-like enzyme activity of manganese(II) adsorbed zeolites are reported herein. Firstly zeolites are activated at 873 K for two hours before contact manganese(II) ions. In order to observe amount of adsorption, filtration process applied for the solution. The pure zeolites and manganese(II) adsorbed zeolites were analysed by FT-IR. As a result according to the FT-IR spectra, the incorporation of manganese(II) cation into the zeolite structure causes changes in the spectra. These changes are expected particularly in the pseudolattice bands connected with the presence of alumino and silicooxygen tetrahedral rings in the zeolite structure. Furthermore, the catalytic activities of the Mn(II) adsorbed zeolites for the disproportionation of hydrogen peroxide were investigated in the presence of imidazole. The Mn(II) adsorbed zeolites display efficiency in the disproportion reactions of hydrogen peroxide, producing water and dioxygen in catalase-like activity.

  3. Zeolite in horizontal permeable reactive barriers for artificial groundwater recharge

    NASA Astrophysics Data System (ADS)

    Leal, María; Martínez-Hernández, Virtudes; Lillo, Javier; Meffe, Raffaella; de Bustamante, Irene

    2013-04-01

    The Spanish Water Reuse Royal Decree 1620/2007 considers groundwater recharge as a feasible use of reclaimed water. To achieve the water quality established in the above-mentioned legislation, a tertiary wastewater treatment is required. In this context, the infiltration of effluents generated by secondary wastewater treatments through a Horizontal Permeable Reactive Barrier (HPRB) may represent a suitable regeneration technology. Some nutrients (phosphate and ammonium) and some Pharmaceutical and Personal Care Products (PPCPs) are not fully removed in conventional wastewater treatment plants. To avoid groundwater contamination when effluents of wastewater treatments plants are used in artificial recharge activities, these contaminants have to be removed. Due to its sorption capacities, zeolite is among the most used reactive materials in Permeable Reactive Barrier (PRB). Therefore, the main goal of this study is to evaluate the zeolite retention effectiveness of nutrients and PPCPs occurring in treated wastewater. Batch sorption experiments using synthetic wastewater (SWW) and zeolite were performed. A 1:4 zeolite/SWW ratio was selected due to the high sorption capacity of the reactive material.The assays were carried out by triplicate. All the bottles containing the SWW-zeolite mixture were placed on a mechanical shaker during 24 hours at 140 rpm and 25 °C. Ammonium and phosphate, as main nutrients, and a group of PPCPs were selected as compounds to be tested during the experiments. Nutrients were analyzed by ion chromatography. For PPCPs determination, Solid Phase Extraction (SPE) was applied before their analysis by liquid chromatography-mass spectrometry time of flight (LC-MS/ TOF). The experimental data were fitted to linearized Langmuir and Freundlich isotherm equations to obtain sorption parameters. In general, Freundlich model shows a greater capability of reproducing experimental data. To our knowledge, sorption of the investigated compounds on zeolite has rarely been addressed and this holds true especially for PPCPs. Therefore, the obtained results will be useful for the design and characterization of those HPRBs in which zeolite will be employed to regenerate treated wastewater for artificial recharge activities.

  4. Multi-component lanthanide hybrids based on zeolite A/L and zeolite A/L-polymers for tunable luminescence.

    PubMed

    Chen, Lei; Yan, Bing

    2015-02-01

    Some multi-component hybrids based on zeolite L/A are prepared. Firstly, zeolite A/L is loaded with lanthanide complexes (Eu-DBM or Tb-AA (acetylacetone = AA, dibenzoylmethane = DBM)) into its channels. Secondly, 3-methacryloyloxypropyltrimethoxysilane (?-MPS) is used to covalently graft onto the surface of functionalized zeolite A/L (Si-[ZA/L?Eu-DBM(Tb-AA)]). Thirdly, lanthanide ions (Eu(3+)/Tb(3+)) are coordinated to the functionalized zeolite A/L and ligands (phen(1,10-phenanthroline) or bipy (2,2'-bipyridyl)) are introduced by a ship-in-bottle method. The inside-outside double modifications of ZA/L with lanthanide complexes afford the final hybrids and these are characterized by means of XRD, FT-IR, UV-vis DRS, SEM and luminescence spectroscopy, some of which display white or near-white light emission. Furthermore, selected above-mentioned hybrids are incorporated into PEMA/PMMA (poly ethyl methylacryate/poly methyl methacrylate) hosts to prepare luminescent polymer films. These results provide abundant data that these hybrid materials can be expected to have potential application in various practical fields. PMID:25411917

  5. Catalytic dehydrocondensation of methane towards benzene and naphthalene on transition metal supported zeolite catalysts: templating role of zeolite micropores and characterization of active metallic sites

    Microsoft Academic Search

    Yuying Shu; Masaru Ichikawa

    2001-01-01

    The catalytic dehydrocondensation of methane to benzene and naphthalene with a bulky of hydrogen on transition metal supported zeolite catalysts is one of strategies for the catalytic conversion of methane and a challenging topic in heterogeneous catalysis. This paper is dealt with the current progress in catalytic dehydrocondensation of methane towards benzene and naphthalene on transition metal supported zeolite catalysts,

  6. Structural, vibrational, and elastic properties of a calcium aluminosilicate glass from molecular dynamics simulations: the role of the potential.

    PubMed

    Bauchy, M

    2014-07-14

    We study a calcium aluminosilicate glass of composition (SiO2)0.60(Al2O3)0.10(CaO)0.30 by means of molecular dynamics. To this end, we conduct parallel simulations, following a consistent methodology, but using three different potentials. Structural and elastic properties are analyzed and compared to available experimental data. This allows assessing the respective abilities of the potentials to produce a realistic glass. We report that, although all these potentials offer a reasonable glass structure, featuring tricluster oxygen atoms, their respective vibrational and elastic predictions differ. This allows us to draw some general conclusions about the crucial role, or otherwise, of the interaction potential in silicate systems. PMID:25028027

  7. The effects of hot corrosion on the microstructure of a silicon carbide fiber-reinforced calcium aluminosilicate

    SciTech Connect

    Kumar, A.; Oppici, M.A.; Fox, A.G. [Naval Postgraduate School, Monterey, CA (United States); Wang, S.W. [Naval Air Warfare Center, Warminster, PA (United States)

    1995-12-01

    This work, funded by the navy exploratory development program, aircraft materials section, studied the effects of sodium sulfate hot corrosion on the microstructure of a SiC fiber-reinforced calcium aluminosilicate by x-ray diffraction and scanning electron microscopy. The corrosion of the composite by liquid sodium sulfate at 900{degrees}C for 50 hours gave an approximately 50-75 {mu}m thick reaction zone. Several phases, including wollastonite, nepheline and albite were identified within this reaction zone. The mechanisms by which these phases are developed are explained in terms of the kinetics of the dissociation of the sodium sulfate and its reaction with both the oxidized silicon carbide fibers and the anorthite matrix.

  8. Structural, vibrational, and elastic properties of a calcium aluminosilicate glass from molecular dynamics simulations: The role of the potential

    SciTech Connect

    Bauchy, M., E-mail: bauchy@mit.edu [Concrete Sustainability Hub, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA and Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095 (United States)

    2014-07-14

    We study a calcium aluminosilicate glass of composition (SiO{sub 2}){sub 0.60}(Al{sub 2}O{sub 3}){sub 0.10}(CaO){sub 0.30} by means of molecular dynamics. To this end, we conduct parallel simulations, following a consistent methodology, but using three different potentials. Structural and elastic properties are analyzed and compared to available experimental data. This allows assessing the respective abilities of the potentials to produce a realistic glass. We report that, although all these potentials offer a reasonable glass structure, featuring tricluster oxygen atoms, their respective vibrational and elastic predictions differ. This allows us to draw some general conclusions about the crucial role, or otherwise, of the interaction potential in silicate systems.

  9. Synthesis, Processing, and Characterization of Inorganic-Organic Hybrid Cross-Linked Silica, Organic Polyimide, and Inorganic Aluminosilicate Aerogels

    NASA Technical Reports Server (NTRS)

    Nguyen, Baochau N.; Guo, Haiquan N.; McCorkle, Linda S.

    2014-01-01

    As aerospace applications become ever more demanding, novel insulation materials with lower thermal conductivity, lighter weight and higher use temperature are required to fit the aerospace application needs. Having nanopores and high porosity, aerogels are superior thermal insulators, among other things. The use of silica aerogels in general is quite restricted due to their inherent fragility, hygroscopic nature, and poor mechanical properties, especially in extereme aerospace environments. Our research goal is to develop aerogels with better mechanical and environmental stability for a variety of aeronautic and space applications including space suit insulation for planetary surface missions, insulation for inflatable structures for habitats, inflatable aerodynamic decelerators for entry, descent and landing (EDL) operations, and cryotank insulation for advance space propulsion systems. Different type of aerogels including organic-inorganic polymer reinforced (hybrid) silica-based aerogels, polyimide aerogels and inorganic aluminosilicate aerogels have been developed and examined.

  10. Synthesis and characterization of new crystalline titanates

    E-print Network

    Gonzalez, Edwin Sabath

    1991-01-01

    of the Type 2 crystalline titanate 12. Comparison between the X-Ray diffraction patterns of a sample calcined in nitrogen and a sample as prepared of the Type 2 crystalline titanate. 13. Comparison between the X-Ray diffraction patterns of a sample... calcined in air and a sample as prepared of the Type 2 crystalline titanate Figure Page 14. Electron micrographs of Type 2 crystalline titanate, batch ? 35 70 15. Electron micrographs of Type 2 crystalline titanate, batch ? 47 71 16. Electron...

  11. Supercritical fluid removal of hydrocarbons adsorbed on wide pore zeolite catalysts

    SciTech Connect

    Lucia M. Petkovic; Daniel M. Ginosar; Kyle C. Burch

    2005-06-01

    The effect of zeolite pore structure on coke removal by supercritical fluid regeneration (SFR) was studied on a series of wide pore zeolite catalysts, which included acidic Y, beta, L, and mordenite zeolites. Catalyst samples were deactivated under liquid phase isobutane/butene alkylation reaction conditions and treated under flowing supercritical isobutane for 60 min. The chemical nature of the species remaining on the catalyst surface before and after SFR was analyzed by temperature-programmed oxidation (TPO), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and ultraviolet-visible (UV-Vis) spectroscopy. Zeolite pore structure played an important role not only in hydrocarbon deposition during alkylation but also in hydrocarbon transformation and removal during SFR. During SFR, the formation of unsaturated cyclic or polycyclic compounds, which likely affects catalyst long-term activity after cyclic alkylation/SFR treatments, was hindered on beta zeolites and favored on catalysts containing periodic expansions or cages, such as Y and L zeolites.

  12. The Ameliorative Effect of Artificial Zeolite on Barley under Saline Conditions

    NASA Astrophysics Data System (ADS)

    Al-Busaidi, A.; Yamamoto, T.; Irshad, M.

    This investigation was aimed to evaluate the effects of zeolite in conjunction with seawater irrigation on barley (Hordeum vulgare L.) growth and salt composition of soil. A sand dune soil was amended with Ca-type zeolite at the rate of 1 and 5% and the seawater was diluted up to the electrical conductivity of 3 and 16 dS mG1. Present results showed that zeolite application significantly increased water holding capacity of the soil and accumulated more salts. The zeolite mixed soils improved plant growth compared to the un-amended control. Higher saline water significantly suppressed the growth of barley than the water with low salinity. The restricted plant growth due to the effects of specific ion or Na+/Ca2+ imbalance may be ameliorated using Ca-type zeolite. We may conclude that soil amendment with zeolite could alleviate the adverse effects of salts on plants following irrigation with higher saline water.

  13. XAFS Study on TiO2 Photocatalyst Loaded on Zeolite Synthesized from Steel Slag

    NASA Astrophysics Data System (ADS)

    Kuwahara, Yasutaka; Ohmichi, Tetsutaro; Mori, Kosuke; Katayama, Iwao; Yamashita, Hiromi

    2007-02-01

    The convenient route for the synthesis of Y-zeolites by utilizing steel slag as a material source was developed. Through hydrothermal treatment, well-crystallized Y-zeolite was obtained. We also synthesized TiO2-loaded Y-zeolites by an impregnation method. The structure of titanium oxide species highly dispersed on the zeolite, which couldn't be detected by XRD patterns, was investigated by XAFS analysis. Photocatalytic activity for decomposition of 2-propanol in liquid phase was found to be enhanced by the hydrophobic surface property of zeolite. It has been demonstrated that the zeolite synthesized from steel slag would be applicable as a promising support of TiO2 photocatalyst.

  14. Factors influencing ?-crystallin association with phospholipid vesicles

    PubMed Central

    Cobb, Brian A.; Petrash, J. Mark

    2010-01-01

    Purpose Lens lipids undergo a number of changes with age, including an overall increase in phospholipid acyl chain saturation and a decrease in length. In addition, the amount of membrane bound ?-crystallin increases dramatically with age and with the onset of cataract. The aim of this study was to determine if a link exists between age and cataract associated changes in lens lipids and the changes in ?-crystallin membrane association. Methods Protein-free lipid vesicles composed of a wide variety of synthetic and lens-derived lipid vesicles were formed by sonication. These vesicles were used with fluorescent native and recombinant ?-crystallin conjugates in vesicle binding assays. Vesicles were collected by centrifugation and bound ?-crystallin was quantified with fluorescence intensity measurements. Results ?-Crystallin complexes showed remarkably similar binding profiles for all lipid vesicles tested, regardless of lipid origin, phospholipid head group, acyl chain length or saturation, and inclusion of cholesterol. In addition, recombinant ?-crystallin complexes bind to these vesicles in a manner that is essentially indistinguishable from that of native human and bovine ?-crystallins. Unlike ?-crystallin binding to lens membranes containing intrinsic proteins, binding of ?-crystallin to protein-free vesicles was very high capacity and unsaturable. Conclusions We conclude from these data that the binding of ?-crystallin to lens membranes is not lipid-specific. Furthermore, protein post-translational changes, such as phosphorylation, do not appear to alter ?-crystallin binding to these vesicles. Given the linearity of the binding curves, we propose that the only limiting factor for normal ?-crystallin membrane binding is available surface area on the bilayer. Finally, the present data suggests that increased in vivo membrane association of ?-crystallin is not a result of lipid changes, but more likely a result of non-lipid factors such as the accumulation of high molecular weight forms of ?-crystallin. PMID:11951084

  15. Hydrothermal synthesis of NaA zeolite membrane together with microwave heating and conventional heating

    Microsoft Academic Search

    Aisheng Huang; Weishen Yang

    2007-01-01

    Uniform and dense NaA zeolite membrane was prepared by hydrothermal synthesis method together with microwave heating and conventional heating. The properties of the as-synthesized zeolite membrane were investigated by XRD, SEM and pervaporation evaluation for dehydration of 95 wt.% isopropanol\\/water mixture at 343 K, respectively. After microwave heating, the ?-Al2O3 support surface was covered with homogeneous zeolite nuclei, which facilitated to form

  16. Effect of some additives on synthesis of zeolite from coal fly ash

    Microsoft Academic Search

    Deyi Wu; Bohua Zhang; Li Yan; Hainan Kong; Xinze Wang

    2006-01-01

    Hydrothermal conversion of fly ash into zeolites was conducted and the effects of the addition of sodium halide and waste solutions produced after zeolitization of fly ash, as well as the adjustment of the Si\\/Al ratio prior to synthesis process on the formation and cation exchange capacity (CEC) of zeolite product were evaluated. Both the addition of NaCl and NaF

  17. Microwave Versus Conventional-Hydrothermal Synthesis of NaY Zeolite

    Microsoft Academic Search

    Hiroaki Katsuki; Sachiko Furuta; Sridhar Komarneni

    2001-01-01

    This paper focuses on the synthesis of NaY zeolite crystals by using microwave-hydrothermal (M-H) processing. NaY zeolites were synthesized from colloidal silica, sodium aluminate, sodium hydroxide and deionized water at 100°C, and some properties were studied. NaY zeolite crystals with high surface area, in the range of 439 to 716 m2\\/g, have been prepared at 100°C for 1 to 3

  18. Microwave-Driven Zeolite?Guest Systems Show Athermal Effects from Nonequilibrium Molecular Dynamics

    Microsoft Academic Search

    Cristian Blanco; Scott M. Auerbach

    2002-01-01

    simulations. We studied industrially important zeolites that represent extremes of high charge (NaY) and low charge (de-aluminated Y (DAY) and silicalite) materials. We also studied guest molecules that represent extremes of polar (methanol) and nonpolar (benzene) species. We performed equilibrium molecular dynamics (MD) and nonequilibrium MD (NEMD) simulations on bare zeolites, and on zeolite-guest systems with single-component guest phases as

  19. Alkylation of benzene with ethylene over faujasite zeolite investigated by the ONIOM method

    Microsoft Academic Search

    Supawadee Namuangruk; Piboon Pantu; Jumras Limtrakul

    2004-01-01

    The alkylation of benzene with ethylene over faujasite zeolite has been investigated using an 84T cluster of faujasite zeolite serving as a nanometer-sized chemical reactor modeled by the ONIOM3 (MP2\\/6-311++G(d,p):HF\\/6-31G(d):UFF) method, which gives accurate adsorption energies for the reactants and the product, indicating the accuracy of the model in representing interactions between the adsorbates and the zeolite. The computed adsorption

  20. Preparation of highly selective zeolite ZSM-5 membranes by a post-synthetic coking treatment

    Microsoft Academic Search

    Yushan Yan; Mark E. Davis; George R. Gavalas

    1997-01-01

    Zeolite ZSM-5 membranes with high n-butane:isobutane selectivities, e.g., 322 at 185°C, are obtained by a selective deposition of coke into non-zeolitic pores. The zeolite membranes are prepared by in situ crystallization on either bare porous ?-Al2O3 support disks or disks that are pretreated to include a diffusion barrier. The post-synthetic coking treatment is accomplished by impregnating these membranes with liquid

  1. Synthesis of zeolite from coal fly ashes with different silica–alumina composition

    Microsoft Academic Search

    Miki Inada; Yukari Eguchi; Naoya Enomoto; Junichi Hojo

    2005-01-01

    Coal fly ashes can be converted into zeolites by hydrothermal alkaline treatment. This study focuses on the effect of Si\\/Al molar ratio of the fly ash source on the type of formed zeolite, which also is affected by the alkaline condition. The fly ashes were mixed with an aqueous NaOH solution and hydrothermally treated at about 100°C. Zeolite Na–P1 and\\/or

  2. A solid-state nuclear magnetic resonance study of the reactions of propene on HY zeolite

    E-print Network

    Oshiro, Irene Sueko

    1988-01-01

    , as denoted by arrows C CP/MAS spectrum of propene-2- C 13 adsorbed on HY zeolite at room temperature 10 The polymerization reaction proposed in reference 13 for the adsorption of propene on HY zeolite The Bloch decay pulse sequence in NMR experiments... 12 18 The cross polarization pulse sequence for dilute nuclei . . . . . . . . . . . . . . . . . . . . . 22 The CAVERN apparatus and rotor used in low temperature adsorptions 26 C spectra of propene adsorbed on HY zeolite . 31 C MAS NMR spectra...

  3. An investigation of Knoevenagel condensation reaction in microreactors using a new zeolite catalyst

    Microsoft Academic Search

    Xiongfu Zhang; Emily Sau Man Lai; Rosa Martin-Aranda; King Lun Yeung

    2004-01-01

    New basic zeolite catalysts obtained by grafting amino groups onto NaX and CsNaX zeolites exhibit excellent catalytic activities for Knoevenagel condensation reaction between benzaldehyde and ethyl cyanoacetate (ECA), ethyl acetoacetate (EAA) and diethyl malonate (DEM). The CsNaX-NH2 catalyst also displays higher conversion compared to aminopropylated MCM-41. Knoevenagel condensation reaction in a CsNaX zeolite microreactor performed better than the traditional packed

  4. Physicochemical properties and activity of Mo-containing zeolite catalysts of nonoxidative conversion of methane

    NASA Astrophysics Data System (ADS)

    Korobitsyna, L. L.; Arbuzova, N. V.; Vosmerikov, A. V.

    2013-06-01

    High-silica zeolites of ZSM-5 structural type were synthesized using various structure-forming additives and without them. Mo-containing catalytic systems were prepared on the basis of these zeolites. Their physicochemical properties and activity in the course of the nonoxidative conversion of methane were studied. The Mo/ZSM-5 catalyst obtained on the basis of zeolite synthesized with hexamethylenediamine showed high aromatizing activity and stability.

  5. Growth and bone development in weanling quarter horses fed diets supplemented with sodium zeolite-A 

    E-print Network

    Frey, Kimberly Suzanne

    1991-01-01

    - supplemented, for twelve days. After this time, the deficient group had no increase in dry weight and the supplemented group had an increase of 23%. At the end of eight days, the 16 supplemented bones had a 140% increase in collagen content over... of osteogenic cells, especially osteoblasts, and silicon mainly influences bone growth through collagen synthesis (1982). Sodium Zeolite-A Sodium zeolite-A (SZA) may prove to be a beneficial source of bioavailable silicon. Zeolites are a group of naturally...

  6. Environmental Applications of Natural Zeolitic Materials Based on Their Ion Exchange Properties

    Microsoft Academic Search

    C. Colella; Piazza Ie; V. Tecchio

    \\u000a Present and potential use of natural zeolites as cation exchangers in environmental protection is reviewed. Siliceous zeolites,\\u000a such as chabazite, clinoptilolite, mordenite and phillipsite, exhibit good selectivities for cations with low charge density,\\u000a e.g., Cs+ and NH4\\u000a +, and for cations with low hydration energy, such as Pb2+. Zeolitised tuffs, containing the mentioned zeolites, may therefore be utilised for removing

  7. Steam promoted mesoporosity in USY zeolites: structural properties and 1,2,4-TMB reactivity

    Microsoft Academic Search

    G Tonetto; M. L Ferreira; H de Lasa

    2004-01-01

    This work addresses the potential effects of steaming in the case of dealumination of Y zeolites. With this end, the interaction between 1,2,4-trimethylbenzene (1,2,4-TMB) and ultrastable Y zeolite (USY) is analyzed. The zeolite is modeled using the complete exposed USY structure of one unit cell constituted by eight sodalite cages, 16 hexagonal prisms bridging the sodalite cages and the formed

  8. Catalytic oxidation of volatile organic compounds (VOCs) mixture (isopropanol\\/ o-xylene) on zeolite catalysts

    Microsoft Academic Search

    R. Beauchet; P. Magnoux; J. Mijoin

    2007-01-01

    The catalytic oxidation of isopropanol and o-xylene alone and in mixture was investigated over basic zeolites (CsX and NaX) and an acidic zeolite (HY). For a given temperature, the conversion of VOCs mixture into CO2 increases with the basicity of the zeolite. Results show that VOCs are oxidized through a basic mechanism over NaX, and through an acidic mechanism over

  9. Equilibrium and kinetic modeling of adsorptive sulfur removal from gasoline by synthesized Ce–Y zeolite

    Microsoft Academic Search

    Maryam Montazerolghaem; Amir Rahimi; Fakhry Seyedeyn-Azad

    2010-01-01

    In this research, the adsorption of a model sulfur compound, thiophene, from a simulated gasoline onto Ce–Y zeolite in pellet and powder forms was investigated. For this purpose, zeolite Na–Y was synthesized, and Ce–Y zeolite was prepared via solid-state ion-exchanged (SSIE) method. Adsorptive desulfurization of model gasoline was conducted in a batch reactor at ambient conditions to evaluate the equilibrium

  10. Silver confined within zeolite EMT nanoparticles: preparation and antibacterial properties

    NASA Astrophysics Data System (ADS)

    Dong, B.; Belkhair, S.; Zaarour, M.; Fisher, L.; Verran, J.; Tosheva, L.; Retoux, R.; Gilson, J.-P.; Mintova, S.

    2014-08-01

    The preparation of pure zeolite nanocrystals (EMT-type framework) and their silver ion-exchanged (Ag+-EMT) and reduced silver (Ag0-EMT) forms is reported. The template-free zeolite nanocrystals are stabilized in water suspensions and used directly for silver ion-exchange and subsequent chemical reduction under microwave irradiation. The high porosity, low Si/Al ratio, high concentration of sodium and ultrasmall crystal size of the EMT-type zeolite permitted the introduction of a high amount of silver using short ion-exchange times in the range of 2-6 h. The killing efficacy of pure EMT, Ag+-EMT and Ag0-EMT against Escherichia coli was studied semi-quantitatively. The antibacterial activity increased with increasing Ag content for both types of samples (Ag+-EMT and Ag0-EMT). The Ag0-EMT samples show slightly enhanced antimicrobial efficacy compared to that of Ag+-EMT, however, the differences are not substantial and the preparation of Ag nanoparticles is not viable considering the complexity of preparation steps.The preparation of pure zeolite nanocrystals (EMT-type framework) and their silver ion-exchanged (Ag+-EMT) and reduced silver (Ag0-EMT) forms is reported. The template-free zeolite nanocrystals are stabilized in water suspensions and used directly for silver ion-exchange and subsequent chemical reduction under microwave irradiation. The high porosity, low Si/Al ratio, high concentration of sodium and ultrasmall crystal size of the EMT-type zeolite permitted the introduction of a high amount of silver using short ion-exchange times in the range of 2-6 h. The killing efficacy of pure EMT, Ag+-EMT and Ag0-EMT against Escherichia coli was studied semi-quantitatively. The antibacterial activity increased with increasing Ag content for both types of samples (Ag+-EMT and Ag0-EMT). The Ag0-EMT samples show slightly enhanced antimicrobial efficacy compared to that of Ag+-EMT, however, the differences are not substantial and the preparation of Ag nanoparticles is not viable considering the complexity of preparation steps. Electronic supplementary information (ESI) available: Zeta potential data of Ag-EMT suspensions, pore-size distributions and antibacterial data for Ag-EMT 2 h samples. See DOI: 10.1039/c4nr03169e

  11. Facile synthesis of hollow zeolite microspheres through dissolution-recrystallization procedure in the presence of organosilanes

    NASA Astrophysics Data System (ADS)

    Tao, Haixiang; Ren, Jiawen; Liu, Xiaohui; Wang, Yanqin; Lu, Guanzhong

    2013-04-01

    Hollow zeolite microspheres have been hydrothermally synthesized in the presence of organosilanes via a dissolution-recrystallization procedure. In the presence of organosilanes, zeolite particles with a core/shell structure formed at the first stage of hydrothermal treatment, then the core was consumed and recrystallized into zeolite framework to form the hollow structure during the second hydrothermal process. The influence of organosilanes was discussed, and a related dissolution-recrystallization mechanism was proposed. In addition, the hollow zeolite microspheres exhibited an obvious advantage in catalytic reactions compared to conventional ZSM-5 catalysts, such as in the alkylation of toluene with benzyl chloride.

  12. Lithium modified zeolite synthesis for conversion of biodiesel-derived glycerol to polyglycerol

    NASA Astrophysics Data System (ADS)

    Ayoub, Muhammad; Abdullah, Ahmad Zuhairi; Inayat, Abrar

    2014-10-01

    Basic zeolite has received significant attention in the catalysis community. These zeolites modified with alkaline are the potential replacement for existing zeolite catalysts due to its unique features with added advantages. The present paper covers the preparation of lithium modified zeolite Y (Li-ZeY) and its activity for solvent free conversion of biodiesel-derived glycerol to polyglycerol via etherification process. The modified zeolite was well characterized by X-ray diffraction (XRD), Scanning Electron Microscope (SEM) and Nitrogen Adsorption. The SEM images showed that there was no change in morphology of modified zeolite structure after lithium modification. XRD patterns showed that the structure of zeolite was sustained after lithium modification. The surface properties of parent and modified zeolite was also observed N2 adsortion-desorption technique and found some changes in surface area and pore size. In addition, the basic strength of prepared materials was measured by Hammet indicators and found that basic strength of Li-ZeY was highly improved. This modified zeolite was found highly thermal stable and active heterogamous basic catalyst for conversion of solvent free glycerol to polyglycerol. This reaction was conducted at different temperatures and 260 °C was found most active temperature for this process for reaction time from 6 to 12 h over this basic catalyst in the absence of solvent.

  13. Photocatalytic degradation of benzene on zeolite-incorporated TiO2 film.

    PubMed

    Hisanaga, Teruaki; Tanaka, Keiichi

    2002-08-01

    Zeolite powder was incorporated into the TiO2 film. Their photoactivities were evaluated for the gas phase degradation of benzene. Seven zeolite samples were used in this study and each enhanced the photocatalytic degradation. Humidity in the gas sample increased the degradation, but suppressed the adsorption of benzene to the TiO2 film. It was noted that the photoactivity was inversely proportional to the silica/alumina ratio of zeolite, whereas adsorption increased with this ratio. It was suggested that the adsorption of water onto zeolite contributes to the enhancement of benzene degradation. PMID:12137993

  14. Ligand exchange photochemistry of iodopentaamminerhodium (III) in a sodium/hydrogen Y type zeolite

    E-print Network

    Camara, Michael Joseph

    1981-01-01

    of the zeolite resulted in a lower value for the quantum yield of 0. 20+0. 07. The ammonia produced by this reaction was traoped within the zeolite as ammonium ious and semi-quantitatively analyzed by infrared spectroscopy. The rate was observed to fall off... for infrared study. Infrared spectrum of the ammonium ion band at -1 1450 cm and the zeolite background Calibration graph of ammonium ion concentration versus infrared absorption Correlation of the actual thickness of wafers of 33 38 41 43 zeolite...

  15. Mid-infrared spectroscopic studies of alkali-activated fly ash structure

    Microsoft Academic Search

    A. Fernández-Jiménez; A. Palomo

    2005-01-01

    Infrared spectroscopic techniques were used in the present study to acquire a deeper understanding of mid-range order in the alkaline aluminosilicate (zeolite precursor) formed in the alkali activation of fly ash. Experiments were conducted with three type F fly ashes containing different proportions of vitreous and crystalline (primarily mullite and quartz) phases, activated with an 8M solution of NaOH. All

  16. Dynamic Nuclear Polarization NMR Enables the Analysis of Sn-Beta Zeolite Prepared with Natural Abundance [superscript 119]Sn Precursors

    E-print Network

    Gunther, William R.

    The catalytic activity of tin-containing zeolites, such as Sn-Beta, is critically dependent on the successful incorporation of the tin metal center into the zeolite framework. However, synchrotron-based techniques or ...

  17. GREEN CHEMISTRY. Shape-selective zeolite catalysis for bioplastics production.

    PubMed

    Dusselier, Michiel; Van Wouwe, Pieter; Dewaele, Annelies; Jacobs, Pierre A; Sels, Bert F

    2015-07-01

    Biodegradable and renewable polymers, such as polylactic acid, are benign alternatives for petrochemical-based plastics. Current production of polylactic acid via its key building block lactide, the cyclic dimer of lactic acid, is inefficient in terms of energy, time, and feedstock use. We present a direct zeolite-based catalytic process, which converts lactic acid into lactide. The shape-selective properties of zeolites are essential to attain record lactide yields, outperforming those of the current multistep process by avoiding both racemization and side-product formation. The highly productive process is strengthened by facile recovery and practical reactivation of the catalyst, which remains structurally fit during at least six consecutive reactions, and by the ease of solvent and side-product recycling. PMID:26138977

  18. Mechanism of the thermal decomposition of tetraethylammonium in zeolite {beta}

    SciTech Connect

    Bourgeat-Lami, E.; Di Renzo, F.; Fajula, F. [CNRS, ENSCM, Montpellier (France)] [and others

    1992-04-30

    The mechanism of the thermal decomposition of tetraethylammonium (TEA) in zeolite {beta} has been investigated under air and argon atmosphere using a combined technique of thermogravimetric analysis and mass spectrometry. The nature of the volatile products and the characterization of the solid after each thermal phenomenon shows that all TEA species, occluded ion pairs and counteranions, decompose into triethylamine and ethylene in a single step, in the temperature range 200-350{degrees}C. The amine readsorbs on the acidic sites of the zeolite and, as the temperature is increased, decomposes into lighter amines by sequential Hofmann elimination reactions. Part of the ethylene also reacts with the acid sites yielding aliphatic and aromatic hyrocarbons. Complete desorption of the organic species form the structure requires a temperature higher than 500 {degrees}C. 14 refs., 5 figs., 8 tabs.

  19. Crystallization Kinetics of Barium and Strontium Aluminosilicate Glasses of Feldspar Composition

    NASA Technical Reports Server (NTRS)

    Hyatt, Mark J.; Bansal, Narottam P.

    1994-01-01

    Crystallization kinetics of BaO.Al2O3.2SiO2 (BAS) and SrO.Al2O3.2SiO2 (SAS) glasses in bulk and powder forms have been studied by non-isothermal differential scanning calorimetry (DSC). The crystal growth activation energies were evaluated to be 473 and 451 kJ/mol for bulk samples and 560 and 534 kJ/mol for powder specimens in BAS and SAS glasses, respectively. Development of crystalline phases on thermal treatments of glasses at various temperatures has been followed by powder x-ray diffraction. Powder samples crystallized at lower temperatures than the bulk and the crystallization temperature was lower for SAS glass than BAS. Crystallization in both glasses appeared to be surface nucleated. The high temperature phase hexacelsian, MAl2Si2O8 (M = Ba or Sr), crystallized first by nucleating preferentially on the glass surface. Also, monoclinic celsian does not nucleate directly in the glass, but is formed at higher temperatures from the transformation of the metastable hexagonal phase. In SAS the transformation to monoclinic celsian occurred rapidly after 1 h at 1100 C. In contrast, in BAS this transformation is sluggish and difficult and did not go to completion even after 10 h heat treatment at 1400 C. The crystal growth morphologies in the glasses have been observed by optical microscopy. Some of the physical properties of the two glasses are also reported.

  20. Crystallization and properties of Sr-Ba aluminosilicate glass-ceramic matrices

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Hyatt, Mark J.; Drummond, Charles H., III

    1991-01-01

    Powders of roller quenched (Sr,Ba)O-Al2O3-2SiO2 glasses of various compositions were uniaxially pressed into bars and hot isostatically pressed at 1350 C for 4 hours or cold isostatically pressed and sintered at different temperatures between 800 to 1500 C for 10 or 20 hours. Densities, flexural strengths, and linear thermal expansion were measured for three compositions. The glass transition and crystallization temperatures were determined by Differential Scanning Calorimetry (DSC). The liquidus and crystallization temperature from the melt were measured using high temperature Differential Thermal Analysis (DTA). Crystalline phases formed on heat treatment of the glasses were identified by powder X ray diffraction. In Sr containing glasses, the monoclinic celsian phase always crystallized at temperatures above 1000 C. At lower temperatures, the hexagonal analog formed. The temperature for orthorhombic to hexagonal structural transformation increased monotonically with SrO content, from 327 C for BaO-Al2O3-2SiO2 to 758 C for SrO-Al2O3-2SiO2. These glass powders can be sintered to almost full densities and monoclinic celsian phase at a relatively low temperature of 1100 C.

  1. Crystallization and properties of Sr-Ba aluminosilicate glass-ceramic matrices

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Hyatt, Mark J.; Drummond, Charles H., III

    1991-01-01

    Powders of roller quenched (Sr,Ba)O-Al2O3-2SiO2 glasses of various compositions were uniaxially pressed into bars and hot isostatically pressed at 1350 C for 4 hours or cold isostatically pressed and sintered at different temperatures between 800 to 1500 C for 10 or 20 hours. Densities, flexural strengths, and linear thermal expansion were measured for three compositions. The glasss transition and crystallization temperatures were determined by Differential Scanning Calorimetry (DSC). The liquidus and crystallization temperature from the melt were measured using high temperature Differential Thermal Analysis (DTA). Crystalline phases formed on heat treatment of the glasses were identified by powder x ray diffraction. In Sr containing glasses, the monoclinic celsian phase always crystallized at temperatures above 1000 C. At lower temperatures, the hexagonal analog formed. The temperature for orthorhombic to hexagonal structure transformation increased monotonically with SrO content, from 327 C for BaO-Al2O3-2SiO2 to 758 C for SrO-Al2O3-2SiO2. These glass powders can be sintered to almost full densities and monoclinic celsian phase at a relatively low temperature of 1100 C.

  2. Nonequilibrium Diffusion in Zeolites due to Deterministic Hamiltonian Chaos

    Microsoft Academic Search

    Dmitry I. Kopelevich; Hsueh-Chia Chang

    1999-01-01

    We show that diffusionlike transport of a spherical sorbate molecule through a zeolite crystal can be driven by deterministic chaos instead of thermal stochastic noise when the sorbate and crystal do not equilibrate. Using a random-phase approximation for the resulting Arnold diffusion and a boundary-layer analysis of the quasisteady Fokker-Planck equation, we estimate the effective diffusivity to scale as T

  3. Synthesis of sodium zeolites from natural and modified diatomite

    Microsoft Academic Search

    A. Chaisena; K. Rangsriwatananon

    2005-01-01

    This project is related with the synthesis of sodium zeolites using natural and modified diatomite as starting materials. The synthesis process consisted of conventional hydrothermal alkaline activation, using NaOH as reagent. The process was studied as a function of the starting material, temperature, time, solid\\/liquid ratio and activation reagent concentration. The resulting crystals were identified by X-ray diffraction, and characterized

  4. Sensitized near infrared emission from lanthanide-exchanged zeolites

    SciTech Connect

    Monguzzi, A.; Macchi, G.; Meinardi, F.; Tubino, R. [CNR-INFM and Department of Material Science, University of Milano-Bicocca, via Cozzi 53, I-20125 Milano (Italy); Burger, M. [Department of Physics A. Volta, University of Pavia, via Bassi 6, I-27100 Pavia (Italy); Calzaferri, G. [University of Berne, Department of Chemistry and Biochemistry, Freiestr. 3 CH-3012 Berne (Switzerland)

    2008-03-24

    In this work, we present an alternative approach to sensitize the near infrared emission of Er{sup 3+} ions (used in telecom applications) by exploiting the geometrical confinement occurring in porous zeolites structures. The sensitization of the Ln ion is obtained by energy transfer between a suitable organic molecule acting as an antenna and the emitting ion arranged in closed proximity, thus, avoiding the limits imposed by the coordination chemistry.

  5. A study of platinum-thulium\\/KL zeolite reforming catalysts

    Microsoft Academic Search

    Xiangming Fang; Fengyi Li; Laitao Luo

    1996-01-01

    The PtKL catalyst modified by Tm2O3 has been characterized by the n-hexane, methylcyclopentane (MCP) and cyclohexane conversion reaction. The results show that the activity for the aromatization on Pt-Tm\\/KL zeolite catalysts containing thulium ranging from 0.05 to 0.2 wt.-% is higher than that on the PtKL catalyst, and the stability of the modified catalysts is remarkably improved. The influence of

  6. Direct electron crystallographic determination of zeolite zonal structures

    Microsoft Academic Search

    Douglas L. Dorset; Christopher J. Gilmore; Jose Luis Jorda; Stavros Nicolopoulos

    2007-01-01

    The prospect for improving the success of ab initio zeolite structure investigations with electron diffraction data is evaluated. First of all, the quality of intensities obtained by precession electron diffraction at small hollow cone illumination angles is evaluated for seven representative materials: ITQ-1, ITQ-7, ITQ-29, ZSM-5, ZSM-10, mordenite, and MCM-68. It is clear that, for most examples, an appreciable fraction

  7. Origin of strong acidity in lanthanum-exchanged zeolites 

    E-print Network

    Carvajal Freese, Ralf R.

    1989-01-01

    compositions for the hydrocarbon process include Czo-C4o molecules comprised of single and fused aromatic rings, naphthene rings, and paraffins (3). These molecules are converted mainly by acid-catalyzed reactions, such as isomerization, polymerization...ORIGIN OF STRONG ACIDITY IN LANTHANUM- EXCHANGED ZEOLITES A Thesis by RALF R. CARVAJAL FREESE Submitted to the Office of Graduate Studies of Texas A&M University in the partial fulfillment of the requirements for the degree of MASTER...

  8. A Simple Model for Strontium Breakthrough on Zeolite Columns

    Microsoft Academic Search

    J. J. Perona; A. C. Coroneos; T. E. Kent; S. A. Richardson

    1995-01-01

    The Process Waste Treatment Plant (PWTP) at the Oak Ridge National Laboratory is designed to remove radioactive contaminants, principally Sr, from process wastewater. Planned upgrades to the PWTP will use chabazite zeolite columns. Pilot-scale studies have shown that mass transfer zone lengths increase from 10 to about 30 cm as the superficial velocity increases from 5.5 to 22 cm\\/min. Calculations

  9. UO2 Sorption in Natural Mexican Erionite and Y Zeolite

    Microsoft Academic Search

    M. T. Olguín; M. Solache; M. Asomoza; D. Acosta; P. Bosch; S. Bulbulian

    1994-01-01

    The use of Y zeolite and erionite to remove UO2 ions from aqueous solutions has been investigated. The effect of temperature, the concentration of UO2 uptake, the diffusion coefficients, and the ion-exchange isotherms were also studied. X-ray diffraction, thermal analyses, and transmission electron microsocopy were used to characterize the solids. The UO2 content was determined by neutron activation analysis. The

  10. Adsorption of SO 2 from Wet Mixtures on Hydrophobic Zeolites

    Microsoft Academic Search

    Sabina A. Rouf; Mladen Ei?

    1998-01-01

    Breakthrough curve measurements of SO2 and water vapor were carried out on a number of selected mordenite and pentasil zeolites from their binary and ternary mixtures with CO2 at 50 and 100°C. SO2 capacities of these samples were found to be significantly reduced by the presence of water. Competitive adsorption led to unusually high overshoot peaks of SO2 breakthrough curves.

  11. Skeletal Isomerization of 1Butene on MCM-22 Zeolite Catalyst

    Microsoft Academic Search

    M. A. Asensi; A. Corma; A. Mart??nez

    1996-01-01

    The skeletal isomerization of 1-butene has been studied on two MCM-22 zeolite catalysts synthesized with different Si\\/Al ratios, i.e., 15 and 47, under a wide range of operating conditions. Product yields are a function ofn-butene conversion, and a maximum of isobutene yield is found at ca. 50% conversion. Besides isobutene, propylene and pentenes, which are formed by dimerization-cracking reactions, are

  12. Formaldehyde base catalysis by NaX zeolite

    Microsoft Academic Search

    S. Trigerman; E. Biron; A. H. Weiss

    1977-01-01

    Reactions of formaldehyde to produce formose sugars at 95°C in aqueous solutions were studied over a trickle bed of NaX Zeolite spheres. When effluent pH was in the range of 5 to 7, a rapid irreversible catalyst deactivation from an initial 50% conversion occurred. The catalyst was destroyed in less than five hours by formic acid produced by the undesired

  13. Kinetic Parameters of Polyethylene Degradation by the Natural Zeolite Chabazite

    Microsoft Academic Search

    V. J. Fernandes; A. S. Araujo; R. A. Medeiros; J. R. Matos; L. P. Mercuri; A. O. Silva; D. M. A. Melo

    1999-01-01

    High-density polyethylene (PE) was subjected to thermal degradation alone and in the presence of an ammonium-exchanged zeolite\\u000a chabazite (CHA\\/PE). The processes were carried out in a reactor connected online to a gas chromatograph\\/mass spectrometer\\u000a in order to analyse the evolved products. Polymer degradation was also evaluated by thermogravimetry, from room temperature\\u000a up to 800°C, under a dynamic nitrogen atmosphere, with

  14. Origin of strong acidity in lanthanum-exchanged zeolites

    E-print Network

    Carvajal Freese, Ralf R.

    1989-01-01

    reagents for zeolite dealumination (57, 58). Fluoride ions are excellent complexing agents, and aluminum can be extracted from the framework in the form ol' water soluble complexes. In addition, ammonium hexafluorosilicate forms monomeric silicon species.... DEALUMINATION WITH AMMONIUM HEXAFLUOROSILICATE 27 D. X-RAY DIFFRACTION. . E. SOLID STATE MAGIC ANGLE SPINNING NMR. . . . . I. Aluminum content evaluation. 2. Evaluation of acid sites. . F. FOURIER TRANSFORM IR, G. SAMPLE PREPARATION FOR ELEMENTAL ANALYSIS...

  15. Development of a dissolved oxygen sensor using tris(bipyridyl) ruthenium (II) complexes entrapped in highly siliceous zeolites

    Microsoft Academic Search

    Pramatha Payra; Prabir K. Dutta

    2003-01-01

    Defect-free highly siliceous zeolites were prepared by dealumination of zeolite Y using silicon tetrachloride. Tris(bipyridyl) ruthenium (II) complex, [Ru(bpy)3]2+, was synthesized inside the supercages of the highly siliceous faujasitic zeolites using neutral Ru(bpy)Cl3 as the starting material. The conventional procedure using ion-exchange of hexammine ruthenium could not be used because of the lack of ion-exchange sites in the siliceous zeolites.

  16. Effects of capillary condensation on adsorption and thermal desorption dynamics of water in zeolite 13X and layered beds

    Microsoft Academic Search

    Hyungwoong Ahn; Chang-Ha Lee

    2004-01-01

    The effects of capillary condensation on the adsorption and thermal desorption dynamics of water in zeolite 13X beds and layered beds with zeolite 13X\\/silica gel or zeolite 13X\\/alumina were experimentally and theoretically studied. As the equilibrium isotherm of water on zeolite 13X pellet was found to be most favorable at a low relative humidity and indicated capillary condensation at a

  17. Synthetic zeolites and other microporous oxide molecular sieves.

    PubMed

    Sherman, J D

    1999-03-30

    Use of synthetic zeolites and other microporous oxides since 1950 has improved insulated windows, automobile air-conditioning, refrigerators, air brakes on trucks, laundry detergents, etc. Their large internal pore volumes, molecular-size pores, regularity of crystal structures, and the diverse framework chemical compositions allow "tailoring" of structure and properties. Thus, highly active and selective catalysts as well as adsorbents and ion exchangers with high capacities and selectivities were developed. In the petroleum refining and petrochemical industries, zeolites have made possible cheaper and lead-free gasoline, higher performance and lower-cost synthetic fibers and plastics, and many improvements in process efficiency and quality and in performance. Zeolites also help protect the environment by improving energy efficiency, reducing automobile exhaust and other emissions, cleaning up hazardous wastes (including the Three Mile Island nuclear power plant and other radioactive wastes), and, as specially tailored desiccants, facilitating the substitution of new refrigerants for the ozone-depleting chlorofluorocarbons banned by the Montreal Protocol. PMID:10097059

  18. The safety of synthetic zeolites used in detergents.

    PubMed

    Fruijtier-Pölloth, Claudia

    2009-01-01

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

  19. Mononuclear iridium dinitrogen complexes bonded to zeolite HY.

    PubMed

    Yang, Dong; Chen, Mingyang; Martinez-Macias, Claudia; Dixon, David A; Gates, Bruce C

    2015-01-01

    The adsorption of N2 on structurally well-defined dealuminated HY zeolite-supported iridium diethylene complexes was investigated. Iridium dinitrogen complexes formed when the sample was exposed to N2 in H2 at 298?K, as shown by infrared spectra recorded with isotopically labeled N2 . Four supported species formed in various flowing gases: Ir(N2 ), Ir(N2 )(N2 ), Ir(C2 H5 )(N2 ), and Ir(H)(N2 ). Their interconversions are summarized in a reaction network, showing, for example, that, in the presence of N2 , Ir(N2 ) was the predominant dinitrogen species at temperatures of 273-373?K. Ir(CO)(N2 ) formed transiently in flowing CO, and in the presence of H2 , rather stable iridium hydride complexes formed. Four structural models of each iridium complex bonded at the acidic sites of the zeolite were employed in a computational investigation, showing that the calculated vibrational frequencies agree well with experiment when full calculations are done at the level of density functional theory, independent of the size of the model of the zeolite. PMID:25381885

  20. CO2 adsorption in amine-grafted zeolite 13X

    NASA Astrophysics Data System (ADS)

    Bezerra, Diôgo P.; Silva, Francisco W. M. da; Moura, Pedro A. S. de; Sousa, Allyson G. S.; Vieira, Rodrigo S.; Rodriguez-Castellon, Enrique; Azevedo, Diana C. S.

    2014-09-01

    The adsorption of CO2 on Zeolite 13X functionalized with amino groups was studied. Adsorbent functionalization was carried out by grafting with different loads of monoethanolamine (MEA). The adsorbents were characterized by N2 adsorption/desorption isotherms at 77 K, x-ray diffraction, TGA, in situ FTIR, XPS and adsorption microcalorimetry. CO2 isotherms were studied in a gravimetric device up to 10 bar at 298 and 348 K. It was found that increasing loads of amine to the adsorbent tend to reduce micropore volume of the resulting adsorbents by pore blocking with MEA. There is experimental evidence that part of the loaded MEA is effectively covalently bonded to the zeolitic structure, whereas there is also physisorbed excess MEA which will eventually be desorbed by raising the temperature beyond MEA boiling point. Heats of adsorption at nearly zero coverage indicate that some of the adsorbed CO2 reacts with available amino groups, which agrees with the finding that the adsorption capacity increases with increasing temperature for the modified zeolite with the highest MEA load.