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1

Amphiphilic organosilane-directed synthesis of crystalline zeolite with tunable mesoporosity  

Microsoft Academic Search

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

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

2006-01-01

2

Catalytic pyrolysis using UZM-44 aluminosilicate zeolite  

DOEpatents

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

Nicholas, Christopher P; Boldingh, Edwin P

2013-12-17

3

Catalytic pyrolysis using UZM-44 aluminosilicate zeolite  

DOEpatents

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

Nicholas, Christopher P; Boldingh, Edwin P

2014-04-29

4

Catalytic pyrolysis using UZM-39 aluminosilicate zeolite  

DOEpatents

A new family of coherently grown composites of TUN and IMF zeotypes has been synthesized and 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.

Nicholas, Christopher P; Boldingh, Edwin P

2014-10-07

5

Catalytic pyrolysis using UZM-39 aluminosilicate zeolite  

DOEpatents

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

Nicholas, Christpher P; Boldingh, Edwin P

2013-12-17

6

MFI lamellae are unique among the availa-ble aluminosilicate zeolite lamellae because they  

E-print Network

MFI lamellae are unique among the availa- ble aluminosilicate zeolite lamellae because they have the potential of single­unit cell layers in applications beyond petrochemical processing. Branching of zeolite- plicable to all zeolite structures that can (i) be grown anisotropically as thin layers and (ii) can

Zare, Richard N.

7

Zeolites  

NASA Technical Reports Server (NTRS)

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

1992-01-01

8

Amphiphilic organosilane-directed synthesis of crystalline zeolite with tunable mesoporosity  

NASA Astrophysics Data System (ADS)

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

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

2006-09-01

9

Facile synthesis of mesoporous aluminosilicates constructed with crystalline microporous frameworks  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

10

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

PubMed

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

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

2014-11-12

11

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

E-print Network

for AdVanced Microscopy and Microanalysis, UniVersity of California, RiVerside, California 92521 with mesopore sizes. The nucleation maximum coincides temporally with development of pores with sizes that is capable of identifying presence of small amounts of crystalline zeolite material in amorphous medium

Bao, Xinhe

12

Diameter and Chirality Distribution of SWNTs Grown from Zeolite Surfaces  

E-print Network

Diameter and Chirality Distribution of SWNTs Grown from Zeolite Surfaces Yoichi Murakami1-8656 Zeolites are microporous, crystalline aluminosilicates constructed from tetrahedral base units. We have been using the b-surfaces of silicalite-1 zeolite (framework: MFI) as catalyst support for catalytic

Maruyama, Shigeo

13

Characterization of zeolite L nanoclusters  

Microsoft Academic Search

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

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

1995-01-01

14

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

E-print Network

Methyl rotational tunneling dynamics of p-xylene confined in a crystalline zeolite host Sankar-xylene confined in nanoporous zeolite crystals has been measured by inelastic neutron scattering INS and proton to the methyl-zeolite interactions. The INS tunneling spectra from the crystals space group P212121 with four

Nair, Sankar

15

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

E-print Network

Zeolites are crystalline, porous aluminosilicates; while a pure silicate structure is charge-neutral, the substitution of A1³? for Si?? creates in the framework a negative charge, which can be compensated by a proton that ...

Lo, Cynthia

2005-01-01

16

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

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

17

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

SciTech Connect

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

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

2001-10-30

18

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

19

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

PubMed

One of the challenges in material science has been to prepare macro- or mesoporous zeolite. Although examples of their synthesis exist, there is a need for a facile yet versatile approach to such hierarchical structures. Here we report a concept for designing a single quaternary ammonium head amphiphilic template with strong ordered self-assembling ability through ?-? stacking in hydrophobic side, which stabilizes the mesostructure to form single-crystalline mesostructured zeolite nanosheets. The concept is demonstrated for the formation of a new type of MFI (zeolite framework code by International Zeolite Association) nanosheets joined with a 90° rotational boundary, which results in a mesoporous zeolite with highly specific surface area even after calcination. Low binding energies for this self-assembling system are supported by a theoretical analysis. A geometrical matching between the arrangement of aromatic groups and the zeolitic framework is speculated for the formation of single-crystalline MFI nanosheets. PMID:24957696

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

2014-01-01

20

Interaction of Dimethylmethylphosphonate with Zeolite Y: Impedance-Based Sensor for Detecting Nerve Agent Simulants  

E-print Network

-exchanged zeolites as well as external surface modification with ceria to deactivate acidic groups. A mechanism air. Introduction Zeolites are crystalline aluminosilicates with pores and channels of molecular), surface acoustic wave arrays (e.g., M90), and gas chromatography-mass spectrometry devices (e.g., Hapsite

Dutta, Prabir K.

21

Growth of zeolite crystals in the microgravity environment of space  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

22

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

23

Location of platinum clusters in PtCaY and PtNaY zeolites  

E-print Network

) spectra of PtNaY after reduction in flowing hydrogen in increments of 100 C/hr to 350'C 61 63 65 INTRODUCTION In heterogeneous catalysis, frequently used supports for active group VIII metals are zeolites, which are crystalline aluminosilicates. A... metal-loaded catalyst may be prepared by exchanging cations into the zeolite structure. Catalytic activity is obtained by the reduction of the cation to metal. In order to understand the properties of metal-exchanged zeolites it is important...

Treybig, Duane Steven

1980-01-01

24

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

NASA Astrophysics Data System (ADS)

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

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

2001-12-01

25

Co-development of Crystalline and Mesoscopic Order in Mesostructured Zeolite Nanosheets.  

PubMed

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

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

2015-01-12

26

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

Microsoft Academic Search

Millions of gallons of high-level radioactive waste are contained in underground tanks at U.S. Department of Energy sites such as Hanford and Savannah River. Most of the radioactivity is due to 137Cs and 90Sr, which must be extracted in order to concentrate the waste. An ion exchanger, crystalline silicotitanate IONSIV IE911, is being considered for separation for Cs at the

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

2001-01-01

27

Conversion of rice husk ash to zeolite beta.  

PubMed

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

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

2006-01-01

28

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

ERIC Educational Resources Information Center

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

Saini, Vipin K.; Pires, Joao

2012-01-01

29

Microwave-hydrothermal synthesis of Al-substituted tobermorite from zeolites  

Microsoft Academic Search

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

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

2002-01-01

30

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

Microsoft Academic Search

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

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

1985-01-01

31

Microporous Zeolite MembranesMicroporous Zeolite Membranes and Their Potential for Hand Their Potential for H22 ProductionProduction  

E-print Network

Microporous Zeolite MembranesMicroporous Zeolite Membranes and Their Potential for Hand interest." 22 Zeolites andZeolites and ZeotypesZeotypes ZeoliteZeolite ­­ A crystallineA crystalline zeolites.same structure as known zeolites. MFI Zeolite #12;"...exceptional service in the national interest

32

Investigations on P zeolites: synthesis, characterisation, and structure of highly crystalline low-silica NaP  

Microsoft Academic Search

A highly crystalline sample of low-silica zeolite P was synthesised. It was, therefore, possible to investigate the structure of Na8Al8Si8O32·15.2H2O on the basis of highly resolved synchrotron data and to correlate structural information with data from SEM, DTA\\/TGA, temperature-dependent DRIFTS, transmittance infrared, Raman, 29Si MAS NMR, and 27Al MAS NMR experiments. The crystal structure of low-silica NaP has been determined

B. R Albert; A. K Cheetham; J. A Stuart; C. J Adams

1998-01-01

33

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

NASA Astrophysics Data System (ADS)

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

Luscher, Walter G.

34

Synthesis strategies in the search for hierarchical zeolites.  

PubMed

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

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

2013-05-01

35

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

PubMed

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

Hui, K S; Chao, C Y H

2006-09-01

36

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

Microsoft Academic Search

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

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

2011-01-01

37

Chemically feasible hypothetical crystalline networks  

NASA Astrophysics Data System (ADS)

Our systematic enumeration of 4-connected crystalline networks (that is, networks in which each atom is connected to exactly four neighbours) used recent advances in tiling theory to evolve over 900 topologies. The results are relevant to the structures of zeolites and other silicates, aluminophosphates (AlPOs), oxides, nitrides, chalcogenides, halides, carbon networks, and even to polyhedral bubbles in foams. Given their importance as molecular sieves, ion exchangers, catalysts and catalyst supports, we have applied the results to microporous aluminosilicates and aluminophosphates (zeolites). Zeolite chemistry has to date produced 152 distinct types of structure. However, it was always clear that although many further structures can be synthesised, only a fraction of the mathematically generated networks would be chemically feasible (many are 'strained' frameworks requiring unrealistic bond lengths and bond angles), and that an effective 'filtering' process is needed to identify the most plausible frameworks. Here, we describe the use of computational chemistry methods to calculate optimized structural parameters, framework energies relative to ?-quartz, volumes accessible to sorption, and X-ray diffraction patterns for systematically enumerated hypothetical 4-connected crystalline frameworks. Structures were treated as silica polymorphs with the empirical formula SiO2, and their energies were minimized.

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

2004-04-01

38

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

E-print Network

Cesium incorporation and diffusion in cancrinite, sodalite, zeolite, and allophane Jarai Mon of silicate minerals and precipitation of new aluminosilicate minerals. Cancrinite, sodalite, LTA zeolite in sodalite and cancrinite was far more difficult to replace than that in LTA zeolite or allophane. Most

Flury, Markus

39

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

SciTech Connect

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

Raman, S.

1993-12-01

40

Microprobes aluminosilicate ceramic membranes  

DOEpatents

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

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

1993-01-01

41

Spectroscopic signatures of nitrogen-substituted zeolites.  

PubMed

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

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

2008-11-12

42

Core-shell strain structure of zeolite microcrystals  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

43

Zeolite with trimodal porosity by desilication of zeolite nanocrystals aggregate  

SciTech Connect

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

Wang Yuxin; Liu Kaituo [Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese academy of Sciences, 189 Songling road, Qingdao 266101 (China) [Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese academy of Sciences, 189 Songling road, Qingdao 266101 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100049 (China); He Tao; Wu Jinhu [Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese academy of Sciences, 189 Songling road, Qingdao 266101 (China)] [Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese academy of Sciences, 189 Songling road, Qingdao 266101 (China); Fang Yunming, E-mail: fangym@qibebt.ac.cn [Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese academy of Sciences, 189 Songling road, Qingdao 266101 (China)

2012-10-15

44

Functionalized Amorphous Aluminosilicates  

NASA Astrophysics Data System (ADS)

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

Mesgar, Milad

45

Properties and applications of zeolites.  

PubMed

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

Rhodes, Christopher J

2010-01-01

46

A new synthesis procedure for titanium-containing zeolites under strong alkaline conditions and the catalytic activity for partial oxidation and photocatalytic decomposition  

Microsoft Academic Search

A new synthesis procedure for titanium-containing aluminosilicate zeolites has been obtained using a clear colloidal dispersion (sol) which was prepared with titanium isopropoxide, water, hydrochloric acid and colloidal silica, Ludox. When NaY, KL, offretite, mordenite and ZSM-5 zeolites were crystallized from the sol following conventional hydrothermal crystallization procedures, all the aluminosilicate zeolites showed the same X-ray absorption fine structure at

Ja Hun Kwak; Sung June Cho; Ryong Ryoo

1996-01-01

47

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

PubMed

C-dots obtained in the homogeneous phase may exhibit a broad particle size distribution. The formation of C-dots within nanometric reaction cavities could be a methodology to gain control on their size distribution. Among the various possibilities, in the present work, the cavities of small pore size zeolites have been used to confine C-dots generated by the pyrolysis of the organic structure directing agent present in the synthesis of these crystalline aluminosilicates. To explore this methodology, ITQ-29 zeolite having a Linde type A (LTA) structure was prepared as pure silica with 4-methyl-2,3,6,7-tetrahydro-1H,5H-pyrido[3.2.1-ij]quinolinium as the organic structure directing agent. Pyrolysis under an inert atmosphere at 550 °C of a pure-silica ITQ-29 sample (cubic particles of 4 ?m edge) renders a highly fluorescent zeolite containing about 15 wt% of the carbonised residue. While another small pore zeolite, ITQ-12 (ITW), also renders photoluminescent C-dots under similar conditions, medium or large pore zeolites, such as silicalite (MFI) or pure silica Beta (BEA), failed to produce fluorescent powders under analogous thermal treatment and only decomposition and complete removal of the corresponding quaternary ammonium ion templates was observed for these zeolites. The dissolution of the pyrolysed ITQ-29 zeolite framework and the extraction of the carbon residue with ethyl acetate have allowed the characterisation of C-dots with particle sizes between 5 and 12 nm and a photoluminescence quantum yield of 0.4 upon excitation at 350 nm that is among the highest reported for non-surface functionalized C-dots. Photoluminescence varies with the excitation wavelength and is quenched by oxygen. Pyrolysed ITQ-29 powders can act as fluorescent oxygen sensors. PMID:25516465

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

2015-01-22

48

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

49

Synthesis and testing of nanosized zeolite Y  

NASA Astrophysics Data System (ADS)

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

Karami, Davood

50

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

51

Sodium Diffusion through Aluminum-Doped Zeolite BEA System: Effect of Water Solvation Hyungjun Kim, Wei-Qiao Deng, and William A. Goddard, III*  

E-print Network

Sodium Diffusion through Aluminum-Doped Zeolite BEA System: Effect of Water Solvation Hyungjun Kim To investigate the effect of hydration on the diffusion of sodium ions through the aluminum-doped zeolite BEA absorption into aluminosilicate zeolite structure under various conditions of vapor pressure and temperature

Goddard III, William A.

52

The growth of zeolites A, X and mordenite in space  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

53

Hyperbolic and elliptic layer warping in some sheet alumino-silicates  

NASA Astrophysics Data System (ADS)

The curvature of alumino-silicate structures related to imogolite and kaolinite is investigated using techniques derived from differential geometry and topology. It is demonstrated that the curvatures of these structures can be varied to give a limited range of “modulated” relatives, of both hyperbolic and elliptic curvature. These modulated structures may account for a number of soil minerals, the “poorly ordered non-crystalline aluminosilicates” (Wilson et al. 1988), including protoimogolite and allophane.

Hyde, S. T.

1993-08-01

54

Crystalline Membranes  

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

55

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

E-print Network

Zeolites DOI: 10.1002/anie.200702628 Aluminum Siting in Silicon-Rich Zeolite Frameworks: A Combined Sauer* Dedicated to Süd-Chemie on the occasion of its 150th anniversary Zeolites are crystalline. Silicon-rich zeolites (Si/Al > 12) such as ZSM-5 (MFI framework) have found particular attention

Sklenak, Stepan

56

Nanoclusters in Zeolite  

NASA Astrophysics Data System (ADS)

Nanoclusters of Se, Rb-Se, and Cs-Se were incorporated in the supercages of Y zeolite. Anomalous x-ray scattering established that the Se clusters take the form of weakly interacting chains with a disordered structure similar to that of amorphous Se, while the Rb-Se and Cs-Se clusters contain Se2-2 Zintl ions as in crystalline and liquid bulk phases. The Raman spectra of the nanoclusters exhibit features found in the bulk disordered phases.

Armand, Pascale; Saboungi, Marie-Louise; Price, D. L.; Iton, L.; Cramer, Cornelia; Grimsditch, M.

1997-09-01

57

Dry-gel synthesis of shaped binderless zeolites composed of nanosized ZSM-5  

NASA Astrophysics Data System (ADS)

Shaped binderless ZSM-5 zeolites are prepared via a dry-gel conversion (DGC) technique from aluminosilicate extrudates, where the addition of seed gels not only provides crystal nuclei for rapid crystallization of zeolite but also controls the size of ZSM-5 crystal. Furthermore, the introduction of amine into the steam favors the formation of nanosized ZSM-5 zeolite. Especially, the morphology of these aluminosilicate extrudates well kept in the crystallization process. The obtained shaped zeolites are characterized by X-ray diffraction (XRD), nitrogen adsorption analysis, and scanning electron micrographs (SEM). The shaped zeolites show hierarchical structure with high mesopore volume (0.22 cm3 g-1) and demonstrate similar activity as commercial ZSM-5 samples in the transformation of i-propanol to hydrocarbons reaction.

Yue, Ming Bo; Yang, Na; Jiao, Wen Qian; Wang, Yi Meng; He, Ming-Yuan

2013-06-01

58

Towards a sustainable manufacture of hierarchical zeolites.  

PubMed

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

Verboekend, Danny; Pérez-Ramírez, Javier

2014-03-01

59

Fire-resistant Aluminosilicate Composites  

Microsoft Academic Search

The fire response of a potassium aluminosilicate (Geopolymer) matrix carbon fiber composite was measured and the results compared to organic matrix composites being used for transportation, military, and infrastructure applica- tions. At irradiance levels of 50 kW m~2 typical of the heat flux in a well-developed fire, glass- or carbon-reinforced polyester, vinylester, epoxy, bismaleimde, cyanate ester, polyimide, phenolic, and engineering

Richard E. Lyon; P. N. Balaguru; Andrew Foden; Usman Sorathia; Joseph Davidovits; Michel Davidovics

1997-01-01

60

21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.  

Code of Federal Regulations, 2011 CFR

...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...

2011-04-01

61

21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.  

Code of Federal Regulations, 2010 CFR

...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...

2010-04-01

62

21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.  

Code of Federal Regulations, 2010 CFR

...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...

2010-04-01

63

21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.  

Code of Federal Regulations, 2011 CFR

...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...

2011-04-01

64

21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.  

Code of Federal Regulations, 2012 CFR

...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...

2012-04-01

65

21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.  

...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...

2014-04-01

66

21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.  

Code of Federal Regulations, 2013 CFR

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

2013-04-01

67

21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.  

Code of Federal Regulations, 2013 CFR

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

2013-04-01

68

21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.  

...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...

2014-04-01

69

21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.  

Code of Federal Regulations, 2012 CFR

...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...

2012-04-01

70

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

71

Basic concepts of the crystallization from aqueous solutions: The example of aluminum oxy(hydroxi)des and aluminosilicates  

NASA Astrophysics Data System (ADS)

This overview features the chemical background on condensation phenomena of the aluminum cation in aqueous solution. The formation of polycationic molecular clusters and nanosized solid phases of aluminum oxy(hydroxi)des is interpreted with illustrative mechanisms, building a bridge between solution chemistry and solid-state chemistry. The formation of the main structural types of aluminosilicates (zeolites, clays, imogolite) is also illustrated through the aqueous chemistry of aluminum and silicates.

Jolivet, Jean-Pierre; Chanéac, Corinne; Chiche, David; Cassaignon, Sophie; Durupthy, Olivier; Hernandez, Julien

2011-02-01

72

Fracture of an aluminosilicate fiberboard  

SciTech Connect

Mode-I fracture of aluminosilicate fiberboard that is used in large mirror casting molds was studied. The material was idealized as a transversely isotropic, layered composite that was composed of planar sheets of crosslinked fibers. Plastic constants, the toughness (K{sub R}) curve, and the fracture work were measured at room temperature. The observed rising K{sub R} behavior was attributed to crack bridging. Experimental measurements of the bridging stress were made using a specimen-renotching technique. Relationships between the bridging stress, K{sub R}, and fracture work were explored and shown to be consistent.

Olbert, B.H. [Univ. of Arizona, Tucson, AZ (United States). Steward Observatory Mirror Lab.; Schenck, S.R. [Rex Roto Corp., Fowlerville, MI (United States)

1997-11-01

73

Water behaviour in nanoporous aluminosilicates.  

PubMed

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

Smirnov, Konstantin S; Bougeard, Daniel

2010-07-21

74

Preparation and characterization of host (mesoporous aluminosilicate material)–guest (semiconductor nanoparticles) nanocomposite materials  

Microsoft Academic Search

We report the optical and structural properties of NiS and CoS nanoparticles in AlMCM-41 zeolite. The samples were obtained by sulfidation of the Ni2+ and Co2+ ion exchange zeolite in a Na2S solution at room temperature. The optical properties of the samples were studied by UV–Vis spectroscopy. Their crystalline structure and morphology were studied by XRD and scanning electron microscopy

A. Pourahmad; Sh. Sohrabnezhad; M. S. Sadjadi; K. Zare

2008-01-01

75

Preparation and characterization of zeolitic membrane  

SciTech Connect

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

Shuanshi Fan; Chunhua Li; Jinqu Wang [Dalian Univ. of Technology (China)

1994-12-31

76

Influence of Zeolite Catalyst Supports on the Synthesis of Single-Walled Carbon Nanotubes  

E-print Network

1 Influence of Zeolite Catalyst Supports on the Synthesis of Single-Walled Carbon Nanotubes; catalytic CVD; metal catalyst; Zeolite ABSTRACT: Choice of the catalyst support is an important factor) method. Zeolites, which are a class of microporous crystalline material, have also been known

Maruyama, Shigeo

77

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

NASA Astrophysics Data System (ADS)

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

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

2010-09-01

78

High-aluminum-affinity silica is a nanoparticle that seeds secondary aluminosilicate formation.  

PubMed

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

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

2013-01-01

79

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

PubMed Central

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

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

2013-01-01

80

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

PubMed

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

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

2014-04-25

81

An introduction to zeolite molecular sieves  

Microsoft Academic Search

This book covers the following topics: What is a zeolite ; Natural zeolites and their occurrence; The structure of zeolites; Zeolite structure identification and characterization; Zeolite syntheses; Zeolites as ion exchangers; Zeolites as molecular sieves and drying agents; The stabilities of zeolite structures and their modification; Zeolites as catalysts; Zeolite-like materials (Zeotypes) containing elements other than Si or Al in

A. Dyer

1988-01-01

82

Database of Zeolite Structures  

NSDL National Science Digital Library

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

83

Characterisation of the textural properties of chemically dealuminated Y zeolites  

Microsoft Academic Search

The main objective of this work is to characterise the textural properties of a series of Y zeolites dealuminated by ammonium hexafluorosilicate treatment. It was observed that the fluorosilicate treatment produced a highly crystalline product with a contracted unit cell. Both textural and XRD analysis confirmed the samples to be at least 95% crystalline for dealumination degrees ?50%. According to

R. López-Fonseca; B. de Rivas; J. I. Gutiérrez-Ortiz; J. R. González-Velasco

2002-01-01

84

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

PubMed

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

Shawabkeh, Reyad Awwad

2006-07-15

85

Studies on secondary synthesis and characterisation of boron-modified ZSM-5 zeolites  

Microsoft Academic Search

A post synthesis modification (“secondary synthesis”) of aluminosilicates has been described in order to produce boron-containing zeolites of the pentasile type: Isomorphic incorporation of boron is verified by means of 11B MAS NMR spectroscopy, laser ablation ICP AES and X-ray powder diffraction. 27Al MAS NMR spectroscopy is used for further characterisation of the resulting material. In order to create lattice

Brit Meier; Wladimir Reschetilowski

1994-01-01

86

Conventional hydrothermal synthesis of NaA zeolite from cupola slag and aluminum sludge  

Microsoft Academic Search

Na-A type zeolites were prepared from two industrial wastes: the solid by-product of cupola slag and aluminum sludge from an aluminum plating plant. Two preparation methods using the same starting material compositions were carried out. In the first method, alkaline fusion was introduced, followed by the hydrothermal treatment to obtain sodium aluminosilicate which was then crystallized in NaOH solution under

Rewadee Anuwattana; Pojanie Khummongkol

2009-01-01

87

Characteristics of aluminosilicate hydrogels related to commercial “Geopolymers”  

Microsoft Academic Search

To establish aluminosilicate hydrogels as a model system for processing and developing commercial Geopolymer binders, various aluminosilicate hydrogels were synthesized and characterized by multiple techniques. Aluminosilicate hydrogel microstructure was investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD), solid-state magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy and small amplitude oscillatory rheometry. The [SiO2]\\/[Na2O], [SiO2]\\/[Al2O3] and salt content of the

J. W. Phair; J. D. Smith; J. S. J. Van Deventer

2003-01-01

88

Zeolite catalysis: technology  

SciTech Connect

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

Heinemann, H.

1980-07-01

89

Inelastic X-ray Scattering Studies of Zeolite Collapse  

NASA Astrophysics Data System (ADS)

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

Greaves, G. Neville; Kargl, Florian; Ward, David; Holliman, Peter; Meneau, Florian

2009-01-01

90

Inelastic X-ray Scattering Studies of Zeolite Collapse  

SciTech Connect

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

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

2009-01-29

91

Exhausted fluid catalytic cracking catalysts as raw materials for zeolite synthesis  

Microsoft Academic Search

The utilization of exhausted fluid catalytic cracking (FCC) catalysts as raw materials for the zeolite synthesis was analyzed. Samples of the catalysts directly released from FCC units and the corresponding impact grinding pretreated samples were used. Mechanical treatment was observed to decrease catalyst crystallinity and particle size. The catalyst reactivity was analyzed in terms of conversion in zeolite and product

Elena I. Basaldella; Julio C. Paladino; Mariana Solari; Graciela M. Valle

2006-01-01

92

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

Microsoft Academic Search

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

H. M. Yin; B. Lai

2012-01-01

93

Zeolite thin films: from computer chips to space stations.  

PubMed

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

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

2010-02-16

94

Condensation of aluminosilicate gels—model system for geopolymer binders  

Microsoft Academic Search

The reaction of geopolymer binders can be subdivided into two more or less parallel reactions, (1) the dissolution of reactable silicate and aluminate monomers from the reactive solid material and (2) the condensation to an aluminosilicate gel. Due to the wide range of possible raw materials, the question arises whether the Si\\/Al ratio of the hardened aluminosilicate network is predominated

A. Buchwald; H.-D. Zellmann; Ch. Kaps

2011-01-01

95

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

96

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

SciTech Connect

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

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

1997-10-01

97

Influence of soluble aluminosilicate complex formation on imogolite solubility determination  

NASA Astrophysics Data System (ADS)

In a earlier paper (Su and Harsh, 1994), we presented a free energy of formation for imogolite based on solubility studies and including a formation constant for a monomeric, soluble aluminosilicate complex (Browne and Driscoll, 1992). Farmer and Lumsdon (1994) have argued that the aluminosilicate formation constant is too high, calling into question solubility determinations utilizing this value. We have recalculated the log K value for imogolite dissolution using the new value for the aluminosilicate species. The result is a slight, but insignificant, increase in the log K for imogolite dissolution, supporting our earlier contention that the free energy of imogolite is larger than found in previous studies.

Su, Chunming; Harsh, James B.

1996-11-01

98

Photoelastic response of alkaline earth aluminosilicate glasses.  

PubMed

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

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

2012-02-01

99

Synthesis and catalytic applications of novel mesoporous aluminosilicate molecular sieves  

SciTech Connect

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

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

1997-12-31

100

Reaction of vitreous silicates and sodium aluminosilicates with aqueous solutions  

Microsoft Academic Search

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

S. K. Dubrovo

1954-01-01

101

Direct synthesis of acidic aluminosilicate mesoporous molecular sieves  

SciTech Connect

A simple and versatile synthetic route, whereby primary amine surfactants are the template in the assembly of aluminosilicate inorganic species, is used to prepare aluminosilicate mesoporous molecular sieves in which Broensted acidity is generated by simply calcining the as-synthesized material. Al incorporation is accompanied by charge-balancing protonated amine molecules. Si and Al are incorporated into the mesoporous framework to yield materials with textural properties similar to those of MCM-41 but with substantially higher Broensted acidity.

Mokaya, R.; Jones, W. [Univ. of Cambridge (United Kingdom). Dept. of Chemistry

1996-12-31

102

Diagram of Zeolite Crystals  

NASA Technical Reports Server (NTRS)

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

2003-01-01

103

Hierarchical zeolites from class F coal fly ash  

NASA Astrophysics Data System (ADS)

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

Chitta, Pallavi

104

Composite zeolite membranes  

DOEpatents

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

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

2002-01-01

105

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

NASA Astrophysics Data System (ADS)

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

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

2005-09-01

106

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

PubMed

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

Gounder, Rajamani; Iglesia, Enrique

2012-02-21

107

Hydrothermal Synthesis and Characterization of Aluminum-Free Mn-? Zeolite: A Catalyst for Phenol Hydroxylation.  

PubMed

Zeolite beta, especially heteroatomic zeolite beta, has been widely used in the industries of fine chemicals and petroleum refining because of its outstanding thermal stability, acid resistance, and unique 3-D open-frame structure. In this paper, aluminum-free Mn-? zeolite was hydrothermally synthesized in the SiO2-MnO2-(TEA)2O-NaF-H2O system. The effect of the chemical composition of the precursor mixture to the crystallization of the Al-free Mn-? zeolite was investigated. The synthesized Al-free Mn-? zeolite was characterized by inductively coupled plasma (ICP), XRD, thermogravimetric/differential thermal analysis (TG/DTA), N2 adsorption-desorption, FT-IR, UV-vis, X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM). The results show that the synthesized zeolite has a structure of ? zeolite with good crystallinity and Mn ions present in the framework of the zeolite. The synthesized Al-free Mn-? zeolite shows great catalytic activity toward the phenol hydroxylation reaction using H2O2 as the oxidant. Approximately 35% of phenol conversion and ?98% of dihydroxybenzene selectivity can be obtained under the optimal conditions. PMID:25556927

He, Zhen; Wu, Juan; Gao, Bingying; He, Hongyun

2015-02-01

108

Coating of silica sand with aluminosilicate clay.  

PubMed

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

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

2006-02-01

109

Preparation of functionalized zeolitic frameworks  

DOEpatents

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

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

2014-08-19

110

Preparation of functionalized zeolitic frameworks  

DOEpatents

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

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

2013-07-09

111

Preparation of functionalized zeolitic frameworks  

DOEpatents

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

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

2012-11-20

112

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

SciTech Connect

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.

Schneider, E.

1985-11-01

113

Adamantanes from petroleum with zeolites  

Microsoft Academic Search

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

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

1996-01-01

114

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

PubMed

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

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

2009-06-15

115

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

Microsoft Academic Search

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

Carol A Bessel; Debra R Rolison

1997-01-01

116

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

117

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

SciTech Connect

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

Conrad Ingram; Mark Mitchell

2005-03-21

118

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

NASA Astrophysics Data System (ADS)

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

Kodumuri, Pradeep

2009-12-01

119

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

E-print Network

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

Shawabkeh, Reyad A.

120

Advances in nanosized zeolites  

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

121

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

122

The influence of metakaulinite crystallinity on the properties of a geopolymer  

Microsoft Academic Search

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

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

123

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

SciTech Connect

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

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

2011-03-15

124

Synthesis and characterization of zeolites prepared from industrial fly ash.  

PubMed

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

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

2014-09-01

125

A high acid mesoporous USY zeolite prepared by alumination  

NASA Astrophysics Data System (ADS)

A high-acidity HUSY zeolite with mesoporous structure was prepared by alumination with a dilute aqueous NaAlO2 solution and characterized by XRD, N2 adsorption, IR framework vibration and 29Si MAS NMR methods. The results indicated the extra-framework aluminum was reinserted into the tetrahedral framework through isomorphic substitution of framework Si (0Al) sites by Al ions, whereas the crystal and micropore structure were unaltered. FTIR spectra of hydroxyl vibrations and pyridine adsorbed on realuminated zeolites showed that the number of 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.

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

2013-01-01

126

Clinoptilolite zeolitized tuff from Central Alborz Range, North Iran  

NASA Astrophysics Data System (ADS)

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

Taghipour, Batoul

2010-05-01

127

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

PubMed

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

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

2012-05-23

128

Separations Using Zeolite Membranes  

Microsoft Academic Search

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

Joaquín Coronas; Jesús Santamaría

1999-01-01

129

Diffusion in zeolites  

Microsoft Academic Search

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

Douglas M. Ruthven

1995-01-01

130

Heterostructured layered aluminosilicate-itraconazole nanohybrid for drug delivery system.  

PubMed

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

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

2013-11-01

131

Zeolites in Tertiary coal from the Çayirhan mine, Beypazari, Turkey  

NASA Astrophysics Data System (ADS)

The study focuses on the mineralogy of the upper coal seam accumulated at the top of the Çoraklar Formation (Miocene), Beypazari, Turkey. This coal seam is laterally extensive and averages 3.0 m thick, varying from 1.0 to 4.9 m. Analcime and clinoptiolite comprise up to 80% of the mineral matter (which also includes feldspars, quartz and pyrite and traces of dolomite, clay minerals and apatite) in the coal from the Çayirhan mine. Zeolites were formed when sodium-rich solutions altered aluminosilicate epiclastic material derived from contemporaneous volcanic activity. The allocthonous organic matter accumulated as a result of detrital plant and epiclastic material from an adjacent fresh-water environment being washed into a saline lake in sufficient quantities to form peat with a high mineral matter content (29.7% mean mineral matter content in raw coal). Subsequent syngenetic alteration of the volcanic glass incorporated into the peat resulted in zeolite formation. Alteration of sodium-rich epiclastic material by sodium-rich solutions resulted in the formation of analcime, whilst alteration of calcium-rich epiclastic material by sodium-rich solutions resulted in the formation of clinoptilolite.

Whateley, M. K. G.; Querol, X.; Fernández-Turiel, J. L.; Tuncali, E.

1996-09-01

132

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

NASA Astrophysics Data System (ADS)

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.

Mysen, Bjorn O.

2006-05-01

133

Zeolite crystal growth in space  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

134

Zeolite exposure and associated pneumoconiosis  

SciTech Connect

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

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

1985-06-01

135

SO2 REMOVAL FROM FLUE GASES USING UTILITY SYNTHESIZED ZEOLITES  

SciTech Connect

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

Michael Grutzeck

1999-04-30

136

SO2 REMOVAL FROM FLUE GASES USING UTILITY SYNTHESIZED ZEOLITES  

SciTech Connect

It is well known that natural and synthetic zeolites (molecular sieves) can adsorb gaseous SO2 from flue gas and do it more efficiently than lime based scrubbing materials. Unfortunately their cost ($500-$800 per ton) has deterred their use in this capacity. It is also known that zeolites are easy to synthesize from a variety of natural and man-made materials. The overall objective of the current work has been to evaluate the feasibility of having a utility synthesize its own zeolites, on-site, from fly ash and other recycled materials and then use these zeolites to adsorb SO2 from their flue gases. Work to date has shown that the efficiency of the capture process is related to the degree of crystallinity and the type of zeolite that forms in the samples. Normally, those samples cured at 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.

MICHAEL GRUTZECK

1998-10-31

137

Structural effects induced by 2.5 MeV proton beam on zeolite 4A: Positron annihilation and X-ray diffraction study  

NASA Astrophysics Data System (ADS)

Structural changes induced by 2.5 MeV proton beam in zeolite 4A were studied at fluences of 1.1016, 8.1016 and 2.1017 ion/cm2. Positron lifetime (LT) measurements were performed in vacuum after a heat treatment to remove the water from samples. X-ray diffraction method (XRD) was also applied to determine the changes in the crystallinity of zeolite. Gradual transformation of the crystalline structure to amorphous one can be observed in dependence of the implanted doses. Combination of LT and XRD provides a consistent view on structural effects induced by H+ beam in zeolite 4A.

Tuyen, L. A.; Szilágyi, E.; Kótai, E.; Lázár, K.; Bottyán, L.; Dung, T. Q.; Cuong, L. C.; Khiem, D. D.; Phuc, P. T.; Nguyen, L. L.; Hue, P. T.; Hue, N. T. N.; Tao, C. V.; Chuong, H. D.

2015-01-01

138

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

SciTech Connect

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

Conrad Ingram; Mark Mitchell

2005-03-31

139

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

SciTech Connect

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

Ogino, I.; Gates, B.C.

2009-05-22

140

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

141

Solvent-Free Syntheses of Hierarchically Porous Aluminophosphate-Based Zeolites with AEL and AFI Structures.  

PubMed

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

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

2014-12-22

142

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

NASA Astrophysics Data System (ADS)

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

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

2010-04-01

143

Electroanalytical chemistry with zeolites  

Microsoft Academic Search

In this paper we explore how solution phase molecules affect the electrochemistry of silver-cation exchanged zeolite-modified electrodes (ZMEs). Furthermore, we examine the potential utility of ZME response to quantify solution phase analytes in aqueous and non-aqueous solutions. We give several examples which show that ZMEs are useful in assessing detection efficiencies and analyte selectivities. However, flow systems are better if

C. Senaratne; J. Zhang; J. Fox; I. Burgess; M. D. Baker

1999-01-01

144

Growth and characterization of NiS and NiCoS nanoparticles in mordenite zeolite host  

Microsoft Academic Search

We report the optical and structural properties of NiS and the ternary NiCoS nanoparticles in mordenite zeolite. The samples were obtained by sulfidation of the Ni2+ and Co2+ ion-exchange zeolite in a Na2S solution at room temperature. The optical properties of the samples were studied by UV–visible spectroscopy. Their crystalline structure and morphology were studied by XRD and scanning electron

Sh. Sohrabnezhad; A. Pourahmad; M. S. Sadjadi; M. A. Zanjanchi

2008-01-01

145

Conversion of exhausted fluid cracking catalysts into zeolites by alkaline fusion  

Microsoft Academic Search

Na2CO3 fusion was used to improve the conversion of exhausted fluid cracking catalysts into NaA zeolite. Experiments were performed varying the catalyst\\/Na2CO3 mass ratios and the heating treatment. X-ray diffraction analysis was used to identify the different crystalline phases present in the starting material as well as in the products. Quantitative determination of crystalline phases was performed by Rietveld analysis.

Elena I. Basaldella; Rosa M. Torres Sánchez; Maria S. Conconi

2009-01-01

146

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

SciTech Connect

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

EL-Mekkawi, Doaa M., E-mail: doaa_egypt@yahoo.com; Selim, Mohamed M., E-mail: mmaselim@yahoo.com

2012-07-15

147

Synthesis, characterisation and thermal behaviour of lithium aluminosilicate inorganic polymers  

Microsoft Academic Search

Lithium aluminosilicate inorganic polymers were synthesised from dehydroxylated kaolin-type clay (halloysite) by the conventional\\u000a method under highly alkaline conditions with lithium hydroxide or lithium silicate solutions of two different Li2O\\/SiO2 molar ratios. Variants were also developed of a solid-state synthesis method involving the thermal reaction of dehydroxylated\\u000a halloysite with LiOH followed by hydration of the product. The molar compositions of

Sean J. O’Connor; Kenneth J. D. MacKenzie

2010-01-01

148

Gas phase catalysis by zeolites  

Microsoft Academic Search

This paper provides an overview about today’s use of zeolites and related microporous materials as catalysts within the fields of refining, petrochemistry and commodity chemicals. The content of this presentation is devoted to gas phase catalysis—with focus on acid catalysis, hydrocarbon conversion and formation, oil and natural gas upgrading as well as catalytic probe reactions for the characterisation of zeolites

Michael Stöcker

2005-01-01

149

Zeolite-modified electrodes in electroanalytical chemistry  

Microsoft Academic Search

This review reports on the analytical applications of chemically modified electrodes involving zeolites or zeolite-like materials. After a brief introduction on zeolites, the implication of these solids in electrochemistry is discussed. The interest of zeolite-modified electrodes (ZMEs) for electroanalytical purpose is pointed out, by classifying the applications into five main categories depending on the detection process. In the last decade,

A. Walcarius

1999-01-01

150

Zeolite formation from coal fly ash and its adsorption potential  

SciTech Connect

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

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

2009-10-15

151

Zeolite formation from coal fly ash and its adsorption potential.  

PubMed

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

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

2009-10-01

152

Solid-state radioluminescent zeolite-containing composition and light sources  

DOEpatents

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

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

1992-01-01

153

Alteration of biophysical activity of pulmonary surfactant by aluminosilicate nanoparticles.  

PubMed

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

Kondej, Dorota; Sosnowski, Tomasz R

2013-02-01

154

Verified Syntheses of Zeolitic Materials  

NSDL National Science Digital Library

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

155

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

PubMed

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

Sprung, Christoph; Weckhuysen, Bert M

2014-03-24

156

Oxygen and hydrogen isotope geochemistry of zeolites  

NASA Technical Reports Server (NTRS)

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

Karlsson, Haraldur R.; Clayton, Robert N.

1990-01-01

157

The Framework Topology of ZSM-18, a Novel Zeolite Containing Rings of Three (Si,Al)-O Species.  

PubMed

ZSM-18 is the first known aluminosilicate zeolite to contain rings of three (Si,Al)-O species (3-rings). Its framework topology has been determined by hypothetical model building, subsequent constrained distance and angle least-squares refinements of atomic coordinates, and x-ray powder diffraction pattern simulations. Its channel structure is characterized by a linear unidimensional 12-ring channel, with an approximate pore opening of 7.0 angstroms. In addition, the channels are lined with pockets that are capped by 7-rings with dimensions of 2.8 angstroms by 3.5 angstroms. An intraframework packing model of the organic moiety used in the synthesis suggests that a strong templating effect may be responsible for the formation of this unusual zeolite structure. PMID:17843794

Lawton, S L; Rohrbaugh, W J

1990-03-16

158

The Framework Topology of ZSM-18, a Novel Zeolite Containing Rings of Three (Si,Al)-O Species  

NASA Astrophysics Data System (ADS)

ZSM-18 is the first known aluminosilicate zeolite to contain rings of three (Si,Al)-O species (3-rings). Its framework topology has been determined by hypothetical model building, subsequent constrained distance and angle least-squares refinements of atomic coordinates, and x-ray powder diffraction pattern simulations. Its channel structure is characterized by a linear unidimensional 12-ring channel, with an approximate pore opening of 7.0 angstroms. In addition, the channels are lined with pockets that are capped by 7-rings with dimensions of 2.8 angstroms by 3.5 angstroms. An intraframework packing model of the organic moiety used in the synthesis suggests that a strong templating effect may be responsible for the formation of this unusual zeolite structure.

Lawton, Stephen L.; Rohrbaugh, Wayne J.

1990-03-01

159

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

Microsoft Academic Search

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

G Steenbruggen; G. G Hollman

1998-01-01

160

Mechanisms of zinc incorporation in aluminosilicate crystalline structures and the leaching behaviour of product phases.  

PubMed

This study quantitatively evaluates a waste-to-resource strategy of blending zinc-laden sludge and clay material for low-cost ceramic products. Using ZnO as the simulated zinc-laden sludge to sinter with kaolinite, both zinc aluminate spinel (ZnAl2O4) and willemite (Zn2SiO4) phases were formed during the sintering process. To analyse the details of zinc incorporation reactions, ?-Al2O3 and quartz were further used as precursors to observe ZnAl2O4 and Zn2SiO4 formations. By firing the ZnO mixtures and their corresponding precursors at 750-1350°C for 3?h, the efficiency of zinc transformation was determined through Rietveld refinement analyses of X-ray diffraction data. The results also show different incorporation behaviour for kaolinite and mullite precursors during the formation of ZnAl2O4 and Zn2SiO4 in the system. In addition, with a competitive formation between ZnAl2O4 and Zn2SiO4, the ZnAl2O4 spinel phase is predominant at temperatures higher than 1050°C. This study used a prolonged leaching test modified from the US Environmental Protection Agency's toxicity characteristic leaching procedure to evaluate ZnO, ZnAl2O4, and Zn2SiO4 product phases. The zinc concentrations in ZnO and Zn2SiO4 leachates were about two orders of magnitude higher than that of ZnAl2O4 leachate at the end of the experiment, indicating that ZnAl2O4 formation is the preferred stabilization mechanism for incorporating zinc in ceramic products. PMID:25399963

Tang, Yuanyuan; Shih, Kaimin

2014-12-01

161

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

PubMed Central

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

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

2012-01-01

162

Synthesis of NaP zeolite at room temperature and short crystallization time by sonochemical method.  

PubMed

NaP zeolite nano crystals were synthesized by sonochemical method at room temperature with crystallization time of 3h. For comparison, to insure the effect of sonochemical method, the hydrothermal method at conventional synthesis condition, with same initial sol composition was studied. NaP zeolites are directly formed by ultrasonic treatment without the application of autogenous pressure and also hydrothermal treatment. The effect of ultrasonic energy and irradiation time showed that with increasing sonication energy, the crystallinity of the powders decreased but phase purity remain unchanged. The synthesized powders were characterized by XRD, IR, DTA TGA, FESEM, and TEM analysis. FESEM images revealed that 50 nm zeolite crystals were formed at room temperature by using sonochemical method. However, agglomerated particles having cactus/cabbage like structure was obtained by sonochemical method followed by hydrothermal treatment. In sonochemical process, formation of cavitation and the collapsing of bubbles produced huge energy which is sufficient for crystallization of zeolite compared to that supplied by hydrothermal process for conventional synthesis. With increasing irradiation energy and time, the crystallinity of the synthesized zeolite samples increased slightly. PMID:22922038

Pal, Pameli; Das, Jugal K; Das, Nandini; Bandyopadhyay, Sibdas

2013-01-01

163

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

NASA Technical Reports Server (NTRS)

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

Ahlborg, Nadia L.; Zhu, Dongming

2013-01-01

164

Hydrothermal interactions of cement or mortar with zeolites or montmorillonites  

SciTech Connect

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

Komarneni, S.; Roy, D.M.

1983-01-01

165

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

166

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

SciTech Connect

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

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

2006-08-21

167

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

PubMed Central

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

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

2013-01-01

168

STRUCTURAL STUDIES OF BLOCK COPOLYMER AND BLOCK COPOLYMER/ALUMINOSILICATE MATERIALS  

E-print Network

/aluminosilicate material was studied via Small Angle X-ray Scattering (SAXS) and Transmission Electron Microscopy (TEMSTRUCTURAL STUDIES OF BLOCK COPOLYMER AND BLOCK COPOLYMER/ALUMINOSILICATE MATERIALS A Dissertation Gilman Ewan Stephen Toombes #12;STRUCTURAL STUDIES OF BLOCK COPOLYMER AND BLOCK COPOLYMER

Gruner, Sol M.

169

The electronic structure of a single-walled aluminosilicate nanotube  

NASA Astrophysics Data System (ADS)

The geometric structure and electronic structure of an imogolite nanotube have been studied using density functional theory (DFT). The calculation results indicate that the deformation of the material leads to structural electric charges on the tube wall. This hydrous aluminosilicate single-walled nanotube is a wide gap semiconductor with a direct band gap, Eg~3.67 eV at the ? point, which may be promising for application in optoelectronic devices. In conjunction with the DFT calculations, molecular dynamics simulations based on empirical potentials are also performed to evaluate the mechanical properties of this material.

Li, Lijuan; Xia, Yueyuan; Zhao, Mingwen; Song, Chen; Li, Jiling; Liu, Xiangdong

2008-04-01

170

The electronic structure of a single-walled aluminosilicate nanotube.  

PubMed

The geometric structure and electronic structure of an imogolite nanotube have been studied using density functional theory (DFT). The calculation results indicate that the deformation of the material leads to structural electric charges on the tube wall. This hydrous aluminosilicate single-walled nanotube is a wide gap semiconductor with a direct band gap, E(g)?3.67 eV at the ? point, which may be promising for application in optoelectronic devices. In conjunction with the DFT calculations, molecular dynamics simulations based on empirical potentials are also performed to evaluate the mechanical properties of this material. PMID:21825681

Li, Lijuan; Xia, Yueyuan; Zhao, Mingwen; Song, Chen; Li, Jiling; Liu, Xiangdong

2008-04-30

171

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

172

New nanocomposites based on layered aluminosilicate and guanidine containing polyelectrolytes  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

173

Adsorption of unsaturated hydrocarbons on zeolites: the eects of the zeolite framework on adsorption  

E-print Network

Adsorption of unsaturated hydrocarbons on zeolites: the eects of the zeolite framework-FAU) and H-ZSM-5 zeolites have been investigated by both the cluster and embedded cluster approaches with the experimental observation that the ZSM-5 is more acidic than that of FAU zeolite. The adsorption energy

Truong, Thanh N.

174

POLYMER-ZEOLITE NANOCOMPOSITE HIGH-TEMPERATURE  

E-print Network

POLYMER-ZEOLITE NANOCOMPOSITE HIGH-TEMPERATURE PROTON-EXCHANGE-MEMBRANE FOR FUEL CELLS Prepared For://www.energy.ca.gov/research/index.html. #12;Page 1 Polymer-Zeolite Nanocomposite High Temperature Proton-Exchange- Membrane for Fuel Cells EI SMALL GRANT (EISG) PROGRAM INDEPENDENT ASSESSMENT REPORT (IAR) POLYMER-ZEOLITE NANOCOMPOSITE HIGH-TEMPERATURE

175

Dynamic Reduction of FeO-Bearing, Anhydrous Aluminosilicate Melts  

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

176

Parameters influencing zeolite incorporation in PDMS membranes  

SciTech Connect

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

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

1994-11-24

177

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

SciTech Connect

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

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

2012-02-06

178

Zeolites with continuously tuneable porosity.  

PubMed

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

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

2014-11-24

179

Zeolite-dye micro lasers  

E-print Network

We present a new class of micro lasers based on nanoporous molecular sieve host-guest systems. Organic dye guest molecules of 1-Ethyl-4-(4-(p-Dimethylaminophenyl)-1,3-butadienyl)-pyridinium Perchlorat were inserted into the 0.73-nm-wide channel pores of a zeolite AlPO$_4$-5 host. The zeolitic micro crystal compounds where hydrothermally synthesized according to a particular host-guest chemical process. The dye molecules are found not only to be aligned along the host channel axis, but to be oriented as well. Single mode laser emission at 687 nm was obtained from a whispering gallery mode oscillating in a 8-$\\mu$m-diameter monolithic micro resonator, in which the field is confined by total internal reflection at the natural hexagonal boundaries inside the zeolitic microcrystals.

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

1998-01-01

180

Structural Characterization of Zeolite Beta  

NASA Astrophysics Data System (ADS)

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

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

1988-12-01

181

Fundamentals and applications of pervaporation through zeolite membranes  

Microsoft Academic Search

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

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

2004-01-01

182

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

183

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

E-print Network

A 27 Al NMR study of the structure of lanthanum and yttrium based aluminosilicate glasses and melts actinides (Pu as well as minor actinides). Yttrium and lanthanum has been chosen to simulate actinides

Paris-Sud XI, Université de

184

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

PubMed

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

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

2011-11-01

185

Evaluation of hydrophilic-hydrophobic character of zeolites by measurements of their immersional heats in water  

Microsoft Academic Search

Na-type faujasite was modified by SiCl4 treatment under dealumination-silicon-exchange reaction. Their crystallinities and lattice constants were analyzed by x-ray diffraction, and their surface areas and pore structures were measured by nitrogen adsorption at 77 K. Their hydrophobic characteristics were evaluated by measurements of water adsorption and heats of immersion into weter, and compared with those of ZSM-5 zeolites which were

T. Kawai; K. Tsutsumi

1992-01-01

186

Process wastewater treatment with hydrogen-form CST and chabazite zeolite  

Microsoft Academic Search

Ion-exchange materials have been investigated for the removal of radionuclides from near-neutral-pH wastewaters containing competing cations at concentrations greater than those of the targeted species. Natural chabazite zeolite was chosen as the baseline material for the removal of fission products, namely ⁹°Sr and ¹³⁷Cs, from wastewater and groundwater. The sorbent IONSIV{reg_sign} IE-911, a crystalline silicotitanate manufactured by UOP, was recently

S. M. DePaoli; D. T. Bostick

1998-01-01

187

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

SciTech Connect

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

Pearson, J. (California Univ., Berkeley, CA (United States). Dept. of Chemistry Lawrence Berkeley Lab., CA (United States))

1991-07-01

188

Single and Multiple Heteroatom Incorporation in MFI Zeolites  

E-print Network

for modulating acid strength and enhancing catalytic properties respectively. Three specific systems were studied: MFI zeolites with simultaneous incorporation of germanium and aluminum (i.e. Ge-Al-MFI zeolites), MFI zeolites with simultaneous incorporation...

Garcia Vargas, Nataly

2012-11-05

189

UTILITY OF ZEOLITES IN HAZARDOUS METAL REMOVAL FROM WATER  

EPA Science Inventory

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

190

Crystallinity in starch bioplastics  

Microsoft Academic Search

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

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

1996-01-01

191

An Electron Microprobe Study of Synthetic Aluminosilicate Garnets  

NASA Astrophysics Data System (ADS)

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

Fournelle, J.; Geiger, C. A.

2010-12-01

192

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

PubMed

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

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

2010-12-01

193

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

SciTech Connect

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.

Conrad Ingram; Mark Mitchell

2006-09-30

194

Surface functionalization of aluminosilicate nanotubes with organic molecules.  

PubMed

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

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

2012-01-01

195

High functional expression of osteoblasts on imogolite, aluminosilicate nanotubes.  

PubMed

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

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

2010-02-01

196

Mixed alkaline earth effect in the compressibility of aluminosilicate glasses.  

PubMed

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

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

2014-02-01

197

Aqueous dissolution of sodium aluminosilicate geopolymers derived from metakaolin  

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

198

Increased thermal conductivity monolithic zeolite structures  

DOEpatents

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

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

2008-11-25

199

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

SciTech Connect

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

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

2007-01-01

200

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

Microsoft Academic Search

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

Hae-Kwon Jeong

2004-01-01

201

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

202

Structure-Entropy Relationships in Aluminosilicate Garnets (Invited)  

NASA Astrophysics Data System (ADS)

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

Geiger, C. A.; Dachs, E.

2013-12-01

203

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

PubMed

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

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

2014-01-29

204

Imogolite: an aluminosilicate nanotube endowed with low cytotoxicity and genotoxicity.  

PubMed

High-aspect-ratio nanomaterials (HARN) (typically, single-walled carbon nanotubes (SWCNT) or multiwalled carbon nanotubes (MWCNT)) impair airway barrier function and are toxic to macrophages. Here, we assess the biological effects of nanotubes of imogolite (INT), a hydrated alumino-silicate [(OH)3Al2O3SiOH] occurring as single-walled NT, on murine macrophages and human airway epithelial cells. Cell viability was assessed with resazurin. RT-PCR was used to study the expression of Nos2 and Arg1, markers of classical or alternative macrophage activation, respectively, and nitrite concentration in the medium was determined to assess NO production. Epithelial barrier integrity was evaluated from the trans-epithelial electrical resistance (TEER). Potential genotoxicity of INT was assessed with comet and cytokinesis-block micronucleus cytome assays. Compared to MWCNT and SWCNT, INT caused much smaller effects on RAW264.7 and MH-S macrophage viability. The incubation of macrophages with INT at doses as high as 120 ?g/cm(2) for 72 h did not alter either Nos2 or Arg1 expression nor did it increase NO production, whereas IL6 was induced in RAW264.7 cells but not in MH-S cells. INT did not show any genotoxic effect in RAW264.7 and A549 cells except for a decrease in DNA integrity observed in epithelial A549 cells after treatment with the highest dose (80 ?g/cm(2)). No significant change in permeability was recorded in Calu-3 epithelial cell monolayers exposed to INT, whereas comparable doses of both SWCNT and MWCNT lowered TEER. Thus, in spite of their fibrous nature, INT appear not to be markedly toxic for in vitro models of lung-blood barrier cells. PMID:24933079

Rotoli, Bianca Maria; Guidi, Patrizia; Bonelli, Barbara; Bernardeschi, Margherita; Bianchi, Massimiliano G; Esposito, Serena; Frenzilli, Giada; Lucchesi, Paolo; Nigro, Marco; Scarcelli, Vittoria; Tomatis, Maura; Zanello, Pier Paolo; Fubini, Bice; Bussolati, Ovidio; Bergamaschi, Enrico

2014-07-21

205

UTILITY OF ZEOLITES IN ARSENIC REMOVAL FROM WATER  

EPA Science Inventory

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

206

Dual zeolite fluid cracking catalyst composition for improved gasoline octane  

Microsoft Academic Search

A fluid cracking catalyst is described useful for the production of high octane gasoline comprising a hydrothermally or chemically stabilized Y zeolite component and a stabilized Omega zeolite component having a silica to alumina ratio greater than 15 wherein the weight ratio of the Y zeolite to the stabilized Omega zeolite is 1:3 to 20: 1, said catalyst not having

Gatte

1993-01-01

207

Durability of Hydrophilic and Antimicrobial Zeolite Coatings under Water Immersion  

E-print Network

Durability of Hydrophilic and Antimicrobial Zeolite Coatings under Water Immersion Cory O-exchanged zeolite A (Ag-ZA) coatings have been shown to have excellent hydrophilicity and are highly antimicrobial Keywords: zeolite coating, zeolite A, hydrophilic, antimicrobial, gravity Introduction Condensing heat

Chen, Wilfred

208

Mechanistic principles of nanoparticle evolution to zeolite crystals  

E-print Network

ARTICLES Mechanistic principles of nanoparticle evolution to zeolite crystals TRACY M. DAVIS1 and building units of silicalite-1, an all-silica zeolite prototype for templated crystal growth. The potential to control nucleation and growth of preferentially oriented zeolite thin films11 and to tailor zeolite

Kokkoli, Efie

209

Silver supported on natural Mexican zeolite as an antibacterial material  

Microsoft Academic Search

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

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

2000-01-01

210

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

PubMed

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

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

2014-02-01

211

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

NASA Astrophysics Data System (ADS)

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.

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

1992-10-01

212

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

NASA Astrophysics Data System (ADS)

A space-charge-limited beam with current densities (J) exceeding 1 mA/cm2 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/cm2, 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.

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

2012-04-01

213

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

NASA Astrophysics Data System (ADS)

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

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

2009-07-01

214

Salt-thermal zeolitization of fly ash.  

PubMed

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

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

2001-07-01

215

Zeolitic Materials, Vol. 3, No. 1, December 2002, 20-28 20 Copyright 2002 Korean Zeolite Association  

E-print Network

Zeolitic Materials, Vol. 3, No. 1, December 2002, 20-28 20 Copyright ¨Ï 2002 Korean Zeolite activity than ZSM-5 zeolite, and also has higher catalytic stability than MCM-41- SO3H. Keywords: Periodic. / Synthesis and Alkylation of Phenol over PMO-SO3H Zeolitic Materials, Vol. 3, No. 1, December 2002 21

Kim, Ji Man

216

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

E-print Network

Zeolitic Materials, Vol. 3, No. 1, December 2002, 29-35 Copyright ¨Ï 2002 Korean Zeolite Association 29 Etherification Reaction of 2-Naphtol with Ethanol Using Dealuminated Beta Zeolite Jin Won Kim Korea *To whom correspondence should be addressed. E-mail: Yie@ajou.ac.kr ABSTRACT Zeolite H

Kim, Ji Man

217

Proton Adsorption Selectivity of Zeolites in Aqueous Media: Effect of Si/Al Ratio of Zeolites.  

PubMed

In addition to their well-known uses as catalysts, zeolites are utilized to adsorb and remove various cations from aqueous system. The adsorption of the cations is ascribed to the negative charge of zeolites derived from isomorphous substitution of Si by Al. The amount of Na+ adsorption on 4A, X, Y, Na-P1 and mordenite type zeolites were determined in aqueous media, in a two-cation (Na+ and H+) system. Although each zeolite has a constant amount of negative charge, the amount of Na+ adsorption of each zeolite decreased drastically at low pH-pNa values, where pH-pNa is equal to log{(Na+)/(H+)}. By using the plot of the amount of Na+ adsorption versus pH-pNa, an index of the H+ selectivity, which is similar to the pKa of acids, of each zeolite was estimated, and the index tended to increase with decreasing Si/Al ratio of zeolites. These indicate that zeolites with lower Si/Al and higher negative charge density have higher H+ adsorption selectivity, and in fact, such a zeolite species (4A and X) adsorbed considerable amount of H+ even at weakly alkaline pH region. The adsorption of H+ results in the decrease of cation adsorption ability, and may lead to the dissolution of zeolites in aqueous media. PMID:25493632

Munthali, Moses Wazingwa; Elsheikh, Mohammed Abdalla; Johan, Erni; Matsue, Naoto

2014-01-01

218

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

SciTech Connect

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

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

1980-09-01

219

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

PubMed

A hierarchical MFI zeolite, with typical micro/meso bimodal pore structures, was prepared by desilication method. CuO nanoparticles (NPs) were incorporated into the hierarchical MFI zeolite by impregnation method. CuO/hierarchical zeolite composites were characterized by X-ray diffraction, transmission electron microscopy and nitrogen sorption. It is shown that the CuO nanoparticles are mostly dispersed in the mesopores with remaining of the crystallinity and morphology of the host zeolite. CuO nanoparticles located in hierarchical zeolite exhibit the excellent electrocatalytic performances to oxidation of glucose in alkaline media. The electrocatalytic activity enhances with increasing the loading content of CuO from 5% to 15%. The composites were fabricated for nonenzyme glucose sensing. Under the optimal conditions, the sensor shows a wide linear range from 5×10(-7) to 1.84×10(-2)M with a low detection limit of 3.7×10(-7)M. The sensor also exhibits good repeatability, long-term stability as well as high selectivity against interfering species. PMID:25499226

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

2015-01-01

220

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

Microsoft Academic Search

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

Niken Taufiqurrahmi; Abdul Rahman Mohamed; Subhash Bhatia

221

Zeolites on Mars: Prospects for Remote Sensing  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

222

Coating crystalline nuclear waste forms to improve inertness  

SciTech Connect

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

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

1981-01-01

223

Copper-Exchanged Zeolite L Traps Oxygen  

NASA Technical Reports Server (NTRS)

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

Sharma, Pramod K.; Seshan, Panchalam K.

1991-01-01

224

Formation and crystallization in the yttrium aluminosilicate glasses containing zinc oxide  

SciTech Connect

Formation of yttrium aluminosilicate glasses containing zinc oxide from batches melted at 1550/sup 0/c was investigated. Densities, thermal expansion coefficients, and Vickers hardnesses were measured for some glasses. In a specific compositional region, crystals with a convex and pyramidal habit were observed on the glass surface.

Makishima, A.; Kubo, H.; Kotani, K.; Tsutsumi, M.; Asami, M.

1986-12-01

225

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...

226

Mechanism of interface formation in a silicon carbide fiber-reinforced magnesuium aluminosilicate  

SciTech Connect

The formation of sliding interfacial layers is a major key to the success of fiber-reinforced glass-ceramics. This paper reports the mechanism of formation of fiber-matrix interfaces during oxidizing heat treatments in a SiC fiber-reinforced magnesium aluminosilicate.

Kumar, A. [Naval Postgraduate School, Monterey, CA (United States); Knowles, K.M. [Univ. of Cambridge (United Kingdom)

1995-12-01

227

Jibamitra Ganguly Weiji Cheng Sumit Chakraborty Cation diffusion in aluminosilicate garnets: experimental determination  

E-print Network

Jibamitra Ganguly á Weiji Cheng á Sumit Chakraborty Cation diffusion in aluminosilicate garnets 1997 Abstract Diusion couples made from homogeneous gem quality natural pyrope and almandine garnets interdiusion coecient or D matrix elements for the purpose of modeling of diusion processes in natural garnets

Ganguly, Jibamitra

228

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

PubMed

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

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

2014-07-21

229

Modified 8-ring zeolites as catalysts  

SciTech Connect

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.

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

1988-06-21

230

Flexibility of the zeolite RHO framework. In situ X-ray and neutron powder structural characterization of cation-exchanged BePO and BeAsORHO analogs  

SciTech Connect

This is an extensive study of the non-aluminosilicate analogs of the zeolite RHO. This molecular sieve is of great interest commercially because of its catalytic properties. In the absence of rigid supporting structural subunits (smaller cages or channels), the aluminosilicate RHO exhibits atypical framework flexibility with large displacivere arrangements. The beryllophosphate and beryalloarsenate analogs are easily synthesized under very mild reaction conditions and therefore maybe of interest for inexpensive and rapid commercial production. However,t hey have decreased thermal stability. In an effort to increase thermal stability and explore framework flexibility, we have synthesized and characterized a series of analogs of the non-aluminosilicate RHO framework. All materials crystallize in the space group I23, ranging from a = 13.584-(2) A for Li-BePO RHO to a = 14.224(4) A for Ba-RbBeAsO RHO for hydrated phases. The extra framework cations are distributed over the double 8-ring, single 8-ring, and two single 6-ring sites. Partially and fully dehydrated phases were also studied for changes in framework stability. Predictive trends based on the type of cation exchanged into the framework were determined by {sup 9}Be and {sup 31}P MAS NMR. 50 refs., 8 figs., 6 tabs.

Nenoff, T.M. [Univ. of California, Santa Barbara, CA (United States)] [Univ. of California, Santa Barbara, CA (United States); Parise, J.B. [State Univ. of New York, Stony Brook, NY (United States)] [State Univ. of New York, Stony Brook, NY (United States); Jones, G.A.; Galya, L.G.; Corbin, D.R.; Stucky, G.D. [DuPont Co., Wilmington, DE (United States)] [DuPont Co., Wilmington, DE (United States)

1996-08-15

231

CRYSTALLINE HEXOKINASE (HETEROPHOSPHATESE)  

PubMed Central

1. Crystalline hexokinase has been isolated from baker's yeast. 2. Crystalline hexokinase is a protein of albumin type of a molecular weight of 96,000. Its isoelectric point is at about pH 4.8. 3. The method of isolation consists in separating the proteins of an aqueous extract of toluene-treated yeast by means of fractional precipitation with ammonium sulfate and with alcohol. 4. The procedure involves also the separation of several crystalline proteins, including one yellow crystalline protein, which do not possess hexokinase activity. The biological and the physicochemical properties of these proteins are still under investigation. 5. The crystallization of hexokinase proceeds at about 5°C. in the presence of ammonium sulfate and dilute phosphate buffer pH 7.0. 6. Crystalline hexokinase becomes relatively pure after 2 or 3 recrystallizations as tested by solubility, sedimentation in the ultracentrifuge, and electrophoresis. The enzymatic activity remains constant on repeated crystallization. 7. The enzymatic activity is associated with the protein nature of the material. Inactivation is accompanied by denaturation of the protein. 8. Crystalline hexokinase is relatively stable when stored in the form of crystalline filter cake. Solutions of hexokinase in dilute buffers are most stable at pH 5.0. 9. Crystalline hexokinase requires the presence of magnesium ions for its catalytic activity. PMID:19873468

Kunitz, M.; McDonald, Margaret R.

1946-01-01

232

Three Mile Island zeolite vitirification demonstration program  

SciTech Connect

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

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

1981-06-01

233

Thermodynamic modeling of natural zeolite stability  

SciTech Connect

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

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

1997-06-01

234

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

SciTech Connect

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.

Conrad Ingram; Mark Mitchell

2007-03-31

235

The zeolite deposits of Greece  

USGS Publications Warehouse

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

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

1996-01-01

236

Powder Diffraction in Zeolite Science  

NASA Astrophysics Data System (ADS)

This tutorial discusses the fundamental principles of X-ray diffraction and its applications in zeolite science. The early sections review the physics of diffraction, crystal symmetry, and reciprocal space. We discuss how the intensity of diffracted radiation is affected both by geometric effects involving detection (the Lorentz-polarization factor) and by the arrangement of atoms within the crystal (the structure factor). The differences between powder diffraction and single-crystal diffraction are then described, and differences between X-ray and neutron diffraction are also discussed. Later sections describe the effects of symmetry, lattice substitution, crystallite size, residual strain, preferred orientation, and X-ray absorption. Special emphasis is placed on the proper application of the Scherrer analysis in reporting crystalize size. The principles of structure solution from direct methods and Patterson methods are then introduced, and a description of Rietveld analysis is given. Finally the effects of stacking disorder on a powder diffraction pattern are presented.

Burton, Allen W.

237

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

SciTech Connect

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

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

2009-02-04

238

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

PubMed

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

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

2005-12-01

239

The catalytic diversity of zeolites: confinement and solvation effects within voids of molecular dimensions.  

PubMed

The ability of molecular sieves to control the access and egress of certain reactants and products and to preferentially contain certain transition states while excluding others based on size were captured as shape selectivity concepts early in the history of zeolite catalysis. The marked consequences for reactivity and selectivity, specifically in acid catalysis, have since inspired and sustained many discoveries of novel silicate frameworks and driven the engineering of hierarchical structures and void size to influence catalysis. The catalytic diversity of microporous voids is explored and extended here in the context of their solvating environments, wherein voids act as hosts and stabilize guests, whether reactive intermediates or transition states, by van der Waals forces. We use specific examples from acid catalysis, including activation of C-C and C-H bonds in alkanes, alkylation and hydrogenation of alkenes, carbonylation of dimethyl ether, and elimination and homologation reactions of alkanols and ethers, which involve transition states and adsorbed precursors of varying size and composition. Mechanistic interpretations of measured turnover rates enable us to assign precise chemical origins to kinetic and thermodynamic constants in rate equations and, in turn, to identify specific steps and intermediates that determine the free energy differences responsible for chemical reactivity and selectivity. These free energy differences reflect the stabilization of transition states and their relevant precursors via electrostatic interactions that depend on acid strength and van der Waals interactions that depend on confinement within voids. Their respective contributions to activation free energies are examined by Born-Haber thermochemical cycles by considering plausible transition states and the relevant precursors. These examples show that zeolite voids solvate transition states and precursors differently, and markedly so for guest moieties of different size and chemical composition, thus enabling voids of a given size and shape to provide the "right fit" for a given elementary step, defined as that which minimizes Gibbs free energies of activation. Tighter confinement is preferred at low temperatures because enthalpic gains prevail over concomitant entropic losses, while looser fits are favored at high temperatures because entropy gains offset losses in enthalpic stabilization. Confinement and solvation by van der Waals forces are not directly involved in the making or breaking of strong chemical bonds; yet, they confer remarkable diversity to zeolites, in spite of their structural rigidity and their common aluminosilicate composition. A single zeolite can itself contain a range of local void environments, each with distinct reactivity and selectivity; as a result, varying the distribution of protons among these locations within a given framework or modifying a given location by partial occlusion of the void space can extend the range of catalytic opportunities for zeolites. Taken together with theoretical tools that accurately describe van der Waals interactions between zeolite voids and confined guests and with synthetic protocols that place protons or space-filling moieties at specific locations, these concepts promise to broaden the significant impact and catalytic diversity already shown by microporous solids. PMID:23507832

Gounder, Rajamani; Iglesia, Enrique

2013-05-01

240

Dual zeolite fluid cracking catalyst composition for improved gasoline octane  

SciTech Connect

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

Gatte, R.R.

1993-08-17

241

Topological crystalline insulator nanostructures  

NASA Astrophysics Data System (ADS)

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

Shen, Jie; Cha, Judy J.

2014-11-01

242

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

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

243

Fly ash zeolite catalyst support for Fischer-Tropsch synthesis  

NASA Astrophysics Data System (ADS)

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

Campen, Adam

244

Zeolite content determination in kaolinic clays via thermal effects  

Microsoft Academic Search

For application in catalysis and adsorption processes, zeolites are synthesized on the surface of spray-dried kaolin microspheres. Various thermal effects are used for the rapid characterization of the zeolite type and content. From DTA measurements, the exothermic lattice break-down peak gives information on the zeolite type and the thermal stability of the sample. Measurements of the heats of immersion by

I. W. Schulz; U. Illgen; J. Scheve; K.-D. Backhaus

1988-01-01

245

Recent Developments in Zeolite-like Materials Synthesis and Characterisation  

Microsoft Academic Search

In the last few years considerable effort has been directed at the targeted synthesis of zeolites and zeolite-like microporous materi- als with predetermined physical and catalytic properties. With new computational techniques, it has become possible to design tem- plates for the synthesis of specific microporous structures with de- sired pore size and connectivities. With regard to zeolite-like mate- rials, much

1999-01-01

246

Microstructural Optimization of a Zeolite Membrane for Organic  

E-print Network

#12;Microstructural Optimization of a Zeolite Membrane for Organic Vapor Separation Zhiping Lai,1 growth method for the fabrication of high-permeance, high-separa- tion-factor zeolite (siliceous ZSM-5, such as twin overgrowths and random nucleation. Organic polycations are used as zeolite crystal shape modifiers

Kokkoli, Efie

247

Synthesis of zeolite beta in fluoride media under microwave irradiation  

E-print Network

Synthesis of zeolite beta in fluoride media under microwave irradiation Dae Sung Kim a , Jong 2003; received in revised form 28 November 2003; accepted 29 November 2003 Abstract Zeolite beta has of zeolite beta. In particular, microwave technique combined with fluoride species and seeding led to more

Kim, Ji Man

248

Zeolite membranes – state of their development and perspective  

Microsoft Academic Search

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

J Caro; M Noack; P Kölsch; R Schäfer

2000-01-01

249

MATERIALS, INTERFACES, AND ELECTROCHEMICAL PHENOMENA Hydrophilic Zeolite Coatings for Improved  

E-print Network

MATERIALS, INTERFACES, AND ELECTROCHEMICAL PHENOMENA Hydrophilic Zeolite Coatings for Improved Heat on the surface of a bare, ZSM-5 coated, and Zeolite-A coated stainless steel 304 substrate at different initial surface temperatures was experimentally studied. ZSM-5 and Zeolite-A coated SS-304 are more much more

Aguilar, Guillermo

250

Phyllosilicates and nanophase aluminosilicates at Mawrth Vallis and their geochemical implications  

NASA Astrophysics Data System (ADS)

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

Bishop, J. L.; Rampe, E.

2013-09-01

251

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

SciTech Connect

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

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

2008-04-15

252

K5.76Ga5.76Si10.24O32.3.4H2O, a gallosilicate with the zeolite gismondine topology.  

PubMed

The title compound, K-GaSi-GIS, potassium gallium silicon oxide hydrate, was synthesized hydrothermally and its crystal structure was determined from data collected on a single crystal of dimensions 10 x 10 x 8 microm at a synchrotron X-ray source. The compound, which has the aluminosilicate (AlSi) zeolite gismondine (GIS) topology, Ca(4)[Al(8)Si(8)O(32)].16H(2)O, crystallizes in the tetragonal space group I4(1)/a. A disordered distribution of the framework Si/Ga sites leads to higher symmetry of the GIS-type network compared with the usual monoclinic symmetry in AlSi-GIS. Framework Ga substitution for Al in AlSi-GIS leads to substantial distortion of the crankshaft chains, reducing the effective pore dimensions and suggesting the possibility of pore-dimension control via partial framework-cation substitution. PMID:11313552

Tripathi, A; Parise, J B; Kim, S J; Lee, Y; Uh, Y S

2001-04-01

253

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

Microsoft Academic Search

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

Jonathan Tailby; Kenneth J. D. MacKenzie

2010-01-01

254

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

Microsoft Academic Search

Twenty-seven fully loaded ¹³⁷Cs aluminosilicate pellets were fabricated in a hot cell by the vacuum hot pressing of a cesium carbonate\\/montmorillonite clay mixture at 1500°C and 570 psig. Four pellets were selected for characterization studies which included calorimetric measurements, metallography, scanning electron microscope and electron backscattering (SEM-BSE), electron microprobe, x-ray diffraction, and cesium ion leachability measurements. Each test pellet contained

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

1981-01-01

255

PERFORMANCE OF ACIDIC MCM-LIKE ALUMINOSILICATE CATALYSTS IN PYROLYSIS OF POLYPROPYLENE  

Microsoft Academic Search

Mesoporous aluminosilicate catalysts having different Al\\/Si ratios were synthesized following a hydrothermal synthesis route and using different aluminum sources, such as aluminum nitrate and aluminum isopropoxide. These mesoporous materials have high surface areas, in the range of 520–1001 m\\/g, and exhibit Type IV nitrogen adsorption isotherms. EDS and Al MAS NMR results showed that aluminum was incorporated more effectively into the

Zeynep Obali; Naime Asli Sezgi; Timur Do?u

2008-01-01

256

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

SciTech Connect

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

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

2008-02-27

257

Anti wetting additives for aluminosilicate refractories in molten aluminum contact applications  

NASA Astrophysics Data System (ADS)

Aluminosilicate based refractories are widely used in furnace installations for melting aluminum because they are inexpensive, readily available and generally exhibit the properties desired from a refractory material. However, they face severe corrosion and degradation issues due to the extremely reducing nature of molten aluminum alloys. Isothermal static cup testing is widely used as a tool to evaluate the performance of refractories against penetration by molten aluminum alloys. Various testing methods were reviewed and an upgraded static cup test was recommended. Commercially available aluminosilicate refractories were tested using this method and their results were studied in order to understand the corrosion process. Barium sulfate, which is widely used as an anti-wetting additive to improve refractory performance by limiting physical contact between molten metal and the refractory, has proved ineffective at temperatures above 1000°C. A literature review suggested that barium sulfate formed barium celsian at high temperatures and that the celsian was responsible for the non-wetting effect. Wetting angle measurements of molten AL 5083 on synthetic celsian discs revealed that barium celsian and strontium celsian were both not wetted by molten aluminum. Static cup tests were performed on aluminosilicate refractories containing barium carbonate and strontium carbonate. These additives led to the in-situ formation of celsian phases within the refractory matrix that led to improved corrosion resistance at 1300°C. Phase analysis revealed that celsian formation suppressed the formation of mullite within refractories, thereby reducing penetration.

Shukla, Devdutt Pramod

258

Sorption of 137Cs, 133Ba and 154Eu by synthesized sodium aluminosilicate (Na-AS).  

PubMed

Sodium aluminosilicate has been synthesized by solution route for use as a sorbent for various radionuclides. It was characterized by XRD, zeta potential, BET surface area, FTIR spectroscopy and site density measurement. Sorption studies of (137)Cs, (133)Ba and (154)Eu on synthesized sodium aluminosilicate have been carried out at varying pH (3-10). Sorption of all the metal ions was found to increase with pH of suspension with the saturation value increasing with the oxidation state of metal ion. Effect of Aldrich humic acid (2mg/l) on sorption was also investigated. In case of (137)Cs, the sorption was not affected by the presence of humic acid, while in case of (133)Ba and (154)Eu, sorption was enhanced at lower pH and decreased at higher pH in presence of HA. A series of experiments were carried out for (154)Eu sorption on sodium aluminosilicate at various conditions. Sorption of europium was analyzed by different sorption isotherms, viz., Freundlich and D-R isotherm. Thermodynamic data reveal sorption phenomena as endothermic and spontaneous. Studies were further extended to find out effect of diverse ions (Ca(2+) and CO(3)(2-)) on sorption of europium. PMID:20236759

Singh, B K; Tomar, Radha; Kumar, Sumit; Jain, Aishwarya; Tomar, B S; Manchanda, V K

2010-06-15

259

Zeolite-templated Pt/C electrocatalysts  

SciTech Connect

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

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

2008-06-16

260

Adsorption of nitrosamines by mesoporous zeolite.  

PubMed

On the basis of a study of the adsorption of zeolite and mesoporous silica, we attempted to create a hierarchical structure in the new nitrosamines trapper. Thus, mesoporous HZSM-5 zeolite was fabricated through impregnating a structure-directing agent into the as-synthesized MCM-41 followed by dry-gel conversion to transform amorphous silica to zeolite crystal. The texture of mesoporous ZSM-5 was tailored by adjusting the Si/Al ratio in the MCM-41 source and the thermal treatment time. The resulting samples were characterized by N(2) adsorption to evaluate their textural properties. One volatile nitrosamine, N-nitrosopyrrolidine (NPYR), was used as probe molecule in instantaneous adsorption to survey the function of the resulting composites. Adsorptions of N'-nitrosonornicotine (NNN) in dichloromethane solution and tobacco-specific nitrosamines (TSNA) in tobacco-extract solution were also utilized for the same purpose. As expected, mesoporous zeolite exhibits a good adsorption capacity in laboratory tests, superior to either microporous zeolite or mesoporous silica, providing a valuable candidate for controlling nitrosamines in the environment. PMID:20621826

Lin, Wei Gang; Wei, Feng; Gu, Fang Na; Dong, Xin; Gao, Ling; Zhuang, Ting Ting; Yue, Ming Bo; Zhu, Jian Hua

2010-08-15

261

Italian zeolitized rocks of technological interest  

NASA Astrophysics Data System (ADS)

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

de'Gennaro, M.; Langella, A.

1996-09-01

262

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

PubMed

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

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

2000-09-01

263

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

SciTech Connect

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

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

2009-06-04

264

Hydrogen Purification Using Natural Zeolite Membranes  

NASA Technical Reports Server (NTRS)

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

DelValle, William

2003-01-01

265

The human crystallin gene families.  

PubMed

Crystallins are the abundant, long-lived proteins of the eye lens. The major human crystallins belong to two different superfamilies: the small heat-shock proteins (?-crystallins) and the ??-crystallins. During evolution, other proteins have sometimes been recruited as crystallins to modify the properties of the lens. In the developing human lens, the enzyme betaine-homocysteine methyltransferase serves such a role. Evolutionary modification has also resulted in loss of expression of some human crystallin genes or of specific splice forms. Crystallin organization is essential for lens transparency and mutations; even minor changes to surface residues can cause cataract and loss of vision. PMID:23199295

Wistow, Graeme

2012-01-01

266

Studies of anions sorption on natural zeolites.  

PubMed

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

Barczyk, K; Mozgawa, W; Król, M

2014-12-10

267

Crystal engineering of zeolites with graphene  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

268

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

PubMed

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

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

2012-08-15

269

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

SciTech Connect

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

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

2011-11-15

270

Synthesis of Dihydropyrimidinones Using Large Pore Zeolites  

Microsoft Academic Search

\\u000a Abstract  A series of dihydropyrimidin-2(1H)-one (DHPM) belongs to one of the important class of therapeutic and pharmacological active compound, were synthesized through\\u000a the multicomponent reactions (MCRs) of aldehydes, ethyl acetoacetate and urea, followed by the heterogeneous catalyzed Biginelli\\u000a reaction. In the present endeavour, medium (ZSM-5) and large pore zeolites (Y, BEA and MOR) as well as dealuminated zeolites\\u000a BEA, were studied

Sunil R. Mistry; Rikesh S. Joshi; Suban K. Sahoo; Kalpana C. Maheria

271

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

SciTech Connect

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

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

2010-12-15

272

High permeate flux of PVA/PSf thin film composite nanofiltration membrane with aluminosilicate single-walled nanotubes.  

PubMed

A new type of thin film nanocomposite (TFN) membranes for nanofiltration was successfully prepared by incorporating aluminosilicate single-walled nanotubes (SWNTs) within the poly(vinyl alcohol) (PVA) matrix. The nanocomposite PVA film was composed of well dispersed synthesized aluminosilicate SWNT with up to 20% volume fraction cast on a polysulfone support. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) revealed that the TFN membranes have characteristic bands at 920-1010 cm(-1) corresponding to Si-OH and Si-O-Al stretching vibration of the aluminosilicate SWNT. This insinuated the successful incorporation of aluminosilicate SWNT into the polymer matrix, which was further confirmed and quantified by X-ray photoelectron spectroscopy (XPS). The PVA layers, in the range of 0.99-1.36 ?m, are free from large defects or cracks as observed in the scanning electron microscopy (SEM) images. The membrane surface hydrophilicity increased as the membrane roughness decreased and as the contact angles decreased from 64.2° to 59.4-50.5°. The increase in water flux is due to the presence of hydrophilic nanotubes. With the incorporation of the aluminosilicate single-walled nanotubes, higher permeate water flux was achieved, while sustaining high rejection of divalent ions (97%) and monovalent ions (59%). PMID:22918049

Baroña, Garry Nathaniel B; Choi, Mijin; Jung, Bumsuk

2012-11-15

273

A comparative evaluation of IONSIV{reg_sign} IE911 and chabazite zeolite for the removal of radiostrontium and cesium from wastewater  

Microsoft Academic Search

Natural chabazite zeolite was selected as the baseline treatment technology for the removal of fission products, namely ⁹°Sr and ¹³⁷Cs, from near-neutral-pH process wastewater and groundwater. The sorbent IONSIV{reg_sign} IE-911, a crystalline silicotitanate manufactured by UOP, was recently tested in this capacity and found to compare extremely well against the baseline material. This paper presents and compares the results of

D. T. Bostick; S. M. DePaoli; B. Guo

1998-01-01

274

In situ evolution of Ni environment in magnesium aluminosilicate glasses and glass-ceramics-Influence of ZrO2 and TiO2 nucleating agents  

NASA Astrophysics Data System (ADS)

The evolution of Ni2+ environment has been systematically investigated using optical and in situ X-ray absorption spectroscopy (XAS) to determine the influence of nucleating agents (TiO2 and/or ZrO2) during the formation of spinel in magnesium aluminosilicate glass-ceramics. The results were complemented by in situ X-ray diffraction data. According to XAS and optical spectroscopy, the nature of nucleating agents does not modify significantly the Ni environment in initial glasses. However, it has a relatively strong influence in the observed crystallization sequence. Ni2+ ions do not enter the Zr-containing crystalline phase of ZrO2 or ZrTiO4 but a Ni2+ coordination change from the fivefold coordinated sites, with a small amount of tetrahedral sites in parent glasses, to [6]Ni2+ and [4]Ni2+ sites in spinel (in glasses nucleated by ZrO2 and/or TiO2) or in ?-quartz solid solutions (in glasses nucleated by ZrO2) has been found.

Dugué, A.; Dymshits, O.; Cormier, L.; Cochain, B.; Lelong, G.; Zhilin, A.; Belin, S.

2015-03-01

275

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

NASA Technical Reports Server (NTRS)

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

Bansal, Narottam P.

1996-01-01

276

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

PubMed

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

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

2014-01-01

277

Silver clusters and chemistry in zeolites  

SciTech Connect

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

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

1994-06-01

278

Multicomponent liquid ion exchange with chabazite zeolites  

SciTech Connect

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

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

1993-10-01

279

Dispersion enhanced metal/zeolite catalysts  

DOEpatents

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

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

1987-01-01

280

Dispersion enhanced metal/zeolite catalysts  

DOEpatents

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

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

1987-03-31

281

Reactions of cyclopropane over zeolite catalysts  

SciTech Connect

The reaction of cyclopropane on NaY, CaNaY, and NaHY zeolites yielded isobutane, 2-methylbutene, propane, isobutene, 2-methylbutane, 2-methylpentane, and heptanes among the minor products, probably as a result of complex oligomerization, isomerization, and cracking processes of a propylene intermediate.

Kiricsi, I.; Hannus, I.; Varca, K.; Fejes, P.

1980-06-01

282

Zeolite 5A Catalyzed Etherification of Diphenylmethanol  

ERIC Educational Resources Information Center

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

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

2009-01-01

283

Conversion of Ethanol to Hydrocarbons on Hierarchical HZSM-5 Zeolites  

SciTech Connect

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.

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

2014-12-15

284

UTILITY OF ZEOLITES IN REMOVAL OF INORGANIC AND ORGANIC WATER POLLUTANTS  

EPA Science Inventory

Zeolites are well known for their ion exchange, adsorption and acid catalysis properties. Different inorganic and organic pollutants have been removed from water at room temperature using various zeolites. Synthetic zeolite Faujasite Y has been used to remove inorganic pollutants...

285

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

NASA Astrophysics Data System (ADS)

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.

Tossell, J. A.

1995-04-01

286

Nitrogen in crystalline Si  

Microsoft Academic Search

Use of N doping, N gas ambients and N implantation in Si processing has stimulated study of the incorporation and behaviour of N in Si. Studies of N-implanted Si and comparisons with melt-doped Si have shown that N pairing is the dominant mode for bonding of N into crystalline Si for a wide range of processing conditions. Studies have also

1985-01-01

287

LTN-type zeolite framework as an interpenetrating net of KFI- and SOD-type parts homeomorphic to cuprite, Cu2O.  

PubMed

The complex LTN-type zeolite framework is described as consisting of two interpenetrating parts in order to understand the connectivities of their underlying nets. Both parts are homeomorphic to diamond-type tetrahedral frameworks, arranged in principle in the same manner as the two interpenetrating frameworks in cuprite, Cu(2)O. However, in cuprite the two frameworks are identical, while in the LTN-type framework one is made up of two kinds of truncated octahedra (toc units) and can be described as one half of the sodalite-type framework (SOD). The other consists of large cages, so-called truncated cubo-octahedra (grc units) connected by hexagonal prisms (double six-rings) and corresponds to one half of the KFI-type framework. Neither of the sub-frameworks has so far been observed in any other zeolite topology. The two sub-frameworks of SOD and KFI types in the interpenetrating LTN-type framework are models for very open interrupted frameworks, which possibly could be synthesized separately in a pure form. Their framework density would be 7.6 T atoms per 1000 A(3) if they could be prepared as aluminosilicates. PMID:17374932

Baur, Werner H; Fischer, Reinhard X

2007-04-01

288

CO2 SEPARATIONS USING ZEOLITE MEMBRANES  

SciTech Connect

Zeolite and other inorganic molecular sieve membranes have shown potential for separations based on molecular size and shape because of their small pore sized, typically less than 1 nm, and their narrow pore size distribution. The high thermal and chemical stability of these inorganic crystals make them ideal materials for use in high temperature applications such as catalytic membrane reactors. Most of the progress with zeolite membranes has been with MFI zeolites prepared on porous disks and tubes. The MFI zeolite is a medium pore size structure having nearly circular pores with diameters between .53 and .56 nm. Separation experiments through MFI membranes indicate that competitive adsorption separates light gas mixtures. Light gas selectivities are typically small, however, owing to small differences in adsorption strengths and their small sizes relative to the MFI pore opening. Furthermore, competitive adsorption does not work well at high temperature where zeolite membranes are stable and have potential application. Separation by differences in size has a greater potential to work at high temperature than competitive adsorption, but pores smaller than those in MFI zeolites are required. Therefore, some studies focused on the synthesis of a small, 8-membered-pore structures such as zeolite A (0.41-nm pore diameter) and SAPO-34, a chabazite (about .4-nm pore diameter with about 1.4 nm cages) analog. The small pore size of the zeolite A and SAPO-34 structures made the separation of smaller molecules by differences in size possible. Zeolite MFI and SAPO-34 membranes were prepared on the inside surface of porous alumina tubes by hydrothermal synthesis, and single gas and binary mixture permeances were measured to characterize the membrane's performance. A mathematical diffusion model was developed to determine the relative quantities of zeolite and non-zeolite pores in different membranes by modeling the permeation date of CO{sub 2}. This model expresses the total flux through the membrane as the sum of surface diffusion through zeolite pores and viscous flow and Knudsen diffusion through non-zeolite pores. As predicted by the model, the permeance of CO{sub 2} decrease with increasing pressure at constant pressure drop for membranes with few non-zeolite pores, but the permeance increased through viscous flow pores and was constant through pores allowing Knudsen diffusion. Membranes having more non-zeolite pores had lower CO{sub 2}/CH{sub 4} selectivities. The SAPO-34 membranes were characterized for light gas separation applications, and the separation mechanisms were identified. Single gas permeances of CO{sub 2}, N{sub 2}, and CH{sub 4} decreased with increasing kinetic diameter. For the best membrane at 300K, the He and H{sub 2} permeances were less than that of CO{sub 2}, because He, H{sub 2} and CO{sub 2} were small compared to the SAPO-34 pore, and differences in the heat of adsorption determined the permeance order. The small component permeated the fastest in CO{sub 2}/CH{sub 4}, CO{sub 2}/N{sub 2}, N{sub 2}/CH{sub 4}, H{sub 2}/CH{sub 4}, and H{sub 2}/N{sub 2} mixtures between 300 and 470 K. For H{sub 2}/CO{sub 2} mixtures, which were separated by competitive adsorption at room temperature, the larger component permeated faster below 400K. The room temperature CO{sub 2}/CH{sub 4} selectivity was 36 and decreased with temperature. The H{sub 2}/CH{sub 4} mixture selectivity was 8 and constant with temperature up to 480 K. Calcination, slow temperature cycles, and exposure to water vapor had no permanent effect on membrane performance, but temperature changes of approximately 30 K/min decreased the membrane's effectiveness. The effects of humidity on gas permeation were studied with SAPO-34 membranes of different qualities. Membranes with high CO{sub 2}/CH{sub 4} selectivities (greater than 20) were stable in water vapor under controlled conditions, but degradation was seen for some membranes. The degradation opened non-SAPO-34 pores that were larger than SAPO-34 pores as shown by the IC{sub 4}H{sub 10} permeance, C

Richard D. Noble; John L. Falconer

2001-06-30

289

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

Microsoft Academic Search

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

Thierry Loiseau; Gérard Férey

2007-01-01

290

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

PubMed

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

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

2010-09-27

291

Facile Fabrication of Uniform Polyaniline Nanotubes with Tubular Aluminosilicates as Templates  

PubMed Central

The uniform polyaniline (PANI) nanotubes, with inner diameter, outer diameter, and tubular thickness of 40, 60, and 10 nm, respectively, were prepared successfully by using natural tubular aluminosilicates as templates. The halloysite nanotubes were coated with PANI via the in situ chemical oxidation polymerization. Then the templates were etched with HCl/HF solution. The PANI nanotubes were characterized using FTIR, X-ray diffraction, and transmission electron microscopy. The conductivity of the PANI nanotubes was found to be 1.752 × 10?5(?·cm)?1.

2008-01-01

292

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

SciTech Connect

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

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

2011-07-21

293

Physical chemical studies of dispersed aluminosilicate wastes for obtaining the burned building materials  

NASA Astrophysics Data System (ADS)

This paper presents results of the studies that determined that grinding can be one of the ways to modify aluminosilicate wastes. The optimal grinding modes were defined in laboratory conditions. Physical and chemical studies of modified ashes were carried out by means of X-ray phase analysis, differential thermal analysis and microscopy. The results have shown that modified ashes of thermal power stations when being applied in production of ceramic brick influence positively the processing properties of raw materials and the ready products.

Iuriev, I. Y.; Skripnikova, N. K.; Volokitin, G. G.; Volokitin, O. G.; Lutsenko, A. V.; Kosmachev, P. V.

2015-01-01

294

First Principles Simulations of Hydrocarbon Conversion Processes in Functionalized Zeolitic Materials  

NASA Astrophysics Data System (ADS)

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

Mazar, Mark Nickolaus

295

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

PubMed

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

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

2004-03-01

296

Seeding of Porous Alumina Substrate with MFI Zeolite Nanocrystals using Spin-coating Technique  

E-print Network

Zeolite membranes offer a great potential for applications in many challenging separation processes. Controlled thickness of zeolite membrane allows high flux and excellent selectivity commercially available; producing ...

Baroud, T.

297

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

PubMed

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

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

2013-01-01

298

Preparation of Robust, Thin Zeolite Membrane Sheet for Molecular Separation  

SciTech Connect

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

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

2011-10-19

299

Advanced zeolites used in FCC catalysts boost motor octane number  

SciTech Connect

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.

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

1988-10-31

300

Charge-transfer state excitation as the main mechanism of the photodarkening process in ytterbium-doped aluminosilicate fibres  

NASA Astrophysics Data System (ADS)

We have studied photodarkening in ytterbium-doped fibre preforms with an aluminosilicate glass core. Analysis of their absorption and luminescence spectra indicates the formation of stable Yb2+ ions in the glass network under IR laser pumping at a wavelength ? = 915 nm and under UV irradiation with an excimer laser (? = 193 nm). We have performed comparative studies of the luminescence spectra of the preforms and crystals under excitation at a wavelength of 193 nm. The mechanism behind the formation of Yb2+ ions and aluminium – oxygen hole centres (Al-OHCs), common to ytterbium-doped YAG crystals and aluminosilicate glass, has been identified: photoinduced Yb3+ charge-transfer state excitation.

Bobkov, K. K.; Rybaltovsky, A. A.; Vel'miskin, V. V.; Likhachev, M. E.; Bubnov, M. M.; Dianov, E. M.; Umnikov, A. A.; Gur'yanov, A. N.; Vechkanov, N. N.; Shestakova, I. A.

2014-12-01

301

Chemical Interactions in Multimetal/Zeolite Catalysts  

SciTech Connect

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

Sachtler, Wolfgang M. H.

2004-04-16

302

Liquid crystalline composites containing phyllosilicates  

DOEpatents

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

Chaiko; David J. (Naperville, IL)

2007-05-08

303

Transesterification of soybean oil with zeolite and metal catalysts  

Microsoft Academic Search

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

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

2004-01-01

304

Large zeolites - Why and how to grow in space  

NASA Technical Reports Server (NTRS)

The growth of zeolite crystals which are considered to be the most valuable catalytic and adsorbent materials of the chemical processing industry are discussed. It is proposed to use triethanolamine as a nucleation control agent to control the time release of Al in a zeolite A solution and to increase the average and maximum crystal size by 25-50 times. Large zeolites could be utilized to make membranes for reactors/separators which will substantially increase their efficiency.

Sacco, Albert, Jr.

1991-01-01

305

Crystalline color superconductors  

E-print Network

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

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

2014-04-12

306

Method for the recovery of silver from silver zeolite  

DOEpatents

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

Reimann, George A. (Idaho Falls, ID)

1986-01-01

307

Zeolites are effective ROS-scavengers in vitro.  

PubMed

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

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

2011-07-01

308

Method for the recovery of silver from silver zeolite  

DOEpatents

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

Reimann, G.A.

1985-03-05

309

Zeolite Crystal Growth in Microgravity and on Earth  

NASA Technical Reports Server (NTRS)

The Center for Advanced Microgravity Materials Processing (CAMMP), a NASA-sponsored Research Partnership Center, is working to improve zeolite materials for storing hydrogen fuel. CAMMP is also applying zeolites to detergents, optical cables, gas and vapor detection for environmental monitoring and control, and chemical production techniques that significantly reduce by-products that are hazardous to the environment. Shown here are zeolite crystals (top) grown in a ground control experiment and grown in microgravity on the USML-2 mission (bottom). Zeolite experiments have also been conducted aboard the International Space Station.

2003-01-01

310

Crystalline titanate catalyst supports  

DOEpatents

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

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

1993-01-05

311

Crystalline titanate catalyst supports  

DOEpatents

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

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

1993-01-01

312

Liquid crystalline dendrimers.  

PubMed

In recent years, there has been an increasing interest in the field of liquid crystalline dendrimers. Such a fast development is, among other things, driven by the multiple possibilities offered by combining the mesomorphic properties of single mesogenic subunits with the supermolecular and versatile architectures of dendrimers to yield a new class of highly functional materials. The induction and the control of the mesomorphic properties (phase type and stability) in dendrimers can be achieved by a dedicated molecular design which depends on the chemical nature and structure of both the functional groups and the dendritic matrix. In particular, the intrinsic connectivity of the dendrimer such as the multivalency of the focal core and the multiplicity of the branches, both controlling the geometrical rate of growth, or the dendritic generation, plays a crucial role and influences at various stages the subtle relationships between the supermolecular structure and the mesophase structure and stability. In this critical review article, an account of the various types of dendritic systems that form liquid-crystalline mesophases along with a description of the self-organization of representative case-study supermolecules into liquid crystalline mesophases will be discussed. Some basics of thermotropic liquid crystals and dendrimers will be given in the introduction. Then, in the following sections, selected examples including side-chain, main-chain, fullerodendrimers, shape-persistent dendrimers, supramolecular dendromesogens and metallodendrimers, as representative families of LC dendrimers, will be described. In the conclusion some further developments will be highlighted. This review will not cover liquid crystalline hyperbranched and dendronized polymers that might be considered as being somehow less structurally "perfect". PMID:17660881

Donnio, Bertrand; Buathong, Saïwan; Bury, Izabela; Guillon, Daniel

2007-09-01

313

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

PubMed

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

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

2005-03-29

314

Cellular morphology of organic-inorganic hybrid foams based on alkali alumino-silicate matrix  

SciTech Connect

Organic-inorganic hybrid foams based on an alkali alumino-silicate matrix were prepared by using different foaming methods. Initially, the synthesis of an inorganic matrix by using aluminosilicate particles, activated through a sodium silicate solution, was performed at room temperature. Subsequently the viscous paste was foamed by using three different methods. In the first method, gaseous hydrogen produced by the oxidization of Si powder in an alkaline media, was used as blowing agent to generate gas bubbles in the paste. In the second method, the porous structure was generated by mixing the paste with a “meringue” type of foam previously prepared by whipping, under vigorous stirring, a water solution containing vegetal proteins as surfactants. In the third method, a combination of these two methods was employed. The foamed systems were consolidated for 24 hours at 40°C and then characterized by FTIR, X-Ray diffraction, scanning electron microscopy (SEM) and compression tests. Low density foams (?500 Kg/m{sup 3}) with good cellular structure and mechanical properties were obtained by combining the “meringue” approach with the use of the chemical blowing agent based on Si.

Verdolotti, Letizia; Capasso, Ilaria; Lavorgna, Marino [Institute of Composite and Biomedical Materials, National Research Council, Naples (Italy); Liguori, Barbara; Caputo, Domenico [Department of Chemical, Materials and Industrial Engineering, University of Naples Federico II, Naples (Italy); Iannace, Salvatore [Institute of Composite and Biomedical Materials, National Research Council, Naples, Italy and IMAST SCRAL, Piazza Bovio 22 Napoli 80133 (Italy)

2014-05-15

315

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

PubMed

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

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

2014-06-01

316

Water solubility in calcium aluminosilicate glasses investigated by first principles techniques  

SciTech Connect

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

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

2010-12-15

317

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

NASA Astrophysics Data System (ADS)

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

Yuan, Chen; Jones, Sam; Blackburn, Stuart

2012-12-01

318

Cellular morphology of organic-inorganic hybrid foams based on alkali alumino-silicate matrix  

NASA Astrophysics Data System (ADS)

Organic-inorganic hybrid foams based on an alkali alumino-silicate matrix were prepared by using different foaming methods. Initially, the synthesis of an inorganic matrix by using aluminosilicate particles, activated through a sodium silicate solution, was performed at room temperature. Subsequently the viscous paste was foamed by using three different methods. In the first method, gaseous hydrogen produced by the oxidization of Si powder in an alkaline media, was used as blowing agent to generate gas bubbles in the paste. In the second method, the porous structure was generated by mixing the paste with a "meringue" type of foam previously prepared by whipping, under vigorous stirring, a water solution containing vegetal proteins as surfactants. In the third method, a combination of these two methods was employed. The foamed systems were consolidated for 24 hours at 40°C and then characterized by FTIR, X-Ray diffraction, scanning electron microscopy (SEM) and compression tests. Low density foams (˜500 Kg/m3) with good cellular structure and mechanical properties were obtained by combining the "meringue" approach with the use of the chemical blowing agent based on Si.

Verdolotti, Letizia; Liguori, Barbara; Capasso, Ilaria; Caputo, Domenico; Lavorgna, Marino; Iannace, Salvatore

2014-05-01

319

Raman spectra of zeolites exchanged with uranyl(VI) cations—II. Zeolite X  

NASA Astrophysics Data System (ADS)

The formation of hydrolysed uranyl(VI) species in UO 2X zeolites prepared by various methods has been investigated by Raman spectroscopy. Ion-exchange in aqueous (pH>3) and non-aqueous (anhydrous methanol and uranyl nitrate melts) media resulted in the formation of hydroxy-bridged complexes such as [(UO 2) 3(OH) 4] 2+, [(UO 2) 3(OH) 5] +, and [(UO 2) 4(OH) 7] +. Ion-exchange in more acidic media (initial pH < 3) was accompanied by the formation of a disordered phase incorporating UO 3, following extensive collapse of the zeolite framework structure. Cation speciation in the UO 2X system is compared to that in UO 2Y zeolites.

Bartlett, John R.; Cooney, Ralph P.

1989-01-01

320

Characterisation and evaluation of hypothetical zeolite frameworks  

Microsoft Academic Search

A series of hypothetical zeolites, derived from the results of tiling theory, has been evaluated using computational chemistry techniques. Simulated heats of formation (i.e. the lattice energy with respect to ?-quartz or ?-berlinite for silica polymorphs and AlPO4 polymorphs, respectively) are used as an initial criterion for the chemical “feasibility” of these structures. This data is further correlated with various

2004-01-01

321

Thermionic emission of alkali ions from zeolites  

Microsoft Academic Search

The thermionic emission of positive alkali ions from zeolites has been investigated in the high-voltage pulsed regime. Current densities of up to 1 A cm-2 have been obtained using 2-mus-long 30-kV pulses. This is about two orders of magnitude larger than currents obtained in the low-voltage dc regime. There are two major reasons for this difference. First, the currents have

A. N. Pargellis; M. Seidl

1978-01-01

322

Sorption properties of EU-1 zeolites  

SciTech Connect

Various features of the sorption of benzene, n-hexane, and cyclohexane, H{sub 2}O, n-butylamine on the protonic forms of EU-1 zeolites of varying Si/Al ratio (SAR = 57.5-262.5) are reported. Equilibrium sorption uptake at P/P{sub 0} = 0.8 and 298 K for benzene (8.50 {plus minus} 0.50 wt %), n-hexane (8.25 {plus minus} 0.20 wt %), and cyclohexane (1.55 {plus minus} 0.25 wt %) was found to be unaffected by varying Si/Al ratio. Equilibrium uptake for water was found to decrease (5.89-3.95%) with the increase in Si/Al ratio, indicating enhanced hydrophobic character of the zeolites on increasing Si/Al ratio. The BET surface area was also found to decrease from 385 to 290 m{sup 2}/g with increasing Si/Al ratio. Sorption isotherms for n-butylamine (n-BA) in the temperature range 298-423 K were found to be of Langmuir type. The number of n-BA molecules sorbed per unit cell of EU-1 zeolites decreases with the increase in Si/Al ratio. n-BA sorption data was satisfactorily represented by Dubinin, BET, and Langmuir isotherm equations.

Rao, G.N.; Joshi, P.N.; Kotasthane, A.N.; Shiralkar, V.P. (National Chemical Lab., Pune (India))

1990-11-15

323

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

E-print Network

-resolution solid-state NMR Eric Robert1, , a , Alan Whittington2, , a, , b , Franck Fayona , Michel Pichavantc-resolution solid-state NMR techniques have been applied to hydrous silicate and aluminosilicate glasses: simple acquisition, cross-polarization (CP-MAS), heteronuclear correlation (HETCOR), dipolar dephasing, spin counting

Boyer, Edmond

324

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

DOEpatents

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

Pence, Dallas T. (Idaho Falls, ID); Thomas, Thomas R. (Idaho Falls, ID)

1980-01-01

325

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

SciTech Connect

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.

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

2007-01-01

326

Crystal engineering of zeolites with graphene Paul Gebhardt,a  

E-print Network

of controlling the zeolite morphology and thereby also further demonstrate the potential of graphene in hybrid Specically, the hybridization of titanium-silicalite (TS-1) with 5­ 10 wt% of graphene (produced via arcCrystal engineering of zeolites with graphene Paul Gebhardt,a Sebastian W. Pattinson,b Zhibin Ren

Elliott, James

327

Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen  

DOEpatents

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

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

1999-06-22

328

Synthetic zeolites as amendments for sewage sludge-based compost.  

PubMed

The effects of incorporating a synthetic zeolite (Zeolite P) in a range of concentrations (0.1-1.0 w:w) into an experimental horticultural compost, derived from sewage sludge, have been investigated. The impact of zeolite treatment on time-related changes of the labile zinc, copper, iron and manganese pools within the compost was compared to lime incorporation (5% w:w) and to a proprietary unamended peat-based compost. Addition of 0.5% and 1.0% zeolite significantly reduced labile zinc over a 90 day period. The highest zeolite treatment was more effective than liming; 0.5% zeolite was as effective as lime. Plant growth trials measuring transfer of metals to ryegrass (Lolium perenne L. cv Elka) in successive harvests demonstrated that both 1.0% zeolite and 5% lime treatment caused significant reduction in total metal transfer from soil-plant over a 116 day growth period. It is concluded that the use of synthetic zeolite as an amendment for compost of this type significantly reduces potential for soil metal mobility and soil-plant transfer. PMID:10819210

Nissen, L R; Lepp, N W; Edwards, R

2000-07-01

329

NO2 disproportionation for the IR characterisation of basic zeolites.  

PubMed

NO2 disproportionation on alkaline zeolites is used to generate nitrosonium (NO+) and nitrate ions on the surface, and the infrared vibrations observed are very sensitive to the cation chemical hardness and to the basicity of zeolitic oxygen atoms. PMID:15719112

Marie, Olivier; Malicki, Nicolas; Pommier, Catherine; Massiani, Pascale; Vos, Ann; Schoonheydt, Robert; Geerlings, Paul; Henriques, Carlos; Thibault-Starzyk, Fréderic

2005-02-28

330

Zeolite films prepared via the Langmuir–Blodgett technique  

Microsoft Academic Search

Micrometer sized zeolite particles were found to form relatively stable particle monolayers at the air–water interface when spread from a chloroform dispersion. For these layers compression isotherms were recorded. The presence of polyelectrolytes in the aqueous subphase was found to have a significant influence on the compression behaviour of the films and on the degree of orientation of the zeolite

K Morawetz; J Reiche; H Kamusewitz; H Kosmella; R Ries; M Noack; L Brehmer

2002-01-01

331

CATION CONTROLLED SINGLET OXYGEN MEDIATED OXIDATION OF OLEFINS WITHIN ZEOLITES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Oxidation of trialkyl olefins has been performed within zeolites employing thionin as the singlet oxygen sensitizer. Unusual selectivity in favor of secondary hydroperoxides is observed within zeolites. In light of the fact that in solution such a selectivity is never observed the selectivity report...

332

Zeolites in the Pine Ridge Indian Reservation, South Dakota  

USGS Publications Warehouse

Zeolites of possible commercial value occur in the Brule Formation of Oligocene age and the Sharps Formation (Harksen, 1961) of Miocene age which crop out in a wide area in the northern part of the Pine Ridge Indian Reservation. The thickness of the zeolite-bearing Interval and the extent of areas within the Interval which contain significant amounts of zeolites are far greater than was expected prior to this investigation. The shape of the zeolite-bearing Interval is tabular and the dimensions of Its exposure are roughly 10 ml x 200 mi x 150 ft (16 km x 160 km x 45 m) thick. Within the study area, there are tracts in which the zeolite resource potential is significant (see pl. 2). This report is intended to inform the Oglala Sioux Tribe of some of the most promising zeolite occurrences. Initial steps can then be taken by the Tribe toward possible development of the resources, should they wish to do so. The data contained herein identify areas of high zeolite potential, but are not adequate to establish economic value for the deposits. If development is recommended by the tribal government, we suggest that the tribal government contact companies involved in research and production of natural zeolites and provide them with the data in this report.

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

1982-01-01

333

Synthesis of zeolites from coal fly ash: an overview  

Microsoft Academic Search

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

X Querol; N Moreno; J. C Umaña; A Alastuey; E Hernández; A López-Soler; F Plana

2002-01-01

334

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 ...

335

Crewmember working on the mid deck Zeolite Crystal Growth experiment.  

NASA Technical Reports Server (NTRS)

View showing Payload Specialist Bonnie Dunbar, in the mid deck, conducting the Zeolite Crystal Growth (ZCG) Experiment in the mid deck stowage locker work area. View shows assembly of zeolite sample in the metal autoclave cylinders prior to insertion into the furnace.

1992-01-01

336

Transport properties of alkanes through ceramic thin zeolite MFI membranes  

Microsoft Academic Search

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

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

1996-01-01

337

Selective thermal oxidation of hydrocarbons in zeolites by oxygen  

DOEpatents

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

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

2000-01-01

338

Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen  

DOEpatents

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

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

1999-01-01

339

Selective thermal and photooxidation of hydrocarbons in zeolites by oxygen  

DOEpatents

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

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

2001-01-01

340

A zeolite ion exchange membrane for redox flow batteries.  

PubMed

The zeolite-T membrane was discovered to have high proton permselectivity against vanadium ions and exhibit low electrical resistance in acidic electrolyte solutions because of its enormous proton concentration and small thickness. The zeolite membrane was demonstrated to be an efficient ion exchange membrane in vanadium redox flow batteries. PMID:24396857

Xu, Zhi; Michos, Ioannis; Wang, Xuerui; Yang, Ruidong; Gu, Xuehong; Dong, Junhang

2014-03-01

341

Monitoring of the crystallization of zeolite LTA using Raman and chemometric tools.  

PubMed

LTA zeolite is used both in industry as well as in laboratories, because of its spatial-specific structure which is useful in gas adsorption and in ion exchange separation. At-line reaction monitoring and multivariate analysis of data, such as Principal Component Analysis (PCA), are fundamentals of the Process Analytical Technology (PAT), which consists of the use of analyzers with rapid detection and low sample preparation for analysis during the process stream. In this work, an optimization of zeolite LTA synthesis was performed aiming to obtain nanocrystals and the synthesis was monitored using Raman spectroscopy and PCA. A reaction mixture of 6.2Na2O?:?Al2O3?:?2SiO2?:?128H2O was used and it was possible to obtain a small particle size and high crystallinity after 72 h of synthesis at 25 °C. The synthesis was monitored at-line, using Raman spectroscopy in both liquid and solid phases. The extension of the reaction could be clearly observed by the PCA scores. As expected, the liquid phase presented changes over time, but the solid phase presented three specific stationary conditions at 0-24 h, 32-56 h and 72-80, related to the beginning of the reaction, the nucleation process, and the crystal formation, respectively. In addition, it was possible to identify the intermediates of the reaction and with the aid of PCA to monitor the reaction close to the real time. PMID:25460364

Chaves, T F; Soares, F L F; Cardoso, D; Carneiro, R L

2014-12-01

342

The characterisation by luminescence spectroscopy of uranium(VI) incorporated into zeolites and aluminas  

NASA Astrophysics Data System (ADS)

Luminescence spectroscopy of solids at 77 K has been used to characterise the uranium(VI) species incorporated into ?-alumina, ?-alumina and zeolites Y and ZSM-20 by adsorption from solution and into ZSM-5 by chemical synthesis. With uranyl adsorbed from nitrate solutions onto ?- and ?-aluminas, the luminescence measurements show the dominant uranium species is schoepite, UO 3· xH 2O, in agreement with results from X-ray diffraction and Raman spectroscopy. With uranyl acetate, there are indications that a crystalline acetate species is also present. With zeolite-Y and ZSM-20, the main species is a dimer. In addition, some monomeric [UO 2(H 2O) 5] 2+ is also present. With ZSM-5, although this is not observed in X-ray diffraction, the luminescence spectrum shows the presence of a species, similar to the schoepite seen with the aluminas. It is suggested that this may be due both to closely related polymeric species, and to uranyl anions, such as [UO 2(OH) 4] 2- and [UO 2(OH) 3] -.

Azenha, M. E. D. G.; da Graça Miguel, M.; Formosinho, S. J.; Burrows, H. D.

2001-05-01

343

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

NASA Astrophysics Data System (ADS)

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

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

2008-05-01

344

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

E-print Network

Oxygen transport in zeolite Y measured by quenching of encapsulated tris(bipyridyl)ruthenium Abstract This study deals with emission quenching of zeolite encapsulated trisbipyridyl ruthenium (II) (Ru the migration of O2 within zeolites using the emis- sion quenching of zeolite encapsulated ruthenium

Dutta, Prabir K.

345

Photochemical template removal and spatial patterning of zeolite MFI thin films using UV/ozone treatment  

E-print Network

Photochemical template removal and spatial patterning of zeolite MFI thin films using UV of thin films of microporous or zeolite materials. We prepared thin-films of a high silica zeolite leads to complete removal of template (structure-direc- ting-agent) from zeolite films comparable

Parikh, Atul N.

346

1 Flexibility As an Indicator of Feasibility of Zeolite Frameworks 2 Colby J. Dawson,  

E-print Network

1 Flexibility As an Indicator of Feasibility of Zeolite Frameworks 2 Colby J. Dawson, Vitaliy Kapko two 6 million unique hypothetical zeolite structures. By a simple flexibility calculation, we have 7 feasibility as zeolites. 78 out of 97 officially approved zeolite framework types 9 that occur in the database

Thorpe, Michael

347

Zeolite Nanoslabs? On the TEM and AFM Evidence of Zeosil Nanoslabs  

E-print Network

Zeolite Nanoslabs? On the TEM and AFM Evidence of Zeosil Nanoslabs Present during the Synthesis · nanoslabs · silicates · zeolites The mechanism of formation of syn- thetic zeolite structures has been a subject of many recent investigations.[1­3] One of the commonly studied zeolites is silicalite-1

Kokkoli, Efie

348

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

USGS Publications Warehouse

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

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

1985-01-01

349

Preparation of a Versatile Bifunctional Zeolite for Targeted Imaging Applications  

PubMed Central

Bifunctional zeolite Y was prepared for use in targeted in vivo molecular imaging applications. The strategy involved functionalization of the external surface of zeolite Y with chloropropyltriethoxysilane followed by reaction with sodium azide to form azide-functionalized NaY, which is amenable to copper(1) catalyzed click chemistry. In this study, a model alkyne (4-pentyn-1-ol) was attached to the azide-terminated surface via click chemistry to demonstrate feasibility for attachment of molecular targeting vectors (e.g., peptides, aptamers) to the zeolite surface. The modified particle efficiently incorporates the imaging radioisotope gallium-68 (68Ga) into the pores of the azide-functionalized NaY zeolite to form a stable bifunctional molecular targeting vector. The result is a versatile “clickable” zeolite platform that can be tailored for future in vivo molecular targeting and imaging modalities. PMID:21306141

Ndiege, Nicholas; Raidoo, Renugan; Schultz, Michael K.; Larsen, Sarah

2011-01-01

350

A pair distribution function analysis of zeolite beta  

SciTech Connect

We describe the structural refinement of zeolite beta using the local structure obtained with the pair distribution function (PDF) method. A high quality synchrotron and two neutron scattering datasets were obtained on two samples of siliceous zeolite beta. The two polytypes that make up zeolite beta have the same local structure; therefore refinement of the two structures was possible using the same experimental PDF. Optimized structures of polytypes A and B were used to refine the structures using the program PDFfit. Refinements using only the synchrotron or the neutron datasets gave results inconsistent with each other but a cyclic refinement with the two datasets gave a good fit to both PDFs. The results show that the PDF method is a viable technique to analyze the local structure of disordered zeolites. However, given the complexity of most zeolite frameworks, the use of both X-ray and neutron radiation and high-resolution patterns is essential to obtain reliable refinements.

Martinez-Inesta, M.M.; Peral, I.; Proffen, T.; Lobo, R.F. (Delaware); (LANL)

2010-07-20

351

Synthesis and catalytic applications of combined zeolitic/mesoporous materials  

PubMed Central

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

Vernimmen, Jarian; Cool, Pegie

2011-01-01

352

Process wastewater treatment with hydrogen-form CST and chabazite zeolite  

SciTech Connect

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

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

1998-05-01

353

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

NASA Technical Reports Server (NTRS)

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.

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

2010-01-01

354

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

NASA Astrophysics Data System (ADS)

This paper presents the results of the synthesis and characterization of inorganic polymers (IP) from aluminosilicates: bentonite (BT) and pumice (PP). The synthesis of IP, was carried out by two methods involving alkaline activation, at room temperature and 80 ± 5 °C, using as activating agent sodium silicate both commercial and analytical (Na2SiO3). Sodium hydroxide (NaOH) at 3 M, 7 M and 12 M was added. A lower degree of polymerization was obtained by using analytical precursors subjected to room temperature and 80 ± 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).

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

2014-06-01

355

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

356

Oxidative regeneration of toluene-saturated natural zeolite by gaseous ozone: the influence of zeolite chemical surface characteristics.  

PubMed

In this study, the effect of zeolite chemical surface characteristics on the oxidative regeneration of toluene saturated-zeolite samples is investigated. A Chilean natural zeolite (53% clinoptilolite, 40% mordenite and 7% quartz) was chemically modified by acid treatment with hydrochloric acid and by ion-exchange with ammonium sulphate. Thermal pre-treatments at 623 and 823K were applied and six zeolite samples with different chemical surface characteristics were generated. Chemical modification of natural zeolite followed by thermal out-gassing allows distinguishing the role of acidic surface sites on the regeneration of exhausted zeolites. An increase in Brønsted acid sites on zeolite surface is observed as a result of ammonium-exchange treatment followed by thermal treatment at 623K, thus increasing the adsorption capacity toward toluene. High ozone consumption could be associated to a high content of Lewis acid sites, since these could decompose ozone into atomic active oxygen species. Then, surface oxidation reactions could take part among adsorbed toluene at Brønsted acid sites and surface atomic oxygen species, reducing the amount of adsorbed toluene after the regenerative oxidation with ozone. Experimental results show that the presence of adsorbed oxidation by-products has a negative impact on the recovery of zeolite adsorption capacity. PMID:24794812

Alejandro, Serguei; Valdés, Héctor; Manéro, Marie-Hélène; Zaror, Claudio A

2014-06-15

357

Structure and properties of sodium aluminosilicate glasses from molecular dynamics simulations  

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

358

Effects of hydrated sodium calcium aluminosilicate on fescue toxicosis and mineral absorption.  

PubMed

The possibility of supplementing livestock diets with an aluminosilicate to protect them from fescue toxicosis was investigated. An in vitro study showed that hydrated sodium calcium aluminosilicate (HSCAS) removed greater than 90% of the ergotamine from aqueous solutions at pH 7.8 or lower, indicating a high affinity of ergotamine for HSCAS in vitro. Rats fed diets containing tall fescue seed infested (E+) with the endophytic fungus Acremonium coenophialum had lower (P less than .05) feed intakes and weight gains than did rats fed diets containing uninfested (E-) tall fescue seed. When feed intake by rats fed the E- seed diet was limited to that of rats fed the E+ seed diet, weight gains did not differ, but testes weights and serum prolactin (PRL) concentrations were lower (P less than .05 and .10, respectively) in rats receiving E+ seed. Supplementing E+ seed diets with HSCAS did not eliminate effects of E+ seed on intake, PRL, or testes weights. Sheep fed E+ tall fescue hay had higher (P less than .05) rectal temperatures than did sheep fed an equal amount of E- tall fescue hay, but OM and N digestion coefficients did not differ between the two hays. Supplementing E+ hay diets with HSCAS did not eliminate the effect of E+ hay on rectal temperatures. Addition of 2% HSCAS to tall fescue hay diets did not affect apparent absorption by sheep of OM, N, Ca, P, Na, K, or Cu, but it reduced (P less than .05) the apparent absorption of Mg, Mn, and Zn.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1328128

Chestnut, A B; Anderson, P D; Cochran, M A; Fribourg, H A; Gwinn, K D

1992-09-01

359

Charge Transport through a Novel Zeolite Y Membrane by a Self-Exchange Process Hyunjung Lee and Prabir K. Dutta*  

E-print Network

Charge Transport through a Novel Zeolite Y Membrane by a Self-Exchange Process Hyunjung Lee, and relatively pinhole-free zeolitic membranes is described. Nanocrystalline zeolite Y (100-200 nm) is used zeolite membranes toward this end.3 Zeolitic membranes are an active area of research because

Dutta, Prabir K.

360

Electrical properties of zeolitized volcaniclastic materials  

NASA Astrophysics Data System (ADS)

The interpretation of electromagnetic anomalies associated with volcanic activity requires a good understanding of two rock properties, the electrical conductivity and the streaming potential coupling coefficient. We measured these properties on 22 consolidated tuff samples containing clays and zeolites typically found in hydrothermal systems or in other areas of high water-rock interactions associated with active volcanic areas. These rocks exhibit unusually high surface conductivity and electrical cementation exponent (2.5-3.3). These features are explained by the highly complex texture of these rocks due to hydration/dissolution processes of the volcanic glass and the formation of clay minerals and zeolites as alteration products. At a pore fluid conductivity of 1.0 +/- 0.2 S m-1, the streaming potential coupling coefficient ranges from -3.55 to -10.7 mV MPa-1. The zeta potential (a key electrochemical property of the pore water/mineral interface) determined from these measurements at T0 = 20°C and pH ~6-7 and corrected for surface conductivity is ~-28 +/- 8 mV at 0.1 M NaCl. Two clay-free samples exhibit a zeta potential ~-16 +/- 5 mV, a value associated with zeolites (clinoptilolite). The temperature dependence of the ? potential is rather strong with ?(T) = ?(T0) [1 + ?? (T - T0)], where ?? ~ 4.2 × 10-2 C-1 in the temperature range 20-60°C. These data are applied to the understanding of large-scale self-potential anomalies located at the ground surface of Miyake-Jima volcano.

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

2002-08-01

361

Carbon dioxide sensitivity of zeolitic imidazolate frameworks.  

PubMed

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

Mottillo, Cristina; Friš?i?, Tomislav

2014-07-14

362

Formation of aluminosilicate geopolymers from 1:1 layer-lattice minerals pre-treated by various methods: a comparative study  

Microsoft Academic Search

Materials resembling aluminosilicate geopolymers have been prepared from the kaolinitic 1:1 layer lattice aluminosilicate\\u000a clay mineral halloysite by reaction with sodium silicate solution under alkaline conditions. The effect on geopolymer formation\\u000a of pretreating the clay mineral reactant by heating, high-energy grinding or exposure to acid or alkali was monitored by the\\u000a ability of the samples to cure and harden, and

Kenneth J. D. MacKenzie; Dan R. M. Brew; Ross A. Fletcher; R. Vagana

2007-01-01

363

Synthesis of zeolite phases from combustion by-products.  

PubMed

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

Pimraksa, Kedsarin; Chindaprasirt, Prinya; Setthaya, Naruemon

2010-12-01

364

Zeolite Crystal Growth (ZCG) Flight on USML-2  

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

365

ESCA study of rhodium(III)-exchanged zeolite catalysts  

SciTech Connect

Samples of both the often investigated rhodium(III)-zeolite Y and the seldom investigated rhodium(III)-zeolite A were prepared and studied by techniques of electron spectroscopy for chemical analysis (ESCA) both in the originally exchanged condition and after activation to the state in which they would be employed in a catalytic capacity. The ESCA data agree with previously reported ESR data which indicated that Rh(III) may be thermally reduced to Rh metal in the zeolite Y lattice, and that this reduction takes place under much milder conditions than comparable reduction of any other metal previously reported. Contrarily, the ESCA data indicated that Rh(III) was not reduced on the zeolite A, and this lack of reduction may be the explanation for the poor catalytic effect of Rh(III) supported on zeolite A. It is postulated that the metallic Rh produced by the activation of Rh(III)-exchanged zeolite Y and not the Rh(III) species is the true catalytic species in the so-called Rh(III)-zeolite catalysts. (BLM)

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

1980-09-01

366

Electron transfer reactions within zeolites: Radical cation from benzonorbornadiene  

SciTech Connect

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

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

1996-08-28

367

Zeolite crystal growth in space - What has been learned  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

368

Ion exchange of ammonium in natural and synthesized zeolites.  

PubMed

In this study, zeolite Na-P and Na-Y was prepared by hydrothermal treatment of the Chinese natural clinoptilolite with NaOH. The ion exchange of NH4+ into the three zeolites in the temperature range of 288-333K was also investigated, and the thermodynamic parameters were calculated. The selectivity sequence for NH4+ entering the sodium form of the three materials was Na-clinoptilolite>Na-Y>Na-P, as indicated by values of DeltaG degrees . The results demonstrated that the Si/Al molar ratio of zeolites determined the selectivity for NH4+. PMID:18417280

Wang, Yifei; Lin, Feng; Pang, Wenqin

2008-12-30

369

Radiation effects on a zeolite ion exchanger and a pollucite  

SciTech Connect

Cation exchange capacity and selective Cs and Sr ion sorption measurements were found to be too insensitive to detect radiation effects on irradiated Ionsiv-IE-95 zeolite. However, leaching the zeolite while under ..gamma..-irradiation caused a modest increase in the desorption of exchangeable ions. Gamma-irradiation and subsequent leaching of a natural pollucite also slightly enhanced the leachability of this material. The increased desorption of ions from the zeolite and the enhanced leachability of the pollucite are apparently caused by a decrease in pH due to the generation of acidic species during irradiation.

Komarneni, S.; Palau, G.L.; Pillay, K.K.S.

1983-01-01

370

Method of preparing sodalite from chloride salt occluded zeolite  

DOEpatents

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

Lewis, M.A.; Pereira, C.

1997-03-18

371

Zeolite-filled PDMS membranes. 1. Sorption of halogenated hydrocarbons  

SciTech Connect

Aiming at a more thorough understanding of the influence of zeolite fillers in PDMS membranes on the pervaporation of chlorinated hydrocarbons from aqueous solutions, the sorption aspect of this separation process was studied. Firstly, the sorption of water and five different chlorinated hydrocarbons was investigated in the zeolite and the polymer separately. Secondly, the composite system was considered and conclusions were drawn concerning interactions at the zeolite-polymer interphase. Finally, the sorption results obtained on the self-synthesized membranes were compared with measurements on commercially available PDMS membranes (GFT). 23 refs., 11 figs., 3 tabs.

Vankelecom, I.F.J.; Dotermont, C.; Morobe, M.; Uytterhoeven, J.B.; Vandecasteele, C. [Katholieke Universiteit Leuven (Belgium)] [Katholieke Universiteit Leuven (Belgium)

1997-03-20

372

Quantitatively Probing the Al Distribution in Zeolites  

SciTech Connect

The degree of substitution of Si4+ by Al3+ in the oxygen-terminated tetrahedra (Al T-sites) of zeolites determines the concentration of ion-exchange and Brønsted acid sites. As the location of the tetrahedra and the associated subtle variations in bond angles influence the acid strength, quantitative information about Al T-sites in the framework is critical to rationalize catalytic properties and to design new catalysts. A quantitative analysis is reported that uses a combination of extended X-ray absorption fine structure (EXAFS) analysis and 27Al MAS NMR spectroscopy supported by DFT-based molecular dynamics simulations. To discriminate individual Al atoms, sets of ab initio EXAFS spectra for various T-sites are generated from DFT-based molecular dynamics simulations allowing quantitative treatment of the EXAFS single- and multiple-photoelectron scattering processes out to 3-4 atom shells surrounding the Al absorption center. It is observed that identical zeolite types show dramatically different Al-distributions. A preference of Al for T-sites that are part of one or more 4-member rings in the framework over those T-sites that are part of only 5- and 6-member rings in the HBEA150 sample has been determined from a combination of these methods. This work was supported by the U. S. Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences.

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

2014-06-11

373

Evaluation of natural zeolite as microorganism support medium in nitrifying batch reactors: influence of zeolite particle size.  

PubMed

An evaluation of natural zeolite as a microorganism carrier in nitrifying reactors operated in batch mode was carried out. Specifically, the influence of zeolite particle sizes of 0.5, 1.0 and 2.0 mm in diameter on microorganism adherence to zeolite, ammonium adsorption capacity and the identification of microbial populations were assessed. The greatest amount of total biomass adhered was observed for a zeolite particle size of 1 mm (0.289 g) which was achieved on the 12th day of operation. The highest ammonium adsorption capacity was observed for a zeolite particle size of 0.5 mm, which was 64% and 31% higher than that observed for particle sizes of 1.0 and 2.0 mm, respectively. The maximum de-sorption values were also found for a zeolite particle size of 0.5 mm, although when equilibrium was reached the ammonium concentrations were similar to those observed for a zeolite particle size of 1.0 mm. It was also found that the experimental data on ammonium adsorption fitted very well to the Freundlich isotherm for the three particle sizes studied. Finally, the nitrifying reactors showed similar microbial populations independently of the particle size used as microorganism carrier. The dominant bacterial community was Gammaproteobacteria making up 80% of the total population found. Betaproteobacteria were also identified and made up 12% approx. of the total population. Ammonium Oxidant Betaproteobacteria and Nitrobacter were also detected. PMID:22320694

Mery, C; Guerrero, L; Alonso-Gutiérrez, J; Figueroa, M; Lema, J M; Montalvo, S; Borja, R

2012-01-01

374

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

Microsoft Academic Search

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

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

1994-01-01

375

Ab initio calculations on aluminosilicate Q3 species: Implications for atomic structures of mineral surfaces and dissolution mechanisms of feldspars  

Microsoft Academic Search

Molecular orbital calculations on various aluminosilicate Q3 T-OHand bridging0 spe- cies were performed to model atomic structural changes on mineral surfaces that occur as a function of pH. Calculated vibrational frequencies are reported for the terminal T-O, T-OH, and O-H bonds of the central T cation as a test of our models, and the predicted frequencies compare well with experimental

J. D. KUBICKI; G. A. BLAKE; E. APITZ

1996-01-01

376

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

Microsoft Academic Search

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

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

1991-01-01

377

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

SciTech Connect

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

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

2010-02-15

378

Permeability of crystalline rocks  

NASA Astrophysics Data System (ADS)

In contrast to most other petrophysical parameters, intrinsic permeability for any single rock type varies by the decade rather than by the factor (see, for example, Bear [1972]). Both the type of measurement and its characteristic scale (that is, the rock volume over which an individual permeability value is integrated) are responsible for this. Brace [1980, 1984] compiled permeabilities of sedimentary (porous) and crystalline (fractured) rocks and pointed out that both types of rock exhibit a “scale effect”: the larger the experiment's scale, or characteristic volume, the greater the permeability. One other transport parameter, dispersion length or dispersivity, which is closely related to permeability, behaves similarly. There are both data compilations for dispersivity documenting this scale effect [Beims, 1983; Gelhar et al., 1985] and theoretical studies (such as Neumann [1990]) discussing possible scaling rules. An interesting conclusion by Neumann [1990], which is in good agreement with Brace's results, is that "porous and fractured media appear to follow the same idealized scaling rule for both flow and transport, raising a question about the validity of many distinctions commonly drawn between such media."

Clauser, Christoph

379

Generalized structural description of calcium-sodium aluminosilicate hydrate gels: the cross-linked substituted tobermorite model.  

PubMed

Structural models for the primary strength and durability-giving reaction product in modern cements, a calcium (alumino)silicate hydrate gel, have previously been based solely on non-cross-linked tobermorite structures. However, recent experimental studies of laboratory-synthesized and alkali-activated slag (AAS) binders have indicated that the calcium-sodium aluminosilicate hydrate [C-(N)-A-S-H] gel formed in these systems can be significantly cross-linked. Here, we propose a model that describes the C-(N)-A-S-H gel as a mixture of cross-linked and non-cross-linked tobermorite-based structures (the cross-linked substituted tobermorite model, CSTM), which can more appropriately describe the spectroscopic and density information available for this material. Analysis of the phase assemblage and Al coordination environments of AAS binders shows that it is not possible to fully account for the chemistry of AAS by use of the assumption that all of the tetrahedral Al is present in a tobermorite-type C-(N)-A-S-H gel, due to the structural constraints of the gel. Application of the CSTM can for the first time reconcile this information, indicating the presence of an additional activation product that contains highly connected four-coordinated silicate and aluminate species. The CSTM therefore provides a more advanced description of the chemistry and structure of calcium-sodium aluminosilicate gel structures than that previously established in the literature. PMID:23534827

Myers, Rupert J; Bernal, Susan A; San Nicolas, Rackel; Provis, John L

2013-04-30

380

Evidence for Al/Si tetrahedral network in aluminosilicate glasses from Al K-edge x-ray-absorption spectroscopy  

NASA Astrophysics Data System (ADS)

The structure of aluminosilicate melts and/or glasses plays a key role in the earth sciences for the understanding of rock-forming igneous processes, as well as in the materials sciences for their technical applications. In particular, the alkaline-earth aluminosilicate glasses are an extremely important group of materials, with a wide range of commercial application, as well as serving as an analog for natural basaltic melts. However, definition of their structure and properties is still controversial, and in particular the role and effect of Al has long been a subject of debate. Here we report a series of experimental x-ray absorption near-edge structure spectra at the Al K edge on a series of synthetic glasses of peralkaline composition in the CaO-Al2O3-SiO2 system, together with a general theoretical framework for data analysis based on an ab initio full multiple-scattering theory. We propose an Al/Si tetrahedral network model for aluminosilicate glasses based on distorted polyhedra, with varying both the T-O (T=Al or Si) bond lengths and the T-O-T angles, and with different Al/Si composition. This model achieves a significant agreement between experiments and simulations. In these glasses, experimental data and theoretical results concur to support a model in which Al is network former with a comparatively well ordered local medium-range order (up to 5 Å).

Wu, Ziyu; Romano, C.; Marcelli, A.; Mottana, A.; Cibin, G.; della Ventura, G.; Giuli, G.; Courtial, P.; Dingwell, D. B.

1999-10-01

381

Alkali aluminosilicate melts and glasses: structuring at the middle range order of amorphous matter  

NASA Astrophysics Data System (ADS)

Rheological properties of silicate melts govern both magma ascension from the mantle to the surface of the earth and volcanological eruptions styles and behaviours. It is well known that several parameters impact strongly these properties, such as for instance the temperature, pressure, chemical composition and volatiles concentration, finally influencing eruptive behaviour of volcanoes. In this work, we will focus on the Na2O-K2O-Al2O3-SiO2 system, which is of a prime importance because it deals with a non-negligible part of natural melts, like for instance the Vesuvius (Italy) or Erebus (Antartica) magmas. In an oncoming paper in Chemical Geology (Le Losq and Neuville, 2012), we have communicated results of the study of mixing Na-K in tectosilicate melts containing a high concentration of silica (?75mol%). In the present communication, we will enlarge this first point of view to tectosilicate melts presenting a lower silica concentration. We will first present our viscosity data, and then the Adam and Gibbs theory that allows theoretically modelling Na-K mixing in aluminosilicate melts by using the so-called "mixed alkali effect". On the basis of the rheological results, the Na-K mixing cannot be explained with the ideal "mixed alkali effect", which involves random exchange of Na-K cationic pairs. To go further and as rheological properties are directly linked with structural properties, we will present our first results obtained by Raman and NMR spectroscopy. These last ones provide important structural pieces of information on the polymerization state of glasses and melts, and also on the environment of tetrahedrally coordinated cations. Rheological and structural results all highlight that Na and K are not randomly distributed in aluminosilicate glasses and melts networks. Na melts present a network with some channels and a non-random distribution of Al and Si. K networks are different. They also present a non-random distribution of Al and Si, but in two sub-networks: one is rich in Si and fully polymerized, the other is richer in Al and K. The size of K+ ions combined to the charge-balancing needs of Al3+ ions determine this structuring of potassium melts. Mixing Na and K melts thus returns to mix two different networks: one composed of Na-Al-Si-O atoms and another of K-Al-Si-O atoms. This impact melts properties, inducing complicated and non-linear effects.

Le Losq, C.; neuville, D. R.

2012-12-01

382

Chlorine, in the Presence of Iron, Does Indeed Decrease the Viscosity of Aluminosilicate Melts  

NASA Astrophysics Data System (ADS)

The effect of volatiles on melt rheology is investigated here, as the degassing of magma before an eruption usually leads to an increase in magma viscosity; and therefore increases the probability of an explosive eruption. There is not a large amount of data on the effect of chlorine on viscosity. It would appear, however, that chlorine increases the viscosity of peralkaline sodium-aluminosilicate melts, and decreases the viscosity of peraluminous sodium-aluminosilicate melts. These different effects of chlorine on viscosity indicate that the chlorine sits in different structural sites in peraluminous and peralkaline melts. In previous studies of rheology in this laboratory, we have shown that chlorine does indeed increase the viscosity of a phonolite analog Na2O-CaO-Al2O3-SiO2 melt. In this study, we have extended our investigation of the rheology of chlorine-bearing melts to basaltic compositions. The melt composition used here is that of a basaltic glass taken from the mid-Atlantic Ridge at 3000 m depth during the Venture Cruise (Ireland) of 2011. The viscosities were determined using the micropenetration technique in the 109-1012 Pa s range at temperatures 600-800 C. It was found that the addition of 0.6 wt% Cl resulted in a 0.5 log unit decrease in viscosity. A synthetic haplo-basaltic melt with the iron replaced by Mg and the Al was also synthesized. The addition of 0.3 wt% chlorine to this melt resulted in a 0.3 log unit increase in viscosity; as observed previously for Fe-free peralkaline melts. Based on these viscosity data it would appear that the effect of chlorine on rheology is a function of the composition of the melt, and that the structural site taken by chlorine varies as a function of the presence or absence of iron. The addition of chlorine to the iron-bearing melt, increased the Fe2+/Fetot from 0.30 to 0.45. This indicates that the presence of chlorine results in an energetic preference for Fe2+ in the melt structure. Thus, it is not so much the structural role of chlorine which results in a decrease in viscosity in iron-bearing melts, but the formation of more network modifying Fe2+ at the expense of network forming Fe3+ which causes the viscosity decrease.

Webb, S. L.

2012-12-01

383

High-silica zeolite nucleation from clear solutions  

E-print Network

. 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...

Cheng, Chil-Hung

2006-04-12

384

Oxidation of bioethanol using zeolite-encapsulated gold nanoparticles.  

PubMed

With the ongoing developments in biomass conversion, the oxidation of bioethanol to acetaldehyde may become a favorable and green alternative to the preparation from ethylene. Here, a simple and effective method to encapsulate gold nanoparticles in zeolite silicalite-1 is reported and their high activity and selectivity for the catalytic gas-phase oxidation of ethanol are demonstrated. The zeolites are modified by a recrystallization process, which creates intraparticle voids and mesopores that facilitate the formation of small and disperse nanoparticles upon simple impregnation. The individual zeolite crystals comprise a broad range of mesopores and contain up to several hundred gold nanoparticles with a diameter of 2-3?nm that are distributed inside the zeolites rather than on the outer surface. The encapsulated nanoparticles have good stability and result in 50?% conversion of ethanol with 98?% selectivity toward acetaldehyde at 200?°C, which (under the given reaction conditions) corresponds to 606?mol?acetaldehyde/mol?Au?hour(-1) . PMID:25196739

Mielby, Jerrik; Abildstrøm, Jacob Oskar; Wang, Feng; Kasama, Takeshi; Weidenthaler, Claudia; Kegnaes, Søren

2014-11-10

385

CO2 capture using zeolite 13X prepared from bentonite  

NASA Astrophysics Data System (ADS)

Zeolite 13X was prepared using bentonite as the raw material by alkaline fusion followed by a hydrothermal treatment without adding any extra silica or alumina sources. The prepared zeolite 13X was characterized by X-ray powder diffraction, N2-adsorption-desorption measurements, and scanning electron microscopy. The CO2 capture performance of the prepared zeolite 13X was examined under both static and flow conditions. The prepared zeolite 13X showed a high BET surface area of 688 m2/g with a high micropore volume (0.30 cm3/g), and exhibited high CO2 capture capacity (211 mg/g) and selectivity to N2 (CO2/N2 = 37) at 25 °C and 1 bar. In addition, the material showed fast adsorption kinetics, and stable CO2 adsorption-desorption recycling performance at both 25 and 200 °C.

Chen, Chao; Park, Dong-Wha; Ahn, Wha-Seung

2014-02-01

386

Net charge and polarizability of zeolitic Brønsted acidic sites  

NASA Astrophysics Data System (ADS)

The interacting induced-dipoles polarization model, implemented in our program POLAR, is used for the calculation of the effective polarizability of the zeolitic bridged OH group, which results much higher than that of the free silanol group. A high polarizability is also calculated for the bridged OH group with a Si4+, in the absence of Lewis-acid promotion of silanol by Al3+. The crystal polarizability is estimated from the Clausius-Mossotti relationship. Siliceous zeolites are low-permittivity isolators. The interaction of a weak base with the zeolitic OH can be considered as a local bond. Only when cations are located in the zeolite micropore, next to tetrahedra that contain trivalent cations, are large electrostatic fields generatedE They are short ranged, and the positive cation charges are compensated.0

Torrens, F.; Castellano, G.

387

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

388

Zeolite an efficient catalyst for the Biginelli condensation reaction  

Microsoft Academic Search

A zeolite catalyzed, single step and environmentally friendly process for synthesis of classical Biginelli reaction was investigated.\\u000a For this reaction Transition metal\\/Y zeolites were prepared by microwave solid-state and aqueous solution ion-exchange methods.\\u000a The yield of reactions was increased in order of CuY > CoY > NiY > MnY ? FeY > VY > CrY > ZnY for the solid-state zeolite\\u000a ion-exchange and CuY > CoY > NiY > MnY > CrY > VY > ZnY > FeY for the aqueous solution ion-exchange. The solid-state ion-exchange\\u000a zeolite by

Mojgan Zendehdel; A. Mobinikhaledi; A. Asgari

2008-01-01

389

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

Microsoft Academic Search

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

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

2009-01-01

390

Radiation effects on a zeolite ion exchanger and a pollucite  

Microsoft Academic Search

Cation exchange capacity and selective Cs and Sr ion sorption measurements were found to be too insensitive to detect radiation effects on irradiated Ionsiv-IE-95 zeolite. However, leaching the zeolite while under ..gamma..-irradiation caused a modest increase in the desorption of exchangeable ions. Gamma-irradiation and subsequent leaching of a natural pollucite also slightly enhanced the leachability of this material. The increased

S. Komarneni; G. L. Palau; K. K. S. Pillay

1983-01-01

391

Metal Oxide/Zeolite Combination Absorbs H2S  

NASA Technical Reports Server (NTRS)

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

Voecks, Gerald E.; Sharma, Pramod K.

1989-01-01

392

Zeolites and mesoporous materials as advanced functional material  

Microsoft Academic Search

With their unique regular channel system, porous materials offer a wide range of applications as host-guest system ranging from membranes with a molecular sieve function to devices with laser or sensor function. The state of the art of the development of zeolites and zeolite-like materials as advanced materials with (i) separation, (ii) electric\\/electronic, and (iii) optical functions is evaluated.

2004-01-01

393

Removal of Metal Cations from Water Using Zeolites  

Microsoft Academic Search

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 (-40, +65 mesh) varied from 0.48 to 0.93 g\\/mL. Attrition losses ranged from 1 to

M. J. Zamzow; J. E. Murphy

1992-01-01

394

Metal ion exchange by natural and modified zeolites  

Microsoft Academic Search

The lead and cadmium removal from wastewaters by natural and pretreatment zeolites was examined by using a batch-type method. The results demonstrated that the natural zeolites contained a complement of exchangeable Na, K and Ca ions but exposing them to 2 M NaCl solution at 22 and 70°C, respectively, converted them to a near homoionic state in Na-form. Lead and

L. ?urkovi?; Š. Cerjan-Stefanovi?; T. Filipan

1997-01-01

395

Microstructural Optimization of a Zeolite Membrane for Organic Vapor Separation  

Microsoft Academic Search

A seeded growth method for the fabrication of high-permeance, high-separation-factor zeolite (siliceous ZSM-5, [Si96O192]-MFI) membranes is reported. The method consists of growing the crystals of an oriented seed layer to a well-intergrown film by avoiding events that lead to a loss of preferred orientation, such as twin overgrowths and random nucleation. Organic polycations are used as zeolite crystal shape modifiers

Zhiping Lai; Griselda Bonilla; Isabel Diaz; Jose Geraldo Nery; Khristina Sujaoti; Miguel A. Amat; Efrosini Kokkoli; Osamu Terasaki; Robert W. Thompson; Michael Tsapatsis; Dionisios G. Vlachos

2003-01-01

396

Electrochemical regeneration of zeolites and the removal of ammonia  

Microsoft Academic Search

The electrochemical regeneration of zeolites was investigated with the objective of removing ammonia from water harmlessly and reusing the regeneration solution in an undivided electrochemical cell assembled with a Ti\\/IrO2–Pt anode and a Cu\\/Zn cathode. Zeolites could be completely regenerated through the electrochemical method in this study. With NaCl as a supporting electrolyte, the conversion rate of ammonia adsorbed by

Xiaohui Lei; Miao Li; Zhenya Zhang; Chuanping Feng; Wei Bai; Norio Sugiura

2009-01-01

397

A theoretical explanation of solvent effects in zeolite catalysis  

Microsoft Academic Search

In a previous study of solid acid catalysis (Nature (1998) 389, 832) we showed that the catalytic activity of zeolites could\\u000a be increased by the coadsorption of “solvent” molecules, such as nitromethane. These coadsorbates do not participate directly\\u000a in the reaction, but alter the environment within the zeolite such that reactivity is increased. In this work we provide further\\u000a theoretical

John B. Nicholas

1999-01-01

398

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

NASA Astrophysics Data System (ADS)

The effects of pressure on aluminosilicate melt and glass structure have been studied by both in-situ methods and by quenching and recovering glasses from high pressure and temperature. Significant increases in the coordination number of Al are now well known from the pressure range of 6-10 GPa. New results show that even at shallower mantle pressures of 1-3 GPa, typical aluminosilicate melts have significant concentrations of aluminum cations with coordination numbers greater than 4, with up to 10's of percents of AlO5 and AlO6. Here, we compare the densities and Al coordinations of glass samples recovered from piston-cylinder experiments carried out at 1 to 3 GPa and different temperatures. Samples of two different compositions (Ca3Al2Si6O18 and Na2Si3O7 with 0.5% Al2O3) were compressed and held at temperatures ranging from near to their ambient glass transitions (Tg) up to temperatures above the liquidus. Our 2 GPa sodium aluminosilicate and calcium aluminosilicate glasses quenched from near to Tg show about 5 and 6 percent recovered densification, respectively. In both compositions, samples that were quenched from above the melting point showed substantially lower recovered density and lower Al coordination number compared to the samples that were held near to Tg. For example, sodium aluminosilicate glass quenched from 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.

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

2013-12-01

399

Synthesis of hydrothermally stable, hierarchically mesoporous aluminosilicate Al-SBA-1 and their catalytic properties.  

PubMed

Hydrothermally stable mesoporous aluminosilicates Al-SBA-1 with hierarchical pore structure have been successfully synthesized under alkaline condition at 120 °C by employing organic mesomorphous complexes of polyelectrolyte (poly(acrylic acid) (PAA)) and cationic surfactant (hexadecyl pyridinium chloride (CPC)) as template. The Si/Al ratio could be as high as 5 and the incorporation of Al into the silica framework did not disturb the well-ordered cubic Pm ?3n mesostructure. Meanwhile, the incorporation of Al could greatly increase the specific surface area and pore volume of the samples. The Al-SBA-1 materials exhibited a high hydrothermal stability and remained stable even after being treated in boiling water for 10 days. The catalytic activity of the Al-SBA-1 materials was investigated by employing the Friedel-Crafts alkylation of toluene with benzyl alcohol as a model reaction and they exhibited excellent catalytic property due to the incorporated acid sites and the hierarchically mesoporous structure. PMID:22327221

Li, Na; Wang, Jin-Gui; Xu, Jian-Xiong; Liu, Jin-Yu; Zhou, Hui-Jing; Sun, Ping-Chuan; Chen, Tie-Hong

2012-03-21

400

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

SciTech Connect

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

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

2003-02-20

401

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

SciTech Connect

The compressive strengths and structures of composites of aluminosilicate geopolymer with the synthetic cement minerals C{sub 3}S, beta-C{sub 2}S, C{sub 3}A and commercial OPC were investigated. All the composites showed lower strengths than the geopolymer and OPC paste alone. X-ray diffraction, {sup 29}Si and {sup 27}Al MAS NMR and SEM/EDS observations indicate that hydration of the cement minerals and OPC is hindered in the presence of geopolymer, even though sufficient water was present in the mix for hydration to occur. In the absence of SEM evidence for the formation of an impervious layer around the cement mineral grains, the poor strength development is suggested to be due to the retarded development of C-S-H because of the preferential removal from the system of available Si because geopolymer formation is more rapid than the hydration of the cement minerals. This possibility is supported by experiments in which the rate of geopolymer formation is retarded by the substitution of potassium for sodium, by the reduction of the alkali content of the geopolymer paste or by the addition of borate. In all these cases the strength of the OPC-geopolymer composite was increased, particularly by the combination of the borate additive with the potassium geopolymer, producing an OPC-geopolymer composite stronger than hydrated OPC paste alone.

Tailby, Jonathan, E-mail: jmtailby@hotmail.co [School of Chemical and Physical Sciences Victoria University of Wellington, P.O. Box 600 Wellington (New Zealand); MacKenzie, Kenneth J.D. [School of Chemical and Physical Sciences Victoria University of Wellington, P.O. Box 600 Wellington (New Zealand)

2010-05-15

402

Single-walled aluminosilicate nanotube/poly(vinyl alcohol) nanocomposite membranes.  

PubMed

The fabrication, detailed characterization, and molecular transport properties of nanocomposite membranes containing high fractions (up to 40 vol %) of individually-dispersed aluminosilicate single-walled nanotubes (SWNTs) in poly(vinyl alcohol) (PVA), are reported. The microstructure, SWNT dispersion, SWNT dimensions, and intertubular distances within the composite membranes are characterized by scanning and transmission electron microscopy (SEM and TEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), XRD rocking curve analysis, small-angle X-ray scattering (SAXS), and solid-state NMR. PVA/SWNT nanocomposite membranes prepared from SWNT gels allow uniform dispersion of individual SWNTs in the PVA matrix with a random distribution of orientations. SAXS analysis reveals the length (?500 nm) and outer diameter (~2.2 nm) of the dispersed SWNTs. Electron microscopy indicates good adhesion between the SWNTs and the PVA matrix without the occurrence of defects such as voids and pinholes. The transport properties of the PVA/SWNT membranes are investigated experimentally by ethanol/water mixture pervaporation measurements, computationally by grand canonical Monte Carlo and molecular dynamics, and by a macroscopic transport model for anisotropic permeation through nanotube-polymer composite membranes. The nanocomposite membranes substantially enhance the water throughput with increasing SWNT volume fraction, which leads to a moderate reduction of the water/ethanol selectivity. The model is parameterized purely from molecular simulation data with no fitted parameters, and shows reasonably good agreement with the experimental water permeability data. PMID:22260317

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

2012-02-01

403

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

SciTech Connect

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

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

2012-05-29

404

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

SciTech Connect

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

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

2011-06-01

405

Water solubility in calcium aluminosilicate glasses investigated by first principles techniques  

NASA Astrophysics Data System (ADS)

First-principles techniques have been employed to study the reactivity of water into a calcium aluminosilicate glass. In addition to the well known hydrolysis reactions Si-O-Si+H2O?Si-OH+Si-OH and Si-O-Al+H2O?Si-OH+Al-OH, a peculiar mechanism is found, leading to the formation of an AlO 3-H 2O entity and the breaking of Al-O-Si bond. In the glass bulk, most of the hydrolysis reactions are endothermic. Only a few regular sites are found reactive ( i.e. in association with an exothermic reaction), and in that case, the hydrolysis reaction leads to a decrease of the local disorder in the amorphous vitreous network. Afterwards, we suggest that ionic charge compensators transform into network modifiers when hydrolysis occurs, according to a global process firstly suggested by Burnham in 1975. Our theoretical computations provide a more general model of the first hydrolysis steps that could help to understand experimental data and water speciation in glasses.

Bouyer, Frédéric; Geneste, Grégory; Ispas, Simona; Kob, Walter; Ganster, Patrick

2010-12-01

406

Molecular dynamics simulations of uranyl and uranyl carbonate adsorption at aluminosilicate surfaces.  

PubMed

Adsorption at mineral surfaces is a critical factor controlling the mobility of uranium(VI) in aqueous environments. Therefore, molecular dynamics (MD) simulations were performed to investigate uranyl(VI) adsorption onto two neutral aluminosilicate surfaces, namely, the orthoclase (001) surface and the octahedral aluminum sheet of the kaolinite (001) surface. Although uranyl preferentially adsorbs as a bidentate inner-sphere complex on both surfaces, the free energy of adsorption on the orthoclase surface (-15 kcal mol(-1)) is significantly more favorable than that at the kaolinite surface (-3 kcal mol(-1)), which is attributed to differences in surface functional groups and the ability of the orthoclase surface to release a surface potassium ion upon uranyl adsorption. The structures of the adsorbed complexes compare favorably with X-ray absorption spectroscopy results. Simulations of the adsorption of uranyl complexes with up to three carbonate ligands revealed that uranyl complexes coordinated to up to two carbonate ions are stable on the orthoclase surface whereas uranyl carbonate surface complexes are unfavored at the kaolinite surface. Combining the MD-derived equilibrium adsorption constants for orthoclase with aqueous equilibrium constants for uranyl carbonate species indicates the presence of adsorbed uranium complexes with one or two carbonates under alkaline conditions, in support of current uranium(VI) surface complexation models. PMID:24580048

Kerisit, Sebastien; Liu, Chongxuan

2014-04-01

407

Zeolite synthesis from fly ash and cement kiln dust  

SciTech Connect

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

Grutzeck, M.W. [Pennsylvania State Univ., University Park, PA (United States)

1996-12-31

408

Synthesis and characterization of nanocrystalline and mesoporous zeolites  

NASA Astrophysics Data System (ADS)

Mesoporous aggregates of nanocrystalline zeolites with MFI and BEA frameworks have been synthesized using a one-pot and single structure directing agent. The effect of different reaction conditions, such as temperature, time, pH and water content, on the particle size, surface area and mesopore volume has been studied. Nanocrystalline and mesoporous ZSM-5, beta and Y zeolites were modified with different transition metals and the resulting single- and double metal containing catalyst materials were characterized. Nanocrystalline Silicalite-1 zeolite samples with varying particle size were functionalized with different organosilane groups and the cytotoxic activity of the zeolite nanocrystals was studied as a function of particle size, concentration, organic functional group type, as well as the type of cell line. Framework stability of nanocrystalline NaY zeolite was tested under different pH conditions. The synthesized zeolites used in this work were characterized using a variety of physico-chemical methods, including powder X-ray diffraction, Solid State NMR, nitrogen sorption, electron microscopy, Inductively Coupled Plasma -- Optical Emission Spectroscopy and X-ray Photoelectron Spectroscopy.

Petushkov, Anton

2011-12-01

409

Zeolitic ammonium ion exchange for portable hemodialysis dialysate regeneration.  

PubMed

Ammonia removal from a recirculating dialysate stream is a major challenge in developing a truly portable, regenerable hemodialysis system. Three zeolites, type F, type W, and clinoptilolite, were found to have good ammonia ion exchange capacity with linear equilibrium ion exchange coefficients of 0.908, 0.488, and 0.075 L/g, respectively. The linear equilibrium ion exchange coefficient relates dialysate ammonia concentration (mumol/L) to the amount of ammonia absorbed by zeolite (mumol/g) at equilibrium. Ammonia uptake by zeolite powders was fast, with equilibrium reached within 15 sec. Zeolite ammonia ion exchange and regeneration through multiple cycles was studied using an ion exchange column containing clinoptilolite pellets. Zeolite ion exchange capability was regenerated by flushing the column with 2 mol/L sodium chloride after an ion exchange run. The column maintained ammonia ion exchange capacity through six ion exchange/regeneration cycles, demonstrating multiple dialysis use possibilities. Atomic absorption spectroscopy of the column effluent showed no detectible (< 1 part per million) Si or Al leached from the zeolite. PMID:7640432

Patzer, J F; Yao, S J; Wolfson, S K

1995-01-01

410

Characterization of Chemical Properties, Unit Cell Parameters and Particle Size Distribution of Three Zeolite Reference Materials: RM 8850 - Zeolite Y, RM 8851 - Zeolite A and RM 8852 - Ammonium ZSM-5 Zeolite  

SciTech Connect

Zeolites have important industrial applications including use as catalysts, molecular sieves and ion exchange materials. In this study, three zeolite materials have been characterized by the National Institute of Standards and Technology (NIST) as reference materials (RMs): zeolite Y (RM 8850), zeolite A (RM 8851) and ZSM-5 zeolite (RM 8852). They have been characterized by a variety of chemical and physical measurement methods: X-ray fluorescence (XRF), gravimetry, instrumental neutron activation analysis (INAA), nuclear magnetic resonance (NMR), calorimetry, synchrotron X-ray diffraction, neutron diffraction, laser light extinction, laser light scattering, electric sensing zone, X-ray sedimentation, scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM) and optical microscopy. The chemical homogeneity of the materials has been characterized. Reference values are given for the major components (major elements, loss on ignition [LOI] and loss on fusion [LOF]), trace elements and Si/Al and Na/Al ratios. Information values are given for enthalpies of formation, unit cell parameters, particle size distributions, refractive indices and variation of mass with variation in relative humidity (RH). Comparisons are made to literature unit cell parameters. The RMs are expected to provide a basis for intercomparison studies of these zeolite materials.

Turner,S.; Sieber, J.; Vetter, T.; Zeisler, R.; Marlow, A.; Moreno-Ramirez, M.; Davis, M.; Kennedy, G.; Borghard, W.; et al

2008-01-01

411

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

PubMed

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

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

2014-08-15

412

A comparative evaluation of IONSIV{reg_sign} IE-911 and chabazite zeolite for the removal of radiostrontium and cesium from wastewater  

SciTech Connect

Natural chabazite zeolite was selected as the baseline treatment technology for the removal of fission products, namely {sup 90}Sr and {sup 137}Cs, from near-neutral-pH process wastewater and groundwater. The sorbent IONSIV{reg_sign} IE-911, a crystalline silicotitanate manufactured by UOP, was recently tested in this capacity and found to compare extremely well against the baseline material. This paper presents and compares the results of similar batch and column tests performed using both materials, and summarizes the physical and chemical characteristics of the sorbents.

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

1998-11-01

413

Preparation of zeolite NaA for CO2 capture from nickel laterite residue  

NASA Astrophysics Data System (ADS)

Zeolite NaA was successfully prepared from nickel laterite residue for the first time via a fusion-hydrothermal procedure. The structure and morphology of the as-synthesized zeolite NaA were characterized with a range of experimental techniques, such as X-ray diffraction, scanning electronic microscopy, and infrared spectroscopy. It was revealed that the structures of the produced zeolites were dependent on the molar ratios of the reactants and hydrothermal reaction conditions, so the synthesis conditions were optimized to obtain pure zeolite NaA. Adsorption of nitrogen and carbon dioxide on the prepared zeolite NaA was also measured and analyzed. The results showed that zeolite NaA could be prepared with reasonable purity, it had physicochemical properties comparable with zeolite NaA made from other methods, and it had excellent gas adsorption properties, thus demonstrating that zeolite NaA could be prepared from nickel laterite residue.

Du, Tao; Liu, Li-ying; Xiao, Penny; Che, Shuai; Wang, He-ming

2014-08-01

414

First zeolite carbon replica with a well resolved X-ray diffraction pattern.  

PubMed

The present study demonstrates that for the nanocasting process with zeolites, a careful choice of the zeolite structure type (EMT) allows the formation of faithful carbon replica exhibiting up to three well resolved XRD peaks. PMID:16491186

Gaslain, Fabrice O M; Parmentier, Julien; Valtchev, Valentin P; Patarin, Joël

2006-03-01

415

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

NASA Astrophysics Data System (ADS)

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.

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

2011-01-01

416

Diffusion of an alkane molecule in siliceous zeolite beta Matthew Aronson  

E-print Network

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

Shell, M. Scott

417

Alpha-B-Crystallin in Neuropathology  

Microsoft Academic Search

?B-Crystallin, which has homology with the small heat shock proteins, is the basic subunit of ?-crystallin, a major component of the vertebrate eye lens. These crystallins have for a long time been thought to be absolutely lens specific. However, about a decade ago ?B-crystallin has been detected extralenticularly in many tissues among which the central nervous system. Under pathological conditions

A. F. van Rijk; H. Bloemendal

2000-01-01

418

Microwave-assisted hydrothermal synthesis of zeolite films on ceramic supports  

Microsoft Academic Search

Zeolite films were formed on ceramic supports by a novel microwave-assisted hydrothermal method and were characterized by\\u000a XRD, SEM, FTIR and BET surface area. The two-stage synthesis technique consists of microwave heating of supports saturated\\u000a with precursor solution to form a thin layer of zeolite nano-seeds, followed by hydrothermal treatment to crystallize MFI\\u000a zeolite. The resulting zeolite formation time was

C. D. Madhusoodana; R. N. Das; Y. Kameshima; K. Okada

2006-01-01

419

Gas detection with SnO 2 sensors modified by zeolite films  

Microsoft Academic Search

Zeolite films have been grown on top of SnO2 sensors to modify their response to gas phase molecules with the aim of improving their selectivity. To this end SnO2 sensors were first prepared using conventional procedures, and then zeolite layers (silicalite and zeolite A) were grown on the outer SnO2 surface, using different synthesis procedures. The zeolite-modified sensors were tested

Montserrat Vilaseca; Joaquin Coronas; Albert Cirera; Albert Cornet; Joan Ramon Morante; Jesus Santamaria

2007-01-01

420

Influence of zeolites on the sintering and technological properties of porcelain stoneware tiles  

Microsoft Academic Search

Low-cost zeolitic rocks are promising substitutes for feldspathic fluxes in ceramic bodies, since their fusibility, modest hardness and high cation exchange capacity (CEC) should improve grinding and sintering. Five large-scale Italian deposits of natural zeolites with different mineralogy were characterised and tested in porcelain stoneware bodies. Their behaviour during processing was appraised and compared with that of zeolite-free bodies. Zeolites

Roberto de’ Gennaro; Piergiulio Cappelletti; Guido Cerri; Maurizio de’ Gennaro; Michele Dondi; Guia Guarini; Alessio Langella; Debora Naimo

2003-01-01

421

Tubular-type pervaporation module with zeolite NaA membrane  

Microsoft Academic Search

Zeolite NaA membranes were prepared on the surfaces of porous tubular supports composed of mullite, ?-alumina and\\/or cristobalite using the hydrothermal synthesis. The zeolite NaA crystals and the surface morphologies of the membranes were characterized by X-ray diffraction and SEM. EPMA analysis revealed that the zeolite composite membranes consisted of three layers — the zeolite layer, the intermediate layer and

Masakazu Kondo; Mitsuru Komori; Hidetoshi Kita; Ken-ichi Okamoto

1997-01-01

422

Solution properties of ?-crystallins: Hydration of fish and mammal ?-crystallins  

PubMed Central

Lens ? crystallins are found at the highest protein concentration of any tissue, ranging from 300 mg/mL in some mammals to over 1000 mg/mL in fish. Such high concentrations are necessary for the refraction of light, but impose extreme requirements for protein stability and solubility. ?-crystallins, small stable monomeric proteins, are particularly associated with the lowest hydration regions of the lens. Here, we examine the solvation of selected ?-crystallins from mammals (human ?D and mouse ?S) and fish (zebrafish ?M2b and ?M7). The thermodynamic water binding coefficient B1 could be probed by sucrose expulsion, and the hydrodynamic hydration shell of tightly bound water was probed by translational diffusion and structure-based hydrodynamic boundary element modeling. While the amount of tightly bound water of human ?D was consistent with that of average proteins, the water binding of mouse ?S was found to be relatively low. ?M2b and ?M7 crystallins were found to exhibit extremely low degrees hydration, consistent with their role in the fish lens. ?M crystallins have a very high methionine content, in some species up to 15%. Structure-based modeling of hydration in ?M7 crystallin suggests low hydration is associated with the large number of surface methionine residues, likely in adaptation to the extremely high concentration and low hydration environment in fish lenses. Overall, the degree of hydration appears to balance stability and tissue density requirements required to produce and maintain the optical properties of the lens in different vertebrate species. PMID:24282025

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

2014-01-01

423

The role of zeolite beta nanoparticles solutions in the synthesis of zeolite-functionalised materials with bimodal porosity  

NASA Astrophysics Data System (ADS)

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.

Van Oers, Cynthia J.

424

Inelastic X-ray Scattering Studies of Zeolite Collapse  

Microsoft Academic Search

In situ inelastic x-ray scattering (IXS) experiments have been used to probe heterogeneity and deformability in zeolte Y as this thermally collapses to a high density amorphous (HDA) aluminosilicate phase. The Landau-Placzek ratio RLP falls slowly as amorphisation advances, increasing in the later stages of collapse clearly showing how homogeneity improves non-linearly-behaviour linked closely with the decline in molar volume

G. Neville Greaves; Florian Kargl; David Ward; Peter Holliman; Florian Meneau

2009-01-01

425

Rotationally Molded Liquid Crystalline Polymers  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

426

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

E-print Network

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

Earl, David J.

427

Ion exchange of zeolite membranes by a vacuum `flow-through' Seok-Jhin Kim a  

E-print Network

Ion exchange of zeolite membranes by a vacuum `flow-through' technique Seok-Jhin Kim October 2014 Keywords: Ion exchange Zeolite membrane Flow-through technique Separation Catalysis a b s t r a c t Ion exchange of nanoporous (e.g., zeolite) membranes is of increasing importance

Nair, Sankar

428

Catalytic Transformation of C7-C9 Methyl Benzenes over USY-based FCC Zeolite Catalyst  

E-print Network

Catalytic Transformation of C7-C9 Methyl Benzenes over USY-based FCC Zeolite Catalyst S. Al (toluene, m-xylene, and 1,2,4-trimethyl benzene) has been investigated over USY based FCC zeolite catalyst for the m-xylene. December 2005 Keywords: FCC zeolite catalyst; USY; Toluene; m-Xylene; Disproportionation

Al-Khattaf, Sulaiman

429

Zeolite-Mediated Photochemical Charge Separation Using a Surface-Entrapped Ruthenium-Polypyridyl Complex  

E-print Network

Zeolite-Mediated Photochemical Charge Separation Using a Surface-Entrapped Ruthenium)ethenyl]benzene (L), a polypyridyl complex of ruthenium(II) was tethered on the surface of zeolite Y. Electrochemical photolysis of the ruthenium-zeolite solid ion-exchanged with diquat and suspended in a propyl viologen

Dutta, Prabir K.

430

Dealumination–aging pattern of REUSY zeolites contained in fluid cracking catalysts  

Microsoft Academic Search

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

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

431

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

ERIC Educational Resources Information Center

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

Smoot, Alison L.; Lindquist, David A.

1997-01-01

432

UTILITY OF SYNTHETIC ZEOLITES IN REMOVAL OF INORGANIC AND ORGANIC WATER POLLUTANTS  

EPA Science Inventory

Zeolites are well known for their ion exchange and adsorption properties. Different inorganic and organic pollutants have been removed from water at room temperature using various zeolites. Synthetic zeolites like ZSM-5, Ferrierite, Beta and Faujasite Y have been used to remove i...

433

Effect of Micropore Topology on the Structure and Properties of Zeolite Polymer Replicas  

E-print Network

Effect of Micropore Topology on the Structure and Properties of Zeolite Polymer Replicas Stacy A Received September 10, 1997X Zeolites were used as templates to prepare microporous polymer replicas. Phenol- formaldehyde polymers were synthesized and cured within the channel networks of zeolites Y

434

Effects of composition and phonon scattering mechanisms on thermal transport in MFI zeolite films  

E-print Network

Effects of composition and phonon scattering mechanisms on thermal transport in MFI zeolite films of different phonon scattering processes on thermal transport in the nanoporous zeolite MFI of Physics. DOI: 10.1063/1.2776006 I. INTRODUCTION Zeolites are nanoporous mixed-oxide crystals with com

Nair, Sankar

435

Spectroscopic study of the dehydration and/or dehydroxylation of phyllosilicate and zeolite minerals  

E-print Network

Spectroscopic study of the dehydration and/or dehydroxylation of phyllosilicate and zeolite, and chlorite) and two natural zeolites are reported here. Pressed powders of sizeseparated phyllosilicate and natural zeolite samples were heated incrementally from 100°C to 900°C, cooled to room temperature

Glotch, Timothy D.

436

The comparative ion exchange capacities of natural sedimentary and synthetic zeolites  

Microsoft Academic Search

A large tonnage of natural, sedimentary zeolites is found in the Western United States and world-wide. They offer a substantial potential for a variety of industrial uses including the removal of cations from acid mine drainage and industrial waste waters. There is a wide variation in the cation exchange capacity of zeolites because of the differing nature of various zeolite

K. D. Mondale; R. M. Carland; F. F. Aplan

1995-01-01

437

Materials Chemistry and Physics 83 (2004) 8995 Microwave preparation of Li-zeolite directly from  

E-print Network

Materials Chemistry and Physics 83 (2004) 89­95 Microwave preparation of Li-zeolite directly from in revised form 3 September 2003; accepted 12 September 2003 Abstract Li-zeolites were successfully and lithium hydroxide as the hydrolytic agent. Many types of Li-zeolites were obtained by controlling

Gulari, Erdogan

438

Sorption of arsenic by surfactant-modified zeolite and kaolinite Zhaohui Li a,*, Ryan Beachner a  

E-print Network

Sorption of arsenic by surfactant-modified zeolite and kaolinite Zhaohui Li a,*, Ryan Beachner Available online 2 April 2007 Abstract In this study, the feasibility of using surfactant-modified zeolite- adecyltrimethylammonium, a cationic surfactant, on zeolite and kaolinite surfaces exceeded monolayer coverage

Li, Zhaohui

439

Identification of iron cyclam complexes encapsulated inside zeolite Y Xile Hu, Karsten Meyer *  

E-print Network

Identification of iron cyclam complexes encapsulated inside zeolite Y Xile Hu, Karsten Meyer complexes formed inside the supercages of zeolite-Y. Especially interesting is the identification Fe(V) nitrido species. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Zeolite; Cage

Meyer, Karsten

440

Density Functional Theory Investigations of the Direct Oxidation of Methane on an Fe-Exchanged Zeolite  

E-print Network

-Exchanged Zeolite WanZhen Liang,,,§ Alexis T. Bell,*, Martin Head-Gordon, and Arup K. Chakraborty, Department-exchange site in the zeolite] is lower in energy by 7.7 kcal/mol, assuming a spin multiplicity M ) 6-exchanged ZSM-5 zeolite pretreated at an elevated temperature with N2O and then exposed to methane at room

Bell, Alexis T.

441

Modeling Spontaneous Formation of Precursor Nanoparticles in Clear-Solution Zeolite Synthesis  

E-print Network

Modeling Spontaneous Formation of Precursor Nanoparticles in Clear-Solution Zeolite Synthesis M zeolite. Silica condensation/hydrolysis is modeled by a nearest-neighbor attraction, while growth by Ostwald ripening. We suggest that this mechanism may play a role in the growth of zeolite

Auerbach, Scott M.

442

Locating stationary points of sorbate-zeolite potential energy surfaces using interval analysis  

E-print Network

Locating stationary points of sorbate-zeolite potential energy surfaces using interval analysis in a zeolite can be studied using transition-state theory. In this application, and other applications points, transition states, zeolites, diffusion, interval-Newton method Author to whom all correspondence

Stadtherr, Mark A.

443

UV-Raman spectroscopy on nanotubes@zeolite Wavelength dependence Ab initio calculations  

E-print Network

UV-Raman spectroscopy on nanotubes@zeolite June, 2005 Wavelength dependence Ab initio calculations involving the peak at 650 cm-1. Nanotubes grown inside the channels of zeolite crystals are constrained in the zeolite. · Further peaks cannot be explained by only 4 °A-diameter nanotubes. · Calculations

Nabben, Reinhard

444

Spectroscopic Studies of Colloidal Solutions of Nanocrystalline Ru(bpy)3 2+-Zeolite Y  

E-print Network

Spectroscopic Studies of Colloidal Solutions of Nanocrystalline Ru(bpy)3 2+-Zeolite Y Norma B of Ru(bpy)3 2+-zeolite Y has made it possible to use conventional optical transmission spectroscopic methods to examine the entrapped Ru(bpy)3 2+ species within the zeolite. To prepare the suspensions

Dutta, Prabir K.

445

Removal of Heavy Metals and Other Cations from Wastewater Using Zeolites  

Microsoft Academic Search

Zeolites from abundant natural deposits were investigated by the Bureau of Mines for efficiently cleaning up mining industry wastewaters. Twenty-two zeolites were analyzed by X-ray diffraction and inductively coupled plasma analysis (ICP). These included clinoptilolite, mordenite, chabazite, erionite, and phillipsite. The zeolites were primarily in the sodium or calcium form, but potassium and magnesium counter ions were also present. Bulk

M. J. Zamzow; B. R. Eichbaum; K. R. Sandgren; D. E. Shanks

1990-01-01

446

Framework stabilization of Si-rich LTA zeolite prepared in organic-free media.  

PubMed

Zeolite HOU-2 (LTA type) is prepared with the highest silica content (Si/Al = 2.1) reported for Na-LTA zeolites without the use of an organic structure-directing agent. The rational design of Si-rich zeolites has the potential to improve their thermal stability for applications in catalysis, gas storage, and selective separations. PMID:25347029

Conato, Marlon T; Oleksiak, Matthew D; Peter McGrail, B; Motkuri, Radha K; Rimer, Jeffrey D

2015-01-01

447

Microwave-assisted preparation of zeolite KH from alumatrane and Mathavee Sathupunya a  

E-print Network

Microwave-assisted preparation of zeolite K­H from alumatrane and silatrane Mathavee Sathupunya-loaded zeolite was synthesized for the first time, via sol­gel processing and microwave heating techniques on x-ray diffraction analysis, the synthesized product is a K­H zeolite of hitherto unknown structure

Gulari, Erdogan

448

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

E-print Network

Temperature dependent thermal conductivity of pure silica MEL and MFI zeolite thin films Jin Fang,1 dependent cross-plane thermal conductivity of pure silica zeolite (PSZ) MFI and MEL thin films measured of MFI zeolite was predicted and discussed using the Callaway model based on the Debye approximation. VC

Pilon, Laurent

449

Helicity Selective Separation of Zeolite-supported Single-walled Carbon Nanotubes Synthesized from  

E-print Network

1 Helicity Selective Separation of Zeolite-supported Single-walled Carbon Nanotubes Synthesized on metal supported Zeolite.10,11 Purification and helicity selective separation of SWNTs is still an important challenge. Two methods for purification, removal of metal catalysts and Zeolite, of SWNTs produced

Maruyama, Shigeo

450

Surface Structure of Zeolite (MFI) Crystals Isabel Diaz,, Efrosini Kokkoli, Osamu Terasaki, and Michael Tsapatsis*,  

E-print Network

Articles Surface Structure of Zeolite (MFI) Crystals Isabel Di´az,,§ Efrosini Kokkoli, Osamu type MFI) is an important zeolite that, in addition to conventional applications such as adsorption in studies of zeolite crystal growth. The surface structure of silicalite-1 crystals with two different

Kokkoli, Efie

451

Zeolite Surface as a Catalyst Support Material for Synthesis of Single-Walled Carbon Nanotubes  

E-print Network

1 Zeolite Surface as a Catalyst Support Material for Synthesis of Single-Walled Carbon Nanotubes support material. Although zeolite has been frequently used as a catalyst support material for the synthesis of SWNTs, detailed surface properties of previously employed zeolites, and thus their role

Maruyama, Shigeo