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1

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

2

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

3

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

4

Crystalline-amorphous transition in silicate perovskites  

SciTech Connect

CaSiO{sub 3} and MgSiO{sub 3} perovskites are known to undergo solid-state crystal to amorphous transitions near ambient pressure when decompressed from their high-pressure stability fields. In order to elucidate the mechanistic aspects of this transition we have performed detailed molecular-dynamics simulations and lattice-dynamical calculations on model silicate perovskite systems using empirical rigid-ion pair potentials. In the simulations at low temperatures, the model perovskite systems transform under tension to a low-density glass composed of corner shared chains of tetrahedral silicon. The amorphization is initiated by a thermally activated step involving a soft polar optic mode in the perovskite phase at the Brillouin zone center. Progression of the system along this reaction coordinate triggers, in succession, multiple barrierless modes of instability ultimately producing a catastrophic decohesion of the lattice. An important intermediary along the reaction path is a crystalline phase where silicon is in a five-coordinate site and the alkaline-earth metal atom is in eightfold coordination. At the onset pressure, this transitory phase is itself dynamically unstable to a number of additional vibrational modes, the most relevant being those which result in transformation to a variety of tetrahedral chain silicate motifs. These results support the conjecture that stress-induced amorphization arises from the near simultaneous accessibility of multiple modes of instability in the highly metastable parent crystalline phase.

Hemmati, M. [Department of Chemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States)] [Department of Chemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States); Chizmeshya, A. [Department of Chemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States)] [Department of Chemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States); [Idaho National Engineering Laboratory, EG& G Idaho, P.O. Box 1625, Idaho Falls, Idaho 83415-2208 (United States); Wolf, G.H.; Poole, P.H.; Shao, J.; Angell, C.A. [Department of Chemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States)] [Department of Chemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States)

1995-06-01

5

The identification of crystalline olivine in cometary silicates  

NASA Astrophysics Data System (ADS)

An intermediate-resolution spectrum of the 8-13 micron region in comet Halley is obtained which shows a prominent silicate emission feature with structure not observed before in other comets or in interstellar silicates. The presence of a strong 11.3 micron peak reported by Bregman and coworkers is confirmed, and evidence is found for additional structure in the band. By comparison with spectra of interplanetary dust particles and laboratory silicates, it is concluded that small crystalline olivine particles are a major component of the silicates in this comet; other silicates (e.g., amorphous or hydrated) must also be present. The identification of crystalline olivine in this part of the spectrum is supported by the observation of four peaks in 20-50 micron airborne spectra of this comet which have also been attributed to olivine.

Campins, H.; Ryan, E. V.

1989-06-01

6

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

7

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

8

Crystalline-amorphous transition in silicate perovskites  

Microsoft Academic Search

CaSiO3 and MgSiO3 perovskites are known to undergo solid-state crystal to amorphous transitions near ambient pressure when decompressed from their high-pressure stability fields. In order to elucidate the mechanistic aspects of this transition we have performed detailed molecular-dynamics simulations and lattice-dynamical calculations on model silicate perovskite systems using empirical rigid-ion pair potentials. In the simulations at low temperatures, the model

Mahin Hemmati; Andrew Chizmeshya; George H. Wolf; Peter H. Poole; Jun Shao; C. Austen Angell

1995-01-01

9

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

10

Application of thermodynamics to silicate crystalline solutions  

NASA Technical Reports Server (NTRS)

A review of thermodynamic relations is presented, describing Guggenheim's regular solution models, the simple mixture, the zeroth approximation, and the quasi-chemical model. The possibilities of retrieving useful thermodynamic quantities from phase equilibrium studies are discussed. Such quantities include the activity-composition relations and the free energy of mixing in crystalline solutions. Theory and results of the study of partitioning of elements in coexisting minerals are briefly reviewed. A thermodynamic study of the intercrystalline and intracrystalline ion exchange relations gives useful information on the thermodynamic behavior of the crystalline solutions involved. Such information is necessary for the solution of most petrogenic problems and for geothermometry. Thermodynamic quantities for tungstates (CaWO4-SrWO4) are calculated.

Saxena, S. K.

1972-01-01

11

Crystalline silicates and hydrocarbon-conversion processes employing same  

SciTech Connect

Novel crystalline silicates which in dehydrated form have the composition in terms of moles of the oxides: (1.0 +- 3)(R)2/no.(AFe/sub 2/O/sub 3/.BAl/sub 2/O/sub 3/ . CGa/sub 2/O/sub 3/ . Y(DSiO/sub 2/ . EGeO/sub 2/)), wherein R one or more mono- or bivalent cations and A, B, C, D, E, Y and N are as defined hereinafter are disclosed. The thermally stable silicates are suitably employed as extracting agents, drying agents, ion exchange agents, catalysts and catalyst carriers.

Kouwenhoven, H.W.; Stork, W.H.

1980-12-09

12

?-? 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

13

?-? 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

14

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

15

Calcium-aluminum-silicate-hydrate "cement" phases and rare Ca-zeolite association at Colle Fabbri, Central Italy  

NASA Astrophysics Data System (ADS)

Very high temperature, Ca-rich alkaline magma intruded an argillite formation at Colle Fabbri, Central Italy, producing cordierite-tridymite metamorphism in the country rocks. An intense Ba-rich sulphate-carbonate-alkaline hydrothermal plume produced a zone of mineralization several meters thick around the igneous body. Reaction of hydrothermal fluids with country rocks formed calcium-silicate-hydrate (CSH), i.e., tobermorite-afwillite-jennite; calcium-aluminum-silicate-hydrate (CASH) — "cement" phases - i.e., thaumasite, strätlingite and an ettringite-like phase and several different species of zeolites: chabazite-Ca, willhendersonite, gismon-dine, three phases bearing Ca with the same or perhaps lower symmetry of phillipsite-Ca, levyne-Ca and the Ca-rich analogue of merlinoite. In addition, apophyllite-(KF) and/or apophyllite-(KOH), Ca-Ba-carbonates, portlandite and sulphates were present. A new polymorph from the pyrrhotite group, containing three layers of sphalerite-type structure in the unit cell, is reported for the first time. Such a complex association is unique. Most of these minerals are specifically related to hydration processes of: (1) pyrometamorphic metacarbonate/metapelitic rocks (natural analogues of cement clinkers); (2) mineralization between intrusive stocks and slates; and (3) high-calcium, alkaline igneous rocks such as melilitites and foidites as well as carbonatites. The Colle Fabbri outcrop offers an opportunity to study in situ complex crystalline overgrowth and specific crystal chemistry in mineral phases formed in igneous to hydrothermal conditions.

Stoppa, F.; Scordari, F.; Mesto, E.; Sharygin, V. V.; Bortolozzi, G.

2010-06-01

16

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

17

[Aluminum coordination and active sites on aluminas, Y-zeolites and pillared layered silicates]. Progress report  

SciTech Connect

This report is organized in four sections. In the first the authors will outline structural features which are common to all fine grained alumina, as well as to non-framework alumina in zeolites. This section will be followed by a study of the surface vs. bulk coordination of aluminum. The third section will deal with measurement of the number of acid sites and the scaling of their strength. The fourth and last section will describe three model reactions: the isomerization of 1-butene and of 2 cis-butene; the isomerization and disproportionation of oxtho-xylene; and the transformation of trichloroethane into vinyl chloride followed by the polymerization of the vinyl chloride. The relationship between chemical activity and selectivity and what is known of the local structure of the active catalytic sites will be underlined. Other kinds of zeolites besides Y zeolite have been studied. Instead of the aluminum pillared silicates they found it more interesting to study the substitution of silicon by aluminum in a layered structure containing a permanent porosity (aluminated sepiolite).

Fripiat, J.J.

1994-02-01

18

Discrete Dipole Approximation Models of Crystalline Forsterite: Applications to Cometary Crystalline Silicates  

NASA Astrophysics Data System (ADS)

In cometary comae, the crystalline silicate forsterite (Mg2SiO4) is the dominant crystalline component. Within the 8 - 40 micron spectral range, the crystal shape has been demonstrated to have a measurable effect on the crystalline features’ shape and peak wavelength locations. We present discrete dipole approximation (DDA) absorption efficiencies for a variety of forsterite grain shapes to demonstrate: a) that the 10, 11, 19, 23, and 33.5 micron resonances are sensitive to grain shape; b) spectral trends are associated with variations in crystallographic axial ratios; and c) that groups of similar grain shapes (shape classes) have distinct spectral features. These computations are performed using DDSCAT v7.0 run on the NASA Advanced Supercomputing (NAS) facility Pleiades. We generate synthetic spectral energy distribution (SED) fits to the Infrared Space Observatory (ISO) SWS spectra for the coma of comet C/1995 O1 (Hale-Bopp) at a heliocentric distance of 2.8 AU. Hale-Bopp is best fit by equant grain shapes whereas rounded grain shapes fit significantly poorer than crystals with sharp edges with well-defined faces. Moreover, crystals that are not significantly elongated along a crystallographic axis fit better. By comparison with Kobatake et al. (2008) condensation experiments and Takigawa et al. (2009) evaporation experiments, our analyses suggest that the forsterite crystals in the coma of Hale-Bopp predominantly are high temperature condensates. The laboratory experiments show that grain shape and grain formation temperature, and hence disk environment, are causally linked. Specifically, the Kobatake et al. (2008) condensation experiment reveals three shape classes associated with temperature: 1) ‘Bulky’ grains (1300 K < T < 1700 K), 2) ‘Platy’ grains (1000 K < T < 1300 K), and 3) columnar/needle grains (T < 1000 K). We construct DDA grain shape analogs to these shape classes to connect grain shapes to distinguishable spectral signatures and crystal formation environments.

Lindsay, Sean; Wooden, D. H.; Woodward, C. E.; Harker, D. E.; Kelley, M. S.; Murphy, J. R.

2012-10-01

19

Hydrothermal synthesis and characterization of copper containing crystalline silicate mesoporous materials from gel mixture  

Microsoft Academic Search

Novel copper-containing crystalline silicate mesoporous materials (SCMM) have been synthesized by the hydrothermal treatment of slurries of silicon–magnesium–copper hydroxide precipitates along with quaternary ammonium salt. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed a house-of-cards type structure consists of very thin platy silicates. Nitrogen adsorption–desorption isotherms of calcined material show that it has a high surface area (?550 m2

M Chatterjee; T Iwasaki; Y Onodera; H Hayashi; Y Ikushima; T Nagase; T Ebina

2004-01-01

20

Entrapment of Ionic Tris(2,2-Bipyridyl) Ruthenium(II) in Hydrophobic Siliceous Zeolite: O2 Sensing in Biological Environments  

E-print Network

Entrapment of Ionic Tris(2,2-Bipyridyl) Ruthenium(II) in Hydrophobic Siliceous Zeolite: O2 SensingVised Manuscript ReceiVed June 5, 2008 Synthesis of the ionic dye, tris(2,2-bipyridyl) ruthenium(II) chloride (Ru the ruthenium compound inside a zeolite supercage ensures permanent entrapment since the 7 Ã? windows

Dutta, Prabir K.

21

Cooked GEMS - Insights into the Hot Origins of Crystalline Silicates in Circumstellar Disks and the Cold Origins of GEMS  

NASA Technical Reports Server (NTRS)

The comparison of interstellar, circumstellar and primitive solar nebula silicates has led to a significant conundrum in the understanding of the nature of solid materials that begin the planet forming processes. Crystalline silicates are found in circumstellar regions around young stars and also evolved stars ejecting particles into the interstellar medium (ISM) but they are not seen in the interstellar medium itself, the source material for star and planet formation. Crystalline silicates are minor to major components of all known early solar system materials that have been examined as meteorites or interplanetary dust samples. The strong presence of Mg-rich crystalline silicates in Oort cloud comets and their minor presence in some Kuiper belt comets is also indicated by 11.2 m peak in approx. 10 microns "silicate" infrared feature. This evidence strongly indicates that Mg-rich crystalline silicates were abundant components of the solar nebula disk out to at least 10 AU, and present out to 30 AU.

Brownlee, D. E.; Joswiak, D. J.; Bradley, J. P.; Matrajt, G.; Wooden, D. H.

2005-01-01

22

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

23

CRYSTALLINE SILICATES IN EVOLVED STARS. I. SPITZER/INFRARED SPECTROGRAPH SPECTROSCOPY OF IRAS 16456-3542, 18354-0638, AND 23239+5754  

SciTech Connect

We report the Spitzer Infrared Spectrograph (IRS) observations of three evolved stars: IRAS 16456-3542, 18354-0638, and 23239+5754. The 9.9-37.2 {mu}m Spitzer/IRS high-resolution spectra of these three sources exhibit rich sets of enstatite-dominated crystalline silicate emission features. IRAS 16456-3542 is extremely rich in crystalline silicates, with >90% of its silicate mass in crystalline form, the highest to date ever reported for crystalline silicate sources.

Jiang, B. W.; Zhang, Ke [Department of Astronomy, Beijing Normal University, Beijing 100875 (China)] [Department of Astronomy, Beijing Normal University, Beijing 100875 (China); Li, Aigen [Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211 (United States)] [Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211 (United States); Lisse, C. M., E-mail: bjiang@bnu.edu.cn, E-mail: kzhang@caltech.edu, E-mail: lia@missouri.edu, E-mail: carey.lisse@jhuapl.edu [Johns Hopkins University, Applied Physics Laboratory, Laurel, MD 20723 (United States)

2013-03-01

24

Discrete dipole approximation models of chrystalline forsterite: Applications to cometary crystalline silicates  

NASA Astrophysics Data System (ADS)

The shape, size, and composition of crystalline silicates observed in comet comae and external proto-planetary disks are indicative of the formation and evolution of the dust grains during the processes of planetary formation. In this dissertation, I present the 3 -- 40 mum absorption efficiencies( Qabs) of irregularly shaped forsterite crystals computed with the discrete dipole approximation (DDA) code DDSCAT developed by Draine and Flatau and run on the NASA Advanced Supercomputing facility Pleiades. An investigation of grain shapes ranging from spheroidal to irregular indicate that the strong spectral features from forsterite are sensitive to grain shape and are potentially degenerate with the effects of crystal solid state composition (Mg-content). The 10, 11, 18, 23, and 33.5 mum features are found to be the most crystal shape sensitive and should be avoided in determining Mg-content. The distinct spectral features for the three shape classes are connected with crystal formation environment using a condensation experiment by (Kobatake et al., 2008). The condensation experiment demonstrates that condensed forsterite crystal shapes are dependent on the condensation environmental temperature. I generate DDSCAT target analog shapes to the condensed crystal shapes. These analog shapes are represented by the three shape classes: 1) equant, 2) a, c-columns, and 3) b-shortened platelets. Each of these shape classes exhibit distinct spectral features that can be used to interpret grain shape characteristics from 8 --- 40 mum spectroscopy of astronomical objects containing crystalline silicates. Synthetic spectral energy distributions (SEDs) of the coma of Hale-Bopp at rh = 2.8 AU are generated by thermally modeling the flux contributions of 5 mineral species present in comets. The synthetic SEDs are constrained using a chi2- minimization technique. The mineral species are amorphous carbon, amorphous pyroxene, amorphous olivine, crystalline enstatite, and crystalline forsterite. Using the DDSCAT computed absorption efficiencies for a large variety of forsterite crystal shapes, which are computed for 66 grain sizes between 0.1 -- 5.0 mum, the flux contribution of irregularly shaped forsterite is computed. The forsterite flux contribution is then summed with the amorphous and crystalline enstatite contributions to generate the total synthetic SED. The DDSCAT forsterite grain shape synthetic SEDs reveal that the crystalline silicates in the coma of Hale-Bopp are irregular in shape with two distinct shape characteristics related to specific formation mechanisms: 1) equant grains with sharp ( ? 90°) angles between the faces, edges, and vertices that formed as high temperature condensates in the inner 1 -- 3 AU radial region of the Solar System's protoplanetary disk; and 2) c-shortened platelet shapes that likely formed from collisional processing of the crystals. The 8 -- 40 mum silicate spectral features of Hale-Bopp's coma are compared to the silicate spectral features of the comae of 17P/Holmes during 2007 outburst and 9P/Tempel 1 during the Deep Impact experiment to show that the silicate features with crystalline resonances are remarkably similar. The similarity in silicate spectral features suggests that the grain populations in the comae of these comets are similar in shape, size, and compositon. However, Hale-Bopp is a nearly isotropic comet (NIC) that dynamically came from the Oort cloud, and 17P and 9P are ecliptic comets (ECs) that dynamically came from the Scattered Disk. The different dynamical source regions yet similar silicate (amorphous and crystalline) grain populations suggest that ECs and NICs innately have similar grains and that the typically weaker silicate features of ECs are an effect of the surface grains becoming compacted with numerous perihelion passages. Hence, the differences in silicate between ECs and NICs are the result of grain structure and not grain composition. (Abstract shortened by UMI.)

Lindsay, Sean Stephen

25

Infrared spectra of crystalline phase ices condensed on silicate smokes at T less than 20 K  

NASA Technical Reports Server (NTRS)

Infrared spectra of H2O, CH3OH, and NH3 condensed at T less than 20 K on amorphous silicate smokes reveal that predominantly crystalline phase ice forms directly on deposit. Spectra of these molecules condensed on aluminum substrates at T less than 20 K indicate that amorphous phase ice forms. On aluminum, crystalline phase H2O and CH3OH are formed by annealing amorphous deposits to 155 K and 130 K, respectively (or by direct deposit at these temperatures); crystalline NH3 is formed by direct deposit at 88 K. Silicate smokes are deposited onto aluminum substrates by evaporation of SiO solid or by combustion of SiH4 with O2 in flowing H2 followed by vapor phase nucleation and growth. Silicate smokes which are oxygen-deficient may contain active surface sites which facilitate the amorphous-to-crystalline phase transition during condensation. Detailed experiments to understand the mechanism are currently in progress. The assumption that amorphous phase ice forms routinely on grains at T less than 80 K is often used in models describing the volatile content of comets or in interpretations of interstellar cloud temperatures. This assumption needs to be reexamined in view of these results.

Moore, Marla H.; Ferrante, Robert F.; Hudson, Reggie L.; Nuth, Joseph A., III; Donn, Bertram

1994-01-01

26

Infrared spectra of crystalline phase ices condensed on silicate smokes at T less than 20 K  

NASA Astrophysics Data System (ADS)

Infrared spectra of H2O, CH3OH, and NH3 condensed at T less than 20 K on amorphous silicate smokes reveal that predominantly crystalline phase ice forms directly on deposit. Spectra of these molecules condensed on aluminum substrates at T less than 20 K indicate that amorphous phase ice forms. On aluminum, crystalline phase H2O and CH3OH are formed by annealing amorphous deposits to 155 K and 130 K, respectively (or by direct deposit at these temperatures); crystalline NH3 is formed by direct deposit at 88 K. Silicate smokes are deposited onto aluminum substrates by evaporation of SiO solid or by combustion of SiH4 with O2 in flowing H2 followed by vapor phase nucleation and growth. Silicate smokes which are oxygen-deficient may contain active surface sites which facilitate the amorphous-to-crystalline phase transition during condensation. Detailed experiments to understand the mechanism are currently in progress. The assumption that amorphous phase ice forms routinely on grains at T less than 80 K is often used in models describing the volatile content of comets or in interpretations of interstellar cloud temperatures. This assumption needs to be reexamined in view of these results.

Moore, Marla H.; Ferrante, Robert F.; Hudson, Reggie L.; Nuth, Joseph A., III; Donn, Bertram

1994-06-01

27

High Silicate Crystalline-to-Amorphous Ratios in Comets C/2001 Q4 (NEAT) and Hale-Bopp  

NASA Technical Reports Server (NTRS)

Crystalline silicates, by their apparent absence in the ISM, are dust grains that experienced high temperatures in the solar nebula. Mg-rich crystalline silicates formed either by condensation from hot nebular gases (1450 K) or by the annealing of Mg-rich amorphous silicates (approximately 1000 K) in shocks in the 5-10AU region or by radial transport into and out of the hot inner zones, e.g., T(sub d) greater than 1000K at r(sub h) less than 5AU, 10(exp -6) -10(exp -5) solar mass per year, alpha = 10(exp -4) of the early solar nebula. Mg-rich crystalline silicates are found in interplanetary dust particles (IDPs) and produce IR spectral features in many Oort cloud comets. In May 2004, we discovered strong crystalline silicate features in the dynamically new Oort cloud comet C/2001 Q4 (NEAT). Thermal emission modeling of comets Q4 and C/1995 O1 (Hale-Bopp) demonstrate that both these comets have similar, high silicate crystalline-toamorphous ratios of 2.4 and 2.1, respectively, indicating that these icy planetesimals aggregated from similar reservoirs of material or that crystalline silicates were widely distributed within the comet-forming zone. This argues for efficient annealing mechanisms and radial mixing.

Wooden, D. H.; Harker, D. E.; Wodward, C. E.

2004-01-01

28

High Silicate Crystalline-to-Amorphous Ratios in Comets C/2001 Q4 (NEAT) and Hale-Bopp  

NASA Technical Reports Server (NTRS)

Crystalline silicates, by their apparent absence in the ISM, are dust grains that experienced high temperatures in the solar nebula. Mg-rich crystalline silicates formed either by condensation from hot nebular gases (1450 K) or by the annealing of Mg-rich amorphous silicates (approx. 1000 K) in shocks in the 5-10 AU region or by radial transport into and out of the hot inner zones, e.g., T(sub d) > 1000 K at r(sub h) < 5 AU, 10(exp -6) - 10(exp -5) M(sub O)/yr, alpha = 10(exp -4) of the early solar nebula. Mg-rich crystalline silicates are found in interplanetary dust particles (IDPs) and produce IR spectral features in many Oort cloud comets. In May 2004, we discovered strong crystalline silicate features in the dynamically new Oort cloud comet C/2001 Q4 (NEAT). Thermal emission modeling of comets Q4 and C/1995 O1 (Hale-Bopp) demonstrate that both these comets have similar, high silicate crystalline-to-amorphous ratios of 2.4 and 2.1, respectively, indicating that these icy planetesimals aggregated from similar reservoirs of material or that crystalline silicates were widely distributed within the comet-forming zone. This argues for efficient annealing mechanisms and radial mixing.

Wooden, D. H.; Harker, D. E.; Woodward, C. E.

2004-01-01

29

Abundant Crystalline Silicates in the Disk of a Very Low Mass Star  

Microsoft Academic Search

We announce the discovery of SST-Lup3-1, a very low mass star close to the brown dwarf boundary in Lupus III with a circum(sub)stellar disk, discovered by the ``Cores to Disks'' Spitzer Legacy Program from mid-infrared, with very conspicuous crystalline silicate features in its spectrum. It is the first of such objects with a full 5-35 mum spectrum taken with the

B. Merín; J.-C. Augereau; E. F. van Dishoeck; J. Kessler-Silacci; C. P. Dullemond; G. A. Blake; F. Lahuis; J. M. Brown; V. C. Geers; K. M. Pontoppidan; F. Comerón; A. Frasca; S. Guieu; J. M. Alcalá; A. C. A. Boogert; N. J. Evans II; P. D'Alessio; L. G. Mundy; N. Chapman

2007-01-01

30

Antimicrobial effects of silver zeolite, silver zirconium phosphate silicate and silver zirconium phosphate against oral microorganisms  

PubMed Central

Objective To evaluate the antimicrobial activities of silver inorganic materials, including silver zeolite (AgZ), silver zirconium phosphate silicate (AgZrPSi) and silver zirconium phosphate (AgZrP), against oral microorganisms. In line with this objective, the morphology and structure of each type of silver based powders were also investigated. Methods The antimicrobial activities of AgZ, AgZrPSi and AgZrP were tested against Streptococcus mutans, Lactobacillus casei, Candida albicans and Staphylococcus aureus using disk diffusion assay as a screening test. The minimum inhibitory concentration (MIC) and minimum lethal concentration (MLC) were determined using the modified membrane method. Scanning electron microscope and X-ray diffraction were used to investigate the morphology and structure of these silver materials. Results All forms of silver inorganic materials could inhibit the growth of all test microorganisms. The MIC of AgZ, AgZrPSi and AgZrP was 10.0 g/L whereas MLC ranged between 10.0–60.0 g/L. In terms of morphology and structure, AgZrPSi and AgZrP had smaller sized particles (1.5–3.0 µm) and more uniformly shaped than AgZ. Conclusions Silver inorganic materials in the form of AgZ, AgZrPSi and AgZrP had antimicrobial effects against all test oral microorganisms and those activities may be influenced by the crystal structure of carriers. These results suggest that these silver materials may be useful metals applied to oral hygiene products to provide antimicrobial activity against oral infection. PMID:23570016

Saengmee-anupharb, Sirikamon; Srikhirin, Toemsak; Thaweboon, Boonyanit; Thaweboon, Sroisiri; Amornsakchai, Taweechai; Dechkunakorn, Surachai; Suddhasthira, Theeralaksna; Kamaguchi, Arihide

2013-01-01

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

Crystalline phase formation in metakaolinite geopolymers activated with NaOH and sodium silicate  

Microsoft Academic Search

The effect of the NaOH content and the presence of sodium silicate activators on the formation of crystalline phases from\\u000a metakaolinite-based geopolymers were studied by X-ray powder diffraction (XRD), Rietveld quantitative XRD, solid-state MAS\\u000a NMR and SEM in samples synthesized with varying NaOH contents and different curing times at 40 °C. Geopolymers activated with\\u000a NaOH alone with Si\\/Na ratios of 4\\/4

Bo Zhang; Kenneth J. D. MacKenzie; Ian W. M. Brown

2009-01-01

33

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

34

Zeolite materials prepared using silicate waste from template synthesis of ordered mesoporous carbon.  

PubMed

Significant amount of silica waste is generated in the preparation of porous carbon materials using template synthesis. Industrial production of such porous carbon not only creates waste chemicals, but also poses significant environmental concerns and high waste treatment cost. Recycling is proposed as the best solution for tackling such chemical wastes. In this study, etched silica waste released from template synthesis of mesoporous carbon is recycled to produce precious functional microporous zeolite materials. The solid silica template is etched out with NaOH solution to produce silica-free mesoporous carbon. The collected silica waste is recycled to generate zeolites such as LTA and MFI type silica materials. The formation of zeolites is confirmed by FT-IR, XRD, (29)Si NMR, (27)Al NMR, and SEM. This straight forward green chemistry route not only recycles the waste chemicals, but also decreases environmental pollution for better improvement of our living. PMID:23792927

Kim, Yun Kyung; Rajesh, Kizhakke Palleeri; Yu, Jong-Sung

2013-09-15

35

Cobalt-containing layered or zeolitic silicates as photocatalysts for hydrogen generation.  

PubMed

Layered magadiite and zeolites Y containing framework Co or small CoO clusters in the pores have been synthesized and tested as photocatalysts for water splitting, in the absence and presence of methanol, upon UV or simulated sunlight irradiation; the best performing material was Co-magadiite. PMID:25314124

Nea?u, ?tefan; Puche, Marta; Fornés, Vicente; Garcia, Hermenegildo

2014-12-01

36

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

37

A vibrational spectroscopic study of the silicate mineral harmotome - (Ba,Na,K)1-2(Si,Al)8O16?6H2O - A natural zeolite  

NASA Astrophysics Data System (ADS)

The mineral harmotome (Ba,Na,K)1-2(Si,Al)8O16?6H2O is a crystalline sodium calcium silicate which has the potential to be used in plaster boards and other industrial applications. It is a natural zeolite with catalytic potential. Raman bands at 1020 and 1102 cm-1 are assigned to the SiO stretching vibrations of three dimensional siloxane units. Raman bands at 428, 470 and 491 cm-1 are assigned to OSiO bending modes. The broad Raman bands at around 699, 728, 768 cm-1 are attributed to water librational modes. Intense Raman bands in the 3100 to 3800 cm-1 spectral range are assigned to OH stretching vibrations of water in harmotome. Infrared spectra are in harmony with the Raman spectra. A sharp infrared band at 3731 cm-1 is assigned to the OH stretching vibration of SiOH units. Raman spectroscopy with complimentary infrared spectroscopy enables the characterization of the silicate mineral harmotome.

Frost, Ray L.; López, Andrés; Wang, Lina; Romano, Antônio Wilson; Scholz, Ricardo

2015-02-01

38

A vibrational spectroscopic study of the silicate mineral harmotome - (Ba,Na,K)1-2(Si,Al)8O16?6H2O - A natural zeolite.  

PubMed

The mineral harmotome (Ba,Na,K)1-2(Si,Al)8O16?6H2O is a crystalline sodium calcium silicate which has the potential to be used in plaster boards and other industrial applications. It is a natural zeolite with catalytic potential. Raman bands at 1020 and 1102cm(-1) are assigned to the SiO stretching vibrations of three dimensional siloxane units. Raman bands at 428, 470 and 491cm(-1) are assigned to OSiO bending modes. The broad Raman bands at around 699, 728, 768cm(-1) are attributed to water librational modes. Intense Raman bands in the 3100 to 3800cm(-1) spectral range are assigned to OH stretching vibrations of water in harmotome. Infrared spectra are in harmony with the Raman spectra. A sharp infrared band at 3731cm(-1) is assigned to the OH stretching vibration of SiOH units. Raman spectroscopy with complimentary infrared spectroscopy enables the characterization of the silicate mineral harmotome. PMID:25203212

Frost, Ray L; López, Andrés; Wang, Lina; Romano, Antônio Wilson; Scholz, Ricardo

2015-02-25

39

The optical constants of crystalline silicate particles in mid- and far-infrared  

NASA Astrophysics Data System (ADS)

The optical constants from the mid to far infrared region are presented for the crystalline silicate particles with submicron size, i.e. olivine, forsterite, clinopyroxene and orthopyroxene particles which are considered as major constituents of interplanetary, interstellar and circumstellar dust. The olivine, clinoproxene and orthopyroxene are natural from Ichinomegata, Akita and have the following characteristics, olivine: (Mg_0.90Fe_0.10)_2SiO_2(Fo_90), rho = 3.36g/cm^3 clinopyroxene: Ca(Mg,Fe,Al)(Si,Al)_2O_6 Mg / (Mg+Fe) = 0.90 - 0.92, Al_2O_3 = 1.9 - 4.9 wt%, rho = 3.28 g/cm^3 orthopyroxene: (Mg,Fe,Al)(Si,Al)O_3 3.36g / cm^3 Mg / (Mg+Fe) = 0.89 - 0.90, Al_2O_3 = 3.3 - 4.0 wt%, rho = 3.32 g/cm^3 The forsterite (Mg_2SiO_4, [Mg / (Mg+Fe) = 1]) is synthesized by the CZ method (Takei 1976). The optical constants have been derived from the transmission spectra of the particles with use of Kramers-Kronig relation (Rouleau and Martin 1991). The transmissions from 5 microns to 30 microns and 25 microns to 100 microns were measured respectively for KBr pellets and polyethylene sheets containing the particles. Under Rayleigh approximation (lambda gg particle size) the imaginary part of the polarizability A per unit volume has a form of A = (epsilon/epsilon_h-1) / ((epsilon/epsilon_h-1)L+1) where epsilon: dielectric constant of particle, epsilon_h: dielectric constant of host medium and L: shape parameter of dust with assumption of homogeneous spheroid. The imaginary part of A is proportional to the transmission T as Aimg = lambda/{(2pi nhost)} rho/M ln (1/T). Imaginary part of A at infrared region are given from our measurements, and with applying Kramers-Kronig relation to the polarizability the real part of A can be derived, then the optical constants of particles are evaluated from equation of A. The silicate's strong absorption features around 10 microns and 11 microns were measured for the particles placed on the surface of KBr or glass plate (not embedded in KBr), in which case the ratios of the absorption depth of the features were found to have little effect of substrate medium, so the ratios obtained in this way should be determined from optical constant of particle itself. The ratios were successfully reproduced with our optical constants by adjusting the shape parameter L where the value L was confirmed to be consistent with the shape of the particles by inspecting their images under microscope.

Suto, Hiroshi; Koike, Chiyoe; Shibai, Hiroshi; Tuchiyama, Akira; Mizutani, Kohei

40

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

41

Review of the thermal stability and cation exchange properties of the zeolite minerals clinoptilolite, mordenite, and analcime; applications to radioactive waste isolation in silicic tuff  

SciTech Connect

Silicic tuffs of the southern Great Basin and basalts of the Columbia River Plateau are under investigation as potential host rocks for high- and intermediate-level radioactive wastes. Nonwelded and partially welded tuffs may contain major amounts (> 50%) of the zeolite minerals clinoptilolite, mordenite, and analcime. Densely welded tuffs and some basalt flows may contain clinoptilolite as fracture filling that limits the permeability of these rocks. The cation exchange properties of these zeolite minerals allow them to pose a formidable natural barrier to the migration of cationic species of various radionuclides in aqueous solutions. However, these minerals are unstable at elevated temperatures and at low water-vapor pressures and may break down either by reversible dehydration or by irreversible mineralogical reactions. All the breakdown reactions occurring at increased temperature involve a net volume reduction and evolution of fluids. Thus, they may provide a pathway (shrinkage fractures) and a driving force (fluid pressure) for release of radionuclides to the biosphere. These reactions may be avoided by keeping zeolite-bearing horizons saturated with water and below about 85{sup 0}C. This may restrict allowable gross thermal loadings in waste repositories in volcanic rocks.

Smyth, J.R.; Caporuscio, F.A.

1981-06-01

42

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

43

Final Report on the Safety Assessment of Aluminum Silicate, Calcium Silicate, Magnesium Aluminum  

E-print Network

Final Report on the Safety Assessment of Aluminum Silicate, Calcium Silicate, Magnesium Aluminum Sodium Silicate, Montmorillonite, Pyrophyllite, and Zeolite1 This report reviews the safety of Aluminum, Calcium, Lithium Magnesium, Lithium Magnesium Sodium, Magnesium Aluminum, Magnesium, Sodium Magnesium

Ahmad, Sajjad

44

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

45

Calcium-aluminum-silicate-hydrate “cement” phases and rare Ca-zeolite association at Colle Fabbri, Central Italy  

Microsoft Academic Search

Very high temperature, Ca-rich alkaline magma intruded an argillite formation at Colle Fabbri, Central Italy, producing cordierite-tridymite\\u000a metamorphism in the country rocks. An intense Ba-rich sulphate-carbonate-alkaline hydrothermal plume produced a zone of mineralization\\u000a several meters thick around the igneous body. Reaction of hydrothermal fluids with country rocks formed calcium-silicate-hydrate\\u000a (CSH), i.e., tobermorite-afwillite-jennite; calcium-aluminum-silicate-hydrate (CASH) — “cement” phases - i.e., thaumasite,

Francesco Stoppa; Fernando Scordari; Ernesto Mesto; Victor V. Sharygin; Giorgio Bortolozzi

2010-01-01

46

Permeability Change of Crystalline Silicate Mineral-Packed Bed Column by Highly Alkaline Plume  

SciTech Connect

For the construction of the geological disposal system, the use of the cementitious material may change the permeability of the natural barrier around the repository. Cementitious materials may alter the pH of ground water to highly alkaline. Also, the potential permeability change of the natural barrier is one of the notable factors for performance assessments of geological disposal systems. In the high pH region, the solubility of silica is very high compared to that in the natural pH (around 8). Therefore, highly alkaline groundwater would dissolve and alter a part of rock surface. Usui et al. (2005) reported that the change of mineral pore structure due to chemical reaction is the key factor to consider the change of the permeability [5-6]. Moreover, such a change of the pore structure was considered to be the result of the spatial heterogeneity of chemical composition. Since such spatial heterogeneity exists also in the sedimentary rocks consisting of crystalline minerals such as quartz and feldspar, we need to examine natural rock, in order to obtain more reliable understanding about the change of permeability induced by highly alkaline groundwater (plume). In this study, silica sand as crystalline mineral was packed in the column, and the effect of dissolution induced by the highly alkaline plume on the permeability-change was examined. The silica sand particles mainly consist of SiO{sub 2} and include Al{sub 2}O{sub 3}, FeO, and K{sub 2}O. The volumetric flow rate and the pressure difference between the inlet and outlet of the column were measured, and the permeability was calculated. At the same time, the concentrations of elements in the fluid were measured by ICP-AES. The experimental result showed that permeability decreased gradually, although the silica sand was continuously dissolved in the column. The behavior of the permeability is considered to be the result from the rearrangement of the particles, or precipitation of secondary mineral. In the column test using the silica sand as packed mineral, the flow-path seems to be clogged by the rearrangement of the particles rather than the increase of the pore space between the particles. (authors)

Hideo Usui; Yuichi Niibori; Hitoshi Mimura [Department of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University, Aramaki Aza Aoba 6-6-01-2, Aoba-ku, Sendai, 980-8579 (Japan); Osamu Tochiyama [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, 980-8577 (Japan)

2007-07-01

47

A simple and general route for the preparation of pure and high crystalline nanosized lanthanide silicates with the structure of apatite at low temperature  

SciTech Connect

Rare earth silicates with the structure of apatite are attracting considerable interest since they show oxygen ion conductivities higher than that of yttria-stabilized zirconia (YSZ) at moderate temperature. Based on the hydrothermal synthesis we presented a simple one step process for the direct preparation of the pure and the high crystalline nanosized rare earth silicates with the structure of apatite under a mild condition (230 {sup o}C). Since the preparation of the high crystalline silicon based rare earth apatites is performed at high temperature previously and accompanied by subsequent process of grinding, results of this work provide a promising alternative of the existing methodology. Furthermore, due to the relatively low temperature of the preparation of these materials, high doping of monovalent cation can be done, which was not achieved before. -- Graphical abstract: A simple one step process for the preparation of the rare earth silicates with the structure of apatite under a mild condition (230 {sup o}C) is presented. The process is based on the hydrothermal synthesis and the obtained powder materials are pure, high crystalline and with nanosize. Display Omitted

Ferdov, Stanislav [Department of Chemistry, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Department of Physics, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Department of Physics, University of Minho, 4800-058 Guimaraes (Portugal); Rauwel, Protima [Department of Ceramic and Glass Engineering, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Lin, Zhi, E-mail: zlin@ua.p [Department of Chemistry, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Ferreira, Rute A. Sa [Department of Physics, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Lopes, Augusto [Department of Ceramic and Glass Engineering, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal)

2010-11-15

48

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

49

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

50

IRAS 15099-5856: REMARKABLE MID-INFRARED SOURCE WITH PROMINENT CRYSTALLINE SILICATE EMISSION EMBEDDED IN THE SUPERNOVA REMNANT MSH15-52  

SciTech Connect

We report new mid-infrared (MIR) observations of the remarkable object IRAS 15099-5856 using the space telescopes AKARI and Spitzer, which demonstrate the presence of prominent crystalline silicate emission in this bright source. IRAS 15099-5856 has a complex morphology with a bright central compact source (IRS1) surrounded by knots, spurs, and several extended ({approx}4') arc-like filaments. The source is seen only at {>=}10 {mu}m. The Spitzer mid-infrared spectrum of IRS1 shows prominent emission features from Mg-rich crystalline silicates, strong [Ne II] 12.81 {mu}m, and several other faint ionic lines. We model the MIR spectrum as thermal emission from dust and compare with the Herbig Be star HD 100546 and the luminous blue variable R71, which show very similar MIR spectra. Molecular line observations reveal two molecular clouds around the source, but no associated dense molecular cores. We suggest that IRS1 is heated by UV radiation from the adjacent O star Muzzio 10 and that its crystalline silicates most likely originated in a mass outflow from the progenitor of the supernova remnant (SNR) MSH 15-52. IRS1, which is embedded in the SNR, could have been shielded from the SN blast wave if the progenitor was in a close binary system with Muzzio 10. If MSH 15-52 is a remnant of Type Ib/c supernova (SN Ib/c), as has been previously proposed, this would confirm the binary model for SN Ib/c. IRS1 and the associated structures may be the relics of massive star death, as shaped by the supernova explosion, the pulsar wind, and the intense ionizing radiation of the embedded O star.

Koo, Bon-Chul; Kim, Hyun-Jeong; Im, Myungshin [Department of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of); McKee, Christopher F. [Department of Physics and Astronomy, University of California, Berkeley, CA 94720 (United States); Suh, Kyung-Won [Department of Astronomy and Space Science, Chungbuk National University, Cheingju-City 361-763 (Korea, Republic of); Moon, Dae-Sik; Lee, Ho-Gyu [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada); Onaka, Takashi [Department of Astronomy, University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Burton, Michael G. [School of Physics, University of New South Wales, Sydney, New South Wales 2052 (Australia); Hiramatsu, Masaaki [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China); Bessell, Michael S. [Research School of Astronomy and Astrophysics, Mount Stromlo Observatory (Australia); Gaensler, B. M. [Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006 (Australia); Lee, Jae-Joon [Astronomy and Astrophysics Department, Pennsylvania State University, University Park, PA 16802 (United States); Jeong, Woong-Seob [Korea Astronomy and Space Science Institute, 61-1, Whaam-dong, Yuseong-gu, Daejeon 305-348 (Korea, Republic of); Tatematsu, Ken'ichi; Kawabe, Ryohei; Ezawa, Hajime [National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo 181-8588 (Japan); Kohno, Kotaro [Institute of Astronomy, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Wilson, Grant; Yun, Min S., E-mail: koo@astrohi.snu.ac.kr [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States)

2011-05-01

51

A vibrational spectroscopic study of the silicate mineral analcime - Na2(Al4SiO4O12)·2H2O - A natural zeolite  

NASA Astrophysics Data System (ADS)

We have studied the mineral analcime using a combination of scanning electron microscopy with energy dispersive spectroscopy and vibrational spectroscopy. The mineral analcime Na2(Al4SiO4O12)·2H2O is a crystalline sodium silicate. Chemical analysis shows the mineral contains a range of elements including Na, Al, Fe2+ and Si. The mineral is characterized by intense Raman bands observed at 1052, 1096 and 1125 cm-1. The infrared bands are broad; nevertheless bands may be resolved at 1006 and 1119 cm-1. These bands are assigned to SiO stretching vibrational modes. Intense Raman band at 484 cm-1 is attributed to OSiO bending modes. Raman bands observed at 2501, 3542, 3558 and 3600 cm-1 are assigned to the stretching vibrations of water. Low intensity infrared bands are noted at 3373, 3529 and 3608 cm-1. The observation of multiple water bands indicate that water is involved in the structure of analcime with differing hydrogen bond strengths. This concept is supported by the number of bands in the water bending region. Vibrational spectroscopy assists with the characterization of the mineral analcime.

Frost, Ray L.; López, Andrés; Theiss, Frederick L.; Romano, Antônio Wilson; Scholz, Ricardo

2014-12-01

52

Cesium titanium silicate and method of making  

DOEpatents

The invention is the new material, a ternary compound of cesium, silica, and titania, together with a method of making the ternary compound, cesium titanium silicate pollucite. More specifically, the invention is Cs.sub.2 Ti.sub.2 Si.sub.4 O.sub.13 pollucite which is a new crystalline phase representing a novel class of Ti-containing zeolites. Compositions contain relatively high Cs.sub.2 O and TiO.sub.2 loadings and are durable glass and ceramic materials. The amount of TiO.sub.2 and Cs.sub.2 that can be incorporated into these glasses and crystalline ceramics far exceeds the limits set for the borosilicate high level waste glass.

Balmer, Mari L. (West Richland, WA)

1997-01-01

53

Cesium titanium silicate and method of making  

DOEpatents

The invention is the new material, a ternary compound of cesium, silica, and titania, together with a method of making the ternary compound, cesium titanium silicate pollucite. More specifically, the invention is Cs{sub 2}Ti{sub 2}Si{sub 4}O{sub 13} pollucite which is a new crystalline phase representing a novel class of Ti-containing zeolites. Compositions contain relatively high Cs{sub 2}O and TiO{sub 2} loadings and are durable glass and ceramic materials. The amount of TiO{sub 2} and Cs{sub 2} that can be incorporated into these glasses and crystalline ceramics far exceeds the limits set for the borosilicate high level waste glass. 10 figs.

Balmer, M.L.

1997-01-07

54

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

55

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

56

Thermal desorption characteristics of CO, O2 and CO2 on non-porous water, crystalline water and silicate surfaces at sub-monolayer and multilayer coverages  

E-print Network

The desorption characteristics of molecules on interstellar dust grains are important for modelling the behaviour of molecules in icy mantles and, critically, in describing the solid-gas interface. In this study, a series of laboratory experiments exploring the desorption of three small molecules from three astrophysically relevant surfaces are presented. The desorption of CO, O2 and CO2 at both sub-monolayer and multilayer coverages was investigated from non-porous water, crystalline water and silicate surfaces. Experimental data was modelled using the Polanyi-Wigner equation to produce a mathematical description of the desorption of each molecular species from each type of surface, uniquely describing both the monolayer and multilayer desorption in a single combined model. The implications of desorption behaviour over astrophysically relevant timescales are discussed.

Noble, J A; Dulieu, F; Fraser, H J

2011-01-01

57

Radiation effects and annealing kinetics in crystalline silicates, phosphates and complex Nb-Ta-Ti oxides. FInal Report  

SciTech Connect

Interaction of heavy particles (alpha-recoil nuclei, fission fragments, implanted ions) with ceramics is complex because they have a wide range of structure types, complex compositions and chemical bonding is variable. Radiation damage can produce diverse results, but most commonly, crystalline periodic materials become either polycrystalline or aperiodic (metamict state). We studied the transition from crystalline to aperiodic state in natural materials that have been damaged by alpha recoil nuclei in the U and Th decay series and in synthetic, analogous structure types which have been amorphized by ion implantation. Transition from crystalline to aperiodic was followed by analysis of XRD, high resolution TEM, and EXAFS/XANE spectroscopy. Use of these techniques with increasing dose provided data on an increasing finer scale as the damage process progressed.

Ewing, R.C.

1987-08-10

58

Lack of Evidence of In-Situ Decay of Aluminum-26 in a FeO-Poor Ferromagnesian Crystalline Silicate Particle, Pyxie, from Comet Wild 2  

NASA Technical Reports Server (NTRS)

One of the important discoveries from the Stardust mission is the observation of crystalline silicate particles that resemble Ca, Al-rich inclusions (CAIs) and chondrules in carbonaceous chondrites], which suggests radial transport of high temperature solids from the inner to the outer solar nebula regions and capture by accreting cometary objects. The Al-Mg isotope analyses of CAI-like and type II chondrule-like particles revealed no excess of Mg-26 derived from in-situ decay of Al-26 (Tau)(sub 1/2) = 0.705Myr; ), suggesting late formation of these particles. However, the number of Wild 2 particles analyzed for Al-Mg isotopes is still limited (n = 3). In order to better understand the timing of the formation of Wild 2 particles and possible radial transport in the protoplanetary disk, we performed SIMS (Secondary Ion Mass Spectrometer) Al-Mg isotope analyses of plagioclase in a FeO-poor ferromagnesian Wild 2 particle, which is the most abundant type among crystalline Wild 2 particles.

Nakashima, D.; Ushikubo, T.; Weisberg, M. K.; Zolensky, M. E.; Ebel, D. S.; Kita, N. T.

2014-01-01

59

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

60

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

61

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

62

CO gas sensor based on Au-La{sub 2}O{sub 3} added SnO{sub 2} ceramic with siliceous zeolite coat  

SciTech Connect

Conventional CO gas sensors have poor selectivity to ethanol vapor, which coexists very often in kitchens, causing false alarms; and adsorbents (e.g., active carbon) of ethanol vapor has always been used. In order to depress alcohol sensitivity in these sensors and thusly improve CO measurement, the authors studied the effects of adding lanthanum oxide to the sensor matrix to increase sensitivity and silaceous zeolite to catalytically remove ethanol vapor through dehydration.

Fukui, Kiyoshi; Nishida, Sachiko [New Cosmos Electric Co., Ltd. Osaka (Japan)

1996-12-31

63

Crystallinity-vesicularity interrelation in silicic pyroclasts - Neutron and X-Ray Computed Tomography constraints on magma permeability  

NASA Astrophysics Data System (ADS)

The permeability of magma controls gas escape during magma ascent and thus may control eruption behaviour, varying from quiet degassing to explosive fragmentation (Mueller et al., 2008). Yet, the spatial distribution of connected vs. isolated vesicle structures in magma remains poorly constrained. Additionally, the crystal distribution may influence magma permeability: a) do fractures in crystals provide additional pathways to melt-based volatile migration? and b) do low surface-tension crystal faces catalyse bubble nucleation and growth? In felsic pyroclasts, the size, shape and interconnectivity of vesicles and phenocrysts have been quantified by 3D tomography. We applied high resolution neutron computed tomography (NCT) at 20 ?m and X-ray Computed Tomography (XCT) at 5-10 ?m resolution on large samples of 15-50 cm3 to investigate the 3D structure of vesicular (? = 0.45-0.72), silica-rich pyroclastic material from various explosive eruptions. Samples are of the 2004 vulcanian and the 1783 plinian eruption of Asama (Japan), the 1997 eruption of Soufrière Hills Volcano (Montserrat) and the June 1991 vulcanian event of Unzen (Japan). Volume reconstructions of the pore space and different crystal phases were calculated with Tomoview, our custom-made software. The reconstructed volumes showed an interrelation between vesicle and crystal distribution. Differential overlapping of crystal and vesicle subvolumes trace the crystal outlines exceptionally well. Furthermore, Tomoview detected connected pathways that frequently exploited inter-fracture space of fragmented crystals. Crystal fragmentation thus appears to provide an additional mechanism for generating pore space. The evolution of a permeable network may thus be affected by the crystal content, which ultimately biases the eruptive behaviour of silicic magma.

Wiesmaier, S.; Scheu, B.; Hess, K.-U.; Schillinger, B.; Flaws, A.; Dingwell, D. B.

2012-04-01

64

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

65

Crystallinity-vesicularity interrelation in silicic pyroclasts - Implications for permeability as inferred from Neutron and X-Ray Computed Tomography  

NASA Astrophysics Data System (ADS)

The permeability of magma controls gas escape during magma ascent and thus may trigger shifts in eruption behaviour from quiet degassing towards explosive fragmentation (Mueller et al., 2008). Yet, the spatial distribution of connected vs. isolated vesicle structures in magma remains poorly constrained. Additionally, the role of the crystal distribution can be expected to influence magma permeability: a) fractures in crystals may provide additional pathways to melt-based volatile migration, and b) low surface tension crystal faces may act as catalyst to bubble nucleation and growth. In felsic pyroclasts, the highly variable size, shape and interconnectivity of vesicles and phenocrysts results in a complex structure, best quantified by 3D tomography. We applied high resolution neutron computed tomography (NCT; 50 ?m pixel/voxel-size) to investigate the 3D structure of vesicular (? = 0.45-0.72), silica-rich pyroclastic material from various explosive eruptions. Samples are of the 2004 vulcanian and the 1783 plinian eruption of Asama (Japan), the 1997 eruption of Soufrière Hills Volcano (Montserrat) and the June 1991 vulcanian event of Unzen (Japan). For large samples (15-50 cm3), Neutron Computed Tomography provides the first non-destructive method to analyse this complex 3D structure. The NCT experiments were performed at the ANTARES beamline of the neutron source at the reactor FRM II at Technische Universität München (Germany). X-ray Computed Tomography (XCT) at 5-10 ?m resolution was performed at IMETUM (Germany) to scrutinize features of one order of magnitude smaller than NCT. Our custom-made software Tomoview permits interpolated slicing and thus a voxel-to-voxel comparison of both XCT and NCT datasets. This allows for differential datasets of hydrous versus non-hydrous phases and their relation to the fabric. Volume reconstructions of the pore space and different crystal phases were calculated with Tomoview. The reconstructed volumes showed an interrelation between vesicle and crystal distribution, as well influencing the formation of connected pathways. Furthermore, crystal fragmentation appears to provide an additional mechanism for generating pore space. The evolution of a permeable network may thus be affected by the crystal content, which ultimately biases the eruptive behaviour of silicic magma.

Wiesmaier, S.; Scheu, B.; Hess, K.; Mühlbauer, M.; Schillinger, B.; Flaws, A.; Dingwell, D. B.

2011-12-01

66

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

67

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

68

Synthesis of hierarchical micro/mesoporous structures via solid-aqueous interface growth: zeolitic imidazolate framework-8 on siliceous mesocellular foams for enhanced pervaporation of water/ethanol mixtures.  

PubMed

A new hierarchical micro/mesoporous composite is synthesized via direct growth of microporous zeolitic imidazolate framework-8 (ZIF-8) on siliceous mesocellular foams (MCF). Depending on different synthetic conditions, ZIF-8 with two different particle sizes, i.e., ZIF-8 microparticles and ZIF-8 nanoparticles, were successfully formed on the external surface of amine-functionalized MCF (denoted as microZIF-8@MCF and nanoZIF-8@MCF, respectively). The synthesized hierarchical micro/mesoporous ZIF-8@MCF structures were characterized with several spectroscopic techniques including X-ray diffraction (XRD), solid-state NMR, and FT-IR and electron microscopic techniques (scanning electron microscope, SEM, and transmission electron microscopy, TEM). In addition, the pervaporation measurements of the liquid water/ethanol mixture show that nanoZIF-8@MCF/PVA (poly(vinyl alcohol) mixed-matrix membrane exhibits enhanced performance both on the permeability and separation factor. Compared to conventional routes for chemical etching, this study demonstrates a promising and simple strategy for synthesizing novel hierarchical porous composites exhibiting both advantages of mesoporous materials and microporous materials, which is expected to be useful for gas adsorption, separation, and catalysis. PMID:24625412

Sue, Yu-Chain; Wu, Jhe-Wei; Chung, Shao-En; Kang, Chao-Hsiang; Tung, Kuo-Lun; Wu, Kevin C-W; Shieh, Fa-Kuen

2014-04-01

69

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

70

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

71

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

72

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

73

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

74

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

75

Silicate emission in Orion  

E-print Network

We present mid-infrared spectro-imagery and high-resolution spectroscopy of the Orion bar and of a region in the Orion nebula. These observations have been obtained in the Guaranteed Time with the Circular Variable Filters of the ISO camera (CAM-CVF) and with the Short Wavelength Spectrometer (SWS), on board the European Infrared Space Observatory (ISO). Our data shows emission from amorphous silicate grains from the entire HII region and around the isolated O9.5V star Theta2 Ori A. The observed spectra can be reproduced by a mixture of interstellar silicate and carbon grains heated by the radiation of the hot stars present in the region. Crystalline silicates are also observed in the Orion nebula and suspected around Theta2 Ori A. They are probably of interstellar origin. The ionization structure and the distribution of the carriers of the Aromatic Infrared Bands (AIBs) are briefly discussed on the basis of the ISO observations.

D. Cesarsky; A. P. Jones; J. Lequeux; L. Verstraete

2000-02-14

76

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

77

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

78

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

79

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

80

Environmental Applications of Natural Zeolitic Materials Based on Their Ion Exchange Properties  

Microsoft Academic Search

\\u000a Present and potential use of natural zeolites as cation exchangers in environmental protection is reviewed. Siliceous zeolites,\\u000a such as chabazite, clinoptilolite, mordenite and phillipsite, exhibit good selectivities for cations with low charge density,\\u000a e.g., Cs+ and NH4\\u000a +, and for cations with low hydration energy, such as Pb2+. Zeolitised tuffs, containing the mentioned zeolites, may therefore be utilised for removing

C. Colella; Piazza Ie; V. Tecchio

81

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

82

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

83

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

84

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

85

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

86

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.

87

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

88

Silicate absorption in heavily obscured galaxy nuclei  

E-print Network

Spectroscopy at 8-13 microns with T-ReCS on Gemini-S is presented for 3 galaxies with substantial silicate absorption features, NGC 3094, NGC 7172 and NGC 5506. In the galaxies with the deepest absorption bands, the silicate profile towards the nuclei is well represented by the emissivity function derived from the circumstellar emission from the red supergiant, mu Cephei which is also representative of the mid-infrared absorption in the diffuse interstellar medium in the Galaxy. There is spectral structure near 11.2 microns in NGC 3094 which may be due to a component of crystalline silicates. In NGC 5506, the depth of the silicate absorption increases from north to south across the nucleus, suggestive of a dusty structure on scales of 10s of parsecs. We discuss the profile of the silicate absorption band towards galaxy nuclei and the relationship between the 9.7 micron silicate and 3.4 micron hydrocarbon absorption bands.

P. F. Roche; C. Packham; D. K. Aitken; R. E. Mason

2006-10-19

89

Geopolymer synthesis using alkaline activation of natural zeolite  

Microsoft Academic Search

The influence of activator ratio, time, and curing temperature on the mechanical strength of geopolymers synthesized from natural zeolite was evaluated by employing silicate solutions and sodium hydroxide. The results demonstrated that an increase in the activator ratio as well as that of curing time favors mechanical strength in the material. Nevertheless, with 90day of curing time and 80°C or

C. Villa; E. T. Pecina; R. Torres; L. Gómez

2010-01-01

90

Ammonium removal from wastewaters using natural New Zealand zeolites  

Microsoft Academic Search

Ammoniacal nitrogen (ammonia and ammonium) in agricultural wastewaters can promote eutrophication of receiving waters and be potentially toxic to fish and other aquatic life. Zeolites, which are hydrated aluminum?silicate minerals, have an affinity for ammonium ions (NH4 ) and are, therefore, potentially useful in removing this contaminant from wastewaters. The major objectives of this study were to evaluate the capacity

M. L. Nguyen; C. C. Tanner

1998-01-01

91

A new crystallization mechanism of cometary silicate grains  

NASA Astrophysics Data System (ADS)

Since the first identification of crystalline silicate feature in comet Halley in the wavelength region of 8 to 13 ?m (Bregman et al. 1987, A&A, 187, 616; Campins and Ryan, ApJ, 341, 1059), similar crystalline silcate features have been clearly observed in a number of comets (see the review by Hanner 1999, Space Science Rev. 90, 99). The crystalline silicate features have also been observed in various kinds of objects including circumstellar dust around evolved stars, in YSOs at a late stage, and in disks aroung young main sequance stars such as ?-Pic. On the other hand, the crystalline feature has not been observed in the dust in diffuse interstellar medium and molecular clouds. The origin of cometary crystalline silicates is not clear. It has been considered that cometary silicates are a mixture of crystalline and amorphous silicates, where former were formed by annealing of amorphous silicates or direct condensation in a hot (> 1000 K) region of the primordial solar nebula and the latter is interstellar grains preserved together with their icy component in the cold region of the solar nebula. We propose a new mechanism of crystallization of cometary silicate grains based on the Greenberg model of cometary dust, which is composed of a silicate core, an organic mantle, and an outermost icy mantle. The mechanism that we propose is crystallization due to energy release by chemical reactions of reactive molecules in the organic mantle when the grains released from a cometary nucleus are heated by solar radiation. We formulate the crystallization mechanism and calculate the degree of crystallinity of the silicate core. It is shown that the present mechanism will work and can reproduce the observed infrared spectra of the cometary crystalline silicate feature.

Yamamoto, T.; Chigai, T.

92

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.

93

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

94

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

95

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.

96

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

97

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

98

Biological and therapeutic effects of ortho-silicic acid and some ortho-silicic acid-releasing compounds: New perspectives for therapy  

PubMed Central

Silicon (Si) is the most abundant element present in the Earth's crust besides oxygen. However, the exact biological roles of silicon remain unknown. Moreover, the ortho-silicic acid (H4SiO4), as a major form of bioavailable silicon for both humans and animals, has not been given adequate attention so far. Silicon has already been associated with bone mineralization, collagen synthesis, skin, hair and nails health atherosclerosis, Alzheimer disease, immune system enhancement, and with some other disorders or pharmacological effects. Beside the ortho-silicic acid and its stabilized formulations such as choline chloride-stabilized ortho-silicic acid and sodium or potassium silicates (e.g. M2SiO3; M= Na,K), the most important sources that release ortho-silicic acid as a bioavailable form of silicon are: colloidal silicic acid (hydrated silica gel), silica gel (amorphous silicon dioxide), and zeolites. Although all these compounds are characterized by substantial water insolubility, they release small, but significant, equilibrium concentration of ortho-silicic acid (H4SiO4) in contact with water and physiological fluids. Even though certain pharmacological effects of these compounds might be attributed to specific structural characteristics that result in profound adsorption and absorption properties, they all exhibit similar pharmacological profiles readily comparable to ortho-silicic acid effects. The most unusual ortho-silicic acid-releasing agents are certain types of zeolites, a class of aluminosilicates with well described ion(cation)-exchange properties. Numerous biological activities of some types of zeolites documented so far might probably be attributable to the ortho-silicic acid-releasing property. In this review, we therefore discuss biological and potential therapeutic effects of ortho-silicic acid and ortho-silicic acid -releasing silicon compounds as its major natural sources. PMID:23298332

2013-01-01

99

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

100

Effect of reaction mixture composition and silica source on size distribution of zeolite X crystals  

NASA Astrophysics Data System (ADS)

Zeolite X crystals were synthesized by hydrothermal crystallization from gels with different compositions. The syntheses were performed at 95 °C using different silica sources such as sodium metasilicate anhydrous, sodium metasilicate pentahydrate, silicate solution and Cab-O-Sil. Triethanolamine was used in some syntheses in order to grow large crystals. Zeolite X crystals with diameters in the range of 1-220 ?m were obtained, and Cab-O-Sil in concert with triethanolamine yielded the largest crystals.

Tekin, Rumeysa; Bac, Nurcan; Warzywoda, Juliusz; Sacco, Albert

2015-02-01

101

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

102

EFFECT OF QUARTZ/MULLITE BLEND CERAMIC ADDITIVE ON IMPROVING RESISTANCE TO ACID OF SODIUM SILICATE-ACTIVATED SLAG CEMENT. CELCIUS BRINE.  

SciTech Connect

We evaluated the usefulness of manufactured quartz/mullite blend (MQMB) ceramic powder in increasing the resistance to acid of sodium silicate-activated slag (SSAS) cementitious material for geothermal wells. A 15-day exposure to 90{sup o} CO{sub 2}-laden H{sub 2}SO{sub 4} revealed that the MQMB had high potential as an acid-resistant additive for SSAS cement. Two factors, the appropriate ratio of slag/MQMB and the autoclave temperature, contributed to better performance of MQMB-modified SSAS cement in abating its acid erosion. The most effective slag/MQMB ratio in minimizing the loss in weight by acid erosion was 70/30 by weight. For autoclave temperature, the loss in weight of 100 C autoclaved cement was a less than 2%, but at 300 C it was even lower. Before exposure to acid, the cement autoclaved at 100 C was essentially amorphous; increasing the temperature to 200 C led to the formation of crystalline analcime in the zeolitic mineral family during reactions between the mullite in MQMB and the Na from sodium silicate. In addition, at 300 C, crystal of calcium silicate hydrate (1) (CSH) was generated in reactions between the quartz in MQMB and the activated slag. These two crystalline phases (CSH and analcime) were responsible for densifying the autoclaved cement, conveying improved compressive strength and minimizing water permeability. The CSH was susceptible to reactions with H{sub 2}SO{sub 4}, forming two corrosion products, bassanite and ionized monosilicic acid. However, the uptake of ionized monosilicic acid by Mg dissociated from the activated slag resulted in the formation of lizardite as magnesium silicate hydrate. On the other hand, the analcime was barely susceptible to acid if at all. Thus, the excellent acid resistance of MQMB-modified SSAS cement was due to the combined phases of lizardite and analcime.

SUGAMA, T.; BROTHERS, L.E.; VAN DE PUTTE, T.R.

2006-06-01

103

Interpreting the 10 micron Astronomical Silicate Feature  

NASA Astrophysics Data System (ADS)

10micron spectra of silicate dust in the diffuse medium towards Cyg OB2 no. 12 and towards field and embedded objects in the Taurus Molecular Cloud (TMC) were obtained with CGS3 at the United Kingdom Infrared Telescope (UKIRT). Cold molecular-cloud silicates are sampled in quiescent lines of sight towards the field stars Taurus-Elias 16 and Elias 13, whilst observations of the embedded young stellar objects HL Tau, Taurus-Elias 7 (Haro6-10) and Elias 18 also include emission from heated dust. To obtain the foreground silicate absorption profiles, featureless continua are estimated using smoothed astronomical and laboratory silicate emissivities. TMC field stars and Cyg OB2 no. 12 are modelled as photospheres reddened by foreground continuum and silicate extinction. Dust emission in the non-photospheric continua of HL Tau and Elias 7 (Haro6-10) is distinguished from foreground silicate absorption using a 10micron disk model, based on the IR-submm model of T Tauri stars by Adams, Lada & Shu (1988), with terms added to represent the foreground continuum and silicate extinction. The absorption profiles of HL Tau and Elias 7 are similar to that of the field star Elias 16. Fitted temperature indices of 0.43 (HL Tau) and 0.33 (Elias 7) agree with Boss' (1996) theoretical models of the 200-300K region, but are lower than those of IR-submm disks (0.5-0.61; Mannings & Emerson 1994); the modelled 10micron emission of HL Tau is optically thin, that of Elias 7 is optically thick. A preliminary arcsecond-resolution determination of the 10micron emissivity near ?1 Ori D in the Trapezium region of Orion and a range of emission temperatures (225-310K) are derived from observations by T. L. Hayward; this Ney-Allen emissivity is 0.6micron narrower than the Trapezium emissivity obtained by Forrest et al. (1975) with a large aperture. Published interstellar grain models, elemental abundances and laboratory studies of Solar System silicates (IDPs, GEMS and meteorites), the 10micron spectra of comets, interstellar silicates, synthetic silicates and terrestrial minerals, and the effects of laboratory processing on the 10micron spectra of crystalline and amorphous silicates are reviewed to provide insight into the mineralogy of interstellar silicate dust. The wavelengths of the peaks of the 10micron silicate profiles decrease between circumstellar, diffuse medium and molecular-cloud environments, indicating (after Gürtler & Henning 1986) that the amorphous pyroxene content of initially olivine-rich interstellar dust increases with time. This is accompanied by an increase in the FWHM of the features which indicates an increase in grain size and/or an increasing fraction of chemically-varied crystalline pyroxene. Fine structure in the Cyg OB2 no. 12, Elias 16, Elias 7, HL Tau profiles indicate that hydrated layer silicates similar to terrestrial serpentines, clays and talc may be a ubiquitous component of interstellar dust. At 10microns the narrow bands of mixed crystalline pyroxenes blend, making their identification difficult. Since no fine structure is observed near 11.2microns, the fraction of crystalline olivine is small. In geology direct olivine-plus-SiO2 to pyroxene reactions occur only at high pressure within the terrestrial mantle. Therefore the fraction of amorphous pyroxene is probably increased by the hydration of Mg-rich olivine to form a serpentine-like hydrated silicate, which is subsequently annealed to form a mixture of amorphous pyroxene and olivine. Terrestrial and laboratory olivine samples are readily converted to serpentine in the presence of water, and (after extended annealing) the first crystalline band to appear is the 11.2micron olivine feature frequently observed in cometary spectra.

Bowey, Janet E.

1998-11-01

104

Antimicrobial properties of zeolite-X and zeolite-A ion-exchanged with silver, copper, and zinc against a broad range of microorganisms.  

PubMed

Zeolites are nanoporous alumina silicates composed of silicon, aluminum, and oxygen in a framework with cations, water within pores. Their cation contents can be exchanged with monovalent or divalent ions. In the present study, the antimicrobial (antibacterial, anticandidal, and antifungal) properties of zeolite type X and A, with different Al/Si ratio, ion exchanged with Ag(+), Zn(2+), and Cu(2+) ions were investigated individually. The study presents the synthesis and manufacture of four different zeolite types characterized by scanning electron microscopy and X-ray diffraction. The ion loading capacity of the zeolites was examined and compared with the antimicrobial characteristics against a broad range of microorganisms including bacteria, yeast, and mold. It was observed that Ag(+) ion-loaded zeolites exhibited more antibacterial activity with respect to other metal ion-embedded zeolite samples. The results clearly support that various synthetic zeolites can be ion exchanged with Ag(+), Zn(2+), and Cu(2+) ions to acquire antimicrobial properties or ion-releasing characteristics to provide prolonged or stronger activity. The current study suggested that zeolite formulations could be combined with various materials used in manufacturing medical devices, surfaces, textiles, or household items where antimicrobial properties are required. PMID:24242073

Demirci, Selami; Ustao?lu, Zeynep; Y?lmazer, Gonca Alt?n; Sahin, Fikrettin; Baç, Nurcan

2014-02-01

105

Thermodynamics of rock forming crystalline solutions  

NASA Technical Reports Server (NTRS)

Analysis of phase diagrams and cation distributions within crystalline solutions as means of obtaining thermodynamic data on rock forming crystalline solutions is discussed along with some aspects of partitioning of elements in coexisting phases. Crystalline solutions, components in a silicate mineral, and chemical potentials of these components were defined. Examples were given for calculating thermodynamic mixing functions in the CaW04-SrW04, olivine-chloride solution, and orthopyroxene systems.

Saxena, S. K.

1971-01-01

106

Safe trapping of Cs in heat-treated zeolite matrices  

NASA Astrophysics Data System (ADS)

Cesium retention performances of two different natural zeolites (an Italian phillipsite-rich tuff and a Mexican erionite-rich tuff), pre-exchanged in Cs form and heat-treated, are compared. After thermal treatment at 1000 °C both zeolites satisfactorily retain Cs during back-exchange tests with NaCl solution or by a prolonged contact with distilled water. The different mechanisms of Cs encapsulation are elucidated. The Cs-exchanged phillipsite, a less siliceous and less heat-stable zeolite, tends to form pollucite on heating. Pollucite is a naturally occurring mineral phase which contains and irreversibly traps cesium. The Cs-exchanged erionite tends to form an amorphous phase on heating and Cs is immobilized through glass formation.

Bosch, P.; Caputo, D.; Liguori, B.; Colella, C.

2004-01-01

107

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

108

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

109

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

110

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

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.

2014-08-19

112

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

113

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

114

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

115

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

116

The importance of zeolites in the potential high-level radioactive waste repository at Yucca Mountain, Nevada  

SciTech Connect

Zeolitic rocks play an important role in retarding the migration of radionuclides that occur in solution as simple cations (Cs, Sr, Ba). However, the interaction of zeolites with complex transuranic species in solution provides little if any advantage over other common silicate minerals. The most important consequences of zeolite occurrences near a high-level radioactive waste repository environment are likely to be their response to thermal loading and their impact on site hydrology. Partial zeolite dehydration during the early thermal pulse from the repository and rehydration as the repository slowly cools can have an important impact on the water budget of a repository in unsaturated rocks, provided that the long-term heating does not result in zeolite destabilization.

Vaniman, D.T.; Bish, D.L.

1993-07-01

117

SILICATE EVOLUTION IN BROWN DWARF DISKS  

SciTech Connect

We present a compositional analysis of the 10 {mu}m silicate spectra for brown dwarf disks in the Taurus and Upper Scorpius (UppSco) star-forming regions, using archival Spitzer/Infrared Spectrograph observations. A variety in the silicate features is observed, ranging from a narrow profile with a peak at 9.8 {mu}m, to nearly flat, low-contrast features. For most objects, we find nearly equal fractions for the large-grain and crystalline mass fractions, indicating both processes to be active in these disks. The median crystalline mass fraction for the Taurus brown dwarfs is found to be 20%, a factor of {approx}2 higher than the median reported for the higher mass stars in Taurus. The large-grain mass fractions are found to increase with an increasing strength in the X-ray emission, while the opposite trend is observed for the crystalline mass fractions. A small 5% of the Taurus brown dwarfs are still found to be dominated by pristine interstellar medium-like dust, with an amorphous submicron grain mass fraction of {approx}87%. For 15% of the objects, we find a negligible large-grain mass fraction, but a >60% small amorphous silicate fraction. These may be the cases where substantial grain growth and dust sedimentation have occurred in the disks, resulting in a high fraction of amorphous submicron grains in the disk surface. Among the UppSco brown dwarfs, only usd161939 has a signal-to-noise ratio high enough to properly model its silicate spectrum. We find a 74% small amorphous grain and a {approx}26% crystalline mass fraction for this object.

Riaz, B. [Instituto de Astrofisica de Canarias, E38205 La Laguna, Tenerife (Spain)], E-mail: basmah@iac.es

2009-08-10

118

Energetic Processing of Interstellar Silicate Grains by Cosmic Rays  

SciTech Connect

While a significant fraction of silicate dust in stellar winds has a crystalline structure, in the interstellar medium nearly all of it is amorphous. One possible explanation for this observation is the amorphization of crystalline silicates by relatively 'low' energy, heavy ion cosmic rays. Here we present the results of multiple laboratory experiments showing that single-crystal synthetic forsterite (Mg{sub 2}SiO{sub 4}) amorphizes when irradiated by 10 MeV Xe{sup ++} ions at large enough fluences. Using modeling, we extrapolate these results to show that 0.1-5.0 GeV heavy ion cosmic rays can rapidly ({approx}70 Million yrs) amorphize crystalline silicate grains ejected by stars into the interstellar medium.

Bringa, E M; Kucheyev, S O; Loeffler, M J; Baragiola, R A; Tielens, A G Q M; Dai, Z R; Graham, G; Bajt, S; Bradley, J; Dukes, C A; Felter, T E; Torres, D F; van Breugel, W

2007-03-28

119

Mg/Fe FRACTIONATION IN CIRCUMSTELLAR SILICATE DUST INVOLVED IN CRYSTALLIZATION  

SciTech Connect

Infrared astronomical observations of oxygen-rich young and evolved stars show that only magnesium-rich crystalline silicates exist in circumstellar regions, and iron, one of the most important dust-forming elements, is extremely depleted. The compositional characteristic of circumstellar crystalline silicates is fundamentally different from that of primitive extraterrestrial materials in our solar system, such as chondritic meteorites and interplanetary dust particles. Amorphous silicates are ubiquitous and abundant in space, and are a promising carrier of iron. However, since the first detection of crystalline silicates, there has been an unsolved inconsistency due to differing compositions of coexisting crystalline and amorphous phases, considering that amorphous silicates have been expected to be precursors of these crystals. Here we show the first experimental evidence that Fe-depleted olivine can be formed by crystallization via thermal heating of FeO-bearing amorphous silicates under subsolidus conditions. Mg/Fe fractionation involved in crystallization makes possible to coexist Mg-rich crystalline silicates with Fe-bearing amorphous silicates around stars.

Murata, K.; Takakura, T.; Chihara, H.; Koike, C.; Tsuchiyama, A. [Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan)], E-mail: keisuke@astroboy.ess.sci.osaka-u.ac.jp

2009-05-10

120

Phosphorus Equilibria Among Mafic Silicate Phases  

NASA Technical Reports Server (NTRS)

Phosphorus incorporation in major rock-forming silicate minerals has the following implications: (1) Reactions between phosphorus-hosting major silicates and accessory phosphates, which are also major trace element carriers, may control the stability of the latter and thus may affect the amount of phosphorus and other trace elements released to the coexisting melt or fluid phase. (2) Less of a phosphate mineral is needed to account for the bulk phosphorus of planetaty mantles. (3) During partial melting of mantle mineral assemblages or equilibrium fractional crystallization of basaltic magmas, and in the absence or prior to saturation with a phosphate mineral, silicate melts may become enriched in phosphorus, especially in the geochemically important low melt fraction regime, Although the small differences in the ionic radii of IVp5+, IVSi4+, and IV Al3+ makes phosphoms incorporation into crystalline silicates perhaps unsurprising, isostructural silicate and phosphate crystalline solids do not readily form solutions, e.g., (Fe, Mg)2SiO4 vs. LiMgPO4, SiO)2 VS. AlPO4. Nonetheless, there are reports of, poorly characterized silico-phosphate phases in angrites , 2-4 wt% P2O5 in olivine and pyroxene grains in pallasites and reduced terestrial basalts which are little understood but potentially useful, and up to 17 wt% P2O5 in olivine from ancient slags. However, such enrichments are rare and only underscore the likelihood of phosphoms incorporation in silicate minerals. The mechanisms that allow phosphorus to enter major rock-forming silicate minerals (e.g., Oliv, Px, Gt) remain little understood and the relevant data base is limited. Nonetheless, old and new high-pressure (5-10 GPa) experimental data suggest that P2O5 wt% decreases from silica-poor to silica-rich compositions or from orthosilicate to chain silicate structures (garnet > olivine > orthopyroxene) which implies that phosphorus incorporation in silicates is perhaps more structure-than site-specific. The data also indicate that DXVliQP2O5 decrease in the same order, but DOVLiQP2O5 and DOpx/LiQP205 are likely constant, respectively equal to 0.08(3) and 0.007(4), in contrast, DG1ILiQP205 increases from 0.15(3) to 0.36(10) as garnet becomes majoritic, thus silica-enriched, and may also depend on liquid composition (SiO2, P2O5 and Na2O wt%).

Berlin, Jana; Xirouchakis, Dimitris

2002-01-01

121

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

122

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

123

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

124

Optical Properties of Astronomical Silicates in the Far-infrared  

NASA Technical Reports Server (NTRS)

Correct interpretation of a vast array of astronomical data relies heavily on understanding the properties of silicate dust as a function of wavelength, temperature, and crystallinity. We introduce the QPASI-T (Optical Properties of Astronomical Silicates with Infrared Techniques) project to address the need for high fidelity optical characterization data on the various forms of astronomical dust. We use two spectrometers to provide extinction data for silicate samples across a wide wavelength range (from the near infrared to the millimeter). New experiments are in development that will provide complementary information on the emissivity of our samples, allowing us to complete the optical characterization of these dust materials. In this paper, we present initial results from several materials including amorphous iron silicate, magnesium silicate and silica smokes, over a wide range of temperatures, and discuss the design and operation of our new experiments.

Rinehart, Stephen A,; Benford, Dominic J.; Dwek, Eli; Henry, Ross M.; Nuth, Joseph A., III; Silverberg, Robert f.; Wollack, Edward J.

2008-01-01

125

Silicate volcanism on Io  

NASA Astrophysics Data System (ADS)

This paper is mainly concerned with the nature of volcanic eruptions on Io, taking into account questions regarding the presence of silicates or sulfur as principal component. Attention is given to the generation of silicate magma, the viscous dissipation in the melt zone, thermal anomalies at eruption sites, and Ionian volcanism. According to the information available about Io, it appears that its volcanism and hence its surface materials are dominantly silicic. Several percent of volatile materials such as sulfur, but also including sodium- and potassium-rich materials, may also be present. The volatile materials at the surface are continually vaporized and melted as a result of the high rates of silicate volcanism.

Carr, M. H.

1986-03-01

126

ESCA studies of the surface chemistry of zeolites  

SciTech Connect

It has been demonstrated that the constituents on the surfaces of various pure zeolites, clays, silicas, and aluminas yield reproducible ESCA peaks with unique binding energies. The collective patterns realized by these different binding energies strongly suggest the registration of selective group rather than elemental chemical shifts. The two primary chemical groups identified in many of the zeolites seem to be a unit that resembles SiO/sub 2/ and another that mimics N/sup + +/-Al/sub 2/O/sub 4//sup 2 -/ (where N symbolizes the cations, usually alkali or alkaline earth species that balance the aluminate charge), a feature supported by quantum calculations, relatively narrow line widths, and reproducible valence band and loss data. These results have been employed to determine the relative purity of the surface region of different conventionally prepared zeolite systems. High-resolution ESCA studies of mordenite, ZSM-5, a silicate surfaces always seem to exhibit Al(2p) spectra that are significantly broadened into patterns that suggest several Al-containing species. The nonzeolites present at the surface of these systems generally constitute more than 50% of the total aluminum. The primary impurity species have been identified as metal aluminates and aluminas in differing ratios apparently depending upon the cation (e.g., sodium) concentrations. The possible presence of silica on the surface of some freshly prepared zeolite systems is suggested, but unconfirmed.

Barr, T.L.; Lishka, M.A.

1986-06-11

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

Pyrolytic Synthesis of Carbon Nanotubes from Sucrose on a Mesoporous Silicate  

NASA Technical Reports Server (NTRS)

Multiwall carbon nanotubes were synthesized from sucrose by a pyrolytic technique using mesoporous MCM-41 silicate templates without transition metal catalysts. The Nanotubes were examined in the carbon/silicate composite and after dissolution of the silicate. High resolution transmission electron microscopy study of the multiwall nanotubes showed them to be 15 nm in diameter, 200 nm in length and close-ended. There was variation in crystallinity with some nanotubes showing disordered wall structures.

Abdel-Fattah, Tarek; Siochi, Mia; Crooks, Roy

2005-01-01

131

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

132

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

133

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

134

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

135

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

136

A theoretical study of Cu clusters in siliceous erionite  

NASA Astrophysics Data System (ADS)

In terms of periodic density functional theory method, we present a theoretical study of the structure and electronic properties of different composites, obtained by the inclusion of distinct Cux (x=2,4,6,8) clusters within the C1 cage of siliceous erionite-zeolite. Results shows that for a periodic distribution of Cux clusters on zeolite, the hosting of those is trough electrostatic confinement which is governed by framework oxygen atoms located at particular equivalent sites. However, when the permanency of a cluster in a C1 cage is compromised, the cluster-cluster long range Coulomb interactions could rise to keep it inside. In addition, results also show that the electronic properties of free Cux clusters are largely transferred to the formed composite.

Antúnez-García, Joel; Galván, D. H.; Posada-Amarillas, A.; Petranovskii, Vitalii

2014-02-01

137

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

138

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

139

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

140

Sodium silicate-based, alkali-activated slag mortars  

Microsoft Academic Search

Alkali activation of ground granulated blast furnace slag (GGBFS) with sodium silicate gave clinker-free binders, with high strength and early strength development, although set times were short and somewhat variable. Isothermal calorimetry detected three heat evolution peaks (wetting, gelation of activator and bulk reaction of slag). X-ray diffraction (XRD) showed no crystalline products. Hydration was investigated by scanning electron microscopy

A. R Brough; A Atkinson

2002-01-01

141

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

142

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

143

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

144

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

145

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

146

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

147

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

148

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

149

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

150

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

151

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

152

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.

153

Hydrothermal alteration and zeolitization of the Fohberg phonolite, Kaiserstuhl Volcanic Complex, Germany  

NASA Astrophysics Data System (ADS)

The subvolcanic Fohberg phonolite (Kaiserstuhl Volcanic Complex, Germany) is an economic zeolite deposit, formed by hydrothermal alteration of primary magmatic minerals. It is mined due to the high (>40 wt%) zeolite content, which accounts for the remarkable zeolitic physicochemical properties of the ground rock. New mineralogical and geochemical studies are carried out (a) to evaluate the manifestation of hydrothermal alteration, and (b) to constrain the physical and chemical properties of the fluids, which promoted hydrothermal replacement. The alkaline intrusion is characterized by the primary mineralogy: feldspathoid minerals, K-feldspar, aegirine-augite, wollastonite, and andradite. The rare-earth elements-phase götzenite is formed during the late-stage magmatic crystallization. Fluid-induced re-equilibration of feldspathoid minerals and wollastonite caused breakdown to a set of secondary phases. Feldspathoid minerals are totally replaced by various zeolite species, calcite, and barite. Wollastonite breakdown results in the formation of various zeolites, calcite, pectolite, sepiolite, and quartz. Zeolites are formed during subsolidus hydrothermal alteration (<150 °C) under alkaline conditions. A sequence of Ca-Na-dominated zeolite species (gonnardite, thomsonite, mesolite) is followed by natrolite. The sequence reflects an increase in and decrease in of the precipitating fluid. Low radiogenic 87Sr/86Sr values indicate a local origin of the elements necessary for secondary mineral formation from primary igneous phases. In addition, fractures cut the intrusive body, which contain zeolites, followed by calcite and a variety of other silicates, carbonates, and sulfates as younger generations. Stable isotope analysis of late-fracture calcite indicates very late circulation of meteoric fluids and mobilization of organic matter from surrounding sedimentary units.

Weisenberger, Tobias Björn; Spürgin, Simon; Lahaye, Yann

2014-11-01

154

Crystal Structure and Chemical Composition of a Presolar Silicate from the Queen Elizabeth Range 99177 Meteorite  

NASA Technical Reports Server (NTRS)

Mineral characterization of presolar silicate grains, the most abundant stardust phase, has provided valuable information about the formation conditions in circumstellar environments and in super-nova (SN) outflows. Spectroscopic observations of dust around evolved stars suggest a majority of amor-phous, Mg-rich olivine grains, but crystalline silicates, most of which are pyroxene, have also been observed [1]. The chemical compositions of hundreds of presolar silicates have been determined by Auger spectroscopy and reveal high Fe contents and nonstoichiometric compositions intermediate to olivine and pyroxene [2-6]. The unexpectedly high Fe contents can partly be attributed to secondary alteration on the meteorite parent bodies, as some grains have Fe isotopic anomalies from their parent stellar source [7]. Only about 35 presolar silicates have been studied for their mineral structures and chemical compositions by transmission electron microscopy (TEM). These grains display a wide range of compositions and structures, including crystalline forsterite, crystalline pyroxene, nanocrystalline grains, and a majority of amorphous nonstoichiometric grains. Most of these grains were identified in the primitive Acfer 094 meteorite. Presolar silicates from this meteorite show a wide range of Fe-contents, suggestive of secondary processing on the meteorite parent body. The CR chondrite QUE 99177 has not suffered as much alteration [8] and displays the highest presolar silicate abundance to date among carbonaceous chondrites [3, 6]. However, no mineralogical studies of presolar silicates from this meteorite have been performed. Here we examine the mineralogy of a presolar silicate from QUE 99177.

Nguyen, A. N.; Keller, L. P.; Rahman, Z.; Messenger, S.

2013-01-01

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

Vibrational spectroscopy of the double 4-, 6-membered rings in silicates and siloxanes  

NASA Astrophysics Data System (ADS)

Siloxanes and silicates are different chemical compounds but they all contain silicooxygen units. Double 6-membered silicooxygen rings are important building units of more complicated silicate structures (silicalites and zeolites). The aim of this work is to understand vibrational spectra of double 6-membered cyclosilicates based on the spectra of selected siloxanes. For the selected siloxane molecules infrared spectra have been calculated (using various terminal groups) by ab initio method and compared with the experimental ones of silicates. Visualization of the calculated normal modes has been used as a tool to define the band type in the spectra of siloxanes and to interpret them in terms of group-characteristic frequencies as tetrahedral, overtetrahedral and ring bands. Similarities between IR spectra of T8 and T12 siloxanes and the spectra of double 4-, 6-membered cyclosilicates allow to identify the bands in the experimental spectra of silicates.

Handke, Miros?aw; Jastrz?bski, Witold

2005-06-01

158

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

159

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

160

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

161

Steps toward interstellar silicate mineralogy. V. Thermal Evolution of Amorphous Magnesium Silicates and Silica  

NASA Astrophysics Data System (ADS)

The thermally induced amorphous-to-crystalline transition has been studied for bulk sheets and micrometre-sized particles of magnesium silicate glass (MgSiO3), nanometre-sized amorphous magnesium silicate (MgSiO3 and Mg2SiO4 smokes) and amorphous silica particles (SiO2). Silicate glass was produced by the shock-quenching of melts. Samples of nanometre-sized smoke particles have been obtained by the laser ablation technique. Both the MgSiO3 and the Mg2SiO4 smokes have been found to consist of two particle species; particles of smaller size ranging in diametre from 10 nm to about 100 nm and bigger size ranging from a few 100 nm to almost 3 micrometres in diametre. Nanometre-sized particles have been shown to be depleted in magnesium whereas the micrometre-sized particles were found to be enriched in Mg. Generally, the particles are composed of nonstoichiometric magnesium silicates with compositions varying even inside of the particles. Frequently, the particles contained internal voids that are assumed to have been formed by thermal shrinkage or outgassing of the particles' interior during cooling. Annealing at 1000 K transformed the magnesium silicate smokes into crystalline forsterite (c-Mg2SiO4), tridymite (a crystalline modification of SiO2) and amorphous silica (a-SiO2) according to the initial Mg/Si-ratio of the smoke. Crystallization took place within a few hours for the Mg2SiO4 smoke and within one day for the MgSiO3 smoke. The MgSiO3 glass evolved more slowly because crystallization started at the sample surface. It has been annealed at temperatures ranging from 1000 to 1165 K. In contrast to the smoke samples, MgSiO3 glass crystallized as orthoenstatite (MgSiO3). Only after 50 hours of annealing at 1000 K, weak indications of forsterite and tridymite formation have been found in the X-ray diffraction spectra. At a temperature of 1000 K, amorphous silica nanoparticles showed distinctly lower rates of thermal evolution compared with the magnesium silicates. At 1220 K, the timescale of crystallization of a-SiO2 into cristobalite and tridymite amounts to 4.5 h. From the experiments, crystallization parameters have been obtained: activation energy and velocity of crystal growth. The spectra shown in this study will be made publically available in the electronic database (http://www.astro.uni-jena.de).

Fabian, D.; Jäger, C.; Henning, Th.; Dorschner, J.; Mutschke, H.

2000-12-01

162

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

163

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

164

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

165

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

166

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

167

Calcium silicate insulation structure  

DOEpatents

An insulative structure including a powder-filled evacuated casing utilizes a quantity of finely divided synthetic calcium silicate having a relatively high surface area. The resultant structure-provides superior thermal insulating characteristics over a broad temperature range and is particularly well-suited as a panel for a refrigerator or freezer or the insulative barrier for a cooler or a insulated bottle.

Kollie, Thomas G. (Oak Ridge, TN); Lauf, Robert J. (Oak Ridge, TN)

1995-01-01

168

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.

169

Optical Properties of Astronomical Silicates with Infrared Techniques (OPASI-T)  

NASA Technical Reports Server (NTRS)

Astronomical dust is observed in a variety of astrophysical environments and plays an important role in radiative processes and chemical evolution in the galaxy. Depending upon the environment, dust can be either carbon-rich or oxygen-rich (silicate grains). Both astronomical observations and ground-based data show that the optical properties of silicates can change dramatically with the crystallinity of the material, and recent laboratory research provides evidence that the optical properties of silicate dust vary as a function of temperature as well. Therefore, correct interpretation of a vast array of astronomical data relies on the understanding of the properties of silicate dust as functions of wavelength, temperature, and crystallinity. The OPASI-T (Optical Properties of Astronomical Silicates with Infrared Techniques) project addresses the need for high quality optical characterization of metal-enriched silicate condensates using a variety of techniques. A combination of both new and established experiments are used to measure the extinction, reflection, and emission properties of amorphous silicates across the infrared (near infrared to millimeter wavelengths), providing a comprehensive data set characterizing the optical parameters of dust samples. We present room temperature measurements and the experimental apparatus to be used to investigate and characterize additional metal-silicate materials.

Rinehart, Stephen

2010-01-01

170

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

171

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

172

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

173

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

174

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

175

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

176

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

177

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

178

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

179

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

180

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

181

Synthesis of Na–X zeolites from tripolaceous deposits (Crotone, Italy) and volcanic zeolitised rocks (Vico volcano, Italy)  

Microsoft Academic Search

Synthesis of zeolitic minerals (Na–X and HS) by the use of natural materials (naturally zeolitised alkaline volcanic rocks and “Tripoli”) has been achieved. Synthesis was conducted at hydrothermal conditions (80 °C) by the use of alkaline silicates (NaxSiyOz) and alkaline aluminates (NaxAlyOz). Chemical treatments were made on “Tripoli” rocks (mainly constituted by opaline silica) coming from Crotone Basin (southern Italy)

D. Novembre; B. Di Sabatino; D. Gimeno; M. Garcia-Vallès; S. Martínez-Manent

2004-01-01

182

Prospects for the direct electron crystallographic determination of zeolite structures.  

PubMed

Recently two successful zeolite structures based on experimental electron crystallographic data have been published. Diffraction and image data based on the silicate portion of the zeolite, mordenite, which are perturbed by dynamical (as well as secondary) scattering, have been simulated by a multiple-beam dynamical scattering program. Structure analyses with these data show that the above claims are not unreasonable, given a high enough accelerating voltage for the electron beam. If, for example, 2.9 A resolution micrographs are taken from a 120 A thick crystal in a 200 or 400 kV electron microscope, the crystallographic phases found by image analysis (Fourier filtration) are accurate enough to be extended by the Sayre equation to the (atomic) resolution limit of the electron diffraction pattern (for example from a 105 A thick crystal illuminated by a 1,200 kV electron source). The resultant potential map can be interpreted to find most of the atomic positions and the remaining ones will appear during the progress of a Fourier refinement. PMID:9080411

Dorset, D L; McCourt, M P

1997-02-01

183

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

184

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

185

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

186

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

187

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...

188

21 CFR 172.410 - Calcium silicate.  

Code of Federal Regulations, 2011 CFR

...Drugs 3 2011-04-01 2011-04-01 false Calcium silicate. 172.410 Section 172.410 Food...HUMAN CONSUMPTION Anticaking Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium...

2011-04-01

189

21 CFR 172.410 - Calcium silicate.  

Code of Federal Regulations, 2013 CFR

...Drugs 3 2013-04-01 2013-04-01 false Calcium silicate. 172.410 Section 172.410 Food...HUMAN CONSUMPTION Anticaking Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium...

2013-04-01

190

21 CFR 172.410 - Calcium silicate.  

Code of Federal Regulations, 2014 CFR

...Drugs 3 2014-04-01 2014-04-01 false Calcium silicate. 172.410 Section 172.410 Food...HUMAN CONSUMPTION Anticaking Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium...

2014-04-01

191

21 CFR 172.410 - Calcium silicate.  

Code of Federal Regulations, 2012 CFR

...Drugs 3 2012-04-01 2012-04-01 false Calcium silicate. 172.410 Section 172.410 Food...HUMAN CONSUMPTION Anticaking Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium...

2012-04-01

192

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

193

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

194

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

195

Phonolite-hosted zeolite deposits in the Kaiserstuhl Volcanic Complex, Germany  

NASA Astrophysics Data System (ADS)

Several subvolcanic phonolitic intrusions occur within the Miocene Kaiserstuhl Volcanic Complex (KVC) located in the central-southern segment of the Upper Rhine Graben, which is part of the European Cenozoic Rift System. Hydrothermally altered phonolitic rocks are of economic interest, due to the high (>40 wt%) zeolite content, which accounts for the remarkable zeolitic physicochemical properties of the ground rock. These properties have widespread industrial application in water softening, catalysis, remediation of soils and soil quality, wastewater treatment, and as additive in the cement industry. Currently the largest phonolite intrusion Fohberg is active in mining, located in the eastern part of the KVC. The Endhale phonolite, approximately 1.5 km to the north marks a further deposit currently under exploration. Both phonolites are hosted in Tertiary sedimentary units. The aim of this study is to carry out a new mineralogical and geochemical data a) to evaluate the manifestation of hydrothermal alteration of the Fohberg and Endhale phonolitic intrusions, and b) to constrain the physical and chemical properties of the fluids, which promoted hydrothermal replacement of primary igneous minerals. The high degree of alteration is in contrast to the only slightly altered Kirchberg phonolite in the western KVC. The alkaline intrusive bodies are characterized by the primary mineralogy: feldspathoid mineral, K-feldspar, aegirine-augite, wollastonite, and andradite, with additional REE-minerals (e.g. götzenite). Fluid-induced re-equilibration of feldspathoid minerals and wollastonite caused breakdown to a set of secondary phases. Feldspathoid minerals are totally replaced by secondary phases including various zeolite species, calcite, and barite. Wollastonite breakdown results in the formation of various zeolites, calcite, pectolite, sepiolite, and quartz. The large variability of secondary minerals indicates a heterogenic fluid composition throughout the phonolitic intrusions and through time. Zeolites formed during sub-solidus hydrothermal alteration under alkaline conditions and completely replace feldspathoid minerals in the matrix of the rock. A sequence of Ca-Na dominated zeolite species (gonnardite, thomsonite, mesolite) is followed by pure sodium endmember species (analcime, natrolite). These sequence reflects an increase in log[aNa+)/(aH+)] of the precipitating fluid. In contrast to the Fohberg phonolitc the Endhale phonolite contains analcime in addition to natrolite as pure Na zeolite species. The appearance of analcime is caused by higher silica activity during fluid rock interaction, which favors the formation of analcime over natrolite. The Fohberg phonolite is cut by fractures, which are totally or partially sealed with secondary minerals. Secondary minerals contain zeolites, followed by calcite and a variety of other silicates, carbonates, and sulphates as younger generations. Stable isotope analyses of late fracture calcite indicate the late circulation of meteoric fluids and mobilization of organic matter from surrounding sedimentary units.

Weisenberger, Tobias; Spürgin, Simon

2014-05-01

196

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

197

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

198

Electronic structure calculations of calcium silicate hydrates  

SciTech Connect

Many phases in the calcium-silicate-hydrate system can develop in cement exposed over long periods of time to temperatures above 25 C. As a consequence, chemical reactions involving these phases can affect the relative humidity and water chemistry of a radioactive waste repository that contains significant amounts of cement. In order to predict and simulate these chemical reactions, the authors are developing an internally consistent database of crystalline Ca-Si-hydrate structures. The results of first principles electronic structure calculations on two such phases, wollastonite (CaSiO{sub 3}) and xonotlite (Ca{sub 6}Si{sub 6}O{sub 17}(OH){sub 2}), are reported here. The calculated ground state properties are in very good agreement with experiment, providing equilibrium lattice parameters within about 1--1.4% of the experimentally reported values. The roles of the different types of oxygen atoms, which are fundamental to understanding the energetics of crystalline Ca-Si-hydrates are briefly discussed in terms of their electronic state densities. The good agreement with experiment for the lattice parameters and the consistency of the electronic density of states features for the two structures demonstrate the applicability of these electronic structure methods in calculating the fundamental properties of these phases.

Sterne, P.A. [Univ. of California, Davis, CA (United States). Dept. of Physics]|[Lawrence Livermore National Lab., CA (United States); Meike, A. [Lawrence Livermore National Lab., CA (United States)

1995-11-01

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

Ion implantation in silicate glasses  

SciTech Connect

This review examines the effects of ion implantation on the physical properties of silicate glasses, the compositional modifications that can be brought about, and the use of metal implants to form colloidal nanosize particles for increasing the nonlinear refractive index.

Arnold, G.W.

1993-12-01

201

The Silicate Structures: Chalkboard Demonstration  

NSDL National Science Digital Library

Three-dimensional, magnetic representations of SiO tetrahedra and cations are manipulated on a chalkboard to create five basic silicate structures. Students are expected to complete a worksheet accompanying the exercise, which addresses silicate structures, bond types and strengths, physical properties (e.g. fracture, cleavage), Si:O ratio and introduction to vocabulary such as "felsic" and "mafic," and mineral formulae. The worksheet and chalkboard demonstration are designed to simplify silicate structures from complex ball-and-stick models typically used in textbook figures, and to grant students a visual, three-dimensional, manipulable, perspective on what tends to be a confusing concept. This exercise may be simplified or expanded to suit timeframe and the needs of the audience. Benefits of this approach include reinforcement of lecture concepts, broad appeal for a student group with multiple learning styles and degrees of knowledge, and strengthened understanding of the silicate structures.

Stevens, Liane

202

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...

203

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

204

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

205

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

206

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

207

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

208

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

209

Low-voltage bendable pentacene thin-film transistor with stainless steel substrate and polystyrene-coated hafnium silicate dielectric.  

PubMed

The hafnium silicate and aluminum oxide high-k dielectrics were deposited on stainless steel substrate using atomic layer deposition process and octadecyltrichlorosilane (OTS) and polystyrene (PS) were treated improve crystallinity of pentacene grown on them. Besides, the effects of the pentacene deposition condition on the morphologies, crystallinities and electrical properties of pentacene were characterized. Therefore, the surface treatment condition on dielectric and pentacene deposition conditions were optimized. The pentacene grown on polystyrene coated high-k dielectric at low deposition rate and temperature (0.2-0.3 Å/s and R.T.) showed the largest grain size (0.8-1.0 ?m) and highest crystallinity among pentacenes deposited various deposition conditions, and the pentacene TFT with polystyrene coated high-k dielectric showed excellent device-performance. To decrease threshold voltage of pentacene TFT, the polystyrene-thickness on high-k dielectric was controlled using different concentration of polystyrene solution. As the polystyrene-thickness on hafnium silicate decreases, the dielectric constant of polystyrene/hafnium silicate increases, while the crystallinity of pentacene grown on polystyrene/hafnium silicate did not change. Using low-thickness polystyrene coated hafnium silicate dielectric, the high-performance and low voltage operating (<5 V) pentacene thin film transistor (?: ~2 cm(2)/(V s), on/off ratio, >1 × 10(4)) and complementary inverter (DC gains, ~20) could be fabricated. PMID:22462593

Yun, Dong-Jin; Lee, Seunghyup; Yong, Kijung; Rhee, Shi-Woo

2012-04-01

210

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

211

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

212

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

213

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

214

Post-synthetic preparation of Sn-, Ti- and Zr-beta: a facile route to water tolerant, highly active Lewis acidic zeolites.  

PubMed

A two-step procedure for the post-synthetic preparation of Lewis acidic Sn-, Zr- and Ti-zeolite ? is reported. Dealumination of a commercially available Al-? zeolite leads to the formation of highly siliceous material containing silanol nests, which can be filled in a second step via the solid-state ion-exchange or impregnation of an appropriate metal precursor. Spectroscopic studies indicate that each metal is subsequently coordinated within the zeolite framework, and that little or no bulk oxides are formed--despite the high metal loadings. The synthesised catalysts demonstrate excellent activity for the isomerisation of glyceraldehyde to dihydroxyacetone, a key model reaction for the upgrading of bio-renewable feedstocks, and the epoxidation of bulky olefins. PMID:24407516

Wolf, Patrick; Hammond, Ceri; Conrad, Sabrina; Hermans, Ive

2014-03-21

215

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

216

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

217

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

218

The crystalline revolution :ISO's finding opens a new research field, "astro-mineralogy"  

NASA Astrophysics Data System (ADS)

Silicate minerals were known to be a main component of dust in space, but detecting them in a crystallised state has been a surprise. It allows the identification of precise silicates in astronomical objects, which will open "a totally new field in astronomy: astro-mineralogy. This is the crystalline revolution", said the author, Dutch astronomer Rens Waters of Amsterdam university. "It's really fantastic, this possibility of identifying the silicates. Before ISO everybody thought that all silicates in space were amorphous, without a well-ordered internal structure; that means you cannot differentiate among the many different silicates existing. Now we can try to identify them and track their presence in different regions. A whole new research field is starting", said Rens Waters, who brought to the press conference samples of several terrestrial crystalline silicates: olivine and pyroxene, the most common silicates on Earth. Crystals give key clues about the physical conditions and evolutionary history of crystal-bearing objects. The precise mechanisms for crystal-making are now being researched now very actively in the laboratories, although some working-hypotheses are already being used. For instance, crystals can be made by heating the material to temperatures above 1 300 degrees Centigrade and then cooling it down slowly. Those found so far by ISO are at -170 degrees Centigrade, both in stellar envelopes and in protoplanetary discs. In the case of the old stars -red giant stars, where crystals are found to account for as much as 20% of all the surrounding dust, astronomers think that that the high temperatures near the star triggered the crystallisation of the silicates. In the protoplanetary discs some experts postulate that electric shocks - like lightning flashes - heated the dust, which cooled afterwards. "The crystals detected by ISO in these discs have a size of about a thousandth of a millimetre. They collide with each other, forming bigger and bigger bodies. Models predict that in about ten to one hundred million years they will make planets", Waters says. "In fact, crystalline silicates are very common in our own Solar System. You also have them in the comet Hale Bopp!". The reason why crystalline silicates had not been detected before in stars has to do with their low temperatures. Cold material emits mostly infrared light, which means an infrared space telescope like ESA's ISO was needed. The two high-resolution spectrometers on-board the satellite, able to detect the 'chemical fingerprint' of the crystals, did the rest. Astronomers are sure about the discovery because those chemical fingerprints, the spectra, can be compared in laboratories with spectra from crystalline silicates found on Earth. This method has demonstrated the crystalline structure and has even already allowed the identification of some of the crystals, such as forsterite and enstatite. However, crystalline silicates are a large family and their chemical signatures can be very similar; to enlarge the list of precise crystals more work will be needed, say experts in space chemistry. That is just one of the open questions requiring lab work. There's at least another one: crystalline silicates are found around old stars, in protoplanetary disks and in our own Solar System, but not in the space among the stars; astronomers can't explain it yet. "Crystalline silicates are synthesised around the stars; then that dust goes into the interstellar space, and enriches the raw material out of which more stars and planets will form. So you would expect crystals also to be in the interstellar medium! Crystals will certainly make us learn a lot...", says Waters. "This finding shows that ISO is really unveiling the chemistry of the Universe", says ESA astronomer Alberto Salama, chairman of the workshop about ISO results in spectroscopy held this week at ESA's Villafranca station in Madrid where the results were presented to the scientific community. "This is becoming more and more a 'hot

2000-02-01

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

Comparative pathology of silicate pneumoconiosis.  

PubMed Central

A simple pneumoconiosis with lamellar birefringent crystals was observed in animals dying in the San Diego Zoo. We studied 100 autopsies from 11 mammalian and eight avian species. In mammals, mild pulmonary lesions comprised crystal-laden macrophages in alveoli and lymphatics. Interstitial fibrosis was present in 20% of cases. There were no nodules. In birds, dust retention produced large granulomas around tertiary bronchi without fibrosis. Mineralogic analysis using scanning and transmission electron microscopy showed most of the crystals to be silicates. Ninety percent were complex silicates, with aluminum-potassium silicates comprising 70% of the analyzed particles. Electron and x-ray diffraction showed the silicates to be muscovite mica and its hydrothermal degradation product, ie, illite clay. This mica was also present on filtration membranes of atmospheric air samples obtained from the San Diego Zoo. The amount of dust retention was related to the animal's age, anatomic or ecologic variances, and length of stay in the San Diego Zoo. Its semidesert atmosphere is rich in silicates, which are inhaled and deposited in the lungs. Similar mica-induced lesions are found in humans living in this region or the Southwest of the USA. This simple pneumoconiosis is likely to be widespread in human populations living in desert or semidesert climates. Images Figure 9 Figure 10 Figure 7 Figure 8 Figure 5 Figure 6 Figure 1 Figure 2 Figure 3 Figure 4 PMID:223447

Brambilla, C.; Abraham, J.; Brambilla, E.; Benirschke, K.; Bloor, C.

1979-01-01

222

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

223

Coating crystalline nuclear waste forms to improve inertness  

SciTech Connect

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

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

1981-01-01

224

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

225

FORMATION OF COSMIC CRYSTALS IN HIGHLY SUPERSATURATED SILICATE VAPOR PRODUCED BY PLANETESIMAL BOW SHOCKS  

SciTech Connect

Several lines of evidence suggest that fine silicate crystals observed in primitive meteorite and interplanetary dust particles (IDPs) nucleated in a supersaturated silicate vapor followed by crystalline growth. We investigated evaporation of {mu}m-sized silicate particles heated by a bow shock produced by a planetesimal orbiting in the gas in the early solar nebula and condensation of crystalline silicate from the vapor thus produced. Our numerical simulation of shock-wave heating showed that these {mu}m-sized particles evaporate almost completely when the bow shock is strong enough to cause melting of chondrule precursor dust particles. We found that the silicate vapor cools very rapidly with expansion into the ambient unshocked nebular region; for instance, the cooling rate is estimated to be as high as 2000 K s{sup -1} for a vapor heated by a bow shock associated with a planetesimal of radius 1 km. The rapid cooling of the vapor leads to nonequilibrium gas-phase condensation of dust at temperatures much lower than those expected from the equilibrium condensation. It was found that the condensation temperatures are lower by a few hundred K or more than the equilibrium temperatures. This explains the results of the recent experimental studies of condensation from a silicate vapor that condensation in such large supercooling reproduces morphologies similar to those of silicate crystals found in meteorites. Our results strongly suggest that the planetesimal bow shock is one of the plausible sites for formation of not only chondrules but also other cosmic crystals in the early solar system.

Miura, H.; Yamada, J.; Tsukamoto, K.; Nozawa, J. [Department of Earth Sciences, Tohoku University, Aoba 6-3, Aramaki, Aoba-ku, Sendai 980-8578 (Japan); Tanaka, K. K.; Yamamoto, T. [Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819 (Japan); Nakamoto, T., E-mail: miurah@m.tohoku.ac.j [Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro, Tokyo 152-8551 (Japan)

2010-08-10

226

TRANSMISSION ELECTRON MICROSCOPY OF Al-RICH SILICATE STARDUST FROM ASYMPTOTIC GIANT BRANCH STARS  

SciTech Connect

We report on transmission electron microscopy (TEM) investigations of two mineralogically unusual stardust silicates to constrain their circumstellar condensation conditions. Both grains were identified by high spatial resolution nano secondary ion mass spectrometry (NanoSIMS) in the Acfer 094 meteorite, one of the most pristine carbonaceous chondrites available for study. One grain is a highly crystalline, highly refractory (Fe content < 0.5 at%), structurally undisturbed orthopyroxene (MgSiO{sub 3}) with an unusually high Al content (1.8 {+-} 0.5 at%). This is the first TEM documentation of a single crystal pyroxene within the complete stardust silicate data set. We interpret the microstructure and chemistry of this grain as being a direct condensate from a gas of locally non-solar composition (i.e., with a higher-than-solar Al content and most likely also a lower-than-solar Mg/Si ratio) at (near)-equilibrium conditions. From the overabundance of crystalline olivine (six reported grains to date) compared to crystalline pyroxene (only documented as a single crystal in this work) we infer that formation of olivine over pyroxene is favored in circumstellar environments, in agreement with expectations from condensation theory and experiments. The second stardust silicate consists of an amorphous Ca-Si rich material which lacks any crystallinity based on TEM observations in which tiny (<20 nm) hibonite nanocrystallites are embedded. This complex assemblage therefore attests to the fast cooling and rapidly changing chemical environments under which dust grains in circumstellar shells form.

Vollmer, Christian [Institute for Mineralogy, University of Muenster, Correnssstr. 24, D-48149 Muenster (Germany); Hoppe, Peter [Max Planck Institute for Chemistry, Particle Chemistry Department, Hahn-Meitner-Weg 1, D-55128 Mainz (Germany); Brenker, Frank E., E-mail: christian.vollmer@wwu.de [Institute of Geoscience/Mineralogy, Goethe-University Frankfurt, Altenhoeferallee 1, D-60438 Frankfurt (Germany)

2013-05-20

227

Identifying the crystal graveyards remaining after large silicic eruptions  

NASA Astrophysics Data System (ADS)

The formation of crystal-poor high-silica rhyolite via extraction of interstitial melt from an upper crustal mush predicts the complementary formation of large amounts of (typically unerupted) silicic cumulates. However, identification of these cumulates remains controversial. One hindrance to our ability to identify them is a lack of clear predictions for complementary chemical signatures between extracted melts and their residues. To address this discrepancy, we present a generalized geochemical model tracking the evolution of trace elements in a magma reservoir concurrently experiencing crystallization and extraction of interstitial melt. Our method uses a numerical solution rather than analytical, thereby allowing for various dependencies between crystallinity, partition coefficients for variably compatible and/or incompatible elements, and melt extraction efficiency. Results reveal unambiguous fractionation signatures for the extracted melts, while those signatures are muted for their cumulate counterparts. Our model is first applied to a well-constrained example (Searchlight pluton, USA), and provides a good fit to geochemical data. We then extrapolate our results to understanding the relationship between volcanic and plutonic silicic suites on a global scale. Utilizing the NAVDAT database to identify crystal accumulation or depletion signatures for each suite, we suggest that many large granitoids are indeed silicic cumulates, although their crystal accumulation signature is expected to be subtle.

Gelman, Sarah E.; Deering, Chad D.; Bachmann, Olivier; Huber, Christian; Gutiérrez, Francisco J.

2014-10-01

228

Hemolytic activity of five different calcium silicates.  

PubMed Central

Mineral characteristics and the in vitro hemolytic activity of three synthetic and two natural calcium silicates (CaSi) are compared. Hemolysis is higher for the synthetic compounds than for the natural ones. The difference is accentuated by weak ultrasonication of the minerals. No variation was observed within the two groups, including both acicular and fibrous forms. Calcium was released from the minerals during storage in Tris-buffered saline. At the same time, hemolysis decreased, and crystallographic alterations occurred in the leached minerals. Treatment of the CaSi with calcium chelators (EGTA and EDTA) did not change hemolytic activity. An increase was observed when 30 mM calcium was added. Hemolysis is related to specific surface areas and the crystalline structure of the minerals. Calcium may also be a contributing factor. Images FIGURE 1. a FIGURE 1. b FIGURE 1. c FIGURE 1. d FIGURE 1. e FIGURE 1. f FIGURE 7. a FIGURE 7. b FIGURE 7. c FIGURE 7. d FIGURE 7. e FIGURE 7. f PMID:6315361

Skaug, V; Gylseth, B

1983-01-01

229

Lithologic mapping of silicate rocks using TIMS  

NASA Technical Reports Server (NTRS)

Common rock-forming minerals have thermal infrared spectral features that are measured in the laboratory to infer composition. An airborne Daedalus scanner (TIMS) that collects six channels of thermal infrared radiance data (8 to 12 microns), may be used to measure these same features for rock identification. Previously, false-color composite pictures made from channels 1, 3, and 5 and emittance spectra for small areas on these images were used to make lithologic maps. Central wavelength, standard deviation, and amplitude of normal curves regressed on the emittance spectra are related to compositional information for crystalline igneous silicate rocks. As expected, the central wavelength varies systematically with silica content and with modal quartz content. Standard deviation is less sensitive to compositional changes, but large values may result from mixed admixture of vegetation. Compression of the six TIMS channels to three image channels made from the regressed parameters may be effective in improving geologic mapping from TIMS data, and these synthetic images may form a basis for the remote assessment of rock composition.

Gillespie, A. R.

1986-01-01

230

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

231

Tobermorite group of silicates (Tables)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume I4 'Inosilicates' of Volume 27 'Magnetic properties of non-metallic inorganic compounds based on transition elements' of Landolt-Börnstein - Group III Condensed Matter. It contains the data of the tobermorite group of silicates (Tables)

Burzo, E.

232

Tobermorite group of silicates (Figures)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume I4 'Inosilicates' of Volume 27 'Magnetic properties of non-metallic inorganic compounds based on transition elements' of Landolt-Börnstein - Group III Condensed Matter. It contains the data of the tobermorite group of silicates (Figures)

Burzo, E.

233

Tobermorite group of silicates (Text)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume I4 'Inosilicates' of Volume 27 'Magnetic properties of non-metallic inorganic compounds based on transition elements' of Landolt-Börnstein - Group III Condensed Matter. It contains the data of the tobermorite group of silicates (Text)

Burzo, E.

234

Laser processing of siliceous materials  

Microsoft Academic Search

Laser processing of siliceous materials becomes increasingly important. Analogous to the laser processing of conventional materials there are applications in the fields of cleaning, surface processing, cutting, etc. The present paper concerns the state of the art and new applications: (1) Laser cleaning of natural stone surfaces. The good disability allows restoration work to be carried out conveniently, as for

Michael Panzner; Andreas Lenk; Guenter R. Wiedemann; Jan Hauptmann; Hans J. Weiss; Thomas Ruemenapp; Lothar Morgenthal; Eckhard Beyer

2000-01-01

235

Solubility limits of silicate melts  

Microsoft Academic Search

A statistical mechanical model of silica melt is presented in which metal oxides are incorporated into the bonding network. In this approach a Flory-type lattice model for binary silicate melts is coupled with a set of chemical reactions that determine the extent of metal oxide incorporation into the silica network and regulate the distribution of nonbridging oxygens around a central

L. Rene Corrales; Keith D. Keefer

1997-01-01

236

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

237

Amended Silicated for Mercury Control  

SciTech Connect

Amended Silicates{trademark}, a powdered, noncarbon mercury-control sorbent, was tested at Duke Energy's Miami Fort Station, Unit 6 during the first quarter of 2006. Unit 6 is a 175-MW boiler with a cold-side electrostatic precipitator (ESP). The plant burns run-of-the-river eastern bituminous coal with typical ash contents ranging from 8-15% and sulfur contents from 1.6-2.6% on an as-received basis. The performance of the Amended Silicates sorbent was compared with that for powdered activated carbon (PAC). The trial began with a period of baseline monitoring during which no sorbent was injected. Sampling during this and subsequent periods indicated mercury capture by the native fly ash was less than 10%. After the baseline period, Amended Silicates sorbent was injected at several different ratios, followed by a 30-day trial at a fixed injection ratio of 5-6 lb/MMACF. After this period, PAC was injected to provide a comparison. Approximately 40% mercury control was achieved for both the Amended Silicates sorbent and PAC at injection ratios of 5-6 lbs/MMACF. Higher injection ratios did not achieve significantly increased removal. Similar removal efficiencies have been reported for PAC injection trials at other plants with cold-side ESPs, most notably for plants using medium to high sulfur coal. Sorbent injection did not detrimentally impact plant operations and testing confirmed that the use of Amended Silicates sorbent does not degrade fly ash quality (unlike PAC). The cost for mercury control using either PAC or Amended Silicates sorbent was estimated to be equivalent if fly ash sales are not a consideration. However, if the plant did sell fly ash, the effective cost for mercury control could more than double if those sales were no longer possible, due to lost by-product sales and additional cost for waste disposal. Accordingly, the use of Amended Silicates sorbent could reduce the overall cost of mercury control by 50% or more versus PAC for locations where fly ash is sold as a by-product.

James Butz; Thomas Broderick; Craig Turchi

2006-12-31

238

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

239

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

240

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

241

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.

242

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

243

Use of zeolitized pumice waste as a water softening agent.  

PubMed

Important pumice quarries are located on the island of Lipari (Italy) where an intense activity of extraction, transformation and trade of pumice takes place. Nevertheless, the finest fraction amounting to about 60% of mined pumice is discarded and disposed off in open-sky pits. This implies economic losses for mining industries and environmental problems for neighbouring villages. In order to find a sustainable use of this waste, we resumed and improved an old extractive process with aqueous sodium alkali, where a sodium silicate concentrated solution was produced together with an unextracted residue partially converted into zeolite P in Na+ form and now we are searching for suitable applications of this residue. In this paper, we relate about its use as a low cost water softening agent on the basis of results obtained from several tests both in batch systems and column. They show that, at room temperature, the residue works well with calcium and badly with magnesium, whereas, at 60 degrees C, also the affinity toward Mg ions increases to acceptable levels. Repeated regenerations of the residue with concentrated NaCl solutions do not appreciably compromise the performance. The limits for the possible use as water softening agent are defined. PMID:17320286

Arrigo, I; Catalfamo, P; Cavallari, L; Di Pasquale, S

2007-08-17

244

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

245

A New Catalog of Silicate Carbon Stars  

NASA Astrophysics Data System (ADS)

A silicate carbon star is a carbon star which shows circumstellar silicate dust features. We collect a sample of 44 silicate carbon stars from the literature and investigate the validity of the classification. For some objects, it is uncertain whether the central star is a carbon star. We confirm that 29 objects are verified silicate carbon stars. We classify the confirmed objects into three subclasses based on the evolution phase of the central star. To investigate the effect of the chemical transition phase from O to C, we use the radiative transfer models for the detached silicate dust shells. The spectral energy distributions and the infrared two-color diagrams of the silicate carbon stars are compared with the theoretical model results. For the chemical transition model without considering the effect of a disk, we find that the life time of the silicate feature is about 50 to 400 years depending on the initial dust optical depth.

Kwon, Young-Joo; Suh, Kyung-Won

2014-08-01

246

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

247

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

248

Mineralogy of the Dhofar 489 Lunar Meteorite, Crystalline Matrix Breccia with Magnesian Anorthositic Clasts  

NASA Astrophysics Data System (ADS)

Dhofar 489, a crystalline matrix feldspathic breccia gives the mg# of mafic silicates higher than those of FAN trend in the An vs. mg# diagram, but D489 does not show granulitic texture. We examine the origin of this magnesian anorthosite.

Takeda, H.; Saiki, K.; Ishii, T.; Otsuki, M.

2003-03-01

249

Improved epitaxy of ultrathin praseodymia films on chlorine passivated Si(111) reducing silicate interface formation  

SciTech Connect

Ultrathin praseodymia films have been deposited on both Cl-passivated and nonpassivated Si(111) substrates by molecular beam epitaxy. Comparative studies on the crystallinity and stoichiometry are performed by x-ray photoelectron spectroscopy, x-ray standing waves, and x-ray reflectometry. On nonpassivated Si(111) an amorphous silicate film is formed. In contrast, praseodymia deposited on Cl-passivated Si(111) form a well-ordered crystalline film with cubic-Pr{sub 2}O{sub 3} (bixbyite) structure. The vertical lattice constant of the praseodymia film is increased by 1.4% compared to the bulk value. Furthermore, the formation of an extended amorphous silicate interface layers is suppressed and confined to only one monolayer.

Gevers, S.; Bruns, D.; Weisemoeller, T.; Wollschlaeger, J. [Department of Physics, University of Osnabrueck, Barbarastrasse 7, D-49069 Osnabrueck (Germany); Flege, J. I.; Kaemena, B.; Falta, J. [Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, D-28359 Bremen (Germany)

2010-12-13

250

Multiple phase structures of Hf silicide precipitated from Hf silicate: An atomic view  

NASA Astrophysics Data System (ADS)

Multiple phase structures of crystalline hafnium silicide precipitated from the silicate have been found as a function of temperature (900-1000 degC) by using scanning tunneling microscopy and x-ray photoelectron spectroscopy. At 900 degC, a crystalline silicate structure transforms into a bulklike (1 x1) "facetbar" of HfSi2 near the topmost surface, but into a "platelet" around the interface with Si. A Si-depletion zone is found to only form near platelets, not facetbars. Upon further annealing to 1000 degC, facetbars likely transform into platelets, and the atomic structure of a platelet also transforms to a patchlike feature having two equivalent antiphase sites, which are shifted by a half (approx2.3 A) of the (1 x1) unit length along the <110> directions. copyright 2002 American Vacuum Society.

Lee, Jung-Ho; Ichikawa, Masakazu

2002-09-01

251

Pressure and temperature influence on tricalcium silicate hydration. A 1H and 29Si NMR study  

NASA Astrophysics Data System (ADS)

Hydration of tricalcium silicate with and without ground quartz, at high temperature (12 ° 16 °C) and high pressure (1000 bars), has been studied by 29Si and 1H CRAMPS NMR. Cross-polarization, for long contact times, allows to separate crystalline phases from poorly crystallized hydrates and to detect small amounts of the crystalline phases. The influence of pressure is also studied by cross-polarization. L'hydratation du silicate tricalcique avec et sans quartz broyé, à haute température (12 °C 16 °C) et haute pression (1000 bars) a été étudiée par RMN du 29Si et du proton (CRAMPS). La polarisation croisée, utilisée avec des temps de contact longs, permet de séparer les hydrates cristallins des hydrates mal cristallisés et de détecter des traces de ces cristaux. Elle permet également d'étudier l'influence de la pression.

Bresson, B.; Zanni, H.

1998-02-01

252

Modifying Silicates for Better Dispersion in Nanocomposites  

NASA Technical Reports Server (NTRS)

An improved chemical modification has been developed to enhance the dispersion of layered silicate particles in the formulation of a polymer/silicate nanocomposite material. The modification involves, among other things, the co-exchange of an alkyl ammonium ion and a monoprotonated diamine with interlayer cations of the silicate. The net overall effects of the improved chemical modification are to improve processability of the nanocomposite and maximize the benefits of dispersing the silicate particles into the polymer. Some background discussion is necessary to give meaning to a description of this development. Polymer/silicate nanocomposites are also denoted polymer/clay composites because the silicate particles in them are typically derived from clay particles. Particles of clay comprise layers of silicate platelets separated by gaps called "galleries." The platelet thickness is 1 nm. The length varies from 30 nm to 1 m, depending on the silicate. In order to fully realize the benefits of polymer/silicate nanocomposites, it is necessary to ensure that the platelets become dispersed in the polymer matrices. Proper dispersion can impart physical and chemical properties that make nanocomposites attractive for a variety of applications. In order to achieve nanometer-level dispersion of a layered silicate into a polymer matrix, it is typically necessary to modify the interlayer silicate surfaces by attaching organic functional groups. This modification can be achieved easily by ion exchange between the interlayer metal cations found naturally in the silicate and protonated organic cations - typically protonated amines. Long-chain alkyl ammonium ions are commonly chosen as the ion-exchange materials because they effectively lower the surface energies of the silicates and ease the incorporation of organic monomers or polymers into the silicate galleries. This completes the background discussion. In the present improved modification of the interlayer silicate surfaces, the co-ion exchange strengthens the polymer/silicate interface and ensures irreversible separation of the silicate layers. One way in which it does this is to essentially tether one amine of each diamine molecule to a silicate surface, leaving the second amine free for reaction with monomers during the synthesis of a polymer. In addition, the incorporation of alkyl ammonium ions into the galleries at low concentration helps to keep low the melt viscosity of the oligomer formed during synthesis of the polymer and associated processing - a consideration that is particularly important in the case of a highly cross-linked, thermosetting polymer. Because of the chemical bonding between the surface-modifying amines and the monomers, even when the alkyl ammonium ions become degraded at high processing temperature, the silicate layers do not aggregate and, hence, nanometer-level dispersion is maintained.

Campbell, Sandi

2005-01-01

253

Zeolite structure type EAB: Crystal structure and mechanism for the topotactic transformation of the Na, TMA form  

NASA Astrophysics Data System (ADS)

Synthetic zeolite (Na, TMA)-E represents a new structure type designated EAB. Detailed structure analyses based on X-ray powder diffraction data have been carried out at room temperature, 220°C, and 350°C. The silicate framework, having maximum symmetry {P6 3}/{mmc}, consists of parallel 6-rings in ABBACC sequence as opposed to AABAAC in erionite (with which it has mistakenly been identified). Large changes in conformation of the EAB framework precede the transformation of (Na, TMA)-E to a sodalite-type product above 360°C. There are also strong indications for this reaction to be topotactic, whereby only one-twelfth of the original siloxane bridges are broken. Details of an acid-base reaction mechanism proceeding in characteristic loops of the structure are discussed. This process brings about the inversion of one-third of the tetrahedra in the silicate framework. The presence of water appears to be essential in this model-type reaction.

Meier, W. M.; Groner, M.

1981-04-01

254

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

255

Silicate Dust in RS Ophiuchi  

NASA Astrophysics Data System (ADS)

We present Spitzer IRS spectra of the recurrent nova RS Ophiuchi obtained between 2006 and 2009. The data show emission lines due to HI, [Ne II], [Ne V], [Ne VI] and [O IV] and the well known silicate features at 10 ?m and 18 ?m, whose behaviour are reported here. The silicate features are variable in the period covered by the observations, appearing strongest in our 2007 data. Interestingly, the central wavelength of the 18 ?m band is shorter than observed in other symbiotic systems and other circumstellar environments, suggesting unusual grain properties in RS Oph. We report changes that have taken place in the dusty environment in RS Oph and investigate the properties of the dust grains.

Rushton, M. T.; Woodward, C. E.; Helton, L. A.; Gehrz, R. D.; Evans, A.; Kaminsky, B.; Pavlenko, Y. V.; Eyres, S. P. S.; Maxwell, M.

2014-12-01

256

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

257

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

258

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

259

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

260

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

261

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

262

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

263

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

264

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

265

Improvement of dissolution rate of piroxicam by inclusion into MCM-41 mesoporous silicate.  

PubMed

The aim of the present paper was the use of mesoporous silicate MCM-41 to increase the dissolution rate of piroxicam, a non-steroidal anti-inflammatory drug-class II of the Biopharmaceutic Classification System. The inclusion/adsorption compound of piroxicam in MCM-41 was obtained with a drug loading of about 14%. X-ray powder diffraction and differential scanning calorimetry (DSC) revealed the presence of piroxicam not arranged in crystalline form and FT-IR spectroscopy showed the presence of light interactions (hydrogen bonds) between the silicate silanols and the drug. The decrease of Brunauer, Emmett and Teller (B.E.T.) specific surface area and pore volume between free MCM-41 and the inclusion/adsorption compound was a prove of the presence of piroxicam inside the mesopores. The inclusion compound was submitted to in vitro dissolution tests and a remarkable dissolution rate improvement was observed in comparison to the crystalline drug in all tested conditions. The dissolution profile at pH 1.2 was comparable to that of the marketed product Brexin, a formulation with rapid analgesic effect onset. The improvement of dissolution rate is due to both the lack of drug in the crystalline form and to the extremely large surface area of the siliceous support. Physical stability tests of the free drug and the inclusion/adsorption complex were conducted as well over one month storage at 40 degrees C at different relative humidity. PMID:17826966

Ambrogi, V; Perioli, L; Marmottini, F; Giovagnoli, S; Esposito, M; Rossi, C

2007-11-01

266

Formation of Uranyl-Silicate Nanoparticles at Ambient Conditions  

NASA Astrophysics Data System (ADS)

Uranium(VI)-silicates are the dominant crystalline form of U(VI) at and near Earth's surface, but are difficult to form as pure phases under ambient conditions because of slow reaction kinetics aided by similar thermodynamic stabilities of the many possible minerals. We have investigated the effects of pH (2 to 11) and time (1 to 10 days) on the formation of U(VI)-silicates from initial solutions with U = 0.05 M and a fixed molar ratio of U:Si = 2:1, 1:1, 1:2, and 1:5 using high-energy X-ray scattering (HEXS), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), powder X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and solution thermodynamic modeling. Previously, we used HEXS to identify from solutions with U:Si = 1:2 at pH 5 to 9, aged for one day, a trimeric U-silicate structural unit, or synthon, approximately one nanometer in dimension with U-U correlation lengths of about 0.4 nm. This synthon is a structural building block in uranyl silicate minerals such as soddyite, boltwoodite, and weeksite. ATR-FTIR results on the full set of samples show systematic changes in peak positions along with appearance and disappearance of vibrational modes that occurred with reaction time, pH and/or U:Si ratio; whereas, XRD indicated only a crystalline Na-boltwoodite-like phase at pH 11 and without the correlation length-scale resolution of HEXS. HRTEM results show few particles in a matrix of material containing areas having the lower correlation length visible in HEXS data. The data show clearly different mixtures of solids, including silica, and precipitate sizes under all conditions that transform over the 1 to 10 day aging period. The experimental reactions simulate conditions in the subsurface at sites contaminated with uranium, and the results are relevant to processes of uranium adsorption and colloid formation. [This work is supported by DOE's Environmental Remediation Science Program].

Nagy, K. L.; Sturchio, N. C.; Klie, R. F.; Skanthakumar, S.; Soderholm, L.

2008-12-01

267

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

268

Development of Desiccant System using Wakkanai Siliceous Shale  

NASA Astrophysics Data System (ADS)

The aim of this study is to develop a desiccant system using Wakkanai siliceous shale. A honeycombed desiccant rotor containing this shale's powder and chlorides was made and evaluated. However a specific surface area and a pore volume were smaller than a silica-gel rotor or a zeolite rotor, the maximum amount of water adsorption was twice as other rotors. We have verified the function of this desiccant rotor concerning adsorption and desorption of moisture from the draft experiments. The rotor containing the shale could adsorb moisture stably in the cyclic test, and be regenerated by 40°C air under this experimental condition. This means that the exhaust heat from the heat pump can be used for regenerating rotor. Furthermore, the numerical simulation was carried out on the assumption that this rotor was used for a dehumidification for the residential air conditioning in Tokyo. This rotor could adsorb 37.1% moisture of the required dehumidification amount for the hottest day in 2008. When we employed a pre-cooling before dehumidification, the amount of adsorption increased to 66.2%.

Nakabayashi, Saya; Nagano, Katsunori; Nakamura, Makoto; Togawa, Junya; Kurokawa, Asami

269

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

270

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

271

Adsorption kinetics of silicic acid on akaganeite.  

PubMed

As part of a series of studies on the interaction between ferric ions and silicic acid in the hydrosphere, the adsorption of silicic acid on akaganeite was investigated kinetically at various pH values. The adsorption of silicic acid increased with increasing pH over an initial pH range of 4-11.5. In the kinetic experiment, the Cl(-) was released from akaganeite much faster than silicic acid was adsorbed. From this result, we concluded that chloride ions bound on the surface of akaganeite are released and Fe-OH or Fe-O(-) sites are formed, which then acts as an adsorption site for silicic acid. The uptake mechanism of silicic acid by akaganeite is significantly different from that by schwertmannite, despite the presence of the same tunnel structure. PMID:23538050

Naren, Gaowa; Ohashi, Hironori; Okaue, Yoshihiro; Yokoyama, Takushi

2013-06-01

272

Competing mechanisms of catalytic H2 formation and dissociation on ultrasmall silicate nanocluster dust grains  

NASA Astrophysics Data System (ADS)

Silicate dust grains are thought to be essential in catalysing the formation of H2. Ultrasmall silicates (diameter ?1.5 nm) are fundamental intermediates in silicate dust formation in stellar outflows, and are ubiquitous in the interstellar medium. To investigate the catalytic formation and dissociation of H2 on such nanosilicates, we have performed ab initio quantum chemical calculations of hydrogen interacting with a stable 21 atom nanosilicate cluster having the stoichiometry of forsterite, (MgO)6(SiO2)3. Due to its small size and high percentage of surface atoms, our particle inherently does not exhibit the bulk forsterite crystal structure and possesses a range of chemisorption and physisorption sites, presumably similar to those that larger amorphous silicates would offer. We find a number of exothermic H2 formation routes and pathways for H2 catalytic dissociation on the nanosilicate. In particular, we discover some H2 formation routes that are energetically more favourable than that reported for the forsterite (010) surface. Further, we find a linear correlation between the dissociative chemisorption of two H atoms and the dissociation transition state, suggestive of a general Brønsted-Evans-Polanyi relation for H2 dissociation on bare silicates independent of dust grain size and/or crystallinity.

Kerkeni, Boutheïna; Bromley, Stefan T.

2013-10-01

273

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

274

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

275

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

276

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

277

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

278

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

279

Effect of silicate ions on electrode overvoltage  

NASA Technical Reports Server (NTRS)

The influence of the addition of a silicate to a caustic solution (KOH) is studied in order to determine the degree to which silicates inhibit the corrosion of chrysotile under conditions of electrolysis at working temperatures of 100 C and above. In an alkaline solution containing various silicate concentrations, current density was increased and electrode overvoltage was measured. Results show that silicate ion concentrations in the electrolyte increase with temperature without effecting electrochemical performance up to 115 C at 700 MA/sqcm. At this point the concentration is about 0.5 g Si/100 g KOH. Beyond this limit, electrolytic performance rapidly degenerates due to severe oxidation of the electrodes.

Gras, J. M.; Seite, C.

1979-01-01

280

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

SciTech Connect

Composite materials of SBA-15/zeolite Y were synthesized from zeolite Y precursor and a synthesis mixture of mesoporous silicate SBA-15 via a hydrothermal process in the presence of a slightly acidic media of pH 4-6 with 2M H{sub 2}SO{sub 4}. The SBA-15/ZY composites showed Type IV adsorption isotherms, narrow BJH average pore size distribution of 4.9 nm, surface areas up to 800 m{sup 2}2/g and pore volumes 1.03 cm{sup 3}, all comparable to pure SBA-15 synthesized under similar conditions. Chemical analysis revealed Si/Al ratio down to 8.5 in the most aluminated sample, and {sup 27}AlSS MAS NMR confirmed aluminum was in tetrahedral coordination. This method of introduction of Al in pure T{sub d} coordination is effective in comparison to other direct and post synthesis alumination methods. Bronsted acid sites were evident from a pyridinium peak at 1544 cm-1 in the FTIR spectrum after pyridine adsorption, and from NH{sub 3} -TPD experiments. SBA-15/ZY composites showed significant catalytic activities for the dealkylation of isopropylbenzene to benzene and propene, similar to those of commercial zeolite Y. It was observed that higher conversion for catalysts synthesized with high amount of ZY precursor mixture added to the SBA-15. Over all the composites has shown good catalytic activity. Further studies will be focused on gaining a better understand the nature of the precursor, and to characterize and to locate the acid sites in the composite material. The composite will also be evaluated for heavy oil conversion to naphtha and middle distillates.

Conrad Ingram; Mark Mitchell

2005-11-15

281

Biochemical evolution. I. Polymerization on internal, organophilic silica surfaces of dealuminated zeolites and feldspars  

PubMed Central

Catalysis at mineral surfaces might generate replicating biopolymers from simple chemicals supplied by meteorites, volcanic gases, and photochemical gas reactions. Many ideas are implausible in detail because the proposed mineral surfaces strongly prefer water and other ionic species to organic ones. The molecular sieve silicalite (Union Carbide; = Al-free Mobil ZSM-5 zeolite) has a three-dimensional, 10-ring channel system whose electrically neutral Si-O surface strongly adsorbs organic species over water. Three -O-Si tetrahedral bonds lie in the surface, and the fourth Si-O points inwards. In contrast, the outward Si-OH of simple quartz and feldspar crystals generates their ionic organophobicity. The ZSM-5-type zeolite mutinaite occurs in Antarctica with boggsite and tschernichite (Al-analog of Mobil Beta). Archean mutinaite might have become de-aluminated toward silicalite during hot/cold/wet/dry cycles. Catalytic activity of silicalite increases linearly with Al-OH substitution for Si, and Al atoms tend to avoid each other. Adjacent organophilic and catalytic Al-OH regions in nanometer channels might have scavenged organic species for catalytic assembly into specific polymers protected from prompt photochemical destruction. Polymer migration along weathered silicic surfaces of micrometer-wide channels of feldspars might have led to assembly of replicating catalytic biomolecules and perhaps primitive cellular organisms. Silica-rich volcanic glasses should have been abundant on the early Earth, ready for crystallization into zeolites and feldspars, as in present continental basins. Abundant chert from weakly metamorphosed Archaean rocks might retain microscopic clues to the proposed mineral adsorbent/catalysts. Other framework silicas are possible, including ones with laevo/dextro one-dimensional channels. Organic molecules, transition-metal ions, and P occur inside modern feldspars. PMID:9520372

Smith, Joseph V.

1998-01-01

282

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

283

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

284

Carbon substitution for oxygen in silicates in planetary interiors  

PubMed Central

Amorphous silicon oxycarbide polymer-derived ceramics (PDCs), synthesized from organometallic precursors, contain carbon- and silica-rich nanodomains, the latter with extensive substitution of carbon for oxygen, linking Si-centered SiOxC4-x tetrahedra. Calorimetric studies demonstrated these PDCs to be thermodynamically more stable than a mixture of SiO2, C, and silicon carbide. Here, we show by multinuclear NMR spectroscopy that substitution of C for O is also attained in PDCs with depolymerized silica-rich domains containing lithium, associated with SiOxC4-x tetrahedra with nonbridging oxygen. We suggest that significant (several percent) substitution of C for O could occur in more complex geological silicate melts/glasses in contact with graphite at moderate pressure and high temperature and may be thermodynamically far more accessible than C for Si substitution. Carbon incorporation will change the local structure and may affect physical properties, such as viscosity. Analogous carbon substitution at grain boundaries, at defect sites, or as equilibrium states in nominally acarbonaceous crystalline silicates, even if present at levels at 10–100 ppm, might form an extensive and hitherto hidden reservoir of carbon in the lower crust and mantle. PMID:24043830

Sen, Sabyasachi; Widgeon, Scarlett J.; Navrotsky, Alexandra; Mera, Gabriela; Tavakoli, Amir; Ionescu, Emanuel; Riedel, Ralf

2013-01-01

285

21 CFR 582.2122 - Aluminum calcium silicate.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122...Anticaking Agents § 582.2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2...

2011-04-01

286

21 CFR 182.2122 - Aluminum calcium silicate.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2009-04-01 true Aluminum calcium silicate. 182.2122 Section 182.2122...Anticaking Agents § 182.2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2...

2010-04-01

287

21 CFR 182.2122 - Aluminum calcium silicate.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Aluminum calcium silicate. 182.2122 Section 182.2122...Anticaking Agents § 182.2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2...

2011-04-01

288

21 CFR 582.2122 - Aluminum calcium silicate.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122...Anticaking Agents § 582.2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2...

2010-04-01

289

21 CFR 182.2122 - Aluminum calcium silicate.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Aluminum calcium silicate. 182.2122 Section 182.2122...Anticaking Agents § 182.2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2...

2012-04-01

290

21 CFR 582.2122 - Aluminum calcium silicate.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122...Anticaking Agents § 582.2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2...

2013-04-01

291

21 CFR 582.2122 - Aluminum calcium silicate.  

Code of Federal Regulations, 2014 CFR

...2014-04-01 2014-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122...Anticaking Agents § 582.2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2...

2014-04-01

292

21 CFR 582.2122 - Aluminum calcium silicate.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122...Anticaking Agents § 582.2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2...

2012-04-01

293

21 CFR 182.2122 - Aluminum calcium silicate.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Aluminum calcium silicate. 182.2122 Section 182.2122...Anticaking Agents § 182.2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2...

2013-04-01

294

21 CFR 182.2122 - Aluminum calcium silicate.  

Code of Federal Regulations, 2014 CFR

...2014-04-01 2014-04-01 false Aluminum calcium silicate. 182.2122 Section 182.2122...Anticaking Agents § 182.2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2...

2014-04-01

295

40 CFR 721.9513 - Modified magnesium silicate polymer (generic).  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Modified magnesium silicate polymer (generic). 721...Substances § 721.9513 Modified magnesium silicate polymer (generic). ...substance identified generically as modified magnesium silicate polymer (PMN...

2012-07-01

296

40 CFR 721.9513 - Modified magnesium silicate polymer (generic).  

Code of Federal Regulations, 2014 CFR

...2014-07-01 2014-07-01 false Modified magnesium silicate polymer (generic). 721...Substances § 721.9513 Modified magnesium silicate polymer (generic). ...substance identified generically as modified magnesium silicate polymer (PMN...

2014-07-01

297

40 CFR 721.9513 - Modified magnesium silicate polymer (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Modified magnesium silicate polymer (generic). 721...Substances § 721.9513 Modified magnesium silicate polymer (generic). ...substance identified generically as modified magnesium silicate polymer (PMN...

2013-07-01

298

The 8-13 micron spectra of comets and the composition of silicate grains  

NASA Astrophysics Data System (ADS)

We have analyzed the existing spectra of seven comets which show an emission feature at 7.8-13 micrometers. Most have been converted to a common calibration, taking into account the SiO feature in late-type standard stars. The spectra are compared with spectra of the Trapezium, interplanetary dust particles (IDPs), laboratory mineral samples, and small particle emission models. The emission spectra show a variety of shapes; there is no unique 'cometary silicate'. A peak at 11.20-11.25 micrometers, indicative of small crystalline olivine particles, is seen in only three comets of this sample, P/Halley, Bradfield 1987 XXIX, and Levy 1990 XX. The widths of the emission features range from 2.6 to 4.1 micrometers (FWHM). To explain the differing widths and the broad 9.8 micrometers maximum, glassy silicate particles, including both pyroxene and olivine compositions, are the most plausible candidates. Calculations of emission models confirm that small grains of glassy silicate well mixed with carbonaceous material are plausible cometary constituents. No single class of chondritic aggregate IDPs exhibits spectra closely matching the comet spectra. A mixture of IDP spectra, particularly the glass-rich aggregates, approximately matches the spectra of comets P/Halley, Levy, and Bradfield 1987 XXIX. Yet, if comets are simply a mix of IDP types, it is puzzling that the classes of IDPs are so distinct. None of the comet spectra match the spectrum of the Trapezium. Thus, the mineralogy of the cometary silicates is not the same as that of the interstellar medium. The presence of a component of crystalline silicates in comets may be evidence of mixing between high- and low-temperature regions in the solar nebula.

Hanner, M. S.; Lynch, D. K.; Russell, R. W.

1994-04-01

299

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

300

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

301

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

302

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

303

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

304

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

305

Better Alternatives to “Astronomical Silicate”: Laboratory-Based Optical Functions of Cosmic Abundance Glass with Application to HD 161796  

NASA Astrophysics Data System (ADS)

“Astronomical” or “cosmic” silicate optical (dielectric) functions over a large fraction of the electromagnetic spectrum are critical for interpreting the radiative environments of systems as varied as H II regions, circumstellar dust around evolved stars and in disks around young stellar objects (YSOs), and active galactic nuclei (AGN). However, the optical functions that have been previously derived by the community to address this need are for compositionally and structurally disparate materials, and were prepared with inconsistent methodology, kludging observational data and laboratory data with different experimental methods to populate the wavelength space. New quantitative laboratory data are available to build up wavelength coverage for amorphous silicates in a more systematic way. We present optical functions and extinction cross-sections derived from mid-UV to far-IR laboratory transmission spectra of cosmic abundance silicate glass. The advantages of using these data are that our glass sample was synthesized especially with cosmic (solar) abundances in mind and excludes iron. We compare these results to other popular optical functions used to model amorphous silicates (e.g., “astronomical” or “cosmic” silicate by Draine & Lee 1984, Draine 2003, Ossenkopf et al. 1992), both directly and in application to HD 161796, a spherically symmetric, O-rich system with a visible central star, optically thin dust shell, and energy intermediate to AGB and PN class targets. The new cosmic silicate optical functions have much lower UV-vis and NIR opacity than the traditionally used functions necessitating significantly more dust (1 or 2 orders of magnitude for mass) to model an object like HD 161796. Furthermore, the lower opacity has an impact on the fraction of crystalline material needed to match the observed spectrum. Previous models produced using older optical functions will underestimate the dust mass and overestimate the importance of crystalline silicates. This work is supported through NSF AST-1009544 and NASA APRA04-000-0041.

Pitman, Karly M.; Speck, A.; Hofmeister, A. M.; Buffard, A. S.; Whittington, A. G.

2013-01-01

306

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

307

The speciation of water in silicate melts  

Microsoft Academic Search

Previous models of water solubility in silicate melts generally assume essentially complete reaction of water molecules to hydroxyl groups. In this paper a new model is proposed that is based on the hypothesis that the observed concentrations of molecular water and hydroxyl groups in hydrous silicate glasses reflect those of the melts from which they were quenched. The new model

Edward Stolper

1982-01-01

308

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...

309

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

310

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

311

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

312

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

313

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.

314

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

315

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

316

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

317

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

318

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

319

Order and disorder in calcium-silicate-hydrate.  

PubMed

Despite advances in the characterization and modeling of cement hydrates, the atomic order in Calcium-Silicate-Hydrate (C-S-H), the binding phase of cement, remains an open question. Indeed, in contrast to the former crystalline model, recent molecular models suggest that the nanoscale structure of C-S-H is amorphous. To elucidate this issue, we analyzed the structure of a realistic simulated model of C-S-H, and compared the latter to crystalline tobermorite, a natural analogue of C-S-H, and to an artificial ideal glass. The results clearly indicate that C-S-H appears as amorphous, when averaged on all atoms. However, an analysis of the order around each atomic species reveals that its structure shows an intermediate degree of order, retaining some characteristics of the crystal while acquiring an overall glass-like disorder. Thanks to a detailed quantification of order and disorder, we show that, while C-S-H retains some signatures of a tobermorite-like layered structure, hydrated species are completely amorphous. PMID:24908022

Bauchy, M; Qomi, M J Abdolhosseini; Ulm, F-J; Pellenq, R J-M

2014-06-01

320

Order and disorder in calcium-silicate-hydrate  

NASA Astrophysics Data System (ADS)

Despite advances in the characterization and modeling of cement hydrates, the atomic order in Calcium-Silicate-Hydrate (C-S-H), the binding phase of cement, remains an open question. Indeed, in contrast to the former crystalline model, recent molecular models suggest that the nanoscale structure of C-S-H is amorphous. To elucidate this issue, we analyzed the structure of a realistic simulated model of C-S-H, and compared the latter to crystalline tobermorite, a natural analogue of C-S-H, and to an artificial ideal glass. The results clearly indicate that C-S-H appears as amorphous, when averaged on all atoms. However, an analysis of the order around each atomic species reveals that its structure shows an intermediate degree of order, retaining some characteristics of the crystal while acquiring an overall glass-like disorder. Thanks to a detailed quantification of order and disorder, we show that, while C-S-H retains some signatures of a tobermorite-like layered structure, hydrated species are completely amorphous.

Bauchy, M.; Qomi, M. J. Abdolhosseini; Ulm, F.-J.; Pellenq, R. J.-M.

2014-06-01

321

Order and disorder in calcium–silicate–hydrate  

SciTech Connect

Despite advances in the characterization and modeling of cement hydrates, the atomic order in Calcium–Silicate–Hydrate (C–S–H), the binding phase of cement, remains an open question. Indeed, in contrast to the former crystalline model, recent molecular models suggest that the nanoscale structure of C–S–H is amorphous. To elucidate this issue, we analyzed the structure of a realistic simulated model of C–S–H, and compared the latter to crystalline tobermorite, a natural analogue of C–S–H, and to an artificial ideal glass. The results clearly indicate that C–S–H appears as amorphous, when averaged on all atoms. However, an analysis of the order around each atomic species reveals that its structure shows an intermediate degree of order, retaining some characteristics of the crystal while acquiring an overall glass-like disorder. Thanks to a detailed quantification of order and disorder, we show that, while C–S–H retains some signatures of a tobermorite-like layered structure, hydrated species are completely amorphous.

Bauchy, M., E-mail: bauchy@mit.edu [Concrete Sustainability Hub, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); MIT-CNRS Joint Laboratory at Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Qomi, M. J. Abdolhosseini; Ulm, F.-J. [Concrete Sustainability Hub, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Pellenq, R. J.-M. [Concrete Sustainability Hub, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); MIT-CNRS Joint Laboratory at Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Centre Interdisciplinaire des Nanosciences de Marseille, CNRS and Aix-Marseille University, Campus de Luminy, 13288 Marseille Cedex 09 (France)

2014-06-07

322

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

323

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

324

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

325

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

326

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

327

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

328

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

329

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

330

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

331

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

332

Alkali Silicate Vehicle Forms Durable, Fireproof Paint  

NASA Technical Reports Server (NTRS)

The problem: To develop a paint for use on satellites or space vehicles that exhibits high resistance to cracking, peeling, or flaking when subjected to a wide range of temperatures. Organic coatings will partially meet the required specifications but have the inherent disadvantage of combustibility. Alkali-silicate binders, used in some industrial coatings and adhesives, show evidence of forming a fireproof paint, but the problem of high surface-tension, a characteristic of alkali silicates, has not been resolved. The solution: Use of a suitable non-ionic wetting agent combined with a paint incorporating alkali silicate as the binder.

Schutt, John B.; Seindenberg, Benjamin

1964-01-01

333

Bis-GMA/TEGDMA Dental Composites Reinforced with Electrospun Nylon 6 Nanocomposite Nanofibers Containing Highly Aligned Fibrillar Silicate Single Crystals  

PubMed Central

The objective of this research was to study the reinforcement of electrospun nylon 6/fibrillar silicate nanocomposite nanofibers on Bis-GMA/TEGDMA dental composites. The hypothesis was that the uniform distribution of nano-scaled and highly aligned fibrillar silicate single crystals into electrospun nylon 6 nanofibers would improve the mechanical properties of the resulting nanocomposite nanofibers, and would lead to the effective reinforcement of dental composites. The nylon 6/fibrillar silicate nanocomposite nanofibers were crystalline, structurally oriented and had an average diameter of approximately 250 nm. To relatively well distribute nanofibers in dental composites, the nanofiber containing composite powders with a particle structure similar to that in interpenetration networks were prepared first, and then used to make the dental composites. The results indicated that small mass fractions (1 % and 2 %) of nanofiber impregnation improved the mechanical properties substantially, while larger mass factions (4 % and 8 %) of nanofiber impregnation resulted in less desired mechanical properties. PMID:17940586

Tian, Ming; Gao, Yi; Liu, Yi; Liao, Yiliang; Xu, Riwei; Hedin, Nyle E.; Fong, Hao

2007-01-01

334

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

335

Erbium Silicon Oxide crystalline films prepared by MOMBE  

NASA Astrophysics Data System (ADS)

Er-Si-O crystalline thin film preparation on silicon substrates by using metal organic molecular beam epitaxy (MOMBE) is proposed. Tetra ethoxy silane (TEOS) and tris-2,2,6,6-tetra methyl-3,5-octane dionato erbium (Er(TMOD) 3) were used as Si-O and Er-O precursors, respectively. The Er-Si-O thin film crystallizes mainly during the post-annealing process and into a novel type of erbium-silicate crystalline compounds, which have not ever been reported. The atomic fraction of Er:Si:O in the prepared thin film is 3:2:8. The Er 3+ related PL spectra show a fine structure with a line width of less than 1 meV at 20 K and 4 meV at room temperature. The narrow line width is due to the crystalline nature. In addition, the PL spectrum fine structure observed in these Er-Si-O films has reproduced the fine structure observed in Er-Si-O crystallites prepared by the wet-chemical method reported by Isshiki et al. The present results have proved that the method proposed in this paper is effective to form Er-Si-O crystalline films.

Masaki, K.; Isshiki, H.; Kimura, T.

2005-02-01

336

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

337

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

338

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

339

Silicate production and availability for mineral carbonation.  

PubMed

Atmospheric carbon dioxide sequestered as carbonates through the accelerated weathering of silicate minerals is proposed as a climate change mitigation technology with the potential to capture billions of tonnes of carbon per year. Although these materials can be mined expressly for carbonation, they are also produced by human activities (cement, iron and steel making, coal combustion, etc.). Despite their potential, there is poor global accounting of silicates produced in this way. This paper presents production estimates (by proxy) of various silicate materials including aggregate and mine waste, cement kiln dust, construction and demolition waste, iron and steel slag, and fuel ash. Approximately 7-17 billion tonnes are produced globally each year with an approximate annual sequestration potential of 190-332 million tonnes C. These estimates provide justification for additional research to accurately quantify the contemporary production of silicate minerals and to determine the location and carbon capture potential of historic material accumulations. PMID:21332128

Renforth, P; Washbourne, C-L; Taylder, J; Manning, D A C

2011-03-15

340

Silicate Liquid Immiscibility in Young Impact Glasses  

NASA Astrophysics Data System (ADS)

Emulsion textures have rarely been described from impact melts. Here, we present and compare several examples of silicate emulsions in impact melts and show that liquid immiscibility may play an important role in the formation of impact melts.

Hamann, C.; Hecht, L.; Schultze, D.; Ebert, M.; Reimold, W. U.; Wirth, R.

2014-09-01

341

Siliceous microfossil extraction from altered Monterey rocks  

SciTech Connect

Samples of altered Monterey rocks of differing lithologies were processed by various methods to develop new techniques for extracting siliceous microfossils. The preliminary use of thin sections made from the same rocks reduced the number of probable samples (samples worth further processing) by about one-third. Most of the siliceous microfossils contained in altered Monterey rocks appear to be highly recrystallized and are extremely fragile; however, some contained silicified and silica-infilled radiolarians and planktonic and benthonic foraminifera, which are very tough. In general the most useful techniques were gently hydrochloric acid, hydrogen peroxide, formic acid, monosodium glutamate, and regular siliceous microfossil extraction techniques. Unsuccessful techniques and a new siliceous microfossil flotation technique are also documented.

Nelson, C.O.; Casey, R.E.

1986-04-01

342

Peroxide-assisted syntheses of metal silicates  

SciTech Connect

Peroxide-containing intermediates have played pivotal roles in new synthesis of several magnesium silicates including olivine, forsterite, transition metal-doped forsterite, and enstatite. The involvement of a little-known hydroperoxide of magnesium will be discussed. Elaboration of the synthesis methodology has produced layered silicates such as the fluoro-mica, potassium fluorophlogopite, and a fluoro-talc that has a higher level of substitution of hydroxide by fluoride than any previously reported.

Burlitch, J.M. [Cornell Univ., Ithaca, NY (United States)

1993-12-31

343

Sepiolite and palygorskite group of silicates  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume I5? `Phyllosilicates - Part ?' of Volume 27 `Magnetic properties of non-metallic inorganic compounds based on transition elements` of Landolt-Börnstein - Group III `Condensed Matter'. It presents silicates belonging to the sepiolite and palygorskite group of silicates, discussing their crystal structures, lattice parameters, nuclear gamma resonance (NGR), nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) data, electrical properties and dielectric behavior, and optical properties.

Burzo, E.

344

Laser processing of siliceous materials  

NASA Astrophysics Data System (ADS)

Laser processing of siliceous materials becomes increasingly important. Analogous to the laser processing of conventional materials there are applications in the fields of cleaning, surface processing, cutting, etc. The present paper concerns the state of the art and new applications: (1) Laser cleaning of natural stone surfaces. The good disability allows restoration work to be carried out conveniently, as for example the complete removal of crusts or the removal to such degree that moisture is not trapped beneath. (2) Non-slip finish of polished natural stone surfaces: The excellent focusing of laser beams on spots as small as 100 micrometer and below can be exploited to produce macroscopically invisible structures on the surfaces of different materials. This permits microscopically small craters and lentil shaped depressions to be generated on the stone surface. Therefore it is possible to provide a non-slip finish to polished natural stone surfaces without noticeably impairing the gloss. (3) Concrete cutting: In Europe, and particularly in Germany, there is a growing demand for redevelopment of concrete apartment buildings, involving the removal of non-bearing walls and the cutting of openings. The temporal relocation of residents due to the noise and moisture from the use of diamond tools could be avoided by applying a laser cutting technology. With a 3 kW-Nd-YAG-laser, 70 mm concrete can be cut with rates up to 25 mm/min.

Panzner, Michael; Lenk, Andreas; Wiedemann, Guenter R.; Hauptmann, Jan; Weiss, Hans J.; Ruemenapp, Thomas; Morgenthal, Lothar; Beyer, Eckhard

2000-08-01

345

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

346

H2O Inner-Surface Interactions in Micro/Nanoporous Silicates: Thermodynamic Behavior and Low Energy Molecular Vibrations  

NASA Astrophysics Data System (ADS)

Macroscopic thermodynamic and molecular-scale behavior related to silicate surface-fluid interactions in nature is complex and poorly understood. The study of confined H2O at inner surfaces in micro/ nanoporous silicates is helpful for understanding outer-surface interactions, because such phases offer simpler physicochemical systems for investigation. We are investigating the nature of H2O in various micro/nanoporous silicates. Low temperature calorimetric heat capacity (Cp) determinations have been made to determine thermodynamic behavior. Powder IR and polarized single-crystal Raman spectroscopy are used to investigate local features such as bonding and dynamics. In this report, Cp behavior and low energy external H2O modes related to van der Waals and/or hydrogen bonding at inner surfaces are emphasized. The first group of microporous silicates that includes cordierite, Mg2Al4Si5O18· xH2O, and beryl, Be2Al3Si6O18· xH2O, where x = 0 to 1, can hold single H2O molecules in small structural microcavities and exchange them with the environment with no change in volume. The Cp behavior of the confined H2O, which is characterized by weak van der Waals forces to the aluminosilicate framework, is roughly similar to that of steam at T > 100 K up to moderate T's. Cp is greater than that for ice at T < 100 K. Raman, IR and inelastic neutron scattering measurements show that the H2O molecule is quasi free in both phases. In cordierite, low energy T(H2O) modes occur at ~80 and ~48 cm-1 (Winkler and Hennion, 1994), and possibly at ~31 cm-1 . For beryl, for an external mode T(H2O) at ~ 10 cm-1 is present. The second type of microporous silicate, namely zeolites (those studied are bikitaite Li2[Al2Si4O12]·2H2O, natrolite - Na16[Al16Si24O80]·16H2O, scolecite - Ca8[Al16Si24O80]·24H2O, gmelinite - (Na2,Ca)[Al2Si4O12]·6H2O) are strongly hydrophilic and their intrachannel H2O molecules are hydrogen bonded. Zeolites show measurable changes in volume with loss or gain of H2O. The Cp behavior of H2O in natrolite is similar to that for ice at T < 100 K, but its Cp increases roughly linearly with increasing T and is greater than the Cp of ice at T > 100 K and also for H2O in cordierite at T > 250 K. At 298 K, T(H2O) modes between 45 and 180 cm-1 occur in natrolite and scolecite. Gmelinite shows similar Cp behavior at T < 100 K but anomalously high Cp behavior above 170 K. Conclusions from our investigations are: 1) At T < 200 K, Cp behavior of confined H2O is controlled by low-energy external T(H2O) modes. 2) T(H2O) mode energies reflect weak van-der-Waals to moderately strong hydrogen-bond forces at inner-surfaces. 3) The marked increase in Cp in some zeolites with increasing T indicates a change in hydrogen-bonding behavior from more "ice-like" to increasing "liquid- water-like". It is possible that this "transition" can account for the Cp behavior observed at T > 170 K in gmelinite. 4) Cp and entropy values for confined H2O in silicates cannot be considered similar, as is done in crystal-chemical-based schemes used for calculating thermodynamic properties of H2O-bearing silicates.

Geiger, C. A.; Paukov, I. E.; Kovalevskaya, Y. A.; Kolesov, B. A.

2007-12-01

347

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

348

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

349

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

350

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

351

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

352

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

353

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...

354

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

355

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

356

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 ...

357

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

358

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

359

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

360

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

361

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

362

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

363

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

364

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

365

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

366

Characterisation of crystalline C-S-H phases by X-ray photoelectron spectroscopy  

SciTech Connect

We have prepared a number of crystalline calcium-silicate-hydrate (C-S-H) phases hydrothermally, with calcium-silicon ratios varying from approximately 0.5 (K-phase) to 2.0 (hillebrandite and {alpha}-dicalcium silicate hydrate). The phases were then analysed using X-ray photoelectron spectroscopy (XPS). Increasing calcium-silicon ratios resulted in decreased silicon binding energies. Additionally, changes in the O 1s spectra could be explained in terms of bridging (BO) and nonbridging oxygen (NBO) moieties. Finally, the modified Auger parameter has proved particularly useful in determining the extent of silicate anion polymerisation. Of note also are the apparently unusual spectra for 11 A tobermorite. The silicon and oxygen photoelectron spectra indicate a phase with a lower degree of silicate polymerisation than predicted from its composition. The main contributing factor is the intrinsic disorder within the tobermorite structure. This study has shown how XPS may be used to obtain valuable structural information from C-S-H phases, and our analysis of the crystalline phases is the first step towards the analysis of real C-S-H-based cement systems.

Black, Leon; Garbev, Krassimir; Stemmermann, Peter; Hallam, Keith R.; Allen, Geoffrey C

2003-06-01

367

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.

368

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.

369

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

370

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

371

Design of layered silicate by grafting with metal acetylacetonate for high activity and chemoselectivity in photooxidation of cyclohexane.  

PubMed

We succeeded in the immobilization of Ti(IV) acetylacetonate onto interlayer surfaces of a layered silicate HUS-2 (Hiroshima University Silicate-2, Si20O40(OH)4·4[C5H14NO]) and investigated the photocatalytic acitivity of Ti-incorporated HUS-2 toward the partial oxidation of cyclohexane to cyclohexanol and cyclohexanone under solar light irradiation. XRD, SEM/EDX, (13)C CP and (29)Si MAS NMR and UV-vis measurements of Ti-incorporated HUS-2 confirmed that the isolated tetrahedral Ti species were homogeneously immobilized onto silicate sheets via Si-O-Ti covalent bond and acetylacetonate ligands were removed after calcination. Ti-incorporated HUS-2 showed ca. 100% selectivity for partial cyclohexane oxidation and considerably higher yields (cyclohexanol and cyclohexanone) than TS-1, a typical Ti-containing zeolite. Higher yields were obtained when the calcined Ti-incorporated HUS-2 with a larger amount of the grafted Ti were used. PMID:24617730

Tsunoji, Nao; Ide, Yusuke; Yagenji, Yuya; Sadakane, Masahiro; Sano, Tsuneji

2014-04-01

372

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

373

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

374

The interaction of aluminum with silicic acid in dilute solution and its biological relevance  

SciTech Connect

The affinity of silicic acid, Si(OH){sub 4}, for aluminum is a unique one in chemistry, owing to ionic size, charge, and coordination geometry of the species involved. The chemistry of aluminosilicates generally has been concerned with the solid state (minerals such as clays, feldspars and zeolites), and relatively little attention has been given to the species which exist in solution since aluminosilicates are highly insoluble near neutral pH. However, under dilute conditions the kinetics of colloid formation can be quite slow and the soluble precursors to a solid phase may be reasonably metastable. When equilibrium is approached, the solubility levels are typically 0.05-0.28 {mu}mol/L Al and 18-210 {mu}mol/L Si. These soluble species are usually regarded as simple hydroxyaluminum ions and silicic acid, although it remains arguable as to whether these species may be associated with each other. The formation of a stable soluble specie would allow for molecular aluminosilicates to exist at below saturation levels. So at concentrations above saturation stable aluminosilicates do form (as a part of an insoluble phase), and they may possibly exist at below saturation (as a stable soluble specie). This interaction is then relevant to biology, where human plasma levels (0.06-0.54 {mu}mol/L Al, 14-39 {mu}mol/L Si) (6,7) fall among saturation values. There is a growing concern over the toxic effects of aluminum, but its chemistry with silicic acid has not been addressed. This chemistry is the topic of this study.

Chappell, J.S.; Birchall, J.D. (Imperial Chemicals Industries plc, Cheshire (England))

1988-09-01

375

A Ti L -edge X-ray absorption study of Ti-silicate glasses  

Microsoft Academic Search

A series of titanium silicate glasses along the composition joins SiO2–TiO2, Na2SiO3–TiO2, K2SiO3–TiO2, and CaSiO3–TiO2 have been examined using titanium (Ti) L-edge X-ray absorption near-edge spectroscopy (XANES). XANES spectra were collected at the Canadian Synchrotron Radiation\\u000a Facility (CSRF), University of Wisconsin, Madison, using the Spherical Grating Monochromator (SGM) beamline. Glass spectra\\u000a were compared with spectra obtained from crystalline analogues with

G. S. Henderson; X. Liu; M. E. Fleet

2002-01-01

376

An Observational Test for Shock-induced Crystallization of Cometary Silicates  

NASA Technical Reports Server (NTRS)

Crystalline silicates have been observed in comets and in protostellar nebulae, and there are currently at least two explanations for their formation: thermal annealing in the inner nebula, followed by transport to the regions of cometary formation and in-situ shock processing of amorphous grains at 5 - 10 AU in the Solar Nebula. The tests suggested to date to validate these models have not yet been carried out: some of these tests require a longterm commitment to observe both the dust and gas compositions in a large number of comets. Here we suggest a simpler test.

Nuth, J. A.; Johnson, N. M.

2003-01-01

377

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

378

The Silicate\\/non-silicate distribution of metals in fly ash and its effect on solubility  

Microsoft Academic Search

In a study at DOE's National Energy Technology Laboratory, 32 Class F fly ash samples from pulverized coal (PC) power plants were dissolved in concentrated nitric acid and in hydrofluoric acid to estimate the distribution of metals in non-silicate and silicate matrices. Nineteen cations occurred to some extent in both phases. Using a column leaching method, the release of the

Ann G. Kim; George Kazonich

2004-01-01

379

Residual stresses and phase transformations in Ytterbium silicate environmental barrier coatings  

NASA Astrophysics Data System (ADS)

Due to their high melting temperature, low density, and good thermomechanical stability, silicon-based ceramics (SiC, Si3N4) are some of the most promising materials systems for high temperature structural applications in gas turbine engines. However, their silica surface layer reacts with water vapor contained in combustion environments. The resulting hydroxide layer volatilizes, leading to component recession. Environmental barrier coatings (EBCs) have been developed to shield the substrate from degradation. Next generation coatings for silicon-based ceramics based on ytterbium silicates have shown a promising combination of very low and good thermomechanical properties. The focus of this thesis is threefold: In the first part, phase transformations in plasma sprayed ytterbium silicates were investigated. Plasma sprayed materials are known to contain large amounts of amorphous material. Phase changes during the conversion from amorphous to crystalline materials were investigated as they have been known to lead to failure in many coatings. The second part of this work focused on measuring residual stresses in multilayer EBCs using synchrotron X-ray diffraction (XRD). Strains were resolved spatially, with probe sizes as small as 20 um. Stresses were calculated using mechanical properties of ytterbium silicates, determined with in-situ loading and heating experiments. In-situ and ex-situ heating experiments allowed for the study of changes in stress states that occur in these EBC materials during heating and cooling cycles. Lastly, the interaction of ytterbium silicates with low-melting environmental calcium-magnesium-aluminosilicate (CMAS) glasses was studied. Synchrotron XRD was used to study the influence of CMAS on the stress state in the coating, X-ray computed tomography was used to provide 3D images of coatings, and EDS and TEM analysis were used to study the interactions at the CMAS/ytterbium silicate interface in detail.

Stolzenburg, Fabian

380

Fluorescence spectroscopy of U(VI)-silicates and U(VI)-contaminated Hanford sediment  

NASA Astrophysics Data System (ADS)

Time-resolved U(VI) laser fluorescence spectra (TRLFS) were recorded for a series of natural uranium-silicate minerals including boltwoodite, uranophane, soddyite, kasolite, sklodowskite, cuprosklodowskite, haiweeite, and weeksite, a synthetic boltwoodite, and four U(VI)-contaminated Hanford vadose zone sediments. Lowering the sample temperature from RT to ˜ 5.5 K significantly enhanced the fluorescence intensity and spectral resolution of both the minerals and sediments, offering improved possibilities for identifying uranyl species in environmental samples. At 5.5 K, all of the uranyl silicates showed unique, well-resolved fluorescence spectra. The symmetric O = U = O stretching frequency, as determined from the peak spacing of the vibronic bands in the emission spectra, were between 705 to 823 cm -1 for the uranyl silicates. These were lower than those reported for uranyl phosphate, carbonate, or oxy-hydroxides. The fluorescence emission spectra of all four sediment samples were similar to each other. Their spectra shifted minimally at different time delays or upon contact with basic Na/Ca-carbonate electrolyte solutions that dissolved up to 60% of the precipitated U(VI) pool. The well-resolved vibronic peaks in the fluorescence spectra of the sediments indicated that the major fluorescence species was a crystalline uranyl mineral phase, while the peak spacing of the vibronic bands pointed to the likely presence of uranyl silicate. Although an exact match was not found between the U(VI) fluorescence spectra of the sediments with that of any individual uranyl silicates, the major spectral characteristics indicated that the sediment U(VI) was a uranophane-type solid (uranophane, boltwoodite) or soddyite, as was concluded from microprobe, EXAFS, and solubility analyses.

Wang, Zheming; Zachara, John M.; Gassman, Paul L.; Liu, Chongxuan; Qafoku, Odeta; Yantasee, Wassana; Catalano, Jeff G.

2005-03-01

381

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.

382

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

383

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

384

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

385

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

386

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

387

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

388

Silicate weathering in anoxic marine sediments  

NASA Astrophysics Data System (ADS)

Two sediment cores retrieved at the northern slope of Sakhalin Island, Sea of Okhotsk, were analyzed for biogenic opal, organic carbon, carbonate, sulfur, major element concentrations, mineral contents, and dissolved substances including nutrients, sulfate, methane, major cations, humic substances, and total alkalinity. Down-core trends in mineral abundance suggest that plagioclase feldspars and other reactive silicate phases (olivine, pyroxene, volcanic ash) are transformed into smectite in the methanogenic sediment sections. The element ratios Na/Al, Mg/Al, and Ca/Al in the solid phase decrease with sediment depth indicating a loss of mobile cations with depth and producing a significant down-core increase in the chemical index of alteration. Pore waters separated from the sediment cores are highly enriched in dissolved magnesium, total alkalinity, humic substances, and boron. The high contents of dissolved organic carbon in the deeper methanogenic sediment sections (50-150 mg dm-3) may promote the dissolution of silicate phases through complexation of Al3+ and other structure-building cations. A non-steady state transport-reaction model was developed and applied to evaluate the down-core trends observed in the solid and dissolved phases. Dissolved Mg and total alkalinity were used to track the in-situ rates of marine silicate weathering since thermodynamic equilibrium calculations showed that these tracers are not affected by ion exchange processes with sediment surfaces. The modeling showed that silicate weathering is limited to the deeper methanogenic sediment section whereas reverse weathering was the dominant process in the overlying surface sediments. Depth-integrated rates of marine silicate weathering in methanogenic sediments derived from the model (81.4-99.2 mmol CO2 m-2 year-1) are lower than the marine weathering rates calculated from the solid phase data (198-245 mmol CO2 m-2 year-1) suggesting a decrease in marine weathering over time. The production of CO2 through reverse weathering in surface sediments (4.22-15.0 mmol CO2 m-2 year-1) is about one order of magnitude smaller than the weathering-induced CO2 consumption in the underlying sediments. The evaluation of pore water data from other continental margin sites shows that silicate weathering is a common process in methanogenic sediments. The global rate of CO2 consumption through marine silicate weathering estimated here as 5-20 Tmol CO2 year-1 is as high as the global rate of continental silicate weathering.

Wallmann, K.; Aloisi, G.; Haeckel, M.; Tishchenko, P.; Pavlova, G.; Greinert, J.; Kutterolf, S.; Eisenhauer, A.

2008-06-01

389

Mid-Infrared Spectrum of the Zodiacal Emission: Detection of Crystalline Silicates in Interplanetary Dust  

NASA Technical Reports Server (NTRS)

Within a few astronomical units of the Sun the solar system is filled with interplanetary dust, which is believed to be dust of cometary and asteroidal origin. Spectroscopic observations of the zodiacal emission with moderate resolution provide key information on the composition and size distribution of the dust in the interplanetary space. They can be compared directly to laboratory measurements of candidate materials, meteorites, and dust particles collected in the stratosphere. Recently mid-infrared spectroscopic observations of the zodiacal emission have been made by two instruments on board the Infrared Space Observatory; the camera (ISOCAM) and the spectrophotometer (ISOPHOT-S). A broad excess emission feature in the 9-11 micron range is reported in the ISOCAM spectrum, whereas the ISOPHOT-S spectra in 6-12 microns can be well fitted by a blackbody radiation without spectral features.

Ootsubo, T.; Onaka, T.; Yamamura, I.; Ishihara, D.; Tanabe, T.; Roellig, T. L.

2003-01-01

390

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

391

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

392

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

393

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

394

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

395

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

396

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

397

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

398

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

399

Europium-doped yttrium silicate nanophosphors prepared by flame synthesis  

E-print Network

Europium-doped yttrium silicate nanophosphors prepared by flame synthesis Xiao Qin a,*, Yiguang Ju; accepted 7 November 2006 Available online 22 December 2006 Abstract Europium-doped yttrium silicate (Y2SiO5

Bernhard, Stefan

400

Optical absorption and ionization of silicate glasses Leonid B. Glebov  

E-print Network

Optical absorption and ionization of silicate glasses Leonid B. Glebov School of Optics and hydroxyl), and induced (color centers) absorption of multicomponent silicate glasses in UV, visible and near JR spectral regions are described. Parasitic effects influencing absorption measurements

Glebov, Leon

401

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

402

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

403

Solubility of Zinc Silicate and Zinc Ferrite in Aqueous Solution to High Temperatures  

SciTech Connect

Crystalline zinc silicate, Zn{sub 2}SiO{sub 4}, and zinc ferrite, ZnFe{sub 2}O{sub 4}, were prepared and characterized. The solubilities of these phases were measured using flow-through apparatus from 50 to 350 C in 100 C intervals over a wide range of pH. Both solid phases dissolve incongruently, presumably to form ZnO(s) and Fe{sub 2}O{sub 3}(s) (or the corresponding hydroxide phases at low temperature), respectively. The respective concentrations of zinc(II) and iron(III) matched those of ZnO(cr) and Fe{sub 2}O{sub 3}(s) ({ge}150 C) reported in the literature, whereas the corresponding Si(IV) and Zn(II) concentrations were at least an order of magnitude below the solubility limits for their pure oxide phases. Therefore, the solubility constants for zinc silicate and ferrite were determined with respect to the known solubility constants for ZnO(cr) and Fe{sub 2}O{sub 3}(s) ({ge}150 C), respectively, and the corresponding concentrations of Si(IV) and Zn(II) measured in this study. The results of independent experiments, as well as those reported in the literature provide insights into the mechanism(s) of formation of zinc silicate and ferrite in the primary circuits of nuclear reactors.

Palmer, Donald [ORNL; Anovitz, Lawrence {Larry} M [ORNL

2009-07-01

404

Rapid hydrothermal flow synthesis and characterisation of carbonate- and silicate-substituted calcium phosphates  

PubMed Central

A range of crystalline and nano-sized carbonate- and silicate-substituted hydroxyapatite has been successfully produced by using continuous hydrothermal flow synthesis technology. Ion-substituted calcium phosphates are better candidates for bone replacement applications (due to improved bioactivity) as compared to phase-pure hydroxyapatite. Urea was used as a carbonate source for synthesising phase pure carbonated hydroxyapatite (CO3-HA) with ?5?wt% substituted carbonate content (sample 7.5CO3-HA) and it was found that a further increase in urea concentration in solution resulted in biphasic mixtures of carbonate-substituted hydroxyapatite and calcium carbonate. Transmission electron microscopy images revealed that the particle size of hydroxyapatite decreased with increasing urea concentration. Energy-dispersive X-ray spectroscopy result revealed a calcium deficient apatite with Ca:P molar ratio of 1.45 (±0.04) in sample 7.5CO3-HA. For silicate-substituted hydroxyapatite (SiO4-HA) silicon acetate was used as a silicate ion source. It was observed that a substitution threshold of ?1.1?wt% exists for synthesis of SiO4-HA in the continuous hydrothermal flow synthesis system, which could be due to the decreasing yields with progressive increase in silicon acetate concentration. All the as-precipitated powders (without any additional heat treatments) were analysed using techniques including Transmission electron microscopy, X-ray powder diffraction, Differential scanning calorimetry, Thermogravimetric analysis, Raman spectroscopy and Fourier transform infrared spectroscopy. PMID:22983020

Knowles, Jonathan C; Rehman, Ihtesham; Darr, Jawwad A

2013-01-01

405

Progress in understanding the structure and thermodynamics of calcium silicate hydrates  

SciTech Connect

A program has been designed to support the prediction of cement degradation and the chemistry of water in contact with cement, over extended periods of time (e.g., 10,000 y). This multidisciplinary experimental and computer modeling investigation is intended to characterize the structural and thermodynamic properties of crystalline phases found in cement at elevated temperature. Many of these crystalline phases my be hydrated. The hydration state of these phases must be known to the interpret experimentally obtained thermodynamic data, to evaluate the stability of hydrated phases and to estimate long-term water availability, such as would be required for prediction of the radioactive-waste repository`s lifetime. The parts of the program associated with assessing and predicting dehydration/ rehydration behavior are described in this paper. (1) identification of phases present in standardized grout mixtures exposed to elevated temperatures; (2) mechanistic and thermodynamic analysis of the hydration/ dehydration behavior of hydrated calcium silicates as a function of temperature, pressure, and relative humidity; and (3) measurements of thermodynamic data for hydrated calcium silicates.

Meike, A.; Bruton, C.J.; Viani, B.E. [Lawrence Livermore National Lab., CA (United States); Onofrei, M. [Atomic Energy of Canada Ltd., Pinawa, MB (Canada). Whiteshell Nuclear Research Establishment

1994-02-01

406

Structure, properties and applications of phenyl-modified silicate films  

Microsoft Academic Search

Organically modified silicate films prepared by sol-gel techniques have been studied. The silicate structure has been modified by phenyl radicals. The films were prepared by cohydrolysis in various proportions of tetraethyloxysilane and phenyl triethoxysilane or diphenyl diethylhexyloxy diethoxydisiloxane. It is shown that phenyl radicals introduced into the silicate network reduce cross-linking in polymer structure, their density and hydroxyl contents. These

Konstantin A. Vorotilov; Vladimir A. Vasiljev; Michael V. Sobolevsky; Natalia I. Afanasyeva

1996-01-01

407

Inorganic Plant Nutrients: Nitrogen, Phosphorus, Silicate Introduction  

E-print Network

. The biogeochemical cycle of nitrogen is further complicated by the different forms in which nitrogen can occurLab 3: Inorganic Plant Nutrients: Nitrogen, Phosphorus, Silicate Introduction Compounds of nitrogen processes. Concentrations of nitrogen and phosphorus, on the other hand, are highly dynamic because they may

Jochem, Frank J.

408

Dynamic Fatigue of a Titanium Silicate Glass  

NASA Technical Reports Server (NTRS)

A dynamic fatigue study was performed on a Titanium Silicate Glass in order to assess its susceptibility to delayed failure. Fracture mechanics techniques were used to analyze the results for the purpose of making lifetime predictions for optical elements made from this material. The material has reasonably good resistance (N=23 to stress corrosion in ambient conditions).

Tucker, Dennis S.; Nettles, Alan T.; Cagle, Holly A.; Smith, W. Scott (Technical Monitor)

2002-01-01

409

Chemical Vapor Deposition on Chabazite (CHA) Zeolite Membranes for Effective Post-Combustion CO2 Capture.  

PubMed

Chabazite (CHA) zeolites with a pore size of 0.37 × 0.42 nm(2) are expected to separate CO2 (0.33 nm) from larger N2 (0.364 nm) in postcombustion flue gases by recognizing their minute size differences. Furthermore, the hydrophobic siliceous constituent in CHA membranes can allow for maintaining the CO2/N2 separation performance in the presence of H2O in contrast with the CO2 affinity-based membranes. In an attempt to increase the molecular sieving ability, the pore mouth size of all silica CHA (Si-CHA) particles was reduced via the chemical vapor deposition (CVD) of a silica precursor (tetraethyl orthosilicate). Accordingly, an increase of the CVD treatment duration decreased the penetration rate of CO2 into the CVD-treated Si-CHA particles. Furthermore, the CVD process was applied to siliceous CHA membranes in order to improve their CO2/N2 separation performance. Compared to the intact CHA membranes, the CO2/N2 maximum separation factor (max SF) for CVD-treated CHA membranes was increased by ?2 fold under dry conditions. More desirably, the CO2/N2 max SF was increased by ?3 fold under wet conditions at ?50 °C, a representative temperature of the flue gas stream. In fact, the presence of H2O in the feed disfavored the permeation of N2 more than that of CO2 through CVD-modified CHA membranes and thus, contributed to the increased CO2/N2 separation factor. PMID:25479409

Kim, Eunjoo; Lee, Taehee; Kim, Hyungmin; Jung, Won-Jin; Han, Doug-Young; Baik, Hionsuck; Choi, Nakwon; Choi, Jungkyu

2014-12-16

410

Thermoset polymer-layered silicic acid nanocomposites  

NASA Astrophysics Data System (ADS)

Nanocomposites are formed when phase mixing occurs on a nanometer length scale. Due to the improved phase morphology and interfacial properties, nanocomposites exhibit mechanical properties superior to conventional composites. Toyota researchers first demonstrated that organoclay could be exfoliated in a nylon-6 matrix to greatly improve the thermal and mechanical properties of the polymer, which has resulted in a practical application in the automobile industry. A great deal of research has been conducted on organic-inorganic hybrid composites in which smectite clays are used as reinforcement agents. However, little work has been devoted to derivatives of other layered inorganic solids. In the present work, the first examples of organic polymer-layered silicic acid nanocomposites have been prepared by formation of a cured epoxy polymer network in the presence of organo cation exchange forms of magadiite. The exfoliation of silicate nanolayers in the epoxy matrix was achieved by in-situ intragallery polymerization during the thermosetting process. In general, the tensile properties, solvent resistance, barrier properties and chemical stability of the polymer matrix are greatly improved by the embedded silicate nanolayers when the matrix is flexible (sub-ambient Tg). The improvement of properties are dependent on the silicate loading, the degree of nanolayer separation and interfacial properties. Interestingly, the exfoliation also affects the polymer elasticity in a favorable way. The mechanism leading to nanocomposite formation is proposed. One exfoliated epoxy-magadiite nanocomposite/composition possessed unique transparent optical properties. The exfoliation chemistry was successfully extended to the other members of the layered silicic acid family. A new approach also was developed to prepare thermoset epoxy polymer-layered silicate nanocomposites in which curing agents can be directly intercalated into the intragallery without the need for alkylammonium ions on the exchange sites. This new development has resulted in a greater improvement in the overall properties of thermoset polymer-clay nanocomposites. The exfoliation chemistry was extended further to other thermoset silicone polymer systems. The new polysiloxane-layered silicic acid nanocomposites were prepared with promising mechanical properties. Some fundamental chemistry and physics issues regarding nanocomposite formation were elucidated by this research work, particularly with regard to the relationship of microstructure and interfacial factors to the mechanical properties of the nanocomposites.

Wang, Zhen

411

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

412

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

413

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

414

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

415

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

416

Is a 'Late Veneer' Necessary? Answers From Metal-Silicate Partitioning of Te, Se, and S  

NASA Astrophysics Data System (ADS)

Chondrite-normalized mantle abundances of Te, Se, and S show depletions from the Planetary Volatility Trend (McDonough and Sun, 1995). This is likely due to their siderophile behavior under reducing conditions (Kilburn and Wood, 1997), resulting in strong partitioning into the core-forming Fe-Ni liquid. A mass balance calculation using Te, Se, and S concentrations in C1-chondrites and a modeled primitive mantle shows similar depletions for each element, with core/mantle "partitioning" of about 100 (McDonough and Sun, 1995). Values for Se and Te relative to S used in this estimate are consistent with those measured in sulfide globules from the upper mantle (Hattori et al., 2001). Experiments have been done to investigate whether this depletion could be achieved solely by equilibrium metal-silicate partitioning at the P-T-fO2 conditions relevant to core formation. If experimental results match the estimated Dcore-mantle, this could reflect either a single P-T condition at the base of a magma ocean where metallic liquid ponded, or an average P-T condition covering a depth range within which metallic liquid droplets rained through semi-crystalline silicate. If the results are discrepant, the abundance of Te, Se, and S were disrupted after initial equilibrium partitioning. Higher experimental DTe,Se,S necessitates the addition of chalcophile-rich material to the mantle after core formation (i.e. a 'late veneer') and lower experimental DTe,Se,S requires removal of chalcophiles from the mantle, perhaps in a late 'Hadean sulfide matte' (Wood and Halliday, 2003). Liquid metal-liquid silicate partitioning experiments were performed using both piston-cylinder and multi-anvil presses over a range of pressure (1-12 GPa) and temperature (1835-2135°C). Powdered oxide and metal added in 50:50 proportion was contained within MgO crucibles. Oxygen fugacity was varied by adding different amounts of Si to the starting material. Experiments ranged from -7 to -0.5 log units below the iron-wüstite buffer (IW). Major elements in both quenched metal and silicate were determined by EMPA while Te and Se abundance in the quenched silicate portion was measured using LA-ICP-MS at the University of Toronto. At constant P and T, all three metal-silicate partition coefficients increase with increasing fO2. Te and S are the most siderophile, followed by Se. The presence of 5-10 wt% S increased both DTe and DSe by a factor of three. At 2.9 GPa, 1960°C and log fO2 between IW-4 and IW-1.5, metal- silicate partitioning of the three elements converge to 100, matching the observed core-mantle partitioning. Previously, it was shown that both DS and DSe are positively correlated with P while increased T lowers DS (Li and Agee, 1996; Li, 2000). After applying these corrections and extrapolating our data to the estimated conditions of core formation (P=25-40 GPa; T=2000-3500°C; e.g. Li and Agee, 1996; Righter et al., 1997), the point of equal metal- silicate partitioning of Te, Se, and S is only raised by a factor of 3. Consequently, the observed core-mantle partitioning of Te, Se, and S is consistent with high temperature equilibrium within a magma ocean, obviating the need for a 'late veneer'. Chalcophile element (including Pb) loss to the core with the separation of a Hadean sulfide 'matte' would have further depleted the mantle. It would be quite fortuitous if a 'late veneer' refertilized the mantle to match the expected equilibrium abundances prescribed by metal-silicate partitioning. This result is consistent with conclusions based on the metal-silicate partitioning behavior of other elements, for instance Ni, Co, and Pt.

Rose, L. A.; Brenan, J. M.

2006-05-01

417

Grain Growth and Silicates in Dense Clouds  

NASA Technical Reports Server (NTRS)

Interstellar silicates are likely to be a part of all grains responsible for visual extinction (Av) in the diffuse interstellar medium (ISM) and dense clouds. A correlation between Av and the depth of the 9.7 micron silicate feature (measured as optical depth, tau(9.7)) is expected if the dust species are well 'mixed. In the di&se ISM, such a correlation is observed for lines of sight in the solar neighborhood. A previous study of the silicate absorption feature in the Taurus dark cloud showed a tendency for the correlation to break down at high Av (Whittet et al. 1988, MNRAS, 233,321), but the scatter was large. We have acquired Spitzer Infrared Spectrograph data of several lines of sight in the IC 5 146, Barnard 68, Chameleon I and Serpens dense clouds. Our data set spans an Av range between 2 and 35 magnitudes. All lines of sight show the 9.7 micron silicate feature. The Serpens data appear to follow the diffuse ISM correlation line whereas the data for the other clouds show a non-linear correlation between the depth of the silicate feature relative to Av, much like the trend observed in the Taurus data. In fact, it appears that for visual extinctions greater than about 10 mag, tau(9.7) begins to level off. This decrease in the growth of the depth of the 9.7 micron feature with increasing Av could indicate the effects of grain growth in dense clouds. In this poster, we explore the possibility that grain growth causes an increase in opacity (Av) without causing a corresponding increase in tau(9.7).

Pendeleton, Yvonne J.; Chiar, J. E.; Ennico, K.; Boogert, A.; Greene, T.; Knez, C.; Lada, C.; Roellig, T.; Tielens, A.; Werner, M.; Whittet, D.

2006-01-01

418

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

419

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

420

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

421

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

422

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

423

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

424

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

425

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

426

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

427

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

428

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

429

Dry plasma processing for industrial crystalline silicon solar cell production  

NASA Astrophysics Data System (ADS)

This paper gives an overview on the standard crystalline silicon solar cell manufacturing processes typically applied in industry. Main focus has been put on plasma processes which can replace existing, mainly wet chemical processes within the standard process flow. Finally, additional plasma processes are presented which are suited for higher-efficient solar cells, i.e. for the “passivated emitter and rear cell” concept (PERC) or the “heterojunction with intrinsic thin layer” approach (HIT). Plasma processes for the deposition of thin dielectric or semiconducting layers for surface passivation, emitter deposition or anti-reflective coating purposes are presented. Plasma etching processes for the removal of phosphorus silicate glass or parasitic emitters, for wafer cleaning and masked and mask-free surface texturisation are discussed.

Hofmann, M.; Rentsch, J.; Preu, R.

2010-10-01

430

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

431

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

432

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