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Zeolite
Kinds of Zeolite Terms modified by Zeolite Selected AbstractsInterplay of Properties and Functions upon Introduction of Mesoporosity in ITQ-4 ZeoliteADVANCED FUNCTIONAL MATERIALS, Issue 9 2010Danny Verboekend Abstract The introduction of mesoporosity in zeolites is often directly coupled to changes in their overall catalytic performance without the detailed assessment of other key functions required for the rational design of the catalytic process such as accessibility, adsorption, and transport. This study presents an integrated approach to study property,function relationships in hierarchical zeolites. Accordingly, desilication of the 1D ITQ-4 zeolite in alkaline medium is applied to develop different degrees of mesoporosity. Along with porosity modification, significant changes in composition, structure, and acidity occur. Relationships are established between the physicochemical properties of the zeolites and their characteristics in the adsorption and elution of light hydrocarbons (C2 to C5, alkanes and alkenes) as well as in the catalytic activity in low-density polyethylene (LDPE) pyrolysis. The recently introduced hierarchy factor can appropriately relate porosity changes to catalytic performance. [source] Hexagonal Network Organization of Dye-Loaded Zeolite,L Crystals by Surface-Tension Driven Autoassembly,ADVANCED FUNCTIONAL MATERIALS, Issue 17 2006S. Yunus Abstract Highly fluorescent dye-loaded zeolite,L crystals, approximately 1.4,,m long and 650,nm in diameter, are organized in a hexagonal network by a surface-tension-driven autoassembly process. A polydimethylsiloxane (PDMS) film presenting a trigonal ordering of spherical protuberances, including a polystyrene (PS) hexagonal network occupying their interstices, is chosen as the platform for the assembly. The overall wettability and the difference in surface tension between PDMS and PS surfaces are found to offer good conditions for ordering micrometric dye-loaded zeolite,L crystals in a 2D hexagonal network. The resulting film displays a regular hexagonal pattern of polarized fluorescence, reflecting the polarization properties of the dye molecules inserted in the parallel nanochannels of the zeolites. [source] Energy Collection, Transport, and Trapping by a Supramolecular Organization of Dyes in Hexagonal Zeolite Nanocrystals,ADVANCED FUNCTIONAL MATERIALS, Issue 2 2006C. Minkowski Abstract The incorporation of guest molecules into the cavities of molecular sieves leads to a large variety of highly interesting materials. Zeolite,L,an aluminosilicate with one-dimensional channels of open diameter 7.1,Å,is a very versatile material for building highly organized host,guest systems. We present materials where organic dye molecules have been incorporated into the channels of zeolite,L by means of diffusion, to build artificial photonic antenna systems. The channel entrance can be plugged by adding closure molecules that then connect the guest molecules inside with materials or molecules outside of the zeolite channels, since they can act as extensions of the interior of the zeolite crystal. The photophysical processes taking place in such dye-loaded zeolite,L antennae can be studied either on single-micrometer- or submicrometer-sized crystals or on crystals dispersed in a solvent or coated as thin layers on a support. The energy-transfer process occurring is of the Förster-type, and its transfer rate can be tuned by separating the donor dyes and the acceptor dyes locally by varying amounts of spacer molecules. The distribution of the dye molecules and empty sites within a zeolite crystal has been modeled by means of a Monte Carlo simulation. The Förster energy migration and transfer steps are described as a random walk. [source] Synthesis and Characterization of a Composite Zeolite,Metglas Carbon Dioxide Sensor,ADVANCED FUNCTIONAL MATERIALS, Issue 7 2005G. Giannakopoulos Abstract The synthesis of a faujasite,Metglas composite material that can be used in gas-sensing applications is presented. A continuous faujasite film was synthesized on a Metglas magnetoelastic strip using the secondary growth method. The ability of the new composite to remotely sense carbon dioxide in a nitrogen atmosphere at room temperature over a wide range of concentrations is demonstrated by monitoring the changes in the resonance frequency of the strip. The novel sensor combines the electromagnetic properties of the magnetoelastic material with the adsorption properties of the faujasite crystals. Experiments performed over a period of a few months showed that the composite sensor remained fully operational, thus indicating its long-term stability. Furthermore, the present work demonstrates that a zeolite,Metglas composite can be used as a sensor of an analyte in a mixture as long as it adsorbs selectively larger amounts of the particular analyte than other compounds present in the mixture. [source] Kinetics of liquid phase synthesis of ethyl tert -butyl ether from tert -butyl alcohol and ethanol catalyzed by ,-zeolite supported on monolithINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 5 2002S. Assabumrungrat This paper compared the performance of ,-zeolite and Amberlyst-15 catalysts on a liquid phase synthesis of ethyl tert -butyl ether (ETBE) from ethanol (EtOH) and tert -butyl alcohol (TBA) ,-Zeolite was synthesized and deposited on monolith support. Its structure was confirmed by an XRD measurement and its composition was analyzed by an XRF measurement. It was found that even though the catalytic activity of ,-zeolite was lower than that of Amberlyst-15, the selectivity of ETBE was much higher than that of Amberlyst-15, resulting in almost the same level of ETBE yield. The dehydration of TBA to isobutene (IB) was the major side reaction. The kinetic study of the reaction catalyzed by ,-zeolite supported on monolith was carried out by using a semibatch reactor. The effect of external mass transfer was investigated by varying stirring speeds. The activity-based rate expressions were developed taking into account of water inhibition. Three temperature levels of 323, 333, and 343 K were performed in the study to obtain the parameters in the Arrhenius's equation and the Van't Hoff's equation. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 292,299, 2002 [source] FI Catalysts: A Molecular Zeolite for Olefin PolymerizationADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2010Haruyuki Makio Abstract A bis(phenoxyimine) group 4 transition metal catalyst (now known as FI catalysts) can discern ethylene from a mixture of ethylene and propylene at more than 99% selectivity. Denisty function theory (DFT) calculations revealed a spatially confined reaction site in the transition states of the migratory insertion which is just the right size for an ethylene molecule but too small for a propylene one. The substituents adjacent to the phenoxy-oxygens are of crucial importance in developing the size/shape-selectivity. [source] The Synthesis of an Extra-Large-Pore Zeolite with Double Three-Ring Building Units and a Low Framework Density,ANGEWANDTE CHEMIE, Issue 29 2010Jiuxing Jiang Weit geöffnet: Mithilfe von Hochdurchsatztechniken wurde ein Zeolith mit 18×12×12-Ring-Porensystem erhalten (siehe Bild). Das Material hat die niedrigste Gerüstdichte aller vollständig verbundenen Zeolithe auf Siliciumoxidbasis; außerdem handelt es sich um das erste Gerüst mit doppelten Dreierringen als Strukturmotiv. [source] Orienting Zeolite,L Microcrystals with a Functional Linker,ANGEWANDTE CHEMIE, Issue 8 2010Yu Wang Farbenfroh: Durch Anordnen von Zeolith-L-Kristallen zu lumineszierenden makroskopischen Strukturen entstehen dichte und homogene funktionelle Monoschichten, die stabil und hochgradig organisiert sind (siehe Bild). Die Farbe der Lumineszenz kann eingestellt werden, indem man Zahl und Art der Lanthanoidionen in der Verbindungseinheit variiert, die Gastspezies in den Kanälen des Zeoliths austauscht oder die Anregungswellenlänge wechselt. [source] Probing Photocatalytic Active Sites on a Single Titanosilicate Zeolite with a Redox-Responsive Fluorescent Dye,ANGEWANDTE CHEMIE, Issue 2 2010Takashi Tachikawa Dr. Richtig belichtet: Laut In-situ-Fluoreszenzbildgebung einer photokatalytischen Oxidation mit einem redoxempfindlichen Fluoreszenzfarbstoff (siehe Bild, grün) erhöht die Behandlung von Titanosilicat-Einkristallen mit Säure die Adsorptions- und Reaktionseffizienz sowie die Heterogenität der photokatalytischen Aktivität der Kristalle signifikant. Zudem fungieren Kristalldefekte bei der photokatalytischen Reaktion als reaktive Zentren. [source] Diversification of RTH-Type Zeolite and Its Catalytic Application,ANGEWANDTE CHEMIE, Issue 52 2009Toshiyuki Yokoi Dr. Metall macht's möglich: RTH-Zeolithe (siehe Bild) haben eine attraktive poröse Struktur, ihre Zusammensetzung lässt sich aber nur bedingt variieren. Metallosilicate mit RTH-Topologie sind nun über zwei Wege zugänglich; bei einem davon kann sogar auf strukturbestimmende Agentien verzichtet werden. So erhaltene Al-haltige RTH-Zeolithe waren wirksame Katalysatoren für die hoch selektive Umwandlung von Methanol in Propen. [source] PST-1: A Synthetic Small-Pore Zeolite that Selectively Adsorbs H2,ANGEWANDTE CHEMIE, Issue 36 2009Jiho Shin Appetit auf 'was Kleines: Ein synthetischer Kaliumgallosilicat-Natrolith mit einem Si/Ga-Verhältnis von 1.28 (PST-1; siehe Bild: Ga,Si,grau, O,rot, K,rosa) adsorbiert selektiv kleine Gase, insbesondere H2, und bevorzugt diese gegenüber den größeren Ar oder CO2. Durch seine erstaunlich leichte Dehydration und seine hohe thermische Beständigkeit bietet sich PST-1 für Prozesse zur schnellen und selektiven Abtrennung von H2 oder He an. [source] A New, Yet Familiar, Lamellar ZeoliteCHEMCATCHEM, Issue 3 2010Michael Tsapatsis Prof. Compulsive layers: Lamellar zeolites are crystalline layered materials with porosity within the layers. A recent breakthrough regarding the synthesis of a new lamellar zeolite with the well-known ZSM-5 structure is highlighted in light of previous work on lamellar zeolites and the emerging applications of hierarchical zeolites and zeolitic layers, which include heterogeneous catalysis and zeolite membranes. [source] Kinetic Reaction Models for the Selective Reduction of NO by Methane over Multifunctional Zeolite-based Redox CatalystsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 12 2004T. Sowade Abstract Kinetic measurements of the selective catalytic reduction (SCR) of NO by methane were performed over CeO2/H-ZSM-5, In-ZSM-5, and CeO2/In-ZSM-5 catalysts. The parameter space covered NO, CH4, and O2 concentrations varying from 250 to 1000 ppm, from 500 to 2000 ppm, and from 0.5 to 10,vol.-%, respectively, space velocities between 5000 and 90000 h,1 and temperatures between 573 and 873 K depending on the catalyst activities. With CeO2/In-ZSM-5 an additional series of measurements was performed with moistened feed gas (0.5,10,vol.-% H2O). On the basis of a pseudo-homogeneous, one-dimensional fixed-bed reactor model, the data were fitted to a kinetic model that includes power rate laws for the reduction of NO and for the unselective total oxidation of methane. From analyses of isothermal data sets, almost all reaction orders were found to vary significantly with changing temperature, which indicates that the simple kinetic model cannot reflect the complex reaction mechanism correctly. Nevertheless, the data measured with In-ZSM-5 could be modeled with good accuracy over a wide range of reaction temperatures (150 K) while the accuracy was less satisfactory with the remaining data sets, in particular for data with the moist feed over CeO2/In-ZSM-5. With the latter catalyst it was not possible to represent the data measured in dry and in moist feed in a single model even upon confinement to fixed reaction temperatures. A comparison of the separate models established showed strong changes in the reaction orders in the presence of water, which occur apparently already at a very low water content (,,0.5,vol.-%). The kinetic parameters found are in agreement with earlier conclusions about the reaction mechanisms. With In-ZSM-5, both reaction orders and the activation energy show a rate-limiting influence of NO oxidation on the NO reduction path which is removed by the presence of the CeO2 promoter. A difference in the reaction mechanism over CeO2/In-ZSM-5 and CeO2/H-ZSM-5 is reflected in different kinetic parameters. The differences of the kinetic parameters between dry-feed and moist-feed models for CeO2/In-ZSM-5 reflect adsorption competition between the reactants and water. [source] Crystal Structure of the New Layer Silicate RUB-39 and Its Topotactic Condensation to a Microporous Zeolite with Framework Type RRO.CHEMINFORM, Issue 43 2007Y. X. Wang Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Structure and Catalytic Function of Re-Oxo Species Grafted onto H-MFI Zeolite by Sublimation of Re2O7.CHEMINFORM, Issue 12 2007Howard S. Lacheen Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] The Topotactic Conversion of a Novel Layered Silicate into a New Framework Zeolite.CHEMINFORM, Issue 49 2004Takuji Ikeda Abstract For Abstract see ChemInform Abstract in Full Text. [source] Mechanism of Ozone-Promoted Uptake of NO2 by a Si-Rich H-Type Zeolite.CHEMINFORM, Issue 43 2004Arkadiy Gal Abstract For Abstract see ChemInform Abstract in Full Text. [source] Selective Removal of the N-(tert-Butoxycarbonyl) Protecting Group Using H-, Zeolite.CHEMINFORM, Issue 36 2004Vasudha H. Tillu Abstract For Abstract see ChemInform Abstract in Full Text. [source] A DFT Study of the Acidity of Ultrastable Y Zeolite: Where Is the Broensted/Lewis Acid Synergism?CHEMINFORM, Issue 32 2004Claudio J. A. Mota No abstract is available for this article. [source] Sn-, Zeolite as Diastereoselective Water-Resistant Heterogeneous Lewis Acid Catalyst for Carbon,Carbon Bond Formation in the Intramolecular Carbonyl,Ene Reaction.CHEMINFORM, Issue 29 2004Avelino Corma Abstract For Abstract see ChemInform Abstract in Full Text. [source] Disproportionation of an Element in a Zeolite.CHEMINFORM, Issue 52 2003Part 2. Abstract For Abstract see ChemInform Abstract in Full Text. [source] Facile and Selective Deprotection of Allyl Esters Catalyzed by H-, Zeolite.CHEMINFORM, Issue 50 2003Rajesh K. Pandey No abstract is available for this article. [source] ChemInform Abstract: Allylic Oxidation of Olefins in the Presence of Cu-Na-HSZ-320 Zeolite as Reusable Solid Catalyst.CHEMINFORM, Issue 9 2001Silvia Carloni Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] A Mononuclear Cyclopentadiene,Iron Complex Grafted in the Supercages of HY Zeolite: Synthesis, Structure, and ReactivityCHEMISTRY - A EUROPEAN JOURNAL, Issue 28 2007Jinlin Long Abstract The reaction of ferrocene with the acidic hydroxy groups in the supercages of zeolite HY dehydrated at 673,K and the reactivity of the resultant surface species towards CO and O2 were investigated by temperature-programmed decomposition (TPD) and reduction (TPR) and IR, X-ray absorption fine structure analysis (XAFS), and X-ray photoelectron (XP) spectroscopy. In situ FTIR, TPD, TPR, and chemical analysis reveal that the Cp2Fe molecule adsorbed on the zeolite surface loses one cyclopentadienyl group under vacuum at 423,K, which leads to the formation of a well-defined mononuclear surface Fe-C5H6 complex grafted to two acidic sites and one (Si-O-Si) unit, as confirmed by the lack of Fe,Fe contributions in the EXAFS spectra. Each iron atom is coordinated, on average, to three oxygen atoms of the zeolite surface with a FeO distance of 2.00,Å and to five carbon atoms with a FeC distance of 2.09,Å. IR spectra indicate that the cyclopentadiene,iron species grafted on the surface of the zeolite is quite stable in vacuo or under an inert or hydrogen atmosphere below 423,K, and is also relatively stable under oxygen at room temperature. However, the cyclopentadiene ligand readily reacts with CO to form a compound containing carbonyl at 323,K, and even at room temperature. The single carbonyl band in the IR spectra provides evidence for the nearly uniform formation of a cyclopentadiene,iron species on the surface of the zeolite. [source] Significant Influence of Zn on Activation of the C-H Bonds of Small Alkanes by Brønsted Acid Sites of Zeolite,CHEMPHYSCHEM, Issue 17 2008Alexander G. Stepanov Prof. Abstract Herein, we analyze earlier obtained and new data about peculiarities of the H/D hydrogen exchange of small C1,n -C4 alkanes on Zn-modified high-silica zeolites ZSM-5 and BEA in comparison with the exchange for corresponding purely acidic forms of these zeolites. This allows us to identify an evident promoting effect of Zn on the activation of CH bonds of alkanes by zeolite Brønsted sites. The effect of Zn is demonstrated by observing the regioselectivity of the H/D exchange for propane and n- butane as well as by the increase in the rate and a decrease in the apparent activation energy of the exchange for all C1,n -C4 alkanes upon modification of zeolites with Zn. The influence of Zn on alkane activation has been rationalized by dissociative adsorption of alkanes on Zn oxide species inside zeolite pores, which precedes the interaction of alkane with Brønsted acid sites. [source] Formation of SnO2 Nanoparticles on External Surface of NaY ZeoliteCHINESE JOURNAL OF CHEMISTRY, Issue 4 2005Xu Xiao-Wen Abstract Tin dioxide nanoparticles of 5 nm in size were prepared on NaY zeolite external surface by impregnation of SnCl2 solution and subsequent calcination at 623 K. A SnO2 -NaY based chemical sensor for detecting H2 was demonstrated. [source] Preparation and Charactrization of Fibrous Crystals of Boron-containing MTW-type ZeoliteCHINESE JOURNAL OF CHEMISTRY, Issue 2 2004Mao-Ying Song Abstract Fibrous crystals of boron-containing MTW-type zeolite have been hydrothermally synthesized in B2O3 -SiO2 -HF-H2O gel system at 170 °C in 20 to 28 d by using 1, 4-diazabicyclo[2.2, 2]octane (DABCO) and methylamine as the co-template, and characterized with XRD, SEM, TEM, HRTEM and SAED. The results of characterizations show that B atoms are incorporated into the zeolite framework as tetrahedron of B(OSi)4. The fibrous single crystals of 5,50 ,m in length and 100,500 nm in width inter-grow along the c -axis of the zeolite, and the one dimension 12 oxygen ring channels are perpendicular to the fibber axis. [source] Electroanalytical Applications of Microporous Zeolites and Mesoporous (Organo)Silicas: Recent TrendsELECTROANALYSIS, Issue 7 2008Alain WalcariusArticle first published online: 10 MAR 200 Abstract Microporous zeolites and ordered mesoporous (organo)silicas have been widely used as electrode modifiers because of their attractive properties (ion exchange and size selectivity of zeolites, well ordered nanoreactors containing a high number of widely accessible active centers in mesoporous (organo)silicas). These properties have been intelligently combined to selected redox processes to improve the response of the resulting modified electrodes or to design novel electrochemical detection schemes. This up-to-date review provides the recent advances made in the electroanalytical applications of zeolite modified electrodes and discusses the interest of ordered mesoporous (organo)silica materials in electroanalysis. [source] Cultivation Optimization of Insect-Pathogenic Fungi PaecUomyces lilacinus HY-4 to Soil-pest Adoretus tenuimaculatusENTOMOLOGICAL RESEARCH, Issue 3 2002Eun Young SUH ABSTRACT A new insect pathogenic fungi, Paecilomyces licacinus HY-4 that was isolated from soil sample, showed biological activity to Chestnut Brown Chafer, pest of golf course. The culture condition for the fungi P. lilacinus HY-4 was optimized through statistical approach for the mass production. According th the bioassay on the pest, the insecticidal activity reached up to 30%, and positive factor for the production of the fungi was zeolite with 97.5% of significance. [source] Enhancing the Porosity of Mesoporous Carbon-Templated ZSM-5 by DesilicationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 33 2008Martin S. Holm Abstract A tunable desilication protocol applied on a mesoporous ZSM-5 zeolite synthesized by carbon-templating is reported. The strategy enables a systematic manufacture of zeolite catalysts with moderate to very high mesoporosities. Coupling carbon-templating and desilication thus allow for more than a doubling of the original mesopore volume and mesopore surface area. The porosity effect arising from various treatment times and base amounts in the media has beenthoroughly mapped. Initially, small mesopores are created, and as desilication strength increases the average mesopore size enhances. Crystallinity of the treated samples is retained, and electron microscopy indicates solely intracrystalline mesoporosity.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] | ||||||||||||||||||||||||||||||||||||||||||||||