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Showing 1 to 20 of 213 for “"Zeolites"”.
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Base catalysis by alkali modified zeolites
… of various alkali exchanged, faujasite-type zeolites are explored. It is found that upon impregnation of CsNaY with cesium hydroxide or cesium acetate, acetone production (normally attributed to base sites) is promoted by an order of magnitude above the untreated (not impregnated) CsNaY …
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Microwave synthesis and occlusion reactions of zeolites
… of this thesis is dedicated to the synthesis of zeolites A (LTA), X (FAU), Y, (FAU) and rho (RHO) in a microwave oven. Results have demonstrated that when zeolitic gels are heated in a microwave oven they yield zeolite crystals far quicker than when heated in a conventional oven. This is in part …
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Studies of Some Catalytic Properties of Zeolites
The use of Yetype zeolites as catalysts for the vapour phase Beckmann rearrangement of alicyclic oximes has been investigated, particularly for the conversion of cyclopentanone oxime to 2-piperidone. The rearrangements of cyclopentanone oxime and cyclohexanone oxime were studied spectroscopically, …
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Exafs Studies of Transition Metal Exchanged Zeolites
The extended X-ray absorption fine structure (EXAFS) that appears on the high energy side of the absorption edge of an element has been shown to be due to modifications to the final state wave function of the ejected photoelectron from the absorbing atom by its near neighbors.('1,2,3) Consequently, …
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Catalytic conversion of Ethylbenzene over acid zeolites
… was employed to compare the acidity of various zeolites, viz. lanthanum/sodium-exchanged zeolite Y (LaNaY-72), hygrogen/sodium-exchanged zeolote Y (LZY-52, LZY-62, LZY-82), hydrogen-exchanged zeolite Beta (H-BEA-15, H-BEA-25) and hydrogen-exchanged ZSM-5 (H-MFI-45).
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Investigating transport through sub-nanometer zeolites pores
… In this thesis, we synthesized MFI (Mobil Five) zeolites that have uniform, well-defined pores of ~~ 5.5 Å and experimentally investigated the transport across these sub-nanometer pores. This porous structure serves as a model framework to experimentally investigate water and salt transport and …
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The diffusion mechanism of hydrocarbons in zeolites
Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1990.
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Rhodium zeolites as catalysts for hydrodesulfurization reactions
… This study investigated rhodium incorporated zeolites as catalysts for thiophene hydrodesulfurization reactions. The compounds RhCl₃ • 3H₂O, Rh₂(CO₂CH₃)₄, and Rh(PPh₃)₃Cl were adsorbed onto 13X and ZSM5 zeolites. Results of thiophene hydrodesulfurization over RhCl₃-13X and RhCl₃-ZSM5 were …
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Understanding Heterogenous Catalysis on Zeolites and Manganese Oxides
Zeolites are a unique type of heterogenous catalysts that have soared in importance since their initial use within industry in the 1950’s, largely due to their ability to be shape selective. Octahedral manganese oxides are another type of heterogenous catalyst that have emerged in significance and …
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Molecular Simulation of Zeolites by Machine-Learned Potentials
Zeolites are a class of minerals frequently used in catalysis, gas separation, and ion exchange. Zeolites exhibit significant variability in the morphology and dimensions of their pores and channels, which directly influences their suitability for specific applications depending on the molecules …
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Multinuclear NMR studies of zeolites and heme-proteins
… two seemingly completely different systems, zeolites in the solid state and proteins in solution, are investigated, using primarily $\sp{17}$O NMR spectroscopy.
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Heats of immersion of zeolites in n-alcohols
The heats of immersion in n-alcohols of zeolites NaY, 5A and ZSM-5 and the kinetics of the immersion process have been determined using a Calvet MS-70 microcalorimeter. The specific heat of immersion decreased non-linearly as a function of chain length of alcohol for NaY and 5A. In contrast, the …
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Isomerisation of cresols over zeolites HZSM5, HBeta and HMordenite
… isomers were investigated over three types of zeolites under liquid as well as vapour phase (only o-cresol isomer) reaction conditions. The best activity for o-cresol isomerisation, in the liquid phase, was initially HMordenite but because the catalyst deactivates so quickly, HZSM5 was thus …
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Methanol amination over hydrothermally treated zeolites RHO and Modernite
… with definite crystal structures, namely zeolites. While being more active than amorphous silica-alumina, most zeolites do not show improved selectivity. Catalysts, which have, however, been reported to show improved selectivity to DMA, include zeolites Rho, ZK-5 and Chabazite. In …
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Synthesis, characterization and reactivity of transition metal containing zeolites
Transition metal containing zeolites (zeolite A and ZSM-5) were prepared by addition of various transition metal containing substrates to zeolite synthesis gels. Crystal growth data were recorded in order to determine the influence of the transition metal species on the rate of crystal growth. …
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Zeolites for Cleaner Processes: Alkylation of isobutane and n-butene
… However, due to rapid deactivation of these zeolites, their acceptance in industrial alkylation has been delayed. In this study we seek a deeper understanding of the kinetics, transport, and sorption of organic molecules used in alkylation processes in nano-porous zeolites. A six lump kinetic …
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Fundamental studies on copper zeolites for catalytic NO x abatement
… and water (H<sub>2</sub>O). Copper containing zeolites show commercially viable SCR performance. Cu-SSZ-13 (CHA framework), a member of this family, is a preferred catalyst for SCR applications because it shows exceptional hydrothermal stability in addition to commercially viable SCR …
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Density Functional Study of NO Decomposition With Cu-Exchanged Zeolites
Cu ions exchanged into zeolites like ZSM-5 show high catalytic activity for the decomposition of environmentally harmful NO to harmless N$\sb2$ and O$\sb2.$ The present work is an attempt to study this phenomenon using a first-principles quantum mechanics-based density functional method. A small …
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Cooperative activation of biomass-derived oxygenates with Lewis acid zeolites
Zeolites containing Sn, Ti, Zr, or Hf heteroatoms are versatile catalysts for the activation and conversion of oxygenated molecules owing to the unique Lewis acid character of their tetrahedral metal sites. Through fluoride-mediated synthesis, hydrophobic Lewis acid zeolites can behave as …
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