Rajamani Gounder

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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(More)
Acidic zeolites are indispensable catalysts in the petrochemical industry because they select reactants and their chemical pathways based on size and shape. Voids of molecular dimensions confine reactive intermediates and transition states that mediate chemical reactions, stabilizing them by van der Waals interactions. This behavior is reminiscent of the(More)
Compensation between adsorption entropies and enthalpies results in less than a twofold variation in adsorption equilibrium constants for C 3 –C 6 alkanes at temperatures relevant for monomolecular cracking; the size-independent activation energy for C–C bond activation in C 3 –C 6 alkanes indicates that the marked increase in monomolecular cracking(More)
Brønsted acid sites in zeolites catalyze alkene hydrogenation with H 2 via the same kinetically-relevant (C-H-H) + carbonium-ion-like transition states as those involved in monomolecular alkane dehydrogenation. [1] Reactions between C 3 H 6 and H 2 selectively form C 3 H 8 (> 80 % carbon basis) at high H 2 /C 3 H 6 ratios (> 2500) and temperatures (> 700(More)
The location of Brønsted acid sites within zeolite channels strongly influences reactivity because of the extent to which spatial constraints determine the stability of reactants and of cationic transition states relevant to alkane activation catalysis. Turnover rates for monomolecular cracking and dehydrogenation of propane and n-butane differed among(More)
Kinetic, spectroscopic, and chemical titration data indicate that differences in monomolecular isobutane cracking and dehydrogenation and methanol dehydration turnover rates (per H +) among FAU zeolites treated thermally with steam (H-USY) and then chemically with ammonium hexafluorosilicate (CD-HUSY) predominantly reflect differences in the size and(More)
Keywords: Alkene hydrogenation Alkane dehydrogenation Brønsted acid catalysis De Donder relations Microscopic reversibility Monomolecular alkane activation Zeolite catalysis a b s t r a c t Brønsted acid sites in zeolites (H-FER, H-MFI, H-MOR) selectively hydrogenate alkenes in excess H 2 at high temperatures (>700 K) and at rates proportional to alkene and(More)
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