Rajamani Gounder

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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)
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)
Operando X-ray absorption experiments and density functional theory (DFT) calculations are reported that elucidate the role of copper redox chemistry in the selective catalytic reduction (SCR) of NO over Cu-exchanged SSZ-13. Catalysts prepared to contain only isolated, exchanged Cu(II) ions evidence both Cu(II) and Cu(I) ions under standard SCR conditions(More)
The relationships among the macroscopic compositional parameters of a Cu-exchanged SSZ-13 zeolite catalyst, the types and numbers of Cu active sites, and activity for the selective catalytic reduction (SCR) of NOx with NH3 are established through experimental interrogation and computational analysis of materials across the catalyst composition space.(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)