Rajamani Gounder

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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)
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)
Compensation between adsorption entropies and enthalpies results in less than a two-fold variation in adsorption equilibrium constants for C3–C6 alkanes at temperatures relevant for monomolecular cracking; the size-independent activation energy for C–C bond activation in C3–C6 alkanes indicates that the marked increase in monomolecular cracking turnover(More)
Brønsted acid sites in zeolites catalyze alkene hydrogenation with H2 via the same kinetically-relevant (C-H-H) + carboniumion-like transition states as those involved in monomolecular alkane dehydrogenation. Reactions between C3H6 and H2 selectively form C3H8 (>80% carbon basis) at high H2/C3H6 ratios (>2500) and temperatures (>700 K). Ratios of C3H8(More)
The location of Brønsted acid sites within zeolites influences catalytic rates and selectivities when their diverse intrachannel environments stabilize transition states to different extents. Mordenite zeolites in the proton form (H-MOR) contain acid sites located within two general environments: eight-membered ring (8-MR) side pockets and 12-MR main(More)
Brønsted acid sites in zeolites (H-FER, H-MFI, H-MOR) selectively hydrogenate alkenes in excess H2 at high temperatures (>700 K) and at rates proportional to alkene and H2 pressures. This kinetic behavior and the De Donder equations for non-equilibrium thermodynamics show that, even away from equilibrium, alkene hydrogenation and monomolecular alkane(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 (CDHUSY) predominantly reflect differences in the size and solvating(More)
The selective transformation of hexose and pentose sugars to intermediate platform chemicals, such as furans, is an essential step in the conversion of cellulosic and hemicellulosic biomass to biofuels and biochemicals. Yet, many challenges in achieving commercially viable processes remain. In this feature article, we outline challenges that need to be(More)