@article{truitt_white_2009, title={In-situ NMR studies of isobutane activation and exchange in zeolite beta}, volume={35}, ISSN={["1527-3326"]}, DOI={10.1016/j.ssnmr.2008.12.002}, abstractNote={(1)H solid-state NMR techniques have been used to simultaneously detect the reactivity of both catalyst and alkane reactant protons in an in-situ experimental design. Specifically, the activation of isobutane C-H bonds by the solid acid zeolite H-Beta is directly observed while the reaction is in progress, and the rate of proton transfer between the solid catalyst surface and gaseous isobutane is quantitatively measured using isotopic (1)H/(2)H exchange methods. Arrhenius analysis of isothermal kinetic runs revealed an apparent activation barrier of 70kJ/mole for the exchange process between isobutane and the 12-membered ring H-Beta, which exceeds our previously determined value of 57kJ/mole for isobutane in the 10-membered ring H-ZSM-5 (JACS 2006, v. 128, p. 1848). Estimation of true activation energies using heat of adsorption data from the literature combined with the experimentally measured apparent E(a) suggests that the true activation barrier differs by only 6-7kJ/mole in the two catalysts. We discuss the possibility that subtle shape selectivity, or inverse shape selectivity, and lattice solvation differences between the two catalysts account for the enhanced solvation of the isobutane transition state in HZSM-5 compared to the larger channel H-Beta. In all experiments, the isobutane reagent was treated to eliminate any unsaturated impurities that might serve as initiators for carbenium-ion mechanisms, and the active catalyst was free of any organic contaminants that might serve as a source of unsaturated initiators.}, number={2}, journal={SOLID STATE NUCLEAR MAGNETIC RESONANCE}, author={Truitt, Matthew J. and White, Jeffery L.}, year={2009}, month={Apr}, pages={100–103} } @misc{white_truitt_2007, title={Heterogeneous catalysis in solid acids}, volume={51}, number={2}, journal={Progress in Nuclear Magnetic Resonance Spectroscopy}, author={White, J. L. and Truitt, M. J.}, year={2007}, pages={139–154} } @article{sremaniak_whitten_truitt_white_2006, title={Weak hydrogen bonding can initiate alkane C-H bond activation in acidic zeolites}, volume={110}, ISSN={["1520-6106"]}, DOI={10.1021/jp0658703}, abstractNote={Ab initio calculations at the Hartree-Fock self-consistent field/single determinant (SCF) and configuration interaction multi-determinant (CI) expansion levels have been used to show that isobutane primary C-H bond activation occurs via direct protium exchange with the zeolite surface via a weakly hydrogen-bonded complex. The calculated 15 kcal/mol activation barrier agrees with the 13.7 kcal/mol value from a recently reported experimental study (J. Am. Chem. Soc. 2006, 128, 1847-1852). Overall, the mechanism described in this contribution demonstrates that weak C-H to O hydrogen bonding leads to complexes at the zeolite acid site that can facilitate C-H bond activation.}, number={42}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Sremaniak, Laura S. and Whitten, Jerry L. and Truitt, Matthew J. and White, Jeffery L.}, year={2006}, month={Oct}, pages={20762–20764} } @article{truitt_toporek_rovira-hernandez_hatcher_white_2004, title={Identification of an adsorption complex between an alkane and zeolite active sites}, volume={126}, ISSN={["0002-7863"]}, DOI={10.1021/ja046729f}, abstractNote={Direct observation of the Bronsted acid site signal in an active zeolite catalyst following adsorption of stoichiometric quantities of isobutane reveals the presence of a specific adsorption complex. Independent polarization transfer experiments in which magnetization originates with either the catalyst or the adsorbed isobutane confirm this assignment. The initial steps in alkane reactivity are poorly defined, and this experimentally verified complex is proposed as a route to C-H bond activation in solid acids.}, number={36}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Truitt, MJ and Toporek, SS and Rovira-Hernandez, R and Hatcher, K and White, JL}, year={2004}, month={Sep}, pages={11144–11145} }