High-temperature dehydrogenation of zeolite Brønsted acid sites and hydroxyl nests

PETR 20

Dustin W. Fickel, fickel@udel.edu1, Anne Marie Shough, amzimm@udel.edu2, Michael J. Nash1, Douglas J. Doren2, and Raul F. Lobo1. (1) Center for Catalytic Science and Technology, Department of Chemical Engineering, University of Delaware, Newark, DE 19716, (2) Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716
The dehydroxylation of thermally treated zeolites has been investigated using a combination of experimental and theoretical methods. The reaction is found to be a dehydrogenation process and not a dehydration. Temperature-programmed-desorption studies identify H2, not H2O, as the primary product from both Brønsted acid sites [Si–OH–Al] (BAS) and defect hydroxyl nest sites. Using hybrid QM/MM calculations and vibrational analyses, plausible paths have been identified for the formation of hydrogen from zeolite BAS and hydroxyl nests sites resulting in the formation of [AlO4]0 and bisperoxosilyl groups, respectively. The [AlO4]0 sites, acting as nonacidic one-electron acceptors of adsorbed molecules, could play an important role in the catalytic chemistry of hydrocarbons in some petroleum refining processes.
 

Zeolite Catalysis for Green Chemistry in Synthesis of Chemicals and Fuels
1:20 PM-5:30 PM, Sunday, April 6, 2008 Morial Convention Center -- Rm. 209, Oral

Division of Petroleum Chemistry

The 235th ACS National Meeting, New Orleans, LA, April 6-10, 2008