471230 Selective Activation of Primary C-H Bonds of Propane on Pdo(101)

Thursday, November 17, 2016: 8:30 AM
Franciscan D (Hilton San Francisco Union Square)
Jason F. Weaver1, Aravind Asthagiri2, Feng Zheng1, Li Pan3, Juhee Choi1, Vikram Mehar1 and John Diulus1, (1)Chemical Engineering, University of Florida, Gainesville, FL, (2)William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, (3)Chemical Engineering, The Ohio State University, Columbus, OH

Achieving selective C-H bond cleavage is critical for developing catalytic processes that transform small alkanes to value-added products. In this talk, I will discuss our recent investigations that clarify the molecular-level origin for an exceptionally strong preference for propane to dissociate on the crystalline PdO(101) surface via primary C-H bond cleavage. From experiments using different propane isotopologues, we find that more than 90% of the adsorbed propane molecules that dissociate on PdO(101) during temperature programmed reaction spectroscopy react via cleavage of primary C-H bonds. Using reflection absorption infrared spectroscopy (RAIRS) and density functional theory (DFT) calculations, we show that the adsorbed propane σ-complexes preferentially adopt geometries on PdO(101) in which only primary C-H bonds datively interact with the surface Pd atoms at low propane coverages and are thus activated under typical catalytic reaction conditions. We show that a propane molecule achieves maximum stability on PdO(101) by adopting a bidentate geometry in which a H-Pd dative bond forms at each CH3 group. We also find that adsorbed propane molecules undergo a configurational change with increasing coverage, and begin to preferentially coordinate to the surface through the CH2 group at sufficiently high coverage. Our results demonstrate that structural registry between the molecule and surface can strongly influence the selectivity of a metal oxide surface in activating alkane C-H bonds, and may thus provide guidance in designing catalysts capable of promoting selective alkane conversions.

Extended Abstract: File Not Uploaded
See more of this Session: Fundamentals of Surface Reactivity I
See more of this Group/Topical: Catalysis and Reaction Engineering Division