(762e) Kinetics of Propane Dehydrogenation on Bulk Zirconia Catalysts

We report the structural, kinetic, and mechanistic characterization of doped, bulk-zirconia catalysts for the non-oxidative conversion of propane to propylene. Aliovalent doping of zirconia with Y₂O₃ resulted in a formulation which exhibits very high selectivity to propylene (>95%) at rates (8 mmol g_cat^-1h^-1) comparable to Pt-Sn (15-24 mmol g_cat^-1h^-1) and CrOx-based (1-13 mmol g_cat^-1h^-1) catalysts reported in the literature. In addition, deactivation rates on the yttria doped zirconia (0.037 h^-1) compare favorably with formulations reported in the literature. These bulk zirconia-based formulations represent a promising alternative to conventional propane dehydrogenation catalysts.^1,2

Measured propylene rates are zero order in hydrogen and first order in propane, suggesting a mechanism where the dissociative adsorption of propane is the kinetically relevant step. We posit that acid-base pairs are stabilized upon low valent doping of irreducible oxides such as ZrO₂ which enables heterolytic cleavage of aliphatic C-H bonds in alkanes. Chemical titration and probe molecule studies demonstrating the existing of these acid-base pair sites also will be discussed.

1) Otroshchenko et al.; Angew. Chem. Int. Ed. 54 (2015) 15880

2) Sattler et al.; Chem. Rev. 124 (2014) 10613