(602g) Investigation of Pore Accessibility and Connections to Selectivity in Alkane Oxidation on M1 Phase Oxide
AIChE Annual Meeting
Thursday, November 11, 2021 - 2:18pm to 2:36pm
Propane/cyclohexane rate-ratio on MoVTeNb oxide is nearly an order of magnitude higher than on oxides without micropores, suggesting significant pore confinement of propane (albeit smaller than ethane, which showed two orders of magnitude higher ratios). Fig.1 shows measured and DFT-derived rate-constant-ratios representing selectivity in parallel and sequential steps for propane-O2 and propene-O2 reactions as a function of reciprocal temperature. The rate-constant-ratio comparing C-O bond formation versus C-H activation in propane (k2/k1) is nearly an order or magnitude lower on MoVTeNbO than on VOx/SiO2âused as a non-microporous reference. The overall sequential oxidation of propene relative to propane C-H activation (k3/k1) is similar on both oxides, but C-O bond formation to allylic C-H activation ratio (k3,2/k3,1) is much less than unity on MoVTeNb (consistent with high acrolein and acrylic acid selectivity) and greater than unity on VOx/SiO2. These findings support the suppression of C-O bonds in the pores observed previously. Systematic decrease in alkane/cyclohexane rate-ratio with alkane length and branching as well as impacts on selectivity provide comprehensive insights on confinement effects in selective oxidation.