Effect of Ag promoter on redox properties and catalytic performance of Ag-Mo-P-O catalysts for oxidative dehydrogenation of propane

The influence of addition of sliver ions on the redox properties and catalytic performance of molybdenum-phosphate catalyst in oxidative dehydrogenation (ODH) of propane has been investigated. MoO₃ and AgMoO₂PO₄ have been detected in Ag-doped Mo-P-O catalysts. The redox properties have been characterized by H₂-temperature-programmed reduction (TPR), electronic paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS). The catalytic performance of MoO₃, Ag₂O, AgMoO₂PO₄ and Ag-doped Mo-P-O catalysts has also been examined. The incorporation of Ag improved the number of Mo⁵⁺ species and the reducibility of the catalysts. The Ag-doped catalysts favor activity and selectivity in ODH of propane higher than the undoped catalyst. The best catalyst was obtained with Ag/Mo ratio of 0.3 and MoO₃/AgMoO₂PO₄ ratio of 1.1. The influence of promoter Ag⁺ on redox properties and catalytic performance is due to forming redox couple “Ag⁰+Mo⁶⁺Ag⁺+Mo⁵⁺” and the synergetic effect originating from “coherent interface” between MoO₃ and AgMoO₂PO₄.