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

摘要

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. MoO_3 and AgMoO_2PO_4 have been detected in Ag-doped Mo-P-O catalysts. The redox properties have been characterized by H_2-temperature-programmed reduction (TPR), electronic paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS). The catalytic performance of MoO_3, Ag_2O, AgMoO_2PO_4 and Ag-doped Mo-P-O catalysts has also been examined. The incorporation of Ag improved the number of Mo~(5+) 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 MoO_3/AgMoO_2PO_4 ratio of 1.1. The influence of promoter Ag~+ on redox properties and catalytic performance is due to forming redox couple "Ag~0 + Mo~(6+) <=> Ag~+ + Mo~(5+)" and the synergetic effect originating from "coherent interface" between MoO_3 and AgMoO_2PO_4.