Oxidative dehydrogenation of propane over a series of low-temperature rare earth orthovanadate catalysts prepared by the nitrate method

A series of high-purity rare earth orthovanadates were prepared by the nitrate method and found to be effective low-temperature catalysts for the oxydehydrogenation of propane at 320 degrees C, at which no reactions occurred over the catalysts reported in the literature, and, thus, may be of practical significance. The catalytic performances of LnVO(4) (Ln=Y, Ce-Yb) at 500 degrees C were much better than those of rare earth orthovanadate catalysts and also slightly exceeded that of magnesium orthovanadate Mg-3(VO4)(2) reported in the literature. LnVO(4) (Ln = Y, Ce-Yb) materials were tetragonal active phases which could stabilize the existence of active sites for the oxydehydrogenation of propane. Some catalysts with a certain amount of LnVO(3) reduced from LnVO(4) (Ln = Ho-Yb) under reaction atmosphere exhibited better redox properties and catalytic performances possibly due to the existence of biphasic catalytic synergy. LaVO4 was a monoclinic unstable active phase, although its bulk structure did not change after reaction. The remarkable deactivation of the LaVO4 catalyst was probably due to that LaVO4 could not stabilize the existence of surface active sites.