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

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