Abstract: The state and reactivity of surface oxygen species of mesoporous silica-supported vanadium oxide catalysts for oxidative dehydrogenation of propane have been investigated by microreactor tests combined with in-situ electron spin resonance, temperature-programmed surface reaction, and ultraviolet-visible diffuse reflectance spectroscopy. The pore diameter of the SBA-15, MCM-41, and silica gel supports exert great influences on the dispersion state of VO_x species and the catalytic properties of the supported vanadium oxide catalysts. The SBA-15-supported vanadium oxide catalyst has the highest selectivity for propylene because of its larger pore diameter and higher surface area. Surface lattice oxygen species of the VO_x/SBA-15 catalyst are main active species for oxidative dehydrogenation of propane to propylene. Highly dispersed VO_x species have high catalytic reactivity for oxidative dehydrogenation of propane. CO₂ can regenerate the lattice oxygen species of supported vanadium oxide catalysts. The high propylene selectivity for oxidative dehydrogenation of propane by CO₂ on supported vanadium oxide catalysts is related to weaker oxidizing effect of CO₂, which inhibits the direct C₃H₈ oxidation and the consecutive oxidation of C₃H₆ to CO_x.

Key words: propane;oxidative dehydrogenation;vanadium oxide;SBA-15, electron spin resonance;temperature-programmed surface reaction