Abstract: The biphasic synergistic effect of a mechanically mixed Mg-V-O catalyst system, which included MgO-Mg3(VO4)2, Mg3(VO4)2- Mg2V2O7, and V2O5-MgV2O6 catalysts, in the oxidative dehydrogenation of cyclohexane was studied. Characterization results and catalytic performance measurements reveal that the biphasic synergistic effect derives from three mechanisms: the formation of coherent interface of the two phases, the remote control mechanism originated from the spillover of mobile surface oxygen, and the formation of a surface con-tamination layer of one phase on the surface of the catalyst. The biphasic synergistic effect on the conversion, yield, and selectivity was ob-served in Mg3(VO4)2 mixing with a suitable amount of MgO and Mg2V2O7. Among the catalyst system, the 80%Mg3(VO4)2- 20%Mg2V2O7 catalyst exhibits better catalytic performance and shows cyclohexene selectivity of 44.9% with cyclohexane conversion of 15.5%.

Key words: magnesium, vanadium, complex oxide, cyclohexane, oxidative dehydrogenation, cyclohexene