Remarkable support effect of ZrO2 upon the CO2 reforming of CH4 over supported molybdenum carbide catalysts

In reforming of CH4 with CO2 over molybdenum carbide catalysts, the catalytic performance of unsupported hexagonal Mo2C prepared by direct carburization of MoO3 was considerably different from a similar composition, cubic MoC1-x (x approximate to 0.5), prepared through nitriding before carburization. The conversion levels over MoC1-x were substantially higher than those over Mo2C, although the turnover frequencies were lower. X-ray diffraction analysis indicated that Mo2C deactivated by conversion to MoO2 during the reaction, but the MoC1-x was transformed to the hexagonal Mo2C and remained stable. The activity of Mo2C dispersed on various supports for the CH4-CO2 reaction was also investigated. The performance depended strongly on the property of supports, with the ZrO2-supported Mo2C catalyst exhibiting the highest activity and durability for this reaction. Moreover, deactivation of Mo2C/ZrO2 at ambient pressure was suppressed by decreasing the loading amount of Mo2C.