Study on modified Mo2C/Al2O3 catalyst for POM to syngas

The supported Mo2C/Al2O3 catalyst was prepared and modified by a trace amount of Ni, Co, Cu or K, and evaluated under the conditions of n(CH4)/n(O-2) = 2.05, GHSV = 20.5 L/(g(.)h) and theta = 850 degreesC in a microreactor for partial oxidation of methane (POM) to syngas. The results showed that the Ni-MO2C/Al2O3 exhibited the highest activity and selectivity, and its catalytic performance was particularly stable. Co had the functions, though to less extent, similar to Ni. The addition of Cu promoted the CH, conversion at initial stage, but then the promotion disappeared rapidly. However, the addition of Cu was unfavorable to the selectivity for CO and H-2. The addition of K was unfavorable to POM to syngas. The catalytst samples were characterized by temperature-programmed surface reaction (TPSR) technique. The TPSR result indicated that the carbonization Of MoO3 was carried out via two steps, namely, reduction by H-2 at first and then carbonization by CH4. The addition of Ni or Co promoted the activation of CH4, the reduction of MoO3 by H-2 and the deposition of carbon, and then promoted the carbonization. Thus, there was possibility for the modified catalyst to hold more carbide or oxycarbide as active phase in the process of POM. Whilst for K-modified catalyst, the K prevented the catalyst from reduction by H-2, carburization by CH4 and activation of CH4. Thus, the K was unfavorable to POM. As for Cu-modified catalyst, Cu promoted the reduction of MoO3 and activation of CH4, thus promoted POM to syngas. Meanwhile, the Cu was favorable to the activation Of O-2 Molecule, being unfavorable to the reaction selectivity. For the Cu-modified catalyst, the disappearance of promotion to CH4 conversion after initial period might be due to the change of valence state of Cu ion.