Catalytic Activity and Stability of Nickel-Modified Molybdenum Carbide Catalysts for Steam Reforming of Methanol

Molybdenum carbides were modified by nickel with different doping amounts by using a temperature-programmed reaction (TPRe) process and used for steam reforming of methanol (SRM). XRD analysis results indicated that the beta-Mo2C phase was easily formed in Ni-modified carbide samples. The doping amount of Ni had great effect not only on the activity of the molybdenum carbide catalyst, but also on the catalyst stability. For relatively lower Ni doping amounts, i.e., Ni/Mo molar ratio = 0.8/99.2 to 2.4/97.6, the catalysts exhibited almost the same methanol conversion in the reaction temperature range. Meanwhile, when the Ni/Mo molar ratio was over 5/95, the catalytic activity was decreased greatly. Furthermore, Ni-Mo2C with Ni/Mo molar ratios of 1.6/98.4 and 2.4/97.6 showed longer term stability than other samples. Compared with the pure beta-Mo2C and other iron group element modified carbide samples, the Ni-modified one showed higher catalytic activity and stability. The fresh and spent catalysts were characterized by XRD, XPS, BET, and TEM and it is found that the resistance to the oxidation of molybdenum carbide and carbon deposition could be enhanced by the loading of Ni with low amounts.