Ni-modified Mo2C catalysts for methane dry reforming Original Research Article

Dry reforming of methane with CO2 (DRM) was studied over Ni–Mo2C catalysts with Ni/Mo molar ratios of 1/3, 1/2, and 1/1 (denoted as Ni–Mo2C (1/3), Ni–Mo2C (1/2), and Ni–Mo2C (1/1), respectively) aiming to investigate the catalytic roles of Ni and the carbide. The results of XRD and XPS characterizations indicated that the carbonization process was promoted by the presence of Ni. The CH4-TPR and CO2-TPO over the fresh samples proved that CH4 dissociation was greatly enhanced by Ni. The Ni–Mo2C (1/2) catalyst showed the best catalytic activity and stability for CH4/CO2 (1/1) dry reforming. Above 80% of CH4 and CO2 conversions were maintained at 800 °C during a test run of 20 h at W/F = 0.3 g s cm−3. Characterizations of the spent samples revealed that the deactivation of Ni–Mo2C (1/1) was due to coke formation whereas that of Ni–Mo2C (1/3) was due to bulk oxidation of Mo2C into MoO2. Only at a Ni/Mo molar ratio of 1/2, a catalytic oxidation–reduction cycle could be established. It was suggested that Ni–Mo2C was a typical bi-functional catalyst. In CH4/CO2 dry reforming, the dissociation of CH4 was catalyzed by Ni, while the activation of CO2 took place on Mo2C. By regulating the molar ratio of Ni and Mo2C, a catalytic redox cycle could be established.