Effect of MoO3 on the heat resistant performances of nickel based MCM-41 methanation catalysts

Several Ni–Mo based catalysts with Mo content from 1 wt% to 7 wt% were prepared by the impregnation method with MCM-41 as the support. The effect of Mo content on the activity of the catalyst was investigated for syngas methanation in a fixed-bed reactor. The addition of MoO3 could obviously improve catalytic activity of Ni/M catalyst at low temperature of 250 °C with the CO conversion and the CH4 selectivity from about 20%, 16% to 100%, about 80%, respectively. Ni–3%Mo/M catalyst showed the best activity with a CO conversion of 100% and a CH4 selectivity of 94% at 350 °C under 1.0 MPa and 12000 ml/g/h with a 3:1 molar ratio of H2 to CO. Compared with Ni/M catalyst, Ni–Mo/M catalysts showed higher resistance to sintering and no decrease in the catalytic activity after calcination at 700 °C for 2 h. In the 100 h stability test under atmospheric pressure, the CO conversion and the CH4 selectivity obtained on Ni–3%Mo/M catalyst maintained at about 100% and 89%, respectively, suggesting an excellent catalytic stability of this catalyst. The catalysts were characterized by N2 adsorption–desorption, CO chemisorptions, TEM, SEM-EDS, ICP, XRD, H2–TPR and XPS, and the results showed that electron transfer from MoO3 to metal nickel was the main cause of activity improvement of Ni–Mo/M catalysts at low reaction temperature of 250 °C. The addition of MoO3 could obviously improve the heat resistant performance of Ni/M catalyst. The results of TPR, SEM–EDS and XRD showed that the addition of MoO3 could enhance the interaction between metal nickel and the support in the way of Ni–Mo alloy, which inhibited the catalyst sintering.