Effect of MoO₃ on Structures and Properties of Ni-SiO₂ Methanation Catalysts Prepared by the Hydrothermal Synthesis Method

Several nickel-incorporated SiO 2 catalysts with MoO 3 molar content in range of 0.5% to 5.0% were prepared by the hydrothermal synthesis method and investigated for synthetic natural gas (SNG) production in a continuous flow fixed-bed reactor. MoO 3 can significantly improve the activity of Ni-SiO 2 due to electron transfer from MoO 3 to Ni species, while excessive MoO 3 (>3.0%) will reduce the catalyst activity due to partial coverage of active metal by MoO 3 and formation of Ni–Mo alloy. Ni-0.5%Mo-SiO 2 achieves the best activity with 100% CO conversion and ∼99% CH 4 yield at 400 °C, 2.0 MPa, and 12000 mL/g/h. The results of thermogravimetry (TG) and temperature-programming reduction (TPR) show that MoO 3 can inhibit carbon deposition of Ni-SiO 2 and excessive MoO 3 (>1.0%) will weaken the interaction between metallic nickel and the support. The results of XRD, TPR, and TG show that catalyst sintering rather than carbon deposition leads to catalyst deactivation in catalytic stability and thermal stability tests.