Methane reforming with CO₂ to syngas over CeO ₂-promoted Ni/Al₂O₃-ZrO₂ catalysts prepared via a direct sol-gel process

CeO₂-promoted Ni/Al₂O₃-ZrO₂ (Ni/Al₂O₃-ZrO₂-CeO₂) catalysts were prepared by a direct sol-gel process with citric acid as gelling agent. The catalysts used for the methane reforming with CO₂ was studied by infrared spectroscopy (IR), thermal gravimetric analysis (TGA), microscopic analysis, X-ray diffraction (XRD) and temperature-programmed reduction (TPR). The catalytic performance for CO₂ reforming of methane to synthesis gas was investigated in a continuous-flow micro-reactor under atmospheric pressure. TGA, IR, XRD and microscopic analysis show that the catalysts prepared by the direct sol-gel process consist of Ni particles with a nanostructure of around 5 nm and an amorphous-phase composite oxide support. There exists a chemical interaction between metallic Ni particles and supports, which makes metallic Ni well dispersed, highly active and stable. The addition of CeO ₂ effectively improves the dispersion and the stability of Ni particles of the prepared catalysts, and enhances the adsorption of CO ₂ on the surface of catalysts. The catalytic tests for methane reforming with CO₂ to synthesis gas show that the Ni/Al ₂O₃-ZrO₂-CeO₂ catalysts show excellent activity and stability compared with the Ni/Al₂O ₃ catalyst. The excellent catalytic activity and stability of the Ni/Al₂O₃-ZrO₂-CeO₂ are attributed to the highly, uniformly and stably dispersed small metallic Ni particles, the high reducibility of the Ni oxides and the interaction between metallic Ni particles and the composite oxide supports.