Study on CO₂ reforming of methane to syngas over Al ₂O₃-ZrO₂ supported Ni catalysts prepared via a direct sol-gel process

Ni-based catalysts supported on Al₂O₃-ZrO₂ (Ni/Al₂O₃-ZrO₂) were prepared by a direct sol-gel process with citric acid as the gelling agent. The evaluation of the catalyst prepared for methane reforming with CO₂ was carried out with thermal gravimetric analysis (TGA), infrared spectroscopy (IR), X-ray diffraction (XRD), microscopy analyses (SEM and TEM), temperature-programmed reduction (TPR) and in a micro-reactor system. The catalytic performance for CO₂ reforming of methane to synthesis gas in a continuous-flow micro-reactor under atmospheric pressure was investigated. TGA, IR, XRD and microscopy analyses show that the Ni particles have a nanostructure of around 5nm and are uniformly dispersed on the Al₂O₃-ZrO ₂ support, which exists as an amorphous phase. Catalytic tests using CO₂ reforming of methane to synthesis gas show that the catalytic activity increases with increasing metal loading, and the 20Ni/Al ₂O₃-ZrO₂ (0.2 Ni/Al molar ratio) catalyst has excellent activity and stability, compared with that of the Al₂O ₃ supported Ni catalyst, with 91.9% conversion of CO₂ and 82.9% conversion of CH₄ over 50 h at 1073 K, atmospheric pressure, hourly space velocity of 11, 200 ml gcat^-1 h^-1 and CH ₄:CO₂:N₂ of 2:2:1. The excellent catalytic activity and stability is attributed to the very highly and uniformly dispersed small metallic Ni particles, the reducibility of the Ni oxides and an interaction between metallic Ni particles and the support Al₂O ₃-ZrO₂.