Effect of Pretreatment Routes on the Performance and Structure of Ni-Co Bimetallic Catalysts

Ni-Co/La₂O₃-γ-Al₂O₃ catalysts for biogas reforming were prepared by conventional incipient wetness impregnation and pretreated first by hydrogen reduction and then by pure carbon monoxide, methane and carbon dioxide, respectively. The effect of pretreatment route on the biogas reforming performance of the catalysts was investigated. The catalysts were characterized with X-ray diffraction (XRD), thermogravimetric and differential scanning calorimetry (TG-DSC), and transmission electron microscopy (TEM), and the relationship between the performance and the structural properties of the catalysts was investigated. The results indicated that, compared with the performance of catalysts pretreated by the traditional hydrogen reduction, the performance of catalysts pretreated by hydrogen and carbon monoxide did not change significantly, while the performance of catalysts pretreated by hydrogen and methane deteriorated obviously. Nevertheless, the performance of catalysts pretreated by hydrogen and carbon dioxide was dramatically enhanced and the long adjustment period of the biogas reforming catalysts was basically eliminated. The characterization results showed that the active metal particle size of the catalysts pretreated by hydrogen and carbon dioxide was smaller on average and distributed more evenly and much more narrowly, which notably enhanced the catalysts' carbon resistance and prolonged the catalysts' longevity.