Preparation of highly active and stable nanostructured Ni-Cr2O3 catalysts for hydrogen purification via CO2 methanation reaction

In this study, a series of Ni/Cr2O3 catalysts with various Ni percentages were synthesized using a solvent-free mechanochemical method and the prepared catalysts were evaluated in CO2 methanation reaction. The influence of metal loading on the catalytic performance was investigated and it was found that increasing in Ni content improved both the carbon dioxide conversion and CH4 selectivity due to the increase in the concentration of active sites. It was evident that among the samples with different Ni loadings, the 20 wt%Ni/Cr2O3 catalyst demonstrated the highest catalytic performance. The catalytic performance of the Ni-Cr2O3 mixed oxide was also compared with Ni/Cr2O3 catalyst. The Ni-Cr2O3 mixed oxide catalyst was more active than the Ni/Cr2O3 catalyst and exhibited 68.98% CO2 conversion and 100% CH4 selectivity at 350 °C (H2/CO2 = 3 M ratio, GHSV = 18000 ml/gcat.h). The higher activity of the mixed oxide catalyst was due to the higher specific surface area, smaller crystalline size, and improved reducibility. Also, 20 wt%Ni-Cr2O3 composite catalyst exhibited high stability for 12 h at 300 °C in the CO2 methanation reaction. It was seen that the increase in H2/CO2 molar ratio from 2 to 5 and also the decrease in GHSV value and calcination temperature improved the catalytic activity.