Study On Ni-based Catalysts For CO Hydrogenation By In-situ FTIR

The syngas methanation reaction has been paid attention as one of the keytechnologies of coal chemical industry recently. It is important for the modification ofcatalysts to have a deep insight into the mechanism of CO methanation. In this paper,Ni/Al2O3(NA) and Ni/ZrO2-Al2O3(NZA) were prepared by impregnation method. Theeffect of ZrO2on catalytic performance for CO methanation was investigated throughfixed-bed reacter, XRD, H2-TPR, N2adsorption and disorption. Meanwhile, COmechanism was discussed by the in-situ FTIR. by comparing the changes of FTIRdifference CO adsorption and methanation reaction over the catalysts before and afterthe addition of ZrO2, the mechanism of CO methanation and reasons for the increaseof the catalytic activity of Ni/ZrO2-Al2O3(NZA) were given. The main results arefollows:(1) The effect of ZrO2on catalytic performance of catalysts at differenttemperature, time and CO/H2ratio are investigated. The results show that the activityand stability of NZA are better than NA. NZA catalyst inhibits the accumulation ofgraphite because ZrO2changed the physical and chemical properties of catalyst.(2) Through the study of in-situ FTIR on CO adsorption and methanation, it isconcluded that carbonyl hydride and mutil-hydrogen carbonyl hydride areinermediates of the reaction. Generation and accumulation of formate and carbonateare restrained for modification of catalyst by addition of ZrO2.(3) The reaction route of CO methanation is as follows: adsorbed COâ†'carbonyl hydrideâ†'mutil-hydrogen carbonyl hydrideâ†'CH4. The band intensity ofCH4on the surface of NZA is higher than that of NA at the same temperature. Thereason is that interaction between carbonyl hydride of liner adsorption site and bridgeadsorption site and NZA catalyst is smaller so that carbonyl hydride was more easilyto react with Hads.