Effects of cobalt promoter and reduction temperature on the surface species and syngas adsorption of K–Co–Mo/C catalyst for mixed alcohols synthesis

Abstract

The K–Co–Mo/C catalysts with different molar ratios of Co/Mo and reduction temperatures were prepared by a sol–gel method and characterized by the means of XRD, H2-TPR, XPS and in situ DRIFTS. The addition of moderate amount of cobalt can promote the reduction of Mo species to Moδ+ species. With increasing the Co content, the CO adsorption strength on Moδ+ species increased and was up to the maximum when Co/Mo=0.5. Further increasing the Co content led to the decrease of surface Moδ+ species because that the formation of CoMoO3 inhibited the further reduction of Mo4+ species. Increasing the reduction temperature resulted in the decrease of the surface cobalt content significantly. The CO adsorption strength on Moδ+ species reached a maximum at 773K. Higher reduction temperature caused the decrease of CO adsorption strength because of the sintering of catalyst. It suggested that the surface Moδ+ species is responsible for the alcohol synthesis. The high activity of the K–Co–Mo/C catalysts with Co/Mo ratio of 0.5 for alcohol synthesis should be attributed to its high Moδ+ content on the surface.