Abstract: In-situ FT-IR technique was employed to investigate the evolution of surface species adsorbed on the Rh-Mn-Li-Ti/SiO2 catalyst under the reaction conditions including pressure, temperature, and H2/CO ratio during CO hydrogenation to C2-oxygenates. The results showed that high pressure favored the adsorption and the activation of CO, while high temperature favored the dissociation of adsorbed CO. The employment of high pressure and nigh temperature conditions not only promoted CO adsorption on the catalyst surface but also remained proper activity of CO dissociation. Thus CO insertion activity was enhanced, resulting in good performance for C2-oxygenate formation. The increase in H2/CO ratio promoted the adsorption of CO, and hence CO insertion, especially CO dissociation and hydrogenation, were enhanced. However, the high activities for CO dissociation and hydrogenation resulted from too high H2/CO ratio might suppress CO insertion, and thus the activity for the formation of C2-oxygenates decreased. Compared with the Rh/SiO2 catalyst, the addition of promoters (Mn, Li, and Ti) favored the formation of C2-oxygenates.

Key words: rhodium-based catalyst, carbon monoxide, hydrogenation, C2-oxygenate, infrared spectroscopy