Roles of chlorine in the CO hydrogenation to C2-oxygenates over Rh-Mn-Li/SiO2 catalysts

Rh-Mn-Li/SiO2 catalysts were prepared by transforming nitrate and chloride precursors from one form to another stepwise, in an attempt to investigate the roles of chlorine in determining the catalytic properties of Rh-Mn-Li/SiO2. The space time yield (STY) of C2-oxygenates and CO conversion increased from 270.1 g/(kg-cat h) and 4.3% to 597.1 g/(kg-cat h) and 8.5%, respectively, and the selectivity towards C2-oxygenates increased from 65.5 to 73.6%, when the precursors of Rh, Mn and Li were completely transformed from nitrates to chlorides. The chlorine seems to function by increasing the amount of Rh species in intimate contact with Mn species and increasing the intensity of Rh–Mn interaction during reduction of the catalyst, therefore improving the Rh particle geometries, sizes and size distribution and the ratio of Rh+/Rh0 on the reduced catalyst. Such properties are responsible for the activity and selectivity towards C2-oxygenates over Rh-Mn-Li/SiO2 catalyst.

The activity and selectivity towards C2-oxygenates over Rh-Mn-Li/SiO2 catalyst obviously increased with the increase of chlorine content of dried catalyst. The chlorine seems to function by increasing the amount of Rh species in intimate contact with Mn species and increasing the intensity of Rh–Mn interaction during reduction of the catalyst, therefore improving the Rh particle geometries, sizes and size distribution and the ratio of Rh+/Rh0 on the reduced catalyst.Figure optionsDownload as PowerPoint slide