CO hydrogenation on lanthana and vanadia doubly promoted Rh/SiO2 catalysts

This paper reports on a study of the combined promoting effect of La and V oxides for ethanol formation during CO hydrogenation on silica-supported Rh catalysts. Non-promoted and La and/or V oxide promoted Rh/SiO2 catalysts were prepared by sequential or co-impregnation methods and characterized by TEM, CO chemisorption and FT-IR. Their catalytic properties for CO hydrogenation were investigated using a differential fixed bed reactor at 230 °C and 1.8 atm. It was found that, compared to non-promoted Rh/SiO2, the singly promoted catalysts, Rh–La/SiO2 and Rh–V/SiO2, showed improved reactivity (3×) and better ethanol selectivities. However, the doubly promoted Rh–La–V/SiO2 catalysts exhibited even higher activity (9×) and selectivity for ethanol and other C2+ oxygenates, with the selectivity of total C2+ oxygenates >30% at these low pressure reaction conditions. The better performance of the Rh–La–V/SiO2 catalysts appears to be due to a synergistic promoting effect of the combined lanthana and vanadia additions through intimate contact with Rh. Use of just more of each promoter by itself was not able to produce the enhanced catalytic performance.