(296e) Gold On Mixed La/Ce Oxides for the Water Gas Shift Reaction

The water gas shift reaction (WGS) is one of the key processes in the production of hydrogen from fossil and renewable resources. It is widely used to adjust the CO: H2 ratio in syngas for the production of chemicals and liquid fuels, and to reduce the carbon monoxide content in order to produce hydrogen-rich streams for fuel cells. Current industrial WGS utilizes a two-stage process involving a high temperature shift catalyst (typically Fe-Cr-based) and a low temperature shift catalyst (Cu/ZnO/Al2O3) in order to take advantage of fast reaction kinetics at high temperature and high equilibrium conversion at low temperature. However, these catalysts are not suitable for portable applications because of insufficient stability and activity.

Recently, supported Au catalysts have received considerable attention as potentially highly active WGS catalysts, in particular in combination with CeO2-based supports. CeO2 is an effective (and active) support material for noble metal-based catalysts in WGS. It has been shown previously that the properties of CeO2 can be improved by the addition of rare earth additives. However, very few systematic studies of such doped CeO2 for WGS are available in the published literature.

We are investigating the synthesis of Au supported on mixed La/Ce oxides over the entire range of La:Ce ratios. In the present contribution, we report the synthesis of gold catalysts on mixed CeO2- and La2O3-based oxide supports with variable Ce:La ratio. By utilizing a reverse microemulsion-templated sol-gel synthesis route, highly homogeneous mixed La/Ce- oxides solid solutions with cubic structures were obtained over the entire range of La-dopings up to 90% La content without phase separation. Au/CeO2-La2O3 catalysts were prepared by deposition-precipitation method and characterized by a wide range of methods (XRD, ICP, HRTEM, TPR and BET). Water gas shift catalytic tests showed that appropriate addition of La can significantly improve the activity of Au/CeO2. Correlations between structure and reducibility of the oxide supports and catalytic properties of Au/CeO2-La2O3 catalysts will be discussed in detail in the presentation.