Water gas shift reaction over monometallic and bimetallic catalysts supported by mixed oxide materials

• A comparison of catalytic activities of Cu on ceria and Gd doped ceria.
• Finely dispersed CuO species are efficient active sites for WGS reaction.
• Re assists Cu in reducing Ce4+ and giving rise to more Ce3+ at the surface of ceria.
• The presence of Ce3+ at the ceria surface increases O2− which leads to easier reduction.

In the present work, the water gas shift activities of Cu on ceria and Gd doped ceria were studied for a further enhancement of hydrogen purity after a steam reforming process. The catalytic properties of commercial catalysts were also studied to compare with our as-prepared catalysts. It was found that copper-containing cerium oxide is suitable for the high temperature reaction. Copper-ceria is a stable high-temperature shift catalyst, unlike iron-chrome catalysts which are deactivated severely in CO2-rich gases. 5%Cu/10%GDC (D) was found to have much higher activity than other copper ceria based catalysts. Finely dispersed CuO species is more favorable due to a higher activity, which explains the activity enhancement of this catalyst. The kinetics of the WGS reaction over Cu catalysts supported by mixed oxide materials were measured in the temperature range 200–400 °C. An independence of the CO conversion rate on CO2 and H2 was observed. To improve the catalytic performance of copper catalysts, the behavior of the bimetallic catalysts was compared with that of the monometallic catalysts. It was found that an addition of Re to Cu/GDC significantly improved the activity of copper catalysts. The effect of Re on enhancing the WGS activity of Cu catalysts was due to Re increases the reducibility of the surface ceria, In addition, Re contributes to reduction of Ce4+ to Ce3+. The presence of Ce2O3 at the ceria surface gives rise to oxygen vacancies which facilitate the electron movement at the surface leading to ease of surface reduction.

Figure optionsDownload high-quality image (213 K)Download as PowerPoint slide