Activation and Deactivation of Au–Cu/SBA-15 Catalyst for Preferential Oxidation of CO in H2-Rich Gas

Abstract

This work aims to develop an efficient catalyst for preferential oxidation (PROX) of CO in a H2-rich gas and obtain a clear structure–property relationship of the catalyst. A Au/CuO/SBA-15 catalyst was designed and prepared via a nanoengineering approach in which the metallic particles of average size 3 nm located in the vicinity of CuO particles were highly dispersed on the SBA-15 support. It was found that the CuO particles could reduce the gold (Au) particle size, stabilize the Au particles, and facilitate the activation of molecular oxygen. Although this catalyst is extremely active for the PROX reaction at room temperature and superior to the Au/SBA-15 and CuO/SBA-15 catalysts, it deactivates easily. Clear experimental evidence showed that CuO was reduced to Cu2O and Cu in the reductive reaction gas mixture, and the Cu further combined/dissolved into the Au particles during the reaction. The alloying of Au and Cu not only decreased the catalytic activity of the Au particles but also reduced the ability of CuO to activate molecular oxygen. Fortunately, this alloying process could be reversed via a simple calcination in air to activate the catalyst. The identification of the catalyst structural evolution and this new contributing factor toward the deactivation of the Au catalysts has provided insights into the field of Au catalysis.