Studies On CeO2-based Aerogel Catalysts Used For Preferential Oxidation Of Carbon Monoxide In Excess Hydrogen

The development of efficient catalysts for the preferential oxidation (PROX) of carbon monoxide in the presence of excess hydrogen has attracted increasingly interest during the last years due to the potential application of such catalysts in the environmentally important fuel cell technology. In this work , CeO₂,CexZr_1-xO₂ and Ce_0.49Zr_0.49RE0.02O(2RE=La,Sm,Pr)aerogel were prepared by supercritical drying (SCD) method, and these aerogel supported copper catalysts were prepared by wet impregnation. Their catalytic performances for PROX of CO in H2 simulated proton-exchange membrane fuel cell (PEMFC) feed gas, compared under the space velocity 20000mlg-1h-1and fixed-bed reactor at atmospheric pressure were investigated. The effects of the presence of carbon dioxide (CO₂) and vapour (H2O) in the reactant feed on the activity and selectivity of these catalysts were also investigated. And these catalysts were characterized by the techniques of temperature–programmed reduction (TPR), X-ray diffraction (XRD) and specific surface area (SBET) test were employed for the characterization.The main results are as follows:CeO₂ aerogel supported CuO catalysts prepared by impregnation method shows good catalytic activity for PROX of CO , and the highest conversion and selectivity were obtained on (12wt%)CuO/CeO₂. The strong surface interaction was existed between CuO and CeO₂ support. CuO species existed on the CuO/CeO₂ catalyst surface as Cu2+, Cu+(or Cu), which enhanced the catalytic activity of the CuO/CeO₂ for the CO oxidation.The catalytic activity for PROX of CO of CexZr_1-xO₂ aerogel supported CuO catalyst was not good as CuO/CeO₂ catalyst, but they exhibited exceptionally selective, a good tolerant towards CO₂ and H2O. The reasons for this phenomenon must be as follows: when Zr component doped, the property of the support would be influenced, and the changed interaction between support and copper would affect the catalytic performances.The catalytic activities of Ce0.98RE0.02O₂ and Ce_0.49Zr_0.49RE0.02O₂(RE=La,Sm,Pr) aerogel supported CuO catalysts were decreased when rare earth RE was doped into CuO/ Ce0.98RE0.02O₂ and CuO/Ce_0.49Zr_0.49RE0.02O₂, but they exhibited a good tolerant towards CO₂.