Study On CuO-CeO₂/FeCrAl Monolithic Catalysts For Preferential Oxidation Of CO In Hydrogen Rich Gases

Fuel cells are extremely sensitive to even trace amounts (10ppm) of CO. Preferential oxidation of carbon monoxide is regarded as the favorable method for the purification of the hydrogen-rich streams. Catalysts for preferential CO oxidation need to be prepared as monolithic shape for use. The key problem is how to ensure high adherence between oxides and metallic supports. Then, the interaction between oxides and metallic supports could influence the structure of the catalysts and further influence the catalytic performance. The paper intends to resolve these two problems. New preparation methods are developed to prepare the monolithic catalysts with good adhesion stability. Based on this work, the interaction between oxides and supports is studied, and such interaction may lead to the change of the structure and the catalytic performance.CuO-CeO2 catalyst exhibits high activity for PROX. Cu1+ may be the key active component in the CuO-CeO2 catalyst, which either enters into the CeO2 lattice or exists in the interface between copper oxide and CeO2.The monolithic catalysts prepared by the sol-pyrolysis method present high adherence and catalytic performance. High surface energy of the crystal nucleus and interaction between the catalyst and the support promote the adhesion stability. The monolithic catalysts prepared by the microemulsion method also present good adherence. It must use many times to coat active components due to its special property of microemulsion. In addition, the special property of the microemulsion facilitates the interaction between copper oxide and creia. These are favorable for adhesion stability and the catalytic performance.For the monolithic catalyst prepared by in situ combustion synthesis method, the additives not only change the interaction between the active component and the support, but also change the redox properties of copper oxide, creia and the surface adsorbed oxygen, hence influence the adhesion stability and catalytic activity of the catalysts. The additives of Zr and Nd increase the selectivity of the monolithic catalysts.The presence of the support influences distribution and the interaction of the active components. Ceria is highly dispersed on the surface of the support,so CeO2 crystallite sizes become smaller. The interaction between ceria and alumina weakens the interaction between copper oxide and ceria, so partial CuO aggregates in the monolithic catalyst.Compared with the particle catalyst, the monolithic catalysts also present high catalytic performance for PROX. Good ability of heat transfer weakens the unfavorable effect of the reverse water gas shift reaction on CO preferential oxidation.