Research Of Co₃O₄-CeO₂ And Ag Catalysts For Preferential Oxidation Of CO In H₂-rich Gas

The preferential oxidation of carbon monoxide is an optimal method for the purification of hydrogen-rich gas used for fuel cells. And it is one of the key techniques for the application of fuel cells to develop catalysts with good catalytic performance for CO preferential oxidation. The main purpose of this paper is to find a new catalyst suitable for CO preferential oxidation.This work investigated the performance of Ag catalyst, and we discovered that Co₃O₄-CeO₂ exhibited much better activity than Ag catalyst. Therefore, the research was shifted to Co₃O₄-CeO₂. The influence of catalyst preparation, pretreatment, Co contents and calcination temperature on its catalytic performance was investigated, and so was the influence of H₂,CO₂ and H₂O in the feed gas and the space velocity on the preferential oxidation of carbon monoxide. XRD, N2-BET adsorption and XPS were used to investigate the components, specific surface area and the state of the elements on the surface of the catalysts.The main results are as follows:1. The activities of Ag catalysts on different supports vary in a wide range and cannot demonstrate ideal outcome. So Ag catalysts do not seem to fit for CO preferential oxidation in H₂-rich gas.2. Co₃O₄-CeO₂ exhibits good activity, and the best preparation conditions in our experiments are the following: co-precipitation, Co₃O₄ content 80wt.%, calcination temperature 350℃and oxidation pretreatment.3. CO₂ and H₂O, especially CO₂, have negative effects on CO preferential oxidation. The temperature window of the complete removal of CO becomes narrower with the increasing of space velocity.4. From XRD and BET results, it could be deduced that the size of the particles and the surface area have strong influences on the activity of Co₃O₄-CeO₂, and good performance could be obtained from the catalyst with highly dispersive particles and large surface area.5. The results of XPS indicate that the function of ceria is to increase the content of Co³⁺. Therefore, the activity of Co₃O₄-CeO₂ is enhanced.