Development of a novel Ru-based catalyst system for the selective oxidation of CO in hydrogen rich gas mixtures

The hydrogen feedstock for fuel cell applications can be supplied by reforming reactions followed by a water-gas-shift stage, where most of the CO is removed. Still the hydrogen rich gas mixture has to be purified further to prevent the anode's catalyst from severe degradation. At DLR, a novel, technically applicable Ru-based catalyst system was developed for the removal of CO from these gas mixtures by selective oxidation. Reticulated ceramic foams were used as matrix structure. These were coated with gamma-Al2O3 washcoat. Ru was applied as the active metal catalyst by the method of incipient wetness impregnation. Three different precursor materials were investigated. As Ru-nitrosylnitrate turned out to be the most favorable one, the oxidation temperature and the metal loading were varied using this precursor. Both parameters turned out to have a strong influence on catalyst activity and selectivity. The best foam-based catalyst was able to reduce the CO content in a simulated shift exit gas stream containing H-2, CO2, H2O and CO below 30ppm applying an oxygen excess of lambda = 3 in a temperature range between 100 and 160 degreesC, while charging the catalyst with space velocities up to 5000 h(-1). (C) 2002 Elsevier Science B.V. All rights reserved.