Selective oxidation of CO in hydrogen-rich stream over Cu–Ce catalyst promoted with transition metals

Abstract

Cu–Ce/ γ-Al 2O 3 catalysts promoted with Co were tested for the low temperature selective oxidation of CO in excess hydrogen. The effects of Cu–Ce composition, Co as a dopant, stoichiometric ratio ( λ=2O 2/CO), water vapor and CO 2 on the selective oxidation of CO to CO 2, O 2 consumption and selectivity of O 2 to CO oxidation as a function of temperature are presented. Also, the catalytic properties of the catalysts were investigated by using X-ray diffraction, CO-/H 2-temperature programmed reduction, temperature programmed oxidation, CO-/CO 2-/H 2O-temperature programmed desorption (TPD). Small addition (0.2 wt) of Co onto the Cu–Ce/ γ-Al 2O 3 brought large increase in selective CO oxidation activity. In the presence of either CO 2 (13 vol%) or H 2O (10 vol%) in the reformed gas feed, both Cu–Ce/ γ-Al 2O 3 and Cu–Ce-Co/ γ-Al 2O 3 showed decreased activity in CO oxidation at low temperatures, especially, under 200°C. Compared with the Cu–Ce/ γ-Al 2O 3, however, the Cu–Ce-Co/ γ-Al 2O 3 gives higher resistivity for the CO 2 and H 2O. From the CO 2/H 2O-TPD results, it could be explained that the main cause for the decrease in catalytic activity with CO 2 and H 2O in the feed may be attributed to the competitive adsorption of CO and CO 2 as well as the blockage of the active sites by water vapor at low reaction temperatures.