Preferential CO oxidation on Ru/Al2O3 catalyst:: An investigation by considering the simultaneously involved methanation

The CO removal with preferential CO oxidation (PROX) over an industrial 0.5% Ru/Al2O3 catalyst from simulated reformates was examined and evaluated through considering its simultaneously involved oxidation and methanation reactions. It was found that the CO removal was fully due to the preferential oxidation of CO until 383 K. Over this temperature, the simultaneous CO methanation was started to make a contribution, which compensated for the decrease in the removal due to the decreased selectivity of PROX at higher temperatures. This consequently kept the effluent CO content as well as the overall selectivity estimated as the ratio of the removed CO amount over the sum of the consumed O-2 and formed CH4 amounts from apparently increasing with raising reaction temperature from 383 to 443 K when the CO2 methanation was yet not fully started. At these temperatures the tested catalyst enabled the initial CO content of up to 1.0 vol. % to be removed to several tens of ppm at an overall selectivity of about 0.4 from simulated reformates containing 70 vol. % H-2, 30 vol. % CO2 and with steam of up to 0.45 (volume) of dry gas. Varying space velocity in less than 9000 h(-1) did not much change the stated overall selectivity. From the viewpoint of CO removal the article thus concluded that the methanation activity of the tested Ru/Al2O3 greatly extended its working temperatures for PROX, demonstrating actually a feasible way to formulate PROX catalysts that enable broad windows of suitable working temperatures. (c) 2005 Elsevier B.V. All rights reserved.