Two-stage strategy for CO removal from H2-rich streams over (Nano-) CuO/CeO2 structured catalyst at low temperature

Abstract

Proton exchange membrane (PEM) fuel cells represent one of the most interesting systems for converting hydrogen from fossil or renewable fuels into electric power at low temperature. To prevent poisoning of fuel cell anodes, CO concentration has to be reduced to 10-100 ppm. To this aim, the preliminary catalytic preferential oxidation of CO may be used, provided that the catalyst effectively oxidizes CO, limiting as much as possible the oxidation of H2. Presently, both high selectivity and CO conversion cannot be simultaneously achieved. In this work, a novel strategy for CO removal from H2-rich streams based on a CuO/CeO2 reactive trap is proposed, exploiting both catalytic and adsorption properties of this material. The process occurs in two stages. In the first stage, one reactor, fed with a CO-containing stream, works as a CO-reactive adsorber, providing a CO-free mixture. In the second stage, the adsorbed CO is converted to CO2 by O2. By this approach it is possible to simultaneously get CO lower than the limiting value and avoid any H2 oxidation with no O2 in the feed stream to PEM. Experimental tests allowed the evaluation of the kinetic parameters of all the reaction mechanism steps. Model simulations were performed at varying operating parameters, showing that the positive effect of high contact times and low CO inlet concentration is significantly affected by the non-linear behavior of the CO reactive adsorption.