CO removal for hydrogen purification via Water Gas Shift and COPROX reactions with monolithic catalysts

Abstract

A combination of Water Gas Shift (WGS) and CO preferential oxidation (COPROX) reactions is considered a promising approach for CO removal in an H2 feed employed for PEM fuel cells. Honeycomb monolithic catalysts were studied for this purpose, firstly coated with Ce or Ce-Pr, then with Cu or Cu-Ni, (mass gained ∼35%). Computational Fluid Dynamics simulation showed that outer channels (close to reactor wall) presented a slightly lower flow in comparison with flow in inner ones. The Pr content in WGS monoliths modulated the activity-selectivity ratio showing an optimal value for 15 at.% in case of Ni-containing samples due to a significant selectivity improvement towards WGS (hindering methanation). A Cu/ceria monolithic sample was tested as COPROX catalyst. The CO conversion presented a maximum value with the increase of the operation temperature. Besides, a larger contact time (achieved by modifying monolith length) also enhanced the undesired H2 oxidation reaction as same as a larger O2/CO ratio. As a consequence, a temperature window around to 130 °C, a contact time close to 0.1 g.s/cm3, and a O2/CO = 1 M ratio was determined as the most adequate parameters set.