Hydrogen production with a microchannel heat-exchanger reactor by single stage water-gas shift; catalyst development

摘要

The water-gas-shift reaction (1) is performed in fuel processors to remove undesired carbon monoxide and increase the hydrogen content of the reformate, which is harmful for numerous applications such as proton exchange membrane fuel cells (PEMFC). CO + H_2O□ CO_2 + H_2 □ H~0 = □ 41.2 kJ mol~(□1) (1) The CO concentration achieved by water-gas shift (WGS) is not low enough for automotive or stationary Pt based electrocatalysts in PEMFC applications [1]. A preferential CO oxidation (PrOx) step is required to reach the CO target concentration, below 10 ppm [2]. However, high temperature proton exchange membrane (HT-PEM) fuel cells allow higher CO concentration in the feed gas and they can tolerate CO concentrations up to 3 vol.%. Therefore, this work aims the development of an appropriate catalyst for a single stage WGS reactor, which achieves CO concentrations lower than 3 vol.%. Kolb et al. [3] tested different mono and bimetallic catalysts combining Pt/Rh/Pd/Ru metals based on CeO_2 and Al_2O_3 supports, operating at a volume hourly space velocity (VHSV) of 200 LN/(h·g_(cat)) with a feed composition of 46.8% H_2, 8.8% CO_2, 8.0% CO and 37.1% H_2O (vol.%). They found the best performance for a Pt/CeO_2-Al_2O_3 catalyst. The present work is a continuation of the work mentioned above and aims at the synthesis of a new catalyst with similar activity and stability, by replacing part of the Pt with a metal of lower cost. Apart from the catalyst cost reduction, the catalyst preparation procedure should also allow industrial production by screen printing, in order to save/reduce manufacturing costs.