Selection of CO2 chemisorbent for fuel-cell grade H2 production by sorption-enhanced water gas shift reaction

New experimental data are reported to demonstrate that high purity H-2 can be directly produced by sorption-enhanced water gas shift (WGS) reaction using synthesis gas (CO + H2O) as sorber-reactor feed gas. An admixture of a commercial WGS catalyst and a proprietary CO2 chemisorbent (K2CO3 promoted hydrotalcite or Na2O promoted alumina) was used in the sorber-reactor for removal Of CO2, the WGS reaction by-product, from the reaction zone. The promoted alumina was found to be a superior CO2 chemisorbent for this application because (a) it could directly produce a fuel-cell grade H-2 product (<10-20 ppm CO) at reaction temperatures of 200 and 400 degrees C, and (b) it produced similar to 45.6% more high purity H-2 product per unit amount of sorbent than the promoted hydrotalcite at 400 degrees C. Furthermore, the specific fuel-cell grade H-2 productivity by the promoted alumina at a reaction temperature of 200 degrees C was similar to 3.6 times larger than that at 400 degrees C. These striking differences in the performance of the two CO2 chemisorbents were caused by the differences in their CO2 sorption equilibria and kinetics. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.