(613a) 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 H2 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 H2 product (<10-20 ppm CO) at reaction temperatures of 200 and 400 oC, and (b) it produced ~ 45.6% more high purity H2 product per unit amount of sorbent than the promoted hydrotalcite at 400 oC. Furthermore, the specific fuel-cell grade H2 productivity by the promoted alumina at a reaction temperature of 200 oC was ~ 3.6 times larger than that at 400 oC. These striking differences in the performance of the two CO2 chemisorbents were caused by the differences in their CO2 sorption equilibria and kinetics. The Sorption Enhanced Water Gas Shift reaction allows for the simultaneous production of H2 and its separation from CO2 in a single reactor unit. This concept can be applied to both coal and biomass gasification processes for the direct production of high purity H2 while also capturing the CO2 produced by the process.