High-purity hydrogen production through sorption enhanced water gas shift reaction using K2CO3-promoted hydrotalcite

Sorption enhanced water gas shift (SEWGS) reaction is a process concept, which simultaneously carries out the gas phase water gas shift (WGS) reaction (CO+H2O↔CO2+H2) and selective chemisorption of the byproduct CO2 from the gas phase reaction zone for direct production of essentially pure H2 in a single unit operation. A packed bed sorber-reactor containing an admixture of a WGS catalyst and a CO2 chermisorbent is used in the process. The concept circumvents the thermodynamic limitation of the WGS reaction and enhances the rate of reaction for H2 production. In this study, the SEWGS reaction concept was successfully demonstrated by both experiment and numerical simulation using K2CO3-promoted hydrotalcite as the CO2 sorbent. Numerical model simulations were also carried out to investigate the effects of various operating conditions of SEWGS reaction on the process performance. In general, higher H2O/CO feed ratio, higher fraction of sorbent (chemisorbent ratio in the sorber-reactor), and lower operating temperature favor both H2 productivity and CO conversion. Higher reaction pressure increases H2 productivity but decreases CO conversion.