Performance of Na₂O promoted alumina as CO₂ chemisorbent in sorption-enhanced reaction process for simultaneous production of fuel-cell grade H₂ and compressed CO₂ from synthesis gas

The performance of a novel thermal swing sorption-enhanced reaction (TSSER) concept for simultaneous production of fuel-cell grade hydrogen and compressed carbon dioxide as a by-product from a synthesis gas feed is simulated using Na₂O promoted alumina as a CO₂ chemisorbent in the process. The process simultaneously carries out the water gas shift (WGS) reaction and removal of CO₂ from the reaction zone by chemisorption in a single unit. Periodic regeneration of the chemisorbent is achieved by using the principles of thermal swing adsorption employing super-heated steam purge. Recently measured equilibrium and kinetic data for chemisorption and desorption of CO₂ on the promoted alumina using conventional column dynamic tests as well as new experimental data demonstrating the concept of sorption-enhanced WGS reaction using the material are reviewed. The simulated performance of the TSSER process employing this material as a chemisorbent is compared with the process performance using K₂CO₃ promoted hydrotalcite as the chemisorbent. The promoted alumina exhibited (i) ∼15% lower H₂ productivity at a slightly reduced CO to H₂ conversion, and (ii) comparable compressed CO₂ productivity at a higher CO₂ recovery, albeit at a relatively lower product pressure. However, the steam duty for regeneration of the chemisorbent was reduced by ∼50% for the promoted alumina.