Sorption-enhanced water gas shift reaction by sodium-promoted calcium oxides

Abstract The water gas shift reaction was evaluated in the presence of novel carbon dioxide (CO 2 ) capture sorbents, both alone and with catalyst, at moderate reaction conditions (i.e., 300–600 °C and 1–11.2 atm). Experimental results showed significant improvements to carbon monoxide (CO) conversions and production of hydrogen (H 2 ) when CO 2 sorbents are incorporated into the water gas shift reaction. Results suggested that the performance of the sorbent is linked to the presence of a Ca(OH) 2 phase within the sorbent. Promoting calcium oxide (CaO) sorbents with sodium hydroxide (NaOH) as well as pre-treating the CaO sorbent with steam appeared to lead to formation of Ca(OH) 2 , which improved CO 2 sorption capacity and WGS performance. Results suggest that an optimum amount of NaOH exists as too much leads to a lower capture capacity of the resultant sorbent. During capture, the NaOH-promoted sorbents displayed a high capture efficiency (nearly 100%) at temperatures of 300–600 °C. Results also suggest that the CaO sorbents possess catalytic properties which may augment the WGS reactivity even post-breakthrough. Furthermore, promotion of CaO by NaOH significantly reduces the regeneration temperature of the former.