CO2 Capture by Hydrotalcite-Derived Sorbents in Pressure Swing Adsorption for Sorption-Enhancing

This work investigated hydrotalcite-derived sorbents for CO2 capture at 350 °C, 10 or 14 bar, and 38.5 vol% CO2 in wet or dry gas flow under dynamic Pressure Swing Adsorption (PSA) in a packed-bed laboratory reactor. The chosen conditions enabled a preliminary assessment of the suitability of hydrotalcite-derived sorbents for Sorption-Enhanced-Water-Gas-Shift (SEWGS), a promising process for producing pure hydrogen from syngas. Two starting sorbents were considered: derived from commercial hydrotalcite, and from hydrotalcite synthesized by low-supersaturation. Both sorbents were doped with 20 wt% K2CO3. In addition, a hydrotalcite bifunctional catalyst-sorbent for SEWGS was studied. K2CO3-doping and higher pressure significantly improved the CO2-sorption capacity; the highest value (1.51 mmolCO2∙g−1) was measured under wet conditions at 14 bar. The bifunctional material showed good, stable CO2 sorption capacity (1.39 mmolCO2∙gsolid−1 on average out of five PSA cycles under wet conditions at 14 bar). Materials derived from commercial hydrotalcite doped with K2CO3 showed promising performances for future industrial SEWGS applications.