Doping of hydrotalcite-based sorbents with different interlayer anions for CO2 capture

Hydrotalcites (HTCs) with a molar ratio Mg2+/Al3+ = 2 or Mg2+/(Al3+ + Ga3+) = 2 and (Al3+/Ga3+ = 9) were synthesized using a co-precipitation method with two different interlayer anions: carbonate (CO32-) and triacetoxyborohydride ((CH3COO)(3)BH-). The simultaneous effect of aluminum partial substitution with gallium and impregnation with potassium on their CO2 sorption capacity was assessed. The physicochemical characterization of the sorbents was performed through different techniques (TGA-DTG, FTIR, XRD, SEM/EDS and AAS). The CO2 sorption equilibrium isotherms at 300 degrees C were determined for all the calcined sorbents and CO2 breakthrough runs carried out. Sorption isotherms under dry conditions were well described by the Freundlich model for all samples. The results indicate that the doping of HTCs with potassium greatly enhanced the sorption capacity when compared with the original materials. It was seen in the dynamic tests that steam affects negatively the sorption performance of the HTCs prepared with the compensating anion (CH3COO)(3)BH-, in opposition to what happens with the HTCs containing the CO32- anion.