Enhanced CO2 chemisorption at high temperatures via oxygen addition using (Fe, Cu or Ni)-containing sodium cobaltates as solid sorbents

Sodium cobaltates containing Fe, Cu or Ni were synthesized, characterized and evaluated for CO2 capture at high temperatures. Initially, NaCoO2 and metal-containing samples were characterized by XRD, XPS, SEM and N2 adsorption-desorption, where it was probed that Fe, Cu and Ni were partially incorporated into the NaCoO2 structure. All these ceramics were able to trap CO2, but only Fe-containing sample presented an important CO2 chemisorption improvement in comparison to the pristine NaCoO2 sample. Based on these results, a second set of samples was prepared and characterized, varying the iron concentration (10, 20 and 30 mol%). Results showed that CO2 chemisorption was improved by iron addition up to 20 mol%, but higher amounts of iron did not continue enhancing the chemisorption process. Afterwards, the gas flow was modified adding oxygen (PCO2 = 0.95 and PO2 = 0.05), resulting in higher CO2 chemisorption efficiencies and kinetics. These analyses were complemented by CO2 cyclic experiments, where different gas flows were used, analyzing thermal stability and efficiency evolution.