Improved CO2 Sorption Performance of Calcium Oxide (CaO) Sorbent with Nickel Oxide Additive

Abstract

Currently, carbon capture and storage (CCS) technology appeared to be the most viable method to reduce carbon dioxide (CO2) emission from its existing sources. This paper reports the improved performance of calcium oxide (CaO)-based sorbents with the addition of nickel oxide (NiO) as an additive (denoted as CaO:NiO) in CO2 sorption process (CaO carbonation reaction). Pure CaO was used as benchmarked sorbent in this study. The samples were synthesized using the sol-gel method and CaO:NiO were evaluated for their performance in CaO carbonation at different sorption temperatures, from its CO2 sorption capacity, CO2 sorption rate, and kinetic performance. CaO:NiO has demonstrated an excellent CO2 sorption capacity of 0.79 mmol CO2/mmol CaO, meanwhile pure CaO exhibited lower CO2 sorption capacity of 0.61 mmol CO2/mmol CaO at 600 °C. During the chemical reaction controlled stage, the CO2 sorption rate of CaO:NiO was 0.78 mmol CO2/mmol CaO.min at 600 °C compared to pure CaO with sorption rate of 0.18 mmol CO2/mmol CaO.min. This study indicates that the addition of nickel oxide has successfully improved the CO2 sorption rate and capacity of CaO for CaO:NiO. Based on the kinetic study, it has been observed that the diffusion controlled stage has a greater resistance towards the CO2 sorption process (carbonation reaction) compared to rapid chemical reaction controlled stage. Experimental carbonation data for CaO:NiO fitted very well to the shrinking core model (SCM) with high correlation coefficient (R2 >0.936). The specific rate constants of rapid chemical reaction and diffusion-limited stages are directly proportional to the carbonation temperature. The activation energy required for CaO:NiO sorbent during the chemical reaction control stage was 31.81 kJ/mol.