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

<jats:title>Abstract</jats:title>
<jats:p>Currently, carbon capture and storage (CCS) technology appeared to be the most viable method to reduce carbon dioxide (CO<jats:sub>2</jats:sub>) 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 CO<jats:sub>2</jats:sub> 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 CO<jats:sub>2</jats:sub> sorption capacity, CO<jats:sub>2</jats:sub> sorption rate, and kinetic performance. CaO:NiO has demonstrated an excellent CO<jats:sub>2</jats:sub> sorption capacity of 0.79 mmol CO<jats:sub>2</jats:sub>/mmol CaO, meanwhile pure CaO exhibited lower CO<jats:sub>2</jats:sub> sorption capacity of 0.61 mmol CO<jats:sub>2</jats:sub>/mmol CaO at 600 °C. During the chemical reaction controlled stage, the CO<jats:sub>2</jats:sub> sorption rate of CaO:NiO was 0.78 mmol CO<jats:sub>2</jats:sub>/mmol CaO.min at 600 °C compared to pure CaO with sorption rate of 0.18 mmol CO<jats:sub>2</jats:sub>/mmol CaO.min. This study indicates that the addition of nickel oxide has successfully improved the CO<jats:sub>2</jats:sub> 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 CO<jats:sub>2</jats:sub> 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 (R<jats:sup>2</jats:sup> >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.</jats:p>