Amine-based post-combustion CO2 capture mediated by metal ions: Advancement of CO2 desorption using copper ions

For the large-scale implementation of amine-based post-combustion CO2 capture, the energy consumption associated with the absorbent regeneration remains the most critical challenge. Despite efforts to reduce regeneration duty, such as using new amine formulations and modifying process configurations, an advanced method of overcoming this technical barrier is still required. Here, we introduce a novel approach to decreasing the heat requirement of absorbent regeneration by introducing metal ions catalyst into aqueous amine solution. Our approach uses the dual ability of amine in aqueous solution to both react with CO2 and complex with transition metal ions to reduce the heat of CO2 desorption via metal-amine complexation. Based on benchmarking monoethanolamine (MEA) absorbent and copper (Cu) ions, we developed a model that describes the process chemistry of Cu(II)-MEA-CO2-H2O to understand the speciation profiles under various conditions, particularly for Cu-MEA complexes. We conducted the comprehensive experiments to investigate the influence of Cu(II) addition on the performance of MEA-based CO2 capture process, including the CO2 absorption/desorption capacity, CO2 absorption/desorption rate, CO2 absorption temperature increase and heat of CO2 desorption. The results showed that adding Cu(II) to MEA solution significantly improved the CO2 capture performance, i.e. it mitigated the temperature increase during CO2 absorption, enhanced the CO2 desorption rate, increased the solvent's cyclic CO2 capacity due to deep CO2 stripping. More importantly, the heat of CO2 desorption was reduced by 13.2-24.0% depending on the copper ion concentration. Our results indicate that metal-amine complexes play an important role in advancing the amine-based CO2 capture process and have potential application to industrial practice.