Performance and Mechanism of Metal Oxide Catalyst-Aided Amine Solvent Regeneration

CO₂ capture from flue gas using the amine-based post-combustion technique is costly because of the high energy requirement for solvent regeneration. The addition of catalyst to the regeneration step can overcome this drawback. In this study, we investigate the regeneration performance of CO₂-rich MEA solution without and with two solid metal oxide catalysts - ZrO₂ and ZnO - within a temperature range of 40-86 °C. The solvent regeneration performance was evaluated in terms of CO₂ desorption rate, total amount of desorbed CO₂, solvent cyclic capacity, and CO₂-lean loadings achieved from the catalytic solutions in comparison with the noncatalytic MEA solution. To understand and support the obtained results BET, NH₃-TPD, pyridine-FTIR, and ¹³C NMR characterization techniques are performed. The obtained results suggest that both catalysts are capable of optimizing the solvent regeneration by desorbing up to 32% greater amounts of CO₂, improving the CO₂ desorption rate up to 54%, and increasing the solvent cyclic capacity up to 56%. On the basis of the obtained experimental and characterization results, a possible mechanism for metal oxide catalyst-aided MEA regeneration process is proposed. The stabilities of both catalysts are confirmed by 5 cyclic solvent regeneration experiments. Additionally, by studying the CO₂ absorption in MEA in the presence of catalyst, it has been investigated if the catalysts induce any undesired activity in the CO₂ absorption step. Catalytic regeneration of amine solvent can pace up the construction of large-scale CO₂ capture plants by economizing the process.