Metal oxide catalyst-aided solvent regeneration: A promising method to economize post-combustion CO₂ capture process

Despite the in-depth understanding of the amine-based post-combustion CO₂ capture technique gained by research efforts made over the decades, its large-scale practicality is hindered by extensive energy input in desorption and solvent degradation issues. The most thoroughly studied alkanolamine solvent, monoethanolamine (MEA), is still unable to capture a significant portion of CO₂ emissions at a bearable economic penalty, owing to these serious drawbacks. Herein, we demonstrate catalytic regeneration of MEA solvent with five commercially available metal oxide catalysts ̶ Ag₂O, Nb₂O₅, NiO, CuO, and MnO₂ which would render this process suitable for achieving a bearable penalty. CO₂-rich MEA solvent with an initial loading of 0.50 mol CO₂/mol MEA was used in this study. A temperature range of interest was selected to perform the experiments in order to identify the optimal operating temperature for each of the catalysts used in this study. The results show that all of the catalysts used in this study improve the MEA regeneration where Ag₂O presents the best regeneration performance followed by Nb₂O₅ by desorbing up to 3.6 and 2.5 times greater CO₂ amounts with faster desorption rates, respectively. Overall, the results show that the MEA solvent can be regenerated at temperature as low as 80 °C, and hence a significant reduction in heat requirement for solvent regeneration is possible. Besides, at this temperature, thermal degradation of the solvent can be avoided completely. Furthermore, as a considerable improvement in the CO₂ desorption rate and cyclic capacity is achieved by the catalytic regeneration process, the size of the stripper and the solvent circulation rate can be reduced, which will decrease the capital and operating cost as well.