Evaluating CO2 desorption performance in CO2-loaded aqueous tri-solvent blend amines with and without solid acid catalysts

Abstract

To enhance the energy efficiency of the CO2 desorption process, the regeneration behaviors of the CO2-loaded 6 M MEA-AMP-PZ (monoethanolamine, 2-amino-2-methyl-1-propanol and piperazine) tri-solvent blends with different AMP/PZ molar ratios with four different solid acid catalysts (H-ZSM-5, γ-Al2O3, SAPO-34 and SO42−/TiO2) and a blank at 96 °C were investigated in terms of CO2 desorption rate, cyclic capacity and relative heat duty. For the no-catalytic runs, the results showed that all the tri-solvent blended amines greatly increased CO2 desorption rate, cyclic capacity and decreased the relative heat duty in comparison with 5 M MEA. The 13C NMR analysis indicated that the 3 M MEA-2.5 M AMP-0.5 M PZ blend with the highest AMP/PZ ratio produced the largest amount of bicarbonate and less carbamate, which resulted in the best desorption performance. With regard to catalyst, when the solid acid catalysts were introduced, the regeneration performance of the blend was further improved. The best of the blends along with H-ZSM-5 provided the combination with the best performance in CO2 desorption, and reduced the relative heat duty by 61.6% as compared to 5 M MEA without catalyst (100%). Five relevant physicochemical properties of the catalyst were obtained and used to better understand the catalytic regeneration process. A possible catalytic CO2 desorption mechanism was analyzed. The results revealed that the mesopore surface area coupled with total acid sites of the catalyst had the most positive influence on improving the CO2 desorption performance. Findings from this work imply that the combination of solid acid catalyst with tri-solvent blended amines is a promising alternative method for further reduction of solvent regeneration energy requirement.