Absorption and Regeneration Performance of High Potential Second-Generation AMP-PZ-MEA Solvent for Carbon Capture

In this study, the second generation of high potential AMP-PZ-MEA solvent was explored for its absorption and regeneration performance in terms of absorption capacity, cyclic capacity, and solvent regeneration heat duty. The AMP-PZ-MEA at molar ratios of 2.5:0.5:3, 2:1:3, and 1.5:1.5:3 was considered as the first-generation solvent. It was reported that an increasing of PZ:AMP molar ratio from 0.2 to 1 significantly increased absorption performance but slightly decreased regeneration performance. Thus, in the second-generation solvent development, the total amine concentration and the PZ:AMP molar ratio were increased while the concentration of MEA was minimized. This is to enhance the absorption and regeneration performance of the blends. To avoid the solvent precipitation due to too high concentration of AMP and PZ, the solvent was screen at 303 K for its precipitation at various CO2 loading of 0, 0.15, 0.25, 0.35, and 0.5 mol CO2/mol amine. It was found that most of the prepared samples were precipitated, especially at high concentration of AMP and/or PZ, 7 M total amine concentration, and CO2 loading of 0.5 mol CO2/mol amine. Interestingly, to maintain a clear solvent, the minimum possible concentration of MEA was 1.5 M and 2.5 M for total 6 M and 7 M total amine concentration, respectively. The results also showed that an addition of AMP and/or PZ induced the originally clear solvent to precipitate at a lower range of CO2 loading. To increase the total amine concentration from 6 M to 7 M, only concentration of MEA can be increased. As a result, the second-generation AMP-PZ-MEA at molar concentration ratios of (i) 2:2.5:1.5, 1.3:3.2:1.5, and 0.95:3.55:1.5 and (ii) 2:2.5:2.5, 1.3:3.2:2.5, and 0.95:3.55:2.5 were proposed for 6 M and 7 M total amine concentrations, respectively. Be noted that these proposed solvents are corresponding to the PZ:AMP molar ratios of 1.25, 2.5. and 3.75. Density of the six proposed solvents were measured over a temperature of 303-333 K and found to be in the same range with that of 5 M MEA. On the other hand, the viscosity of the proposed solvent was much higher than that of 5 M MEA but in the same range with the conventional MDEA-PZ blends. The 6 M solvents possessed slightly lower viscosity than 3.4 M MDEA + 1.2 M PZ, while the 7 M showed the same viscosity range with 4.21 M MDEA + 1.24 M PZ at 303-313 K and became lower at 313-333 K. The absorption experiment was conducted in an absorption reactor at temperature of 313 K and CO2 partial pressure of 12 kPa (total pressure of 101.3 kPa). In terms of absorption capacity (mol CO2/L-solution), the second-generation solvent was 6.7-18.9% better than the first-generation solvent and 56-71% greater than the conventional 5 M MEA. These preliminary data were very convinced but additional information on cyclic capacity and solvent regeneration heat duty should be included to comprehensively evaluate the proposed blends to be used for carbon capture. Hence, the cyclic capacity (mol CO2/L-solution) between absorption (313 K) and regeneration (363 K) conditions will be further studied. Additionally, the solvent regeneration heat duty (kJ/mol CO2) will be measured in the desorption reactor at 363 K. This additional information will be included in the conference proceeding.