Insightful analysis of physical properties, kinetics, absorption capacity, and regeneration heat duty of monoethanolamine and N-methyl-4-piperidinol blended solvent in post-combustion carbon capture

In this study, the high potential tertiary N-methyl-4-piperidinol or MPDL (0.25–1.00 M) was blended with 5 M monoethanolamine (MEA) to formulate 5.25–6.00 M MEA-MPDL solvent and compare with the benchmark 5 M MEA. It was found that the density and the Henry’s constant slightly decreased, while the viscosity increased as the MPDL concentration in the blend increased. Even though the equilibrium CO₂-loaded viscosity considerably increased (by 34.3–40.2%) as the MPDL content increased, it was still in a great operating region of less than 10 mPa.s. Experimental overall reaction kinetics constant (k_ov) was well corresponding with the zwitterion mechanism of MEA and the base-catalyze hydration mechanism of MPDL based absorption kinetics model, with %AAD of 0.56%. Interestingly, an addition of MPDL into 5 M MEA slightly enhanced k_ov (1.2–3.3% increment) and considerably favored absorption capacity (13–31% elevation), and regeneration heat duty (28–47% reduction), respecting 5 M MEA. The proposed strategic blending can maintain the overall solvent reactivity at the same level of the benchmark, while obviously increase the absorption capacity and largely reduce the regeneration heat duty. This highly favors a solvent upgrading for the existing 5 M MEA based CO₂ capture plant. According to the recent data, 5 M MEA + 1.00 M MPDL was suggested. Since the blend was formulated at high concentration, its corrosiveness should also be considered. Graphical abstract: (Figure presented.)