Characterizing the transport properties of multiamine solutions for CO ₂ capture by molecular dynamics simulation

We performed molecular dynamics (MD) simulations on multiamine solutions of CO₂ capture to optimize the conventional amine solvents (MEA, MDEA, DEA, AMP, and TEA). A synergy molecular dynamics model (SMD) was developed for the CO₂ and amine solutions, in which the molecular synergy number (MSN) was introduced to quantify interactions between diffusion and molecule motion. The SMD model involved with the force field was validated with experimental data from CO₂, amine, and water systems. The best synergy for the MDEA-DEA-TEA system was achieved at the ratio of 3:1:1, with a minimum MSN being 3.89. The overall synergy in ternary amine systems was found to be better than that in quaternary and quintuple amine systems. Several optimized multiamine solution systems were identified. The MDEA-DEA-TEA solution could simultaneously provide better diffusivity and less drag force with mass transfer coefficient being 33.33 % higher than that of AMP. The MEA-MDEA-DEA-TEA solution could improve CO₂ transport by increasing 18 % of diffusivity when varying the ratio from 1:1:1:1 to 2:1:1:1. All of the results above provided a benchmark to optimize the amine mixing solution design for CO₂ capture.