Self-diffusion coefficients of amines, a molecular dynamics study

Diffusion coefficients of amines are crucial during the modeling and the designing stages of industrial processes such as CO2 capture and gas sweetening. Nevertheless, experimental data are really scarce, and only few simulation studies have been reported. In this work, molecular dynamics simulations leading to estimate the self-diffusion coefficients for several amines have been performed at temperatures and pressures characteristic for the CO2 capture and gas sweetening processes. Three different force fields were used, namely, OPLS-AA, TraPEE-EH and a recent OPLS-AA version 1.14CM1A-LBCC. Among the main results, self-diffusion coefficients were in average better predicted by OPLS-AA 1.14CM1A-LBCC except for monoethanolamine that was overpredicted similar to 9 times despite being in excellent agreement with density, thus suggesting that the hydrogen bond interaction might be underestimated. Additionally, despite providing excellent predictions for methylamine, and trimethylamine at the studied conditions TraPPE-EH was found to be unable to reproduce the liquid phase for long chain amines at low temperatures as well as to present unphysical conformations for ethanolamine and ethylenediamine. (C) 2021 Elsevier B.V. All rights reserved.