Molecular dynamics models of pores in the liquid monoethanolamine structure

Abstract

Models of liquid monoethanolamine with 1000 molecules in a basic cell in the form of a rectangular parallelepiped are constructed by means of molecular dynamics simulation in the temperature range of 293 to 453 K. The simulation is performed in the NVT mode at real densities, and in the NpT mode at p = 1 atm. Voids (pores) in monoethanolamine structure and the temperature dependences of their sizes are analyzed. It is established that the pores appear and disappear via fluctuation in different places. No dynamic relationship between them is observed; during heating, the radius of a maximal pore grows from 1.98 Å at 293 K to 2.53 Å at 453 K. The inner surface of the pores is notably enriched with oxygen and nitrogen atoms and considerably depleted of hydrogen atoms. At temperatures above 290 K, a maximal pore can freely enclose an argon atom. The pores available in monoethanolamine can freely enclose 20 mol % of helium at 293 K and 57 mol % at 453 K; the solubilities of argon are estimated as 0.1 mol % at 293 K and 6.4 mol % at 453 K. The radius of a maximal pore in monoethanolamine is greater than in ethylene glycol by ~0.1–0.3 Å.