Study on the Mechanism of H<sub>2</sub>S Adsorption by Different Functional Groups of the Coal Surface Based on Density Functional Theory, Gran Canonical Monte Carlo, and Molecular Dynamics
Jinzhang Jia, Yinghuan Xing
Abstract
In order to reveal the relationship between different functional groups and the adsorption performance of H 2 S molecules at the molecular level and to investigate the influence mechanism of H 2 S molecule adsorption characteristics, Materials Studio was used to study the adsorption characteristics of different functional groups: hydroxyl, carboxyl, carbonyl, ether bond, pyridine, pyrrole, thiophene, methyl, benzene, mercaptan, thioether, sulfone, and sulfoxide on H 2 S gas based on the methods of grand canonical Monte Carlo (GCMC), molecular dynamics (MD), and density functional theory (DFT). Research has shown that the absolute values of adsorption energy, from high to low, are Ph–COOH > Ph-pyridine > Ph-pyrrole > Ph–OH > Ph–C–O–C > Ph–C═O > Ph > Ph-methyl > Ph-sulfoxide > Ph-mercaptan > Ph-sulfone > Ph-thioether > Ph-thiophene > H 2 S–H 2 S. The adsorption of H 2 S by functional groups is the result of a combination of physical and microchemical adsorption. In the early stage of adsorption, functional groups attract H 2 S gas molecules through electrostatic and van der Waals forces, causing H 2 S molecules to approach the functional group. When approaching the hydrogen bonding range of 0.26–0.31 nm, electron transfer occurs between functional groups and H 2 S molecules, and hydrogen bonding occurs between carboxyl, carbonyl, hydroxyl, pyridine, sulfone, and sulfoxide functional groups and H 2 S molecules, resulting in microchemical interactions. The potential energy curves of functional groups and H 2 S molecules conform to Lennard-Jones theory, and the order of saturated adsorption capacity and adsorption energy is consistent. H 2 S molecules have obvious layering characteristics in narrow pores.