A DFT Study of Methane Adsorption on Nitrogen-Containing Organic Heterocycles

In coal, nitrogen exists in a variety of forms. We presented 11 compounds of different hybridization forms and nitrogen contents. Density functional theory (DFT) simulation method was employed to study the adsorption behaviors of methane on these nitrogen-containing organic compounds. The interactions were studied and characterized by their adsorption energies, Mulliken charges and electrostatic potential surfaces. The adsorption energies varied from 3.81 to 6.82 kJ.mol(-1), attributable to the weak hydrogen-bonding and electrostatic interactions. The results revealed that the adsorption energy of sp(2)-N with methane was higher than that of sp(3)-N and that higher nitrogen contents provided more positive sites for methane adsorption.