Changes in nitrogen functionality due to solvent extraction of coal during HyperCoal production

We used X‐ray photoelectron spectroscopy (XPS) to examine structural changes in the chemical form of nitrogen in coal induced by thermal extraction with organic or industrial solvents (HyperCoal (HPC) production). Changes during solvent extraction depended on the chemical form of nitrogen in the coal. HyperCoal nitrogen primarily consisted of pyrrole nitrogen (pyrrole‐N), with less pyridine nitrogen (pyridine‐N) and no quaternary nitrogen (quaternary‐N). The extracted residue contained pyridine‐N and quaternary‐N as well as pyrrole‐N. Quaternary‐N decreased during extraction, while the amount of pyridine‐N increased, and relatively a little change was observed in pyrrole‐N. It is thought that much of the quaternary‐N decomposed during thermal extraction and was converted to pyridine‐N.

► Structural changes of nitrogen in coal by thermal extraction were examined.
► XPS was used to examine the changes of pyrrole, pyridine, and quaternary nitrogen.
► The changes during solvent extraction depended on the form of nitrogen in the coal.
► Much of the quaternary nitrogen decomposed and was converted to pyridine nitrogen.