A study of slow pyrolysis of one low rank coal via pyrolysis-GC/MS

This paper describes the study of one low rank coal (LRC). To investigate its molecular structure, a LRC was characterized by proximate and ultimate analyses, XRD, FTIR, Raman spectroscopy, and pyrolysis-GC/MS (py-GC/MS). The light volatile fraction of LRC was characterized via py-GC/MS. LRC's aromatic ring structures consist of 59% amorphous structures, 22% of highly ordered structures with no less than 6 rings, 16% of aromatic structures characterized by aliphatic and/or ether substitutions and 3% of substituted benzene rings. XRD results show that the crystalline unit of LRC contains 1.44 aromatic carbon atoms per aliphatic carbon atom. Aromatic cluster structures within LRC are interconnected via ether- and covalent CC bonds. Hydroxyl, ether and carbonyl functionalities give LRC its polar character. The slow pyrolysis of LRC resulted in a light volatile GC/MS detected fraction consisting of 20% aromatic ring compounds, 45% of phenolics, 30% of aliphatic hydrocarbons and 5% O-compounds, of which the concentration, evolution and nature were dependent on the heating rates and end temperatures. Generally, slow pyrolysis of LRC at 700 °C yielded the highest concentrations of unsaturated acyclic hydrocarbons, aromatics and phenolics.