Characterization of Coals with Different Maturity by TGA and Py-GC/MS

Thermogravimetric analysis (TGA) and pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) are used to analyze the pyrolysis process and pyrolysis products of six kinds of coals with different maturities. TGA results show that the thermogravimetric curves of six kinds of coals are similar and there are three obvious peaks of weightlessness rate in the derived thermos gravimetric (DTG) curves. Each DTG curve can be fitted by a set of sub-curves and each sub-curve is attributed to the breaking of some covalent bonds in the coal. The trends in peak temperature indicating that the decrease of coal maturity promoted the occurrence of pyrolysis. Py-GC/MS results reveal that aromatic compounds (47–95%) are the primary pyrolysis products and its content increase with the increasing of coal maturity, which indicate that high maturity coal more likely to produce aromatic compounds. However, the contents of phenolics, furans and aliphatic hydrocarbons decrease with the increasing coal maturity, suggesting that more polar O-containing compounds are released by the pyrolysis of low maturity coals. These findings are important for further understanding the large-scale and responsible utilization of coals.