Characterization of the thermal dissolution products of a subbituminous coal at different temperatures

The thermal extracts and residues of Shenfu subbituminous coal (SC) obtained from thermal dissolution in 1-methylnaphthalene (1-MN) at different temperatures were characterized by FT-IR, thermo-gravimetric (TG) analysis, GPC and synchronous fluorescence spectrometry. The results show that the thermal extracts contain more amounts of aliphatic compounds than residues. Almost all of the ash is transferred into the residue. TG analysis shows that there exists a significant difference between SC and its residues. With the thermal dissolution temperature increasing from 300 to 360 ℃, the number-average molecular weight of thermal extract increases; however, it decreases at 380 ℃. The condensed aromatic ring number of thermal extract increases with the thermal dissolution temperature rising. When the thermal dissolution of SC was carried out at temperature below initial pyrolysis temperature of SC, the thermal dissolution is dominated by the solvation of 1-MN with coal to break the non-covalent bonds in SC. The light components such as ketone and ester are easy to be released at this temperature. For thermal dissolution carried out above the initial pyrolysis temperature of SC, the pyrolysis of side chains and bridged bonds in SC and condensation reactions of free radicals take place, resulting in an increase of three-fused ring structure in thermal extract.