Investigation on the composition of soluble portions from the extraction residue of Hanglaiwan subbituminous coal by thermal dissolution and alkanolyses

Abstract

Solvent extraction (SE) of Hanglaiwan subbituminous coal (HSBC) was conducted with isometric carbon disulfide/acetone mixed solvent to obtain an extract, i.e., soluble portion 1 (SP1) and extraction residue (ER). Thermal dissolution (TD) and alkanolyses of the ER were carried out at 300 °C in cyclohexane (CH), ethyl acetate (EA), methanol (M), and ethanol (E), respectively, to obtain soluble portions (SPs) 2–5 (SP2-SP5), which were analyzed with a gas chromatograph/mass spectrometer (GC/MS), Fourier transform infrared spectrometer (FTIRS), and quadrupole exactive orbitrap mass spectrometer (QPEOTMS). According to the analysis with GC/MS, the yields of SP4 (25.2%) and SP5 (38.6%) are much higher than those of SP2 (2.6%) and SP3 (7.1%), and SP1-SP5 are rich in alkylbenzenes (ABs), while the semiquantitative analysis with FTIRS suggests that the cleavage of weak and medium-strength covalent bonds, especially oxygen-containing bridged bonds, should be the main reaction during the TD and alkanolyses. For O1-O6 class species detected with QPEOTMS, O1-O2 class species dominated in SP1, SP2, SP4, and SP5, while O2 class species are predominant in SP3. The main O1 class species are alkyl-substituted arenols (ASAs) and acetophenones (APsII), while the O2 class species mainly consist of fatty acids (FAs), alkyl-substituted hydroquinones (ASHQs), methyl alkyl-substituted benzoates (MASBs), and arenediols. This investigation provides an effective approach for understanding the composition of the macromolecular networks (MMNWs) in HSBC.