Insight into the molecular structure of Huolinguole lignite via supercritical methanolysis and ambient characterisation

Supercritical methanolysis of Huolinguole lignite (HL) was carried out at 300°C. The raw coal and the corresponding dried supercritical methanolysis product/residue were characterised using a time-of-flight mass spectrometry (TOF MS) equipped with a direct analysis in real time (DART) ion source to obtain molecular structure feature of HL. Fast and accurate characterisation of molecular information was realised by the combination of DART and TOF MS. A bunch of scattered small molecules with molecular weight from 350 to 500 Da were separated from the macromolecular network of HL by supercritical methanolysis. Desorption and ionisation under ambient condition allowed the detection of small molecules scattered inside the macromolecular network of HL, which are hard to be characterised by other analytical methods at the molecular level. The distributions of carbon number and double bond equivalent for the extract are 3 to 60 and 0 to 25, respectively, which are much wider than those for raw coal, filter cake ...