Structural characteristics of soluble organic matter in four low-rank coals

Abstract

Four low-rank coals, Zhaotong lignite, Dayan lignite, Wucaiwan sub-bituminous coal and Shenfu sub-bituminous coal were sequentially dissolved in cyclohexane, acetone and methanol at 300 °C. An Orbitrap mass spectrometry coupled with an atmospheric pressure chemical ionization ion source was used to analyze the 12 thermal dissolution (TD) extracts from coals to obtain and compare the molecular distribution of soluble organic matter. Two statistical methods, principal component analysis and hierarchical clustering analysis, were used to mine the effective information from a large number of mass spectral data. The statistical results showed that the degree of coalification had greater effects on the structure and composition of TD extracts compared to the solvent. In-source collision-activated dissociation further elucidated the characteristics of molecular structure and revealed that most of O atoms distribute on alky chains.