Energy & Fuels, Vol.34, No.10, 12260-12273, 2020
Solvent Extraction of Superfine Pulverized Coal. Part 1. Composition of the Extract
The chemical properties of coal extracts play a crucial role in understanding coal structure, constructing coal model, and developing clean coal technology. However, there is little knowledge about the superfine comminution-induced mechanochemical effect on the coal extraction process and composition of the extracts. In this paper, typical solid-phase microextraction (SPME) and solvent extraction experiments were performed, which can identify both nonpolar and polar molecules in the coal structure, providing reliable structural information. Then, three different analytical methods were employed to characterize the chemical properties of the extracts, including gas chromatograph-time-of-flight-mass spectrometry (GC-TOF-MS), GC-triple quadrupole-MS (GC-QqQ-MS), and GC-MS. The final results show that the particle size has a notable impact on the composition of nonpolar molecules based on SPME. Polycyclic aromatic hydrocarbons (PAHs) were detected through GC-QqQ-MS in order to study the relation between the AMHs and coal structure. More stabilized structures of the "angular" PAHs were observed in higher ranked coals. In addition, the detailed hydrocarbons, oxygen-containing, and heteroatom-containing species were identified based on GC-MS results. The content of hydrocarbons monotonically increases with the decrease of the particle size, while the constituents with carbonyl groups such as ketone and ester also increase, shedding light on the construction of a multicomponent coal model with structural diversity. The findings from this work give a more comprehensive understanding about the particle size effect on coal extraction and provide a new perspective to understand the chemical morphology of superfine pulverized coal.