There is a particularly high consumption of coal and its liquid products, which has accounted for 70% of Chinese primary energy consumption. Coal is also one of the most chemical complicated natural mixtures with heterogeneity, non-crystallization and insolubility. The need for clean and effective combustion and liquidation process of coal has motivated the research upon its composition[1]. N-methyl-2-pyrrolidinone (NMP) has been found to be a strong solvent for coal extraction due to its comparatively higher soluble fraction yield than others, no matter for single[2] or co-solvents[3]. The fact of a large quantity of extractable substance existing in coal has challenged the concept of two-phase model of coal structure[4]. But the molecular compositions of NMP extracts are rarely investigated such as molecular weight. Herod et al. use size-exclusion chromatography (SEC) to estimate the molecular weight of coal tar pitches[5]. The upper mass limit of coal tar pitches was 1500 Da with THF as mobile phase, but it was 40000 Da for NMP[6]. Thus, NMP elution may provide a new or incorrect insight upon the composition of coal. The molecular composition of coal extracts with solvent such as carbon disulfide (CS2), methanol, 1-methylnaphthalene (1-MN) usually be investigated by mass spectrum like GC-MS.[7] However, GC-MS are hard to be applied upon NMP extracts since NMP has a high boiling point, strong polarity and its extract has a poor dissolving ability in other solvents. The appearance of electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) provides new insights into the constitution of coal-derived products due to its direct liquid injection and high resolution. Marshall and co-workers[8] applied ESI FT-ICR MS to analyze pyridine extracts of coals. Various molecules with different “class” (number of heteroatoms) and “type” (rings plus double bonds) was identified by ultrahigh resolution mass spectrometry. In this work, lignite coal derived NMP extracts were obtained and characterized to reveal the molecular composition of these “mysterious” fractions by using high resolution FT-ICR MS.

Molecular characterization of N-methy-2-pyrrolidone (NMP) extracts from a lignite coal

251st National Meeting (2016)

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