Baiyinhua
lignite (BL) was sequentially extracted and thermally
dissolved in isometric CS2/acetone and toluene/methanol
binary solvents to obtain an extract in isometric CS2/acetone
(EICA) and a soluble portion (SP) in isometric toluene/methanol
(SPITM). The yields of EICA and SPITM are notably higher than the total extract yield from sequential
extraction with CS2 and acetone (or acetone and CS2) and the total SP yield from sequential thermal dissolution
in toluene and methanol (or methanol and toluene), indicating that
there exists an obvious synergic effect between CS2 and
acetone during the extraction and between toluene and methanol during
the thermal dissolution. EICA and SPITM mainly
consist of hydrocarbons and oxygen-containing organic species, respectively.
Little difference in Fourier transform infrared spectroscopy spectra
of BL and its extraction residue was observed, while the intensities
of absorbances assigned to the phenolic OH, CO, and C–O/C–O–C
groups of the thermal dissolution residue are obviously lower than
those of BL and its extraction residue. X-ray photoelectron spectroscopy
analysis shows that C–O/C–O–C groups in BL remarkably
decreased after thermal dissolution, corresponding to the abundant
phenols dissolved in SPITM. The difference in weight loss
between BL and its extraction residue is close to the yield of EICA, while the difference in weight loss between extraction
and thermal dissolution residues is significantly lower than the yield
of SPITM.
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