Effect of Solvent Pretreatment on the Flash Pyrolysis Performance of Yinggema Lignite

Abstract

Yinggema lignite (YL) was pretreated with isometric acetone/carbon disulfide mixed solvent to obtain the residue (RYL) and, then, RYL was separated by density difference with carbon tetrachloride to obtain the light residue (LRYL). The flash pyrolysis performances of YL and LRYL were analyzed by thermogravimetry–Fourier transform infrared spectrometer–Gas chromatography/mass spectrometer (TG-FTIR-GC/MS). The results showed that solvent pretreatment could remove some small molecules in the coal and swell the used coal, leading to the increase in pyrolysis reactivity. The intensity and absorption peak area of C=O from LRYL were significantly reduced compared to YL, resulting from the high hydrogen-donating ability of acetone. The main gaseous products of both samples are H2O, CH4, CO2, and CO; the hydrocarbons detected by GC/MS in the pyrolysis products of YL and LRYL at 450 °C were mainly alkanes, alkenes, and arenes, with the higher relative contents of alkanes of 31.1% and 36.2%, followed by arenes of 27.1% and 22.6%, respectively. The oxygen-containing compounds were mainly alcohols and phenols. It is speculated that the pretreated coal could expose more oxygen-containing functional groups, facilitating their conversion to phenolic hydroxyl groups during the pyrolysis process, resulting in more phenolic compounds.