Changes in oxygen-functional moieties during sequential thermal dissolution and methanolysis of the extraction residue from Zhaotong lignite

Abstract

Zhaotong lignite-derived residue was inflicted to successive thermal dissolution and methanolysis (STD/M) in cyclohexane and CH3OH, respectively, at different temperatures. To investigate the variation of oxygen-functional moieties (OFMs), extraction residue (ER) and the residue (RSTD/M) from the STD/M were characterized with a X-ray photoelectron spectrometer, solid-state 13C nuclear magnetic resonance spectrometer, Fourier transform infrared spectrometer, and thermogravimetric analyzer. Meanwhile, the soluble portions from ZL methanolysis were identified by a Fourier transform ion cyclotron resonance mass spectrometer coupled with an electrospray ionization source. The results show that the cleavage of >Calkyl-O-, especially XnC6H5-nO−CH2CH2- linkages significantly proceeded during ER methanolysis. According to the Curie-point pyrolyzer-gas chromatography/mass spectrometric analysis, the number of compounds detected in the flash pyrolysis of ER is much more than that of RSTD/M. The investigation of organic oxygen transformation during ZL methanolysis will be beneficial to the utilization of oxygenated chemicals in lignite-derived liquids.