Thermal Dissolution of Shengli Lignite in Isometric Methanol and Ethyl Acetate Mixed Solvent - Molecular Composition of the Extract and the Role of Ethyl Acetate

摘要

Thermal dissolution (TD) of Shengli lignite was carried out in isometric solvent of methanol and ethyl acetate (EA), methanol, and EA to offer the thermally soluble fractions 1-3 (F_1-F_3), respectively. F_1-F_3 were analyzed by gas chromatography/mass spectrometry and direct analysis in real-time ionization source/ion trap mass spectrometry (DARTIS/IT-MS). Phenols with 1-4 methyls are the most abundant composition in the extract. The DARTIS/IT-MS analysis shows that the main peaks of the molecular weight distribution of the extract are located at m/z 120-340, and trace signals are still observed at m/z 640. The extract yield of F_1 is higher than those of F_2 and F_3, even the sum of F_2 and F_3 yields. The roles of EA to lignite TD were investigated by experimental comparison and molecular dynamics simulation. Both the increase in nucleophilicity and the O-H bond extension of methanol due to the formation of intermolecular hydrogen bonds between methanol and EA make the nucleophilic attacking and the scission of O-H bond easier. The transesterification reaction with EA occurs during lignite TD. These results demonstrate that the TD process can be slightly adjusted by altering the microstructure and microenvironment of methanol.