Citation: HU Ru-nan, WANG Zhi-cai, LI Lei, WANG Xiao-ling, PAN Chun-xiu, KANG Shi-gang, REN Shi-biao, LEI Zhi-ping, SHUI Heng-fu. Effect of solvent extraction pretreatments on the variation of macromolecular structure of low rank coals[J]. Journal of Fuel Chemistry and Technology, ;2018, 46(7): 778-786. shu

Effect of solvent extraction pretreatments on the variation of macromolecular structure of low rank coals

School of Chemistry and Chemical Engineering, Anhui Key Laboratory of Clean Coal Conversion & Utilization, Anhui University of Technology, Ma'anshan 243002, China

Corresponding author: WANG Zhi-cai, zhicaiw@ahut.edu.cn
Received Date: 25 April 2018
Revised Date: 10 June 2018

Fund Project: the Natural Scientific Foundation of China 21476004the Natural Scientific Foundation of China 21476003the Natural Scientific Foundation of China 21476002Natural Science Foundation of Anhui Provincial Education Department KJ2016A808the Natural Scientific Foundation of China 51174254The project was supported by the Natural Scientific Foundation of China (21476004, 21476003, 21476002, 51174254), Natural Science Foundation of Anhui Provincial Education Department (KJ2016A808), the Provincial Innovative Group for Processing & Clean Utilization of Coal Resource and the Innovative Group of Anhui University of Technology

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In order to understand the effects of solvent pretreatment on the inherent macromolecular structure of low rank coal, Xilinguole lignite (XLL) and Shenfu sub-bituminous coal (SFC) were extracted by tetrahydrofuran (THF) soxhlet extraction, carbon disulfide/N-methyl-2-pyrrolidone (CS₂/NMP) mixed solvent extraction and thermal dissolution, respectively. The extracted coals were characterized by diffuse reflection FT-IR spectroscopy (DRIFT), thermogravimetric analysis (TGA), mercury intrusion method (MI) and swelling ratio determination. The results indicated that the extraction resulted in the arrangement and reassociation of coal inherent macromolecules. THF Soxhlet extraction and CS₂/NMP mixed solvent extraction can relax the macromolecular structure of coal to varying degrees by changing the non-covalent bond cross-linking, especially the distribution of hydrogen bond interactions. However, thermal dissolutions at high temperature mainly increased the covalent cross linking of coal macromolecules, especially for XLL. Swelling of all extracted coals was limited by Fickian diffusion, and the extracted coal showed lower swelling activation energy than the corresponding raw coals.
- pretreatment,
- extraction,
- macromolecular structure,
- swelling,
- diffusion
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