Study on the thermal extraction of Xianfeng lignite in ionic liquid 1-butyl-3-methyl-imidazolium trifluoromethanesulfonate

The depolymerization behaviors of Xianfeng lignite (XL) in ionic liquid 1-butyl-3-methyl-imidazolium trifluoromethanesulfonate (BmimOTf) were studied in this paper. Also, the thermal extracts and residues obtained from thermal depolymerization of XL at different extraction conditions were analyzed. It was found that BmimOTf had good performance in the depolymerization of XL when the extraction was carried out at 280℃ for 4h with BmimOTf/XL at 3.5. The extraction yield of XL with BmimOTf defined as tetrahydrofuran solubles (THFS) reached to 20.1%. The depolymerization of XL with BmimOTf was promoted markedly with the addition of tetralin (THN), H₂ and ZnCl₂ catalyst, and the yield of THFS reached to 30.0%, 36.9% and 46.8%, respectively. The results showed that the amount of hydrogen bonds in thermal extracts increased significantly with the addition of THN. The contents of aromatics and aliphatic hydrocarbon were enhanced greatly under the existence of H₂ and ZnCl₂.