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 ([Bmim]OTf) was 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 [Bmim]OTf had good performance in the depolymerization of XL when the extraction was carried out at 280°C for 4 h with [Bmim]OTf/XL at 3.5. The extraction yield of XL with [Bmim]OTf defined as tetrahydrofuran solubles (THFS) reached to 20.1%. The depolymerization of XL with [Bmim]OTf 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.