Thermal extraction of lignite in ionic liquid and separation and characterization of its extracts

Based on the high efficient depolymerization performance of lignite in ionic liquids, thermal dissolution behaviors of 3 lignites Xianfeng (XL), Xilinggele (XLGL) and Shengli (SL) were investigated. And the thermally dissolved products from XL extracted by ionic liquid 1-butyl-3-methyl imidazole chloride (BmimCl) were separated and analyzed to explore the structure information of the lignite. It is found that the extraction yield of 3 lignites in ionic liquid BmimCl is significantly different under the same extraction conditions. The order of extraction yield is: XL > SL > XLGL. The thermally dissolved products of XL during extraction in BmimCl can be separated into acetone-soluble (15.9%), pyridine-soluble (56.0%), and pyridine-insoluble (28.1%), respectively. Acetone soluble (AS) mainly contains long chain fatty compounds, tricyclic aromatics and tetracyclic aromatic compounds. Pyridine soluble (PS) and pyridine insoluble (PI) mainly contain tricyclic aromatics and pentacyclic aromatics.