Fractional Extraction Of Low-rank Coal And Study On The Pyrolysis Behaviors Of Extracts And Residues

In this paper, Shengli lignite(SL) and Shenhua coal(SH) were selected as research subjects. Coal samples were successively extracted with tetrahydrofuran(THF) and 1-butyl-3-methyl-imidazolium chloride([Bmim]Cl). The structure characteristics of extracts and residues were studied, and the pyrolysis behaviors of residues and extracts were also studied to explore the contribution of different components in coal during coal pyrolysis process. Diphenylmethane, diphenyl ether and diphenyl ketone were chose to study the depolymerization behaviors of weaken bond structures of coal in ionic liquids.The results showed that the extraction yields of SL and SH were 4.6% and 7.9%,which extracted by tetrahydrofuran respectively. At the certain reaction conditions, the extraction yields of SL-THFI and SH-THFI were 18.2% and 8.4% at 150 o C for 1h with the mass ratio of THFI/[Bmim]Cl was 1:5. The results of FTIR analysis indicated that THFS contains large amounts of aliphatic hydrocarbons and oxygen-containing functional groups, and the content of aromatic in NMPS was more than in THFS. The thermal gravimetric analysis showed that the weight loss of extracts was greater than the weight loss of raw coal, the weight loss of THFS reached to 80%. The curve fitting of DTG indicated that the extracts contained a large amount of hydrogen bond, Cal-O bond, Cal-Cal bond and partial Car-Cal bond.The results of pyrolysis of extracts and residues indicated that the tar yield of residues were lower than raw coal, but the sum yields of tar obtained from residue and extract pyrolysis were higher than the yields of tar obtained from raw coal pyrolysis.Compared with the tar yield of raw coal pyrolysis, the sum yields of tar obtained from SL-THFI and SL-THFS pyrolysis increased 13%, and the sum yields of it from Shenhua increased 2.6%. The THFI were extracted by [Bmim]Cl, the sum yields of tar obtained from residue and extract pyrolysis increased 26% and 15.5%, respectively.The GC analysis showed that, in SL tar, the main components were phenolic compounds, about 55.36%. The content of phenolic compounds in pyrolysis tar of THFI was 65.2% and in the THFS was 65.5%. In the extraction process of [Bmim]Cl,the majority of small molecule compounds in coal were extracted, the maincomponents in pyrolysis tar of NMPI pyrolysis were aromatic hydrocarbons, the content was 71.43%. The performance on the extraction of SH in the Ionic liquids[Bmim]Cl was not obvious, the major components of pyrolysis tar of its extracts and residues were phenolic compounds.Depolymerize performance of model compounds with different structures were quite different. The results showed the bridge bond cleavage order was At 150?, the mass ratio(model compound A: model compound B: [Bmim]Cl) was 1:1:2, the conversions of diphenyl ketone and diphenyl methane are 54.1% and 49.5%, respectively. The extent of bridge bond cleavage were enhanced, the presence of carbonyl group promoted the cleavage of methylene group.Under the same conditions, the conversions of diphenyl ether and diphenyl methane were 64.2% and 48.9%, and the conversions of diphenyl ether and diphenyl ketone were 40.7% and 54.9%.