Abstract: In order to study the solvent extraction law of heavy aromatic hydrocarbons in coal tar,the experiment of single solvent,compound solvent,single stage extraction and multistage extraction were carried out with the fraction of 220 to 270℃in products generated by hydrogenation of coal tar as raw material.The results show that N,N-dimethylformamide(DMF)has the best solubility for aromatics among the six kinds of single extractants,the distribution coefficient of heavy aromatics is as high as 0.28,and the content of aromatics in the residual phase decreases from 40.00%of raw materials to 10.65%.Although the distribution coefficient of heavy aromatic hydrocarbons extracted by dimethyl sulfoxide(DMSO)is equivalent to that of sulfolane(SULF),the separation factor is as high as 75.00%,whichhas good selectivity for heavy aromatics.The DMSO and DMF belong to non-proton polar solvents,and the dielectric constant and dipole moment are larger,so the polarity is stronger,and their solubility and selectivity to aromatics are better than TRIG.The DMF contains N—C and C■O groups,which has strong solubility.But the solvent containing—S—group usually have good selectivity,so the selectivity of DMS is better than that of DMF,nevertheless,because the DMSO contains S■O conjugated double bond group,the solubility of DM-SO to aromatics is only inferior to that of DMF.When the blended solvent extraction experiment is carried out with DMSO as the main extractant and 20%DMF as assistant,the distribution coefficient of heavy aromatic hydrocarbons increases from 0.09 of the single extractant to 0.15,the separation factor decreases from 74.49%of the single extractant to 53.45%,and the extraction efficiency of heavy aromatics increases,but it also increases the loss of some cycloparaffin.The total heavy aromatics content decreases to 8.70%through three stages extraction of compound solvent,and the bicyclic aromatics and tricyclic aromatics are easier to be extracted,but the content of mono cyclic aromatic hydrocarbons is still as high as 8.20%.The content of the indan and tetralin in the mono aromatic hydrocarbons decreases to 2.80%from 18.20%of the raw materials and the total extraction rate is 84.60%.The content of indene is reduced from 14.90%to 1.30%,and the total extraction rate is 91.30%.However,the content of alkylbenzene in raw materials is only 6.70%.Through three stages extraction,the content of alkylbenzene dropps to 4.10%,and the total extraction rate is only 38.80%.The main reason for the low extraction efficiency is that alkylbenzene compounds in mono aromatic hydrocarbons are difficult to be extracted by conventional polar solvent.The main structural characteristics of alkylbenzene in the first ring aromatic hydrocarbon above C_9are that the side chain of benzene ring has long alkyl or naphthenic groups,such as phenyl cyclohexane,methyl phenyl cyclohexane,etc.For one thing,the side chains of non-aromatic hydrocarbons on the benzene ring are long or complex,which are quite different from the main extractant DMSO.For another thing,compared with the polarity of other cyclic aromatic compounds such as tetrahydronaphthalene and indene,the polarity of alkylbenzene has a greater difference with that of DMSO.Therefore,the solubility of alkylbenzene in DMSO is weaker than that of tetrahydronaphthalene and indene due to the difference of structure or polarity.