氯化咪唑基离子液体对柴油中含氮化合物选择性脱除作用研究

通过N-甲基咪唑和烷基氯的季铵化反应合成出了咪唑环N上烷基取代基碳链长度或者饱和度不同的4种离子液体：氯化1-丁基-3-甲基咪唑(BMImCl)、氯化1-烯丙基-3-甲基咪唑(AlMImCl)、氯化1-苯甲基-3-甲基咪唑(BzMImCl)和氯化-1-辛基-3-甲基咪唑(OcMImCl)。以含咔唑(CAR)和二苯并噻吩(DBT)的甲苯-正十二烷烃溶液作为模拟柴油，测定CAR和DBT在这些离子液体中的相对分配系数，考察了离子液体对氮和硫化物的萃取脱除选择性。结果表明，在这些离子液体中CAR比DBT有更高的分配系数；4种离子液体比较，BMImCl和AlMImCl对CAR的分配系数分别达46和14，对氮和硫化合物的萃取脱除选择性S_N/S分别达到125和38。测定了离子液体在模拟柴油的溶解度，发现这4种离子液体在甲苯和正十二烷烃模拟柴油中的溶解度有显著的差别，其中BMImCl和AlMImCl的溶解度相当且都很小。综合结果显示BMImCl具有最佳性能。实验还比较了BMImCl对不同碱性氮杂环化合物的萃取效果，发现其对含硫化合物和碱性含氮化合物的萃取效率随着模拟柴油中甲苯的质量分数的增加而降低，而对中性含氮化合物表现出高萃取效率，且几乎不受甲苯质量分数的影响。对一种含有361 mg·kg^-1 N和3 598 mg·kg^-1 S的工业柴油，BMImCl对其对中性含氮化合物的萃取效率达到38%，而对相对含量高约十倍的含硫化合物的萃取率仅约有1.7%。综合上述结果表明，氯化1-丁基-3-甲基咪唑盐离子液体对柴油中的中性含氮化合物具有高选择性脱除作用。

Removal of N-compounds from Diesel Fuel by Using Chloridized Imidazole Based Ionic Liquids

Four kinds of ionic liquids (ILs) with different carbon chain length and saturation of N-substituent groups: 1-butyl-3-methylimidazolium chloride (BMImCl), 1-allyl-3-methylimidazolium chloride (AlMImCl), 1-benzyl-3-methylimidazolium chloride (BzMImCl) and 1-octyl-3-methylimidazolium chloride (OcMImCl), were synthesized by direct quaternization of N-methylimidazole with corresponding alkyl chloride. The distribution coefficient of carbazole (CAR) and dibenzothiophene (DBT) between the ILs phase and the model fuel phase and the extraction selectivity of the ILs for CAR and DBT were determined using a dibenzothiophene and carbazole solution in toluene and n-dodecane as a model fuel. The results show that CAR has higher distribution coefficient than DBT in these ILs phases. The CAR distribution coefficients in BMImCl and AlMImCl are 46 and 14, and the selectivity of CAR/DBT is 125 and 38, respectively. The solubility of ILs in the model fuel was determined to be remarkably different. BMImCl shows both very low solubility in the model fuel and the best extraction property for CAR. The extraction efficiency of BMImCl for some different N heterocyclic compounds was further observed. It is showed that its extraction efficiency for both S-compounds and the basic N-compounds is decreased with increasing mass fraction of toluene in the model fuel, while its extraction efficiency for neutral N-compounds is almost stable. For a diesel fuel containing 361 mg·kg^-1 of N and 3598 mg·kg^-1 of S, the BMImCl shows 38% extraction efficiency for the neutral N-compounds, while only 1.7% extraction efficiency for the S-compounds. In conclusion, BMImCl has a very highly selective extraction for neutral N-compounds in the diesel oil.