低温煤焦油中正十二烷-甲苯-苯酚的相平衡及分离

Phase equilibrium and separation of n-dodecane-toluene-phenol in low temperature coal tar

低温煤焦油组分的分离对其充分利用具有重要的作用。分别以正十二烷、甲苯和苯酚为模型化合物,采用实验和Aspen Plus模拟两种方法得到了低温煤焦油中脂肪烃-芳烃-酚类三元体系的液液平衡关系,并模拟了N,N-二甲基甲酰胺(DMF)水溶液萃取分离该体系时的典型三元相图。结果表明,Aspen Plus采用UNIF-LL法模拟得到的三元相图与实验测定结果吻合较好。甲苯在正十二烷-甲苯-苯酚体系中作为共溶溶剂,促使三元体系成为均相。根据正十二烷、甲苯和苯酚在DMF中的溶解性差异,结合Hansen溶度参数理论,通过在DMF中添加不同含量的H_2O以调节萃取剂的极性,可使正十二烷和甲苯依次从均相体系中分离。通过对萃取温度、剂油比和萃取剂含水量进行优化,最终在303.15 K,剂油比为1.5时,以DMF对模型油进行单级萃取,可以得到纯度为93.2%的正十二烷;相分离后向萃取相中添加DMF量30%的H_2O,可分离出纯度为93.4%的甲苯。

The group separation of low temperature coal tar(LTCT)is important for its effective utilization.With n-dodecane,toluene and phenol as model compounds,the liquid-liquid-equilibrium(LLE)of alkane-aromaticsphenol ternary system in LTCT were obtained by experimental method and Aspen Plus simulation.The LLE of typical ternary systems during separation of the mixture by N,N-dimethylformamide(DMF)water solution were also simulated.The results show that the ternary phase diagram simulated by Aspen Plus through UNIF-LL model fit well with experimental data.Toluene as a cosolvent promotes n-dodecane-toluene-phenol to be a homogeneous system.According to the solubility difference of n-dodecane,toluene and phenol in DMF and with the Hansen solubility parameters theory,n-dodecane and toluene can be separated successively from their homogeneous mixture by DMF in which different content of water were added to adjust the polarity of solvent.Based on the optimization of extraction temperature,solvent/oil ratio and water content in solvent,n-dodecane with 93.2%purity was separated by one stage extraction with DMF,and after phase separation,toluene with 93.4%purity was obtained by adding water weighted 30%of DMF to the extract phase at 303K,1.5 solvent/oil ratio.