萃取蒸馏脱除油品中硫的过程模拟与优化

汽车尾气严重污染环境，为了生产满足环保法规的硫含量低于10μg/g的汽油，提出了在传统的萃取蒸馏中以有机溶剂+离子液体（IL）为复合萃取剂的脱硫法。以与真实催化裂化（FCC）汽油组成及物性相近的模型油为模拟汽油，利用COSMO-RS模型计算了30种常见IL对环己烷-噻吩的选择性和溶解能力，筛选出用于萃取蒸馏脱硫添加剂的最佳离子液体为[EMIM][BF₄]。通过Aspen Plus软件以N-甲酰吗啉（NFM）+[EMIM][BF₄]为复合萃取剂进行了汽油脱硫的工艺流程模拟与优化。优化结果为萃取剂由NFM（质量分数98%）和[EMIM][BF₄]（质量分数2%）构成，萃取蒸馏塔质量回流比R=0.4，剂油质量比S/F=1，采出率为70%。模拟结果表明：萃取蒸馏可高效地脱除苯并噻吩、硫醚及噻吩类硫化物，上述硫化物总量可从1581μg/g降低至5.37μg/g，脱硫率达98.1%，质量收率为70%，体积收率为75%。此外，通过对比计算值与文献中实验值，验证了COSMO-RS预测IL热力学性质、UNIFAC预测有机硫化物-烃类汽液相平衡的准确性和模拟工艺流程的可靠性。

Desulfurization of oil products by extractive distillation:simulation and optimization

Automobile exhaust leads to serious pollution,a mixture of organic solvent and ionic liquid(IL)was proposed as the mixed extractant to produce clean gasoline whose sulfur content below 10μg/g. The composition and property of model gasoline neared real FCC gasoline during the simulation. The selectivity and solubility of 30 kinds of normal ILs to cyclohexane-thiophene system were calculated by COSMO-RS model,and [EMIM][BF₄] might be the most suitable IL as entrainer with N-formylmorphol(NFM). Then simulation and optimization of extractive distillation process were carried out by Aspen Plus,which used NFM and [EMIM][BF₄] as mixed extractant. The optimized results showed the extractant was composed of NFM(98wt%) and [EMIM][BF₄](2wt%),reflux mass ratio was 0.4 for extractive distillation column,recovery ratio was 70% and the mass flow ratio of solvent to feed was 1. The method of extractive distillation could remove benzothiophene,thioether and thiophenes effectively,and the content of these sulfides could be decreased from 1581μg/g to 5.37μg/g in model gasoline,desulfurization efficiency was 98.1%,the distillate could reach up to mass yield 70% and volume yield 75%. Moreover,the prediction accuracy of COSMO-RS model in thermodynamics of IL,UNIFAC model in vapor-liquid equilibrium of organic sulfur compounds -hydrocarbon system and the reliability of simulation process were tested by comparing calculated value and experimental value in literature.