离子液体萃取精馏技术在甲醇-碳酸二甲酯分离中的应用

Separation of methanol and dimethyl carbonate azeotrope by extractive distillation using ionic liquid as solvent

针对甲醇-碳酸二甲酯共沸物分离难题,采用萃取精馏技术并以离子液体3-辛基-1-甲基四氟硼酸盐([omim][BF4])为萃取剂进行流程设计和Aspen Plus模拟。根据气液相平衡数据回归了NRTL气液模型的二元交互参数,确保模拟结果准确。通过优化萃取剂用量、最佳回流比、进料位置和闪蒸塔的工艺条件等操作参数,实现了甲醇和碳酸二甲酯有效分离,并使产品质量分数达到99.5%以上。通过与草酸二甲酯作为萃取剂的工艺进行对比,发现[omim][BF4]工艺对分离设备要求更低、萃取剂用量更小,且分离能耗相当。经济分析结果则表明,[omim][BF4]工艺塔费用和填料费用分别为草酸二甲酯工艺的78%和37%,在设备投资上具有一定优势;但工艺能耗费用增加4%,萃取剂费用为草酸二甲酯费用的6.5倍,最终年总花费与草酸二甲酯工艺相当。因此,[omim][BF4]工艺用于甲醇-碳酸二甲酯萃取精馏具有一定的应用前景。

Focused on separation of methanol（MEOH）and dimethyl-carbonate（DMC）azeotrope,the extractive distillation process employing ionic liquid 1-octyl-3-methylimidazolium tetrafluoroborate（[omim][BF4]） as solvent was designed and simulated based on Aspen Plus.To verify the reliability of simulation results,binary interaction parameters were correlated by NRTL using vapor-liquid equilibrium data.The flow rate of [omim][BF4],reflux ratio,feed stage and operation conditions of flash tower were optimized to obtain Me OH and DMC with purity above 99.5%,respectively.Compared to the dimethyl oxalate（DMO）process,[omim][BF4] process presents lower requirements for towers,lower solvent and energy consumption.Economy analysis indicates that the column cost and packing cost of [omim][BF4] only account for 78% and 37% of DMO process respectively,while the energy consumption increase 4% and solvent cost is 6.5 times higher than DMO process.As a result,the total annual cost of [omim][BF4] is comparable with DMO process.Hence,the [omim][BF4] process shows application potential in Me OH and DMC separation.