离子液体萃取精馏技术在甲醇-碳酸二甲酯分离中的应用

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。

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

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 MeOH 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 MeOH and DMC separation.