甲醇-碳酸二甲酯-[N_(1,1,1,1)][NTf_(2)]等压气液相平衡数据测定

Isobaric vapor-liquid equilibrium for ternary system of methanol-dimethyl carbonate-[N_(1,1,1,1)][NTf_(2)]

为了实现绿色高效萃取精馏分离甲醇-碳酸二甲酯共沸物系,以离子液体[N_(1,1,1,1)][NTf_(2)](四甲基铵双三氟甲烷磺酰亚胺)为萃取剂,测定了101.3 kPa下甲醇-碳酸二甲酯-[N_(1,1,1,1)][NTf_(2)]三元体系等压气液相平衡数据,通过非随机双液体模型(NRTL)对三元气液相平衡数据进行关联,利用过量焓分析[N_(1,1,1,1)][NTf_(2)]的作用机理。结果表明:[N_(1,1,1,1)][NTf_(2)]的加入可在富甲醇区对甲醇产生盐析效应,提高甲醇相对于碳酸二甲酯的相对挥发度,随[N_(1,1,1,1)][NTf_(2)]含量的增加,盐析效应越显著。NRTL模型关联结果与实验结果具有良好的一致性,NRTL模型计算显示,打破甲醇-碳酸二甲酯共沸点所需[N_(1,1,1,1)][NTf_(2)]的最小摩尔分数为0.0825。过量焓分析表明,[N_(1,1,1,1)][NTf_(2)]与碳酸二甲酯有更强的相互作用,因而可提高甲醇对碳酸二甲酯的相对挥发度。

Ionic liquid tetramethylammonium bis(trifluoromethanesulfonyl)imide([N_(1,1,1,1)][NTf_(2)])was tried as the extractant to achieve the green and efficient extractive distillation separation of the methanol-dimethyl carbonate(DMC)azeotropic system.The isobaric vapor-liquid equilibrium(VLE)data for the ternary system of methanol-dimethyl carbonate-[N_(1,1,1,1)][NTf_(2)]were measured at 101.3 kPa,the non-random two-liquid model(NRTL)was used to correlate VLE data,and excess enthalpy was employed to analyze the mechanism of[N_(1,1,1,1)][NTf_(2)].The experimental results show that[N_(1,1,1,1)][NTf_(2)]produces a salting-out effect on methanol in the methanol-rich region and can increase the relative volatility of methanol to dimethyl carbonate.Furthermore,the more[N_(1,1,1,1)][NTf_(2)],the stronger the salting-out effect.The correlation result of the NRTL model is consistent with the experimental result,and the minimum mole fraction of[N_(1,1,1,1)][NTf_(2)]needed to break the azeotropic point is calculated to be 0.0825.The excess enthalpy analysis shows that dimethyl carbonate has stronger interaction with[N_(1,1,1,1)][NTf_(2)]than methanol,thus improving the relative volatility of methanol to dimethyl carbonate.