【作者】 任洪东；

【导师】 崔现宝； 杨志才；

【作者基本信息】 天津大学 ， 化学工程， 2003， 硕士

【摘要】 本文通过理论分析与实验相结合的方法,主要研究了盐效分离盐的选择、加盐液液相平衡的研究以及2-甲基吡嗪-水混合物加盐萃取工艺的研究。盐的选择是盐效分离的核心问题。本文提出了将迁移自由能与相平衡中盐效应的大小结合起来,用迁移自由能理论解释相平衡中的盐效应。采用选择性溶剂化模型,利用定标粒子理论计算盐在含水体系中的标准摩尔迁移自由能。文中计算了盐在六种含水体系的标准摩尔迁移自由能,并与其盐效应进行了对比,研究发现在含水体系中盐效应随盐的标准摩尔迁移自由能增大而增大,因此在盐效分离过程中可以采用标准摩尔迁移自由能模型选择有效的盐作为分离剂。加盐液液相平衡研究是加盐萃取过程的基础,是该工艺的关键所在。本文采用浊度法研究了含盐三元体系溶解度,对电解质在混合溶剂的溶解度与混合溶剂组成的关系进行了关联,得到对加盐萃取具有重要价值的溶解度曲线。对加盐萃取中盐的选择进行了实验研究,考察了不同种类盐分相能力的差异。加盐液液分相分为三类,有机溶剂浓度较低时为Ⅰ型:V始>V终;有机溶剂浓度较高时为Ⅱ型:V始<V终;Ⅲ型:兼有Ⅰ型和Ⅱ型二者的特征,即Ⅰ型向Ⅱ型的过渡。混合溶剂体系的pH值的改变会对加盐分相三元体系的液液平衡产生重要影响,研究发现pH>7时有利于发生液液分相,而pH<7时不利于发生液液分相。另外对加盐液-液相平衡数据关联进行了研究。测定了七个含水体系的加盐液液相平衡数据,采用混合溶剂电解质体系Chen的NRTL模型(即ENRTL模型)。利用实验数据对七个含盐体系的ENRTL模型参数进行回归,采用回归ENRTL模型参数关联加盐液液相平衡数据。关联计算结果与实验结果基本吻合。在加盐液液相平衡研究的基础上,进行了 2-甲基吡嗪(MP)-水混合物加盐萃取工艺的研究。MP-水混合物加盐萃取过程的最佳工艺条件:选用NaOH水溶液作为萃取剂,w(NaOH)=60%,萃取温度30～40 ℃,萃取比m(NaOH水溶液)/m(MP-水混合物)=0.5/1。NaOH对MP水共沸物脱水率达95.5%,萃取后有机相中w(MP)=96.1124%,并研究了NaOH水溶液作为萃取剂的稳定性,NaOH水溶液性能稳定,回收容易,可循环使用。更多还原

【Abstract】 The salt selection, salt effects on Liquid-Liquid Equilibria (LLE) and salt extraction of 2-methylpyrazine-water mixtures were studied by theoretical analysis and experiment.Salt selection is the key problem for separation process adding salt. The Gibbs free energy of transfer of salt in six ternary organic solvent-H2O-salt mixtures where salting-out phenomenon occurs at 25℃ was calculated with the solvation model and scaled particle theory. The results are compared with salt effect on Vapor-Liquid Equilibria (VLE) or LLE. In most cases, salt effect on VLE or LLE is increasing with the increasement of the Gibbs free energy of transfer of salt in systems containing water. The results show that salt effect can be explained by the theory of the Gibbs free energy of transfer. Therefore, the Gibbs free energy of transfer can be used as a guide in salt selection in separation process adding salt.LLE containing salts is a part of salt extraction. By applying turbidity analysis, the equilibrium solubility of five ternary systems of organic solvent-water-salt are determined at 25℃, and the solubility diagrams are drawn and empirical equations of solubility are regressed. The phase split ability of various organic solvent-water-salt systems was studied. There are many factors affecting the phase separation, such as the type and concentration of solvent and salts. According to the variation of organic solvent phase volumes after separation, three types of LLE containing salt have been observed: typeⅠ(Vinitial<Vend), typeⅡ(Vinitial<Vend) and typeⅢ(typeⅠand concurrently typeⅡ). The value of pH in mixed-solvent affects LLE containing salt. When pH>7 the phase split is easy; when pH<7 the phase split is difficult. LLE data for the ternary systems of organic solvent-water-salt were measured at 20 and 25℃. The experimental data of the ternary systems were correlated with the electrolyte NRTL model. The interaction parameters for the electrolyte NRTL model were estimated with the Simplex method. The calculated results are basically consistent to the experimental data.Salt extraction for separation of 2-methylpyrazine-water mixture was developed. Optimum conditions of salt extraction were investigated: w(NaOH)=60%, temperature 30-40℃,and the extracting ratio m(NaOH aqueous solution)/m(2- methylpyrazine-water mixture)=0.5/1. Under such conditions, the concentration of 2- methylpyrazine in extract phase could reach 96.11%, and dehydration ratio of 2-methylpyrazine-water azeotropic mixture was 95.5%. In addition, the stability of NaOH aqueous solution was investigated.更多还原