【作者】 李雪梅；

【导师】 李春喜；

【作者基本信息】 北京化工大学 ， 化学工程与技术， 2012， 博士

【摘要】 离子液体是一类新型化合物，独特的阴、阳离子构成使其拥有与传统分子溶剂不同的特性：室温呈液态，为工业操作过程的加料和储运带来了便利；良好的热稳定性和不易挥发特性，使其在使用过程中更加安全、环保，易于纯化和循环利用。本论文重点测定了含离子液体体系汽液平衡数据、研究了相关热力学模型，并对乙醇水溶液的萃取精馏进行了概念设计和过程模拟。利用酸碱中和法合成了三种亲水性离子液体，即：单乙醇胺甲酸盐（[HMEA][HCOO]），二乙醇胺甲酸盐（[HDEA][HCOO]）和三乙醇胺甲酸盐（[HTEA][HCOO]）。利用¹³C NMR和¹H NMR鉴定了室温离子液体[HMEA][HCOO]和[HDEA][HCOO]的结构和纯度（x≥99%）；热重－差热分析结果显示，二者的热分解温度均在424K以上。可见，本文合成的醇胺类甲酸盐纯度较高、热稳定性较好；经溶解性试验，二者与乙醇、甲醇和水互溶，可用于醇－水体系的精馏分离。醇胺的价格不足咪唑价格的1/10，甲酸为大宗商品，因此醇胺甲酸盐离子液体具有价格优势，而且分子中不含卤素，无生物毒性，具有工业应用前景。采用CL-II型沸点仪，利用非分析拟静态方法，测定了不同离子液体含量和温度范围内，由离子液体[HMEA][HCOO]或[HDEA][HCOO]与乙醇、甲醇、水组成的6个二元体系和6个三元体系的饱和蒸汽压。离子液体的加入可以降低溶剂的蒸汽压，但对不同溶剂降低作用不同，同一种离子液体在相同的条件下与水的作用最强，与乙醇的作用最弱；甲醇和水与离子液体组成的二元体系对拉乌尔定律呈负偏差，非理想性随离子液体浓度的增加而增大；乙醇与离子液体组成的二元体系在离子液体浓度低（w≤0.1）时，对拉乌尔定律呈负偏差，随离子液体浓度的升高，对拉乌尔定律呈正偏差。利用NRTL模型，对测得的二元、三元体系汽液平衡数据进行了关联，关联的平均绝对相对偏差分别为0.62%和0.82%。基于二元NRTL模型参数，对含离子液体的醇－水体系等压汽液平衡相图进行了预测。结果表明：（1）所研究的两种离子液体均能显著影响乙醇对水的相对挥发度，并且对乙醇呈盐析效应；（2）随溶液中离子液体浓度的增加，共沸点逐渐向乙醇浓度增大的方向移动，当离子液体的浓度达到10wt%以上时，可以消除乙醇－水体系的共沸现象；（3）在富乙醇区，五种醇胺盐离子液体均对乙醇呈“盐析”效应；但在富水区呈“盐溶”效应；其盐效应作用顺序依次为：[HMEA][BF₄]<[HDEA][HCOO]<[HMEA][HCOO]<[HDEA][BF₄]<[HTEA][BF₄]。基于基团贡献思想，借鉴质量连接指数概念和电荷笼罩假设，改进了密度简捷计算模型；提出了新的基团划分方法（将与大π键等稳定结构，如咪唑环和吡啶环，紧密相连的原子团划为一个中心基团；将中心基团和与之相连的第一个支链基团划成一个大的基团）和质量连接指数计算方法。新模型对54种离子液体的密度预测的最大绝对偏差为1.83%，而原模型预测的最大绝对偏差为4.08%，新模型的预测精度较原模型提高55%。离子液体不易挥发，以往的研究工作中大多忽略其蒸汽压的存在。本文利用GC-PT模型对离子液体的蒸汽压进行了预测，并首次在精馏过程模拟中考虑了离子液体蒸汽压的影响。计算结果表明，在整个精馏过程中，离子液体的损耗不足0.001（质量分数）。利用Aspen Plus软件，对离子液体－醇－水体系的精馏分离过程进行了概念设计和过程模拟，考察了溶剂比、回流比等参数对分离效果的影响，确立了精馏工艺条件。与乙二醇为萃取剂的精馏过程相比，分离效果相同的前提下，再沸器热负荷降低28%，产品中萃取剂的夹带量降低了4个数量级，具有明显的节能效果。对工业酒精的分离模拟结果显示，当离子液体达到一定浓度时，工业酒精中的甲醇由轻组分变成重组分，与离子液体和水一起在塔釜富集，从而实现利用一个精馏塔由工业酒精制取无水乙醇的过程。可见，醇胺盐离子液体是一类制备方法简单、价格低廉、安全环保的新型萃取剂，可望用于乙醇－水的工业精馏分离过程。更多还原

【Abstract】 As a kind of novel compounds, Ionic liquids （ILs） show manyunique properties in comparison with traditional molecular solventsbecause of their unique structure. Most of ILs are liquid at roomtemparature, which make them convenient for feeding and transport andthus for industry use. ILs also show good thermal stability and negligiblevapor pressure, which make them more environmental benign, safe foruse and easy for regeneration. This thesis mainly focuses on measurementof vapor-liquid equilibrium, thermodynamic modeling of theexperimental data, as well as process simulation for alcohol-water-ILdistillation systems at varying conditions.Three hydrophilic ILs, viz. mono-（2-hydroxyethyl） ammoniumformic [HMEA][HCOO], di-（2-hydroxyethyl） ammonium formic[HDEA][HCOO] and tri-（2-hydroxyethyl） ammonium formic[HTEA][HCOO], have been synthesized via acid base neutralizationreaction. Their structures are identified by¹³C NMR and¹H NMR and the purities are estimated above0.99（mole fraction）. Their thermal stabilitiesare studied by TG-DTA, and their decomposition temperatures are allabove424K. In summary, the ILs can be used in the separation ofalcohol-water system for their good dissolubility in ethanol, methanol andwater. The ILs synthesized show other advantages like low cost and leasttoxicity to the environmemt.Using vapor-liquid equilibrium still （CL-II）, vapor pressure atvarying IL contents and temperatures were measured for6binary and6ternary systems containing an IL and ethanol, methanol and water. Theresults indicate that ILs can depress the vapor pressure of the solvent butto differing degree with respect to different solvents. For an IL at fixedother conditions its effect is the strongest to water and weakest to ethanol.The binary systems of IL with methanol and water all show a negativedeviation from the Raoult’s law, and the non-ideality increases with theincreasing IL-content. The ethanol-IL binary system shows a negativedeviation from the Raoult’s law in the lower IL content region（w≤0.1）,but also a positive deviation in the higher IL content region.The NRTL model was used to correlate the vapor pressure data ofbinary and ternary systems with the average absolute relative deviation（AARD） of0.62%and0.82%, respectively. Based on NRTL parameters,isobaric vapor-liquid equilibrium for ethanol-water has been estimated.The results indicate that （1） both ILs can enhance the relative volatiles of ethanol to water, and showed a salting-out effect to ethanol.（2） Theazeotropic point for the ethanol-water mixture shifts upwards as theincrease of the IL-content, and finally removed completely as ILconcentration above10wt%.（3） All5ILs based on （2-hydroxyethyl）ammonium showed a salting-out effect for ethanol aqueous solution inthe ethanol-rich region, but showed a salting-in effect in the water-richregion, and their salt effect follows the order of [HMEA][BF₄]<[HDEA][HCOO]<[HMEA][HCOO]<[HDEA][BF₄]<[HTEA][BF₄].Based on group contribution method and the ionic screening chargeconcept, the group segmentation method was improved, and accordinglythe accuracy of the density model with mass connectivity index parameteris increased greatly. The applicability of the present model was furthertested for54different ILs in a wide temperature range, its biggestinaccuracy is found to be1.83%, while the biggest inaccuracy is4.08%for the original model.Vapor pressure of ionic liquids is generally neglected in previousresearches due to their extremely low volatility. However, Vapor pressurehas been estimated here by the GC-PT equation of state, and integrated tothe present simulation process for the first time. As indicated by thesimulation results, the loss of ionic liquids in the separation process isnegligible being lower than0.001in terms of mass fraction.Concept design and process simulation were made for the extractive distillation separation of ethanol-water-IL system using Aspen Plussimulation software, the influences of process parameters, e.g. solventratios and reflux ratio, on separation effect were investigated, and theoptimal distillation conditions were determined. The separationperformance of ionic liquid and conventional glycol solvent is comparedand analyzed in terms of product purity and energy consumption. It isshowed that the heat duty of the reboiler using ionic liquid solventdecreases about28%, and the IL entraiment in distillate is lowered by4orders of magnitude in comparison with the conventional glycol solvent,showing a promising energy saving effect. Under the help of ionic liquids,the methanol component in the industrial ethanol solution is convertedfrom a lighter to a heavier component, and accumulated in the reboilertogether with the ionic liquid, which is helpful to obtain anhydrousethanol without methanol contamination.In conclusion, the （2-hydroxyethyl） ammonium based ionic liquidsare a novel class of extractive solvents with the advantages of facialpreparation, lower price, environmental benign, and safe for use, so it isexpected to be useful as solvents in ethanol-water separation process.更多还原