论文总字数：17496字

摘 要

生物法制备丁二酸一般适宜在pH 6~7.2的环境中进行生物转化与合成，需加入碱性物质（如碳酸钠，NaOH等）来中和生成的丁二酸，酸化结晶后，结晶母液中含有高浓度氯化钠（16~20%），使得存在于结晶母液中的丁二酸难以回收，影响收率。为了提高生物法制丁二酸的经济效益，本论文开展了对丁二酸高盐结晶母液中丁二酸的萃取回收研究。

本文选择磷酸三丁酯(TBP)作为萃取剂。考察了不同无机盐浓度对其萃取性能的影响，结果表明高浓度无机盐的存在有利于提高萃取性能，结晶母液中的高浓度NaCl分子可结合部分自由水分子，强化其盐析效应，有利于提高丁二酸的分配系数，通过经验公式对该盐析效应进行拟合，可用于预测该体系中的萃取平衡关系。而对pH对萃取性能的影响表明当丁二酸以分子态形式存在时，有利于与萃取剂发生氢键缔合作用，可提高萃取选择性。而温度对萃取性能的影响说明该萃取过程为放热反应，适合常温萃取。

本文研究表明：油水比越高，萃取率越高，但单位体积萃取剂负载的丁二酸越少，综合考虑，确定丁二酸结晶母液的单级萃取条件为：油水比1：1，萃取温度为25℃，萃取平衡时间为20min。在此基础上建立了基于两级萃取的策略，使丁二酸的总萃取率达到98%。

对丁二酸的反萃及萃取剂再生过程进行了研究，结果表明：热水和低浓度的丁二酸溶液均可将油相中的部分丁二酸解吸，确定反萃工艺条件为：反萃温度为90℃，反萃1h，通过三级反萃可反萃出油相中90%的丁二酸。反萃液经浓缩及冷却结晶获得的丁二酸产品，符合FCCV质量标准。丁二酸结晶母液的萃取-反萃的总回收率可达88%。以上结果说明利用TBP萃取回收结晶母液中的丁二酸具有可行性。

关键词：丁二酸 结晶母液 萃取 磷酸三丁酯 反萃

Extraction and recovery of succinic acid from crystallization mother liquor

Abstract

Succinic acid is generally suitable to bioconversion and synthetic in the environment of pH 6 ~ 7.2. The process needs to add alkaline substances(such as NaCO₃、NaOH) to counteract the generated succinic acid. Crystallization mother liquor contains high concentration of inorganic salts（16~20%） after acidification crystallization,which make it hard to recover succinic acid from crystallization mother liquor.Then it influences the yield of succinic acid. In order to increase the economic benefits of biological preparation of succinic acid, this paper has studied on the extraction and recovery of succinic acid from crystallization mother liquor.

In this article，we choose tributyl phosphate (the TBP) as extracting agent.We investigated the influence of different concentration of inorganic salt on the extraction performance, the results showed that high concentrated inorganic salt was beneficial to improve the of extraction performance. The high concentrated NaCl in crystal liquor can be combined with some free water molecules, which strengthens its salting out effect and improve the distribution coefficient of succinic acid. Through empirical formula, we fit the salting out effect, which can be used to predict extraction equilibrium in the system. The influence of pH on the extraction performance showed that when the succinic acid was in the form of molecular state, it was conducive to hydrogen bonding association with extraction agent, which can improve the selective extraction. The influence of temperature on the extraction performance showed that the extraction process was the exothermic reaction, which was suitable for normal temperature extraction.

In this paper, the extraction rate increased with the oil/water ratio, but the load of succinic acid in the unit volume extraction agent decreased. We determined that the single stage extraction conditions for crystallization mother liquor of succinic acid were as follows: water-oil ratio is 1:1, extraction temperature is 25 ℃, time of extraction equilibrium is 20 min. On the basis, two stage extraction strategy is established, which make the total extraction rate of succinic acid reached 98%.

The stripping of succinic acid and the extractant regeneration process was studied. The results show that part of succinic acid in the oil phase can be desorbed by the hot water and low concentration of succinic acid solution. We determine that the stripping process conditions were as follows: stripping temperature is 90 ℃, time of stripping is 1 hour , 90% of succinic acid in oil phase can be desorbed by three stage stripping. The product of the succinic acid obtained from the concentrated and cooling crystallization of the stripping solution, which was accorded with the FCCV quality standard. The overall recovery rate of the succinic acid crystallization liquor extraction - stripping process can reach 88%.The above results show that it is feasible to use TBP to extract succinic acid from crystallization mother liquor.

Key words: Succinic acid; Crystallization mother liquor; Extraction; Tributyl phosphate; Stripping

目 录

摘 要 I

Abstract II

第一章 文献综述 1

1.1 丁二酸性质及制备 1

1.1.1 丁二酸简介 1

1.1.2 丁二酸的制备 1

1.2 丁二酸的分离提取的研究进展 2

1.3 萃取体系的分类 2

1.4 有机酸的萃取 2

1.4.1液液萃取法 2

1.4.2络合萃取法 2

1.4.3预分散溶解萃取（PDSE） 3

1.5 本课题研究目的及内容 3

第二章 实验材料与方法 5

2.1 实验试剂 5

2.2 仪器与设备 5

2.3 实验方法 5

2.3.1 丁二酸结晶母液的萃取分离 5

2.3.2 丁二酸的反萃与溶剂再生 6

2.4 分析方法 6

2.4.1 有机酸的检测 6

2.4.2 有机溶剂萃取平衡分配系数与萃取率的计算 6

2.4.3 萃取剂丁二酸负载量的计算 6

第三章 实验结果与讨论 7

3.1 高盐体系丁二酸萃取剂的选择 7

3.2丁二酸结晶母液萃取分离的优化 7

3.2.1 盐浓度对TBP萃取性能的影响 7

3.2.2 pH对TBP萃取性能的影响 8

3.2.3 温度对TBP萃取性能的影响 8

3.2.4 丁二酸浓度对TBP萃取性能的影响 9

3.2.5 萃取时间对TBP萃取性能的影响 9

3.2.6 相比对TBP萃取性能的影响 10

3.2.7 色素对TBP萃取性能的影响 10

3.3 丁二酸的反萃与萃取剂回收优化 11

3.3.1 反萃油水比对TBP反萃性能的影响 11

3.3.2 反萃液中丁二酸浓度对TBP反萃性能的影响 12

3.3.3 温度对TBP反萃的影响 12

3.3.4 反萃时间对TBP反萃性能的影响 13

3.4 反萃液中丁二酸结晶母液的多级萃取与反萃 13

第四章 结论与展望 15

4.1 结论 15

4.2 展望 15

参考文献 16

致 谢 18

第一章 文献综述

1.1 丁二酸性质及制备

1.1.1 丁二酸简介

丁二酸（Succinic Acid）又名琥珀酸是一种二元羧酸，分子式为C₄H₆O₄, 分子量118.09，性状为无色三斜晶体或单斜晶体，广泛存在于人体、动物、植物和微生物中。熔点460-461K，能溶于水，微溶于乙醇、丙酮、乙醚和甘油等有机溶剂，不溶于氯仿、二氯甲烷^[1]。丁二酸是工业上一种重要的碳四化合物，它作为有机合成原料、重要的中间产物或专业化学制品。丁二酸具有优良的性质，可用于合成多种复杂有机物（如照相化学品^[2] ）的中间体和制造药物，还可用来合成可降解的生物聚合物^[3] ，如聚丁烯琥珀酸酯(PBS)和聚酰胺，在合成塑料、橡胶、医药、食品、涂料、农业、化工等工业中应用广泛^[4]，丁二酸及其衍生物每年有超过四亿美元的市场总量^[5]。

1.1.2 丁二酸的制备

丁二酸的工业制备方法很多，主要有石蜡氧化法、催化加氢法、丙烯酸羰基合成法、电解氧化法、乙炔法以及新兴的发酵法等方法。其中微生物发酵法与传统化学方法相比，发酵法生产丁二酸具有诸多优点。采用微生物发酵法生产丁二酸，利用可再生的农业资源包括二氧化碳作为原料避免了对于石油等不可再生资源的依赖，并且减少了化学合成工艺对环境的污染。丁二酸的生物合成主要是利用细菌、真菌等微生物以可再生资源，如糖类、秸秆、工业废料等作为原料，利用发酵固定CO₂再经分离提取制得^[6-7]，流程如下：

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