论文总字数：23500字

摘 要

渗透汽化是一种比较新颖的膜分离技术，相对传统的分离技术而言，更加节能环保、效率高。而且此项技术可以解决较难的分离问题，越来越受到人们的关注，尤其是在分离共沸物体系方面。渗透汽化膜是渗透汽化的核心部分，在很大程度上决定着渗透汽化分离性能的高低。

壳聚糖（CS）分子中含有许多的氨基、羟基等功能基团，这些基团和水分子之间有一定作用力，从而引起较大的亲水性。因此对于酯化反应中副反应产生的水，我们可以用CS膜进行渗透汽化反应来去除，从而使反应正向移动，提高反应转化率。但是当混合物中水的质量分数为20 %以上时，CS膜分离选择性会明显下降。这是因为CS是一种半刚性分子，分子链间的自由体积大，当水含量高时，膜的溶胀度较大，膜的稳定性降低。为此本实验将探究CS渗透汽化膜的改性方法来提高膜的分离性能。

丙酸乙酯是一种比较重要的香料添加剂、溶剂和医药中间体。生产丙酸乙酯的常用方法是丙酸与乙醇之间的酯化，但该方法是典型的可逆反应，其转化率受到热力学平衡的限制，工业上常采用增大酸或醇的浓度或者移除反应产物来提高转化率。本实验采用渗透汽化耦合酯化反应法，通过除去副产物水，使反应平衡向正方向移动，提高酯化反应的转化率。将制得的改性CS渗透汽化膜渗透汽化分离乙醇/水溶液体系并考察其分离性能，研究分离过程中各因素对改性膜分离性能的影响。然后把改性膜用在渗透汽化耦合丙酸乙酯的酯化反应当中，探究不同的影响因素对酯化反应转化率和渗透通量的影响。本文首先对渗透汽化的主要相关知识进行了介绍，并介绍了CS渗透汽化膜的应用现状和改性方法，在实验部分将改性CS膜先用于渗透汽化，然后将其用在渗透汽化耦合酯化反应当中，具体内容如下：

将国药集团化学试剂有限公司生产的脱乙酰度为80.0 %～95.0 %的壳聚糖材料配制为CS制膜液用钢丝网（300目的不锈钢丝网）过滤后与戊二醛交联，用高精度平板刮膜机刮出0.5 mm的纯CS渗透汽化膜。将制备好的改性CS膜用于渗透汽化分离乙醇/水溶液体系，通过改变反应中料液的温度和浓度，分析这两个因素对渗透汽化分离性能的影响。再将制备的改性膜用于渗透汽化耦合丙酸乙酯的酯化反应，改变反应过程中的反应温度，用气相色谱来分析这个因素对酯化转化率的影响。从实验结果可以看出：当反应温度升高、料液水含量增大时，渗透通量随之增大。当温度为60 ℃，原料侧含水10 wt%时，渗透通量达到223.3 g·m^-2·h^-1，渗透侧含水量达到89.7 wt%，这说明纯CS渗透汽化膜的分离性能比较好。渗透汽化耦合酯化实验结果表明，反应10 h后，转化率达到91.01 %，而在无渗透汽化的酯化反应中，反应10 h后转化率只有61.03 %，这验证了渗透汽化可以有效地促进反应的进行。本实验还探究了反应温度对酯化反应的转化率和渗透通量的影响，得出耦合反应的反应温度为90 ℃时，两者较好。

关键词：纯CS渗透汽化膜 渗透汽化 分离性能 丙酸和乙醇 转化率

Modified CS pervaporation membrane in the esterification reaction of propanoic acid and ethanol

ABSTRACT

Pervaporation is a relatively new membrane separation technology, compared to the traditional separation technology, it is more energy saving, high efficiency. And this technology can solve the more difficult separation problems, catches more and more people's attention, especially in the azeotropic separation system.The pervaporation membrane is the core of pervaporation process ,it largely determines the pervaporation separation efficiency level.

CS molecule contains many amino, hydroxyl functional groups, there is a certain force between these groups and water molecules, causing a large hydrophilic. So for the water side reactions in esterification reaction, we can use the CS membrane to remove it by pervaporation, causing the reaction to move forward and improve the conversion rate. But when the mass fraction of water in the mixture is more than 20 %, CS membrane separation selectivity will be significantly decreased. This is because the CS is a semi-rigid molecule, large free volume between the molecular chains, when the water content is high, the greater the degree of swelling of the membrane, reducing the stability of the membrane. So the experiment will explore methods to modify CS pervaporation membrane to improve the properties of the membrane.

Ethyl propionate is very important in spice additives, solvents and pharmaceutical intermediates. Common methods for producing ethyl propionate is propionic acid and the ethanol esterified between, but the process is a typical reversible reaction, the conversion rate is limited by thermodynamic equilibrium. Increasing the concentration of the acid or alcohol or removing the product is often used to improve the conversion rate in the industry. In this study, pervaporation is coupled with esterification, by removing the water by-product, the reaction equilibrium can be shifted to the positive direction, improve the conversion rate of the esterification reaction. The modified CS pervaporation membrane is used in the pervaporation of ethanol / water separation system and evaluate its performance, quest the influence of various factors on the separation performance of modified membrane. Then take modified membrane into permeation vaporization coupled esterification of propionate and investigate the influence of each factor during the reaction on the conversion rate of esterification and its reactive flux. This article introduced mainly related knowledge of pervaporation firstly and presented the application status and modification methods of CS modified membrane. The experimental part is to use the CS modified membrane for pervaporation coupling again for esterification, details are as followed:

Using the 80.0 % to 95.0 % degree of deacetylation chitosan material produced in Sinopharm Chemical Reagent Co., Ltd. to formulate the CS liquid filmand then filtered by steel mesh and cross-linked with glutaraldehyde, scraping 0.5 mm pure CS pervaporation membrane by a high-precision flat film machine scrapings. Take the modified membrane into pervaporation of ethanol / water system, changing the temperature or concentration of feed during the reaction and investigating these two factors on the pervaporation performance by gas chromatography. Then used the prepared modified membrane in the permeation vaporization esterification coupled propionate, change the temperature of the reaction and study the effect of this factor on the esterification conversion by gas chromatography. Results of pervaporation show that the flux increases with the increase of temperature and feed liquid water content. When the temperature is 60 ℃, the water of raw side is 30 wt%, the flux is nearly 223.3 g·m^-2·h^-1, the water content in permeate side arrives at 89.7 wt%. This showed pure CS pervaporation membrane has good separation performance. The esterification coupled pervaporation results show that, 10 h after the reaction, the conversion rate arrived to 91.01 %, while the conversion rate only arrived to 61.03 % without pervaporation. It verifies that pervaporation can promote the reaction process effectively. The experiment also studied the influence of the reaction temperature on esterification conversion rate and permeate flux, obtained when the temperature is 90 ℃,they were well.

Key Words: pure CS pervaporation membrane; pervaporation; separation performance; propanoic acid and ethanol; percent conversion

目 录

摘 要 I

ABSTRACT III

第一章 引言 1

1.1 膜分离 1

1.1.1 膜分离技术 1

1.1.2 分离膜的种类 1

1.2 渗透汽化 1

1.2.1 渗透汽化简介 1

1.2.2 渗透汽化的基本原理与传质机理 2

1.2.3 影响渗透汽化的因素 2

1.2.4 渗透汽化膜的特点与应用 3

1.3 壳聚糖膜的研究状况 4

1.3.1 壳聚糖简介 4

1.3.2 壳聚糖渗透汽化膜的改性 4

1.3.3 壳聚糖膜在渗透汽化领域的应用 5

1.4 课题的提出及内容 6

1.4.1 研究目的和意义 6

1.4.2 研究内容概述 7

第二章 实验部分 8

2.1 实验材料 8

2.1.1 实验试剂 8

2.1.2 实验仪器 8

2.2 实验装置及步骤 8

2.2.1 实验装置 8

2.2.2 改性膜的制备 9

2.2.3 实验步骤 9

2.3 分析方法 10

2.3.1 渗透汽化实验 10

2.3.2 渗透汽化耦合酯化反应实验 11

第三章 结果与讨论 13

3.1 纯CS渗透汽化膜热重分析 13

3.2 纯CS渗透汽化膜电镜分析 13

3.3 料液水含量及温度对膜分离性能的影响 14

3.3.1料液中水含量对膜的分离性能的影响 14

3.3.2 料液温度对膜分离性能的影响 14

3.4 反应温度对酯化反应的影响 15

结语 17

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