论文总字数：23774字

摘 要

乙醇是重要的化学品原料，广泛应用于医药、塑料、涂料和化妆品等行业。乙醇与水在1.015×10⁵ Pa、78.15 ̊C下形成共沸物，带来分离问题。渗透汽化是一种新型的膜分离技术，广泛用于溶剂脱水和有机混合物的分离。本研究首先采用海藻酸钠为原料，用GA和H₂SO₄作为交联剂和催化剂，制备纯的海藻酸钠(SA)膜，通过正硅酸四乙酯(TEOS)原为水解制备SA-TEOS膜并用于渗透汽化分离乙醇水溶液。实验考察了TEOS与SA质量比对海藻酸钠(SA)膜分离性能的影响。通过SEM、EDX、FTIR、TG实验对膜的微观结构和物理化学性质进行表征。加入亲水性的TEOS后，膜的亲水性增大，溶胀程度随着TEOS与SA质量比的增加而减小。当TEOS:SA质量比为0.2 ，在50 ̊C分离乙醇质量分数为90 wt%的乙醇水溶液时，杂化膜的分离性能达到最佳：渗透通量为210 g/(m²·h)，渗透侧的水含量为99.90wt%。同时，随着进料中水含量的增加，渗透通量增加；随着实验操作温度的升高，渗透通量增大，渗透侧水含量达99wt%以上。

其次，在制膜液中添加亲水性的纳米粒子Al₂O₃，制备有机-无机杂化膜，用于渗透汽化分离乙醇水溶液。实验考察了纳米Al₂O₃掺杂量对膜形貌、物理化学性质和渗透汽化性能的影响，通过FTIR、XRD、SEM进行表征。结果表明：纳米Al₂O₃与聚合物SA和GA发生了强有力的作用；当纳米Al₂O₃含量为0.3wt%时，杂化膜显示出较好的分离性能，渗透通量由未掺杂时的173g/(m²·h)提高到197g/(m²·h)，渗透侧的水含量从99.70wt%上升到99.92wt%。当乙醇水溶液中水的含量从7wt%上升到20wt%时，渗透通量由114g/(m²·h)提高到478g/(m²·h)，渗透侧的水含量先增大后减小；当料液温度从30 ̊C上升到50 ̊C，渗透通量显著增加，从114g/(m²·h)增加到197 g/(m²·h)，渗透侧的水含量缓慢下降从99.97wt%下降到99.92wt%。

关键词：海藻酸钠(SA)；TEOS；Al₂O₃；渗透汽化

Preparation and modification of sodium alginate pervaporation membrane

Abstract

Ethanol, an important chemical product, is mainly used in pharmaceutical, plastic, coating and variety of cosmetics. It is well known that water and ethanol can form an azeotrope at 1 atm, 78.15 ̊C and this causes difficulty in its recovery through traditional methods. Pervaporation is a new type of membrane separation technology which is widely used to separate a mixture of organic solvent and dehydration. In this study, composite pervaporation membranes were prepared using sodium alginate (SA) and tetraethylorthosilicate (TEOS) which were used as cross-linking agent and catalyst, respectively. The effect of mass ratio of TEOS to SA on the separation performance was investigated. The obtained membranes were characterized by scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FTIR), thermogravimetry (TG) and differential thermal analysis (DTA). The degree of swelling decreased with increasing mass ratio of TEOS to SA. The result showed that the flux reached to 210 g/(m²·h) and the content of water in permeate was 99.90 wt% with the 10wt% feed water at 50 °C when the mass ratio of TEOS to SA was 10%.

Then, organic-inorganic hybrid membranes were prepared by adding Al₂O₃ into SA solution. The effects of nano-Al₂O₃ doping on membrane morphology, physical and chemical properties and pervaporation performance were characterized by FTIR, XRD, SEM. The results showed that: a strong reaction between nano-Al2O3 with SA and GA happened; When the nano-Al₂O₃ content was 0.3wt%, the hybrid membrane showed better separation performance. The flux increased from 173 g/(m²·h) to 197 g/(m²·h), the water content of permeate side increased from 99.70wt% to 99.92wt%. When the water content of feed rose from 7wt% to 20wt%, the permeate flux

increased from 114 g/(m²·h) to 478 g/(m²·h), the water content of the permeate side decreased. The flux increased from 114 g/(m²·h) to 197 g/(m²·h) when the temperature increased from 30 ̊C to 50 ̊C. The water content of the permeate side had a slow decline from 99.97wt% to 99.92 wt%

KEYWORDS: SA; TEOS; Al₂O₃; pervaporation

目 录

摘 要 I

Abstract II

第一章 文献综述 1

1.1 课题背景 1

1.2 渗透汽化技术 1

1.2.1 渗透汽化简介 1

1.2.2 渗透汽化分离原理 2

1.2.3 渗透汽化的影响因素 3

1.3 渗透汽化膜改性方法 3

1.3.1 共混 4

1.3.2 掺杂 4

1.4 膜材料 4

1.5 改性海藻酸钠渗透汽化膜 5

1.6 本文的研究目的与内容 6

第二章 SA-TEOS渗透汽化膜的制备及表征 8

2.1 引言 8

2.2 实验部分 8

2.2.1 实验药品和仪器 8

2.2.2 实验装置及步骤 9

2.2.3 分析方法 10

2.2.4 SA-TEOS膜的制备 12

2.2.5 SA-TEOS膜的表征 12

2.3 结果与讨论 13

2.3.1 杂化膜红外分析 13

2.3.2 杂化膜热重分析 14

2.3.3 复合膜电镜分析 15

2.3.4 SA-TEOS膜EDX图 16

2.3.5 SA-TEOS膜溶胀度表征 17

2.3.6 SA-TEOS膜中TEOS:SA质量比不同对膜分离性能的影响 19

2.3.7 料液中水含量对膜分离性能的影响 20

2.3.8 料液温度对膜分离性能的影响 21

2.3.9 杂化膜厚度对分离性能的影响 23

2.4本章小结 23

第三章 SA-Al₂O₃杂化膜的制备与表征 24

3.1 引言 24

3.2 实验部分 24

3.2.1 实验药品和仪器 24

3.2.2 SA- Al₂O₃杂化膜的制备 25

3.2.3 膜的表征 25

3.3 结果与讨论 25

3.3.1 杂化膜红外分析 25

3.3.2 杂化膜XRD分析 26

3.3.3 杂化膜电镜分析 27

3.3.4 杂化膜溶胀度表征 28

3.3.5 掺杂纳米Al₂O₃对膜分离性能的影响 29

3.3.6 料液中水含量对膜分离性能的影响 31

3.3.7 料液温度对膜分离性能的影响 32

3.4 本章小结 33

参考文献 34

致 谢 36

文献综述

1.1 课题背景

燃料乙醇一般是指体积分数达到 99.5%以上的无水乙醇，是良好的辛烷值调和组分和汽油增氧剂，燃烧乙醇汽油能够有效减少汽车尾气中的 PM2.5 和 CO^[1]，其作为可再生液体燃料的代表之一，可补充化石燃料资源，降低石油资源对外依存度，减少温室气体和污染物排放，可在坚持和发展可持续和环境友好型经济的中发挥重要作用，近年来受到世界各国的广泛关注。我国的国家标准规定,汽油醇中汽油含量为90%,燃料乙醇含量为10%。目前以甘蔗、玉米为原料的第1代燃料乙醇产业已经形成规模，燃料乙醇已经成为世界消费量最大的生物燃料^[2]。

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