涤纶乙二醇解产物在甲醇酯交换过程的转化规律

doi:10.13475/j.fzxb.20241201301

纺织学报 ›› 2025, Vol. 46 ›› Issue (06): 1-7.doi: 10.13475/j.fzxb.20241201301

• 纤维新材料与纺织绿色发展青年科学家沙龙专栏 • 下一篇

涤纶乙二醇解产物在甲醇酯交换过程的转化规律

徐文豪¹, 陈琳², 徐世美², 汪秀丽², 王玉忠²()

1.四川大学化学工程学院, 四川成都 610046
2.四川大学化学学院, 四川成都 610046

收稿日期:2024-12-06 修回日期:2025-03-12 出版日期:2025-06-15 发布日期:2025-07-02
通讯作者: 王玉忠(1961—),男,教授,博士。主要研究方向为高分子材料的阻燃与高性能化、生物基与生物降解高分子及高分子材料的循环与升级回收。E-mail: yzwang@scu.edu.cn。
作者简介:徐文豪(1997—),男,博士生。主要研究方向为废旧涤纶纺织品的醇解与单体全回收。
基金资助:
国家重点研发计划项目(2023YFC3904901)

Transformation rule of polyester glycolysis products in methanol transesterification

XU Wenhao¹, CHEN Lin², XU Shimei², WANG Xiuli², WANG Yuzhong²()

1. School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610046, China
2. College of Chemistry, Sichuan University, Chengdu, Sichuan 610046, China

Received:2024-12-06 Revised:2025-03-12 Published:2025-06-15 Online:2025-07-02

摘要/Abstract

摘要： 为高效回收利用废旧纺织品中的涤纶,针对工业上采用的乙二醇解-甲醇酯交换联合工艺,揭示了涤纶在该联合工艺中的化学回收反应历程,确定了涤纶乙二醇解产物中对苯二甲酸双羟乙酯(BHET)及低聚物向对苯二甲酸二甲酯(DMT)转化的规律。结果表明:在第1步乙二醇解过程中,涤纶醇解产物主要为BHET的单体、二聚体、三聚体、四聚体和五聚体;在第2步甲醇酯交换过程中,BHET的单体、二聚体和三聚体在65 ℃下反应3 h可完全转化为DMT;而四聚体和五聚体由于分子量大导致反应活性较低,难以完全转化为DMT;由于DMT是该联合工艺中涤纶的最终回收单体,在乙二醇解过程中,涤纶解聚为BHET的单体、二聚体和三聚体是“有效”解聚,因此可通过提高乙二醇比例和延长解聚时间来提高BHET单体及二聚体和三聚体的含量,以提高最终DMT的产量和回收率,助力实现涤纶的高效化学回收和循环再利用。

关键词: 废旧纺织品, 循环再利用, 涤纶, 乙二醇解, 甲醇酯交换, 低聚物, 转化规律

Abstract:

Objective Polyester is the most widely used fiber material in waste textiles, and its efficient recycling is the key to solving the problem of waste textiles. At present, the combined glycolysis-methanol transesterification process is widely used in industry. In this process, the methanol transesterification reaction of glycolysis products into dimethyl terephthalate (DMT)is the key step. Therefore, the transformation rule of glycolysis products in methanol transesterification can provide theoretical guidance for the efficient chemical recycling of waste polyester.

Method In this paper, the chemical recycling of polyester was studied according to the industrial combined glycolysis-methanol transesterification process. The depolymerization products of polyester textile during glycolysis and methanol transesterification were qualitatively and quantitatively studied by high performance liquid chromatography-mass spectrometry (HPLC-MS).

Results In the first step of glycolysis, the glycolysis products of polyester are mainly bis(2-hydroxyethyl) terephthalate (BHET) monomer, dimer, trimer, tetramer, and pentamer. The oligomer content can be controlled by reducing the ethylene glycol ratio and shortening the depolymerization time. Firstly, the glycolysis solution with a mass ratio of polyethylene terephthalate (PET) to ethylene glycol (EG) of 1∶1 and depolymerized at 190 ℃ for 1 h was selected for methanol transesterification. HPLC-MS showed that BHET monomer, dimer, and trimer could be completely converted into DMT within 3 h, while tetramer and pentamer could not be completely converted into DMT due to their large molecular weight and low reaction activity. The intermediate 2-hydroxyethyl methyl terephthalate is generated during the conversion of BHET and oligomers to DMT. The conversion rate of BHET and oligomers to DMT was very fast (within 5 min), and then remain at a very low content. The BHET in the PET glycolysis products was separated by water washing, and the conversion process of BHET oligomers to DMT was studied in detail. HPLC-MS confirmed that the separated oligomer products were mainly BHET dimer, tetramer, pentamer and trace trimer. The separated BHET oligomers were subjected to methanol transesterification reaction. It was found that the BHET dimer and trimer completely disappeared after methanol transesterification, which again showed that dimer and trimer were completely converted into DMT. However, BHET tetramer and pentamer still exist, proving that it was difficult to completely convert them into DMT. This is because BHET tetramer and pentamer have larger molecular weights and lower reactivity. They have fewer effective collisions with methanol in the transesterification reaction and cannot be completely converted into DMT. Since DMT is the final recycled monomer of polyester in this combined process, the depolymerization of polyester into BHET monomer, dimer, and trimer during glycolysis is the ″effective″ depolymerization.

Conclusion Aiming at the glycolysis-methanol transesterification combined process used in industry, the methanol transesterification process of the glycolysis depolymerization products of polyester was researched and revealed. In the first step of glycolysis, the glycolysis products of polyester are mainly BHET monomer, dimer, trimer, tetramer, and pentamer. In the second step of methanol transesterification, BHET monomer, dimer, and trimer can be completely converted into DMT at 65 ℃ for 3 h. However, BHET tetramers and pentamers exhibit low reactivity due to their large molecular weight and are difficult to be completely converted into DMT. The depolymerization of polyester into BHET monomer, dimer, and trimer during glycolysis represents the ″effective″ depolymerization. Therefore, the content of BHET monomer and its dimer and trimer can be increased by increasing the proportion of ethylene glycol and prolonging the depolymerization time, thereby improving the final DMT yield and achieving efficient chemical recycling of polyester fibers. The transformation rules of BHET and its oligomers to DMT in the glycolysis products of polyester were determined, which provides theoretical guidance for the chemical recycling of polyester textiles in glycolysis-methanol transesterification combined process.

Key words: waste textile, recycling, polyester, glycolysis, methanol transesterification, oligomer, transformation rule

中图分类号:

TS102.9

徐文豪, 陈琳, 徐世美, 汪秀丽, 王玉忠. 涤纶乙二醇解产物在甲醇酯交换过程的转化规律[J]. 纺织学报, 2025, 46(06): 1-7.

XU Wenhao, CHEN Lin, XU Shimei, WANG Xiuli, WANG Yuzhong. Transformation rule of polyester glycolysis products in methanol transesterification[J]. Journal of Textile Research, 2025, 46(06): 1-7.

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链接本文: http://www.fzxb.org.cn/CN/10.13475/j.fzxb.20241201301

http://www.fzxb.org.cn/CN/Y2025/V46/I06/1

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反应时间/ min	相对含量/%
反应时间/ min	BHET	二聚体	三聚体	四聚体	五聚体	DMT	MHET
0	70.68	17.16	8.06	1.82	0.90	0	0
1	2.85	0	3.21	0.39	0.70	68.19	13.36
5	0.12	0	0	0.19	0.26	84.98	14.45
10	0.29	0	0	0.18	0.55	84.00	11.60
30	0.10	0	0	0.17	0.65	80.40	18.40
60	0.41	0	0	0.10	0.24	82.84	12.78
90	0.09	0	0	0.14	0.30	90.67	8.80

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涤纶乙二醇解产物在甲醇酯交换过程的转化规律

Transformation rule of polyester glycolysis products in methanol transesterification

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