废弃PET化学回收及制备不饱和聚酯树脂的研究进展

doi:10.16085/j.issn.1000-6613.2021-1439

摘要/Abstract

摘要：

随着聚对苯二甲酸乙二醇酯（PET）材料用量的大幅增长，大量废弃PET制品堆积造成的环境污染问题日益突出，其回收利用技术也随之广受关注。在不同的PET回收方法中，将PET降解为单体或低聚物的化学回收是效率最高、产物利用价值最大的方法，但也存在反应条件苛刻、产物收率低等问题。本文详细梳理了水解法、甲醇醇解法、二元醇醇解法、胺解法和氨解法等化学回收方法的主要特点以及微波加热、离子液体、纳米技术等新兴技术在PET化学回收过程中的应用概况。通过对各种化学回收工艺的比较，文中得出二元醇醇解法是最具商业应用价值方法的结论。在此基础上，文中重点介绍了PET的二元醇解以及进一步制备不饱和聚酯树脂的化学过程、发展现状、制约因素和改进措施。分析表明，由PET二元醇解产物制备不饱和聚酯树脂是提高废弃PET资源化效率、丰富原料供给、推动产品升级的重要途径，开发高效、廉价、环保的新型催化剂或酶催化技术是废弃PET回收领域今后主要的发展方向。

关键词: 聚对苯二甲酸乙二醇酯, 回收, 降解, 二元醇解, 制备, 不饱和聚酯树脂, 化学过程

Abstract:

With the substantial increase of polyethylene terephthalate (PET) material consumption, the environmental pollution caused by the accumulation of a large number of waste PET products has become increasingly prominent, and its recycling technology has also received widespread attention. Among different PET recovery methods, the chemical recycling of degrading PET into monomers or oligomers is the most efficient and most valuable method for product utilization. However, there are also problems such as harsh reaction conditions and low product yields. This review combs the main characteristics of the chemical recycling methods such as hydrolysis, methanolysis, glycolysis, aminolysis and ammonolysis. Meanwhile, the applications of emerging technologies such as microwave heating, ionic liquids and nanotechnology in the chemical recycling of PET are also introduced. Through the comparison of various chemical recycling processes, it is concluded that glycolysis is the most valuable method for commercial application. On this basis, the focus is on the chemical processes, development status, restricting factors and improvement measures of the glycolysis of PET and the further preparation of unsaturated polyester resins. The analysis shows that the preparation of unsaturated polyester resins from PET glycolysis products is an important way to improve the resource efficiency of waste PET, enrich the supply of raw materials and promote product upgrades. The development of high-efficiency, low-cost and environmentally friendly new catalysts or enzyme catalysis is the main development direction in the field of waste PET recycling in the future.

Key words: polyethylene terephthalate (PET), recovery, degradation, glycolysis, preparation, unsaturated polyester resins, chemical processes

中图分类号:

TQ322.3

李志斌, 唐辉, 罗大伟, 应俏. 废弃PET化学回收及制备不饱和聚酯树脂的研究进展[J]. 化工进展, 2022, 41(6): 3279-3292.

LI Zhibin, TANG Hui, LUO Dawei, YING Qiao. Progress in chemical recycling of waste PET and preparation of unsaturated polyester resins[J]. Chemical Industry and Engineering Progress, 2022, 41(6): 3279-3292.

图/表 12

参考文献 62

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EG/PET配比	催化剂	催化剂/PET配比	温度/℃	醇解时间/min	BHET收率/%	参考文献
7.6∶1（mol/mol）	Zn(OAc)₂	0.0026（mol/mol）	196	60	64	［56］
7.6∶1（mol/mol）	Na₂CO₃	0.0041（mol/mol）	196	60	65
4∶1（w/w）	尿素	0.1（w/w）	180	180	78	［66］
10∶1（mL/g）	ZrCl₄	0.01（w/w）	190	180	69	［61］
10∶1（mL/g）	CoCl₂·6H₂O	0.01（w/w）	190	180	65
10∶1（mL/g）	[Co(dcype)Cl₂]	0.03（mol/mol）	190	180	82
4∶1（w/w）	K₆SiW₁₁ZnO₃₉(H₂O)	0.0013（mol/mol）	185	30	84.1	［67］
4∶1（w/w）	Na₁₂[WZn₃(H₂O)₂(ZnW₉O₃₄)₂]	0.00018（mol/mol）	190	40	84.5	［62］
10∶1（w/w）	[Bmim]OH	0.05（w/w）	190	120	71.2	［63］
11∶1（w/w）	[Bmim]ZnCl₃	0.0125（w/w）	190	120	84.9	［40］
4∶1（w/w）	[Amim][ZnCl₃]	0.1（w/w）	175	75	80.1	［57］
11.7∶1（w/w）	[Bmim]₂[CoCl₄]	0.17（w/w）	175	90	81.1	［68］
6.7∶1（w/w）	[Bmim][OAc]	0.33（w/w）	190	180	58.2	［58］
6.7∶1（w/w）	[Bmim-Fe][(OAc)₃]/膨润土	0.33（w/w）	190	180	44	［69］
4∶1（w/w）	[Ch]₃[PO₄]	0.05（w/w）	180	180	60.6	［41］
10∶1（w/w）	1,3-二甲基咪唑-2-羧酸盐	0.15（w/w）	185	60	60	［42］
10∶1（w/w）	Fe₃O₄增强多壁碳纳米管	0.05（w/w）	190	120	100	［70］
10∶1（mL/g）	Fe₃O₄@SiO₂@(mim)[FeCl₄]	0.15（w/w）	180	1440	100	［9］
4∶1（w/w）	尿素/ZnCl₂DES	0.05（w/w）	170	30	82.8	［43］
4∶1（w/w）	1,3-二甲基脲/Zn(OAc)₂ DES	0.05（w/w）	190	20	82	［44］
5∶1（w/w）	乙酰胺/ZnCl₂@ZIF-8	0.004（w/w）	195	25	83.2	［65］

EG/PET配比	催化剂	催化剂/PET配比	温度/℃	醇解时间/min	BHET收率/%	参考文献
7.6∶1（mol/mol）	Zn(OAc)₂	0.0026（mol/mol）	196	60	64	［56］
7.6∶1（mol/mol）	Na₂CO₃	0.0041（mol/mol）	196	60	65
4∶1（w/w）	尿素	0.1（w/w）	180	180	78	［66］
10∶1（mL/g）	ZrCl₄	0.01（w/w）	190	180	69	［61］
10∶1（mL/g）	CoCl₂·6H₂O	0.01（w/w）	190	180	65
10∶1（mL/g）	[Co(dcype)Cl₂]	0.03（mol/mol）	190	180	82
4∶1（w/w）	K₆SiW₁₁ZnO₃₉(H₂O)	0.0013（mol/mol）	185	30	84.1	［67］
4∶1（w/w）	Na₁₂[WZn₃(H₂O)₂(ZnW₉O₃₄)₂]	0.00018（mol/mol）	190	40	84.5	［62］
10∶1（w/w）	[Bmim]OH	0.05（w/w）	190	120	71.2	［63］
11∶1（w/w）	[Bmim]ZnCl₃	0.0125（w/w）	190	120	84.9	［40］
4∶1（w/w）	[Amim][ZnCl₃]	0.1（w/w）	175	75	80.1	［57］
11.7∶1（w/w）	[Bmim]₂[CoCl₄]	0.17（w/w）	175	90	81.1	［68］
6.7∶1（w/w）	[Bmim][OAc]	0.33（w/w）	190	180	58.2	［58］
6.7∶1（w/w）	[Bmim-Fe][(OAc)₃]/膨润土	0.33（w/w）	190	180	44	［69］
4∶1（w/w）	[Ch]₃[PO₄]	0.05（w/w）	180	180	60.6	［41］
10∶1（w/w）	1,3-二甲基咪唑-2-羧酸盐	0.15（w/w）	185	60	60	［42］
10∶1（w/w）	Fe₃O₄增强多壁碳纳米管	0.05（w/w）	190	120	100	［70］
10∶1（mL/g）	Fe₃O₄@SiO₂@(mim)[FeCl₄]	0.15（w/w）	180	1440	100	［9］
4∶1（w/w）	尿素/ZnCl₂DES	0.05（w/w）	170	30	82.8	［43］
4∶1（w/w）	1,3-二甲基脲/Zn(OAc)₂ DES	0.05（w/w）	190	20	82	［44］
5∶1（w/w）	乙酰胺/ZnCl₂@ZIF-8	0.004（w/w）	195	25	83.2	［65］

回收方法	解聚试剂	操作条件	回收产物	优点	不足与改进
碱性水解	NaOH/KOH水溶液	200～250℃，带压操作^［16］	TPA、EG	水解产物TPA和EG可直接用于PET的生产；相转移催化剂的应用能使反应在100℃以下、常压的温和条件下进行	生成的TPA需额外的酸化步骤后沉淀得到，需做好废液处理；水的亲核性较弱、水解速率慢，可通过超声波辅助、微波加热技术提高反应速率
酸性水解	强酸（H₂SO₄、HNO₃）	H₂SO₄：25～100℃^［16］、 HNO₃：70～100℃^［53］，常压	TPA、EG	无需高温高压条件	普遍存在腐蚀问题，温度和酸浓度过低也会使水解速率很慢，可引入微波加热技术、开发新型催化体系解决速率和废液的问题
中性水解	水或蒸汽	200～300℃，1～4MPa	TPA、EG	无废液问题，具有生态友好型特征	高温高压的操作条件会增加生产成本，亟需开发出高效催化剂以改善操作条件，如H⁺@ZSM-5-25型分子筛
甲醇解	甲醇	180～280℃，2～4MPa	DMT、EG	对污染物的耐受性更强，可以处理低质量的原料；高温下的气相甲醇还可以作为载体将气相中的单体组分与液相中的低聚物分离	高温高压的操作条件增加了生产成本，加剧了甲醇解的强腐蚀性，发展催化甲醇解更有利于降低PET解聚温度，减少能耗；产物分离困难，预蒸馏和无溶剂熔融结晶相结合的新型分离工艺将大大降低投资和运行成本，提高甲醇解的可持续性
二元醇解	二元醇（EG、PG、DEG等）	180～240℃，常压	BHET及其低聚物、EG、PG、DEG等	反应温度适中且多在常压下进行，简单、灵活、易于工业化扩大；以少量的二元醇为解聚剂，能做到重复利用，解聚及催化剂回收过程对环境危害性小；可按需求选择不同种类的催化剂；产物用途广泛，可生产包括UPR、PU、醇酸树脂、环氧树脂在内的多种高分子材料，用于UPR、PU等的生产时可不用从混合产物中分离出二元醇	因为存在聚合可能，解聚单体不能通过真空蒸馏等常规方法提纯，可采用闪蒸柱和结晶器两级蒸发工艺进行单体提纯^［75］；不宜处理污染度过大的原料，需加强原料分拣、净化的预处理工序
胺解	甲胺、乙胺、乙醇胺、乙二胺等	20～100℃，常压	TPA的二酰胺、EG	反应条件很温和，已确定部分胺解在增强PET性能方面的应用，如纤维表面改性	在PET化学回收工业中很少应用，部分胺解产物用作增塑剂、添加剂，产品附加值较低
氨解	NH₃	70～180℃，中压、低压	对苯二甲酰胺、EG	温度、压力要求适中，产品收率较高；产物对苯二甲酰胺经加氢可制备对苯二甲酰胺，用于生产环氧树脂、聚氨酯涂料等	解聚时间较长，产品提纯步骤繁复，需简化

回收方法	解聚试剂	操作条件	回收产物	优点	不足与改进
碱性水解	NaOH/KOH水溶液	200～250℃，带压操作^［16］	TPA、EG	水解产物TPA和EG可直接用于PET的生产；相转移催化剂的应用能使反应在100℃以下、常压的温和条件下进行	生成的TPA需额外的酸化步骤后沉淀得到，需做好废液处理；水的亲核性较弱、水解速率慢，可通过超声波辅助、微波加热技术提高反应速率
酸性水解	强酸（H₂SO₄、HNO₃）	H₂SO₄：25～100℃^［16］、 HNO₃：70～100℃^［53］，常压	TPA、EG	无需高温高压条件	普遍存在腐蚀问题，温度和酸浓度过低也会使水解速率很慢，可引入微波加热技术、开发新型催化体系解决速率和废液的问题
中性水解	水或蒸汽	200～300℃，1～4MPa	TPA、EG	无废液问题，具有生态友好型特征	高温高压的操作条件会增加生产成本，亟需开发出高效催化剂以改善操作条件，如H⁺@ZSM-5-25型分子筛
甲醇解	甲醇	180～280℃，2～4MPa	DMT、EG	对污染物的耐受性更强，可以处理低质量的原料；高温下的气相甲醇还可以作为载体将气相中的单体组分与液相中的低聚物分离	高温高压的操作条件增加了生产成本，加剧了甲醇解的强腐蚀性，发展催化甲醇解更有利于降低PET解聚温度，减少能耗；产物分离困难，预蒸馏和无溶剂熔融结晶相结合的新型分离工艺将大大降低投资和运行成本，提高甲醇解的可持续性
二元醇解	二元醇（EG、PG、DEG等）	180～240℃，常压	BHET及其低聚物、EG、PG、DEG等	反应温度适中且多在常压下进行，简单、灵活、易于工业化扩大；以少量的二元醇为解聚剂，能做到重复利用，解聚及催化剂回收过程对环境危害性小；可按需求选择不同种类的催化剂；产物用途广泛，可生产包括UPR、PU、醇酸树脂、环氧树脂在内的多种高分子材料，用于UPR、PU等的生产时可不用从混合产物中分离出二元醇	因为存在聚合可能，解聚单体不能通过真空蒸馏等常规方法提纯，可采用闪蒸柱和结晶器两级蒸发工艺进行单体提纯^［75］；不宜处理污染度过大的原料，需加强原料分拣、净化的预处理工序
胺解	甲胺、乙胺、乙醇胺、乙二胺等	20～100℃，常压	TPA的二酰胺、EG	反应条件很温和，已确定部分胺解在增强PET性能方面的应用，如纤维表面改性	在PET化学回收工业中很少应用，部分胺解产物用作增塑剂、添加剂，产品附加值较低
氨解	NH₃	70～180℃，中压、低压	对苯二甲酰胺、EG	温度、压力要求适中，产品收率较高；产物对苯二甲酰胺经加氢可制备对苯二甲酰胺，用于生产环氧树脂、聚氨酯涂料等	解聚时间较长，产品提纯步骤繁复，需简化

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