废聚对苯二甲酸乙二醇酯的高温醇解研究

通过高温高压醇解法对废聚对苯二甲酸乙二醇酯(PET)在催化剂金属醋酸盐作用下,进行乙二醇醇解得到对苯二甲酸乙二醇酯(BHET),研究了废PET高温醇解的影响因素及工艺条件。结果表明:在高温醇解反应中,乙二醇与废PET的质量比和反应压力为主要影响因素,反应温度和解聚时间为次要影响因素;BHET收率随反应时间的延长、温度与压力的升高、乙二醇与废PET的质量比加大、催化剂的用量增大而增加,而二甘醇含量(除质量比因素)及醇解产物的熔点则随其相应降低;最佳醇解反应条件为压力0.4 MPa、乙二醇与废PET质量比0.5∶1.0、反应温度250℃、反应时间4 h,BHET收率达82%。     

乙二醇解聚废旧聚酯及其产物分析

研究了乙二醇解聚废旧聚酯工艺,探索并明确了催化剂含量、废旧聚酯与乙二醇质量比、温度、时间等参数对非均相解聚效率的影响。试验结果表明:催化剂质量分数0.2%、废旧聚酯与乙二醇质量比1∶3、常压反应温度196℃、反应时间2 h为优化高效的醇解工艺,醇解率为100%,对苯二甲酸双羟乙酯(BHET)产率达到80%。研究了醇解主要产物中BHET与低聚物的分离纯化工艺,通过DSC/TGA、FTIR、NMR等测试手段对分离组分进行了分析表征。     

PET在离子液体[Pmim]OH催化下的液化行为研究

采用1-戊基-3-甲基咪唑氢氧化物([Pmim]OH)离子液体作为催化剂,在乙二醇(EG)体系中降解聚对苯二甲酸乙二醇酯(PET),分别考察了反应时间、反应温度、催化剂用量、EG与PET的质量比(mEG∶mPET)对降解实验的影响。结果表明,最佳降解条件为:反应温度为195℃,反应时间为3.5h,催化剂用量为PET质量的2.5%,mEG∶mPET为4∶1;离子液体对PET的降解表现出较好的催化作用,降解产物为对苯二甲酸二乙二醇酯(BHET)。     

微波辅助废旧PET聚酯解聚反应研究

采用微波辅助加热的方式研究了回收PET聚酯的乙二醇解聚反应,并对比了相同催化作用下常规加热条件下的解聚反应,对解聚反应产物BHET进行了熔点测定和IFTIR分析.结果显示,两种方法下控制解聚反应至PET聚酯完全转化时单体BHET的收率相差不大,微波辅助条件下单体的收率略高,但是反应时间大大缩短.反应物PET与EG在1:...     

响应面法优化Fe_3O_4/NiO催化聚对苯二甲酸乙二醇酯醇解

以Fe_3O_4为磁性基质,采用液相共沉淀法制备磁性固体碱催化剂Fe_3O_4/Ni O,并用于聚对苯二甲酸乙二醇酯(PET)的醇解反应。以催化醇解反应得到的对苯二甲酸二乙二醇酯(BHET)回收率为指标,通过响应面法优化得到催化剂合成的最佳条件,即前驱体n(Fe_3O_4)∶n[Ni(AC)_2]=1∶3.94,反应时间1.67 h,催化剂煅烧时间2.01 h,煅烧温度600℃。以最优条件制备的催化剂在乙二醇介质,反应温度195℃,降解反应时间4 h,催化剂用量为PET质量的2.0%的条件下进行醇解反应,BHET回收率达到81.47%。采用XRD、BET和SEM对催化剂进行表征,结果表明:催化剂具有片状结构,比表面积较大,降解产物是BHET。     

高黏度聚酯的醇解工艺及其溶胀预处理研究

以乙二醇(EG)为解聚剂分别醇解特性黏数为0.670,1.014 dL/g的聚对苯二甲酸乙二醇酯(PET)切片及两者的混合物,对醇解产物进行了表征;通过单因素控制法考察了反应温度、EG与PET摩尔比、反应时间、催化剂添加量对醇解产物产率的影响;针对高黏度PET切片难以醇解的问题,提出了一种溶胀预处理工艺,研究了溶胀预处理PET切片的醇解动力学。结果表明：不同黏度PET切片的醇解产物的化学结构基本一致,主产物均为对苯二甲酸双羟乙酯(BHET);高黏度PET切片醇解体系的反应温度高于低黏度PET切片,高黏度PET切片适宜的醇解工艺为EG与PET摩尔比14：1、催化剂添加质量分数0.5%、反应时间240 min、反应温度200℃,此条件下产物BHET的产率为48.65%;高黏度PET切片在130℃经溶胀预处理后,结晶度由30.95%降至25.25%,反应速率常数由0.131 9 min^-1提高至0.171 9 min^-1,醇解速率大幅提高,溶胀预处理适宜的温度为高于PET切片的玻璃化转变温度且比其结晶温度低20～30℃。     

中科院过程工程研究所开发出多金属氧簇催化降解PET新方法

<正>中国科学院过程工程研究所开发出一种高活性催化醇解聚对苯二甲酸乙二醇酯(PET)制备对苯二甲酸乙二醇酯(BHET)的新方法。其特征在于以过渡金属Mn、Co、Zn、Cu或Ni单取代的Keggin型杂多酸盐为催化剂,以乙二醇为溶剂,在催化剂用量为反应物质量的0.5%~10%,反应温度为70~250℃,压力0.1 MPa,反应时间10 min~2 h的条件下醇解聚对苯二甲酸乙二醇酯。该方法具有反应条件温和、催化剂易制备、催     

过渡金属Mn取代多金属氧簇催化醇解废旧PET

合成了一种具有三明治结构的过渡金属Mn取代的多金属氧簇(POMs)催化剂Na12[WZnMn2(H2O)2(ZnW9O34)2],用于催化聚对苯二甲酸乙二醇酯(PET)的醇解过程,对反应温度、反应时间和催化剂量等实验条件进行了优化。结果表明,在催化剂量为PET质量的1.0%、质量比PET/EG(乙二醇)为1:4及190℃的条件下反应80 min,PET降解率可达100%,对苯二甲酸乙二醇酯(BHET)的收率达84.42%。     

聚对苯二甲酸乙二醇酯合成基本原理Ⅱ.聚对苯二甲酸乙二醇酯的合成

概述了聚对苯二甲酸乙二醇酯(PET)合成的基本原理，以及由对苯二甲酸乙二醇酯(BHET)单体经缩聚反应合成PET的反应机理、合成过程中的主要化学反应，详述了BHET缩聚合成PET的主要影响因素。由BHET缩聚合成PET属于逐步缩合聚合过程，缩聚过程中存在多个化学反应，包括链增长反应、链降解反应及网状结构凝胶物生成的副反应。BHET缩聚合成PET的影响因素主要有催化剂种类及其用量、稳定剂种类及其用量、反应温度、反应釜余压及物料的液层厚度等。今后，在PET及其共聚酯的合成中，应加大无毒催化剂的使用与推广、非石油基原料的开发及化学改性共聚酯的开发，以及废旧聚酯的化学法回收再生利用。     

乙二醇/二甘醇联合醇解废聚酯及其产物分析

探索了乙二醇/二甘醇联合醇解废聚酯(PET)工艺,并对醇解产物的性能进行了表征.结果表明:废PET与总二元醇质量比1 ∶ 2～1∶ 3、二甘醇(DEG)物质的量分数10％(占PET结构单元)、反应温度200℃、催化剂质量分数0.1％、反应时间1～1.5 h为高效的醇解反应条件.通过DSC、TG、FTIR、1H NMR等...     

Kinetics of glycolysis of poly(ethylene terephthalate) under microwave irradiation

The glycolysis of poly(ethylene terephthalate) (PET) was carried out using excess ethylene glycol (EG) in the presence of zinc acetate as catalysts under microwave irradiation. The effects of particle size, microwave power, the weight ratio of EG to PET, the weight ratio of catalyst to PET, reaction temperature and stirring speed on the yield of bis(hydroxyethyl terephthalate)(BHET) were investigated. The experimental results indicated that the glycolysis rate was significantly influenced by stirring speed and initial particle size. The optimal parameters of glycolysis reactions were the weight ratio of catalyst to PET of 1%, the weight ratio of EG to PET of 5, 500 W and 196°C, the yield of BHET reached to 78% at only 35 min. The glycolysis products were analyzed and identified by FTIR, differential scanning calorimetry, and elemental analysis. The kinetics of glycolysis of PET under microwave irradiation could be interpreted by the shrinking core model of the film diffusion control. The apparent activation energy was evaluated using the Arrhenius equation and it was found to be 36.5 KJ/mol, which was lower compared to the same process using conventional heating. The experimental results also showed that the reaction time was significantly decreased under microwave irradiation as compared with it by conventional heating. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Pretreatment of low-grade poly(ethylene terephthalate) waste for effective depolymerization to monomers

Pretreatment process of silica-coated PET fabrics, a major low-grade PET waste, was developed using the reaction with NaOH solution. By destroying the structure of silica coating layer, impurities such as silica and pigment dyes could be removed. The removal of impurity was confirmed by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The pretreated PET fabric samples were used for depolymerization into its monomer, bis(2-hydroxylethyl) terephthalate (BHET), by glycolysis with ethylene glycol (EG), and zinc acetate (ZnAc) catalyst. The quality of BHET was confirmed by DSC, TGA, HPLC and NMR analyses. The highest BHET yield of 89.23% was obtained from pretreated PET fabrics, while glycolysis with raw PET fabric yielded 85.43%. The BHET yield from untreated silica-coated PET fabrics was 60.39%. The pretreatment process enhances the monomer yield by the removal of impurity and also improves the quality of the monomer.     

Depolymerization of poly(ethylene terephthalate) resin under pressure

The process of depolymerization of PET resin by EG glycolysis under pressure is investigated. The kinetics of this pressurized depolymerization of PET resin is discussed. It was found that the rate of depolymerization is dependent of temperature, pressure, and concentration ratio of EG to PET. The rate of depolymerization is proportional to the square of EG concentration and faster than that under atmospheric pressure. Glycolyzed products under pressure consist of the PET monomer, BHET, and oligomers, mostly dimer and trimer. An equilibrium between BHET and oligomers is attained quickly soon after the depolymerization step is completed in the case of a higher ratio of EG/PET used. In the case of lower ratio of EG/PET, the final product now consists of higher molecular weight of oligomers rather than monomer, dimer, and trimer.     

Microwave assisted glycolysis of poly(ethylene terephthalate) catalyzed by 1‐butyl‐3‐methylimidazolium bromide ionic liquid

The combination of ionic liquid (IL) associated with microwave energy may have some potential application in the chemical recycling of poly (ethylene terephthalate). In this processes, glycolysis of waste poly (ethylene terephthalate) recovered from bottled water containers were thermally depolymerized with solvent ethylene glycol (EG) in the presence of 1‐butyl‐3‐methyl imidazolium bromide ([bmim]Br) as catalyst (IL) under microwave condition. It was found that the glycolysis products consist of bis (2‐hydroxyethyl) terephthalate (BHET) monomer that separated from the catalyst IL in pure crystalline form. The conversion of PET reach up to 100% and the yield of BHET reached 64% (wt %). The optimum performance was achieved by the use of 1‐butyl‐3‐methyl imidazolium bromide as a catalyst, microwave irradiations temperature (170–175°C) and reaction time 1.75–2 h. The main glycolysis products were analyzed by ¹H NMR, ¹³C NMR, LC‐MS, FTIR, DSC, and TGA. When compared to conventional heating methods, microwave irradiation during glycolysis of PET resulted in short reaction time and more control over the temperature. This has allowed substantial saving in energy and processing cost. In addition, a more efficient, environmental‐friendly, and economically feasible chemical recycling of waste PET was achieved in a significantly reduced reaction time. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41666.     

Calcined Zn/Al hydrotalcites as solid base catalysts for glycolysis of poly(ethylene terephthalate)

In this research, glycolysis of poly(ethylene terephthalate) (PET) with ethylene glycol (EG) was carried out using Zn/Al mixed oxide catalyst. These mixed oxides were prepared by calcining crystalline Zn/Al hydrotalcites at different calcination temperatures. The samples and corresponding precursors were characterized by X‐ray diffraction, BET, Fourier‐transform infrared spectra, thermogravimetry/differential thermal analysis, and Hammett titration method. The experimental results showed that Zn/Al mixed oxides obtained from hydrotalcites were found to be more active than their individual oxides for glycolysis of PET. The relationship between catalytic performance and chemical–physical features of catalysts was established. In addition, a study for optimizing the glycolysis reaction conditions, such as the weight ratio of EG to PET, catalyst amount and reaction time, was performed. The conversion of PET and yield of bis(2‐hydroxyethyl terephthalate) (BHET) reached about 92% and 79%, respectively, under the optimal experimental conditions. Moreover, it should be noted that Zn/Al mixed oxide not only provided an effective heterogeneous catalyst for glycolysis of poly(ethylene terephthalate), but also presented a novel method for decolorization of discarded colored polyester fabric. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41053.     

Studies of glycolysis of poly(ethylene terephthalate) recycled from postconsumer soft‐drink bottles. I. Influences of glycolysis conditions

The glycolysis of recycled poly(ethylene terephthalate) flakes by ethylene glycol (EG) is investigated. Bis‐2‐hydroxyethyl terephthalate (BHET) and oligomers are predominately glycolysis products. The influences of glycolysis temperature, glycolysis time, and the amount of catalyst (cobalt acetate) are illustrated. The BHET, dimer, and oligomers are predominately glycolysis products. The optimum glycolysis temperature is found to be 190°C. If a 190°C glycolysis temperature, 1.5‐h glycolysis time, and 0.002 mol glycolysis catalyst (cobalt acetate) are used, the glycolysis conversion is almost 100%. The glycolysis conversion rate increases significantly with the glycolysis temperature, glycolysis time, and the amount of cobalt acetate. Thermal analyses of glycolysis products are examined by differential scanning calorimetry. In addition, the chemical structures of glycolysis products are also determined by a Fourier transform IR spectrophotometer. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 943–948, 2001     

Glycolysis of postconsumer polyethylene terephthalate waste

Glycolytic depolymerization of polyethylene terephthalate (PET) bottle waste was attempted using ethylene glycol (EG) in the presence of chlorides of zinc, lithium, didymium, magnesium, and iron as catalysts. Virtual monomer bis (2‐hydroxyethyl terephthalate) (BHET) was obtained in all cases with nearly 74% yield, the highest yield being achieved with zinc chloride catalyst 0.5% w/w, PET : EG ratio 1 : 14 and 8 h under reflux conditions. The results were comparable to other catalysts like common alkalis, acids, and salts of some earth metals and zeolites used earlier although parameters of glycolysis were observed to vary depending on the catalyst. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Recycling of off‐grade pet via partial alcoholysis to synthesize functionalized pet oligomer nanocomposites

Off‐grade poly(ethylene terephthalate) (PET) of industrial manufacturers was partially depolymerized using excess ethylene glycol in the presence of manganese acetate as a transesterification catalyst to synthesize PET oligomers. Influences of reaction time, Ethylene Glycol (EG)/PET molar ratio, catalyst concentrations, and particle size of off‐grade PET on yield of partial glycolysis reaction were investigated based on Box–Behnken's design of experiment. Thermal analyses of glycolyzed products are examined by differential scanning calorimetry. The optimum samples were also well‐characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy (¹H‐NMR and ¹³C‐NMR). The optimal conditions to synthesize PET oligomer (melting point of about 180°C) for a 120‐min glycolysis reaction time were EG/PET molar ratio of 2 with no catalyst using granule‐shaped PET. The same results were obtained for a 60‐min glycolysis reaction time, including EG/PET molar ratio of 1 with the weight ratio (catalyst to PET) of 0.5% using average particle size of PET. Then, maleated PET as a compatibilizer for preparing PET nanocomposites was produced via reaction between maleic anhydride/phthalic anhydride composition and optimized PET oligomers based on central composite design of experiment. The combination of reaction time of 106 min and PhA/MA molar ratio of 0.85 gave the best results based on d‐spacing and peak shift of nanocomposite samples. Hence, melt mixing of maleated PET with organoclay produced a good intercalation of layered silicate and good dispersion of clay in maleated PET matrix. Analysis of variance (ANOVA) was studied for both glycolyzed products and functionalized PET oligomers. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

An efficient recycling process of glycolysis of PET in the presence of a sustainable nanocatalyst

We demonstrate that the catalyst Perkalite F100 efficiently works as a nanocatalyst in the depolymerization of poly(ethylene terephthalate) (PET). After depolymerization of PET in the presence of ethylene glycol and the Perkalite nanocatalyst, the main product obtained was bis(2‐hydroxylethyl) terephthalate (BHET) with high purity, as confirmed by Fourier transform infrared spectroscopy and NMR. The BHET monomers could serve directly as starting materials in a further polymerization into PET with a virgin quality and contribute to a solution for the disposal of PET polymers. Compared with the direct glycolysis of PET, the addition of a predegradation step was shown to reduce the reaction time needed to reach the depolymerization equilibrium. The addition of the predegradation step also allowed lower reaction temperatures. Therefore, the strategy to include a predegradation step before depolymerization is suitable for increasing the efficiency of the glycolysis reaction of PET into BHET monomers. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46285.     

Study of glycolysis of poly(ethylene terephthalate) recycled from postconsumer soft‐drink bottles. III. Further investigation

A modified glycolysis reaction of recycled poly(ethylene terephthalate) (PET) bottles by ethylene glycol (EG) was investigated. Influences of the glycolysis temperature, the glycolysis time, and the amount of catalysts (per kg of recycled PET) were illustrated in this study. The manganese acetate was used as a glycolysis catalyst in this study. Bis‐2‐hydroxyethyl terephthalate (BHET) and its dimer were predominately glycolysis products. It was found the optimum glycolysis temperature is 190°C. And the best glycolysis condition is 190°C of glycolysis temperature, 1.5 h of glycolysis time, and 0.025 moles of manganese acetate based on per kg of recycled PET. If the best glycolysis condition is conducted, the glycolysis conversion may be as high as 100%. For a given reaction time (1.0 h), the ln(% glycolysis conversion) is linear to 1/T (K^?1) and the activation energy (E) of glycolysis reaction is around 92.175 kJ/(g mole). The glycolysis conversion rate increases significantly with increasing the glycolysis temperature, the glycolysis time, or the amount of manganese acetate (glycolysis catalyst). Thermal analyses of glycolysis products were examined by a differential scanning calorimetry (DSC) and a thermogravimetric analysis (TGA). According to the definition of a 2³ factorial experimental design, the sequence of the main effects on the glycolysis conversion of the recycled PET, in ascending order, is the glycolysis time (0.18) < the amount of catalyst per kg of the recycled PET (0.34) < the glycolysis temperature (0.40). Meanwhile, the prediction equation of glycolysis conversion from the result of a 2³ factorial experimental design is ? = 0.259+0.20X₁+0.09X₂+0.17X₃+0.06X₁ X₂+0.145X₁X₃+0.05X₂X₃+0.035X₁X₂X₃. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2004–2010, 2003