回收聚酯废料的几种工艺方法

甲醇醇解法的原理是利用废聚酯与甲醇反应，得到对苯二甲酸二甲酯和乙二醇。对苯二甲酸二甲酯可转化为对苯二甲酸或直接用作聚酯原料。甲醇醇解法的化学反应是对苯二甲酸二甲酯与乙二醇发生酯交换反应生成聚酯的逆反应。传统的甲醇醇解工艺尽管解聚反应比较简单，但产品的提纯却很复杂。如果用于解聚的聚酯质量低，就必须对甲醇、乙二醇和对苯二甲酸二甲酯的混合物进行分离。如果聚酯片中     

原位红外光谱研究聚对苯二甲酸乙二醇酯(PET)醇解反应过程

以醋酸锌(ZnAc2)为催化剂,甲醇(CH3OH)为醇解剂,采用在线红外光谱仪跟踪了聚对苯二甲酸乙二醇酯(PET)解聚反应过程中产物红外特征峰强度随时间的变化关系,研究了催化剂用量和反应温度对PET解聚过程的影响,并给出了可能的解聚机理。红外光谱跟踪结果表明,解聚过程中C-O,C=O基团的红外吸光强度随时间不断增强,解聚完成后吸光强度趋于定值。同时二者表现出相同的变化趋势,可以用其表征PET的解聚率。通过比较不同反应条件下的PET解聚速率发现,催化剂ZnAc2的适宜用量为PET质量的0.8%;提高反应温度可显著缩短PET解聚所需的时间,在190℃条件下,PET完全解聚仅用时15 min,具有良好的工业应用价值。PET解聚的主要产物是对苯二甲酸二甲酯(DMT)和乙二醇(EG),解聚过程中PET存在多种断链机制,产生不同的中间产物,可继续与甲醇发生酯交换反应生成DMT和EG。     

壳聚糖硫酸盐催化合成衣康酸二甲酯

以壳聚糖和硫酸为原料,制备了壳聚糖硫酸盐,利用红外及元素分析对壳聚糖硫酸盐进行了结构表征。将其用于催化衣康酸与甲醇合成衣康酸二甲酯的反应,考察了酸醇比、时间、催化剂用量、温度等条件对衣康酸二甲酯收率的影响,得到的最佳工艺条件为：壳聚糖硫酸盐用量占反应物料总质量的2%,n(甲醇)∶n(衣康酸)=7∶1,反应温度为140 ℃,反应时间6 h,在此条件下,产品收率为86.6%。衣康酸二甲酯经气质定性分析,气相色谱检测纯度大于98%。催化剂经简单干燥处理,循环使用5次后产品收率为84.0%。     

聚对苯二甲酸乙二醇酯在超临界甲醇中解聚的研究

在间歇高压反应器中研究了聚对苯二甲酸乙二醇酯(PET)在超临界甲醇中的解聚反应特性, 通过扫描电镜观测了不同解聚条件下固相聚合物的内部结构,提出了解聚反应历程并得到了不同解聚条件下反应表观活化能。在甲醇的非临界区域,PET在甲醇中表现为溶胀过程,解聚程度低,反应在聚合物表面进行,反应表观活化能为27.19kJmol-1,解聚过程为传质、扩散控制;在甲醇的临界区域, PET完全溶于甲醇,解聚反应在均相中进行,反应表观活化能为89.79kJmol-1,为化学反应控制。     

用超临界反应从废PET中回收纯单体

由新日本空气技术公司和日本国立材料与化学研究所研究成功的这种化学回收法是使经粉碎的 PET与超临界甲醇反应。反应在约 330℃温度和 8.1MPa压力下进行约 2 0 min,得到对苯二甲酸二甲酯和乙二醇 ,收率 95% ,5%的甲醇进行循环处理。甲醇醇解后 ,两单体通过结晶 ,离心分离和蒸馏处理分离 ,回收。甲醇循环重复使用。此法曾在一 5L热压器中进行试验 ,得到的单体无需提纯即可直接用于生产高纯度的 PET。该公司计划下一步将以较大的规模试验核实小规模试验的结果。据估计 ,采用此技术的工业规模装置需要达到至少 2万 t/a的处理能力在经济上…     

响应面法优化废旧PET一锅法解聚工艺的研究

以对苯二甲酸二甲酯(DMT)产率为指标,通过单因素实验和响应面法对一锅法解聚废旧PET工艺进行优化。结果表明,解聚温度、乙二醇(EG)摩尔分数和酯交换时间3个因素对DMT产率的影响显著,最佳解聚工艺条件为:以二水乙酸锌、乙酸钾和十二水磷酸三钠为解聚催化剂,Na OH为酯交换的催化剂,PET解聚温度为230℃,n(EG)∶n(PET)为5.08,解聚时间为4 h,n(甲醇)∶n(PET)为80,酯交换时间为6 h,酯交换温度为75℃,此时,DMT产率为84.39%。在优化条件下再次进行实验,得到DMT产率为83.72%,与模型预测值接近。     

聚酯废丝的化学回收研究

使用乙二醇(EG)对有色聚酯(PET)废料解聚,经分离提纯,得到对苯二甲酸二乙二醇酯(BHET)。研究了物料比、反应温度、反应时间、催化剂对醇解率的影响。结果表明,在m(乙二醇)∶m(PET)=2∶1,反应温度196℃,反应时间3 h,催化剂用量为PET质量的0.5%条件下,聚酯解聚很彻底,产物羟值可达434 mg/g以上,主要成分是BHET单体及其低聚物。并通过IR,DSC,HPLC验证了产物的组成,BHET单体纯度可达96.457%。     

杜邦把聚酯再循环工艺工业化

杜邦公司开工它的第一套工业化装置,用Petretec工艺,使聚酯(PET)再循环。此工厂位于Cape Fear,邻近威林顿。此工厂使甲醇分解作用,把废聚酯膜,纤维和其他聚酯材料转化为45000吨对苯二甲酸二甲酯(DMT)     

以单体酸为原料制备生物柴油

研究了以单体酸为原料制备生物柴油的方法,反应以对甲苯磺酸为催化剂,单体酸与甲醇进行酯化反应获得脂肪酸甲酯。分别考察了酯化反应条件如甲醇与脂肪酸的摩尔比、反应时间、催化剂浓度以及反应温度对酯化率的影响。通过正交实验得到最佳酯化反应参数：醇酸摩尔比3∶1,反应时间3 h,对甲苯磺酸用量6%,反应温度60 ℃,该条件下单体酸酯化率达98.25%。实验制得的单体酸甲酯生物柴油的主要性能指标符合ASTM质量标准,并与0^#柴油性质接近。     

废弃PET聚酯的甲醇醇解回收技术

固废资源化是可持续发展和环境友好的必然要求。废塑料俗称白色垃圾,在固废中占比很大,其回收再利用技术一直是工业中关注的焦点。聚对苯二甲酸乙二醇酯（PET）是重要的聚酯材料,广泛应用于饮料瓶、纤维、工程塑料和薄膜等领域。我国是PET生产、消费第一大国,每年废弃的PET量很大,回收再利用势在必行。典型的回收方法是通过化学回收法将PET解聚成单体或低聚物。对废弃PET聚酯的醇解工艺进行了较为系统的评述,并在技术经济性方面将其与超临界甲醇醇解法进行了比较,并初步指出了未来可能的发展方向。     

Degradation of poly(butylene terephthalate) in different supercritical alcohol solvents

Reactions were carried out in a batch autoclave reactor. Poly(butylene terephthalate) (PBT) and different alcohol solvents were used in the vessel. The reaction products were analyzed by infrared spectroscopy and gas chromatography/mass spectrometry. Alcoholysis of PBT occurred in supercritical methanol, ethanol, and propanol, and we obtained dimethyl terephthalate (DMT), diethyl terephthalate (DET), and dipropyl terephthalate (DPT), respectively. The conversion of PBT at different temperatures showed similar trends but different degradation degrees. The reactivity for the alcoholysis of PBT in supercritical methanol was much higher than those in supercritical ethanol and propanol. DMT and 1,4‐butanediol obtained from the depolymerization of PBT in supercritical methanol reached 98.5 and 72.3%, respectively, at 583 K for 75 min. The yield of DET reached 76% for 75 min. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Methanolysis of Poly（ethylene terephthalate）in Supercritical Phase

1 INTRODUCTIONPoly(ethylene terephthalate), commonly known as PET polyester, is extensively used for making synthetic fibers and package containers. The volume of PET consumed is rising by year, and thus the chemical recycling and reuse of waste PET are drawing much attention for the preservation of resources and the protection of environment. Through chemical recycling, waste PET is depolymerized into its valuable monomers such as dimethyl terephthalate (DMT), bis (hydroxyethyl) ter…     

Depolymerization of polyethyleneterephthalate in supercritical methanol

The depolymerization of polyethyleneterephthalate (PET) in supercritical methanol was carried out using a batch-type autoclave reactor. The total conversion and the yield of dimethylterephthalate (DMT) increased with rising temperature. The final yield of DMT at 300°C and 310°C reached 97.0% and 97.7%, respectively. The yield of DMT was markedly increased when the methanol density was 0.08 g/cm³, and leveled off at higher densities. A kinetic model to describe the depolymerization of PET in supercritical methanol was proposed, where the scission of one ester linkage in PET by a methanol molecule produces one carboxymethyl group and one hydroxyl group. The values of the forward reaction rate constant at different temperatures were determined by comparing the observed time dependence of carboxymethyl group concentration with that calculated by the proposed model. The activation energy was evaluated to be 49.9 kJ/mol, a value close to a literature value (55.7 kJ/mol). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2102–2108, 2001     

聚对苯二甲酸丁二醇酯在超临界甲醇中降解机理的研究

在高压间歇无搅拌反应器中研究了聚对苯二甲酸丁二醇酯(PBT)在高温甲醇溶液中的降解行为,通过对降解产物的各种定性和定量的分析,提出了超临界甲醇降解PBT的机理为在甲醇的作用下聚合物分子链的随机断裂和酯交换反应双重作用下发生的降解反应,建立了降解-反应模型.PBT在甲醇溶液中的降解可分为超临界区、非超临界区和中间过渡区三个区域.通过分子量测定考察了PBT在不同的区域中降解规律.在非临界区PBT在溶剂中处于溶胀状态,其数均分子量Mn下降缓慢,解聚程度低;在过渡区PBT的溶解性能提高,聚合物大分子发生断裂,降解速率加快;在超临界区,Mn随反应的进行而迅速下降,聚合物很快完全降解.在超临界区中PBT可实现完全降解,其主要产物为单体对苯二甲酸二甲酯(DMT)和丁二醇(BG),它们的收率可分别可达98.1%和72.3%.     

Recycling of waste PET‐bottles using dimethyl sulfoxide and hydrotalcite catalyst

The degradation of PET bottles has been successfully achieved using hydrotalcite as catalyst and dimethyl sulfoxide (DMSO) as solvent. The reaction was carried out at boiling point of DMSO (190°C) and degradation was complete in 10 min. The oligomer (tetramer) obtained was treated with NaOH at room temperature in methanol to get dimethyl terephthalate (DMT) and ethylene glycol (EG). Thus, it is a safe and cleaner process. Oligomer was characterized by MS, 13 C‐NMR, X‐ray diffractometric, and thermogravimetric analysis. DMT and EG were characterized by GC‐MS. DMT was also characterized by FT‐IR. GC‐MS analysis shows that the purity of DMT was 99%. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2012     

Depolymerization of poly(trimethylene terephthalate) in supercritical methanol

The depolymerization of poly(trimethylene terephthalate) (PTT) in supercritical methanol was carried out with a batch‐type autoclave reactor at temperatures ranging from 280 to 340°C, at pressures ranging from 2.0 to 14.0 MPa, and for reaction time of up to 60 min. PTT quantitatively decomposed into dimethyl terephthalate (DMT) and 1,3‐propaniol (PDO) under the designed conditions. The yields of DMT and PDO greatly increased as the temperature rose. The yields of the monomers markedly increased as the pressure increased to 10.0 MPa, and they leveled off at higher pressures. The final yield of DMT at 320°C and 10.0 MPa reached 98.2%, which was much closer to the extent of the complete reaction. A kinetic model was used to describe the depolymerization reaction, and it fit the experimental data well. The dependence of the forward rate constant on the reaction temperature was correlated with an Arrhenius plot, which gave an activation energy of 56.8 kJ/mol. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2363–2368, 2004     

DMT甲醇溶液结晶介稳区性质的研究

研究了对苯二甲酸二甲酯（ＤＭＴ）甲醇溶液的结晶特性。测定了ＤＭＴ在甲醇中的溶解度、ＤＭＴ甲醇溶液于不同降温速率、搅拌转速下的结晶介稳区宽度以及不同过饱和度下的结晶成核诱导期。结果表明：ＤＭＴ在甲醇溶液中的溶解度随温度升高而增加;溶液的结晶介稳区随降温速率的增加变宽,随搅拌转速的增加而变窄,且ＤＭＴ甲醇溶液的结晶诱导期随相对过饱和度的增加而缩短。     

BHET/纳米TiO2催化合成PET性能的研究

采用对苯二甲酸双羟乙酯(BHET)/纳米TiO_2复合材料为催化剂合成聚酯(PET),研究了催化剂的催化活性以及所合成PET的性能。结果表明:催化剂添加量为16.5μg/g(换算成TiO_2的有效含量)时,酯缩聚时间为80 min,所合成的PET的色度b值达到纤维级聚酯切片一级品标准;PET成型加工性能优异,PET初生纤维拉伸4.0倍时,断裂强度达3.78 cN/dtex,PET薄膜双向拉伸3.7倍时,其断裂强度为116.0 MPa,断裂伸长为122.5%。     

Correlation of acidity of metal ion with catalytic activity for the formation of poly(ethylene terephthalate)

For the transesterification of DMT (dimethyl lerephthalate) and polycondensation of BHET [bis(2-hydroxyethyl) terephthalate)], catalytic activity of various metal complex can be correlated with acidity of metal ion, which is expressed as modified electronegativily. Based on correlations mode of catalysis for the formation of PET [poly(ethylene terephthalate] was suggested.     

PET Recycling – Contributions of Crystallization to Sustainability

Polyethylene terephthalate (PET) is one of the most common thermoplastic polymers and its durability has become a major environmental concern. The current public debate on plastic debris also triggered the revision of PET recycling technologies. This Research Article focuses on the chemical recycling of PET by means of methanolysis. The process degrades PET into two main reaction products, dimethyl terephthalate (DMT) and ethylene glycol (EG). Subsequent separation by distillation combined with crystallization removes critical impurities and non-PET components from co-polymers, providing monomers of high purity needed for re-polymerization purposes.