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     

Depolymerization of poly(butylene terephthalate) using high‐temperature and high‐pressure methanol

Poly(butylene terephthalate) (PBT) was depolymerized in excess methanol at high‐temperature (473–523 K) and high‐pressure (4–14 MPa) conditions. Considering the critical point of methanol (512.6 K, 8.09 MPa), the reaction pressure was varied over the range of 6–14 MPa at the reaction temperature of 513 K. As a result, ca. 20 min was required to recover dimethyl terephthalate and 1,4‐butanediol, quantitatively, at any pressure, indicating that the supercritical state of methanol is not a key factor of degradation of PBT and that the effect of pressure is little. On the contrary, when the reaction temperature was varied over the range of 473–523 K at the pressure 12 MPa, the decomposition rate constant of PBT at the reaction temperatures (503–523 K) higher than the melting temperature of PBT (500 K) was much higher than that at 473–483 K. This result indicates that melting of PBT is an important factor for the short‐time depolymerization of PBT. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3228–3233, 2000     

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%.     

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。     

超临界甲醇中的化学反应

在介绍超临界甲醇特性的基础上,综述了近年来超临界甲醇中的有机化学反应、高分子降解回收和生物质再资源化等方面的研究现状与进展,分析了目前超临界甲醇研究中存在的主要问题,并对研究的主要方向进行了展望.     

聚苯乙烯在超临界二甲苯中的解聚

研究了聚苯乙烯在超临界二甲苯介质中的解聚反应，温度为340－390℃，压力为5MPa，10MPa。产的相GC－MS分析表明解聚产物多达107种，含量最多的是苯乙烯的二聚物，丙基苯和对甲基苯乙烯二聚物。在实验取值范围内，主要产物苯乙烯二聚物及解聚转化率随温度升高而增加。在一级反应的基础上，由数据拟合求出了反应活化能，频率因子及反应速率常数的表达式，能较好地预测实验结果。     

Depolymerization of poly(ethylene terephthalate) wastes using ethanol and ethanol/water in supercritical conditions

Chemical recycling of poly(ethylene terephthalate) (PET) in supercritical ethanol has been investigated. In the presence of water, under supercritical conditions (temperature and pressure above 516 K and 6,384 kPa, respectively) excess ethanol reacts with PET to form diethyl terephthalate (DET) as the main product. A laboratory‐made 0.1 L ‐batch reactor was used at 528 K under pressures from 7,600 and 11,600 kPa. After the required reaction times, the reaction products were analyzed by reverse phase high pressure liquid chromatography and nuclear magnetic resonance. It was found that PET is completely depolymerized into monomers in about 5 h. The influences of water, pressure, ethanol/PET weight ratio, PET sources, as well as depolymerization time were investigated. Maximum DET recovery yield was 98.5%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2009–2016, 2006     

超临界甲醇制备生物柴油的多元相平衡研究进展

超临界甲醇制备生物柴油与传统方法制备生物柴油相比具有着多方面的优点,包括无需催化剂、反应速率快、对原料要求低、产物不需要后处理,因而近年来越来越受到国际社会的关注。由于与酯转化相关的反应物、中间产物以及产物在甲醇中的高压相平衡是理解与调控超临界甲醇反应的基础,为更好的理解多元混合物高温高压相行为对于酯转化反应的控制条件和机理,需要对相关体系的高压相平衡、转酯化反应动力学以及二者之间的关系等基础性问题进行深入研究。但由于超临界流体对温度、压力变化的敏感性和高温高压取样的困难性,使得在相平衡方面的研究起步较晚,基础数据缺乏。本文比较了当前几种生物柴油生产方式的优缺点,同时对现有超临界甲醇制备生物柴油的多元相平衡研究进展情况进行了总结。     

超临界条件下甲醇合成的气液传质系数测定

以液体石蜡为惰性液相载体,正己烷为超临界介质,合成气制甲醇为研究体系,测定了超临界条件下三相浆态床中甲醇合成的气液传质系数。在反应温度238℃、合成气分压3.7 MPa、气体空速2744 h^-1条件下,通过不断增加催化剂浓度提高气液传质阻力和反应阻力的相对大小,采用外推法获得完全处于气液传质控制下的气液传质系数。计算结果表明：催化剂浓度对CO的气液传质系数的影响较大,而对CO₂的气液传质系数的影响较小;液相条件下CO、CO₂的气液传质系数分别是0.161、0.03 s^-1,而超临界三相甲醇合成中CO、CO₂的气液传质系数分别是0.199、0.042 s^-1,说明三相浆态床甲醇合成中引入超临界流体利于气液传质,验证了超临界介质中三相甲醇合成的优越性。     

胜利褐煤超临界醇解反应行为研究

对胜利褐煤在甲醇、碱体系中的超临界反应行为进行了研究,考察了反应温度、反应时间和碱的种类分别对胜利褐煤转化率、产物收率和分布规律的影响.结果表明,反应温度显著影响褐煤的转化率和产物收率,产物主要为四氢呋喃可溶组分(占67%～85%)和甲苯可溶组分(占8%～22%);300℃时,胜利褐煤在甲醇-NaOH体系中转化率和收率最高(99%左右);反应时间显著影响褐煤的转化率和产物收率,80 min后褐煤的转化率和产物收率分别为99%和100%;反应过程中四氢呋喃可溶组分可转化为甲苯可溶组分、正己烷可溶组分和水溶性组分;碱的种类对褐煤超临界醇解转化率和产物收率有显著影响.     

超/亚临界水中聚对苯二甲酸乙二醇酯的解聚

采用间歇式高压反应装置研究了聚对苯二甲酸乙二醇酯(PET)在超/亚临界水中的解聚,考察了投料比、反应温度及反应时间对PET解聚率及主产物对苯二甲酸(TPA)和乙二醇(EG)产率的影响.固相产物采用傅里叶红外光谱(FT-IR)、液相色谱(HPLC)进行分析,液相产物采用气相色谱(GC)和气-质联谱(GC-MS)进行分析....     

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…     

番泻叶药渣超临界甲醇解产物的 GC／MS 分析

采用GC/MS分析解聚产物,研究了番泻叶药渣在超临界甲醇条件下的解聚产物。结果表明：番泻叶药渣超临界甲醇解聚产物所含成分复杂。 GC/MS分析鉴定出了58种化合物,化合物类型主要有酯类、酮类、醇类、烯烃类、酚类、含氮类及其它类化合物,其中大部分是甲酯类化合物,共27种,相对百分含量为59.43％;第二大类的是酮类化合物,相对含量为15.07％,首次鉴定出羽扇烯酮,相对含量达11.31％。甲醇参与了番泻叶药渣甲醇超临界解聚反应,同时存在酯化反应和超临界萃取作用,番泻叶药渣的超临界解聚反应的机理有待更深入的研究。该研究结果为番泻叶药渣的进一步利用提供了科学依据。     

Electroanalytical studies on electrically conducting polyaniline:polyethyleneterephthalate composite films

Polyaniline (PANI):polyethyleneterephthalate (PET) composite was prepared by chemical polymerization of aniline diffused in the PET matrix. Thus prepared composite films were characterized by fourier‐transform infrared spectroscopy and scanning electron microscopy and their electrical properties and the thermo‐oxidative stability was studied by thermogravimetry and differential thermal analysis. The stability in terms of DC electrical conductivity retention was studied in an oxidative environment by two slightly different techniques viz. isothermal and cyclic techniques. DC electrical conductivity of composite films was found to be stable up to 90°C for most of the composites under ambient conditions. The composite films were employed as cathode material in secondary cells containing 1M ZnCl₂ solution. The studies were carried out on the charge/discharge cycles under a constant current load 140 mA. The composite films showed similar behavior in electrolyte solution and cell response is reversible. To determine the diffusion coefficient for the chloride ions diffusion into the composite films electrochemically, galvanostatic pulse method was used. The diffusion coefficient was estimated to be ～ 3.28 × 10^?12 cm² s^?1. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Ionic liquids in supercritical methanol greatly enhance transesterification reaction for high‐yield biodiesel production

Biodiesel production is one of the most promising future alternatives to replacing fossil fuels. This work studies the use of ionic liquids (ILs) as potential catalysts in supercritical methanol for biodiesel production from non‐edible oil. The transesterification reaction of karanja oil was investigated in supercritical methanol in the presence of two respective ILs, [BMIM⁺][ ] and [Chol⁺][H₂ ]. The reaction was performed in a one‐step batch process at several temperatures and percentages by weight of catalyst (w/w_oil). The results obtained show that the IL [Chol⁺][H₂ ] allows a high yield of fatty acid methyl esters to be achieved in a short reaction time (above 95% in 45 min). A catalytic mechanism is also proposed for the IL that offered significant catalytic activity. This work investigates the effects of the use of ionic liquids as potential catalysts in supercritical methanol for the transesterification reaction of non‐edible oil. The reported reaction times to obtain biodiesel yields above 90% through the transesterification reaction of karanja oil range between 90 min and 8 h. ILs as catalysts in supercritical methanol drastically reduce reaction time (45 min) to obtain high fatty acid methyl ester yield (95.6%). © 2016 American Institute of Chemical Engineers AIChE J, 62: 3842–3846, 2016     

Continuous synthesis of metal nanoparticles in supercritical methanol

Metal nanoparticles were synthesized continuously in supercritical methanol (scMeOH) without using reducing agents at a pressure of 30 MPa and at various reaction temperatures ranging 150-400 °C. Wide angle X-ray diffraction (WAXD) analysis revealed that metallic nickel (Ni) nanoparticles were synthesized at a reaction temperature of 400 °C while mixtures of nickel hydroxide (α-Ni(OH)₂) and metallic Ni were produced at lower reaction temperatures of 250-350 °C. In contrast, metallic silver (Ag) nanoparticles were produced at reaction temperatures above 150 °C while metallic cupper (Cu) nanoparticles were produced at reaction temperatures above 300 °C. Mixtures of copper oxide (CuO and Cu₂O) and metallic Cu were produced at lower reaction temperatures of 250 °C. Scanning electron microscopy (SEM) showed that the particles size and morphology changed drastically as the reaction temperature increased. The average diameters of Ni, Cu and Ag particles synthesized at 400 °C were 119 ± 19 nm, 240 ± 44 nm, and 148 ± 32 nm, respectively. The scMeOH acted both as a reaction medium and a reducing agent. A possible reduction mechanism in scMeOH is also presented.     

Methanolysis of seed oils in flowing supercritical carbon dioxide

The direct methanolysis of triglycerides in flowing supercritical carbon dioxide by an immobilized lipase is described. The reaction system consists of two syringe pumps for substrate addition and another two syringe pumps for delivering CO₂ at 24.1 MPa. Corn oil is pumped into the carbon dioxide stream at a rate of 4 μL/min, and methanol is pumped at 5 μL/min to yield fatty acid methyl esters (FAME) at >98% conversion. Direct methanolysis of soy flakes gives FAME at similar yields. This combined extraction/reaction is performed at 17.2 MPa and 50°C. The fatty acid profiles obtained for these seed oils matches those obtained by classical chemical synthesis.     

超临界甲醇降解聚碳酸酯的动力学

利用高压间歇反应器研究了聚碳酸酯（PC）在230～265 ℃、7.76～9.96 MPa条件下的降解特性.通过红外光谱(IR)、体积排阻色谱(SEC)和气相色谱/质谱(GC/MS)对降解产物进行了定性和定量分析,提出了PC在超临界甲醇中的降解机理,同时运用连续分布动力学对PC降解历程进行了研究,随机断裂降解反应的活化能为75.72 kJ•mol^-1.     

连续化条件下超临界甲醇法制备生物柴油

在连续操作的管式反应器中,以大豆油为原料在压力11～19MPa,温度240～400℃的超临界甲醇条件下进行连续化制备生物柴油的研究。考察了在连续反应条件下醇油摩尔比、压力、温度、停留时间及共溶剂对大豆油转化率的影响。实验结果表明:较高的醇油摩尔比有利于油脂转化率的提高,但当醇油摩尔比超过40:1后提高醇油摩尔比对提高油脂转化率的影响不大;在11～15MPa范围内,压力升高对油脂转化率影响很大,但高于15MPa后压力对转化率的影响减弱;反应温度对油脂转化率有着重要影响,在300℃以上随着温度的升高,油脂转化率有较大幅度的上升,但温度太高油脂会发生分解反应;醇油摩尔比40:1,温度350℃,压力15MPa,停留时间1000s是该实验获得的最佳反应条件,在该条件下油脂转化率可达89%。实验还研究了添加共溶剂四氢呋喃对油脂转化率的影响。