熔融酯交换合成聚碳酸酯预聚体

以碳酸二苯酯和双酚A为原料,氢氧化四丁基铵为催化剂,熔融酯交换合成聚碳酸酯预聚体,研究了催化剂用量、抗氧剂种类、原料配比等对产物色差的影响。在优化条件下,当碳酸二苯酯与双酚A的摩尔比为1.05∶1.00,抗氧剂为K7时,预聚体的色差最小,为0.11。     

有机胺催化酯交换合成聚碳酸酯树脂工艺

研究了以碳酸二苯酯(DPC)和双酚A(BPA)为原料,氢氧化四乙基铵(TEAH)为催化剂,熔融酯交换合成聚碳酸酯的工艺。其催化剂用量、原料配比、反应时间等工艺条件对产物分子量等参数有较大的影响。与以氢氧化钠作催化剂相比,在所得的较优条件下以TEAH为催化剂,可得到分子量较高、分子量分散指数低、熔体流动性好、支化重排产物少、基本无色的聚碳酸酯树脂。     

酯交换缩聚法合成聚碳酸酯的研究进展

聚碳酸酯的酯交换缩聚工艺具有绿色环保的特性,符合当今世界可持续发展的主题,相对于传统的光气法工艺更具有发展前途。综述了国内外在酯交换缩聚工艺的机理以及催化剂选择和工艺条件上取得的进展。指出碳酸二苯酯与双酚A酯交换反应是四面体机理,正反应是二级反应,逆反应是三级反应;以La(ACAC)_3作催化剂,得到的产品不但粘均分子量较高,而且热稳定性非常好;利用酯交换熔融聚合工艺可以解决传统光气法的环境问题,而固相聚合可以得到超高分子量的产品。     

酯交换法合成碳酸二苯酯催化剂的研究

碳酸二苯酯是重要的有机中间体,应用于塑料工业。酯交换法合成碳酸二苯酯是替代光气法的新型绿色合成工艺。笔者概述了碳酸二苯酯酯交换法的合成工艺,并对催化剂研究作了介绍。     

A modeling of semibatch reactors for melt transesterification of dimethyl terephthalate with ethylene glycol

A mathematical model of a semi batch reactor was developed to investigate the oligomerization reactions in the melt transesterification of dimethyl terephthalate with ethylene glycol catalyzed by metal acetate catalyst. The detailed kinetic scheme based on the molecular species model is used to estimate the conversion of methyl ester groups and the concentrations of various oligomeric species. The numerical simulation of the model shows that the oligomerization reactions lower the overall conversion of methyl ester end groups. Effects of ethylene glycol/dimethyl terephthalate mole ratios, reaction temperature and, catalyst concentration on the conversion, oligomer concentration, oligomer molecular weight, and molecular weight distribution were also analyzed.     

Kinetics measurement of ethylene-carbonate synthesis via a fast transesterification by microreactors

High-purity ethylene carbonate (EC) is widely used as battery electrolyte, polycarbonate monomer, organic intermediate, and so on. An economical and sustainable route to synthesize high-purity ethylene carbonate (EC) via the transesterification of dimethyl carbonate (DMC) with ethylene glycol (EG) is provided in this work. However, this reaction is so fast that the reaction kinetics, which is essential for the industrial design, is hard to get by the traditional measuring method. In this work, an easy-to-assemble microreactor was used to precisely determine the reaction kinetics for the fast transesterification of DMC with EG using sodium methoxide as catalyst. The effects of flow rate, microreactor diameter, catalyst concentration, reaction temperature, and reactant molar ratio were investigated. An activity-based pseudo-homogeneous kinetic model, which considered the non-ideal properties of reaction system, was established to describe the transesterification of DMC with EG. Detailed kinetics data were collected in the first 5 min. Using these data, the parameters of the kinetic model were correlated with the maximum average error of 11.19%. Using this kinetic model, the kinetic data at different catalyst concentrations and reactant molar ratios were predicted with the maximum average error of 13.68%, suggesting its satisfactory prediction performance.     

酯交换合成碳酸二苯酯反应及催化剂研究进展

介绍了碳酸二甲酯与苯酚酯交换合成碳酸二苯酯的反应热力学。总结了近年来该类催化剂研究的新进展。对酯交换反应的平衡限制问题和选择性问题进行了详细的讨论。根据对反应热力学的分析,指出避开平衡限制的合理途径是采用酯交换-歧化二步法工艺路线,而高选择性地得到碳酸二苯酯取决于催化剂的性质。通过分析酸碱催化作用在酯交换反应中的差异,认为碱催化是副产物苯甲醚生成的主要原因,Lewis酸性的催化剂有利于碳酸二苯酯的高选择性。最后对国内研究现状进行了评价和展望。     

Synthesis and properties of bisphenol-Z polycarbonate via melt transesterification

Polycarbonate (PC) is a thermoplastic engineering plastic with excellent properties, and its excellent dielectric properties have broad application prospects in the field of electronics. In this paper, bisphenol Z (BPZ) and diphenyl carbonate (DPC) are used as raw materials to synthesize special polycarbonate (BPZ-PC) by melt transesterification. The effects of catalyst type, catalyst dosage, molar ratio of raw materials, transesterification reaction time and vacuum degree, polycondensation reaction temperature and time on the molecular weight of the product are investigated, and the optimal reaction conditions are obtained. The chemical structure of the product is verified by FTIR, ¹H-NMR and ¹³C-NMR spectra tests. The thermal properties, mechanical properties, optical properties and dielectric properties of BPZ-PC are evaluated. Therefore, due to its excellent performance, BPZ-PC, a high-performance low-dielectric polycarbonate, can be widely used in high-frequency communication, microelectronics, and aerospace industries.     

酯化-酯交换两步法制备生物柴油的动力学

以潲水油（WCO）为原料,探讨了酯化-酯交换两步法制备生物柴油的反应动力学。以活性炭负载硫酸铁［Fe₂(SO₄)₃/AC］为负载型催化剂,通过测定不同反应温度、不同甲醇/脂肪酸（FFA）摩尔比条件下WCO中游离脂肪酸的转化率,以此确定酯化反应的动力学控制步骤及动力学方程中的待定参数,从而建立了在实验温度范围内酯化反应的动力学方程,并根据碱催化酯交换反应机理,在简化的动力学模型基础上,推导出了WCO中甘油三酯（TG）与甲醇发生酯交换反应的宏观动力学方程。结果表明,酯化反应和酯交换反应的动力学方程在实验条件范围内都能较好地描述各自的反应过程。     

PEN合成中NDC与EG酯交换反应工艺及动力学研究

以2,6-萘二甲酸二甲醇酯(NDC)和乙二醇(EG)为原料,以金属盐类为催化剂,在一定条件下,研究了NDC与EG的酯交换反应,探讨了NDC与EG的酯交换反应工艺及动力学规律,不同反应温度下,NDC与EG酯交换反应遵循二级反应动力学规律,反应表观活化能为92.89 kJ/mol。     

固相缩聚法合成双酚A型聚碳酸酯的催化剂筛选

采用固相缩聚(SSP)法,以双酚A(BPA)和碳酸二苯酯(DPC)为原料,在不同催化剂的作用下,反应得到双酚A型聚碳酸酯(BAPC)。测定了产物的特性黏数和色差,并对产物进行了傅立叶变换红外光谱(FTIR)、核磁共振氢谱(1H–NMR)和热重(TG)分析。结果表明,四苯硼钠(Na TPB)为较优的催化剂,在1 mol的BPA中加入催化剂Na TPB用量为1×10–4 mol时,通过非光气熔融酯交换法合成并经部分结晶处理、筛分得到180~250μm预聚物颗粒,其在210℃、近真空(压力100 Pa)条件下,采用SSP法,反应3 h,可得色差较小(0.52%)、特性黏数为90.36 m L/g、热稳定性良好的BAPC。     

Homopolymerization of 4‐propionoxybenzoic acid: A kinetic study

A kinetic study of the synthesis of poly(4‐oxybenzoate) by melt‐step growth polymerization using para‐propionoxybenzoic acid is reported. The polycondensations obey second‐order kinetics, irrespective of whether the reaction was catalyzed or uncatalyzed. Breaks are observed in the kinetic plots, suggesting the presence of different kinetic regimes during the course of the reaction. An elaborate kinetic model that presupposes precipitation of oligomers predicts two‐stage kinetics as well as breaks in the rate plots and fits experimental data well throughout the course of the reaction and the performance of two transesterification catalysts are estimated. No isokinetic temperature is displayed for the transesterification reaction. Activation energy values for catalyzed reactions are found to be higher than the uncatalyzed reaction, indicating that entropy factors drive the reaction to completion. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 467–476, 1999     

Transesterification in poly(ethylene terephthalate) and poly(ethylene naphthalate 2,6-dicarboxylate) blends: model compounds study

Kinetics of transesterification reaction in poly(ethylene terephthalate)-poly(ethylene naphthalate 2,6-dicarboxylate), PET-PEN, blends resulting from melt processing was simulated using model compounds of ethylene dibenzoate (BEB) and ethylene dinaphthoate (NEN). The exchange reaction between BEB and NEN was followed by ¹H NMR spectroscopy using signals from the aliphatic protons of ethylene glycol moieties at 4.66 and 4.78 ppm, respectively. The first-order kinetics was established under pseudo-first-order conditions for both reactants. Thus, the overall transesterification reaction was second order reversible. The reversibility was confirmed experimentally by heating a mixed sequence of 1-benzoate 2-naphthoate ethylene (BEN) under similar conditions. Both forward reaction of the equimolar amounts of the reagents and reverse reaction came to equilibrium at the same molar ratio of the reactants and reaction products of roughly 0.25:0.50:0.25 for BEB, BEN, and NEN, respectively. The rate equation for the transesterification reaction in the model system was modified using half-concentration of BEN, which is the only effective in the intermolecular exchange. Direct ester-ester exchange was deduced as a prevailing mechanism for the transesterification reaction under the conditions studied, and the values of equilibrium and rate constants, as well as other basic thermodynamic and kinetic parameters were determined. The use of Zn(OAc)₂ as a catalyst resulted in a significant decrease in the activation enthalpy of transesterification, which might be due to the partial switch of the reaction mechanism from primarily pseudo-homolytic to more heterolytic where Zn^II acts as a Lewis base which binds to the ester carbonyl oxygen.     

棕榈油酯交换制备生物柴油的反应动力学

在甲醇与棕榈油的摩尔比为6∶1和催化剂KOH用量为棕榈油质量1.0%的条件下,研究不同温度下棕榈油制备生物柴油的酯交换反应动力学,采用Origin软件拟合曲线方程,建立棕榈油酯交换反应的宏观动力学模型。研究结果表明:棕榈油制备生物柴油的酯交换反应遵循1.40级动力学方程,反应速率随温度的升高而加快,二者符合Arrhenius方程,该反应的活化能为27.23 kJ/mol,频率因子为1.4×103。文中研究建立的反应动力学模型将对扩大试验研究提供理论依据和基础数据支持。     

Steady-state and transient behavior of a continuous polyethylene terephthalate condensation polymerization process. I. Melt transesterification stage

The steady-state and transient behavior of a continuous stirred-tank reactor for melt transesterification of dimethyl terephthalate with ethylene glycol in the presence of metal acetate catalyst is presented. The kinetic model includes the main transesterification reactions and side reactions leading to diethylene glycol and carboxylic acid end groups. The effect of various reactro operating parameters such as [EG]/[DMT] mole ratio and feed catalyst concentration on the product distribution under steady-state reactor operating conditions is analyzed. The dynamic process model has also been solved and the reactor transients to step changes in various reactor parameters are reported.     

Kinetic and catalytic aspects in melt transesterification of dimethyl terephthalate with ethylene glycol

The kinetics of melt transesterification of dimethyl terephthalate with ethylene glycol in the presence of zinc acetate as catalyst has been studied in semibatch conditions. We observed that this reaction occurs with the formation of many oligomers characterized from the terminal groups of the chains that can be hydroxyl–hydroxyl, methyl–hydroxyl or methyl–methyl. Experimental runs have been performed at different temperatures, initial reagents ratios, and catalyst concentrations, following the amount of methanol released during the time as well as the concentration of any kind of oligomer. All the oligomers have been identified and determined by HPLC analysis. A classic Kinetic model based on a complex reaction scheme containing four or five reaction sequences has been developed. The scheme with four sequences foresees 24 oligomeric species involved in 58 different reactions, while the scheme with five sequences has 48 oligomeric species involved in 228 reactions. Despite the large number of oligomers and occurring reactions, only two kinetic parameters and two equilibrium constants are necessary to simulate the kinetic behaviour of all the oligomers. A kinetic constant is related to the reaction of a methyl group with a hydroxyl of ethylene glycol, while the other corresponds to the reaction of a methyl group with a hydroxyl in a chain. Both kinetic constants show an activation energy of about 15 kcal/mol. We observed a nonlinear correlation between activity and catalyst concentration and interpreted this fact by assuming two different catalytic activity levels for a dissociated and an undissociated zinc ionic couple, respectively. © 1994 John Wiley & Sons, Inc.     

酯交换法合成聚碳酸酯催化剂性能考察

以双酚A和碳酸二苯酯为原料,采用非光气熔融酯交换法合成聚碳酸酯。考察了氢氧化钾、氢氧化钠、四丁基氢氧化铵、碳酸钠、吡啶以及复合催化剂对聚碳酸酯合成反应速率及聚碳酸酯分子量和色差的影响。研究表明,氢氧化钾作为催化剂较适合于聚碳酸酯合成工艺,使用复合催化剂可以得到分子量较高、色差较低的聚碳酸酯。     

碳酸二苯酯的合成工艺进展

讨论了光气法、酯交换法及氧化羰化法合成碳酸二苯酯的工艺路线及相关催化剂。重点讨论酯交换法催化剂的选择及反应装置的设计开发,对氧化羰化法则侧重于催化剂的研究开发。     

碳酸二丙酯的绿色合成及其与DMC相平衡数据测定

用碳酸二甲酯(DMC)与正丙醇(n-PrOH)酯交换反应合成了碳酸二丙酯(DPC),考察了催化剂种类、物料摩尔比、催化剂用量、温度和时间等因素对反应的影响。结果表明,碳酸钾(K2CO3)具有较好的催化活性和选择性,反应最佳工艺条件为:常压,反应温度95℃,n(n-PrOH)∶n(DMC)=3∶1,w(K2CO3)=1%,反应时间5 h,DMC转化率95.9%,DPC产率73.7%。优化条件下的重复实验表明,该反应易于控制,重复性好。测定了常压下DPC和DMC的气液相平衡数据,结果表明,在常压下DPC和DMC二元物系不形成共沸物。     

Optimization and kinetic modeling of waste lard methanolysis in a continuous reciprocating plate reactor

Continuous biodiesel production from a waste pig-roasting lard, methanol and KOH was carried out in a reciprocating plate reactor (RPR) using a factorial design containing three process factors, namely methanol/lard molar ratio, catalyst loading, and normalized height of the reactor. The main goals were to optimize the influential process factors with respect to biodiesel purity using the response surface methodology and to model the kinetics of the transesterification reaction in order to describe the change of triacylglycerols (TAG) and fatty acid methyl esters (FAME) concentrations along the RPR height. The first-order rate law was proved for both the reaction and the mass transfer. The model of the changing reaction mechanism and mass transfer of TAG was also applicable. Both kinetic models agreed with the experimental concentrations of TAG and FAME determined along the RPR height.