Transesterification of dimethyl terephthalate with ethylene glycol

Conclusion For the first time, data are given on the quantitative composition of the transesterification products of dimethyl terephthalate with ethylene glycol at various molar ratios of the starting materials.During the transesterification process, oligomerization reactions take place rather intensively. Thereupon the linear oligomers are formed both in the transesterification process of carbomethoxy groups and also as a result of the interaction of carbohydroxyethoxy groups. The ethylene glycol formed in the latter case ensures further transesterification of the carbomethoxy groups.It is possible in principle to reduce the molar ratio of ethylene glycol to dimethyl terephthalate in the transesterification stage. Thereupon a polyethylene terephthalate can be obtained which has properties similar to the serially produced product.Translated from Khimicheskie Volokna, No. 5, pp. 18–20, September–October, 1983.     

Studies in transesterification of ethylene carbonate to dimethyl carbonate over Amberlyst A‐21 catalyst

Transesterification of ethylene carbonate (EC) with methanol (MeOH) was studied in a slurry reactor using various homogeneous and heterogeneous, acidic as well as basic, catalysts. Among all catalysts studied, the weakly basic anion‐exchange resin Amberlyst A‐21 gave more than 95% selectivity towards dimethyl carbonate (based on EC converted). Using this Amberlyst A‐21 as a catalyst, the kinetics for the transesterification reaction was studied in the range of temperature from 363 to 393 K, varying catalyst loading from 11.24 to 44.97 kg m^?3 and the molar ratio MeOH:EC being varied between 4:1 and 16:1. The initial rate data were analysed using a power law model to aid process design. Copyright © 2005 Society of Chemical Industry     

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.     

Transesterification of brazilian vegetable oils with methanol over ion-exchange resins

The transesterification of several Brazilian vegetable oils with methanol was carried out at 60°C in the presence of several ion-exchange resins having different structures. The vegetable oils used were from Babassu coconut, corn, palm, palm kernel, and soybean. The effect of the methanol/oil mole ratio and the influences of the structure of the ion-exchange resin and the type of vegetable oil used on the catalytic activity of the ionexchange resins were investigated. The resins used were Amberlyst 15, Amberlyst 31, Amberlyst 35, and Amberlyst 36. Amberlyst 15 produced the best results for the transesterification of vegetable oils. The methyl ester yield is higher for palm kernel oil and Babassu coconut oil than for soybean oil, probably owing to their higher content of shorter-chain FA. Therefore, it was shown that the catalytic activity of the resin depends on the FA composition of the vegetable oil employed.     

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.     

PEN合成的酯交换反应工艺及动力学研究

讨论了使用 (CH3COO) 2 Zn·2H2 O作为催化剂 ,2 ,6 萘二甲酸二甲酯 (DMN) 乙二醇 (EG)的酯交换反应。该酯交换反应遵循二级反应动力学。反应活化能为 14 7.9kJ mol。较高的反应活化能使得该酯交换反应速率对反应温度比较敏感。     

Water‐vapor‐permeable polyurethane resin

The reaction of methylene diphenylene diisocyanate with ethylene glycol, dimethyl dimethoxysilane, dimethyl diethyloxysilene, and other additives in the presence of N,N‐dimethylformamide and toluene to form the structure of water‐vapor‐permeable polyurethane (PU) resin was proven with Fourier transform infrared spectra. Experimental results clearly showed that the amount of oxygen that permeated the film made with the PU resin increased with an increase in the concentration of ethylene glycol, diethylene glycol, or triethylene glycol. This was due to an increased number of hydrophilic groups attached to the backbone of the PU resin molecules. These hydrophilic groups, because of the intermolecular interactions between PU resin molecules, made PU resin molecules form an expanded conformation with large porosities. Interestingly, the water vapor permeability of the PU resin appeared to increase with an increasing concentration of ethylene glycol, dimethyl dimethoxysilane, or dimethyl diethoxysilane but not to increase with an increasing concentration of diethylene glycol, triethylene glycol, or poly(ethylene glycol) with dimethyl dimethoxysilane. The former was due to intermolecular interactions resulting in an expanded conformation with large porosities, but the latter was due to intramolecular interactions resulting in a compact conformation or a micellelike structure with small porosities. Therefore, the water vapor permeability of the former increased, but the latter remained unchanged or decreased. Our experimental results suggest that the use of poly(ethylene glycol) 400, ethylene glycol, dimethyl dimethoxysilane, and other strong hydrophilic compound in the preparation of modified PU resins substantially raises the amount of water vapor diffusing into films made with these resins. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2002–2010, 2002     

PET synthesis in the presence of lanthanide catalysts

Syntheses of poly(ethylene terephthalate), PET, by transesterification of dimethyl terephthalate with ethylene glycol in the presence of well-known catalysts and various lanthanide compounds were performed. Lanthanide catalysts appeared to be much more efficient in the first stage of the process (transesterification in the presence of an excess of ethylene glycol), and less active in polycondensation. PET produced with lanthanides was found to possess enhanced thermal and hydrolytic stability as compared to PET synthesized with well-known catalysts and commercial PET. © 1995 John Wiley & Sons, Inc.     

间苯二甲酸双羟乙酯-5-磺酸钠的合成研究

采用间苯二甲酸二甲酯-5-磺酸钠(SIPM)和乙二醇(EG)为原料,在一定的温度和催化剂条件下进行酯交换反应制备间苯二甲酸双羟乙酯-5-磺酸钠(SIPE)。用高效液相色谱(HPLC)法测定酯交换率,系统研究了催化剂、EG／SIPM摩尔比及反应时间对酯交换率的影响。     

Study of the glycolysis of PET by oligoesters

A series of oligoesters was synthesized via the transesterification of dimethyl isophthalate with neopentyl glycol or tetraethylene glycol and the esterification of adipic acid with neopentyl glycol or tetraethylene glycol under diol/diester or diol/diacid molar ratios sufficient to limit molecular weight increasing.These oligoesters were used to depolymerize poly(ethylene terephthalate) (PET) in the presence of zinc acetate to yield new types of glycolysates. The oligoesters and the glycolysates are characterized by ¹H NMR, size exclusion chromatography (SEC), differential scanning calorimetry (DSC), thermogravimetric analyses and matrix assisted laser desorption/ionisation time of flight mass spectrometry (MALDI-TOF MS). These analyses revealed the structure of the different glycolysates.     

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。     

Concurrent Synthesis of Dimethyl Carbonate and Ethylene Glycol via Transesterification of Ethylene Carbonate and Methanol Using Smectite Catalysts Containing Mg and/or Ni

Smectites containing magnesium and/or nickel in the lattice were found to be excellent heterogeneous catalysts for the concurrent synthesis of dimethyl carbonate and ethylene glycol by transesterification of ethylene carbonate with methanol. The catalytic activity strongly depends on the elemental composition of the catalysts and is correlated with the number of moderately basic sites present on the catalyst.     

The reaction of ethylene oxide with oleic acid

The base-catalyzed reaction of ethylene oxide with oleic acid can be divided into two stages. The first stage consists of a slow reaction of oleic acid with ethylene oxide to form principally ethylene glycol monooleate; other reactions such as esterification, transesterification and polyglycol formation lag behind. In the second stage, after the addition of approximately one mole of ethylene oxide, the reaction accelerates and transesterification equilibrium is rapidly attained. The composition of products containing several molecules or more of ethylene oxide can be calculated satisfactorily on the assumption of random addition of ethylene oxide and random esterification of the hydroxyl groups. The uncatalyzed reaction is much slower and transesterification equilibrium is attained slowly, if at all. A reaction mechanism based on the difference in basicities of the carboxylate and alkoxide ions (and the relative rates of the competitive ethylene oxide reactions) is presented for the base-cat-alyzed reaction.     

酯交换法碳酸二甲酯生产技术的市场分析

作为一种绿色基础化工原料,碳酸二甲酯具有广泛的用途。介绍了碳酸二甲酯的几种生产技术如光气法、甲醇氧化羰基化法和酯交换法,并进行了分析比较。从酯交换法的主产品碳酸二甲酯和副产品丙(乙)二醇的市场来看,酯交换法具有较大发展空间,应尽快加速发展与推广。     

涤纶染色改性剂SIPG合成研究

研究了以５－磺酸纳－间苯二甲酸二甲酯为原料进行酯交换反应合成５－磺酸钠－间苯二甲酸双乙二酯(ＳＩＰＧ),并讨论了催化剂、反应温度、配比等反应条件对产品质量的影响。通过优化工艺条件,合成的产品具有二甘醇含量低,低温条件下稳定性好的特点。     

Biodiesel Production Using a Carbon Solid Acid Catalyst Derived from β‐Cyclodextrin

A novel carbon solid acid catalyst was prepared by incomplete hydrothermal carbonization of β‐cyclodextrin into small polycyclic aromatic carbon sheets, followed by the introduction of –SO₃H groups via sulfonation with sulfuric acid. The physical and chemical properties of the catalyst were characterized in detail. The catalyst simultaneously catalyzed esterification and transesterification reactions to produce biodiesel from high free fatty acid (FFA) containing oils (55.2 %). For the as‐prepared catalyst, 90.82 % of the oleic acid was esterified after 8 h, while the total transesterification yield of high FFA containing oils reached 79.98 % after 12 h. By contrast, the obtained catalyst showed comparable activity to biomass (such as sugar, starch, etc.)‐based carbon solid acid catalyst while Amberlyst‐15 resulted in significantly lower levels of conversion, demonstrating its relatively high catalytic activity for simultaneous esterification and transesterification. Moreover, as the catalyst can be regenerated, it has the potential for use in biodiesel production from oils with a high FFA content.     

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.     

新型共聚酯-PETG

PETG(聚对苯二甲酸乙二醇酯-1,4-环己二甲醇酯)是一种结晶度很低甚至是完全不结晶的共聚酯,具有优异的韧性、透明度、易加工和耐化学性能。它是由DMT(对苯二甲酸二甲酯)、EG(乙二醇)、CHDM(1,4-环己二甲醇)在通N2条件下发生酯交换反应,然后在高真空度下发生缩聚反应而制得。本文就PETG的制备、性能和应用等方面作一论述。     

Glycolyzed poly(ethylene terephthalate) waste and castor oil-based polyols for waterborne polyurethane adhesives containing hexamethoxymethyl melamine

Glycolysis of poly(ethylene terephthalate) (PET) waste using different molar ratio of poly(ethylene glycol) (PEG400), was used to produce saturated hydroxyl-functional polyester polyols with castor oil (CO) by transesterification process. The waterborne polyurethane (WBPU) adhesives were synthesized from these saturated polyester polyols, isophorone diisocyanate (IPDI), dimethylolpropionic acid (DMPA), and hexamethoxymethyl melamine (HMMM) as cross-linking agent by a conventional prepolymer process. The glycolyzed polyols and polyester polyos formations were characterized using Fourier transform infrared spectroscopy (FTIR) and the molecular weights were determined using gel permeation chromatography (GPC). The cross-linking reaction between WBPU and HMMM was verified using FTIR and ¹H NMR analysis. Thermal properties were investigated by thermogravimetric analysis (TG). Thermal stability of cross-linked WBPU significantly increased with decreasing castor oil content in the process of transesterification to obtain polyester polyol as a soft segment. The T_15% and T_50% (the temperature where 15 and 50% weight loss occurred) of WBPU increased with the decreasing of castor oil content in the obtained polyester polyols, caused by the steric hindrance of polyester polyol with higher castor oil content, in the process of cross-linking reactions with HMMM. The physico-mechanical properties of WBPU, such as hardness, adhesion test, and gloss of the dried films were also determined considering the effect of participation of HMMM in cross-linking reactions with polyurethane, on coating properties.     

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.