TPA和EG连续生产PET的第一酯化反应器操作模拟

对乙二醇(EG)和对苯二甲酸(TPA)连续生产对苯二甲酸乙二酯(PET)的第一酯化反应器进行了数学模拟。数学模型中包括了反应动力学方程、气液平衡和气液传质方程,使模拟结果接近于工厂实践。此外对不同停留时间、不同的反应器操作温度及压力、不同的进料 EG/TPA 的 mol比,进行了模拟计算,得出了反应器出口各种产物的组成随操作参数的变化,并对各操作参数的范围和对反应的影响进行了评述。     

Solubility and esterification kinetics of terephthalic acid in ethylene glycol III. The effects of functional groups

Clear time (t_cl), the time required for the turbid mixture of terephthalic acid (TPA) and ethylene glycol (EG) to be clear, was measured to examine the effect of poly(ethylene terephthalate) (PET) prepolymer (DP of 1–5) on the kinetics of dissolution and/or ester-ification of TPA with EG. The t_cl of the mixture of TPA/EG (1 : 1.5 in molar ratio) was reduced to 1 : 2.2 or 1 : 3.5 by addition of 30 wt % of PET prepolymer or bis-(2-hydroxyl ethyl) terephthalate (BHET), respectively. Diethyl terephthalate (DET) as an addititive was used as a model compound to examine the effects of the —OH group on the esterification reaction of TPA/EG. The t_cl value increased with addition of DET. The effect of the carbonyl group was also examined by determining esterification rates of benzoic acid (BA) with either ethylene glycol monobezoate (EGMB) as a compound with carbonyl group, or 2-penoxyethanol (2-PhE) as a compound without the carbonyl group. The reaction rate of BA with EGMB was much higher than that of BA with 2-PhE, which indicates that the carbonyl group gave an increasing effect of the esterification rate. Fourier transform infrared spectra showed that the —OH group in both BHET and EGMB formed intramolecular hydrogen bonding with the ester carbonyl group. On the basis of these observations, we concluded that the electron density of oxygen in the hydroxyl group increased through the formation of the intramolecular hydrogen bond. The increased electron density gave the —OH group easier access to the carbonyl carbon in BA, leading to an increase in the esterification rate. © 1996 John Wiley & Sons, Inc.     

Optimization for the minimum reaction time of pet esterification

We have investigated the direct esterification reaction between terephthalic acid (TPA) and ethylene glycol (EG) in semi-batch reactors, the first stage process for making polyethylene terephthalate (PET), to get optimum conditions for the minimum reaction time. An independent-variable-minimization problem, i.e., a free-end-time/fixed-end-point problem, has been formulated for the system, and then converted to a dependent-variable-minimization (fixed-end-time/ free-end-point) problem by a coordinate transformation, for the latter problem readily yields to established solution methods. We have solved this reformulated problem to obtain the optimal temperature profiles in the reactor required for the minimum reaction time, by iteratively improving the temperature (manipulating variable) profile using the Pontryagin’s minimum principle. The results prove that the method employed here successfully finds an optimal solution for the PET esterification process. The reduction of the reaction time realized following this optimal temperature profile in the reactor was, however, found to be smaller than expected, due to the approximating assumptions of neglecting the solubility equation of TPA in the model. The results obtained using a more improved model of the system will be reported in the future.     

对苯二甲酸与1,4-环己烷二甲醇直接酯化反应的研究

研究了对苯二甲酸（TPA）与1,4-环己烷二甲醇（CHDM）的直接酯化反应,讨论了酸/醇配比、催化剂用量对酯化反应的程度、反应时间的影响,对实验过程及动力学处理方法进行了分析探讨,并对实验结果进行了相应的整理,得到了该反应的动力学参数,确定了较佳的工艺条件。此外,在相同酸/醇配比和催化剂用量时还进行了TPA与乙二醇（EG）的直接酯化实验并进行了酯化动力学分析。结果表明,较佳的工艺条件为酸/醇比1:1.6,催化剂用量3.5/104（质量比,下同）;TPA与CHDM的直接酯化反应比TPA与EG的反应对温度的敏感程度低,反应时间短、活化能小。     

Identification of kinetics of direct esterification reactions for PET synthesis based on a genetic algorithm

In this study we propose a method to identify the kinetics of direction esterification reactions for polyethylene terephthalate (PET) based on a genetic algorithm. The reaction rate parameters could be identified successfully by using a genetic algorithm and plant data. The effects of key operating variables (temperature, pressure, monomer feed ratio and residence time) on the reactor performance were also investigated. It was observed that the reactor performance strongly depends on the degree of dissolution of the solid terephthalic acid (TPA) in the reaction mixtures.     

Influence of reaction temperature on direct esterifications in a continuous recycling process between terephthalic acid and ethylene glycol

Simulations were carried out with a continuous recycle esterification model for the terephthalic acid–ethylene glycol (TPA–EG) system proposed previously. The influence of reaction temperatures, recycle ratios, and residence times on the oligomer characteristics was examined and the following results were obtained: (1) The main reactions proceed more under higher reaction temperatures, but the side reactions on diethylene glycol (DEG) proceed further than do the main reactions. (2) The higher residence time ratio of the first reactor to the total results in the proceeding of esterifications, which becomes remarkable as the temperature becomes high. (3) As the recycle ratio becomes high, the esterfications proceed, but in the very high degree of esterification, the tendency is reversed. (4) The characteristics of oligomer are almost the same at the same degree of esterification, independent of the reaction conditions. © 1994 John Wiley & Sons, Inc.     

A mathematical model for computer simulation of a direct continuous esterification process between terephthalic acid and ethylene glycol

To study the effect of potassium titanium oxyoxalate on the esterification reaction of terephthalic acid (TPA) and ethylene glycol (EG) in the first tank reactor of TPA/EG continuous esterification, experiments at various addition rates of potassium titanium oxyoxalate were made in the pilot plant. Potassium titanium oxyoxalate accelerated the esterification reaction of TPA and EG. Also, reaction rate constants of the reaction scheme reported in a previous report were fitted with the experimental results, and the calculated values of physical properties of oligomers obtained from these reaction rate constants showed relatively good agreement with experimentally obtained physical properties of the oligomers. The effect of potassium titanium oxyoxalate on the reaction rate constants was expressed by a set of seven equations: Using the resultant reaction rate constants, the esterification reaction at various addition rates of potassium titanium oxyoxalate were stimulated and the following conclusions drawn:

• 1 Under low pressure close to atmospheric, when the amount of water in the reaction mixture is very low, the decomposition of potassium titanium oxyoxalate proceeds slowly and decomposition can be practically neglected.
• 2 Potassium titanium oxyoxalate accelerates the esterification reaction.
• 2 Potassium titanium oxyoxalate mainly accelerates the main reactions and its effects on side reactions are rather weak. As a result, the higher the addition rate of potassium titanium oxyoxalate, the lower the values of AV and DEG, as is preferable.

     

β-二酮铝和β-二酮酯铝催化合成聚对苯二甲酸乙二醇酯

采用对苯二甲酸(TPA)和乙二醇(EG)为原料,以自制的β-二酮铝和β-二酮酯铝为催化剂经酯化、缩聚,制得聚对苯二甲酸乙二醇酯(PET).探讨了反应条件对合成反应的影响.结果表明:β-二酮酯铝和乙酰丙酮铝优于其他β-二酮铝.EG与TPA的摩尔比为1.2∶1、催化剂的用量为0.5%(与TPA的摩尔比),酯化反应温度为26...     

Heat Transfer Studies in an Agitated Vessel During Aqueous Alkaline Depolymerization of Poly(Ethylene Terephthalate) (PET) Waste

Depolymerization reactions of poly(ethylene terephthalate) (PET) waste in aqueous sodium hydroxide solution were carried out in a batch reactor at 150°C at atmospheric pressure. Disodium terephthalate (terephthalic acid salt) and ethylene glycol (EG) remain in the liquid phase. Terephthalic acid (TPA) salt was converted into TPA. The produced monomeric products (TPA and EG) were recovered. Various design parameters were estimated. Design of a batch reactor was undertaken for depolymerization of PET waste in aqueous sodium hydroxide solution. As expected, the Reynolds numbers, Prandtl numbers, Nusselt numbers, coil-side heat transfer coefficients, and overall heat transfer coefficients were consistent with the fluid velocities. It shows excellent potential for commercialization of the depolymerization of PET waste.     

Depolymerization of poly(ethylene terephthalate) in dilute aqueous ammonia solution under hydrothermal conditions

BACKGROUND: Various methods, such as glycolysis, methanolysis, and hydrolysis with supercritical water, have been investigated for chemical recycling of poly(ethylene terephthalate) (PET), which is used in large quantities for beverage containers. However, a more effective process is needed. RESULTS: PET was depolymerized in aqueous ammonia in a batch reactor and a semi‐batch reactor over a temperature range 463 to 573 K, at a pressure 10 MPa, and with up to 3 mol L^?1 ammonia. Total organic carbon in the product solution and yields of the major products such as terephthalic acid (TPA) and ethylene glycol (EG) were measured. The PET pellet sample was thoroughly solubilized in aqueous ammonia under hydrothermal conditions, and more than 90% of the initial PET samples were recovered as TPA + EG on a carbon weight basis. Depolymerization rates were represented by 2/3‐order reaction kinetics with respect to unreacted PET, where the reaction took place on the PET pellet surface. The rate increased slightly with increasing ammonia concentration. CONCLUSION: Ammonia was effective for depolymerization of PET, allowing the recovery of TPA and EG under hydrothermal conditions. Copyright © 2008 Society of Chemical Industry     

A mathematical model for computer simulation of a direct continuous esterification process between terephthalic acid and ethylene glycol: Part 1. Model development

A new mathematical model has been developed for the continuous esterification process of terephthalic acid (TPA) and ethlene glycol (EG) with consideration of oligomer characteristics. The liquid weight fraction in the reaction mixture, β, has been selected as a principal parameter in this model. The solubility of TPA in EG and bis β-hydroxyethyl terephthalate (BHET) has been measured in order to estimate more precisely the concentration of each component. Good agreement has been obtained by plotting the log of solubility data of TPA in EG and BHET against the reciprocal of the absolute temperature with correlation coefficients of 0.998 and 0.989, respectively. The validity of these data has been verified in comparison with other data.     

聚酯（PET）反应过程研究：Ⅲ酯化反应过程中传质研究

对酯化反应过程中发生的传质分别进行了分析和研究，得到了ＴＰＡ溶解度关联式；ＥＧ，水和齐聚物的汽液平衡数据；反应器内ＥＧ和水的气液传质速率关联式以及工艺塔的简化模型     

聚酯(PET)反应过程研究⒇Ⅳ酯化反应过程数学模拟

通过对酯化反应器流动模型的分析结合酯化反应化学平衡、反应动力学和反应器内传质的研究建立了适用于多种工业酯化反应器的数学模型     

PET装置EG降耗的措施

对EG损耗影响因素进行分析后,通过改进酯化水分离塔,增大酯化釜,平衡原料量比,缓和工艺反应条件来降低酯化中的裂解副反应,降低EG单耗,减少对大气的污染,进一步推进装置清洁化生产。     

Modeling of poly(ethylene terephthalate) reactors: 4. A continuous esterification process

A mathematical model has been developed for the direct, continuous esterification process. Influence of process and operational variables, including temperature distribution, residence time distribution, bis(hydroxyethyl)terephthalate recycle, pressure, and ethylene glycol (EG) to terephthalic acid ratio on the reactor performance have been investigated in a range as close to industrial practice as possible. The variables influencing the amount of EG reflux (which governs the energy economy) and side products (which govern the product quality) have been discussed. This investigation provides an analysis of a continuous, direct esterification process, and the results indicate strategies for optimizing productivity and product quality.     

聚酯（PET）反应过程研究：Ⅱ.酯化反应过程动力学研究

对乙二醇和对苯二甲酸直接酯化反应过程的主反应动力学和生成ＤＥＧ副反应的动力学进行了研究，得到了不同温度下的反应速率，进而获取了各反应的活化能和频率因子。     

Flame retardant polyesters. I. Phosphorous flame retardants

Commercially available two types of phosphorous flame retardants (FRs) for polyester were compared from the viewpoint of chemical reactivity, reaction mechanism, and byproduct formation. 3‐(Hydroxyphenyl phosphinyl) propanoic acid (HPP) and 9,10‐dihydro‐9‐oxa‐10‐2,3‐dicarbonylpropyl)‐10‐phosphophenanthrene‐10‐oxide (DI) were used as a main chain type and a pendant type, respectively. HPP and DI showed different behavior with ethylene glycol (EG). More acidic HPP reacted with EG spontaneously and then produced esterified terminal hydroxy end group reacted with EG to form terminal diethylene glycol (DEG) end group. But the composition in the HPP solution was not varied for a long time below the esterification temperature. Contrast to HPP, DI showed normal esterification procedure. DI esterified with EG to form DI ester of EG, and DEG formation is not distinct. The difference of reactivity and DEG formation is caused by the difference of acidity in EG solution. For production of phosphorous containing polyester, it is desirable that HPP is introduced into the reactor in the mere solution state and DI in the esterified state. In addition, for production of polyester having the same phosphorous content in commercial scale, it is more beneficial to apply HPP than DI because of low input of FR due to low molecular weight. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Sodium Methoxide Catalyzed Depolymerization of Waste Polyethylene Terephthalate Under Microwave Irradiation

Chemical recycling of polyethylene terephthalate (PET) to produce terephthalic acid (TPA) was studied using in situ hydrolysis with sodium methoxide in methanol and dimethyl sulfoxide (DMSO) as solvent under microwave irradiation. The microwave-assisted reaction was carried out at different temperatures, and reaction time between 5 to 30 min. High degrees of depolymerization were examined at temperature near 70°C at microwave power 300 W. The reaction was carried out in a sealed microwave reactor in which the time and temperature were controlled and recorded. The products were mainly monomers such as TPA and ethylene glycol (EG) which were isolated and purified for further analysis. Monomethyl terephthalate, dimethyl terephthalate, and terephthalic acid were formed initially then converted to TPA as a single monomer product. Purified, TPA was analyzed and identified by NMR, TGA, DSC and FTIR. It was observed that the reaction greatly depends on the amount of sodium methoxide, the volume of methanol and DMSO used, the reaction time, and temperature. Compared to conventional heating methods, the time needed to achieve complete degradation of PET was significantly reduced to 5 min by using microwave irradiation and sodium methoxide catalyst. This has led to substantial saving in energy and cost supporting the conclusion that this proposed recycling process is very beneficial for the recycling of PET wastes.     

间歇TPA法制备PET过程中DEG生成规律及控制方法

我们在二升间歇装置中,对高纯度对苯二甲酸(TPA)和乙二醇(EG)直接酯化缩聚(简称TPA法)时的酯化温度、酯化压力、酯化时间及醚键抑止剂的添加量,作了一系列的试验。其结果表明:采用TPA法制备PET主要在酯化阶段生成副产物DEG,其量占总量80％。其次是缩聚阶段;提高酯化反应速度,宜用加压法来实现,一般反应压力4.0×10~5Pa、反应温度250℃;及时除去反应系统中多余的EG;添加适量的醚键抑止剂可有效地降低DEG的生成。     

聚氨酯用二聚酸聚酯二醇的合成

研究了以辛酸亚锡为催化剂、二聚酸（DA）与乙二醇（EG）为原料、制备聚氨酯用二聚酸聚酯二醇的方法,讨论了催化剂的类型和用量、反应温度、原料醇酸比、反应时间等对酯化率的影响,并用红外光谱对合成产物进行了表征。结果表明,DA与EG摩尔配比为1：2．4,催化剂辛酸亚锡用量为原料总质量的0．3％,反应温度在1h内缓慢升温到190℃,然后保温反应4h,并在130℃、2．66kPa下减压3h,酯化率可达99．7％,产品羟值为95mgKOH／g,酸值0．26mgKOH／g。