聚酯装置酯化生产过程动态模拟

动态模型是进行生产过程动态优化的基础。本文采用链段法建立了聚酯装置酯化生产过程反应器和工艺塔相互影响的动态模型,分析了基本控制系统作用下过程操作工况的动态阶跃响应特性。模拟结果表明,酯化反应器进料摩尔配比及反应器温度、压力、液位的调整显著影响了酯化过程气相流的变化,且对反应产物中端羧基含量和聚合度等指标的响应比较灵敏;控制系统对稳定酯化生产过程操作起着显著的作用。     

High concentration of 1-(3-)monoglycerides by direct partial esterification of fatty acids with glycerol

An improved method for the production of monoglycerides (MO) by direct esterification of fatty acids with glycerol was developed. The reaction medium was composed of oleic acid (72% purity, OA), glycerol (Gly), dodecylbenzene sulfonic acid (DBSA) as catalyst, and emulsifying agent, as well as of a molecular sieve as drying agent. Partial esterification of glycerol by oleic acid is carried out in either a batch reactor and in a column filled with a molecular sieve according to a continuous process. In a discontinuous batch reactor, the OA/Gly/DBSA system gives 28% of 1-(3-)MO and strong proportions of di- and triesters. The addition of the 3A molecular sieve to this system makes it possible to increase the selectivity in 1-(3-)MO (47%). However, the reaction carried out in a column filled with a 3A molecular sieve produced a mixture containing 60% of 1-(3-)MO after deacidification and removal of the catalyst and shows the advantage of a continuous process.     

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.     

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。     

A simulation study on continuous direct esterification process for poly(ethylene terephthalate) synthesis

A mathematical model for a continuous direct esterification reactor has been developed. The solid-liquid equilibrium of terephthalic acid (TPA) was considered in our modeling, and the characteristic dissolution time, an adjustable parameter, was introduced to account for the mass-transfer effect in the dissolution of TPA. The effects of the characteristic dissolution time, monomer feed ratio, temperature, and pressure on the reactor performance at different residence times were investigated through simulation. It was observed that the behavior of the first reactor strongly depends on whether the solid TPA is completely dissolved in the reaction mixtures. From the dynamic simulations, it was found that a sudden change in the operating conditions affects the ethylene glycol (EG) vapor flow rate instantly. For the esterification process having two reactors in series, the strategy for time distribution and recycling of EG is also discussed. © 1997 John Wiley & Sons, Inc.     

五釜工艺聚酯工业装置的稳态模拟

针对大型连续PTA直接酯化法PET工艺过程装置,以Aspen Plus和Polymers Plus为模型开发工具,建立了以反应和传质过程机理为基础的稳态模型。结果表明:该模型中包括了酯化反应、缩聚反应、二甘醇生成反应、链降解反应和乙醛生成等主副反应,且考虑了端羧基对酯化反应的自催化效应;更重要的是模型考虑了酯化阶段PTA在酯化反应器中的溶解过程和终缩聚阶段小分子的脱挥,并建立了小分子脱挥的传质系数与缩聚反应器内聚合度、黏度、温度和搅拌器转速等的关联;在此模型基础上模拟研究了第一酯化反应操作温度对各反应器出口指标的影响,指出酯化段的酯化率有一个适宜的控制范围。     

Esterification of Acetic Acid and Ethanol in a Flow‐Through Membrane Reactor Coupled with Pervaporation

The esterification of acetic acid is an important industrial process for the synthesis of ethyl acetate. A membrane reactor with a sulfonated polyethersulfone/polyethersulfone/non‐woven fabrics composite catalytic coupled with a poly(vinyl alcohol) pervaporation membrane was applied in continuous esterification of ethanol with acetic acid in a flow‐through mode. High equilibrium conversion was obtained for esterification in a closed‐loop mode. For the pervaporation‐assisted esterification in this mode, the experimental conversion was very close to the theoretical value.     

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.     

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。     

渗透汽化-酯化反应耦联膜过程动力学模型

建立了渗透汽化 -酯化反应耦联复合膜反应器过程动力学模型及测量复合膜渗透率的方法 .该动力学模型较系统地考虑了复合膜反应器中可能影响酯化反应化学平衡移动的各种因素 .研究结果表明 ,模型的模拟结果能很好地与实验结果相吻合 .     

Towards a continuous process in heterogeneous coordinated anionic ring opening polymerization

Summary The current article deals with the initial developments of the use of a continuous plug flow reactor using an original heterogeneous catalyst system for the living coordinated anionic polymerization of certain oxygenated rings. This reactor is designed in order to maintain the essential characteristics of the original batch system. One of the pertinent parameters considered here is the residence time of the reactants inside the reactor. The column has been used to investigate ethylene oxide and -caprolactone oligomerization. Initial experiments have pointed out how the molecular weights can depend on the flow rate for a fixed bed length. Some theoretical problems relative to the reactive column are discussed in order to investigate more in depth the properties of this original continuous process and to model it to find the optimal working conditions.     

Membrane reactors in chemical production processes and the application to the pervaporation-assisted esterification

When appropriate membrane was used for the assistance of chemical and biochemical equilibrium reactions, it is possible to enhance the yield and the purity of the reaction product by selectively adding educts or selectively removing products and to a lower the energy input and the reaction time compared to conventional process. In this paper a review on membrane reactors with special emphasis on membrane-assistance of esterification reactions and a continuous tube membrane reactor for the pervaporation-assistance of the esterification are presented. The heterogeneously catalyzed esterification of ethanol and acetic acid to ethyl acetate and water was investigated as a typical chemical equilibrium reaction. The selective and simultaneous water separation from the reaction mixture of the esterification with polyvinyl alcohol pervaporation membranes is considered to be an interesting process alternative to the conventional distillation process. Compared to the distillation process, for the pervaporation-assisted process a decrease of the energy input of over 75% and of the investment and operating coasts of over 50% each was calculated.     

PET连续聚合工艺流程优化改造

采用将五釜流程改为四釜流程的方法,即以酯化预聚塔一个反应器取代五条工艺流程的第二酯化釜和第一预缩聚釜两个反应器,对PET聚合工艺流程优化,改造后的PET单线生产能力由160t/d提高到200 t/d,其单耗PTA由改造前的865 kg/t降至863 kg/t,EG由338 kg/t降至334 kg/t,降低了成本,提高了产品质量。     

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.     

规模化聚酯装置酯化过程的机理模型化

聚对苯二甲酸乙二醇酯(PET)酯化反应体系的热力学物性计算、动力学常数的整定是实现聚酯工业生产装置模型化的2个重要部分。对聚酯酯化过程的各主副反应——酯化反应、缩聚反应、水解反应、醇解反应、二甘醇生成反应进行机理分析和参数比较,确定了聚酯生产全流程模拟的动力学常数的合理范围。通过动力学参数对目标产物对苯二甲酸、二甘醇、乙二醇、PET质量流量影响的灵敏度分析,修正了反应动力学常数使之适应特定的工业装置,结合物性计算方程建立了规模化聚酯装置酯化工段的机理型数学模型。利用不同生产负荷的工业数据对模型进行了验证,其误差在3%以内。     

Measurement of the melting points of oligomers obtained in the manufacture of poly(ethylene terephthalate)

The melting points (T_m) were measured for oligomers obtained by a direct continuous esterification process between terephthalic acid and ethylene glycol. Multiple regression analyses of data were carried out, and an equation was obtained for predicting melting points with correlation coefficient of ～0.99.     

Studies of ethylene chlorohydrin formation in a bubble column reactor

An experimental study of the reactions of ethylene, chlorine, and water in a bubble column reactor, on a laboratory scale, has been carried out. The effect of gas flow rates on the yield of the products in an unbaffled reactor is reported. Baffles were introduced into the column to reduce axial mixing. A significant improvement in the conversion and yield of ethylene to ethylene chlorohydrin was observed.     

三相鼓泡淤浆床环氧乙烷合成反应器数学模拟及工程分析

建立了加压三相鼓泡淤浆床环氧乙烷合成反应器的数学模型 ,计入了催化剂颗粒在床层中沉降形成沿床高浓度分布对反应的影响以及由于惰性液相载体部分返混对传递的影响 ,进一步利用经实验验证的上述数学模型模拟不同表观气速、床高、反应器直径 (扣除传热元件截面积 )、进口乙烯摩尔分数等参数对床层中催化剂浓度随床高的分布、出口环氧乙烷摩尔分数、环氧乙烷选择率以及单位质量催化剂环氧乙烷年产量的影响 .通过模拟分析预示了工业三相床环氧乙烷反应器的合理尺寸、表观气速、环氧乙烷选择率以及时空产率 ,为工业化提供必要的设计依据     

Design of entrainer-enhanced reactive distillation for the synthesis of butyl cellosolve acetate

An innovative entrainer-enhanced reactive distillation (RD) process is presented, which aims to the production of high-purity butyl cellosolve acetate from butyl cellosolve and acetic acid via an esterification reaction. This entrainer-enhanced RD process can procure technical advantages from both heterogeneous azeotropic distillation and RD. Solvents such as cyclohexane, ethylene dichloride, toluene, and octane are considered as candidates in this esterification RD process. The function of entrainers is to simplify the separation between water and acetic acid. For this purpose, the proper entrainer to use is thus evaluated based on its mutual solubility with water in two liquid phases. Simulation results reveal that total annual cost can be substantially reduced when cyclohexane, toluene, and octane are used as entrainers in the RD column. The octane-enhanced RD provides the most economical design in this studied case.     

聚酯酯化反应通氮气工艺的研究

在常规聚酯酯化反应条件下,向20 mL酯化反应器通入氮气,探讨了通氮气对酯化反应速度的影响。结果表明:向酯化反应器通入氮气,有利于提高聚酯酯化反应速度,平均酯化反应速度比常规工艺提高19.18%。其中,向酯化反应器气相通入氮气,酯化反应速度比常规工艺提高27.7%。