A kinetic study of the reaction between terephthalic acid and ethylene oxide at atmospheric pressure

The kinetics of the reaction of terephthalic acid with ethylene oxide, in n-butanol solvent, catalysed by triethyl amine, were investigated in a semi-batch reactor under atmospheric conditions. It was found that the reaction occurred in the liquid phase and that mass transfer effects were absent. The reaction was found to be pseudo-zero order in terephthalic acid and first order in ethylene oxide and in catalyst concentration. The effects of reaction temperature, catalyst concentration, particle size of terephthalic acid, ethylene oxide flow rate, stirrer speed and terephthalic acid to ethylene oxide ratio were studied. Particle size of terephthalic acid, stirrer speed and flow rate of ethylene oxide did not affect the reaction rate. The Arrhenius activation energy of the reaction was found to be between 19.2 and 23.5 kcal/mol.     

A kinetic study of the reaction between terephthalic acid and ethylene oxide in a nonsolvent system

Kinetics of the reaction between terephathalic acid and ethylene oxide, catalysed by triethylamine, was studied in a high-pressure reactor without using solvent. This reaction was carried out at a temperature range of 80–100°C and at a pressure range of 10–15 Kg/cm² beyond the corresponding vapor pressure of ethylene oxide. Effects of temperature, catalyst concentration, mole ratio of ethylene oxide to terephthalic acid, particle size of terephthalic acid, pK value of the tertiary amine and stirrer speed were experimentally investigated on the yield of bis(2-hydroxyethyl) terephthalate and reaction rates. It was found that the bulk reaction of terephthalic acid with ethylene oxide occurred in the liquid phase. Based on experimental results a reaction mechanism to synthesize bis(2-hydroxyethyl) terephthalate from terephthalic acid and ethylene oxide in a nonsolvent system was proposed, and rate constants were obtained with a model based on this proposed reaction mechanism. The activation energy of the reaction was found to be between 3.67–8.28 kcal/mole in the temperature range of 80–95°C.     

Kinetics of the reaction between terephthalic acid and ethylene oxide under high pressure

Kinetics of the reaction between terephthalic acid and ethylene oxide in n-butanol solvent, catalyzed by triethyl amine, was investigated under high pressure. Effect of temperature, catalyst concentration, ethylene oxide to terephthalic acid ratio and stirrer speed was studied on the rate of formation of bis(2-hydroxy-ethyl)terephthalate. It was found that the reaction of terephthalic acid with ethylene oxide occurred in the liquid phase. The experimental data were correlated with a model based on S_N2 reaction mechanism and the activation energy of the reaction was found to be between 19.3–21.6 kcal/mole in the temperature range of 60–100°C.     

Reaction kinetics of the reaction of terephthalic acid and ethylene carbonates

The kinetics of the reaction of terephthalic acid with a number of ethylene carbonates in the presence of an amine catalyst were examined. All reactions apparently follow first-order kinetics; therefore, the solution rate of TPA is not rate-limiting. With minor adjustments, the mechanism appears to be in accord with that of the model reaction of benzoic acid and ethylene carbonate previously reported. Attack of the carboxylate on the carbonate ring must be the rate-limiting step. Substituent effects (owing to substituents on the carbonate ring) appear to be mostly steric in nature; surprisingly, an n-octyl group causes the slowest reaction. Besides being strongly influenced by steric hinderance, the transition state appears to be highly polar. Activation energy (16.0 kcal/mol) and activation entropy (?23.6 cal/deg) are very similar to those of the model reaction.     

Effect of pressure on the reaction between 3-methyl-1-p-tolyl-triazene and benzoic acid; A kinetic study

Rates of reaction between 3-methyl-1p-tolytriazene and benzoic acid were measured with variation of pressure in chloroform and acetonitrile. Activation volumes were found to be–15 and–4 cm³ mol⁻¹, respectively. The reaction mechanism is discussed in the context of these values.     

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.     

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.     

精对苯二甲酸干燥动力学模型

分析了精对苯二甲酸(PTA)干燥过程中干燥温度,物料初始含湿量,空气流速对干燥速率的影响。结果表明:PTA干燥过程由预热阶段、恒速阶段和降速阶段组成,临界含湿量为5%。随着干燥温度或初始含湿量的升高,干燥速率升高,随着载气流量的升高,干燥速率变化不明显。干燥温度对干燥速率的影响最为显著。通过模型比较得出合适的PTA干燥模型为Page模型,模型计算值与实验值吻合较好。     

Effect of diantimony trioxide on direct esterification between terephthalic acid and ethylene glycol

Experiments at various Sb₂O₃ concentrations were made in a pilot plant and the effect of Sb₂O₃ on continuous esterification between terephthalic acid (TPA) and ethylene glycol (EG) was obtained. Reaction rate constants of the previously reported reaction scheme were determined to fit with the experimental data obtained. It was found that the effect of Sb₂O₃ on reaction rate constant (k_i) can be expressed as follows.

• k₁ = (3.75 × 10^?4Sb + 1.0) × 1.5657 × 10⁹exp(?19,640/RT)
• k₂ = (4.75 × 10^?4Sb + 1.0) × 1.5515 × 10⁸exp(?18,140/RT)
• k₃ = (6.25 × 10^?4Sb + 1.0) × 3.5165 × 10⁹exp(?22,310/RT)
• k₄ = (4.50 × 10^?4Sb + 1.0) × 6.7640 × 10⁷exp(?18,380/RT)
• k₅ = (3.50 × 10^?4Sb + 1.0) × 7.7069 × exp(?2810/RT)
• k₆ = (1.75 × 10^?4Sb + 1.0) × 6.2595 × 10⁶exp(?14.960/RT)
• k₇ = (3.75 × 10^?4Sb + 1.0) × 2.0583 × 10¹⁵exp(?42,520/RT)

Simulation of esterification with these reaction rate constants at various Sb₂O₃ concentrations was made and the following results were obtained.

• 1 Sb₂O₃ accelerates the esterification reaction between TPA and EG.
• 2 Sb₂O₃ accelerates the main reaction and its effects on side reactions are minor. The higher the addition rate of Sb₂O₃, the lower the carboxyl end-group concentration (AV) and diethylene glycol content (DEG).
• 3 The comparison between simulation with potassium titanium oxyoxalate (PTO) in the previous report and with Sb₂O₃ in the present report shows that the acceleration of polycondensation reaction by Sb₂O₃ is higher. DEG formation rate is lower with PTO than Sb₂O₃.

     

Novel oxidation reaction at ambient temperature and atmospheric pressure with electric discharge and oxide surface

We investigated a novel oxidation reaction with surface-oxygen and lattice-oxygen induced using a non-equilibrium electric discharge at ambient temperature. We employed MgO, ZrO₂, and TiO₂ for this novel reaction. Methane was oxidized easily and converted into H₂, CO, and CO₂ by the surface-oxygen and lattice-oxygen of oxide with activation of discharge at ambient temperature without gas-phase oxygen. The oxide itself was stable after the reaction. Among these oxides, the tetragonal phase and amorphous phase of ZrO₂ showed remarkably high activity for methane oxidation. Consequently, up to 8% of surface and lattice oxygen of the oxide was consumed by methane oxidation induced by electric discharge. The non-equilibrium electric discharge activated both the surface-oxygen and the lattice-oxygen of the oxides and methane molecules in the gas phase. After these reactions, the oxide surface vacant sites were recovered partially through steam post-treatment. Hydrogen formed simultaneously with steam decomposition. Other reactions were also studied by changing the reaction gas: methane into carbon monoxide, carbon monoxide with oxygen, and carbon monoxide with steam. Furthermore, the correlation of reactivity between the feed gas and surface oxygen was studied. Emission spectra under a CH₄ atmosphere with electric discharge showed complex peaks caused by carbon monoxide formation at 280-500 nm at 0-4 min, suggesting that surface oxygen on oxides was probably consumed within 4 min from the start of the reaction.     

A mathematical model for a continuous esterification process with recycle between terephthalic acid and ethylene glycol

A new mathematical model for a continuous recycle esterification process has been derived by basically the same procedure as the continuous process of a cascade type, reported earlier, which includes material and heat balances. Such a model can give extensive information about the optimum design of a new plant through the predictions of oligomer characteristics (concentrations of carboxyl and hydroxyl end groups, number average molecular weight, number average degree of polymerization, esterification and saponification degree, DEG content, melting point of oligomer, etc.), distillate properties (concentrations of EG and water in the vapor phase), heat transfer area, mass flow rate of heating medium, amount of heat supplied by heating medium, enthalpy moving with recycle, and amount of heat removed from each reactor. © 1992 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.

     

The reactions in the polyesterification of terephthalic acid with ethylene glycol

Conclusions 1. A closed-system analysis was carried out of the kinetics and process equilibrium of the formation of dimer 1 which is one of the basic products of the initial state of the poly-esterification reaction of terephthalic acid and ethylene glycol.2. It was established that the hydrolysis of dimer 1 proceeds along only one complexester bond and results in the formation of TPA and BHET.3. The kinetic parameters of the esterification reaction MHET + MHET and the thermodynamic characteristics of the reaction TPA + BHET were determined.4. The rate and equilibrium constants of the reactions MHET + BHET and TPA + MHET were calculated in the first approximation.All-Union Scientific-Research Institute for Synthetic Fibres. Translated from Khimicheskie Volokna, No. 1, pp. 17–20, January–February, 1976.     

Mathematical model for a semicontinuous esterification process with recycle between terephthalic acid and ethylene glycol

A new mathematical model has been derived for a semicontinuous recycle esterification process that consists of two reactors, one has the recycle flow to or from another and the discharge flow of the main flow and another has only recycle flow without the discharge flow. This model can give useful information about the optimum design of a new plant through the predictions of oligomer characteristics such as concentrations of carboxyl and hydroxyl end groups, number-average molecular weight, number-average degree of polymerization, esterification and saponification degree, diethylene glycol content, melting point, concentrations of ethylene glycol and water in the vapor phase, and so on.     

Alkali decomposition of poly(ethylene terephthalate) with sodium hydroxide in nonaqueous ethylene glycol: A study on recycling of terephthalic acid and ethylene glycol

Pellets of poly(ethylene terephthalate) (PET; 0.48–1.92 g) were heated in anhydrous ethylene glycol (EG; 5 mL) with 2-equivs of NaOH at 150°C for 80 min or 180°C for 15 min to convert them quantitatively to disodium terephthalate (Na₂-TPA) and EG. The disodium salt was precipitated quantitatively in pure state from the EG solution and separated readily. The other product EG, being the same component to the solvent, remains in the solution and can be obtained after distillation as a part of the solvent. The rate of decomposition was significantly accelerated by the addition of ethereal solvents to EG, such as dioxane, tetrahydrofuran, and dimethoxyethane. The reaction system is simple; no water and no extra reagent other than NaOH and EG are used. A few recycling systems of PET can be designed on the basis of the present alkali decomposition reaction. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 595–601, 1997     

A kinetic study of the electrochemical hydrogenation of ethylene

In this study, we have examined the kinetics of the electrochemical hydrogenation of ethylene in a PEM reactor. While in itself this reaction is of little industrial interest, this reaction can be looked upon as a model reaction for many of the important hydrogenation processes including the refining of heavy oils and the hydrogenation of vegetable oils.To study the electrochemical hydrogenation of ethylene, several experimental techniques have been used including polarization measurements, measurement of the composition of the exit gases and potential step, transient measurements. The results show that the hydrogenation reaction proceeds rapidly and essentially to completion. By fitting the experimental transient data to the results from a zero-dimensional mathematical model of the process, a set of kinetic parameters for the reactions has been obtained that give generally good agreement with the experimental results. It seems probable that similar experimental techniques could be used to study the electrochemical hydrogenation of other unsaturated organic molecules of more industrial significance.