Ester interchange reactor

Ravindranath, K. and Mashelkar, R. A., Modeling of poly(ethylene terephthalate) reactors 1. A semibatch ester interchange reactor, J. Appl. Polym. Sci., 26, 3179-3204 (1981). 

Description A slurry composed of PTA and EG, or molten DMT and EG is fed to the first esterification/ester-interchange reactor (1) in which main reaction occurs at elevated pressure and temperatures (200°C-270°C). Reaction vapors—water or methanol—are sent to a low/high boiler separation column. High boilers are reused as feedstock. 

Yoshioka, T., Motoki, T. and Okuwaki, A., Kinetics of hydrolysis of poly(etliylene terephthalate) powder in sulfuric acid by a modified slirinking-core model, Ind. Eng. Chem. Res., 40, 75-79 (2001). Ravindranatli, K. and Mashelkar, R. A., Modeling of poly(etliylene tereph-tlialate) reactors 1. A semibatch ester interchange reactor, J. Appl. Polym. Set, 26, 3179-3204 (1981). 

Patty esters (wax esters), formed by ester interchange of the product alcohol and the starting material in the hydrogenolysis reactors, are later separated from the product by distillation. Unreacted methyl esters are also converted to fatty esters in the distillation step... 

Alcoholysis (ester interchange) is performed at atmospheric pressure near the boiling point of methanol in carbon steel equipment. Sodium methoxide [124-41 -4] CH ONa, the catalyst, can be prepared in the same reactor by reaction of methanol and metallic sodium, or it can be purchased in methanol solution. Usage is approximately 0.3—1.0 wt % of the triglyceride. 

Ravindranath and Mashelkar 88 Semi-batch Ester interchange Stirred tank reactor... 

An alkaline catalyst, sodium methoxide, is created in the same reactor as the ester interchange by first adding sodium metal to the methanol before the triglyceride is introduced. The reaction is performed batch by batch in a carbon-steel vessel at atmospheric pressure. The reaction, shown in the top part of Figure 15—2, results in glycerol and three fatty methyl esters. 

Fatty Acid-Oil Process. When oil represents only a minor portion (33% or less) of the total furnish of fatty acids in an alkyd formulation, the alcoholysis step may be avoided. All of the ingredients, dibasic acid, polyol, oil, and free fatty acids may be charged together into the reactor and proceed as in the fatty acid process. Apparently, the oil is incorporated into the resin by ester interchange at the reaction... 

Due to different residence times needed for the reaction steps, the industrial batch processes are typically run in multiple reactors. Usually two reactors are involved, an ester interchange (El) reactor designed to extract methanol or water and a poly condensation (PC) reactor designed to drive the polymerization and build molecular weight by removing excess... 

Let us now examine the intrinsic causes of oligomer formation during the transesterification reaction. In the transesterification process, the extent of reaction has traditionally been followed by measuring the methanol withdrawn from the reactor. It has been shown [6] that a model based on the ester interchange reaction... 

Various esters of acrylic add are commercially available but methyl, ethyl and butyl acrylates are the most widely used. These esters are obtained by esterification of acrylic acid. The appropriate alcohol, acrylic acid and a catalyst (generally sulphuric add) are fed into a reactor at about 80°C and the ester separated by distillation. Higher acrylates are conveniently prepared by ester interchange. 

Ester interchange is favored for terephthalates because the free acid is very insoluble and difficult to incorporate into a reaction system. Two stages are used In the first, methanol is displaced from the terephthalic acid ester by the diol, and in the second, the excess diol is driven off at high temperatures and low pressures. A continuous process (Figure 17.1) starts with a molar ratio of dimethyl terephthal-ate to glycol of 1 1.7. Methanol is removed from the horizontally sectioned vessel over a period of 4 h with a rise in temperature to 245°C at a pressure of 1 atm. In two polycondensation reactors, the pressures are about 0.020 and 0.001 atm, and the exit temperatures are 270°C and 280°C, respectively. The resultant polymer melt is low enough in viscosity that pumps can be used to extrude fibers directly or to make chips as an intermediate form for storage. 

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