Kinetics of alcoholysis of poly(ethylene terephthalate) in sub- and super-critical isooctyl alcohol to produce dioctyl terephthalate

Abstract

The alcoholysis kinetics of poly(ethylene terephthalate) (PET) in sub- and super-critical isooctyl alcohol (2-EH) to produce dioctyl terephthalate (DOTP) was studied with a batch reactor under the temperature range from 533 to 653K. Owing to the fast decomposition of DOTP to terephthalic acid (TPA) in the super-critical 2-EH, the kinetics was studied according to two conditions based on temperature less and more than critical temperature of 2-EH as pseudo-first-order reaction. In the sub-critical 2-EH about the temperature range of 533–593K, the decomposition of DOTP was very slow, and thus the apparent activation energy of production rate of DOTP is determined to be 82.14kJ/mol without taking into account decomposition of DOTP. Whereas, as for the super-critical 2-EH, the decompositions of DOTP should be taken into account, and a consecutive pseudo-first-order reaction model from PET to DOTP, TPA and subsequent decomposition products is adopted. The apparent activation energies of production rates of DOTP are 30.29kJ/mol and the decomposition values of DOTP and TPA are 128.14 and 176.43kJ/mol of the super-critical temperature range of 613–653K.