Depolymerization of poly(trimethylene terephthalate) in supercritical methanol

The depolymerization of poly(trimethylene terephthalate) (PTT) in supercritical methanol was carried out with a batch-type autoclave reactor at temperatures ranging from 280 to 340degreesC, at pressures ranging from 2.0 to 14.0 MPa, and for reaction time of up to 60 min. PTT quantitatively decomposed into dimethyl terephthalate (DMT) and 1,3-propaniol (PDO) under the designed conditions. The yields of DMT and PDO greatly increased as the temperature rose. The yields of the monomers markedly increased as the pressure increased to 10.0 MPa, and they leveled off at higher pressures. The final yield of DMT at 320degreesC and 10.0 MPa reached 98.2%, which was much closer to the extent of the complete reaction. A kinetic model was used to describe the depolymerization reaction, and it fit the experimental data well. The dependence of the forward rate constant on the reaction temperature was correlated with an Arrhenius plot, which gave an activation energy of 56.8 kJ/mol. (C) 2004 Wiley Periodicals, Inc.