Recycling of phenol from poly (1,4-cyclohexylene dimethylene terephthalate) using subcritical water from 260 to 340 °C

Abstract

Recycling of chemicals from waste plastics is important for the reutilization of resources and the reduction of environmental pollution. The phase behaviors of poly (1,4-cyclohexylene dimethylene terephthalate) (PCT) in water at different temperature and time were observed in a fused silica capillary reactor (FSCR) with a microscope. The effects of the reaction temperature (260−340 °C), the reaction time (30−90 min), and the mass ratio of water/PCT (6:1−14:1) on the degradation of PCT were studied in an autoclave reactor on the basis of the results obtained from the FSCR. Under our research conditions, depolymerization of both 1,4-cyclohexanedimethanol and terephthalic acid (TPA) generated mainly phenol, and the maximum yield of phenol was obtained at 340 °C after its reaction with a water/PCT mass ratio of 10:1 for 90 min. Moreover, a reaction mechanism of PCT degradation in subcritical water was proposed. Our results suggest that PCT can be depolymerized rapidly and completely in subcritical water to produce phenol, and this method is conducive to the recycling of waste PCT.