Depolymerization Of Poly (1,4-Cyclohexylene Dimethylene Terephthalate) In Subcritical Water Abstract

Depolymerization of poly (1,4-cyclohexylene dimethylene terephthalate) (PCT) in sub-critical water was researched in a batch autoclave reactor under different reaction conditions. The phase behavior of PCT was observed in a fused silica capillary reactor (FSCR). The products of depolymerization were analyzed quantitatively and qualitatively by Fourier-transform Infrared Spectroscopy (FT-IR), Liquid Chromatography, Mass Spectrometry (LC-MS) and High Performance Liquid Chromatography (HPLC). According to the ratio of PCT depolymerization, the yield of production and the phase behavior result, the activation energy of PCT depolymerization in sub-critical water was calculated.Phase behavior of PCT in sub-critical water was researched in FSCR. The results showed that with reaction time and tempreture increasing, PCT gradually melted and dissolved in sub-critical water completely at 350.0℃. Phase state in FSCR became gas-liquid from solid-gas-liquid. Reaction time of 30min when the tempreture up to 350.0℃,there is no phase change during the process, the oil droplet appeared in cooling process.The depolymerization of PCT was researched under the conditions of ratio of water/PCT (15.0～25.0), reaction temperature (240～320℃), reaction time (30～105 min). The results showed that PCT could be depolymerized completely when the experiments were conducted for 90 min at 320 ℃. It was calculated that the activation energy of PCT depolymerization was 89.0kJ·mol-1 by the results of kinetic analysis. The result of LC-MS show that the molecular formula of the main production of PCT depolymerization is C9H10O, instead of the monomer of PCT, p-phthalic acid (C8H6O4) and 1,4-Cyclohexanedimethanol (C8H16O2). And side product such as C9H12O2, C6H6O, C15H16O2 were detected.