Vacuum pyrolysis of PVC I. Kinetic study

Vacuum pyrolysis of PVC has been studied emphasizing two aspects: the kinetics of PVC pyrolysis reactions and the yields of pyrolysis products. The purpose of the kinetic study is to identify each apparent reaction involved in PVC pyrolysis. Three stages of weight loss have been evidenced by TG analysis during PVC decomposition both under vacuum and in nitrogen atmosphere, while in most previous studies carried out under similar conditions only two stages were detected. The corresponding temperature intervals of these three stages are: 200–320°C; 250–375°C and 375–520°C. Based on the TG results, a three-apparent-reactions model is proposed. Kinetic parameters and conversion factors have been calculated for each apparent reaction with this model including all three stages of decomposition. Some results are in good accordance with literature data. Bench scale PVC pyrolysis tests were carried out to collect the pyrolysis products from each single apparent reaction. These products were analyzed and a correlation with TG results was made in order to assign these results to a certain change of the PVC structure. These findings provide new insights into the PVC thermal decomposition and useful data for controlling the release of HCl during PVC pyrolysis have been made available.