Study of the low temperature pyrolysis of PVC

The characteristics of PVC pyrolysis dechlorination has been studied in a fixed bed reactor under different operating conditions such as temperature, time, heating rate. It is found that about 90% chlorine in PVC can be effectively removed within 3 h with heating rate of 5 mu/min at temperature 300 degreesC, with 10% chlorine remaining in volatile gas and residue. The yield of combustible gas increases and the yield of tar as well as residue decreases with the increasing of the pyrolysis temperature. Thermogravimetric technique was used to investigate the weight-loss curves of PVC pyrolysis process; elemental analysis and FTIR were conducted to analyze the functional-group composition of products. The results showed that the PVC pyrolysis is a two-step process. The first step is mainly a dechlorination process which, accompanied by depolymerization and this reaction, can be seen as a first-order reaction: apparent energy activation is about 130 kJ/mol. The second step is a further cracking process of the residue which produces low molecular hydrocarbons including alkene and aromatic compounds.