Thermal decomposition of poly(vinyl chloride) in organic solvents under high pressure

In order to study chlorination of the plastics derived liquid products by secondary reaction of hydrogen chloride, thermal decomposition of poly(vinyl chloride) (PVC) was carried out in decalin or tetralin at 300-460°C for 0-90 min under 4.0 MPa of initial nitrogen pressure. Dechlorination of PVC was completed in 30 min at 300°C, and further slight degradation of the dechlorinated PVC was observed in both solvents. Conversion of PVC to its liquid product proceeded with time at 400°C, and much more liquid product was produced in tetralin than in decalin. In the liquid product, 1,4-dichlorobutane was observed as the dominant organic chlorine product at 300°C, and its yield increased with the reaction time in both solvents. We detected 1,3-dichlorobutane, 1-chlorobutane, 2-chlorobutane, and chlorinated solvents as minor organic chlorine products. These results suggest that 1,4-dichlorobutane is a unique product of the secondary reaction between gaseous hydrogen chloride and the polyene chain derived from the dechlorination of PVC. In decalin, the yield of 1,4-dichlorobutane decreased with temperature, and the maximum yield of chlorodecalin was observed at 400°C. Conversely, yields of all organic chlorine compounds decreased with the reaction time in tetralin, and this hydrogen donorable solvent effectively prevented the production of organic chlorine compounds.