Effect of hydrogen transferred from solvent and gaseous hydrogen on thermal decomposition of dehydrochlorinated poly(vinyl chloride)

Poly(vinyl chloride) (PVC) dehydrochlorinated at 300 °C was decomposed in tetralin at 440 °C or 470 °C for 60 min under 7.1 MPa initial pressure of nitrogen or hydrogen or of hydrogen in the presence of a nickel–molybdenum catalyst. A tetrahydrofuran-insoluble fraction, a hexane-insoluble undistilled fraction, a hexane-soluble undistilled fraction, and a liquid product were the main products at both temperatures. At 440 °C under nitrogen, the yield of liquid product was 7.1%, but the yield increased to 43.2% under hydrogen in the presence of the catalyst at 470 °C. Linear relationships were observed between the yields of the products derived from the dehydrochlorinated PVC and the total amounts of hydrogen transferred from tetralin and gaseous hydrogen. Hydrogen transferred from the solvent and from gaseous hydrogen promoted the degradation of dehydrochlorinated PVC and reduced the amount of residual chlorine in the degradation products.