Comparing the effects of different metal oxides on low temperature decomposition of PVC
Polyvinyl chloride (PVC) is one of the most widely used plastics in the world. When PVC is heated, HCl will form, causing equipment corrosion, product quality decline, environmental pollution and other problems. Therefore, more attention is paid to recycling of PVC than other plastics. In this study, the reaction mechanisms of PVC with different metal oxides (MO x : CaO, ZnO, CuO, MgO, Fe 2 O 3 , Al 2 O 3 ) at low temperature (310 °C) were compared, with focus on chlorine capture and dehydrochlorination product (De-Cl PVC) property. The results showed that when the radius of metal ion was smaller, the extrapolated onset temperature ( T i ) of PVC-MO x pyrolysis tended to be lower, such as PVC-ZnO, PVC-CuO and PVC-Al 2 O 3 . Direct reaction of PVC and MO x was deduced for PVC-CuO and PVC-ZnO pyrolysis, based on the lower T i and peak temperature ( T max ) than that of PVC pyrolysis. MO x that did not significantly lower T max was supposed to react with HCl that dissociated from PVC. The addition of ZnO significantly reduced the release of HCl (0.5%) and captured 97.6% of chlorine as inorganic chloride salts. However, the chloride salts produced from PVC-MgO pyrolysis could decompose at low temperature, thus releasing HCl again, and the C atoms in PVC-CuO system could react with copper chloride salts and H 2 O, to form and release HCl. The capture effects of chlorine by Fe 2 O 3 and Al 2 O 3 were not good. With addition of MO x , all De-Cl PVCs were rich in C=C-H and (C) 3 C-H structures. Fe 2 O 3 , MgO and CuO reduced the release of volatile hydrocarbons, while CaO, ZnO and Al 2 O 3 increased the release of volatile hydrocarbons. Except for CaO and CuO, the other MO x increased the amount of residual hydrocarbon (De-Cl PVC).
危险品化学品经营许可证（带存储）