Study On The Pyrolysis Of Polyvinyl Chloride And Iron Oxide

A novel de-chlorination method removing chlorine from polyvinyl chloride(PVC)by using iron oxide(Fe2O3)is suggested in this study aiming to recycle waste plastics containing chlorine in a clean,profitable way friendly to the environment.Based on the comprehensive understanding about the co-pyrolysis process mechanism of Fe2O3 and PVC.investigated in this study,appropriate conditions suitable for de-chlorination are proposed and the solid residue after de-chlorination are tested the reactivity for the possibility of making iron.The parameters controlled are mixing ratio of Fe2O3 to PVC,temperature,holding time,heating rate and the types of Fe2O3&PVC.The main results can be summarized as the following.(1)During the co-pyrolysis of pure Fe2O3 and PVC,in addition to the decomposition of PVC,Fe2O3 participates in reactions as well.The reaction products are influenced significantly by the mixing ratio of Fe2O3 to PVC and temperature,whereas increasing heating rate only results in the shift of temperature zone reactions occur to higher ranges.(ⅰ)From room temperature to 673 K,the decomposition of PVC releases HCl and polyene meanwhile Fe2O3 is chlorinated to FeCl2.In the samples of Fe2O3 content greater than 39%,Fe2O3 is excess to PVC and part of which is reduced to Fe3O4;(ⅱ)From 673 K to 793 K,further decomposition of polyene occurs resulting in hydrogen and carbon mainly so that FeCl2 starts to be reduced to Fe together with the reduction of Fe3O4 to Fe;(ⅲ)From 793 K to 1673 K,in the samples of large Fe2O3 content(Fe2O3wt.%>39%),the left Fe3O4 is reduced by carbon gradually to FeO first and then Fe,even Fe3C.(2)The suitable temperatures for de-chlorination of PVC by using Fe2O3 are below 673 K.Increasing temperature,Fe2O3 content in the mixtures and holding time favors the de-chlorination,especially temperature and Fe2O3 content in the mixtures show a much significant impact on the de-chlorination process than holding time.(3)The properties of Fe2O3 exhibits a large influence on the de-chlorination process.An improved coverage of Fe2O3 powders on the surface of PVC favors the formation of FeCl2(4)The solid residue after de-chlorination of Fe2O3 and PVC mixtures is composed of polyene,iron oxide and unreacted impurities from the raw materials such as SiO2.When heated to higher temperatures,polyene decomposes and iron oxide is reduced to metal Fe.