二次反应最小条件下聚氯乙烯塑料脱氯过程的实验

Experiment of polyvinyl chloride plastic dechlorination process under condition of minimum secondary reaction

采用金属网反应器对PVC热解过程中温度范围300～800℃、升温速率1～1000 K·s^-1、停留时间0～120 s的热解气体释放特性开展了实验研究。并基于EPA-26A标准对热解气中HCl和Cl2进行了检测。结果显示，HCl和 Cl2的产率均随着温度的升高、停留时间的增长而有所提高。降低升温速率能够提升气态产物总体产率但没有改变含氯气体的总体分布。热解实验中气态产物均以HCl为主，并伴随有少量的Cl2生成；该结果也证实了在PVC热解脱氯过程中大量含氯自由基的存在，进一步证实了PVC热解过程遵循的是自由基链反应机理。此外，通过对PVC 热解焦样的分析进一步发现 PVC 热解第一阶段链反应终止时的分子更接近于直链多烯烃结构而非聚合环状结构，环化反应在该阶段并未发生。

Pyrolysis experiments of polyvinylchloride （PVC） were performed using a wire-mesh reactor. Non-condensing gases were collected at a heating rate 1-1000 K·s^-1 with temperatures from 300℃ to 800℃ and a holding time from 0 to 120 s. EPA-method 26A was employed to determinate the concentrations of both Cl2 and HCl. The results showed that the release of HCl and Cl2 increased continually with increase of temperature and reaction time. Lower heating rate could make the total gas yield increase but do not change the chlorine distribution. Cl2 seemed as an accompanied product during HCl release, which indicated that a bunch of free Cl radicals were involved in PVC thermal degradation. The results confirmed that the pyrolysis process of PVC plastic followed the free radical chain mechanism. Lastly, it was further indicated, by the analysis of PVC pyrolysis tar, that the products obtained at the first stage of PVC pyrolysis were straight-chain polyenes rather than ring structure compounds,i.e. occurring of cyclization reactions seemed impossible at the phase.