PVC产品在热化学过程中氯化石蜡的排放特征及转化机制研究

Short-chain chlorinated paraffins (SCCPs) have been listed as a Persistent Organic Pollutant (POP) in Annex A by the Stockholm Convention in 2017. The Chinese ministry of environmental protection also listed SCCPs as the first batch of priority controlled chemicals. As the main carrier of chlorinated paraffin (CPs), polyvinyl chloride (PVC) products may encounter thermal chemical processes during the whole life cycle stages. However, the emission and transformation of CPs during this process are still unclear. In this project, the quantitative analysis methods of CPs are optimized and developed firstly. Extensive sampling is conducted in order to grasp the occurrence and distribution of CPs in PVC products in China. Based on the above works, laboratory experiments are carried out to investigate the emission levels and characteristics of CPs from typical PVC products during thermochemical processes. The transformation mechanism of CPs as well as the synergetic formation, emission and regulation principles of chlorinated aromatic hydrocarbons is also studied. We also investigate the catalytic mechanism of the metal compounds on CPs in PVC products during thermochemical processes. Efficient catalytic method is explored so as to control the synergetic emission of CPs and chlorinated aromatic hydrocarbons. The results of this project will help to understand the emission characteristic and transformation mechanism of CPs during thermochemical processes and provide data supporting the improvement of the emission inventory of CPs in China. Furthermore, the results are of great significance for the implementation of the Stockholm convention and pollutant emission control.

短链氯化石蜡（SCCPs）已被列入《斯德哥尔摩公约》附件A清单以及我国的第一批优先控制化学品名录。作为氯化石蜡（CPs）的主要载体，聚氯乙烯（PVC）产品在生命周期可能遭遇热化学过程，而该过程中CPs的排放及转化尚不清楚。本项目拟采用实验室模拟与现场采样相结合的方法，通过优化并发展CPs的准确定量分析方法，初步掌握我国PVC产品中CPs的赋存与分布情况。在此基础上系统地开展典型PVC产品在不同热化学过程中CPs的排放水平与排放特征研究，探究CPs在热反应中的转化机理及其与氯代芳香烃生成、释放的协同效应和调控原理。研究PVC产品在热化学过程中金属催化物对CPs的催化转化机制，探索高效催化方法协同控制CPs及氯代芳香烃的排放。本研究结果有助于揭示典型PVC产品在热化学过程中CPs的排放特征与转化机制，能够为完善我国SCCPs的排放清单提供技术支撑，同时对我国履行公约和减排工作具有重要意义。

短链氯化石蜡（SCCPs）作为一类新型受控持久性污染物（POPs），其环境来源尚不清楚。本项目研究氯化石蜡（CPs）在PVC制品中的赋存特征，并开展不同热化学过程中CPs的释放及转化机理研究。主要研究内容和结果如下：.（1）CP52的分解的活化能（~81kJ/mol）要低于CP70（~88-127kJ/mol），两者的反应动力学机理均符合随机成核和随后生长模型函数。CP-52及CP-70分解会导致SCCPs及MCCPs的显著释放，随温度升高CPs逐步从固相迁移至气相。在释放速率加快的同时，CPs的分解也在增强，并在气相中生成高浓度的1-2氯取代氯代芳烃。密度泛函（DFT）计算表明，苯自由基与氯苯（CBz）是气相反应过程中多氯联苯（PCBs）及多氯萘（PCNs）的重要反应物。.（2）采集了湖北武汉地区不同PVC制品。优化并建立了基于LC-MS的样品前处理技术和仪器分析方法，实现了PVC制品中短、中、长链CPs的准确定量。研究发现，所采集PVC制品中CPs的检出率超过96%，总体上CPs的含量∑MCCPs>∑SCCPs>∑LCCPs，说明PVC中主要源于CP-52的添加。∑SCCPs、∑MCCPs及∑LCCPs的浓度范围分别为0.28-52864μg/g、5.52-785933μg/g及0.0047-7288μg/g，表明PVC制品在使用和回收过程中，可能是环境中CPs的重要来源之一。.（3）研究了废弃电缆线在不同焚烧过程中CPs的释放及转化。结果发现，温度是影响CPs释放的最重要因素。固相中CPs的浓度随温度呈下降趋势，而气相浓度则持续升高，并在400℃时达到浓度峰值，分别为433μg/g，369μg/g，316μg/g。CPs在释放到气相的过程中存在明显的分解，且氧气能加速CPs分解。Fe3O4有利于长链CPs的生成，在铜类化合物中，CuO对CPs分解的催化活性最弱。铜化合物对芳香烃及氯代芳香烃生成的催化作用要显著强于铁化合物，CuCl2、CuO和Cu2O催化生成CBz、PCNs、PCBs和PCDD/Fs均以4氯取代以上的高氯代单体为主。.本研究成果有助于较为全面地了解我国PVC产品在生命周期中的环境效应，为完善我国CPs的排放清单提供理论支持，同时为我国履行POPs公约和后续的污染物协同减排及防治工作提供科学依据。