Wikström Evalena, Ryan Shawn, Touati Abderrahmane, Gullett Brian K
National Risk Management Research Laboratory, Air Pollution Prevention and Control Division, Air Pollution Technology Branch, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA.
Environ Sci Technol. 2004 Apr 1;38(7):2097-101. doi: 10.1021/es034564p.
The aim of this study was to investigate the role of in situ formed soot deposits generated during a combustion process for the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/Fs). In situ formed soot deposits were generated in an entrained flow reactor by using a sooting methane (CH4) flame (sooting phase), with or without chlorine doped into the flame, and fly ash added into the gas phase. The presence of fly ash in the soot deposit was found to be critical, as a catalyst for formation and/or a chlorinating agent. The presence of chlorinated aromatic structures in the soot matrix was not enough to promote de novo formation of PCDDs/Fs without the presence of fly ash. PCDFs were formed via direct release of the molecule backbone structure from the soot. PCDDs were formed via a similar mechanism as well as an equally important formation pathway of condensation reactions of C6 compounds. The formation rate of the soot/ash depositwas still at half its original activity 34 h after the deposits were formed, suggesting a persistent de novo formation occurring for a long time after the sooting incidences (memory effect).
本研究的目的是调查燃烧过程中生成的原位烟灰沉积物在多氯代二苯并 - 对 - 二噁英和二苯并呋喃（PCDDs/Fs）形成过程中的作用。通过使用含碳的甲烷（CH₄）火焰（积碳阶段），在夹带流反应器中生成原位烟灰沉积物，火焰中可掺杂或不掺杂氯，并向气相中添加飞灰。发现烟灰沉积物中飞灰的存在至关重要，它可作为生成的催化剂和/或氯化剂。在没有飞灰的情况下，烟灰基质中氯化芳族结构的存在不足以促进PCDDs/Fs的从头生成。多氯代二苯并呋喃是通过从烟灰中直接释放分子主链结构形成的。多氯代二苯并二噁英是通过类似机制以及C6化合物缩合反应这一同样重要的生成途径形成的。烟灰/灰沉积物形成34小时后，其生成速率仍为原始活性的一半，这表明在积碳事件发生后很长一段时间内持续存在从头生成现象（记忆效应）。
