Synergistic effect of mixed Cu and Fe oxides and chlorides on electrophilic chlorination of dibenzo-p-dioxin and dibenzofuran
Synergistic effect of mixed Cu and Fe oxides and chlorides on electrophilic chlorination of dibenzo-p-dioxin and dibenzofuran
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混合铜铁氧化物和氯化物对二苯并对二恶英和二苯并呋喃亲电氯化的协同作用
DOI：
10.1016/j.scitotenv.2020.137563
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发表时间：
2020
影响因子：
9.8
通讯作者：
Chen Jiping
中科院分区：
文献类型：
--
作者：
Wang Dan;Zhang Haijun;Fan Yun;Cao Rong;Gao Yuan;Chen Jiping
二苯并二恶英（DD）和二苯并呋喃（DF）的直接氯化是燃烧烟气中二恶英的重要来源。氯化反应主要通过铜、铁氯化物诱导的亲电取代反应进行，铜、铁氯化物必须以混合状态共存于颗粒物上。为探索真实的燃烧烟气中DD/DF氯化反应机理，制备了8种CuO/Fe 2 O3/CuCl 2/FeCl 3/SiO2复合材料，模拟燃烧烟气中Cu和Fe物种的共存状态。铜、铁氧化物和氯化物的混合物对DD/DF的亲电氯化反应有显著的协同作用。在250 °C下，含Cu和Fe物种的复合材料的DD/DF氯化效率比仅含Fe物种的复合材料高1-2个数量级。CuCl 2物种是亲电氯化反应的高活性中心。FeCl 3作为一种优良的促进剂，对DD/DF氯化反应的促进作用优于CuCl 2。Cu和Fe氧化物的比例升高也有利于亲电氯化。与DF相比，DD更容易被氯化。氯取代主要发生在DD和DF的2、3、7和8位。并对DD/DF亲电氯化协同效应的可能机理进行了推测。
The direct chlorination of dibenzo-p-dioxin (DD) and dibenzofuran (DF) is an important source of dioxins in combustion flue gas. The chlorination reaction mainly occurs via electrophilic substitution induced by Cu and Fe chlorides, which must cohabit on particulate matters in mixed state. To explore the mechanism for DD/DF chlorination in real combustions flue gas, 8 kinds of CuO/Fe2O3/CuCl2/FeCl3composites impregnated onto silica powder were prepared to simulate the coexisting state of Cu and Fe species in combustion flue gas. Mixed Cu and Fe oxides and chlorides induced a significant synergistic effect on electrophilic chlorination of DD/DF. The efficiencies of DD/DF chlorination over composites containing both Cu and Fe species were 1–2 orders of magnitude higher than those over composites containing only Fe species at 250 °C. CuCl2species were highly active sites for electrophilic chlorination. FeCl3acted as an excellent promoter to accelerate DD/DF chlorination over CuCl2species. The elevated proportion of Cu and Fe oxides was also favora ble for electrophilic chlorination. Compared with DF, DD was more prone to be chlorinated. Chlorine substitution primarily occurred at 2, 3, 7 and 8 positions of DD and DF. Furthermore, the possible mechanism for synergistic effect on electrophilic chlorination of DD/DF was speculated.