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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Reaction Mechanism of Photocatalytic Degradation of Chlorinated Ethylenes on Porous TiO_2 Pellets: Cl Radical-Initiated Mechanism
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Reaction Mechanism of Photocatalytic Degradation of Chlorinated Ethylenes on Porous TiO_2 Pellets: Cl Radical-Initiated Mechanism

机译：多孔TiO_2微球上光催化降解氯乙烯的反应机理：Cl自由基引发机理

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摘要

The photoassisted catalytic degradation of chloroethylene was studied in a tubular photoreactor packed with TiO_2 pellets prepared by a sol-gel method. The experiments were performed in a noncirculating mode. Kinetic data and the reaction products were compared with those for the photodegradation of ethylene, trichloroethylene, and tetrachloroethylene. The theoretical calculations at the MP4/6-31G**//B3LYP/6-31G** level indicated that the addition of OH radicals to chlorinated ethylenes is more exothermic than that of Cl radicals by 14.6-29.5 kcal mol~(-1). Examination of Cl mass balance indicated that the concentration of Cl~- collected from the TiO_2 surface was higher than that from the product gas stream. When the photodegradation of ethylene was performed on the TiO_2 pellets which had been used for that of TCE or which were pretreated with HCl, the formation of chloroacetaldehyde was confirmed by the GC/MS. We proposed that during the photodegradation of the chlorinated ethylenes, the Cl~-, as one of the reaction products, accumulated and was oxidized to Cl radical on the TiO_2 surface, which might be due to the oxidation by OH radical. Then, the Cl radical reacted with chlorinated ethylenes, leading to the formation of undesirable chlorinated byproducts.
机译：在装有溶胶-凝胶法制备的TiO_2颗粒的管状光反应器中研究了氯乙烯的光辅助催化降解。实验以非循环模式进行。将动力学数据和反应产物与乙烯，三氯乙烯和四氯乙烯的光降解反应进行了比较。在MP4 / 6-31G ** // B3LYP / 6-31G **水平上的理论计算表明，在14.6-29.5 kcal mol〜（-1）下，向氯化乙烯中添加OH自由基比向Cl自由基放热更多。 ）。 Cl质量平衡的检验表明，从TiO_2表面收集的Cl〜-的浓度高于从产物气流中收集的Cl〜-的浓度。当对用于TCE的TiO_2颗粒或用HCl预处理的TiO_2颗粒进行乙烯的光降解时，通过GC / MS确认了氯乙醛的形成。我们提出，在氯化乙烯的光降解过程中，作为反应产物之一的Cl〜-积累并被氧化为TiO_2表面的Cl自由基，这可能是由于OH自由基的氧化所致。然后，Cl自由基与氯化乙烯反应，导致形成不良的氯化副产物。

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