Mechanism and Direct Kinetic Study of the Polychlorinated Dibenzo-p-dioxin and Dibenzofuran Formations from the Radical/Radical Cross-Condensation of 2,4-Dichlorophenoxy with 2-Chlorophenoxy an

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• 作者：Fei Xu ; Wanni Yu ; Qin Zhou ; Rui Gao ; Xiaoyan Sun ; Qingzhu Zhang ; Wenxing Wang
• 刊名：Environmental Science & Technology
• 出版年：2011
• 出版时间：January 15, 2011
• 年：2011
• 卷：45
• 期：2
• 页码：643-650
• 全文大小：390K
• 年卷期：v.45,no.2(January 15, 2011)
• ISSN：1520-5851

文摘

A direct density functional theory (DFT) kinetic calculation is carried out for the homogeneous gas-phase formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from the cross-condensation of 2,4-dichlorophenoxy radical (2,4-DCPR) with 2-chlorophenoxy radical (2-CPR) and 2,4,6-trichlorophenoxy radical (2,4,6-TCPR). The possible formation mechanism is investigated and compared with the PCDD/F formation mechanism from the self-condensation of 2,4-DCPR, 2-CPR, and 2,4,6-TCPR. The rate constants and their temperature dependence of the crucial elementary reactions are computed by the canonical variational transition-state theory with the small curvature tunneling contribution over the temperature range of 600鈭?200 K. This study shows that the multichlorine substitutions suppress the PCDD/F formations. Because of a lack of experimental kinetic data, the present theoretical results are expected to be useful and reasonable to estimate the kinetic properties, such as the pre-exponential factors, the activation energies, and the rate constants, of the elementary reactions involved in the formation of PCDD/Fs.