Mechanism and direct kinetics study on the homogeneous gas-phase formation of PBDD/Fs from 2-BP, 2,4-DBP, and 2,4,6-TBP as precursors.
Mechanism and direct kinetics study on the homogeneous gas-phase formation of PBDD/Fs from 2-BP, 2,4-DBP, and 2,4,6-TBP as precursors.
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DOI：
10.1021/es103536t
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发表时间：
2011-02
影响因子：
11.4
通讯作者：
Wanni Yu;Jingtian Hu;Fei Xu;Xiaoyan Sun;R. Gao;Qingzhu Zhang;Wen-xing Wang
中科院分区：
文献类型：
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作者：
Wanni Yu;Jingtian Hu;Fei Xu;Xiaoyan Sun;R. Gao;Qingzhu Zhang;Wen-xing Wang
本研究研究了以2- bp、2,4- dbp和2,4,6- tbp为前体的多溴化二苯并-对二恶英/二苯并呋喃（PBDD/Fs）的均相气相形成。首先，对形成机理进行了密度泛函理论（DFT）计算。在MPWB1K/6-31+G（d,p）水平上计算了平稳点的几何形状和频率，并采用MPWB1K/6-311+G（3df,2p）方法进一步细化了能量参数。然后，将PBDD/F的形成机理与2- cp、2,4- dcp和2,4,6- tcp为前驱体的PCDD/F形成机理进行了比较。最后，在600 ~ 1200 K的宽温度范围内，用正则变分过渡态（CVT）理论和小曲率隧穿（SCT）修正计算了关键元素反应的速率常数。目前的结果表明，只有邻位有溴的bp才能形成pbdd。这项研究，连同我们小组已经发表的作品，清楚地表明bp比类似的cp更容易形成二恶英。多溴取代抑制PBDD/F生成。
This study investigated the homogeneous gas-phase formation of polybrominated dibenzo-p-dioxin/dibenzofurans (PBDD/Fs) from 2-BP, 2,4-DBP, and 2,4,6-TBP as precursors. First, density functional theory (DFT) calculations were carried out for the formation mechanism. The geometries and frequencies of the stationary points were calculated at the MPWB1K/6-31+G(d,p) level, and the energetic parameters were further refined by the MPWB1K/6-311+G(3df,2p) method. Then, the formation mechanism of PBDD/Fs was compared and contrasted with the PCDD/F formation mechanism from 2-CP, 2,4-DCP, and 2,4,6-TCP as precursors. Finally, the rate constants of the crucial elementary reactions were evaluated by the canonical variational transition-state (CVT) theory with the small curvature tunneling (SCT) correction over a wide temperature range of 600-1200 K. Present results indicate that only BPs with bromine at the ortho position are capable of forming PBDDs. The study, together with works already published from our group, clearly shows an increased propensity for the dioxin formations from BPs over the analogous CPs. Multibromine substitutions suppress the PBDD/F formations.