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首页> 外文期刊>Environmental Science & Technology >The Regular/Persistent Free Radicals and Associated Reaction Mechanism for the Degradation of 1,2,4-Trichlorobenzene over Different MnO_2 Polymorphs
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The Regular/Persistent Free Radicals and Associated Reaction Mechanism for the Degradation of 1,2,4-Trichlorobenzene over Different MnO_2 Polymorphs

机译：不同MnO_2多晶型物降解1,2,4-三氯苯的规则/持久自由基及相关的反应机理

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摘要

The role of regular/persistent free radicals on the catalytic activity of K+-tuned MnO2 tunnel structures is poorly understood to date. Herein, three MnO2 polymorphs (alpha-, beta-, and delta-MnO2) were synthesized and examined toward the degradation of 1,2,4-trichlorobenzene (1,2,4-TrCBz) at 300 degrees C. delta-MnO2, with a two-dimensional-layered tunnel structure tuned by K+, exhibited the highest activity among the three MnO2 polymorphs. The electron spin resonance spectroscopy results confirmed that delta-MnO2 featured the most abundant reactive oxygen species (ROS: O-2(-center dot), center dot OH, and O-1(2)), followed by alpha-MnO2 (O-2(-center dot) and O-1(2)), and beta-MnO2 (O-2(-center dot)), being supported by the calculated energy barrier. It was, intriguingly, noted that persistent organic free radicals, newly recognized as emerging surface-stabilized compound, were remarkably detected in alpha- and beta-MnO2/1,2,4-TrCBz systems but not in more reactive delta-MnO2/1,2,4-TrCBz system. These might contribute to discrepant oxidative degradation process. During the oxidative process, intermediates, including benzoic acid and glycerol, formed via attack by ROS. Upon further attack, these intermediates fragmented into smaller molecules such as formic, acetic, propionic, and butyric acids. The present findings give deeper insights into the role of free radicals on the catalytic degradation of chlorinated aromatics.
机译：迄今为止，对规则/持久性自由基在K +调节的MnO2隧道结构的催化活性中的作用知之甚少。在此，合成了三种MnO2多晶型物（α-，β-和δ-MnO2），并研究了其在300摄氏度下对1,2,4-三氯苯（1,2,4-TrCBz）的降解， K +调谐的二维层状隧道结构在三个MnO2多晶型物中表现出最高的活性。电子自旋共振谱结果证实，δ-MnO2具有最丰富的活性氧种类（ROS：O-2（中心点），中心点OH和O-1（2）），其次是α-MnO2（O -2（中心点）和O-1（2））和β-MnO2（O-2（中心点））受计算的能垒支持。有趣的是，新发现的持久稳定的有机自由基被认为是新兴的表面稳定化合物，在α-和β-MnO2/ 1,2,4-TrCBz系统中得到了显着检测，而在反应性更强的δ-MnO2/ 1中则未检测到。 ，2,4-TrCBz系统。这些可能导致差异的氧化降解过程。在氧化过程中，中间体（包括苯甲酸和甘油）通过ROS的侵蚀而形成。经过进一步的攻击，这些中间体会破碎成较小的分子，例如甲酸，乙酸，丙酸和丁酸。目前的发现为自由基在氯化芳烃催化降解中的作用提供了更深入的见解。

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  • 来源
    《Environmental Science & Technology》 |2018年第22期|13351-13360|共10页
  • 作者

    Li Qianqian; Huang Xinchen; Su Guijin; Zheng Minghui; Huang Chunhua; Wang Mengjing; Ma Chunyan; Wei Da;

  • 作者单位

    Chinese Acad Sci, State Key Lab Environm Chem & Ecotoxicol, Res Ctr Ecoenvironm Sci, POB 2871, Beijing 100085, Peoples R China;

    Chinese Acad Sci, Key Lab Environm Nanotechnol & Hlth Effects, Res Ctr Ecoenvironm Sci, POB 2871, Beijing 100085, Peoples R China;

    Univ Chinese Acad Sci, Beijing 100049, Peoples R China;

    Nanyang Technol Univ, Sch Civil & Environm Engn, 50 Nanyang Ave, Singapore 639789, Singapore;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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