Zhang Tianlei, Wen Mingjie, Zeng Zhaopeng, Lu Yousong, Wang Yan, Wang Wei, Shao Xianzhao, Wang Zhiyin, Makroni Lily
Shaanxi Key Laboratory of Catalysis, School of Chemical & Environment Science, Shaanxi University of Technology Hanzhong Shaanxi 723001 P. R. China
Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University Shanghai 200433 P. R. China.
RSC Adv. 2020 Mar 2;10(15):9093-9102. doi: 10.1039/d0ra00024h. eCollection 2020 Feb 27.
The HO + HO → HO + HO reaction is an important reservoir for both radicals of HO and HO catalyzing the destruction of O. Here, this reaction assisted by NH and HCOOH catalysts was explored using the CCSD(T)-F12a/cc-pVDZ-F12//M06-2X/aug-cc-pVTZ method and canonical variational transition state theory with small curvature tunneling. Two possible sets of mechanisms, (i) one-step routes and (ii) stepwise processes, are possible. Our results show that in the presence of both NH and HCOOH catalysts under relevant atmospheric temperature, mechanism (i) is favored both energetically and kinetically than the corresponding mechanism (ii). At 298 K, the relative rate for mechanism (i) in the presence of NH (10, 2900 ppbv) and HCOOH (10 ppbv) is respectively 3-5 and 2-4 orders of magnitude lower than that of the water-catalyzed reaction. This is due to a comparatively lower concentration of NH and HCOOH than HO which indicates the positive water effect under atmospheric conditions. Although NH and HCOOH catalysts play a negligible role in the reservoir for both radicals of HO and HO catalyzing the destruction of O, the current study provides a comprehensive example of how acidic and basic catalysts assisted the gas-phase reactions.
HO + HO → HO + HO反应是HO和HO两种自由基催化O破坏的重要储存途径。在此，使用CCSD(T)-F12a/cc-pVDZ-F12//M06-2X/aug-cc-pVTZ方法和具有小曲率隧道效应的正则变分过渡态理论，探索了由NH和HCOOH催化剂辅助的该反应。存在两种可能的反应机理：（i）一步反应路径和（ii）分步反应过程。我们的结果表明，在相关大气温度下，同时存在NH和HCOOH催化剂时，机理（i）在能量和动力学上均比相应的机理（ii）更有利。在298 K时，在存在NH（10、2900 ppbv）和HCOOH（10 ppbv）的情况下，机理（i）的相对速率分别比水催化反应低3-5个和2-4个数量级。这是由于NH和HCOOH的浓度比HO相对较低，这表明了大气条件下的正水效应。尽管NH和HCOOH催化剂在HO和HO两种自由基催化O破坏的储存途径中作用可忽略不计，但本研究提供了一个酸性和碱性催化剂如何辅助气相反应的全面示例。
