甲苯,挥发性有机化合物(VOC)的重要成员,对人类生活和环境产生重大不利影响。在高级氧化工艺的背景下,·OH自由基作为高效氧化剂出现,对消除VOCs至关重要。本研究采用计算量子化学方法(G4MP2//B3LYP/6-311++G(d,p))在隐式溶剂模型中系统地研究·OH自由基对甲苯的降解,并验证了使用T1诊断选择单参考方法的基本原理。我们的结果表明,用·OH氧化甲苯的三种可能的反应机理:首先,苯环进行夺氢反应,然后与·OH直接结合形成甲酚;其次,·OH直接添加到苯环,导致戒指打开;第三,将侧链氧化为苯甲酸,然后进一步加成和开环。最后两种氧化途径涉及通过添加·OH使甲苯开环,大大促进了这个过程。因此,这两种途径都被认为是可行的降解甲苯。随后,设计了UV-H2O2体系以诱导·OH的形成以降解甲苯并确定最佳反应条件。证明·OH和1O2是降解甲苯的主要活性物质,他们的贡献排名为·OH>1O2。反应后的混合溶液中的中间体使用GC-MS进行表征,证明了理论预测的有效性。甲苯消耗率的比较研究表明,实验综合活化能为10.33kJ/mol,这与通过对这三种机理的理论分析获得的初步活化能(0.56kJ/mol至13.66kJ/mol)一致,说明该理论方法可为·OH氧化甲苯的实验研究提供理论依据。
Toluene, a prominent member of volatile organic compounds (VOCs), exerts a substantial adverse influence on both human life and the environment. In the context of advanced oxidation processes, the ·OH radical emerges as a highly efficient oxidant, pivotal in the elimination of VOCs. This
study employs computational quantum chemistry methods (G4MP2//B3LYP/6-311++G(d,p)) to systematically investigate the degradation of toluene by ·OH radicals in an implicit solvent model, and validates the rationale of choosing a single-reference method using T1 diagnostics. Our results suggest three possible reaction mechanisms for the oxidation of toluene by ·OH: firstly, the phenyl ring undergoes a hydrogen abstraction reaction followed by direct combination with ·OH to form cresol; secondly, ·OH directly adds to the phenyl ring, leading to ring opening; thirdly, oxidation of sidechain to benzoic acid followed by further addition and ring opening. The last two oxidation pathways involve the ring opening of toluene via the addition of ·OH, significantly facilitating the process. Therefore, both pathways are considered feasible for the degradation of toluene. Subsequently, the UV-H2O2 system was designed to induce the formation of ·OH for toluene degradation and to identify the optimal reaction conditions. It was demonstrated that ·OH and 1O2 are the primary active species for degrading toluene, with their contribution ranking as ·OH > 1O2. The intermediates in the mixture solution after reactions were characterized using GC-MS, demonstrating the validity of theoretical predictions. A comparative
study of the toluene consumption rate revealed an experimental comprehensive activation energy of 10.33 kJ/mol, which is consistent with the preliminary activation energies obtained via theoretical analysis of these three mechanisms (0.56 kJ/mol to 13.66 kJ/mol), indicating that this theoretical method can provide a theoretical basis for experimental studies on the oxidation of toluene by ·OH.