The Atmospheric Oxidation Mechanism of o-Xylene Initiated by Hydroxyl Radicals
The Atmospheric Oxidation Mechanism of o-Xylene Initiated by Hydroxyl Radicals
复制标题
羟基自由基引发邻二甲苯的大气氧化机理
DOI：
10.3866/pku.whxb201510152
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
王黎明
中科院分区：
文献类型：
--
作者：
Pan Shanshan;王黎明
采用量子化学、过渡态理论和单分子理论（RRKMME）方法研究了羟基（OH）自由基引发邻二甲苯（oX）大气氧化反应机理，在M06-2X/6-311++G（2df，2 p）水平上优化了反应物、过渡态和产物的分子结构，在ROCBS上计算电子能量-采用经典的过渡态理论计算了各步反应的速率和速率常数，并计算了各步反应的支化比在常压下，邻二甲苯的氧化反应主要是OH在C_1和C_3位的加成反应，生成加合物oX-1-OH（R1）和oX-3-OH（R3），R1和R3与O_2的反应可以通过不可逆的去氢反应生成二甲酚（仅R3），双环过氧自由基（BPR）与大气中的NO和/或HO_2反应，生成有机硝酸酯、氢过氧化物（ROOH）和双环烷氧基自由基（BAR），并最终转化为双乙酰、丁烯二醛、甲基乙二醛、4-氧代-2-戊烯醛、根据目前的理论预测和实验测量结果，提出了一种新的OX在大气中的氧化机理，并将高NO条件下的预测产物产率与以前的实验测量结果进行了比较。并讨论了
The atmospheric oxidation mechanism of o-xylene(oX) initiated by hydroxyl(OH) radicals has been investigated by using quantum chemistry,transition state theory,and unimolecular theory(RRKMME) calculations.Molecular structures of reactants,transition states,and products are optimized at M06-2X/6-311++G(2df,2p) level,and the electronic energies are calculated at the ROCBS-QB3 level.The classical transition state theory is employed to predict the rates or rate constants for all the reaction steps as well as the branching ratios of the reaction pathways.RRKM-ME calculations are employed to explore the pressure-dependence of the reaction kinetics.Under atmospheric conditions,the oxidation of o-xylene is dominated by OH addition to the C_1 and C_3 positions,forming adducts oX-1-OH(R1) and oX-3-OH(R3),which will readily react with atmospheric oxygen.The reactions of R1 and R3 with O_2 can proceed by irreversible H-abstraction to dimethylphenols(R3 only),or by reversible addition to form bicyclic radicals,which recombine with atmospheric oxygen to form bicyclic peroxy radicals(BPRs).BPRs will react with NO and/or HO_2 in the atmosphere,forming organonitrate,hydroperoxides(ROOH),and bicyclic alkoxy radicals(BARs),of which the BARs eventually transfer to the final products,including biacetyl,butenedial,methylglyoxal,4-oxo-2-pentenal,epoxy-2,3-butenedial,and a small amount of glyoxal.The products ROOH and methylglyoxal are considered to contribute to the formation of secondary organic aerosols.A new oxidation mechanism of oX in the atmosphere is proposed,based on the current theoretical predictions and previous experimental measurements,and the predicted product yields under high NO conditions are compared with previous experimental measurements.The effect of temperature on the oxidation mechanism is also discussed.