Uptake of isoprene, methacrylic acid and methyl methacrylate into aqueous solutions of sulfuric acid and hydrogen peroxide.
Uptake of isoprene, methacrylic acid and methyl methacrylate into aqueous solutions of sulfuric acid and hydrogen peroxide.
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DOI：
10.1016/s1001-0742(11)61034-6
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发表时间：
2012-11
影响因子：
6.9
通讯作者：
Ze Liu;Maofa Ge;Weigang Wang
中科院分区：
文献类型：
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作者：
Ze Liu;Maofa Ge;Weigang Wang
多相酸催化过氧化氢氧化被认为是异戊二烯及其气相氧化产物形成二次有机气溶胶的潜在途径，但缺乏动力学数据严重限制了对该过程在大气中的评价。在这里，我们报告了异戊二烯，甲基丙烯酸和甲基丙烯酸甲酯进入硫酸和过氧化氢水溶液的第一次测量。异戊二烯由于其高挥发性和低溶解度而不易分解到溶液中，这阻碍了其进一步的液相氧化。甲基丙烯酸和甲基丙烯酸甲酯均可进入溶液并被过氧化氢氧化，当溶液酸度分别在30 wt.%和70 wt.%以上时，观察到稳态吸收。在相同酸度的溶液中，甲基丙烯酸的稳态吸收系数远大于甲基丙烯酸甲酯。这些观察结果可以用这两种化合物的不同反应活性来解释，这是由羧基和酯基之间不同的吸电子偶联引起的。根据计算的稳态吸收系数估算大气寿命。这些结果表明，甲基丙烯酸的多相酸催化氧化在二次有机气溶胶形成中起作用，但对于异戊二烯和甲基丙烯酸甲酯，这一过程在对流层中并不重要。
Multiphase acid-catalyzed oxidation by hydrogen peroxide has been suggested to be a potential route to secondary organic aerosol formation from isoprene and its gas-phase oxidation products, but the lack of kinetics data significantly limited the evaluation of this process in the atmosphere. Here we report the first measurement of the uptake of isoprene, methacrylic acid and methyl methacrylate into aqueous solutions of sulfuric acid and hydrogen peroxide. Isoprene cannot readily partition into the solution because of its high volatility and low solubility, which hinders its further liquid-phase oxidation. Both methacrylic acid and methyl methacrylate can enter the solutions and be oxidized by hydrogen peroxide, and steady-state uptake was observed with the acidity of solution above 30 wt.% and 70 wt.%, respectively. The steady-state uptake coefficient of methacrylic acid is much larger than that of methyl methacrylate for a solution with same acidity. These observations can be explained by the different reactivity of these two compounds caused by the different electron-withdrawing conjugation between carboxyl and ester groups. The atmospheric lifetimes were estimated based on the calculated steady-state uptake coefficients. These results demonstrate that the multiphase acid-catalyzed oxidation of methacrylic acid plays a role in secondary organic aerosol formation, but for isoprene and methyl methacrylate, this process is not important in the troposphere.