Eskola Arkke J, Antonov Ivan O, Sheps Leonid, Savee John D, Osborn David L, Taatjes Craig A
Combustion Research Facility, Sandia National Laboratories, 7011 East Avenue, MS 9055, Livermore, California 94551, USA.
Phys Chem Chem Phys. 2017 May 31;19(21):13731-13745. doi: 10.1039/c7cp01366c.
Product formation, in particular ketohydroperoxide formation and decomposition, were investigated in time-resolved, Cl-atom initiated neopentane oxidation experiments in the temperature range 550-675 K using a photoionization time-of-flight mass spectrometer. Ionization light was provided either by Advanced Light Source tunable synchrotron radiation or ∼10.2 eV fixed energy radiation from a H-discharge lamp. Experiments were performed both at 1-2 atm pressure using a high-pressure reactor and also at ∼9 Torr pressure employing a low-pressure reactor for comparison. Because of the highly symmetric structure of neopentane, ketohydroperoxide signal can be attributed to a 3-hydroperoxy-2,2-dimethylpropanal isomer, i.e. from a γ-ketohydroperoxide (γ-KHP). The photoionization spectra of the γ-KHP measured at low- and high pressures and varying oxygen concentrations agree well with each other, further supporting they originate from the single isomer. Measurements performed in this work also suggest that the "Korcek" mechanism may play an important role in the decomposition of 3-hydroperoxy-2,2-dimethylpropanal, especially at lower temperatures. However, at higher temperatures where γ-KHP decomposition to hydroxyl radical and oxy-radical dominates, oxidation of the oxy-radical yields a new important channel leading to acetone, carbon monoxide, and OH radical. Starting from the initial neopentyl + O reaction, this channel releases altogether three OH radicals. A strongly temperature-dependent reaction product is observed at m/z = 100, likely attributable to 2,2-dimethylpropanedial.
在550 - 675K的温度范围内，使用光电离飞行时间质谱仪，在时间分辨的、氯原子引发的新戊烷氧化实验中研究了产物形成，特别是酮氢过氧化物的形成和分解。电离光由先进光源可调谐同步辐射或氢放电灯发出的约10.2eV固定能量辐射提供。实验分别在1 - 2个大气压下使用高压反应器进行，以及在约9托压力下使用低压反应器进行以作比较。由于新戊烷的高度对称结构，酮氢过氧化物信号可归因于3 - 氢过氧基 - 2,2 - 二甲基丙醛异构体，即来自γ - 酮氢过氧化物（γ - KHP）。在低压和高压以及不同氧浓度下测量的γ - KHP的光电离光谱彼此吻合良好，进一步支持它们源自单一异构体。在这项工作中进行的测量还表明，“科尔切克”机制可能在3 - 氢过氧基 - 2,2 - 二甲基丙醛的分解中起重要作用，特别是在较低温度下。然而，在较高温度下，γ - KHP分解为羟基自由基和氧自由基占主导，氧自由基的氧化产生了一个导致丙酮、一氧化碳和羟基自由基的新的重要通道。从最初的新戊基 + O反应开始，这个通道总共释放三个羟基自由基。在m/z = 100处观察到一种强烈依赖温度的反应产物，可能归因于2,2 - 二甲基丙二醛。
