Wang Zhandong, Herbinet Olivier, Cheng Zhanjun, Husson Benoit, Fournet René, Qi Fei, Battin-Leclerc Frédérique
Laboratoire Réactions et Génie des Procédés, CNRS - Université de Lorraine, BP 20451, 1 rue Grandville, 54000 Nancy, France.
J Phys Chem A. 2014 Jul 31;118(30):5573-94. doi: 10.1021/jp503772h. Epub 2014 Jul 22.
The low-temperature oxidation of the five hexane isomers (n-hexane, 2-methyl-pentane, 3-methyl-pentane, 2,2-dimethylbutane, and 2,3-dimethylbutane) was studied in a jet-stirred reactor (JSR) at atmospheric pressure under stoichiometric conditions between 550 and 1000 K. The evolution of reactant and product mole fraction profiles were recorded as a function of the temperature using two analytical methods: gas chromatography and synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). Experimental data obtained with both methods were in good agreement for the five fuels. These data were used to compare the reactivity and the nature of the reaction products and their distribution. At low temperature (below 800 K), n-hexane was the most reactive isomer. The two methyl-pentane isomers have about the same reactivity, which was lower than that of n-hexane. 2,2-Dimethylbutane was less reactive than the two methyl-pentane isomers, and 2,3-dimethylbutane was the least reactive isomer. These observations are in good agreement with research octane numbers given in the literature. Cyclic ethers with rings including 3, 4, 5, and 6 atoms have been identified and quantified for the five fuels. While the cyclic ether distribution was notably more detailed than in other literature of JSR studies of branched alkane oxidation, some oxiranes were missing among the cyclic ethers expected from methyl-pentanes. Using SVUV-PIMS, the formation of C2-C3 monocarboxylic acids, ketohydroperoxides, and species with two carbonyl groups have also been observed, supporting their possible formation from branched reactants. This is in line with what was previously experimentally demonstrated from linear fuels. Possible structures and ways of decomposition of the most probable ketohydroperoxides were discussed. Above 800 K, all five isomers have about the same reactivity, with a larger formation from branched alkanes of some unsaturated species, such as allene and propyne, which are known to be soot precursors.
在喷射搅拌反应器（JSR）中，于大气压下、化学计量比条件下，在550至1000 K的温度范围内研究了五种己烷异构体（正己烷、2-甲基戊烷、3-甲基戊烷、2,2-二甲基丁烷和2,3-二甲基丁烷）的低温氧化。使用气相色谱和同步辐射真空紫外光电离质谱（SVUV-PIMS）这两种分析方法，记录了反应物和产物摩尔分数分布随温度的变化情况。两种方法获得的实验数据对于这五种燃料而言吻合良好。这些数据用于比较反应活性、反应产物的性质及其分布。在低温（低于800 K）下，正己烷是反应活性最高的异构体。两种甲基戊烷异构体具有大致相同的反应活性，低于正己烷。2,2-二甲基丁烷的反应活性低于两种甲基戊烷异构体，而2,3-二甲基丁烷是反应活性最低的异构体。这些观察结果与文献中给出的研究辛烷值吻合良好。已对这五种燃料中的含3、4、5和6个原子环的环状醚进行了鉴定和定量。虽然环状醚的分布比其他关于支链烷烃氧化的喷射搅拌反应器研究文献中的更为详细，但在甲基戊烷预期生成的环状醚中缺少一些环氧乙烷。使用SVUV-PIMS还观察到了C2-C3单羧酸、酮氢过氧化物以及含两个羰基的物种的形成，支持了它们可能由支链反应物生成的观点。这与之前从直链燃料实验得出的结果一致。讨论了最可能的酮氢过氧化物的可能结构和分解方式。在800 K以上，所有五种异构体具有大致相同 的反应活性，支链烷烃生成一些不饱和物种（如丙二烯和丙炔，已知它们是炭黑前驱体）的量更大。
