• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Ethanol Oxidation: Kinetics of the a-Hydroxyethyl Radical + O_2Reaction
【24h】

Ethanol Oxidation: Kinetics of the a-Hydroxyethyl Radical + O_2Reaction

机译：乙醇氧化：α-羟乙基自由基+ O_2反应的动力学

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Bioethanol is currently a significant gasoline additive and the major blend component of flex-fuel formulations.Ethanol is a high-octane fuel component, and vehicles designed to take advantage of higher octane fuel blendscould operate at higher compression ratios than traditional gasoline engines, leading to improved performanceand tank-to-wheel efficiency. There are significant uncertainties, however, regarding the mechanism for ethanolautoignition, especially at lower temperatures such as in the negative temperature coefficient (NTC) regime.We have studied an important chemical process in the autoignition and oxidation of ethanol, reaction of theα-hydroxyethyl radical with O_2(~3P), using first principles computational chemistry, variational transition statetheory, and Rice—Ramsperger—Kassel—Marcus (RRKM)/master equation simulations. The α-hydroxyethyl+ O_2association reaction is found to produce an activated α-hydroxy—ethylperoxy adduct with ca. 37 kcalmol~(-1)of excess vibrational energy. This activated adduct predominantly proceeds to acetaldehyde + HO_2,with smaller quantities of the enol vinyl alcohol (ethenol), particularly at higher temperatures. The reactionto acetaldehyde + HO_2proceeds with such a low barrier that collision stabilization of C_2O_3H_5isomers isunimportant, even for high-pressure/low-temperature conditions. The short lifetimes of these radicals precludesthe chain-branching addition of a second O_2molecule, responsible for NTC behavior in alkane autoignition.This result helps to explain why ignition delays for ethanol are longer than those for ethane, despite ethanolhaving a weaker C—C bond energy. Given its relative instability, it is also unlikely that the α-hydroxy—ethylperoxyradical acts as a major acetaldehyde sink in the atmosphere, as has been suggested.
机译：生物乙醇目前是重要的汽油添加剂，也是弹性燃料配方的主要混合物组分。乙醇是高辛烷值燃料组分，设计用于利用较高辛烷值燃料混合物的车辆的压缩比应高于传统汽油发动机，从而导致改进的性能和油轮效率。然而，关于乙醇自燃的机理，尤其是在较低温度下，例如在负温度系数（NTC）状态下，存在很大的不确定性。我们研究了乙醇自燃和氧化，α-羟乙基自由基反应的重要化学过程。在O_2（〜3P）的条件下，使用第一原理计算化学，变分过渡状态理论和Rice-Ramsperger-Kassel-Marcus（RRKM）/主方程模拟。发现α-羟乙基+ O_2缔合反应产生活化的α-羟基-乙基过氧加合物，其具有约。 37 kcalmol〜（-1）的多余振动能量。该活化的加合物主要以较少量的烯醇乙烯醇（乙烯醇）进行，生成乙醛+ HO_2，特别是在较高温度下。与乙醛+ HO_2的反应以如此低的势垒进行，即使对于高压/低温条件，C_2O_3H_5异构体的碰撞稳定性也并不重要。这些自由基的寿命短，可防止在链烷中添加第二个O_2分子，从而导致烷烃自燃中的NTC行为。该结果有助于解释为何乙醇的点火延迟比乙烷的点火延迟长，尽管乙醇的CC键能量较弱。考虑到其相对的不稳定性，α-羟基-乙基过氧自由基也不太可能充当大气中的主要乙醛吸收剂。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号