Direct Chemical Kinetics Studies of Elusive Intermediates in Combustion: Ketohydroperoxides

可持续能源技术的发展仍然是一个重大的科学挑战，也是美国和世界其他地区的高度优先事项。鉴于目前和未来几十年对燃烧衍生能源的依赖，一个关键的挑战是提高下一代燃烧系统的效率。效率的提高依赖于对控制发动机点火和放热过程的化学反应的更好理解。这两个都是重要的优化预测模型用于模拟燃烧化学。重要的是，这些模型的有效性取决于对详细实验数据的验证。因此，本文研究的主要活动是研究以前未研究的一组分子的基本化学反应，酮氢过氧化物，这是难以捉摸的中间体，对理解点火过程至关重要。本研究的主要好处是发展新的基本理解的化学反应途径和速率相关的燃烧以及新的建模能力，以提高现有的计算机模拟模型的鲁棒性。此外，该研究项目还包括博士的科学培训。学生和本科生退伍军人，以及增加当地高中一级的教育材料有关的可持续交通能源。本文的研究解决了中间物种酮氢过氧化物的分子结构和燃烧过程中的产物形成之间的联系的知识差距。为了实现这一目标，形成了一个具有环己烷燃烧产生的酮氢过氧化物化学合成和物理化学专业知识的跨学科团队。使用两个不同的实验研究了三种异构体的反应：多路复用光电离质谱在先进光源同步加速器，和形态从高压喷射搅拌反应器在格鲁吉亚大学。在实验的同时，利用反应机理生成软件包生成了环己烷燃烧化学的新的子机理。目前的建模工作的动力是，单分子分解反应是唯一的消耗途径酮过氧化氢物种在目前的燃烧模型。然而，烷基过氧自由基常见的其他反应途径是可能的，包括与羟基自由基和与氧的反应。通过对反应途径的完整表征，化学动力学模型的现有不确定性可以通过准确的燃烧效率预测最小化。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The development of sustainable energy technologies for transportation remains a significant scientific challenge and a high priority for the United States and rest of the world. Given the current and projected reliance on combustion-derived energy for decades to come, a key challenge is increasing the efficiency of next-generation combustion systems. Improvements in efficiency relies on better understanding of chemical reactions that control ignition and heat-release processes in engines. Both are important in optimizing predictive models used to simulate combustion chemistry. Importantly, the efficacy of such models hinges on validation against detailed experimental data. Therefore, the primary activity of the research herein is the study of elementary chemical reactions from a previously unstudied set of molecules, ketohydroperoxides, which are elusive intermediates and central to understanding ignition process. The primary benefit of the present research is the development of new fundamental understanding of chemical reaction pathways and rates relevant to combustion as well as new modeling capabilities to improve the robustness of existing computer simulation models. In addition, the research project encompasses scientific training of Ph.D. students and undergraduate Student Veterans, as well as augmentation of local high school-level educational materials related to sustainable transportation energy. The research herein addresses the knowledge gap on the connection between the molecular structure of intermediate species ketohydroperoxides and products formation during combustion. To achieve this objective, an interdisciplinary team with expertise in chemical synthesis of ketohydroperoxides, derived from cyclohexane combustion, and physical chemistry is formed. Reactions of the three isomer species are studied using two different experiments: multiplexed photoionization mass spectrometry at the Advanced Light Source synchrotron, and speciation from a high-pressure jet-stirred reactor at the University of Georgia. In parallel to experiments, Reaction Mechanism Generator software package is used to generate a new sub-mechanisms for cyclohexane combustion chemistry. The impetus for the present modelling work is that unimolecular decomposition reactions are the only consumption pathways of ketohydroperoxide species in current combustion models. However, other reaction pathways common to alkylperoxy radicals are possible, including reaction with hydroxyl radicals and with oxygen. With complete characterization of reaction pathways, the existing uncertainties of chemical kinetics models can be minimized with accurate predictions of combustion efficiency.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.