Ethanol oxidation with high water content: A reactive molecular dynamics simulation study
Ethanol oxidation with high water content: A reactive molecular dynamics simulation study
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DOI：
10.1016/j.fuel.2018.08.040
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发表时间：
2019-01-01
期刊：
影响因子：
7.4
通讯作者：
Hellier, Paul
中科院分区：
文献类型：
--
作者：
Feng, Muye;Jiang, Xi Zhuo;Hellier, Paul
乙醇是传统化石燃料的潜在替代品。然而，生产无水乙醇所需的脱水过程是极其耗能和昂贵的。一个有前途的解决方案是直接使用含水乙醇用于燃烧应用，这可以显著降低生产成本。许多研究人员已经进行了实验，证明了含水乙醇单独作为燃料燃烧的可行性和优势。本研究采用分子动力学（MD）模拟，结合反应力场（ReaxFF），研究含水乙醇氧化的基本反应机理，并与燃油-空气条件下的乙醇氧化进行比较，以了解加水对乙醇氧化的影响。结果表明，乙醇在水中的氧化反应速率比在氮气中快，水的存在促进了离子化过程，加快了自由基的产生速率，从而促进了氧化反应。此外，它表明，水含量在低温下的反应中起着至关重要的作用，但在高温下的影响可以忽略不计。详细的反应路径和相关关键物种的时间演化表明，H2O促进了许多涉及OH生成的反应，这些OH自由基也促进了其与C1和C2中间体的反应以及C1和C2中间体的脱氢。类似地，由于CO与OH反应最终将CO转化为CO2，因此在含水乙醇氧化中CO的产生减少。因此，水的加入促进了OH的产生，这是由于H2O的化学作用导致乙醇氧化的增强和CO产生的减少。总之，本研究为含水乙醇作为低成本燃料直接用于燃烧系统提供了科学依据。
Ethanol is a potential alternative to conventional fossil fuels. However, the required dewatering process to produce anhydrous ethanol is extremely energy-intensive and expensive. A promising solution is the direct use of hydrous ethanol for combustion applications, which can dramatically reduce the production cost. Many researchers have undertaken experiments demonstrating the feasibility and advantages of burning hydrous ethanol solely as a fuel. In this study, molecular dynamics (MD) simulation with the reactive force field (ReaxFF) is employed to investigate the fundamental reaction mechanisms of hydrous ethanol oxidation in comparison with the ethanol oxidation under fuel-air condition in order to understand the effects of water addition on ethanol oxidation. The results show that the reaction rate of ethanol oxidation is faster in water than in nitrogen environment and the presence of water advances the ionisation process and accelerates the radical production rate thereby enhancing the oxidation reaction. Additionally, it is suggested that the water content plays a vital role in reactions at low temperatures but that effect can be ignored at high temperatures. The detailed reaction pathways and time evolution of relevant key species indicate that H2O promotes many reactions involving OH generation and these OH radicals also facilitate its reactions with C-1 & C-2 intermediates as well as the dehydrogenation of C-1 & C-2 intermediates. Similarly, CO production is reduced in hydrous ethanol oxidation as a result of CO reaction with OH converting the CO to CO2 ultimately. Therefore, it is the addition of water that promotes the OH production due to the chemical effect of H2O leading to the enhancement of ethanol oxidation and reduction of CO production. In summary, this research provides the scientific base for the direct use of hydrous ethanol as a fuel for combustion systems with a low cost.