Pressure-dependent kinetics of peroxy radicals formed in isobutanol combustion
Pressure-dependent kinetics of peroxy radicals formed in isobutanol combustion
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异丁醇燃烧中形成的过氧自由基的压力依赖性动力学
DOI：
10.1039/d0cp02872j
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发表时间：
2020
影响因子：
3.3
通讯作者：
Green, William H.
中科院分区：
文献类型：
--
作者：
Goldman, Mark Jacob;Yee, Nathan W.;Kroll, Jesse H.;Green, William H.
生物衍生的异丁醇已被批准作为汽油添加剂在美国，但我们对其燃烧化学的理解仍然有很大的不确定性。详细的量子计算可以提高模型的准确性，从而更好地估计异丁醇的燃烧特性及其对环境的影响。这项工作研究了47个分子和38个反应，涉及第一次氧加成到异丁醇的三个烷基自由基位于α，β和γ的氢氧化物。量子计算主要在CCSD（T）-F12/cc-pVTZ-F12//B3 LYP/CBSB 7上进行，在B3 LYP/6- 31 G（d）上进行了一维位阻转子修正。由此产生的势能面是迄今为止发表的最全面的过氧异丁醇网络。正则过渡态理论和1-D微正则主方程分别用于推导高压极限和压力相关速率系数。在所研究的所有条件下，γ-异丁醇自由基与O_2复合形成HO_2 ~+异丁醛。在400 K以下，β-异丁醇自由基与O2复合形成稳定的过氧烃基，在较高温度下，形成水+烷氧基，在1200 K以上，形成HO 2+烯烃。在700-1100 K温度范围内，β-异丁醇自由基与O2复合生成混合产物，在较低温度下生成丙酮+甲醛+ OH，在较高温度下生成HO 2+烯烃。势垒高度，高压极限速率，和压力依赖的动力学一般同意从以前的量子化学计算的结果。在这项工作中的六个反应速率偏离超过三个数量级的动力学在详细的模型异丁醇燃烧，这表明这里计算的速率可以帮助改善建模异丁醇燃烧及其环境命运。
Bio-derived isobutanol has been approved as a gasoline additive in the US, but our understanding of its combustion chemistry still has significant uncertainties. Detailed quantum calculations could improve model accuracy leading to better estimation of isobutanol's combustion properties and its environmental impacts. This work examines 47 molecules and 38 reactions involved in the first oxygen addition to isobutanol's three alkyl radicals located α, β, and γ to the hydroxide. Quantum calculations are mostly done at CCSD(T)-F12/cc-pVTZ-F12//B3LYP/CBSB7, with 1-D hindered rotor corrections obtained at B3LYP/6-31G(d). The resulting potential energy surfaces are the most comprehensive isobutanol peroxy networks published to date. Canonical transition state theory and a 1-D microcanonical master equation are used to derive high-pressure-limit and pressure-dependent rate coefficients, respectively. At all conditions studied, the recombination of γ-isobutanol radical with O2 forms HO2 + isobutanal. The recombination of β-isobutanol radical with O2 forms a stabilized hydroperoxy alkyl radical below 400 K, water + an alkoxy radical at higher temperatures, and HO2 + an alkene above 1200 K. The recombination of β-isobutanol radical with O2 results in a mixture of products between 700–1100 K, forming acetone + formaldehyde + OH at lower temperatures and forming HO2 + alkenes at higher temperatures. The barrier heights, high-pressure-limit rates, and pressure-dependent kinetics generally agree with the results from previous quantum chemistry calculations. Six reaction rates in this work deviate by over three orders of magnitude from kinetics in detailed models of isobutanol combustion, suggesting the rates calculated here can help improve modeling of isobutanol combustion and its environmental fate.