乙酸基+O₂及其分解异构化反应速率常数计算和不确定度分析

In order to develop an accurate chemical reaction kinetic model for acetic acid, high-precision quantum computation is carried out on the addition reaction between O₂ and acetic acid radical(CH₂CO(O)H), and the thermal decomposition and isomerization reactions of CH₂CO(O)H. The potential energy surface is obtained as per the CCSD(T)-F12/cc-pVTZ-F12//B2PLYPD3/cc-pVTZ level of theory while the barrierless reaction potential energy surface using the multireference method CASPT2/CBS//CASPT2/cc-pVTZ. The temperature-and pressure-dependent rate coefficients are determined as per the RRKM/ME theory and the rate constant of the barrierless addition reaction between O₂ and acetic acid radical is obtained as per the variable reaction coordinate-transition state theory. The results show that at a low pressure or high temperature, more than 99% of chemically activated O₂CH₂CO₂H decomposes directly into CH₂O₂H+CO₂. With the increase of pressure, more chemically activated O₂CH₂CO₂H is collisionally stabilized and subsequently decomposes into CH₂O₂H+CO₂. Moreover, CO₂+CH₃ are dominant product channel of CH₂CO(O)H decomposition. A previous model for acetic acid is modified based on the calculation results. The improved model can better predict the laminar burning velocity and provides more pathways for CH₂CO(O)H consumption. The results obtained are consistent with those from quantum calculation.