A shock tube kinetic study on the branching ratio of methanol + OH reaction

Abstract

24Methanol (CH3OH) is the simplest alcohol and is considered to be a future fuel, produced by 25 solar-driven reduction of carbon dioxide. The reaction of methanol and hydroxyl radicals is 26 important in both combustion and atmospheric systems because this reaction is the dominant 27 consumption pathway for methanol oxidation. Hydrogen abstraction at the CH3 or OH site of 28 CH3OH leads to different radical intermediates. The relative importance of these two channels 29 is critical for combustion modeling as the subsequent chemistries of the product radicals (CH3O 30 and CH2OH) are markedly different. In this work, we measured overall rate coefficients for the 31 reaction of methanol (CH3OH), methanol-d3 (CD3OH) and methanol-d1 (CH2DOH) Using our measured total rate coefficients, we determined site-specific H-abstraction rate 38 coefficients, and, hence, branching ratios of the two abstraction channels. Our results show that 39 abstraction at the CH3 site is the dominant channel, contributing more than 80% throughout our 40 temperature range. Our calculated site-specific rate coefficients (per H atom) over 900 -1300 41

Kinetic Model for High-Pressure Methanol Oxidation in Gas Phase and Supercritical Water

“…Xu and Lin computed theoretically the total and individual rate constants and product branching ratios for CH 3 OH + OH at 200–3000 K; their evaluation was adopted in Aramco 15.34 . Recently, Liu et al measured the total rate constant by employing a shock tube/UV laser absorption technique. The reported values were consistent with those obtained by Zaczek et al The individual rate constants for two reaction channels were also determined in the temperature range of 900–1300 K. The branching ratio of the CH 2 OH channel was found to decrease slightly with temperature; it is lower than the calculated value by Xu and Lin but in good agreement with the value from Rasmussen et al, determined at 1000 K. Comparisons of the total rate constants and branching ratios from literature are shown in Figure .…”

Water Catalysis of the Reaction of Methanol with OH Radical in the Atmosphere is Negligible

“…[2][3][4][5] Removal of the methanol proceeds mainly through the degradation reaction by hydroxyl radical (OH), [6] a reaction that has been intensively studied over a broad temperature range. [7][8][9][10][11][12][13][14][15][16] The bimolecular rate constant is a nonmonotonic function of temperature with a dramatic enhancement at low temperatures (< 200 K). The enhancement is ascribed to an H-bonded complex, which can be stabilized at low temperatures and thus provide a route for low-energy tunneling.…”

Symmetric Ethers as Bioderived Fuels: Reactivity with OH Radicals

“…We solved β(1°) by utilizing the theoretical work of Zhou et al for EME + OH reaction, as follows: Hence, α(2°) and β(1°) will be constrained by α(2°)| Zhou and β(1°)| Zhou , respectively. As in our recent work, the genetic algorithm function available in Matlab was used to optimize α(2°), β(1°), and β(2°) using eqs , , , , and via the following objective functions: The overall objective function OF is then defined as Here, W exp . and W th .…”

“…Hence, α(2°) and β(1°) will be constrained by α(2°)| Zhou and β(1°)| Zhou , respectively. As in our recent work, 36 the genetic algorithm function available in Matlab was used to optimize α(2°), β(1°), and β(2°) using eqs 6, 7, 10, 13, and 15 via the following objective functions:…”