| 1. |
- Konnov, Alexander A., et al.
(författare)
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Combustion chemistry of methoxymethanol. Part II : Laminar flames of methanol+formaldehyde fuel mixtures
- 2021
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Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180. ; 229
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, the laminar burning velocities of mixtures of up to 16.4% (mol) formaldehyde in methanol, burning with air, were determined at atmospheric pressure using the heat flux method covering lean, stoichiometric and rich flames at initial gas mixture temperatures of 298, 318 and 338 K. Results published in the literature indicate that evaporation of CH2O+CH3OH fuel blends should lead to a gaseous mixture of formaldehyde, methanol and methoxymethanol, although the composition of these components in the gas phase was not well defined. To interpret the measurements performed in the present study, the detailed kinetic model developed by the group of Konnov was used. The recently updated mechanism was further extended by the reactions of methoxymethanol with the rate constants calculated in Part I of the present study. A comparison of the predictions of this mechanism with the new experimental data indicated that between 40% and 60% of CH2O present in the investigated CH2O+CH3OH mixtures were at 473 K evaporated as gaseous formaldehyde monomer, while the rest was released within CH3OCH2OH. Laminar burning velocity results suggest partial condensation of methoxymethanol in the CH3OH+CH2O fuel mixture with 5.84% formaldehyde at rich conditions and 298 K. These observations allowed evaluation of the partial pressure of CH3OCH2OH which was found to be between 0.35 and 0.52 kPa. The sensitivity and rate-of-production analyses revealed that the reduced reactivity with the increased amount of methoxymethanol in the fuel mixtures is explained by the conversion of CH3OCH2OH to CH3OCHOH radicals due to favored H-abstraction from the secondary hydrogen atoms predicted by ab initio calculations compared to other sites of methoxymethanol. Hydroxyl-methoxyl-methyl radicals further decompose forming slowly reacting formic acid and methyl radicals.
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| 2. |
- Zhu, Yuxiang, et al.
(författare)
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Combustion chemistry of methoxymethanol. Part I : Chemical kinetics of hydrogen-abstraction reactions and the unimolecular reactions of the product [C2H5O2] radicals
- 2021
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Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180. ; 229
-
Tidskriftsartikel (refereegranskat)abstract
- The reaction kinetics of hydrogen-abstraction reactions from methoxymethanol (CH3OCH2OH) by hydrogen (Ḣ) atom, hydroxyl (ȮH), hydroperoxyl (HȮ2), methyl (ĊH3) and methoxyl (CH3Ȯ) radicals, and decomposition of the related hydroxyl-methoxyl-methyl (CH3OĊHOH), hydroxymethoxyl-methyl (ĊH2OCH2OH) and methoxyl-methoxy (CH3OCH2Ȯ) radicals, have been investigated in this study through high-level ab initio calculations. The stationary points of the potential energy surfaces have been determined at the CCSD(T)/aug-cc-pVTZ level of theory corrected by MP2/aug-cc-pVT,QZ methods, based on the optimized geometries obtained from BHandHLYP/6–311++G(d,p) method. Rate constants at temperatures from 300 to 2000 K for H-abstraction reactions by Ḣ atom, HȮ2, ĊH3 and CH3Ȯ radicals have been obtained using conventional transition state theory (TST), while those for H-abstraction reactions by ȮH radical have been calculated employing variation transition state theory (VTST). It is found that the H-abstraction reactions from the secondary carbon atom of methoxymethanol are the most favored pathways. Total rate constants for H-abstraction reactions by ȮH radical are the fastest among the title H-abstraction reactions at temperatures below 1000 K, while H-abstraction reactions by Ḣ atom are more competitive at temperatures above 1200 K. Pressure-dependent rate constants at temperatures in the range of 300–2000 K and at pressures from 0.01 to 100 atm for the unimolecular reactions of CH3OĊHOH, ĊH2OCH2OH and CH3OCH2Ȯ radicals have been obtained from Rice-Ramsperger-Kassel-Marcus/Master Equation (RRKM/ME) calculations. Temperature-dependent thermochemical properties for methoxymethanol and related radicals have been computed using a combination of composite methods.
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