کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6679396 | 1427927 | 2009 | 8 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
A shock-tube and theory study of the dissociation of acetone and subsequent recombination of methyl radicals
دانلود مقاله + سفارش ترجمه
دانلود مقاله ISI انگلیسی
رایگان برای ایرانیان
کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
مهندسی شیمی
مهندسی شیمی (عمومی)
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
The dissociation of acetone: CH3COCH3 â CH3CO + CH3, quickly followed by CH3CO â CH3 + CO, has been examined with Laser-Schlieren measurements in incident shock waves over 32-717 Torr and 1429-1936 K using 5% acetone dilute in krypton. A few very low pressure experiments (â¼10 Torr) were used in a marginal effort to resolve the extremely fast vibrational relaxation of this molecule. This effort was partly motivated as a test for molecular, “roaming methyl” reactions, and also as a source of methyl radicals to test the application of a recent high-temperature mechanism for ethane decomposition [J.H. Kiefer, S. Santhanam, N.K. Srinivasan, R.S. Tranter, S.J. Klippenstein, M.A. Oehlschlaeger, Proc. Combust. Inst. 30 (2005) 1129-1135] on the reverse methyl combination. The gradient profiles show strong initial positive gradients and following negative values fully consistent with methyl radical formation and its following recombination. Thus C-C fission is certainly a large part of the process and molecular channels cannot be responsible for more than 30% of the dissociation. Rates obtained for the C-C fission show strong falloff well fit by variable reaction coordinate transition state theory when combined with a master equation. The calculated barrier is 82.8 kcal/mol, the fitted ãÎEãdown = 400 (T/298) cmâ1, similar to what was found in a recent study of C-C fission in acetaldehyde, and the extrapolated kâ = 1025.86 Tâ2.72 exp(â87.7 (kcal/mol)/RT), which agrees with the literature rate for CH3 + CH3CO. Large negative (exothermic) gradients appearing late from methyl combination are accurately fit in both time of onset and magnitude by the earlier ethane dissociation mechanism. The measured dissociation rates are in close accord with one earlier shock-tube study [K. Sato, Y. Hidaka, Combust. Flame 122 (2000) 291-311], but show much less falloff than the high pressure experiments of Ernst et al. [J. Ernst, K. Spindler, H.Gg. Wagner, Ber. Bunsenges. Phys. Chem. 80 (1976) 645-650].
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Proceedings of the Combustion Institute - Volume 32, Issue 1, 2009, Pages 123-130
Journal: Proceedings of the Combustion Institute - Volume 32, Issue 1, 2009, Pages 123-130
نویسندگان
Saumitra Saxena, John H. Kiefer, Stephen J. Klippenstein,