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Thermal ignition of acetonitrile. Experimental results and kinetic modeling
Author(s) -
Lifshitz Assa,
Tamburu Carmen,
Carroll Harvey F.
Publication year - 1997
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/(sici)1097-4601(1997)29:11<839::aid-kin5>3.0.co;2-n
Subject(s) - chemistry , acetonitrile , ignition system , analytical chemistry (journal) , oxygen , dissociation (chemistry) , shock wave , argon , atmospheric temperature range , shock tube , autoignition temperature , thermodynamics , combustion , organic chemistry , physics
Ignition delay times of acetonitrile (CH 3 CN) in mixtures containing acetonitrile and oxygen diluted in argon were studied behind reflected shock waves. The temperature range covered was 1420–1750 K at overall concentrations behind the reflected shock wave ranging from 2 to 4×10 −5 mol/cm 3 . Over this temperature and concentration range the ignition delay times varied by approximately one order of magnitude, ranging from ca. 100 μs to slightly above 1 ms. From a total of some 70 tests the following correlation for the ignition delay times was derived: t ign =9.77×10 −12 exp(41.7×10 3 / RT )×{[CH 3 CN] 0.12 [O 2 ] −0.76 [Ar] 0.34 } s, where concentrations are expressed in units of mol/cm 3 and R is expressed in units of cal/(K mol). The ignition delay times were modeled by a reaction scheme containing 36 species and 111 elementary reactions. Good agreement between measured and calculated ignition delay times was obtained. A least‐squares analysis of 60 computed ignition delay times from six different groups of initial conditions gave the following temperature and concentration dependence: E=46.2×10 3 cal/mol, β CH 3 CN =0.43, β O 2=−1.18, and β Ar =0.18. The ignition process is initiated by H‐atom ejection from acetonitrile. The addition of oxygen atoms to the system from the dissociation of molecular oxygen and from the reaction CH 3 CN+O 2 → HO 2 ·+CH 2 CN·is negligible. In view of the relatively high concentration of methyl radicals obtained in the reaction CH 3 CN+H → CH 3 +HCN, the branching step CH 3 +O 2 → CH 3 O+O plays a more important role than the parallel step H+O 2 → OH+O. A discussion of the mechanism in view of the sensitivity analysis is presented. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 839–849, 1997