Kinetics of 1,2-Dimethylbenzene Oxidation and Ignition: Experimental and Detailed Chemical Kinetic Modeling

Abstract

New experimental results were obtained for the oxidation of 1,2-dimethylbenzene in a jet-stirred reactor (JSR) at atmospheric pressure in dilute conditions over the temperature range 900–1400 K, and variable equivalence ratio (0.5 ≤ ϕ ≤ 1.5). The data consisted of concentration profiles vs. temperature for the reactants, stable intermediates and final products, measured by sonic probe sampling followed by on-line GC-MS analyses and off-line GC-TCD-FID and GC-MS analyses. The ignition of 1,2-dimethylbenzene-oxygen-argon mixtures was measured behind reflected shock waves over the temperature range 1400–1830 K, at 1 atm, and variable equivalence ratio (0.5 ≤ ϕ ≤ 2.0), using a shock tube (ST). The oxidation and ignition of 1,2-dimethylbenzene under respectively JSR and ST conditions were modeled using a detailed chemical kinetic reaction mechanism (219 species and 1545 reactions, most of them reversible) deriving from a previous scheme proposed for the ignition, oxidation, and combustion of simple aromatics (benzene, toluene, styrene, n-propyl-benzene, 1,3-dimethylbenzene, and 1,4-dimethylbenzene). Sensitivity analyses and reaction path analyses, based on rates of reaction, were used to interpret the results. This study showed the reactivity of 1,2-dimethylbenzene is higher than that of 1,3-dimethylbenzene and 1,4-dimethylbenzene under the above conditions.

Keywords:

• 1,2-dimethylbenzene
• Jet-stirred reactor
• Kinetic
• Modeling
• Shock-tube
• Xylene

S.G. thanks the French MENRT for a Doctoral grant. G.B. thanks the Environmental Protection Agency of Ireland for support. The authors are grateful to Dr. F. Lecomte for his help with the JSR experiments, to Dr. M. Cathonnet for his interest in this research and Pr. J. Bozzelli for his help in the calculation of o-xylylene thermochemical data.

Notes

Nomenclature: 5-methylcyclopenta-1,3-diene, MeCPD; 5-methyl-1,3-cyclopentadienyl, MeCDPY; 2-methyl-1-hydroxybenzene, o-MePhOH; 2-methyl-1-hydroxybenzene radical, o-OC₇H_7; 2-methylphenyl radical, o-C₆H₄CH_3; 2-formylphenyl radical, Y1P2CHO; 2-formyl-1-hydroxybenzene radical, OY1P2CHO; 1,2-dimethylbenzene, 1,2 -xylene; 2-methylbenzyl radical, o-xylyl; o-xylylene or 5,6-dimethylenecyclohexa-1,3-diene, o-CH₂PhCH₂; 1-formyl-2-methylbenzene, o-MePhHCO; 1-carbonyl-2-methylbenzene radical, o-MePhCO; 2-methyl-1-hydroxymethylbenzene, o-MePhCH₂OH; 2-methyl-1-hydroxydedydro-1-methylbenzene radical, o-MePhCHOH; 2-methyl-1-hydroxymethylbenzene radical, o-MePhCH₂O; 1,2-diformylbenzene, o-CHOPhCHO; 1-carbonyl-2-formylbenzene radical, CHOPhCO; 2-formylbenzyl radical, o-CHOPhCH₂; 2-ethylphenyl radical, Y1P2Et; 2-ethyl-1-hydroxybenzene radical, OY1P2Et; 2-ethyl-1-methylbenzene, o-MePhC₂H₅; 2-methyl-1-ethylenebenzene radical, o-AMePhC₂H₄; 2-methyl-1-ethylidenebenzene radical, o-BMePhC₂H_4; 2-methyl-1-vinylbenzene, o-MeStyrene; 2-methyl-1-ethen-1-yl benzene radical, o-AMeStyryl; 2-methyl-1-ethen-2-yl benzene radical, o-BMeStyryl; 1-formyl-2-ethylbenzene radical, o-EtPhHCO; 1-carbonyl-2-ethylbenzene radical, o-EtPCO; 2-ethylbenzyl radical, MY1P2Et; 2,2′-dimethylbiphenyl, o-MePPMe; 2,2′-dimethylbibenzyl, o-DiMePCH2; benzocylobutene, BZCYBUT.

Note: (a) Based on previous work on p- and m-xylene (Gaïl and Dagaut, 2005, 2007); (b) this work; (c) Roth et al. (1978 and 1981).

Units: ΔH° _{f (298)} in kcal/mol; ΔS° _{f (298)} and C _p (T) in cal/mol/K.

^a T₅±15 K, τ±15%.