The oxidation of 1,3-butadiene: Experimental results and kinetic modeling

The oxidation of 1,3-butadiene has been investigated in a jet-stirred reactor at high temperature (similar to 750-1250 K), variable pressure (1 and 10 atm) and variable equivalence ratio (0.25 less than or equal to phi less than or equal to 2). Molecular species concentration profiles of O-2, H-2, CO, CO2, CH2O, CH4, C2H2, C2H4, C2H6, C3H4 (allene and propyne), C3H6, acrolein, 1-C4H8, 2-C4H8 (cis and trans), 1,3-C4H6, vinylacetylene, cyclopentadiene, and benzene were obtained by probe sampling and GC analysis. The oxidation of 1,3-butadiene in these conditions was modeled using a detailed kinetic reaction mechanism (91 species and 666 reactions, most of them reversible). The proposed mechanism, also validated for the oxidation of simpler hydrocarbons and natural gas blends in the same conditions, is able to reasonably well-predict the experimental results obtained in this study. Sensitivity analyses and reaction path analyses, based on species net rate of reaction, are used to interpret the present results. The routes to benzene formation have been delineated: At low fuel conversion and low temperature, benzene is mostly formed through the addition of vinyl radical to 1,3-butadiene, yielding 1,3-cyclohexadiene, followed by two channels: (a) elimination of molecular hydrogen to yield benzene and (b) decomposition of 1,3-cyclohexadiene yielding cyclohexadienyl followed by its decomposition into benzene and H atom; at high fuel conversion and higher temperature, (c) the recombination of propargyl radicals and (d) the addition of vinyl to vinylacetylene increasingly yield to benzene formation.