Thermal decomposition of benene. Single-pulse shock-tube investigation

The thermal decomposition of benzene was studied behind reflected shocks in a pressurized driver single-pulse shock tube. The temperature range covered was 1400–2000 K at overall densities of ∼3.5×10−5 mol/cm3. Gas chromatography (GC) analyses of post-shock samples revealed the presence of the following decomposition products: C2H2, C4H2, C6H5-C≡CH, C6H5-C6H5, and small quantities of C6H2 and C6H4. The main decomposition product at low temperatures is biphenyl, which is formed in the reaction C6H5+C6H6→C6H5-C6H5+H. At higher temperatures, the opening of the phenyl radical becomes a major reaction that competes with its attack on benzene. At these temperatures, the main products are C2H2 and C4H2. A reaction scheme containing 15 species and 22 elementary reactions reproduces very well the experimental product distribution. Kinetic modeling indicates that at low temperatures the overall decomposition of benzene is second order with respect to benzene. At high temperatures, the decomposition is close to a first-order reaction with a rate constant given by ktotal=2.14×1010 exp(−63.0×103/RT) s−1, where R is expressed in units of cal/(K mol). Arrhenius rate parameters for the production rates of the decomposition products are given, and a discussion of the mechanism is presented.