Experimental Investigation of Toluene + H → Benzyl + H2 at High Temperatures

Abstract

The reaction of toluene with hydrogen atoms yielding benzyl and molecular hydrogen, C(6)H(5)CH(3) + H --> C(6)H(5)CH(2) + H(2), was investigated using UV laser absorption of benzyl radicals at 266 nm in shock tube experiments. Test gas mixtures of toluene and ethyl iodide, an H-atom source, diluted in argon were heated in reflected shock waves to temperatures ranging from 1256 to 1667 K at total pressures around 1.7 bar. Measurement of laser absorption at 266 nm due to benzyl radicals allowed determination of the rate coefficient of the title reaction, reaction 1. A two-parameter best-fit Arrhenius expression for the rate determinations over the temperature range of these experiments is given by k(1)(T) = 1.33 x 10(15) exp(-14880 [cal/mol]/RT) [cm(3) mol(-1) s(-1)]. With the use of both the high-temperature shock tube measurements reported here and the rate coefficient determination of Ellis et al. (Ellis, C.; Scott, M. S.; Walker, R. W. Combust. Flame 2003, 132, 291) at 773 K the best-fit rate coefficient for reaction 1 can be described using a three-parameter Arrhenius expression by k(1)(T) = 6.47T (3.98) exp(-3384 [cal/mol]/RT) [cm(3) mol(-1) s(-1)].