Modeling the Thermal Destruction of Toluene (C7H8) as Tar-Related Species for Fuel Gas Cleanup

Abstract

Thermal destruction of vaporized toluene in the presence of a [N2 + H2O + O2] in air and [N2 + H2 + H2O] gas mixtures are examined. Toluene (P[C7H8] = 0.93−1.85 kPa) is used as model species present in tar-related volatile organic compounds from advanced thermochemical conversion technologies. Experiments were performed in a nonisothermal tubular flow reactor at a total pressure of ca. 101.3 kPa, temperature range of 973−1223 K. In presence of oxygen-containing molecules (molar ratios of [H2O + O2]/C7H8 were varied between 1.78 and 3.52), a first-order reaction rate could express the effects of temperature and residence time. Thermal destruction of toluene in [N2 + H2 + H2O] gas mixture ([H2 + H2O]/C7H8 = 3.52, and 0.40 < τ < 0.90 s) was studied as reference. Activation energies of the thermal destruction of toluene are: 356 ± 5 kJ mol-1 in [N2 + H2O + O2] atmosphere and 250 ± 10 kJ mol-1 in [N2 + H2 + H2O] gas mixture. A chemical reaction network and a free-radical mechanism have been suggested to expla...