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

Thermal destruction of vaporized toluene in the presence of a [N 2 + H 2 O + O 2 ] in air and [N 2 + H 2 + H 2 O] gas mixtures are examined. Toluene ( P [C 7 H 8 ] = 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 [H 2 O + O 2 ]/C 7 H 8 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 [N 2 + H 2 + H 2 O] gas mixture ([H 2 + H 2 O]/C 7 H 8 = 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 [N 2 + H 2 O + O 2 ] atmosphere and 250 ± 10 kJ mol - 1 in [N 2 + H 2 + H 2 O] gas mixture. A chemical reaction network and a free-radical mechanism have been suggested to explain the products concentration distribution. The free-radical mechanism has been used to interpret the experimental trends at gas residence times (τ < 5 s).