Kinetic model discrimination for toluene hydrogenation over noble-metal-supported catalysts

The hydrogenation of toluene has been studied using an integral fixed-bed reactor with a Pt/γ-Al2O3 commercial catalyst over a wide range of experimental conditions: temperature = 100-250 °C, H 2 inlet pressure = 0.3-1.9 bar, toluene inlet pressure = 0.04-0.15 bar, and space time = (2-10) × 10-2 gcat h g tol -1. Hydrocarbon molecules block the active sites at elevated temperature and toluene partial pressure, and, as a consequence, three reaction-controlled regimes occur: (i) kinetic, (ii) surface coverage, and (iii) thermodynamic. The experimental data have been fitted to 23 kinetic models proposed in the literature (empirical and mechanistical), and their parameters have been estimated. The model discrimination has been performed based on statistical F-test and mechanistical aspects. A simplified kinetics model is proposed by introducing the thermodynamical equilibrium constant. Finally, that kinetic model is used for reactor simulation. © 2007 American Chemical Society.