Kinetics of the liquid-phase hydrogenation of toluene

The toluene hydrogenation over an industrial platinum/alumina catalyst has been studied. Experiments have been done in a batch reactor, at pressures in the range 1.6 to 3.5 MPa and at temperatures in the range of 393 to 423 K. The main reaction product was methyl cyclohexane. The analysis of experimental data shows that the apparent order of the reaction for toluene is lower than that for hydrogen, that the specific reaction constant values are comparable to those reported in the literature, and that the apparent activation energy is 53.3 kJ/mole. Experimental data have been also adjusted using a mathematical model based on a Langmuir-Hinshelwood type mechanism, assuming a non competitive adsorption to toluene and hydrogen, on two different kind of active centers. It is also assumed that the reaction between toluene and hydrogen is the controlling step of the whole process. From the results it can be seen that the kinetic expression satisfactorily represents the hydrogenation process of toluene. The values of the kinetic parameters are consistent with the mechanism proposed to derive the rate expression.