Modelagem cinética da reação de aromatização do propeno sobre HZSM5.

Abstract

The aromatic hydrocarbons, generally denominated BTX (Benzene, toluene and xylenes) are very important industrial compounds. These hydrocarbons present high indexes of octane and constitute an important fraction of the gasoline. BTX are also important intermediates for synthesis in the organic chemistry. The pathway of the reaction of propene aromatization over HZSM5 is complex, involving a great number of compounds and several reaction steps, as oligomer formation, oligomer cracking, transfer of hydrogen, dienes cyclization and naphtenes aromatization. A tool quite used now for obtaintion of quantitative information about the mechanism of chemical reactions is the kinetic modelling, that allows determination of the values of the kinetic parameters starting from a limited number of experimental data. In the present work, the development of a kinetic model is proposed for the propene aromatization over the HZSM5 catalyst, based on the model proposed by Lukyanov et al. (1994). For such purpose, it was necessary to develop a simulator in order to calculate the values of the kinetic parameters and the values of the rate constants of the propene aromatization over HZSM5 in a tubular reactor, at temperatures of 350, 400, 450 and 530°C. The experimental data used were obtained from Rodrigues (1996) at reaction times of 1, 6, 12, 24 and 72 hours. The kinetic model for propene aromatization over HZSM5 was developed. The reaction is almost completely processed after one hour. Therefore, a kinetic model for this reaction in the interval from zero to one hour was developed, avoiding the introduction of the deactivation function that would become the model quite complex. The experimental data were compared with the simulated ones and showed a considered satisfactory adjustment. The results of this study showed that the simulator set up for the referred reaction can be used for other reactions which do not present a number of constant superior to five, and in the maximum four concentration data in function of the time, to avoid convergence problems.