EXPERIMENTAL AND MODELLING STUDY OF PROPANE AROMATIZATION OVER H-ZSM-5 CATALYSTS PREPARED BY DIFFERENT SILICA SOURCES

The catalytic performance of H-ZSM-5 samples prepared from different silica sources, namely, Ludox (sample A), waterglass (sample B) and tetraethyl orthosilicate (sample C) in aromatization of propane was studied. The catalysts were characterized by BET, SEM, XRD and NH3-TPD techniques to analyze the structure and acidity of the active sites. The performance tests were carried out in fixed-bed reactor at 550 degrees C. For a quantitative assessment, the long-term propane conversion data were fitted with a second order kinetics for the main reaction and a second order independent kinetics for deactivation using integral method of analysis. Fair fits were observed. According to silica source, the order for activity and stability were A>B>C and B>C>A, respectively. The incorporation of Zn (0.4 wt. %) as a promoter showed beneficial effect on aromatic selectivity at the expense of propane conversion and catalyst stability. The introduction of Zn decreased the rate constant of aromatization from 9.4 to 8.7 m(6)kg(-1)mol(-1)h(-1) at 550 degrees C, while the rate constant of deactivation increased by a factor of five, that is, from 0.0056 to 0.025 h(-1).