Propane Aromatization over Mo／HZSM—5 Catalysts

Impregnation, mechanical mixing and hydrothermal treatment methods were used to introducemolybdenum species into the HZSM-5 zeolite. The structure and surface acidity of the catalysts werestudied by means of XRD, FT-IR, NH3-TPD, TPR and XPS. The effects of Mo content and reaction timeon stream on the aromatization of propane were investigated. It was found that the performance of theMo/HZSM-5 catalyst prepared by the hydrothermal treatment method was much better than that of theother two catalysts. For example, under the reaction conditions of 823 K and 600 h-1, propane conversionand aromatics selectivity over the catalyst prepared by hydrothermal pretreatment could reach 89.17%and 78.56%, respectively. XRD and XPS results showed that the Mo species in the catalysts preparedby hydrothermal treatment were highly dispersed on the surface of the HZSM-5, and larger amounts ofthem could penetrate into the HZSM-5 channel, as compared with the other two kinds of catalysts. Thesefactors may be responsible for their high activities for propane aromatization. IR and NH3-TPD studiesindicated that the number of Bronsted acid centers decreased and the Lewis acid centers increased afterMo was introduced into the HZSM-5 zeolite.