Effect of pH on the synthesis of ZSM-5 zeolite using TEOS and performance of H-ZSM-5 catalyst in propane aromatization

Effect of alkalinity on the hydrothermal synthesis of ZSM-5 zeolite using TEOS as the Si source, TPABr as the template and NaAlO2 as the Al source was studied. Formation of the crystal phases was investigated throughout X-Ray Diffraction. BET, SEM and NH3-TPD techniques were also applied for product characterization. The results indicated the significant effect of the hydrogel alkalinity on the product specifications. Actually, different levels of alkalinity can hinder formation of crystalline phase or result in growth of other phases which are more stable than ZSM-5. An optimum of 9.7 was found for pH value leading to formation of ZSM-5 crystals with appropriate crystallinity. The catalytic performance test of the prepared H-ZSM-5 was carried out in fixed-bed reactor at 550°C. The obtained data showed a conversion of 68% for propane while the selectivity towards aromatics was 37%. A gradual decreasing trend in both of the terms was also observed which implies the preferential deactivation of active sites

Keywords:

ZSM-5 , pH , Hydrothermal synthesis , Propane Aromatization , Aromatics selectivity