EVOLUTION OF H-ZSM-5 ZEOLITE STRUCTURE AL ONG ITS PREPARATION THERMAL-TREATMENT STEPS

The thermal treatment steps in the preparation of acidic H-ZSM-5 zeoli tes have been studied by using the techniques of thermogravimetry and in situ FTIR spectrophotometry by difuse reflectance in catalytic cham ber. From the observation of the treatment temperature effect on cryst allinity and on concentration of structural hydroxyl groups (strong ac idic sites), it is concluded that in order to optimize these propertie s, the thermal decomposition of tetrapropylamonium should be carried o ut at 500-degrees-C and the calcination for obtaining the acidic form of the zeolite, at 400-degrees-C.