IMPROVEMENT OF CATALYTIC PROPERTIES OF SAPO-31 MOLECULAR-SIEVES BY USING AN ACTIVATED FORM OF SIO2

SAPO-31 molecular sieves the synthesis of which is based on different types Of SiO2 were physico-chemically characterized by X-ray diffracti on, IR, temperature-programmed desorption of ammonia, Si-29 magic angl e spinning nuclear magnetic resonance and catalytically investigated i n the conversion of methanol to lower alkenes and in the isomerization of n-heptane. The use of ultradispersed SiO2 generated in a capacitiv ely coupled high frequency plasma (CCP) allowed us to synthesize SAPO- 31 molecular sieves of Bronsted acidities which are higher than with s amples based on traditional silicon sources. Results of the conversion of methanol and of the isomerization of n-heptane show that the use o f plasma-chemically generated silica in the synthesis of SAPO type mol ecular sieves can be a way to improve their catalytic properties.