Improvement of catalytic properties of SAPO-31 molecular sieves by using an activated form of Si0 2

Abstract

SAPO-31 molecular sieves the synthesis of which is based on different types of SiO 2 were physicochemically characterized by X-ray diffraction, IR, temperature-programmed desorption of ammonia, 29Si magic angle spinning nuclear magnetic resonance and catalytically investigated in the conversion of methanol to lower alkenes and in the isomerization of n-heptane. The use of ultradispersed SiO 2 generated in a capacitively coupled high frequency plasma (CCP) allowed us to synthesize SAPO-31 molecular sieves of Brønsted acidities which are higher than with samples based on traditional silicon sources. Results of the conversion of methanol and of the isomerization of n-heptane show that the use of plasma-chemically generated silica in the synthesis of SAPO type molecular sieves can be a way to improve their catalytic properties.