Abstract:

SAPO-34 molecular sieve is often used in methanol to olefin（MTO） reaction.Using sodium silicate,aluminum nitrate and ammonia as raw materials,a silicon modified pseudo boehmite was prepared by alkali dropping to acid feeding method,and then SAPO-34 molecular sieve was prepared by hydrothermal synthesis method with silicon modified pseudo boehmite as silicon source and aluminum source,phosphoric acid（H₃PO₄） as phosphorus source,tetraethyl ammonium hydroxide（TEAOH） as template.The synthesized silica modified pseudo boehmite and SAPO-34 molecular sieve were characterized by XRD,SEM,FT-IR and NH₃-TPD,and their MTO catalytic properties were evaluated.The results showed that when the molar ratio of silicon to aluminum was 0.08~0.5,the introduction of silicon had no effect on the synthesis of pure pseudo boehmite,but the amount of silicon had a certain effect on the crystallinity and morphology of pseudo boehmite.When the amount molar ratio of silicon to aluminum was 0.2~0.5,pure SAPO-34 molecular sieve could be synthesized with silicon modified pseudo boehmite as silicon source and aluminum source.The methanol conversion rate of MTO catalytic reaction could reach more than 99%,the diene selectivity could reach more than 87%,and it had high ethylene selectivity.

Key words: silicone modification, pseudo-boehmite, SAPO-34 molecular sieve, MTO