Influence of phosphorus and water contents on synthesis of SAPO-34 molecular sieve

SAPO-34 molecular sieves with different P and H2O contents were synthesized by adjusting P2O5/Al2O3 and H2O/Al2O3 molar ratios in starting gel. Differerent characterization methods such as XRD, SEM, ICP, and FTIR were used. The Morphology, crystallinity, and acidity of SAPO-34 materials varied with P2O5/Al2O3 and H2O/Al2O3 molar ratios in the starting gel and different Si substitution mechanisms were carried out correspondingly. Samples with P2O5/Al2O3 and H2O/Al2O3 molar ratios of 1 and 55 had the best crystallinity with the largest crystals and maximum surface area. FTIR results showed that the concentration of strong acidic hydroxyl groups for samples SP-1 and SW-55 were increased. This indicates the presence of a higher amount of Bronsted acid sites.

Keywords:

Crystallinity , Crystal size , Morphology , Bronsted acid site , Surface area