Characterization of SAPO-11 and SAPO-31 synthesized from aqueous and non-aqueous media

Medium-pore SAPO-11 and SAPO-31 molecular sieves were synthesized from aqueous and non-aqueous (ethylene glycol) media. All the samples were characterized by XRD, SEM, N₂ adsorption (BET analysis), TGA-DTA, pyridine-TPD, ²⁷Al MAS-NMR, and ²⁹Si MAS-NMR. The samples synthesized from non-aqueous medium possess higher acidity due to higher substitution of Si⁴⁺ at P⁵⁺ sites and less silica island formation, as evidenced from ²⁹Si MAS-NMR spectra. It is possible to incorporate more silicon in the samples by synthesis in ethylene glycol medium. The SAPOs synthesized from non-aqueous medium show higher activity for the isomerization of m-xylene.