Hydroisomerization of n-alkanes over Pt-SAPO-11 and Pt-SAPO-31 synthesized from aqueous and nonaqueous media

The acidic and catalytic properties of the medium pore molecular sieves SAPO-11 and SAPO-31 synthesized by two different routes [from aqueous and nonaqueous (ethylene glycol) medial are compared. Samples synthesized from the nonaqueous medium possess more acidity (due to higher substitution of P5+ by Si4+ and consequent lower concentration of silica islands) and larger hydroisomerization activities and selectivities. The molecular sieves, after loading 0.5 wt % Pt, were used as catalysts for isomerization of n-hexane, n-octane, and n-hexadecane. Reactions at the pore mouth at the external surface are more predominant in the case of SAPO-31 than SAPO-11.