SAPO-11, SAPO-31, and SAPO-41 Molecular Sieves: Synthesis, Characterization, and Catalytic Properties inn-Octane Hydroisomerization☆

Abstract Large-pore SAPO-5 and medium-pore SAPO-11, SAPO-31, and SAPO-41 have been synthesized using a hydrothermal method. These catalysts were characterized by chemical analysis, XRD, SEM, IR, TPD of NH 3 , and MAS NMR; Pt dispersion was measured by H 2 adsorption. n -Octane hydroconversion over the Pt–SAPO catalysts has been tested. High selectivity for n -octane isomerization has been observed on medium-pore Pt–SAPO-11, -31, and -41, while preferential hydrocracking has been found for large-pore Pt–SAPO-5. Isomerization products consisted of monobranched isomers with a negligible amount of dibranched isomers. Interestingly, among the medium-pore SAPOs, SAPO-41 exhibits the highest isomerization selectivity. The selectivity decreases in the order SAPO-41 > SAPO-31 > SAPO-11. The differences in isomerization selectivities of the SAPOs are explained by considering diffusional restriction and steric constraints, SAPO-41 channel dimensions adequately fitting the dimensions of the monobranched isomers.

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