Acid properties and morphology of SAPO-11 molecular sieve controled by silica source

Abstract

This paper reports on the control of strong acid sites in SAPO-11 molecular sieve crystals using different silica sources. The crystallization process of the SAPO-11 molecular sieves was performed using silicon sources with different particle sizes, i.e., fumed silica (200 nm), colloidal silica (22 nm), and SiO2 sol prepared by the sol-gel method (4 nm). The SiO2 sol proved to have a significant effect on the acidic properties, morphology and crystal size of SAPO-11 molecular sieve. Moreover, more efficient incorporation of silicon is achieved, providing an increased concentration of acid sites. The SAPO-11 intergrown crystals with a size of 100–300 nm exhibited hierarchical pore structure (SBET – 250 m2/g and Vmeso – 0.27 cm3/g) were synthesized using the SiO2 sol precursor. The SAPO-11 molecular sieves were tested in the reaction of a-methylstyrene dimers synthesis. The SAPO-11 samples, synthesized by SiO2 sol showed the highest monomer conversion and linear dimer selectivity.