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Effect of silicon precursor on silicon incorporation in SAPO-11 and their catalytic performance for hydroisomerization of n-octane on Pt-based catalysts

Zhichao Yang,Jilong Li,Yunqi Liu,Chenguang Liu

SAPO-11 molecular sieves were synthesized using silica sol, hydrophilic fumed silica , and tetraethyl orthosilicate (TEOS) as silicon precursors. Their physicochemical properties were characterized using XRD , SEM, nitrogen adsorption-desorption, Py-IR, NH 3 -TPD, EDS, and 27 Al, 31 P, 29 Si MAS NMR techniques. The catalytic performance was assessed in the hydroisomerization of n -octane. The results showed that the silicon precursors influenced the physicochemical properties and catalytic performance of SAPO-11. SAPO-11 synthesized using hydrophilic fumed silica as silicon precursor showed higher silicon distribution and had more medium acid sites. SAPO-11 synthesized using TEOS as silicon precursor had more silicon content , but more silicon islands formed in its framework. The depolymerization of silicon precursors might affect the silicon content and distribution in SAPO-11. In the hydroisomerization of n -octane, the catalytic activity strongly depended on the number of medium acid sites instead of the number of total acid sites. SAPO-11 synthesized using hydrophilic fumed silica as silicon precursor exhibited higher catalytic activity than the other samples because it has more medium acid sites.