Eco-friendly synthesis of hierarchical SAPO-11 with fluoride ions for hydroisomerization of n- hexane

Abstract

To increase the yield of iso-hexane and inhibit cracking of isomers in hydroisomerization of n-hexane, hierarchical SAPO-11 was employed to prepare Pt/SAPO-11 catalysts. Hierarchical SAPO-11 was prepared with fluoride ions via an eco-friendly grinding synthesis method. Fluoride ions incorporate into zeolitic framework to form T-F (T = Al and Si) bonds and inhibit the isomorphous substitution of silicon atoms. It endows SAPO-11 intra- and inter-crystalline mesopores and decreases the amount of acid sites. A low diffusion resistance and decreased acidity of catalysts are unfavorable for a subsequent isomerization and cracking of mono-branched iso-hexane. Compared to microporous SAPO-11, catalysts with hierarchical SAPO-11 have a higher selectivity of iso-hexane at a similar conversion. It is reflected as comparable TOF n-C6 = 21.3 h −1 and TOF iso-C6 = 19.9 h −1 . Results above propose a facile and green approach to prepare SAPO-11 molecular sieves. The in-situ regulation method of Pt/SAPO-11 is a reference for other types of SAPO supported catalysts. • The regulation of Pt/SAPO-11 catalysts is achieved with fluoride ions. •Interaction between fluoride ions and zeolitic atoms is investigated. •Fluoride ions introduce mesopores and decrease the particle size of Pt in hydroisomerization catalysts.