Synthesis, Characterization and Hydroisomerization Performance of SAPO-11 Molecular Sieves with Caverns by Polymer Spheres

Abstract

Silicoaluminophosphates SAPO-11 molecular sieves with caverns were synthesized using polystyrene (PS) micro-spheres as template. The morphologies of the cavitary SAPO-11 molecular sieves exhibit spherical particles ranging 7–10 μm aggregated from cubic plate microcrystallites which just like the SAPO-11 molecular sieves synthesized with the conventional method, but some caverns of 500–1,200 nm pore size in diameter can be observed on the former material. The strength and distribution of the acid sites of the cavitary SAPO-11 are similar to that of the conventional SAPO-11, but the acid density is slightly low owing to the decreased crystallinity of the cavitary SAPO-11. The micropores size and mesopores size of the conventional SAPO-11 are centered at about 0.45 and 3.8 nm, respectively, while the cavitary SAPO-11 has, in addition to the micropores and mesopores, large mesopores ranging 5–30 nm and macropores ranging from about 100 to 1,200 nm, which were derived from the PS sphere template. Hydroisomerization of n-hexadecane was performed to investigate the catalytic performance of the cavitary SAPO-11. The result showed that, in comparison with the conventional SAPO-11, the cavitary SAPO-11 has high activity based on per active site and high selectivity, owing to the fast diffusion of the reactant and isomer products inside the catalyst.