Controlled synthesis of hierarchically porous SAPO-34 zeolites with tailored crystal size and morphology.

A series of hierarchical SAPO-34 zeolites with controllable crystallite sizes ranging from 40 to 200 nm and morphologies from well-dispered urtral-small nanocrystals to compact spherical-like polycrystallite aggregates were fabricated by only modulating the Si/TEAOH molar ratios in the gel mixture. [Display omitted] • Hierarchical SAPO-34 zeolites are synthesized without a secondary template. • A possible forming mechanism of SAPO-34 zeolite is proposed. • Crystal sizes and morphologies can be well modulated by controlling Si/TEAOH molar ratios. • The rich mesopore structure resulted from the intercrystal pores of nanoparticles is fabricated. A series of hierarchically porous SAPO-34 zeolites with tunable crystal sizes varying from 40 to 200 nm were synthesized with different morphologies from well-dispersed ultra-small nanocrystals to compact spherical-like polycrystalline aggregates by only changing the Si/TEAOH (TEAOH: tetraethylammonium hydroxide) molar ratios in the gel precursors without using any meso -templates. The hierarchical samples were systematically characterized by XRD, FT-IR, SEM, TEM, XRF, 29Si MAS NMR spectra and N 2 adsorption–desorption. It reveals that hierarchical SAPO-34 nanocrystals with high crystallinities, larger external surface areas (61 – 125 m2/g) and mesopore volumes (0.15 – 0.29 cm3/g) were obtained under current synthesis condition. [ABSTRACT FROM AUTHOR]