Manipulation of the crystallization of SSZ-13 transformed from coal fly ash-derived analcime.

Interzeolite transformation (IZT) has been used to produce zeolite with novel structure and composition. However, the complicated interactions between synthesis parameters and the resultant zeolites remained ambiguous. Herein, we synthesized zeolite SSZ-13 via an IZT strategy by using coal fly ash-derived analcime as parent zeolite. The effects of feeding H 2 O/SiO 2 , OH-/SiO 2 , and SiO 2 /Al 2 O 3 ratios on the crystallization of zeolite SSZ-13 were examined. The crystallinity, pore structure, building units, and chemical environment of the products were investigated by XRD, SEM, XRF, N 2 adsorption-desorption, FT-IR, and NMR, respectively. Zeolite SSZ-13 with high crystallinity and regular pore structure can be obtained under feeding H 2 O/SiO 2 ratios of 17.5–25, OH-/SiO 2 ratios of 0.2–0.6, and Al 2 O 3 /SiO 2 ratios of 30–40. The absence of external water limited the mass transfer between reactants. While excessive water lessened the driving force for synthesizing zeolite SSZ-13 with regular structure. Small amounts of OH- ions triggered the dissociation of zeolite analcime. But high concentrations of OH- ions blocked the condensation of Si reactants and nucleation of zeolite SSZ-13. Increasing SiO 2 /Al 2 O 3 ratio boosted the nucleation frequency. Insufficient contents of external Si species delayed nucleation and formed amorphous aluminosilicate impurities. The superfluous SiO 2 /Al 2 O 3 ratio caused the overgrowth of zeolite SSZ-13 with irregular structures. Our findings benefited in understanding the interaction among synthesis parameters and the crystallization mechanism of IZT. It also gained new strategies for synthesizing high-silica zeolite using Al-rich natural and industrial aluminosilicate solid wastes. [Display omitted] • Zeolite SSZ-13 was synthesized transforming from coal fly ash-derived analcime. • Effects of H 2 O/SiO 2 , OH−/SiO 2 , and SiO 2 /Al 2 O 3 ratios on SSZ-13 were examined. • Added water determined mass transfer of reactants and crystallization driving force. • OH− ions triggered dissociation of analcime but inhibited nucleation of SSZ-13. • High Si contents boosted nucleation frequency but impacted product purity. [ABSTRACT FROM AUTHOR]