Green synthesis of SUZ-4 zeolite controllable in morphology and SiO2/Al2O3 ratio

• A strategy for the green synthesis of SUZ-4 with controllable morphology and Si/Al was proposed.
• High-silica SUZ-4 zeolite with Si/Al ratio as high as 9 was obtained for the first time.
• The crystallization time for obtaining the 100% SUZ-4 at 150 °C was shortened to 12 h from 96 h.
• The crystallization temperature for obtaining SUZ-4 zeolite could be lowered to 90 °C from 150 °C.

The influence of chemical composition of initial gel on the crystallization kinetic, product yield, particularly, on the morphology and SiO2/Al2O3 ratio of zeolite was investigated for the SUZ-4 zeolite synthesis with the assistance of seed slurry. It was found that the SiO2/Al2O3 ratio and morphology of the SUZ-4 zeolite can be controlled by manipulating the H2O content, SiO2/Al2O3 ratio, and K+ content of the initial gel. The crystallization time for obtaining the 100% SUZ-4 zeolite was shortened to 12 h from 96 h at 150 °C for the first time by reducing the H2O content in the gel. It was found that coexistence of Na+ with K+ in the gel does not influence the SUZ-4 zeolite synthesis, while only K+ can incorporate into the SUZ-4 framework. The SUZ-4 zeolite with the SiO2/Al2O3 ratio as high as 18.0 was obtained by decreasing K+ content and increasing SiO2/Al2O3 ratio of the gel with the assistance of seed slurry. Well-crystalline SUZ-4 was obtained in the synthesis recycling 100% mother liquid. As the mother liquid produced from each batch of synthesis was not changed in amount, a possible green process of SUZ-4 synthesis in industry was proposed.

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