Phase transformation and morphology control of zeolite LZ-277 with alkaline media in Na2O–Al2O3–SiO2–H2O system

• Pure zeolite LZ-277 with uniformly desert rose-like morphology was synthesized.
• Influence of pH value on structural transformation of phi-type zeolite was obvious.
• Zeolite LZ-277 showed a certain hygroscopic performance and NH4+-exchanged property.

Zeolite LZ-277 has been synthesized from inorganic gel system via a hydrothermal method involving structure-directing agents. The structural features and textural properties of the obtained samples were extensively characterized using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence (XRF), N2 adsorption–desorption isotherms and thermogravimetric analysis/differential thermal analysis (TGA/DTA) techniques. In an effort to obtain pure zeolite LZ-277 with desert rose-like spherical morphology, we have systematically investigated the influence of pH value of starting gel on the crystallization performance. It was found that the amorphous phase, formed under low alkalinity conditions, could be transformed to pure zeolite LZ-277 by increasing the pH value of the starting gel to 11.8. However, an additional phase of FAU-type zeolite was generated when the pH value was increased to 12.8, and the sodalite crystal structure was eventually produced when the pH value reached 13.3. In addition, in order to evaluate its potential application, the thermostability of ammonium-exchanged LZ-277 was preliminary investigated using ion exchange methods, XRD, TEM and TGA/DTA analyses.

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