Synthetic
conditions for the zeolitic octahedral metal oxide based
on vanadotungstate are studied. The temperature, time, acidity, W/V ratio, cation species, and concentration
affect the resulting materials. The study shows that mixing tungstate
and VO2+ in an aqueous solution generates cubane units
([W4O16]8–) at room temperature.
The cubane units assemble with VO2+ immediately to form
a solid with an amorphous phase and nonporosity, which further crystallizes
under a hydrothermal condition to form the crystalline microporous
vanadotungstate. The zeolitic vanadotungstates act as effective adsorbents
for the separation of propylene/propane. The active materials effectively
separate propylene/propane even at high temperatures and high humidities.
Tuning microporosity of crystalline microporous materials is critical for achieving good application performance. Zeolitic ironmolybdate shows both redox property and microporosity, and a redox-triggered microporosity change is investigated. The micropore...
Zeolitic octahedral metal oxides are inorganic crystalline microporous materials with adsorption and redox properties. New ɛ-Keggin nickel molybdate-based zeolitic octahedral metal oxides have been synthesized. 31 P NMR spectroscopy shows that reduction of Mo VI -based molybdates forms an ɛ-Keggin polyoxometalate that immediately transfers to the solid phase. Investigation of the formation process indicates that a low Ni concentration, insoluble reducing agent, and long synthesis time are the critical factors for obtaining the zeolite octahedral metal oxides rather than the ɛ-Keggin polyoxometalate molecule. The synthesized zeolitic nickel molybdate with Na + is used as the adsorbent, which effectively separates C 2 hydrocarbon mixtures.
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