Investigation of the Synthesis of Zeolitic Vanadotungstate and its Use in the Separation of Propylene/Propane at High Temperature and Humidity.

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.

Assembly of ϵ-Keggin Polyoxometalate from Molecular Crystal to Zeolitic Octahedral Metal Oxide.

Zeolitic octahedral metal oxides are inorganic crystalline microporous materials with adsorption and redox properties. New ϵ-Keggin nickel molybdate-based zeolitic octahedral metal oxides have been synthesized. 31 P NMR spectroscopy shows that reduction of MoVI -based molybdates forms an ϵ-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 ϵ-Keggin polyoxometalate molecule. The synthesized zeolitic nickel molybdate with Na+ is used as the adsorbent, which effectively separates C2 hydrocarbon mixtures.