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

Abstract

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.

Stable and Efficient Cu‐Based Zeolitic Octahedral Metal Oxides for Ethylene and Ethane Separation at High Temperature and Humidity

“…Powder X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were shown in Figure S1 (Supporting Information). The characteristic XRD and FTIR peaks of Cu-VT-1 were the same as the reported VT-1, [8] which demonstrated that the crystal structures and structures of the cubane unit did not change. The results indicated that the incorporation of Cu did not damage the structure of the material.…”

“…Elemental analysis showed that the mole ratio of W/V/Cu = 4/3/1. [8] Combined with elemental anal-ysis and valence analysis, the chemical formula of Cu-VT-1 was Cu I 0.54 Cu II 0.46 [W VI 4 V IV 1.72 V V 1.28 O 19.37 ]. For comparison with Cu-VT-1, the other cations incorporated VT-1s were synthesized.…”

“…A recent progress of inorganic order microporous materials is zeolitic transition metal oxides that are mainly based on metal‐oxygen octahedra, so‐called zeolitic octahedral metal oxides (ZOMOs). Different ZOMOs have been synthesized for molecule adsorption and separation, including cubane unit‐based ZOMOs [ 7 ] for C 3 H 6 /C 3 H 8 [ 8 ] and nC 4 H 10 /iC 4 H 10 separations, [ 9 ] ε ‐Keggin unit‐based ZOMOs [ 10 ] for C 2 H 2 /CO 2 , [ 11 ] C 2 H 4 /C 2 H 6 , [ 12 ] and CO 2 /CH 4 separations. [ 13 ] Among them, cubane unit‐based ZOMOs are interesting.…”

“…[ 7 ] The stable framework of VT‐1 allows it to be applicable to the gas separation at high temperature and humidity. [ 8 ] However, the pore size of the material is larger than the size of C 2 H 6 and C 2 H 4 , which drawbacks the material from separating C 2 H 4 /C 2 H 6 . The previous studies have shown that Cu + can act as a metal center that selectively interacts with C 2 H 4 , thereby improving the separation performance of C 2 H 4 /C 2 H 6 .…”

“…Herein, the incorporation of Cu as the cation of VT‐1 by a redox reaction during the ion‐exchange with VT‐1 , [ 8 ] and the resulting material was denoted as Cu‐VT‐1 . Ideal solution adsorption theory (IAST) [ 14 ] selectivity, calculated based on single gas adsorption isotherms, demonstrated that Cu‐VT‐1 exhibited significantly higher selectivity for C 2 H 4 /C 2 H 6 compared to VT‐1 s with other cations.…”