The nanoporous-like title compound is precipitated by addition of KCl to an aq. HCl solution of K8[SiW11O39] and NaVO3 and characterized by EDS, single crystal XRD, UV/Vis, IR, and Raman spectroscopy, and 1 H, 51 V, and 29 S solid state NMR spectroscopy. K3(H2O)4[H2SiVW11O40](H2O)8+x crystallizes in the hexagonal space group P62 with Z = 3 and contains large water-filled channels. A uniform distribution of vanadium over the 12 metal sites of the α-Keggin anion is observed. -(DE PAIVA FLORO BONFIM, R.; DE MOURA, L. C.; PIZZALA, H.; CALDARELLI, S.; PAUL, S.; EON*, J. G.; MENTRE, O.; CAPRON, M.; DELEVOYE, L.; PAYEN, E.; Inorg. Chem. 46 (2007) 18, 7371-7377; Inst. Quim., Univ. Fed. Rio de Janeiro,
Membrane separation technology has been recently attracted more attention as an option for gas separations due to its compact system, ease of operation and low power consumption. In this study, polymer membranes with different percentages of polyurethane were synthesized and submitted to permeability and selectivity tests for the following gases, CO2, N2, O2 and CH4, at two pressures of 4 and 8 bar and at room temperature. The membranes were characterized by FTIR-ATR, Scanning electron microscope (SEM), Thermogravimetric analysis (TGA) and X-ray diffractometer (XRD). At low pressure of 4 bar and room temperature, the membrane with low percentage of PU, 10 %, presented the higher selectivity to CO2 in relation to both N2 and CH4. The same behavior was observed at a high pressure of 8 bar, with higher selectivity to CO2 in relation to all studied gases, N2, O2 and CH4, compared to the already analogous reported membranes submitted at greater pressures.
Single crystals of the potassium salt K3(H2O)4[H2SiVW11O40](H2O)8+x of the vanadium monosubstituted alpha-Keggin dodecatunsgstosilicate were grown from an aqueous solution and analyzed by EDS, XRD, vibration and electronic spectroscopy, and 1H, 51V, and 29Si solid-state NMR spectroscopy. Results indicate the formation of a nanoporous-like compound of hexagonal symmetry (space group P62) with large, water-filled channels running along the c axis. A uniform distribution of vanadium over the 12 metal sites of the alpha-Keggin anion is observed by XRD. Two different neighborhoods were characterized by 51V NMR in a 2:1 ratio (deltaiso=-546.3 and -536.2 ppm), in accordance with a difference in the number of potassium ions in the second coordination shell of vanadium.
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