The Polymetallic Pom / Zirconia Composite Catalysts Preparation And Characterization Of,

Two types of Zirconia-supported the POM-containing microporous materials and composite films such as PWi2/ZrO2, PW11Ti/ZrO2 PW10Ti2/ZrO2,PW12/ZrO2,PW4O2/Zr02 and PW11TiO2/ZrO2were prepared by the method of sol-gel via spin-coating, calcination and rogrammed temperature solvothermal reaction techniques. Otherwise, colored N-containing ZrO2 powders with high surface area were synthesized by Spray pyrolysis. Retention of the structure integrity of the starting POMs in the as-synthesized composites was confirmed by UV/DRS, FT-IR, solid state NMR and ICP-AES. Also it was shown from the results that the strong chemical interactions between POM molecules and zirconia networks existed in the composites. Nitrogen doped into substitutional sites of ZrO2 has proven to be indispensable for band-gap narrowing. The introduction of nitrogen atoms does not change the ZrO2 crystal structure. The surface morphology of the composite films was confirmed by the SEM measurements. Indicating that microporous materials have well distributed porous channel, and the average pore sizes are 0.60 ~ 0.70 nm. The films are smooth and the thickness of the films is 200 nm. The particles of ZrO2-xNx were maintained the three-dimensional spherical nature with an average diameter of ca. 15 ~ 30 nm.Under UV-irradiation of the PWi2-nTin/ZrO2 microporous composites, all as-synthesized composites exhibited high photocatalytic activity on the degradation of dye naphthol blue black (NBB). It has been shown that aqueous NBB can be complete mineralized into CO2-. H2O and inorganic ions. The photocatalytic reactions followed Langmuir-Hinshelwood first-order kinetics. Little leakage of the POM from the zirconia matrix was owing to strong chemical interactions between the POM molecules and zirconia matrix. The results indicate that the zirconia composites based onTi-substituted Keggin-type polyoxometalates is stable.The photocatalytic activities of the POMs/ZrOi composite fihns were tested via degradation of aqueous Reactive Brilliant Red K-2G (K-2G) under visible light irradiation. It was observed that the visible-light photocatalytic activities of the three composite films are much high, mainly attributed to (i) the higher oxidizing ability of the peroxo POM anions; (ii) with visible light excitation of adsorbed dye K-2G, electron transfer from the excited dye to the LUMO of the POMs occurs and subsequent transformation of K-2G cation radical is possible. The dye K-2G can be effective degraded by sensitized photocatalysis; (iii) optical absorption spectra show that the POMs/ZrO2 composite fihns noticeably absorb the light at less than 500 nm. The leakage of the active component from the films was hardly observed during the degradation reaction, indicating that the as-synthesized composite fihns were stable, and they are more easily handled than that of the powdered photocatalytic materials, therefore, as-synthesized film exhibits the potential for practical applications.To use solar irradiation or ulterior lighting efficiently, we sought a photocatalyst with high reactivity under visible light. Powders of ZrO2-xNx have revealed an improvement over zirconia (ZrO2) under visible light (wavelength, 430 nanometers) in optical absorption and photocatalytic activity such as photodegradations of Ractive blue 5 (RB5). Nitrogen doped into substitutional sites of ZrO2 has proven to be indispensable for band-gap narrowing and photocatalytic activity.The PWi2/ZrO2 composites contained both Bronsted and Lewis acid sites. Selective synthesis of dimethyl carbonate (DMC) from methanol and CO2 was investigated in the presence of H3PW12OWZrO2 catalysts under mild conditions. The effects such as the amount of catalysts, reaction temperature and C pressure on the DMC formation were studied, indicting that the catalytic activity depend strongly on the CC>2 pressure.ivWhen the reaction was carried out at various pressure of CC>2, two maxima in DMC synthesis were observed at 4 and 7.6 MPa, and the byproducts such as dimethyl ether and CO were hardly detected. Br0nst...