Research On The Synthesis And Catalytic Properties Of Silica And Silica Composite Oxide Supported Phosphotungstic Acid

Silica and silica composite oxide supported polyoxometalates were prepared by situ method, impregnation and co-precipitation, and characterized by FT-IR, XRD, PL, TG-DTA, SEM, Zeta potential, UV-vis/DRS and XPS. The catalytic activity of the prepared catalysts were tested through synthesis of 3,4-dihydropyrimidine-2(1H)- one and photodegradation of organic dyes. The specific contents are as follows:3,4-Dihydropyrimidine-2(1H)-one was synthesized from substituted benzaldehyde, urea and ethylacetoacetate using H3PW12O40/Si O2 as a eco-friendly catalyst prepared by a situ method. It was found that H3PW12O40/Si O2 was a good catalyst for synthesis of 3,4-dihydropyrimidine-2(1H)-one. Under the optimum conditions, the yields of 3,4-dihydropyrimidine-2(1H)-one can reach 73.1%~88.4%. The derivatives of 3,4-dihydropyrimidine-2(1H)-one has a certain bacteriostasis. The results also reveal that H3PW12O40/Si O2 has a good stability.H3PW12O40/Ti O2-Si O2 was synthesized by impregnation method. Degradation of methyl violet(MV) was used as a probe reaction to explore the influencing factors on the photodegradation reaction under simulated natural light. The results showed that the optimal conditions were as following: initial concentration of methyl violet 10 mg/L, p H 2.0, catalyst dosage 2.9 g/L, and light irradiation time 2.5 h. Under these conditions, the degradation rate of MV is 99.5 %. The reaction on photodegradation for MV can be expressed as the first-order kinetic model. After used continuously for five times, the catalyst kept the inherent photocatalytic activity for degradation of dyes. The photodegradation of methyl orange, methyl red, naphthol green B, and methylene blue were also tested, and the degradation rate of dyes could reach 81%-100 %.TiO2-SiO2 photocatalysts were successfully synthesized using the sol-gel method, hydro-calcination, co-precipitation and room-temperature solid-phase synthesis technology. Photocatalytic properties of the catalysts was evaluated by the degradation of methyl orange(MO) under simulated natural light, the photocatalytic activity was compared and the optimum conditions have been found. The results revealed that Ti O2-Si O2 with prepared by co-precipitation method is an execellent catalyst for degradation of MO. Under the optimal conditions, the degradation rate of MO was 98.8 %. After used continuously for five times, the degradation rate of MO can reach 81.2 %. The photodegradation of methylene blue, rhodamine B, methyl violet, naphthol green B, basic fuchsin, malachite green and methyl red was also tested, and the degradation rate of dyes can reach over 93.0 %. The photocatalytic activity of H3PW12O40/Ti O2-Si O2 were also tested, the results revealed that there was a synergistic effect between the H3PW12O40 and Ti O2-Si O2.