The Preparation Of Metal Oxide Composite Catalyst And Its Catalytic Performance

In this paper,the preparation process of metal oxide catalyst because its complication,harsh reaction conditions,low yield,not suitable for industrial production was improved,and the method of adding some of precious metals and a variety of metal oxide semiconductor compound was used to improve its catalytic performance.Using acetic acid zinc,silver nitrate and bismuth nitrate and bismuth nitrate as raw material,citric acid as complesing agent,the precursor was obtained,and through the method of chemical precipitation to get the Ag/ZnO-Bi₂O₃,Ag/ZnO,Ag/Bi₂O₃,Bi₂O₃/ZnO four kinds of composite metal oxide catalysts,through some means including X-ray diffraction?XRD?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,N2adsorption-desorption and ultraviolet-visible diffuse reflection spectrum?Uv-vis?,the crystal structure,morphology,specific surface area and optical property of products were characterized,the catalytic ability to photocatalytic degradation of organic dye waste water and catalytic aldol condensation reaction was also studied.Different raw material ratio of Ag/ZnO-Bi₂O₃ composite catalyst were prepared in this paper,we can find elemental silver grain,zinc oxide block crystals,bismuth oxide wafer structure respectively by the scanning electron microscopy?SEM?and transmission electron microscopy?TEM?analysis,which is suitable for large lump crystal ZnO morphology,and Ag grain and Bi₂O₃ chip is much evenly dispersed on the surface of ZnO crystal,the composite result is good.Using Ag and Bi₂O₃ on modification of ZnO,the forbidden band width of the ZnO is reduced effectively,and it makes the spectral response range extension to 423 nm,At the same time,the ultraviolet absorption of this Ag /ZnO-Bi₂O₃ composite catalyst in the230-400 nm is enhanced.Photocatalytic experiment results show that the modified composite catalyst has the most highest catalytic efficiency under the ltraviolet light conditions when the mole ratio of raw material for zinc acetate:bisimuth nitrate:silver nitrate is 1:0.1:0.25,it can be effective to the degradation of methyl orange organic pollutant,the degradation rate can reach more than 95%only in 2.5h;Adding the hydrogen peroxide solution which the volume concentration is 0.091 as the electron capture agent and it can produce synergy effect with Ag/ZnO-Bi₂O₃ compositecatalyst,the oxidation of organic pollutant can be more effectively,the fully degradation time can be reduced to 2 hours.Under the visible light,the Ag/ZnO-Bi₂O₃ composite catalyst degradation rate of Rhodamin B solution which the concentration of 20mg/L was 97.6% in1.5h,when the time was added to 2.5h,the basic degradation of Rhodamine B is 99.8%,the effect is significantly described that the modified composite catalyst has higher catalytic efficiency in the visible light at the same time;Attending to the same degradation time?1.5h?of Rhodamine B solution with the Ag/ZnO composite catalyst,the degradation rate was 99.9%,it was tend to degradation completely;when the Ag/Bi₂O₃ reaction time was to 4h,the degradation rate was 98.7%,and continue to extend the degradation time,the degradation rate of change was not obvious;Bi₂O₃/ZnO composite catalyst degradation rate was faster,when the reaction time was 30 min,the degradation rate has reached 97.99%.Abore all,using Ag and Bi₂O₃ on the modification of ZnO can effectively enhanced the intensity of the spectral response,and it can improve its photocatalytic efficiency.Metal oxide catalysts were used for catalytic synthesis of chalcone experiment,the result showed that Bi₂O₃/ZnO can effectively reduce the by-products of the reaction,and improved the production rate of chalcone.When the amount of catalyst was 8.8%,the reaction time was2 h,the chalcone yield was 92.5%,and the catalyst has a good stability,it can be used more than 3 times repeatedly.