Preparation Of CuO_x/C Spheres And CuO_x Hollow Nanospheres And Their Application In Benzaldehyde Oxidation Reaction

Benzoic acid as a kind of important organic intermediates,are widely used in medicine,food,dyes,spices,chemical and other fields.The traditional synthesis method of benzoic acid has shortcomings of environmental pollution and difficult to separate recycling.Therefore,researching on green,pollution-free and environment-friendly catalyst become the main task of the current study.This thesis synthesized the catalyst of core-shell structure spherical CuOx/C and hollow spherical CuOx catalyst by hydrothermal combined with different gas(argon gas and air)heat-treating,Selecting benzaldehyde oxidation preparation of benzoic acid by 30%H2O2 as basic reaction test the performance of the catalyst,obtaining benzaldehyde with high yield and selectivity.The main content of this work are listed as follows:(1)CuOx/C catalysts and CuOx catalysts are synthesized through hydrothermal and heat-treating under different atmosphere(argon gas and air)by using Cu(acac)2 as copper source,D-fructose as carbon source.The surface properties and structure of the catalysts were characterized by X-ray photoelectron spectroscopy,X-ray powder diffraction,Fourier transform infrared spectroscopy,scanning electron microscopy and transmission electron microscopy.Results indicated that the hydrothermal synthesis of CuOx/C samples are carbon microspheres of core-shell structure which have smooth surface without cracks and the diameter of particles is about 2-8 ?m.Small black particles can be obviously observed within the carbon microspheres.The diameter of particles is about 20-80 nm and increased to 50-140 nm after heat treatment in argon atmosphere.At the same time a large number of species of copper particles embedded in the carbon microspheres surface,the copper of prepared CuOx/C catalysts exist in three forms which are Cu,Cu2O and CuO.The surface of CuOx/C samples contain rich oxygen-containing functional groups(such as hydroxyl,carbonyl,carboxyl,etc.);After air heat-treating the CuOx samples become hollow ball structure which formed by tightly aggregation of CuOx nanoparticles.By looking at different heat-treating temperature,carbon source and copper precursor finds that the highest activity catalysts are CuOx/C(A)which synthesized through 300? heat-treating under argon gas by using Cu(acac)2 as copper source,D-fructose as carbon source.Using acetonitrile as solvent,the amount of benzaldehyde is 0.5 mL,hydrogen peroxide is 2 mL and the catalyst is 0.1 g.After reaction at 60? for 6 h,the yield of benzoic acid reached 91.7%,the selectivity of benzoic acid is greater than 99%.The catalytic efficiency almost no loss even after 5 repeated cycles.Catalyst can be easily separated from the product after the reaction and recycled.The hollow ball structure CuOx catalysts are synthesized through hydrothermal and heat-treating under air atmosphere by using CuSO4 as copper source,sucrose as carbon source.The surface properties and structure of the catalysts were characterized by X-ray powder diffraction,Fourier transform infrared spectroscopy and scanning electron microscopy.Results indicated that CuO samples are hollow ball structure which formed by tightly aggregation of CuO nanoparticles,the particle size is around 0.5 ?m-0.8 ?m.By looking at different heat-treating temperature,carbon source and copper precursor finds that the highest activity catalysts are CuOx(S)which synthesized through 550? heat-treating under air gas by using CuSO4 as copper source,sucrose as carbon source.Using acetonitrile as solvent,the amount of benzaldehyde is 0.5 mL,hydrogen peroxide is 2 mL and the catalyst is 0.1 g.After reaction at 60? for 3 h,the yield of benzoic acid reached 80%,the selectivity of benzoic acid is greater than 99.4%.Using the CuOx catalyst on the other benzaldehyde oxidation reaction finds that with electron-withdrawing groups on the aromatic ring of benzaldehyde derivatives,the corresponding carboxylic acid yield is very high,and for electron donating group on the aromatic ring of benzaldehyde derivatives,the corresponding carboxylic acid is relatively low.