The Research Of Oxidation Of Aldehydes To Carboxylic Acid Under Cu_xO_y/C Catalyst Using H₂O₂ As Oxidant

The transformations of aldehydes to carboxylic acids are important reactions in organic synthesis and fine chemical industry.Benzoic acid and its salts are widely used in medicines,veterinary medicines,industrial raw materials,preservatives for food,cosmetics,resin preparations,plasticizers,dyestuffs,synthetic fibers,and intermediates.Currently,benzoic acid was mainly produced by the traditional oxidation of toluene.Because of hige doses of inorganic strong oxidizer and inorganic salt catalyst caused difficulty of product separating,difficult recycle of catalyst,high energy consumption and serious pollution,efficient and environmentally-friendly catalytic methods become one of the hot spot of current research.This thesis synthesized Cu_xO_y/C catalysts by hydrothermal and heat-treating under argon atmosphere.The main contents of this work are listed as follows:?1?Cu_xO_y/C catalysts are synthesized through hydrothermal and heat-treating under argon atmosphere 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,Ultraviolet visible diffused reflectance spectrum,Fourier transform infrared spectroscopy,scanning electron microscopy and transmission electron microscopy.Results indicated that the copper of prepared Cu_xO_y/C catalysts exist in three forms which are Cu,Cu₂O,CuO.The surface of Cu_xO_y/C samples contain rich oxygen-containing functional groups?such as hydroxyl,carbonyl,carboxyl,etc.?.The SEM analyze shows that Cu_xO_y/C catalysts are carbon microspheres which have smooth surface without cracks and diameter reduced after the heat treatment in argon atmosphere.By TEM,small black particles can be observed within the carbon microspheres.The diameter of particles is about 20-80nm and increased to 50-140 nm after heat treatment in argon atmosphere.?2?The effect of preparation conditions of catalyst?such as hydrothermal temperature and time,the copper precursor,copper loading,heat-treatment temperature and time?on the benzaldehyde oxidation reaction was investigated.The results showed that Cu_xO_y/C?A?-0.37-180?Ar-300 ^?-10h?catalyst exhibits higher catalytic activity.?3?Using acetonitrile as solvent,the starting amount of benzaldehyde and hydrogen peroxide is 1:4?motor ratio?and the amount of catalyst is 0.1g.After reaction at 60 ^?for 5h,the yield of benzoic acid reached 90.6%,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.?4?To explore the range of suitable substrates for this catalytic system,the oxidation of various aldehydes catalyzed by Cu_xO_y/C was investigated.Test results show that benzaldehyde derivatives with an electron-withdrawing groups were more reactive than those with electron-donating groups.Cu/C,Cu₂O/C and CuO/C catalysts are synthesized through impregnation method by using Cu?NO3?2 as copper source and D-fructose as carbon source.The hydrogen peroxide decomposition experiment shows that the decomposition of hydrogen peroxide decreases in following order:CuO/C>Cu/C>Cu₂O/C.The amount of·OH produced on the tested samples decreases in the following order:CuO/C>Cu/C>Cu₂O/C.It can be identified that the active specie of catalysts is CuO.The possible path of the catalytic reaction is the free-radical reaction mechanism.