The Preparation And Properties Of Supported Cu-Co Spinel Compound Oxides Catalysts

N-butylaldehyde can be applied to resin,plasticizer and pesticides,et al.The production of butylaldehyde is mainly from the propylene carbonyl synthesis method which shows a moderate reaction condition and the catalyst can be easily separated.However,the commonly used rhodium catalyst is expensive and the ligand is toxic,which is harmful to human health.The catalytic oxidation reaction is conducted under atmospheric pressure and the reaction process is simple with less pollution.Moreover,the facile separation process of the product and the high utilization of the raw material make it arouse much attention in the academic community.In this study,the transition metal composite oxide prepared from an impregnation method was used as the catalyst for the catalytic oxidation.1.Catalysts Preparation and CharacterizationIn this paper Co based spinel type oxide catalysts were synthesized after the impregnation,resting,filtration,drying and calcination process with Al2O3,SiO2,Si-Al as the support and Cu(NO3)2.Co(NO3)2 as the metal source.The support of Alumina and Silica were commercially available while the Si-Al composite oxide were self-made.The catalyst samples were characterized by XRD,FT-IR,UV-vis and XPS techniques.1.The Co based spinel type oxide catalysts were synthesized with Al2O3、SiO2 and Si-Al as the support.The XRD showed that Cu-Co oxides formed spinel structure and part of Cu2+formed the CuCo2O4 spinel structure and the other part of Cu2+ formed CuO.Co based spinel type oxide catalysts were synthesized after calcinations at 550℃ with Si-Al composite oxides as the support calcinated at 450℃～600℃.The XRD diffraction intensity was the strongest.2.FT-IR showed that there were twe characteristic absorption peaks between 500-800cm-1 on the Cu-Co composite oxide catalysts formed by the three carrier which were respectively located in the spinel compound Co-O-Co and the Cu-O-Co of the bending vibration.With the calcination temperature rising,the vibration of the Co-O key moved to the high wavenumber due to bonding ability of metal oxide key became strong and key force constant larger.3.UV-vis showed that the two packages absorption peak appeared between 400-800nm respectively around 450nm and 700nm on the CuCo2O4 wiith Si-Al as support at different calcination temperatures.With the calcination temperature rising,red shift of absorption peaks appeared.Eectrons were transferred through the metal particles to the surface of the particles,resulting in metal particles surface electron density decreased.UV-vis showed the same results when catalysts calcinated at different temperatures.4.XPS showed that the peak appeared around 783 eV,934eV on the surface of CUCo2O4/Si-Al which were the characteristic peaks of CuCo2O4.The binding energy of Co 2P3/2 and Cu 2P3/2 were 782.9eV and 934.1eV.The electronic binding energy of O1S was 531eV in composite oxides.The CuCo2O4 surface kept spinel structure,and Co、Cu binding energy barely changed at different calcination temperatures.The O 1S changed a lot,there were three forms at 500℃and 550℃,four forms at 600℃.2.Catalytic Activity ResearchIn this study,we investigated the effect of different supports,catalyst preparation process and reaction process on the oxidation of n-butyraldehyde catalyzed by butanol with CuCo2O4 as catalyst in a fixed-bed reactor.1.The effect of different reaction time and temperature on the oxidation of n-butyraldehyde catalyzed by butanol with CUCo2O4/Al2O3,CUCo2O4/SiO2 as catalysts were systematically investigated.The conversion rate was 75.5%and the selectivity was 79.6%using CUCo2O4/Al2O3 as the catalyst when the reaction temperature was 380℃,the speed was 0.5h-1 and the ratio between oxygen and butanol was 0.5.At the same reaction condition,the conversion was 68.1%and the selectivity was 78%with CUCo2O4/SiO2 as the catalyst(the reaction average time was 6h-1).2.The effect of calcination temperature and the reaction temperature on the oxidation of n-butyraldehyde catalyzed by butanol used the CuCo2O4/Si-Al were investigated.The results showed that the catalytic performance of CUCo2O4/Si-Al catalyst calcined at 600℃ was the best with Si-Al composite oxide calcined at 550℃,when the reaction temperature was 340℃,the conversion of butanol was 96.5%,the selectivity of n-butyraldehyde was 73.2%with the speed 0.5 h-1 and the ratio between oxygen and butanol 0.5(the reaction average time was 6h-1).3.The CuCo2O4/Si-Al was formed after different calcination temperature of supports.With calcination temperature varing,the selectivity varied.As the calcination temperature increased,the selectivity increased at 450℃～550℃.When the calcination temperature exceeded 550℃,the selectivity decreased.The XPS infered that the new 0 lead to oxidative ability enhanced,n-butyraldehyde became n-butyric acid;so the selectivity decreased.