Preparation Of ?-caprolactone By B-V Oxidation Of Cyclohexanone Over Bimetallic Oxide Catalysts

?-Caprolactone is an excellent intermediate in organic synthesis,which has been used in the fields of medicine,environment,chemical industry and so on.Peroxy acid is commonly used to oxidize cyclohexanone to produce ?-caprolactone in industrial production,but it needs to be replaced because of high cost,low yield and risk of raw materials storage.H2O2 and O2/aldehydes are suitable oxidants at present,and it has been an important direction to develop efficient catalysts for improving reaction efficiency.In this paper,the oxidation of cyclohexanone to ?-caprolactone with H2O2 and O2/aldehyde were used as performance evaluation experiments respectively,and the bimetallic oxide catalyst with high catalytic effect on the system was mainly explored.The preparation,characterization,catalytic performance and effects of reaction conditions on the Baeyer-Villiger(B-V)oxidation of cyclohexanone were studied and analyzed.The main conclusions were as follows:First of all,bimetallic oxide catalysts with different molar ratios of magnesium to tin were prepared with Mg(?)and Sn(?)as active centers,the optimum molar ratio was 2:1.The template modifi ed catalyst Mg0.67Sn0.33-N-T and Mg0.67Sn0.33-N/Na-T(H)with different templates was obtained by coprecipitation and hydrothermal method,respectively.The results of X-ray-diffraction(XRD),scanning electron microscope(SEM)and N2 adsorption-desorption,showed that templates can improve the stability of the catalyst by affecting the structural properties such as morphology,crystal phase and specific surface area of the catalyst.Mg0.67Sn0.33-N-CTAC showed best catalytic performance and less recovery loss in the oxidation of cyclohexanone.The optimized reaction conditions were as follows:catalyst 0.28 g,cyclohexanone 12 mmol,96 mmol H2O2(30wt%),acetonitrile 10 mL,75?,6 h,the conversion of cyclohexanone was 89.92%,and the selectivity of ?-caprolactone was 91.20%.Secondly,through the oxidation of cyclohexanone with O2/benzaldehyde,Ce and Fe were selected as the suitable catalytic centers from a variety of monometallic,bimetallic oxides and molecular sieve supported catalysts;Taking the molar ratio of Ce to Fe at 3:1,the different properties of the catalysts prepared by coprecipitation,sol-gel,hydrogen reduction and direct mixed combustion method were studied;A series of catalysts Ce/Fe(a:b)-600 with diffierent molar ratio of Ce to Fe were obtained,the optimum ratio was 2:1 according to experiments;Catalysts Ce/Fe(2:1)-T was prepared at different calcination temperature,it was found that there was a synergistic effect between CeO2 and Fe2O3 combined with the characterization results of XRD,N2 adsorption-desorption and X-ray photoelectron spectroscopy(XPS).Ce/Fe(2:1)-500 had the highest surface oxygen concentration,which was beneficial to activation of benzaldehyde and cyclohexanone,showing the best catalytic performance.The optimum reaction conditions were as follows:catalyst 50 mg,cyclohexanone 12 mmol,benzaldehyde 24 mmol,O2 10 mL/min,1,2-dichloroethane(DCE)20mL,reaction temperature 45?,reaction time 4 h,conversion of cyclohexanone 99.20%,selectivity of ?-caprolactone 99.93%,the conversion of benzaldehyde was 97.22%and the selectivity of benzoic acid was 99.32%.There was no obvious change in the activity of the catalyst when it was recycled for 4 times.Then,the above catalyst Ce/Fe(a:b)-600 and Ce/Fe(1:1)-T was used to catalyze the oxidation of cyclohexanone to ?-caprolactone with O2/isobutyraldehyde,Ce/Fe(1:1)-500 was selected as the optimum catalyst.The effects of the amount of catalyst,reaction temperature,reaction time and the ratio of aldehyde to ketone were investigated and suitable reaction conditions are as follows:catalyst 50 mg,cyclohexanone 12 mmol,isobutyraldehyde 18 mmol,O2 15 mL/min,DCE 15 mL,reaction temperature 45?,reaction time 1.5 h.The conversion of cyclohexanone and isobutyraldehyde was 35.60%and 99.94%,the selectivity of ?-caprolactone and isobutyric acid was 99.91%and 91.90%.Finally,the scale-up design of the oxygen/isobutyraldehyde co-oxidation of cyclohexanone to ?-caprolactone with an output of 1000 t/a was proposed,which can provide some reference for the actual production design in the future.