Cyclohexene Epoxidation Using Molecular Oxygen Over Supported Polyoxometalate Hybrid Catalyst And Conception Design Of The Process

As the product of cyclohexene epoxidation,cyclohexene oxide is an important intermediate in organic synthesis and commonly used in pharmaceutical,pesticide,dyestuff and perfume industries.Epoxidation of cyclohexene with hydrogen peroxide or tert-butyl hydrogen peroxide(TBHP)is one of the most extensively studied synthetic routes of cyclohexene oxide in recent years.In addition,solvents and co-reductant will be added to improve the selectivity and conversion of cyclohexene oxide in many researches,but these methods have no advantages in materials cost,storage safety and separation of production.Relatively speaking,epoxidation of cyclohexene with molecular oxygen has the advantages of low production cost,high storage safety and high utilization ratio of atoms,which is an important research direction of green selective oxidation industry in the future.However,the selectivity and conversion of molecular oxygen epoxidation of cyclohexene are not very high,so it is extremely urgent to develop the catalysts with high catalytic activity.This paper will take the reaction of cyclohexene epoxidation with molecular oxygen under solvent-free conditions as research object.It focuses on the preparation,characterization and catalytic performance of the supported polyoxometalate hybrid catalyst.Outlined as follows:Firstly,experiments chose polyoxometalate PMo11 and nano-gold as the active center,ZSM-5,SBA-15,MCM-41,ZSM-11,Mordenite,Al2O3 and activated carbon as supports,and prepared catalysts for epoxidation of cyclohexene by impregnation reduction method(for nano-Au)and mixing method or impregnation method(for PMo11).The result showed that,the catalyst prepared by mixing method(for PMo11)and using ZSM-5 zeolite modified by NaOH solution of 0.4 mol/L as support had better effect.The optimum loading content of PMo11 was 6.67%,and the addition of TBHP could increase the epoxidation effect significantly.The reaction conditions were:the catalyst was 1%Au/PMo11/ZSM-5-M(modified)0.4,the amount of addition 0.02 g,2.0 g of cyclohexene,3 drops of TBHP,the reaction pressure 0.8 MPa,the reaction temperature 80? and the reaction time 18 h.The conversion of cyclohexene was 34.62%and the selectivity of cyclohexene oxide was 37.31%.In order to enhance the catalytic performance,the supported polyoxometalate hybrid catalysts were prepared by adding second metals.The second metals Cu,Fe,Bi,Ga,Co were supported by formaldehyde,hydrazine hydrate or hydrogen reduction method respectively.And on this basis,polyoxometalates BMo11,PW11,BW11 were prepared and the catalysts were prepared by replacing PMo11 or their binary mixing.The capability of the catalysts was compared with the effect of cyclohexene epoxidation.The result showed that,the second metal Bi supported by formaldehyde reduction method was better,and the optimum loading was 0.5%.And the catalyst prepared by mixing BMo11 and PMo11 with mass ratio of 1:1 was slightly better.The reaction conditions were:the catalyst was 1%Au-0.5%Bi/BMo11-PMo11/ZSM-5-M0.4,the amount of addition 0.02 g,2.0 g of cyclohexene,3 drops of TBHP,the reaction pressure 0.8 MPa,the reaction temperature 80 ? and the reaction time 18 h.The conversion of cyclohexene was 41.42%and the selectivity of cyclohexene oxide was 38.52%.This date had reached a better level of published literatures at present.In addition,the effects of reaction conditions on epoxidation of cyclohexene catalyzed by above catalysts were explored.The best conditions were:the catalyst 0.02 g,2.0 g of cyclohexene,3 drops of TBHP,the reaction pressure 0.5 MPa,the reaction temperature 80? and the reaction time 18 h.Under above conditions,the conversion of cyclohexene was 39.30%and the selectivity of cyclohexene oxide was 40.85%.And the catalyst showed a very good stability for four repeated experiments.Finally,the conceptual design of epoxidation of cyclohexene to cyclohexene oxide with output of 1500 t/a was proposed.The epoxidation process of cyclohexene was preliminarily simulated by Aspen Plus,and the preliminary layout of the plant was also designed.The result showed that the process route was feasible in technology,and would provide some reference for industrial design in the future.