Study On Catalytic Oxidation Of Cyclohexane With New Covalent Organic Framework Materials

The selective oxidation of cyclohexane to cyclohexanone and cyclohexanol is one of the important reactions in petrochemical industry.Actual industrial process of cyclohexane oxidation mostly uses metal cobalt salt as catalyst and oxygen as oxidant under high temperature and high pressure.The reaction process has the disadvantages of high reaction temperature,low substrate conversion rate and target product yield,and high energy consumption for product separation.Many researchers have prepared various monomeric metal porphyrins,metal oxides or metal nanoparticles and other high-efficiency catalysts for cyclohexane oxidation.These catalysts can show good catalytic effects at high temperatures,the KA oil selectivity and cyclohexane conversion are improved,but the effect of improving the selectivity of alcohol or ketone in KA oil is not obvious,and the reusability of these catalysts is still not good enough.COFBTC builds a metalloid phthalocyanine active center,provides abundant active sites for cyclohexane oxidation,and provides sites for interaction with hydroxide and polar solvent molecules to ensure the solubility of COFBTC in polar solvents.The highly conjugated structure of COBTC provides a carrier transport channel,which can ensure high catalytic activity,and the ring structure ensures the thermal stability and chemical stability of COFBTC,COFBTC has been highly studied as a catalyst for cyclohexane oxidation,Loading COFBTC on a porous support can also improve the dispersibility and stability of catalytic activity.Based on this,we used COFBTC and graphene as raw materials and prepared a new type of COFBTc/graphene catalyst by impregnation,and carried out FT-IR and Raman characterization analysis.COFBTC,COFBTC solution and COFBTC/graphene are used for cyclohexane oxidation,and the effects of various reaction factors such as pressure and temperature on the catalytic effect are analyzed.The specific research content and innovations are as follows:(1)The fully conjugated quasi-phthalocyanine active structure in COFBTC exhibited high activity and selectivity for cyclohexane oxidation.When the reaction temperature is 120?,the reaction pressure is 1.0 MPa,the time is 2 h,the conversion rate of cyclohexane reaches 9.6%,the selectivity of KA oil reaches 90.4%,and the catalyst has reusability.COFBTC can show good catalytic effect of cyclohexane oxidation at lower temperature,and the chemical stability of heterogeneous COFBTC ensures the reusability of the catalyst.COFBTC has industrial application and research value in cyclohexane oxidation.(2)The COFBTC catalyst dissolved in acetonitrile has the ability to oxidize cyclohexane to cyclohexanone with high selectivity.Reaction temperature 120?,reaction pressure 1.5 MPa,and reaction time 4 h,the conversion rate of cyclohexane was 12.3%,the selectivity and yield of KA oil reached 93.4%and the selectivity of cyclohexanone was 87.3%.The advantage of COFBTC's acetonitrile solution as a catalyst is to greatly improve the selectivity of ketones.This work provides new ideas for the homogeneous catalytic oxidation of cyclohexane.(3)The porous material graphene as a carrier can improve the dispersion and stability of the COFBTC active center.The catalytic activity of the COFBTC/graphene composite catalyst is higher than that of COFBTC.Under the experimental conditions of 145?,1.0 MPa,and 4 hours of reaction,the COFBTC/graphene TON reaches 1.2�105,which is about 2 orders of magnitude higher than that of unloaded COFBTC.This work can prove that the support of porous carriers,such as graphene,can improve the catalytic activity to a certain extent.This work will provide help for the preparation of new covalent organic polymer catalysts in the future.