Study On The Preparation Of Cobalt Based Catalysts And Their Catalytic Performance In The Oxidation Of Cyclohexane

The aerobic oxidation of liquid cyclohexane is an important oxidation reaction of hydrocarbon in the industry and its products,cyclohexanol and cyclohexanone(KA oil),possess important industrial application.The activation of C-H bond which exists in saturated hydrocarbons and the low selectivity of KA oil due to the deep oxidation of cyclohexanol and cyclohexanone.The excellent catalytic performance of transition metal cobalt in cyclohexane oxidation can be seen from the industry and experiment research.Thus,the Co based catalysts,carbon nanotube supported Co catalyst,the derivative of metal-organic material ZIF-67 and Co3O4 with different morphology,were studied in this paper,respectively.carbon nanotube supported different transition metal Fe,Co and Ni was prepared with impregnation method and were used as catalysts in cyclohexane oxidation.The results show that the catalyst contains Co own better catalytic performance.And then carbon nanotubes supported cobalt inside and outside were prepared by the same impregnation method with different solvent,absolute ethyl alcohol and deionized water.The different catalytic performance of 5%Co/OCNT(in)and 5%Co/OCNT(out)was evaluated in the oxidation of cyclohexane with oxygen as oxidant in the presence of neither solvents or initiator.The results revealed that the 5%Co/OCNT(in)perform higher selectivity of KA oil.The content of Co,the reaction pressure,reaction time and reaction temperature were studied in this paper.It has been found that the 5%Co/OCNT(in)exhibits good performance that the conversion of cyclohexane is 8.40%and selectivity of KA oil is 79.27%at the condition of 150?,1.0MPa,2.0h.In this paper,ZIF-67 with rhombic dodecahedral structure.was prepared by room temperature agitation method and calcinated at different temperature in muffle,the derivative of ZIF-67 was obtained.The catalysts were characterized via XRD,FT-IR,TEM,SEM.The characterization results reveal the successfully synthesis of derivative of ZIF-67,and the main component is C03O4.The prepared catalysts have been tested in cyclohexane oxidation,it has been found that Co3O4-ZIF-67(400)exhibits slightly higher performance compared with ZIF-67,The conversion of cyclohexane is 10.72%and selectivity of KA oil is 78.23%.The catalyst Co3O4-ZIF-67(400)is characterized for excellent stability.Characterization and experimental result revaled that the crystal structure of ZIF-67 was destroyed after reaction,while the Co3O4-ZIF-67(400)can maintain its original crystal structure after reaction,achieved the purpose of recycling.The catalytic performance in cyclohexane oxidation of transition metal oxide Co3O4 prepared by different method were further studied in this paper.Coprecipitation method,solvothermal method and hydrothermal method have been used to prepare Co3O4,which possess different morphologies.The reaction results reveal the best catalytic performance of Co3O4 prepared by coprecipitation,The conversion of cyclohexane is 9.61%and selectivity of KA oil is 83.05%.This catalyst characterised by simple preparation method,low cost and recycle.This result may attribute to the contact area of reactant and catalyst.The effect of valence state of Co on cyclohexane oxidation was studied by doping Zn and Cu into Co3O4 in the preparation process.