Preparation Of Cobalt-based Metal Oxide Catalysts For Selective Oxidation Of Ethylbenzene With Molecular Oxygen

The selective oxidation of aryl alkanes has very important application value in laboratory and industrial organic synthesis,because its oxidation products have a wide range of applications in medicine,chemical and other fields,but also for the industrial production of polyester,fiber,paint and other necessary chemicals.Catalytic oxidation makes an important contribution to the production of various chemicals,pharmaceuticals and other useful compounds.The efficient oxidation of ethylbenzene(EB)through heterogeneous catalyst to synthesize acetophenone(AP)is both promising and challenging.On the one hand,traditional production processes often use stoichiometric oxidants with serious pollution and require high temperature or high pressure oxidation environment.On the other hand,homogeneous catalyst oxidation of EB can lead to difficult recovery and separation problems.In addition,the use of molecular oxygen as an oxidant is more economical and safer than peroxide.Based on the above understanding,a series of co-foundation composite catalysts were designed and synthesized in this paper.Under the condition of solvent-free,molecular oxygen was used as the oxidant to achieve the efficient selective oxidation of EB.In addition,the physical and chemical properties of the catalysts were studied systematically,and the effects of reaction parameters such as temperature and pressure on the catalytic activity were investigated.At the same time,combined with the reaction kinetics and free radical quenching experiments,the possible mechanism of action was preliminarily discussed.1.Preparation and characterization of(Co,Mn)(Co,Mn)2O4 catalyst and its catalytic oxidation of EBThe(Co,Mn)(Co,Mn)2O4 composite metal oxide catalyst with spinel structure was prepared by simple sol-gel method and characterized by XRD,SEM,HRTEM and XPS.The results show that the catalytic performance of the prepared catalyst for the selective oxidation of EB without solvent and oxygen is much better than that of Co3O4 and Mn2O3.The conversion rate of EB and the selectivity of AP are 77.9%and 89.5%,respectively.At the same time,the synergistic effect between(Co,Mn)(Co,Mn)2O4 makes(Co,Mn)2O4 have better reduction performance at low temperature,higher surface Mn3+/Mn4+ atomic ratio and abundant redox pairs.In addition,the catalytic performance of the catalyst under different reaction conditions was investigated,and kinetic analysis and free radical quenching experiments were carried out.2.Preparation and characterization of Co3O4/La2O2CO3 catalyst and its catalytic oxidation of EBComposite catalyst Co3O4/La2O2CO3 was prepared by solvothermal method.It was also used in the selective oxidation of EB to produce AP.Under the optimized reaction conditions,the conversion rate of EB was 79.5%,and the selectivity of AP was 90.0%,which was better than that of single metal catalyst.The cyclic experiment of the catalyst showed that the activity of the catalyst decreased slightly after five cycles.In addition,kinetics and free radical quenching experiments were used to investigate the oxidation mechanism of EB.The excellent catalytic activity of Co3O4/La2O2CO3 can be attributed to the abundant oxygen vacancy on the catalyst surface,the synergistic effect between bimetals and the high specific surface area.3.Preparation and characterization of CaxCoyOz catalyst and its catalytic oxidation of EBThe catalyst CaxCoyOz(Co3O4,CaCo2O4 and Ca9Co12O28 composite metal oxides)was prepared by solvothermal method and characterized by XRD,SEM,HRTEM and XPS.The catalyst can selectively oxidize EB with a conversion rate of 74.3%and a selectivity of 93.6%for AP.Combined with the characterization analysis,the multiple interfaces and abundant oxygen vacancies effectively regulate the electronic properties of the interface and promote the activation of molecular oxygen to form ·O2-species.The effects of reaction parameters on the catalytic performance were studied and cyclic experiments and kinetic analysis were carried out.The results showed that the morphology and structure of the catalyst did not change after repeated use,and the conversion of EB and the selectivity of AP decreased slightly,indicating that the catalyst has good stability and cycling performance.