Preparation Of Cobalt Modified Mesoporous Molecular Sieve And Its Study On Epoxidation Of Styrene

Styrene oxide（SO）is an important organic intermediate.It is widely used in pharmaceutical synthesis,fine chemicals and other fields.It can also be used as an epoxy resin diluent and ultraviolet absorber.At present,the main production method of styrene oxide is the halohydrin method,which has large environmental problems,high production costs and backward technology,and it is urgent to develop a new green and environmentally friendly production process.In this paper,based on mesoporous molecular sieve HMS and transition metal Co as the active component,cobalt modified catalysts were prepared by impregnation,co-impregnation and in-situ synthesis.The catalysts were analyzed and studied using various characterization methods.The prepared catalyst was used in the synthesis of styrene oxide,oxygen was used as the oxidant,and the process conditions for the synthesis of styrene oxide by epoxidation of styrene were optimized.Cobalt-supported catalyst Co/HMS was prepared by impregnation method and co-impregnation method.XRD,UV-Vis and other characterization methods were used to analyze the sample structure,cobalt dispersion and existence form.The results show that the cobalt catalyst prepared by the impregnation method exists in the form of Co₃O₄,the cobalt catalyst active component prepared by the co-impregnation method appears isolated[Single-site Co（Ⅱ）],and the cobalt oxide dispersion is better.According to the evaluation of the reaction of styrene epoxidation to synthesize styrene oxide,the catalyst prepared by the co-impregnation method has better activity.The preparation conditions of Co/HMS prepared by co-impregnation method were further investigated and optimized.The best preparation conditions were:selection of Ethylene glycol,addition amount of ethylene glycol（Co:EG=1:1）,and baking temperature of 550℃.Under this catalyst condition,the reaction process conditions were optimized.The best reaction condition:O₂（30ml/min）,reaction temperature is 110℃,DMF amount is 25ml,reaction time is 4h.At this time,styrene conversion rate and SO selectivity were 98.01%and 48.49%,respectively.M-HMS molecular sieves modified with different metal ions were prepared by in situ synthesis,and the effect of different metal doping on the molecular sieve structure was explored.Among them,Co-HMS modified with cobalt had better activity.The analysis using mesoporous molecular sieve framework and did not destroy the framework structure.When the cobalt doping amount is small,Co exists in the form of isolated[Single-site Co（Ⅱ）].Through the evaluation of styrene epoxidation,the types of solvents,oxidants and process conditions were explored.When DMF is the solvent and TBHP is the initiator,the reaction is carried out at 100℃for 4h at O₂（20ml/min）.The highest styrene conversion rate and SO selectivity were 91.24%and 43.41%,respectively.