Preparation And Catalytic Performance Of MOF In The Oxidtion Reaction Of Styrene

Catalytic oxidation of styrene has been widely concerned by researchers because the main products produced by the reaction,such as styrene oxide and benzaldehyde,can be used as essential organic intermediates in the synthesis of coatings,fragrances,medical chemicals and agricultural chemicals.Therefore,in the past decades,many researchers have devoted themselves to exploring and developing catalysts that can be applied to catalyze the oxidation of styrene.At present,there are two main types of catalysts used in this reaction,namely,homogeneous catalysts and heterogeneous catalysts.In general,homogeneous catalysts have high catalytic oxidation activity for styrene,but it is challenging to isolate them from the reaction system and recycle after the reaction was terminated.In contrast,the preparation of new reusable heterogeneous catalysts for the oxidation of styrene have more potential.And metal-organic framework materials(MOFs)are full of good stability,adjustable channel and the advantages of h?igh specific surface area,which can be functionalized modifications or doped to load a new metal and preparation of the bimetallic heterogeneous catalysts,and by the structure of the synergy between the two kinds of metal and further enhance the catalytic activity.In this paper,Cu_x-Co_y-MOF catalysts were prepared by one-step hydrothermal method and M@MIL-101(Cr)catalysts were prepared by impregnation method.Meanwhile,XRD,XPS,FT-IR and SEM were utilized to analyze the structural characteristics and surface morphology of the prepared metal-organic framework materials.In addition,the catalytic performance and stability of the prepared MOF materials for the oxidation of styrene were investigated,and the reaction conditions of the catalyst for the reaction were optimized.According to the characterization and test results,the following conclusions can be drawn:(1)The Cu_x-Co_y-MOF catalyst can still maintain the same octahedral shape and structure characteristics as Cu-MOF,which indicates that the doping of Co does not affect the morphology of Cu-MOF.However,it can be used to discern from the XPS results,the peak relative strength of Cu_x-Co_y-MOF catalyst at 933.2 e V was significantly decreased compare with the Cu-MOF material,which may be caused by the doping of Co metal.(2)When Cu_x-Co_y-MOF materials catalyze the oxidation of styrene,the catalytic effect is improved compared with Cu-MOF materials.The product selectivity of bimetallic MOF materials with different copper-cobalt ratios is different,that is,the increase of Co doping amount will increase the selectivity of the target product styrene oxide(Selectivity:51.07%→83.04%).(3)The M@MIL-101(Cr)catalyst prepared with transition metal supported in MIL-101(Cr)has similar structural characteristics to the support material,and its catalytic performance for the oxidation reaction of styrene has been significantly improved compared with MIL-101(Cr)(conversion rate:28.38%→97.45%),and it shows more excellent catalytic activity in the catalytic selective oxidation of styrene to the target product benzaldehyde.(4)Due to the synergistic effect between the bimetals in the structure of bimetal organic framework materials,the catalytic effect is better when it is applied to the catalytic oxidation of styrene.In addition,it was found that different catalysts have different catalytic effects under different reaction temperatures and reaction times,indicating that these factors have an impact on the activity of the catalysts.