Study On Selective Oxidation Of Aromatic Olefins To Aromatic Aldehydes

The aldehyde group of aromatic aldehyde is a very active group,and can occur a variety of organic reactions easily.Therefore,aromatic aldehydes are widely applied in chemistry and chemical industries.Three kinds of metal(Co,Ni,and Cu)molybdate catalysts were prepared by EDTA assisted hydrothermal method and characterized by XRD for structure.Then the catalytic effects of three catalysts in the selective oxidation reaction of aromatic olefins were also investigated.With CoMoO4 as catalyst and acetonitrile as solvent,the conversion of styrene could reach 91%and the yield of benzaldehyde was 74%under hydrogen peroxide at 70?for 12 h.Influenced by the space effect and the electron density on the double bond,the catalyst has different reactivity to other olefin.In addition,it also has prominent catalytic effect on the alcohols,and the selectivity of the products was close to 100%.Bimetallic combination effect existed in catalytic system,and the combination of Co and Mo was beneficial to the reaction.The new material(rGO)was the carrier to prepare the corresponding supported catalysts by loading the compound oxides of Co or Ni and V.Their structure and morphology were characterized by FT-IR,Raman,TEM,and XRD.With CoV/rGO as catalyst,styrene could be converted to benzaldehyde with a high conversion rate of 95%and a high yield of 85%.In cycles the catalyst still maintained high catalytic activity,and the yield of benzaldehyde could reach more than 80%.When expanding the substrates,we found that the catalyst exhibited a high catalytic activity in a series of styrene derivatives,having good substrate universality.Reaction mechanisms of CoMoO4 and CoV/rG for catalytic oxidation of aromatic olefins were studied.It was found that the catalysts were combined with hydrogen peroxide to produce peroxide intermediates,which were then reacted with double bond of styrene to form styrene oxide;subsequently,the styrene oxide continued to combine with the peroxide intermediate to generate the transition state with the diepoxy structure,which was finally decomposed into benzaldehyde.The difference of mechanisms was the formation of peroxide intermediates,the cobalt-oxygen ring bond of the CoMoO4 catalyst was opened under hydrogen peroxide;and the CoV/rGO catalyst was the oxidation of the vanadium-oxygen double bond.