Synthesis And Phenol Oxidation Of Metal-modified HMS

With the development of industry,people pay more attention to t he green synthesis of products while paying attention to high yield.The mesoporous silica material has gradually become a new research focus due to its high surface area,uniform and controllable size pore structure.However,the mesoporous molecular sieves lack of the active components needed for the reaction,so they need to be modified to have better catalytic performance.In this paper,the transition metal is introduced into the molecular sieve channel through in-situ synthesis.After aerobic calcining,the metal oxide is fixed on the surface of the inner channel to form an active center.The structure of the modified molecular sieve channel is basically unchanged.Based on dodecylamine（DDA）as the template agent,ethyl ortho silicate（TEOS）as silica source,using sol-gel method the HMS meso porous molecular sieve,and Co Cl₂·6H₂O,cerium nitrate,nickel nitrate,ammonium molybdate and partial ammonium vanadate as the active component in situ synthesized single metal M-HMS（M=Co,Ni,Ce,Mo,V）,through the X-ray diffraction spectrum（XRD）,scanning el ectron microscopy（SEM）,Fourier infrared spectrum（FT-IR）,N₂ad sorption-desorption,thermal analysis（TG-DTA）the V-HMS were char acterized and analyzed.The results showed that the pore configuration of mesoporous molecular sieve was not changed by the introduction of metal,and the pore size and internal surface area decreased slightl y with the increase of metal,indicating that metal oxides successfully embedded into the molecular sieve instead of silicon atoms in the por e.The catalytic oxidation of some common phenols was studied with the prepared molecular sieve as catalyst.In this paper,the prepared V-HMS was used as catalysts to expl-ore the reaction conditions for preparation of 1,4-naphthoquinone by t-he catalytic oxidation of 1-naphthol.In the experiment,30%hydrogen peroxide was used as the oxidants,acetonitrile as solvent,and reactio ntemperature was 60℃for 2 h.The conversion rate of 1-naphthol was 98.73%,the selectivity of 1,4-naphthoquinone was 96.22%,and th eyield was 95.06%.Under the same conditions,the oxidation reaction of 1-naphthol was carried out on silica materials with different transiti on metal loads,and the catalytic effect was compared with V-HMS.At the same time,V-HMS was used as the catalyst to investigate the catalytic oxidation of 2-naphthol,phenol,2,5-dimethyl phenol to prepare 2-hydroxy-1,4-naphthoquinone,benzoquinone,2,5-dimethyl benz oquinone,and the optimal reaction conditions were investigated,Result s:the yield and selectivity of 2-naphthol were 98.21%,96.22%,98.22%,50.28%,59.15%,29.74%,89.13%,76.03%,85.39%,respectively.In or-der to compare the catalytic activity of catalyst,some simpl e electroc-hemical oxidation of phenol were carried,the experimental condition was:with the mass fraction of 5%sulfuric acid solution as electrolyte,with acetonitrile and dichloromethane as solvent,the temp erature was20-30℃,electrolytic time constant current was adjusted to0.3 A,theexperiment results showed that under the condition of mod erate,selectivity of electrochemical oxidation of product was higher th an chemicaloxidation.