The Preparation Of Metal Oxide/Graphene Composite And Its Application In The Selective Oxidation Of Benzyl Alcohol

Graphene is a honeycomb planar film formed by sp2 hybridization of carbon atoms.It is a quasi-two-dimensional material with only one atomic layer thickness with the C—C bond connected to the honeycomb crystal.Since its first successfully exfoliated from the graphite by the physicists Andre Geim and Konstantin Novoselov in Manchester University,with the micro-mechanical stripping method in 2004,it has propelled the development in physics,materials science,electronic information,computer,aerospace and other fields,and has become a hot topic in recent years because of its excellent Strength,toughness,conductive thermal conductivity,optical properties,etc.The graphene composite material is an important research area in the domain of graphene application.It has excellent performance in energy storage,liquid crystal devices,electronic devices,biomaterials,sensing materials and catalyst carriers.At present,the research of graphene composites mainly focuses on graphene polymer composites and graphene inorganic nanocomposites.Due to its large theoretical surface area,the availability of carbon skeleton functionalization,superb electron transport capacity,it is ideal for catalyst carriers.Meanwhile,the combination of graphene with inorganic nonmetallic,small organic molecules,polymers has also confirmed and testified the great potential as an ideal nano-support carrier.It is apparent that metal nanoparticles and graphene share some common places-they both have large specific surface area,good electron transfer property.Also because of these excellent properties,metal nanoparticles have been widely used in the surface Raman enhancement,sensing technology,medical diagnosis,catalysis and other fields.It can be possible that the composite products of graphene and metal nanoparticles will demonstrate more attractive physical and chemical properties with the significant increase in specific surface area and conductivity,the application in the fields of energy,biology,chemical and other fields will be much more impressive and prepossessing.Therefore,the preparation of metal oxide/graphene composite catalyst will be of great significance to both fundamental research and industrial applications.In this paper,Al/Fe oxide graphene composites were prepared and applied in the catalytic oxidation of benzyl alcohol.Firstly,the precursor graphene oxide was prepared by modified Hummers’ method which was subsequently utilized int the preparation of Al/FeOx RNGO catalyst by solvothermal method.At the same time,the composition and internal and external structure of the catalyst were determined by means of FTIR,XRD,XPS,TEM and SEM.The in situ generated Al and Fe oxide nanoparticles are evenly distributed over the N-hybridized graphene surface,but the overall arrangement is still cluttered and chaotic.The agglomeration of nanoscale particles,however,is effectively prevented,and the two-dimensional structure of graphene was also maintained in good shape.The selective oxidation reaction of benzyl alcohol was used as the probe reaction.The parameters of the reaction were studied by single factor parallel experiment to optimize the reaction condition,in order to obtain the best conversion and selectivity,which was 85.2%and 98.4%,respectively.At the same time,we investigated the time and temperature of the heat treatment of the catalyst,and found that the heat treatment time and temperature have a great effect to the performance of the catalyst.Choosing the appropriate heat treatment time and temperature will greatly improve the conversion rate of the reaction.We further proposssed the reaction mechanism of Al/FeOx RNGO catalyzd selective oxidation of benzyl alcohol,according to the experimental observation and the existing theory.In addition,the catalytic effect of a series of different nano-metal oxides and carriers were also examed,but it turned out that the catalytic performance of Al/Fe composite metal oxide on graphene was superior over others,such as zeolite,heteropoly acids.Finally,we tested the recycling performance of the catalyst.The conversion and selectivity of the catalyst did not suffer a sever lost,and the active components were still well distributed on the surface of the graphene carrier after 10 trials,certifying that the catalyst is excellent chemical stable and industrial application prospects are promising.In addition,Al/Fe/SnOx RNGO were prepared and the effect of metal tin on the particle size of the synthesized nanoparticle composites was studied.The results were analyzed by FTIR,XRD,TEM,SEM and other methods.The metal Sn can effectively reduce the particle size and reduce the possibility of agglomeration of nanoparticles,and can further enhance the catalytic efficiency.Compared with the two-component Al/FeOx RNGO,the three-component Al/Fe/SnOx RNGO has a better catalytic effect on the selective oxidation of benzyl alcohol.Under the optimum conditions,the conversion and selectivity can reach 90.2%and 99.3%.The prepared catalyst also showed good stability:after the lifetime test,the selectivity and conversion rate remained essentially unchanged.