Preparation Of Boron Doped Graphene And Iron Aluminum Oxide/graphene Nanocomposites And Its Oxidative Dehydrogenation Of Benzyl Alcohols

Graphene,due to its huge theoretical specific surface area,oxygen-containing groups,special structure and so on,has a good application prospect in catalytic oxidative dehydrogenation of alcohols and alkanes as a new nano-carbon catalyst in recent years,which has attracted scholars'attention.Benzaldehyde is one of the simplest aromatic aldehydes and has a wide demand in fine chemical industry.To date,the oxidative dehydrogenation of benzyl alcohol to benzaldehyde is one of the simplest and environmental-friendly methods.In this paper,graphene was directed used as the nanocarbon catalysts,and the catalytic performance of graphene is mainly studied from two aspects.First,graphene was doped and modified,and boron atoms were used as doping elements because their atomic size was close to that of carbon atoms.Boron doped graphene with different boron contents was prepared by annealing at high temperature in an inert atmosphere.The effects of boron doping and boron doping on the structural properties and catalytic properties of graphene were investigated.Boron-doped graphene is directly the most nano-carbon catalyst for catalytic oxidative dehydrogenation of benzyl alcohol,and has the advantages of high selectivity?the benzaldehyde selectivity is above 97%?,but its catalytic activity is poor,and benzyl alcohol conversion rate is about 20%.Secondly,graphene is compounded with non-noble metal Fe/Al oxide as a catalyst for oxidative dehydrogenation of benzyl alcohol.Solvothermal method is considered to be the most commonly used method to synthesize metal-based graphene composites,but this method usually requires a long reaction time,usually 5-35 h.In order to obtain nanocrystalline phase structure,it is necessary to add some structure-oriented agents or surfactants in the reaction system.In addition to solvothermal method,thermal decomposition and electrochemical methods can also be used to prepare metal-based graphene composites,but their applications are limited by some restrictive factors,such as complex operation,long reaction time,difficulty in obtaining precursors and high cost.In this paper,the iron-aluminium oxide-graphene composite was prepared by one-step method using supercritical?subcritical?fluid,which is different from the traditional method.Supercritical method has many advantages,such as adjustable physical and chemical properties,simple reaction system,short time-consuming,easy operation and large-scale application.It is considered to be one of the most promising methods for the synthesis of nanomaterials.In the experiment,ethanol was used as solvent and reductant to provide pressure for the sealed reaction system at a certain temperature and to reduce graphene oxide.In this part,the effects of graphene,graphene addition,preparation temperature,preparation pressure,catalyst promoter Al and Al/Fe ratio on the structure and catalytic performance of the iron oxide/graphene composite were investigated.The results show that the introduction of B into graphene can significantly improve the conversion of benzyl alcohol and the selectivity of benzaldehyde which higher than other metal-based catalysts.The superior catalytic performance of BGs is attributed to boron doping species?BC₃?enhanced the O₂ chemisorption on catalysts and further promoted forming the active sites?C=O?.It can be observed with XPS analysis,the BC₃ could stimulate the increase in the amount of C=O obviously,and thus promoted the C-H bond activation ability of BG.Graphene is compounded with non-noble metal iron-aluminium oxides.Graphene provides a carrier for iron-aluminium oxides and contributes a certain amount of C=O active sites.FeOx can improve the activation ability of molecular oxygen and benzyl alcohol.These factors make the iron-aluminium oxide-graphene complex catalyst have good catalytic activity and selectivity.The conversion rate of benzyl alcohol reaches 75%,and the selectivity of benzaldehyde reaches 90%.