Liquid Phase Oxidation Of Ethylbenzene To Acetophenone With Graphene-based Complexes

The selective oxidation of alkanes is useful in industrial chemistry for the production of desired pharmaceuticals and chemicals.And it is beneficial to the conversion from cheap hydrocarbons to high value-added oxygenates.The selective oxidation of ethylbenzene?EB?to acetophenone?AP?is one of the selective oxidation reactions.AP is an important organic chemical raw material.It can be used as an intermediate for the manufacture of resins,pharmaceuticals,flavoring agents and tear gas.It can also be used as a solvent for cellulose ethers and also as a fragrance.With the rapid development of chemical industry,the demand for AP is more and more.At present,there are mainly two methods to synthesize AP in industry,namely,the directly oxidation of EB and the Fridel-Crafts acylation of arenes.However,the conversion of AP is low,the by-products are numerous and the reaction condition under the pressure of 10 atm of air is harsh during the direct oxidation of EB;it will produce mang noxious and corrosive wastes during processes of the Fridel-Crafts acylation.So it is much interesting and urgent to design highly efficient and eco-friendly processes for the manufacture of AP from EB.On the one hand,green and efficient oxidants could be selected,such as O₂,H₂O₂ and tert-butyl hydroperoxide;On the other hand,new and highly efficient catalysts could be explored.And the reaction conditions and operation methods of the catalytic system can also be optimized to get the large-scale and high-quality preparation of AP.Graphene is a novel two-dimensional carbon material with a single layer of sp² carbon and it has superb structures and characteristics,such as unique electron mobility,mechanical strength,optical properties and high conductivity.What's more,it has the superior conjugated?�electron system that is much easier to form?�?stacking.Graphene aerogels,as graphene-based three-dimensional?3D?materials,retain the own advantages of graphene and have the merit of high porosity,a regulatable structure,highly compressibility and ultra-low density.Many studies have stated that the introduction of heteroatoms,for example B,N,P and S could effectively improve the function of graphene.More significantly,N-doped graphene has attracted considerable concern because of its chemical and electrical properties.The introduction of metal species can generate more active sites which are of great benefit to the reaction.Biomasses also have been utilized to prepare various functional carbon materials,because they are abundant,eco-friendly and have unique structural characteristics.This paper has prepared graphene-based complexes with graphite oxide as the substrate and the catalytic performance of these catalysts is investigated in the liquid phase oxidation of ethylbenzene to acetophenone.The main contents are as follows:?1?The cobalt/nitrogen-doped graphene aerogel is prepared by the hydrothermal and nitrogen calcination methods using graphite oxide as the substrate.Ammonia and cobaltous chloride are the nitrogen and cobalt source,respectively.XRD,Raman,FT-IR,SEM and EDS illustrated that both cobalt and nitrogen have been successfully incorporated into the graphene aerogel.The specific surface area of cobalt/nitrogen-doped graphene aerogel?Co-N-GA?is192.494 m²/g,and that of nitrogen-doped graphene aerogel?N-GA?is 541.150 m²/g.The catalytic activities of these catalysts in the selective oxidation of ethylbenzene to acetophenone have been tested with tert-butyl hydroperoxide as oxidant.Among them,the catalytic activity of Co-N-GA is the best one,the conversion of ethylbenzene is 93.58%,the selectivity of acetophenone is 92.05%,and there is almost no loss of catalytic activity after five cycles.The excellent activity of Co-N-GA is attributed to the doping of cobalt and nitrogen which could form the porous,multi-defect structure.?2?The series of graphene materials and N-doped graphene materials are successfully synthesized and improved by high temperature treatment with trace iron oxide.The catalytic performance of these catalysts has been investigated in the selective oxidation of ethylbenzene with tert-butyl hydroperoxide as oxidant.The impacts of temperature,mass of catalysts,reaction time and oxidants on the selective oxidation of ethylbenzene have been also investigated.The N-doped graphene materials exhibit greatly remarkable catalytic performance than others.The conversion of ethylbenzene is more than 90%and the selectivity of acetophenone is more than 95%at 353 K.Graphene can be used as catalyst owing to its unique structures and chemical properties.The characterization tests show that the doping of N atoms can create more defects and more active sites in the N-doped graphene materials which could greatly improve the catalytic performance.The N-doped graphene materials would be an alternative,efficient candidate for the oxidation of ethylbenzene.What's more,the introduction of heteroatoms would be helpful in the design of more active carbon-based catalyst.?3?Porous N-doped carbon-based composite aerogels?GA-CW-X,X=0.25,0.5,0.75,1?as an efficient potential catalyst have been successfully prepared through the processes of hydrothermal synthesis and calcination.Cattail wools and graphene aerogels are used as the carbon source and template,and urea is the nitrogen source.The composite aerogels exhibit excellent catalytic activities in the selective oxidation of ethylbenzene to acetophenone with tert-butyl hydroperoxide as oxidant and the selectivity of acetophenone can be more than 92%.The porous structure,the introduction of nitrogen and the interaction between cattail wools and graphene aerogels are of benefit to the catalytic performance.The novel method to convert cattail wools into high-value-added carbon materials provides a new design of the high-performance catalysts for the selective oxidation of ethylbenzene.