Studies In The Preparation Of Novel Hybrid Nanocarbon Catalyst And Catalytic Direct Dehydrogenation Of Ethylbenzene To Styrene

With the development of the economy,the petrochemical products and derivatives have attracted a lot of attention from all over the world and they have been applied in many fields widely.Styrene which can be obtained by the dehydrogenation of ethylbenzene is an organics which has unsaturated carbon-carbon double bond and it can be applied in the synthesis of macromolecular organic polymers such as the synthetic rubber.The dehydrogenation of ethylbenzene to styrene can be divided into the oxidization dehydrogenation of ethylbenzene to styrene and the direct dehydrogenation of ethylbenzene to styrene.And the main process condition of the dehydrogenation of ethylbenzene to styrene in chemical industrial is using Fe-K based catalyst and the water vapor to prevent the coke.This way has many disadvantages such as the high energy consumption,low selectivity,easier deactivation and the pollution of the environment caused by the loss of metal.Compared with the tranditional industrial catalyst,the sustainable carbon-based catalyst which can be applied in the dehydrogenation of ethylbenzene to styrene under the anaerobic conditions shows good stability without the using of metal.In this paper,aiming at the existing problems of direct dehydrogenation of ethylbenzene to styrene on nanocarbon catalysts,the research on preparation of new nano-carbon catalysts and the exploration of the catalytic performance on direct dehydrogenation of ethylbenzene to styrene has important academic value and practical significance.In this paper,two novel nanodiamond/carbon nanotube hybrid catalysts were prepared by wet two-step method and surfactant-assisted dispersion method,and the catalytic properties and structure-activity relationship of styrene prepared by direct dehydrogenation of ethylbenzene from the hybrid were studied.The detailed contents are listed as follows:（1）The nanodiamond（ND）and carbon nanotubes（CNT）were used to prepare nanodiamond/carbon nanotube hybrid carbon materials（N,O-ND/CNT-d）by two-step method.The unagglomerated ND is loaded onto the CNT to increase the number of active sites exposed.Furthermore,nitric acid treatment was carried out on the hybrid catalyst to eliminate the CN compounds to exposure of more defects and increase the number of C=O on the surface by surface oxidation.The prepared N,O-ND/CNT-d hybrid nanocarbon materials shows excellent catalytic performance of the direct dehydrogenation of ethylbenzene to styrene that the styrene production rate can reach 5.2 mmol g^-1 h^-1 and the yield can reach 16.8%with a high selectivity of 98.7%.The catalysts were characterized by means of TEM,XRD,XPS,BET and Raman to explore the structural-activity relationship of the catalysts.We can find that the N,O-ND/CNT-d hybrid nanocarbon catalyst for ethylbenzene dehydrogenation to styrene can show excellent catalytic performance due to its unique hybrid structure,heteroatom doping and the addition of defects and C=O,and reactive nitrogen doped alkali and nucleophilicity of ethyl benzene pyrolysis side effects such as inhibition,（2）From the above work,we can be inspired that the preparation of hybrid catalyst can solve the problem of the agglomeration of nanocarbon materials.In this work,we choose sodium lauryl sulfate（SDS）to solve the deaggregation of nanodiamond and nano carbontubes and prepare a kind of hybrid carbon materials with S-doping（ND/CNT-SDS）.The ND/CNT-SDS can be applied in the direct dehydrogenation of ethylbenzene to styrene and improved the catalytic performance that the styrene rate can reach 7.7 mmol g^-1 h^-1 with good selectivity.By the characterization of TEM,HRTEM,XPS,XRD,BET,FT-IR and chemical titration and the association of the catalytic performance,we can find that using the surfactant can promote the dispersion of nanocarbon materials,add the active sites and surface area and promote the catalytic performance.This work,apart from the preparation of the hybrid catalyst with high catalytic performance of dehydrogenation of ethylbenzene to styrene,it also can provide a reference for the preparation of nanometer carbon hybridization catalysts which need to be dispersed for other reactions.