Study On Selective Catalytic Hydrogenation Of Naphthalene To Tetrahydronaphthalene

With the continuous development of coal chemical industry,the use of high-value fractions of coal and coal char has been extensively studied.Among them,the separation and hydrogenation of coal tar can increase its added value.Not only can get high value single compounds from coal tar,but also can be hydrogenated these to make them more valuable,to achieve the purpose of high efficiency and quality utilization of coal.In this paper,naphthalene as the research object,the use of high temperature and high pressure reactor for its selective catalytic hydrogenation to tetrahydronaphthalene.On the one hand,it can increase the added value of naphthalene,on the other hand,the naphthalene as a model compound can be used to explore the laws and catalysts for the hydrogenation of coal tar,and provide certain theoretical and technical support for the use of coal tars for their quality and high value.NiMo/Al₂O₃ catalysts were prepared by the equal volume impregnation,using nickel and molybdenum as active metals and activated alumina as carriers.The optimum loading of catalyst was 24%,the loading ratio of nickel to molybdenum was 1:5,and the optimum calcination temperature was 500℃ under the optimal conditions of metal loading,loading ratio,temperature,pressure and time.The process conditions were as follows:200℃,6 MPa,8 h.The experimental results were as follows:the conversion of naphthalene was 95.62%,and the selectivity of tetralin was 99.75%.Under these conditions,the naphthalene hydrogenation of this catalyst produces good performance for tetrahydronaphthalene.Preparation of naphthalene hydrogenation catalysts by self-made activated alumina carrier by gel-sol and precipitation,compared with catalysts prepared by industrial support,and the better preparation method of active alumina carrier was explored.The catalysts were characterized by XRD,NH₃-TPD,BET,TPR and SEM.The effects of different preparation methods on the surface acidity,pore structure and activity of active metals were investigated.The results showed that the activated alumina support prepared by gel-sol method prepared the best catalyst,naphthalene conversion was 99.56%,tetralin selectivity was 99.43%.The characterization results of the catalyst also showed that the catalyst prepared by the gel-sol method has a large acidity,a relatively large area,and the active metal is easily reducible.Study on different morphology and phosphorus modification of different single and double metals of activated alumina supported by Ni-Mo Explore the influence of different catalyst morphology and phosphorus modification on catalytic effect The results of phosphorus modification showed that phosphorus modification improves the hydrogenation activity of these catalysts to varying degrees.The results of oxidation,reduction and sulfided NiMo/Al₂O₃catalysts show that the conversion of naphthalene and the selectivity of tetralin are higher in the oxidation state catalyst,which is most suitable for the selective catalytic hydrogenation of naphthalene to prepare tetrahydronaphthalene.But the sulfide catalyst has a very high naphthalene hydrogenation activity,can make naphthalene completely converted to decalin.