Hydrogenation Of 2,5-dihydrofuran Catalyzed By Pd-M?Ce?Ca?Fe?Na?/?-Al₂O₃

At present,tetrahydrofuran(THF)was prepared in industry,in which contains dihydrofuran(DHF,2,3-dihydrofuran and 2,5-dihydrofuran),which is difficult to be removed.It will not only affect the polymerization process of THF,but also cause high chromaticity and poor quality of polymer,which is not conducive to the application in the downstream market.It is found that the conversion of DHF to THF by catalytic hydrogenation can not only reduce the content of DHF which is difficult to be removed by distillation,but also improve the purity of THF,increase the product yield and economic benefit.In recent years,researchers have carried out the research on the hydrogenation performance of C=C bond of Ni and Pd based catalysts.It is found that Pd based catalysts have the characteristics of high activity at low temperature and are the most suitable catalyst for dihydrofuran hydrogenation.However,the double bond isomerization and hydrogenolysis under Pd catalysis lead to incomplete hydrogenation or new by-products,which are still the key problems to be solved.In view of the above problems,this work takes 2,5-DHF hydrogenation as the probe reaction,studies the influence of promoters and reaction conditions on the hydrogenation performance of Pd based catalyst,obtains the relationship between the chemical properties of catalyst surface and the hydrogenation of C=C bond in DHF,so as to obtain high activity and high selectivity hydrogenation catalyst.The main research contents include:1.Pd-M(Ce?Ca?Fe?Na)/?-Al2O3 catalysts with Pd content of 0.3% and M content of 3.0% were prepared by step impregnation method.The effects of promoters on the hydrogenation of dihydrofuran over Pd/?-Al2O3 catalysts were studied by XRD,N2 physical adsorption,H2-TPR,H2-TPD and Py-IR.The results showed that the introduction of metal assistant in Pd/?-Al2O3 reduced the interaction between Pd and metal,reduced the surface exposed L acid sites,promoted the hydrogenation of 2,5-DHF to THF,and inhibited the production of 2,3-DHF.In particular,the introduction of Fe and the synergistic effect between Fe and Pd enhanced the adsorption of C=C double bond on thesurface of Pd,and greatly improved the conversion of 2,5-dihydrofuran.2.A series of Pd-x Fe/?-Al2O3 catalysts with Pd content of 3% and Fe content of3%~6% were prepared by equal volume impregnation.The effects of Fe on the hydrogenation of 2,5-dihydrofuran were studied by XRD,N2 physical adsorption,H2-TPR,FT-IR,TEM,NH3-TPD and Py-IR.The results show that the introduction of Fe into Pd/?-Al2O3 can effectively reduce the interaction between Pd and support,form more free Pd species,and facilitate the adsorption and activation of H2 species;meanwhile,the electron transfer between Fe and Pd is conducive to the adsorption and activation of2,5-dihydrofuran on the catalyst surface.When Fe content is 3%,the catalyst surface has the most weak acid center and the least medium strong acid center,the isomerization performance decreases,and the selectivity of tetrahydrofuran increases.3.The hydrogenation conditions of 2,5-DHF were studied by using Pd/?-Al2O3 and Pd-Fe/?-Al2O3 catalysts.The performance of the catalysts was compared and discussed.The optimal hydrogenation conditions of the two catalysts were studied.The experimental results show that the hydrogenation activity of Pd-3.0% Fe/?-Al2O3 is low and its stability is poor.When Pd-3.0% Fe/?-Al2O3 reacts at 50 ? and 1.5 MPa for 1 h,2,5-DHF can be basically converted into THF.When the temperature rises to 70 ?,a small amount of THF can be hydrogenated into butanol.