Preparation And Catalytic Performance Of Modified Sepiolite Supported Nickel Catalysts

Aniline is a very important chemical raw material.In the industry,nitrobenzene catalytic hydrogenation is generally used to prepare aniline.Generally,the catalyst used in the catalytic hydrogenation reaction is optimized with a noble metal catalyst.Due to the high cost of the noble metal catalyst,the non-noble metal catalyst has become a hot research topic,and the nickel-based catalyst is widely used in the field of hydrogenation reaction.Simple,low in price,easy to separate and recover,and good catalytic activity,it has broad application prospects in the field of catalysis.As a new type of material,sepiolite has better performance than traditional Ni carriers such as SiO₂、MgO or Al₂O₃ in terms of activity and stability,mainly due to its intricate pore structure.There are few reports on the preparation of supported catalysts using sepiolite as a carrier.In this paper,sepiolite was used as a hydrogenation catalyst carrier to prepare 20wt.%nickel-based catalyst and 10%wt.%nickel-based catalyst to catalyze the hydrogenation of nitrobenzene and study its catalytic performance.In this paper,20wt.%Ni/Msep catalyst was prepared by precipitation method and used for the gas phase hydrogenation of nitrobenzene to prepare aniline.First,the effects of different precipitants on the performance of the catalyst were investigated.Comparing the three precipitants of sodium carbonate,urea and oxalic acid,we found that the performance of the prepared catalyst is optimal when using sodium carbonate as a precipitant.In addition,we investigated the effects of different pH on the preparation of the catalyst and the effect of different loadings on the performance of the catalyst.It was found that the catalyst prepared at pH 9.0 had the best performance and the best catalytic effect at 20wt.%loading.Finally,the reaction conditions were optimized by using20wt.%Ni/Msep catalyst.The optimum reaction conditions were obtained when the reaction temperature was 300℃,the ratio of hydrogen to oil was 5:1,and the residence time was 5.71 s.The conversion of nitrobenzene was 98.75%,the selectivity of aniline is98.63%.At the same time,the stability was investigated.After continuous reaction for 52h,the conversion of nitrobenzene decreased to about 67%,and the selectivity of aniline was relatively stable at about 94%.After the catalyst was regenerated,it was found to have good catalytic effect.The catalyst structure was analyzed by TG,XRD,SEM,BET,H₂-TPR,FT-IR,ICP.The catalyst prepared in the above was reused for liquid phase hydrogenation.It was found that the catalyst still had high catalytic activity,but the 20wt.%Ni loading was very high,so we reduced the Ni loading to 10wt.%.At this time,the catalytic activity is very low.The conversion of nitrobenzene was only 59.41%,and the selectivity of aniline was84.43%.Therefore,in this chapter,the Msep catalyst is modified by TiO₂,and due to the interaction between Ti-Ni,the conversion of nitrobenzene reaches 100%and the selectivity of aniline reaches 98%at 10wt.%Ni loading,the process was optimized under these conditions,and The catalyst structure was analyzed by TG,XRD,SEM,BET,H₂-TPR,FT-IR,ICP,XPS.The Ti species can not only improve the hydrogenation capacity of Ni,but also promote the reduction of Ni and the better adsorption and dissociation ability of hydrogen.