Preparation,characterization And Catalytic Performance Of ZrO₂-Al₂O₃ Mixed Oxides

In the morden oil chemical industry,developing new type catalyst with carrier which has high strength and a certain surface acidity has always been a research hot spot.ZrO₂-Al₂O₃ mixed oxide is an important catalyst carrier material,has been applied in many fields,which has many characteristics,such as large surface areas,abundant surface acditity,high thermal stability and so on.In this paper,the molding process of ZrO₂-Al₂O₃ mixed oxide has been studied by many catalyst characterization methods.In this dissertation,a series of ZrO₂-Al₂O₃ mixed oxide were perpared by extrusion method.I investigated many factors how to effect the physical and chemical performance of ZrO₂-Al₂O₃ mixed oxides,such as the content of ZrO₂,calcination temperature,the type of agglomerant,the concentration of agglomerant.TEM,BET,FTIR measurements were used to characterize the ZrO₂-Al₂O₃ mixed oxides.The Ni/ZrO₂-Al₂O₃ catalysts were prepared by impregnation methord on the ZrO₂-Al₂O₃ mixed oxides.The synthesis of methyl isobutyl carbinol（MIBC）from diacetone alcohol（DAA）over Ni/ZrO₂-Al₂O₃ catalysts were carried out to investigate the content of ZrO₂,reaction temperature,mass space velocity（WHSV）were how to effect the catalysts,activities.Experimental result has been associted with the structure and physical properties of the mixed oxide to provide certain technicl support for a new catalyst carrier containing zirconium.The result indicated that:（1）In the process of preparation of ZrO₂-Al₂O₃ composite carrier with extrusion method,factors affecting the strength of carrier are mainly for the ratio of raw material,calcination temperature,kneading time.With the increase of the content of Al₂O₃ in ZrO₂-Al₂O₃,calcination temperature and kneading time,the strength of the carrier showed a trend of increase.When the mass ratio of ZrO₂ and Al₂O₃ was 1:5,calcination temperature was 600 ℃,the strength of carrier prepared could reach 163.2 N/cm.（2）Factors influencing the surface areas of ZrO₂-Al₂O₃ are mainly the ratio of raw material,calcination temperature,kneading time.With the increase of the content of ZrO₂ in the ZrO₂-Al₂O₃,calcination temperature and kneading time,the surface area of the carrier showed a trend of decline.When the mass ratio of ZrO₂ and Al₂O₃ was 1:5,citric acid was the bonding agent,calcination temperature was 500℃,the surface area of ZrO₂-Al₂O₃ could reach 221 m2/g.The surface area of the carrier will be significantly reduced when the calcination temperature is too high,while the strength of the carrier will be increased to a certain extent.（3）There were only L acid sites on the surface of the ZrO₂-Al₂O₃ composite surpports.compared with the Al₂O₃ support,the ZrO₂-Al₂O₃ composite oxides had new weak acid sites,and the content of Zr O₂ could adjust the distribution of the surface acid strength.When zirconia content was 10%,the amount of weak acid and medium strong acid reached maximum,and the ratio of weak acid,s and medium strong acid,s concentration reached maximum.（4）In the process of preparation of methyl isobutyl carbinol（MIBC）from diacetone alcohol（DAA）,when the content of ZrO₂ was 10%,reaction temperature was 180 ℃,mass space velocity was 2.62 h-1,the yield of MIBC could reach 21.8%.A moderate amount of of ZrO₂ in ZrO₂-Al₂O₃ composite surpports added new weak acid site,which promoted the dehydration and hydrogenation performance of catalysts.