Synthesis Of Ce-based Composite Oxide Supported Noble Metal Pt Catalysts And Their Performance Investigation Toward Selective Hydrogenation Reaction

Because of unique redox properties,high oxygen storage capacity（OSC）and ability to transform quickly between Ce³⁺and Ce⁴⁺of CeO₂,it is widely used in heterogeneous catalysis reaction.Previous literatures reported that after CeO₂was combined with other metals,which obviously improves the redox performance and recycle stability.Due to important catalytic applications of CeO₂catalysts,two kinds of Ce-La and Ce-Al composite oxide supported metal Pt nanoparticles were successfully prepared.The physicochemical properties of the prepared catalytic materials were characterized by different characterization techniques such as XRD、TEM、FTIR、Raman、N₂-desorption and XPS、H₂-TPR.Finally,using selective hydrogenation reaction of cinnamaldehyde and 2-pentenal as model reaction,Ce-La and Ce-Al composite oxide supported catalysts were investigated,respectively.Firstly,Ce-La composite oxides（molar ratio of Ce and La=1:10,1:1and 10:1）were synthesized by coprecipitation and calcination,and then using impregnation Pt nanoparticles were deposited.Ce-La composite oxide supported Pt catalysts successfully synthesized.Characteristic results displayed that Ce1La10,Ce1La1 and Ce10La1 composite oxides possesses spherical particle morphology and particle size were about30-40 nm.Pt nanoparticles were highly dispersed in all composite oxide supports and their particle size was 4-5 nm.With increase in La contents,the specific surface area of composite oxides decreased from 112 to 54 m²g^-1.Pt/La₂O₂CO₃and Pt/CeO₂catalysts were also prepared to test the selective hydrogenation properties of cinnaldehyde with all catalyst.Pt/Ce1La1 catalyst exhibited the highest catalytic activity.Combined with XPS and H₂-TPR results,this enhanced activity of Pt/Ce1La1catalyst resulted from strong metal-support interactions（SMSI）.Second,we also successfully prepared Ce-Al composite oxides（molar ratios of Ce and Al are 1:10,1:1 and 10:1）supported Pt nanoparticle catalysts using coprecipitation and impregnation method.Characteristic results displayed that Ce1Al10,Ce1Al1 and Ce10Al1composite oxides possesses spherical particle morphology and particle size were about 8-10 nm.Pt nanoparticles were highly dispersed in all composite oxide supports and their particle size was 4-5 nm.With increase in Al contents,the specific surface area of composite oxides increased from 92 to 157 m²g^-1.For comparison,Pt/Al₂O₃and Pt/CeO₂catalysts were also prepared.Pt/Ce1Al10 catalyst exhibited the highest catalytic activity than other catalysts in selective hydrogenation reaction of 2-pentenal.Combined with XPS and H₂-TPR results,this enhanced activity of Pt/Ce1Al10 catalyst resulted from strong metal-support interactions（SMSI）.Interestingly,we also found that the Pt/Ce1Al10 and Pt/CeO₂catalysts were favorable for the hydrogenation of C=O double bonds to produce the product 2-pentenol,whereas for the Pt/Ce10Al1,Pt/Ce1Al1 and Pt/Al₂O₃catalysts were more favorable for hydrogenation of the C=C double bonds to produce n-pentenaldehyde.