Preparation Of The Supported Magnetic Catalysts And Catalytic Reduction Of Carbon Dioxide

With the burning of chemical fuels,the content of carbon dioxide in the atmosphere is higher and higher.Carbon dioxide is a kind of greenhouse gas which can seriously affect the survival and development of mankind.Therefore,it is very important to reduce the concentration of carbon dioxide in atmosphere and transforming carbon dioxide to high value-added chemicals such as methanol and formic acid by catalytic reduction has been widely concerned.In the catalytic reduction of carbon dioxide,carbon dioxide can be immobilized to formyl and methyl through N-formylation reaction and N-methylation reaction using amines as reactant and hydrogen as reducing agent.This reaction has important research value.In this paper,Pd/Cu-BTC and Au/γ-Al₂O₃ were prepared by sol-gel method.Supported magnetic catalysts Pd/Cu-BTC@SiO₂@Fe₃O₄ and Au/γ-Al₂O₃@Fe₃O₄ were also prepared.The catalysts were characterized by XRD,FT-IR,HRTEM,SEM,BET,XPS and VSM.Supported palladium catalyst and supported gold catalyst were applied to the N-formylation and N-methylation reaction using aniline and CO₂/H₂ as reactant to synthesize formanilide and N-methylaniline respectively.The results were as follows:（1）A series of Pd/Cu-BTC catalysts with different palladium percent were prepared.The palladium nanoparticles with zero-valent were homogeneously dispersed on Cu-BTC and the average particle size is 4.5 nm.Then I optimized the reaction conditions,the best reaction condition is 3wt%Pd/Cu-BTC,40 mg catalyst,7 h,160℃,0.2 MPa CO₂ and 0.2 MPa H₂.The conversion of aniline is 29.80%and the selectivity of formanilide is nearly 100%.The catalyst shows excellent reusability,the conversion of aniline is 27.48%and the selectivity of formanilide is also nearly 100%after 5 times reuse.Then I find that the magnetic catalyst has high saturated magnetic field with 42.2 emu/g which can be separated under the effect of external magnetic field.It has good catalytic performance.The conversion of aniline is over 25%and the selectivity of formanilide is also nearly 100%after 5 times reuses using 3wt%Pd/Cu-BTC@SiO₂@Fe₃O₄ as catalyst.（2）A series of Au/γ-Al₂O₃ catalysts with different gold percent were prepared.The gold nanoparticles with zero-valent were homogeneously dispersed on γ-Al₂O₃ and the average particle size is 4.4 nm.Then I optimize the reaction conditions,the best reaction condition is 80 mg 4wt%Al/γ-Al₂O₃,10 h,180℃,1.5 MPa CO₂ and 2.5 MPa H₂.The conversion of aniline is 32.86%and the yield of N-methylaniline is 19.37%.The catalyst shows excellent reusability,the conversion of aniline is 31.52%and the yield of N-methylaniline is 17.84%after 5 times reuse.Then I prepared bimetallic catalyst such as AuCu/γ-Al₂O₃,AuNi/γ-Al₂O₃,AuRu/γ-Al₂O₃,AuPd/γ-Al₂O₃ and used them in catalytic reaction,only AuPd/γ-Al₂O₃ shows excellent catalytic performance.The magnetic catalyst has high saturated magnetic field with 56.3 emu/g which can be separated under the effect of external magnetic field.It has good catalytic performance.The conversion of aniline is over 29%and the yield of N-methylaniline can come to 16%after 5 times reuses using 4wt%Au/γ-Al₂O₃@Fe₃O₄ as catalyst.