Preparation Of Au-based MOFs Bifunctional Catalysts And Its Reaction Performance Of CO₂ With Amine/H₂

In recent years,the CO2 content in the air has been too high,and the greenhouse effect has become more and more serious.The use of CO2 as the C1 raw material can not only reduce the CO2 content,but also produce high-value chemicals such as formic acid,methylene low olefins and N-formylation(N-methylation)products.Among them,the N-methylation reaction of CO2 and amine/H2 is a relatively novel method of utilizing CO2.The following MOFs were prepared by solvothermal method:MIL-101(Cr),UiO-66(Zr),NH2-MIL-101(Al),MIL-100(Cr),MIL-100(Fe).The corresponding Au-based MOFs catalysts were prepared by supporting Au.Au-Pd,Au-Pt,Au-Cu,and Au-Ru bimetallic catalysts were prepared by using MIL-101(Cr)as a carrier.Through acid modification,Au/MIL-101(Cr)-HSO3 and Au/HPW@MIL-101(Cr)catalysts were prepared.The nature of the catalyst was characterized by XRD,BET,FT-IR,SEM,HRTEM,and XPS.In the kettle reactor,the N-methylation reaction of CO2 and aniline/H2 was evaluated,and the reaction conditions were optimized.The specific results were as follows:(1)Au-based MOFs catalysts:Au-based MOFs catalysts were prepared using MIL-101(Cr),UiO-66(Zr),NH2-MIL-101(Al),MIL-100(Cr),and MIL-100(Fe)as supports.The loaded Au was evenly dispersed and the particle size was concentrated between 4 nm and 6 nm.The XRD diffraction peak was basically consistent with the corresponding simulated peak.Using Au/MIL-101(Cr)as a catalyst to optimize the reaction conditions,the aniline conversion rate can reach 47.28%,the yield of N-methylaniline was 32.66%,and the selectivity of N-methylaniline was 69.08%.(2)Modified metal component catalysts:Using MIL-101(Cr)as the carrier,Au-Pd,Au-Pt,Au-Cu,Au-Ni,Au-Ru bimetal catalysts were prepared.For the Au-Pd/MIL-101(Cr)bimetal catalyst,the supported precious metal Au and Pd particles were basically zero-valent.The precious metal particle size was concentratedly distributed between 3 nm and 5 nm.The metal particle distribution was more uniform.Using Au-Pd/MIL-101(Cr)as a catalyst,the reaction conditions were optimized.The aniline conversion rate can reach 37.72%.The yield of N-methylaniline was 36.03%,and the selectivity of N-methylaniline was 95.52%.(3)Acid modified MOFs catalysts:2wt%Au/MIL-101(Cr)-HSO3 catalyst was prepared.For the N-methylation reaction of CO2 and aniline/H2,the conversion of aniline was 21.71%,and the yield of N-methylaniline was 17.42%.Compared with before modification,the yield was reduced by 15.24%.2wt%Au/HPW@MIL-101(Cr)catalyst was prepared.The aniline conversion was 30.34%and the selectivity of N-methylaniline was 81.04%.Compared with before modification,the selectivity was improved by 11.96%.