Preparation And Catalytic Performance Testing Of Highly Stable NiAl₃-Ni And Ni₂Al₃-Ni Composite Catalyst

Raney Ni is a nickel-based catalyst with skeleton structure,which has the advantages of high catalytic activity,simple preparation process and low cost,and is widely used in various hydrogenation reactions.However,Raney Ni is poorly stabilized in air,and in addition,the hydrogenation performance of Raney Ni is lower than that of precious metals such as Pd and Pt in terms of catalytic performance.In recent years,studies on Raney Ni catalysts have mainly focused on improving the catalytic activity of Raney Ni by elemental doping and changing the electronic state of the active site,and less studies have been conducted on the stability of Raney Ni.Compared with alloys and monometals,intermetallic compounds have long-range ordered structures,which give them better stability and catalytic performance,and have been verified in several catalytic reactions.Therefore,in this thesis,Ni-Al intermetallic compounds were introduced into Raney Ni catalysts to enhance their catalytic performance and stability.The specific research results are as follows:（1）Preparation and catalytic activity and stability study of Ni Al₃-Ni composite catalysts with high Al content intermetallic compounds.The Ni Al₃-Ni composite catalyst was obtained by controlling the Ni/Al ratio and melting process to obtain a uniformly mixed alloy precursor of Ni Al₃+Al,and by controlling the corrosion process to achieve the complete removal of Al and partial removal of Ni Al₃ using the difference in reactivity between Ni Al₃ and Al.Ni Al₃-Ni has a porous structure with The pore size～4 nm and specific surface area of 106 m²/g.The results of differential thermal analysis tests of the Ni Al₃-Ni composite showed that the stability of the Ni Al₃-Ni composite in air was significantly improved compared with that of the Raney Ni catalyst.The catalytic activity of Ni Al₃-Ni composite catalysts was generally higher than that of Raney Ni catalysts and nanoporous nickel catalysts,indicating that the electronic structure change caused by the introduction of Ni Al₃ intermetallic compounds enhanced the ability of Ni Al₃-Ni to activate hydrogen,to catalyze the reaction intermediates,which helps to improve the catalytic performance.（2）Preparation,catalytic activity and stability of Ni₂Al₃-Ni composite catalysts with corrosion-resistant intermetallic compounds.The Ni₂Al₃-Ni composite catalyst was obtained by regulating the Ni/Al ratio in the alloy and the melting process to obtain a uniformly mixed alloy precursor of Ni Al₃+Ni₂Al₃;the differences in the reactivity of Ni Al₃ and Ni₂Al₃ were used to achieve the complete removal of Al from Ni Al₃ through a controlled corrosion process to obtain a Ni₂Al₃-Ni i composite catalyst.has a porous structure with a pore size～6 nm and a specific surface area of 80 m²/g.The results of differential thermal analysis tests of the Ni₂Al₃-Ni composite showed that its stability in air was basically comparable to that of the Ni Al₃-Ni composite.More importantly,the results of catalytic activity tests for the hydrogenation of phenylacetylene and 1,4-butynediol showed that the catalytic activity of the Ni₂Al₃-Ni composite catalysts was generally higher than that of Ni Al₃-Ni,especially the selectivity against 1,4-butanediol in the hydrogenation of 1,4-butynediol was as high as 99.6%,and the cyclic stability of the catalytic reaction was also significantly enhanced,indicating that the corrosion-resistant intermetallic The introduction of the corrosion-resistant intermetallic Ni₂Al₃compound not only improved the catalytic activity,selectivity and stability in air of the Raney Ni catalyst,but also enhanced the catalytic stability of the catalyst.In conclusion,the technical solution to improve the stability of Raney Ni catalyst in air while maintaining the catalytic activity of the catalyst by introducing intermetallic compounds is feasible,and the results of this thesis provide a new idea for the development of highly stable catalysts.