Study On Micro-mesoporous Zeolite Confined Double-active Site Catalyst And Its Catalytic Hydrogenation

As the name implies,the double active sites are composed of two different active centers.Their unique properties and diverse applications have attracted the attention of researchers.Double active sites have a series of superior and different properties compared with a single active site.The synergistic effect between the two active centers,electronic effects such as charge transfer,smaller size and better dispersion make it a highly sought-after catalytic material.In this paper,the construction of efficient and stable dual-active site catalyst based on microporous TS-1 molecular sieve and its application in catalytic hydrogenation direction are studied.The synergistic effect of dual-active sites is regulated by means of phase regulation,structure regulation and alloying effect,so as to improve the intrinsic catalytic activity of the catalyst.The main contents are divided into the following three aspects:(1)Using microporous TS-1 zeolite as seed,the seed-assisted synthesis method was used to accelerate the etching and crystallization speed,and less structure directing agent(TPAOH)and adjustable etching and crystallization behavior were used to generate mesoporous zeolite particles in the seed.Through this strategy,the zeolite can be transformed into crystal and pore-forming in the crystal without mesoporous agent and less TPAOH,and the active site(acid site)can be obtained more easily in the open position of mesoporous in the crystal.Then,noble metal Pt was deposited on zeolite catalyst by ALD deposition technology,and a mesoporous catalyst with double active sites of metal site and acid site was constructed.During the process of etching and crystallization,the acid site of the catalyst changed greatly,and it has excellent catalytic activity in furfural hydrogenation.(2)In this work,we constructed a bimetallic mesoporous core-shell structure catalyst(Pt-Au/TDMSN),which realized the space-limited,two-zone synergistic catalysis and improved the activity and selectivity of semi-hydrogenation reaction.During the hydrogenation process,due to the adsorption of Au in the mesopores,the rate of active hydrogen species overflowing to Au increases,and the reaction with the reaction substrate adsorbed on Au increases the hydrogenation rate,isolating the substrate from the active site and preventing direct contact,thereby greatly improving the activity and selectivity of the reaction.This work elucidates the synergistic effect of Pt and Au NPs in Pt-Au/TDMSN catalysts and proposes a tandem working mechanism with dual active centers.(3)Limited by the specific electronic structure and single active center of a single metal,it does not show high selectivity for some catalytic reactions.Bimetallic alloy catalyst has become a new research hotspot in bimetallic catalysts because of its high utilization efficiency of precious metals,adjustable geometry and electronic structure,unique active center and outstanding catalytic performance.In this work,a mesoporous zeolite molecule(Pt Ru/TDMSN)with platinum-ruthenium bimetallic alloy was designed and synthesized.First,Pt Ru nanoparticles are confined to TS-1 microporous molecular sieve channels,which ensures nanoscale dispersion.Then,in order to improve the transmission efficiency,Pt Ru/TS-1 microporous molecular sieve was embedded in the dendritic mesoporous silica wall(DMSN).This catalyst successfully solved the shortcoming of easy agglomeration of noble metal catalysts and retained the high catalytic activity and selectivity of bimetallic alloys.At the same time,we studied the influence of different alloy proportions on the interaction between two metals.