Design And Preparation Of Mesoporous Metal Catalyst For Tandem Catalysis

Tandem catalysis can combine a variety of chemical transformations without the need to separate,purify and transfer intermediate products,thereby saving costs and reducing waste.Many advantages have attracted more and more attention.Tandem catalysis also presents a synthetic challenge,requiring precise control of the composition,morphology,and interface structure of the nanostructured catalyst to combine the active sites of the two reactions proceed efficiently.So far,the research of tandem catalysis has achieved certain results,which can be classified according to different tandem mechanisms.In this paper,research has been carried out on the tandem catalysis of mesoporous rhodium.In the second chapter,the preparation and structure control of rhodium-based mesoporous metal catalysts are introduced.First,we use the iodine ion strong ability of coordination,reinforced metal ions and the interaction between surfactants and the method of using this synergy self-assembly,were highly uniform mesoporous rhodium nanoparticles morphology size,the material has good crystallinity,the ordered mesoporous structure and high specific surface area(80 m²g^-1);Mediated by seed growth strategy,and realized the control of the size of mesoporous rhodium nanoparticles,by changing the parameters of the accumulation of surface active agent,has realized the mesoporous rhodium nanoparticles,mesoporous structure regulation,respectively the rhodium nanoparticles unordered accumulation pore structure is prepared,the divergent type rhodium nanoparticles of the mesoporous structure and 3D mesh of rhodium nanoparticles,mesoporous structure by introducing a second metal precursor,preparation with different proportion of mesoporous metal Rh-Ru dual alloy nanoparticles,Ru particles within a large number of irregular spongiform nanometer pore structure,and the preparation of Rh Ru-MPSs samples with good crystallinity.In the third chapter,the catalytic behavior of mesoporous rhodium catalyst in the tandem reaction of continuous hydrogenation of nitroaromatic hydrocarbons to acyclic amines was studied.It not only realized the efficient conversion of nitroaromatic hydrocarbons to acyclic amines,but also proposed the limiting effect of the ordered pores of metal catalyst on the reaction intermediate.First,under mild reaction conditions(80 ^oC,2.0 MPa H₂),using ethanol as solvent,the yield of cyclohexylamine can reach more than 99%at 1.0 h,and the TOFs can reach 1170 h^-1,which is much higher than that of the corresponding non-porous rhodium-based catalyst and other metal catalysts.Then,combined with the study of reaction kinetics,it is found that the mesoporous pores of metal rhodium catalyst can effectively prolong the residence time of intermediate aniline molecules in the pores,and thus greatly enhance its catalytic efficiency in continuous hydrogenation reaction.Again,by studying the intermediate aniline molecules found in different catalyst of TPD,aniline molecules on the surface of the mesoporous rhodium catalysts,stripping temperature is much higher than no hole rhodium catalysts,and with the increase of the mesoporous rhodium nanoparticles,mesoporous channel,stripping of aniline molecules further increases in temperature,which directly prove the mesoporous mesoporous channel of rhodium catalyst in the role of the confined reaction intermediates.Finally,the study shows that mesoporous rhodium catalyst has good substrate applicability and excellent catalytic stability in the continuous hydrogenation of nitroaromatic hydrocarbons,and the yield of cyclohexylamine can still reach 95%after 10 cycles.