Hydroformylation Of Olefins By A Fe₃O₄-Rh Heterogeneous Nanocrystalline Catalyst With High Efficiency And Easy Recovery

Olefin hydroformylation is the formation of aldehydes by olefins and synthesis gas under the action of a catalyst.It is widely used in the synthesis of bulk chemicals such as alcohols,lipids,amines,and is of great significance for the production of fine chemicals.Due to the advantages of high catalytic activity and excellent chemical selectivity in catalytic hydroformylation,the complex formed by rhodium（Rh）and phosphine ligands is a homogeneous catalyst widely used in this reaction.However,homogeneous catalysts still have many problems such as separation difficulties,cumbersome recovery process,catalyst loss,and regeneration difficulties,which increase energy consumption and pollution,and raise the cost of industrial production.Therefore,the development of an Rh-based catalyst with high catalytic activity and easy recovery has become a hot topic in the chemical industry.Because of its superior catalytic activity and easier recovery than traditional homogeneous catalysts,nanocatalysts have a greater advantage in industrial catalysis.In this study,we prepared 3.0 wt%Fe₃O₄@SiO₂-Rh NPs nanocatalysts by chemically impregnating Rh nanoparticles on silica-coated ferroferric oxide nanoparticles（Fe₃O₄@SiO₂）.During the hydroformylation of butene,the nanocatalysts achieve the higher yield（92.5%）and n-valeraldehyde selectivity（66.6%）.And after 6 cycles of reaction,the yield and selectivity were not significantly reduced.In addition,the Fe₃O₄core gives the composite catalyst magnetic control.Under the action of an external magnetic field,the Fe₃O₄@SiO₂-Rh NPs nanocatalyst can be easily separated from the reaction system,which greatly improves the catalyst recovery efficiency.Single-atom catalyst has the highest atom utilization rate,and its unsaturated coordinated active center can significantly improve the catalytic activity.Here,we further prepared Rh monoatomic catalysts based on Fe₃O₄@por SiO₂-P（Rh/Fe₃O₄@por SiO₂-P SACs）,and analyzed the atomic structure of the catalyst using HAADE-STEM and other characterization technology systems.In the olefin hydroformylation experiment,the single-atom catalyst exhibited higher reactivity（TON=18500）and selectivity（89.6%）,which was comparable to the RhCl（PPh₃）₃ homogeneous catalyst（TON=19000）.Rh/Fe₃O₄@por Si O₂-P SACs show excellent stability.Under the action of external magnetic field,the catalyst can be easily separated and recovered,and it still maintains a high catalytic activity after 6 cycles of use.The single-atom catalyst is expected to be further used in industrial catalysis to achieve high-atom economic green catalysis.