Constructing Liquid-Solid Hybrid Catalyst For Bridging Homogenous And Heterogeneous Hydroformylation

Hydroformylation of alkenes is an industrial and atomically economical reaction to produce aldehyde products.This reaction involves the utilization of alkenes and syngas as raw materials,hydrogen atom and formyl group are added to the two ends of the carbon-carbon double bond under the catalysis of transition metal cobalt or precious metal rhodium,forming aldehyde compounds,which can be further processed into high value-added products such as alcohols,carboxylic acids,amines,hydroxylaldehydes et.al.At present,homogeneous hydroformylation catalysis is the main method in industry,which has the advantages of high reactivity and good selectivity.However,it faces challenges such as product separation,catalyst recycling and continuous production.In contrast,heterogeneous catalysis has the advantages of easy separation of catalyst from reaction system and continuous operation.Therefore,it is an important mean to solve the above bottleneck problems by immobilizing the homogeneous hydroformylation catalyst.In this thesis,aiming at the ionic liquid-medium olefin hydroformylation reaction process,we proposed a liquid-solid hybrid catalytic material,in which the homogeneous catalytic system was dispersed into countless tiny droplets by using the confined microspace of silica shell.During the catalysis process,the reaction was homogeneous from a microscopic point of view,while it also possesses the advantage of recycling solid catalytic materials from a macroscopic point of view.This study provides a new method for bridging the homogeneous and heterogeneous hydroformylation catalysis.The main results obtained are summarized as follows:（1）Construction of liquid-solid hybrid micro-spherical catalyst.A liquid-solid hybrid catalyst with an ionic liquid core and silica shell was prepared via interfacial growth of a porous silica crust around Pickering emulsion droplets,and the rhodium-based molecular catalyst was encapsulated in situ in the material.The microsphere materials with different interior media（including[BMIM]PF₆,[BMIM]NTf₂and[BMIM]BF₄,etc.）and chemical microenvironment were obtained by regulating the types of internal ionic liquids.The size of hybrid microspheres（16-50μm）and shell thickness（60-170 nm）were controlled by tunning the size of Pickering drops and the amount of crosslinking agent.Meanwhile,the good thermal stability and solvent tolerance of the material were investigated by the corresponding experiments,and the rapid molecular diffusion and exchange ability of the material was verified by fluorescence permeability experiment.（2）Application of olefin hydroformylation reaction.Due to the enlarged liquid-liquid reaction interface and free state of the molecular catalyst,the constructed solid-liquid hybrid microspheres showed significantly enhanced catalytic performance compared with the traditional biphasic reaction system in the hydroformylation of 1-dodecene.By adjusting the type of liquid pool,particle size,shell thickness,internal molecular catalyst type and other parameters,the regulation and optimization of catalytic performance were realized,and the structure-activity relationship between the corresponding catalyst structure and reaction performance was preliminarily obtained.The composition and P/Rh ratio of rhodium ligand were also studied,and it was found that above 99%conversion was achieved within 5 h,while 93.1%of aldehyde selectivity and 38.3 of aldehyde isomerization ratio were got by using Sulfoxantphos as ligand.The solid-liquid hybrid microspheres also showed good substrate applicability,and can be applied to 1-octadecene,1-decene,1-octene,1-heptene and other substrates,and exhibited much better catalytic performance than the traditional biphasic reaction systems.In addition,the micron-scale catalytic material has good stability,which can be recycled more than 7 times,and maintained more than 80%of activity and selectivity.