A Magnetic Nano-Rh Catalyst:Design,Preparation And Its Performance In Catalytic Hydroformylation Reaction

Hydroformylation is one of the largest homogeneous catalytic reactions in the industry.Low-carbon olefins have been efficiently catalyzed by a mature low pressure hydroformylation process(LP Oxo^SM process)and a water-organic two-phase hydroformylation process（RCH/RP process）,products and catalysts can be easily separated.However,due to the defects of above two processes,they cannot be applied to high-carbon olefins.Most of the high-carbon olefins are also subjected to cobalt catalysis with harsh reaction conditions and low catalytic activity at present.Therefore,how to apply ruthenium catalysts to high-carbon olefins hydroformylation reaction and realize high-efficiency separation and recovery of ruthenium catalysts have become a hot research topic.Magnetic nanoparticles with unique superparamagnetism provide the possibility to separate and recover catalytic species loading on their surfaces rapidly.Magnetic nanoparticles were synthesized by coprecipitation method successfully.Magnetic nano-Rh catalyst was prepared via direct-loading of Rh on to the surfaces of magnetic nanoparticles.The catalysts morphology and Rh content were determined by TEM,EDAX and ICP-AES methods.The influences of ultrasonic time and mass ratio of Rh and iron oxide on the Rh content and Rh recovery in the catalyst were investigated.The effect of different solvents on the Rh dispersibility of the catalyst was investigated at the same time.It is easier to prepare a magnetic nano-Rh catalyst with high dispersion of Rh on the surface of iron oxide by using water as solvent than using isopropyl alcohol as solvent.The optimal preparation condition was obtained:water as solvent,10 min as ultrasonic time,RhCl₃·3H₂O:Fe₃O₄=9.6:416（mass ratio）.A magnetic nano-Rh catalyst with low Rh loading and good catalytic performance was prepared,the recovery of Rh was 60%.It is used to catalyze the hydroformylation of styrene,and to explore the influences of time,temperature,pressure and the amount of Rh in the catalyst.The optimal reaction condition was obtained:120°C,4 MPa（CO:H₂=1:1）,6 h.It was found that the catalytic performance of the catalyst with low Rh loading was much higher than that with high Rh loading.Reducing the molar ratio of Rh and substrate to 1:10000 can increase the TOF to 1454 h^-1.At the same time,the prepared magnetic nano-Rh catalyst was applied to catalyze the 1-pentene and1-hexene hydroformylation reactions with yields of 89%and 83%.The problem of the loss of Rh was found when exploring cyclic catalytic efficiency of the catalyst.A new concept of hydroformylation reactions under the gas phase condition of the magnetic nano Rh catalyst in fixed bed was proposed.The specific surface and pore diameter of the catalyst after tabletting were detected and analyzed.It was found that tabletting did not change the original surface area of the catalyst,and the formed pores were suitable for the passage of olefins.The influence factors of catalyst formation and the influence of reaction conditions on the hydroformylation reaction of the fixed bed were investigated.It was found that the temperature had little effect on the reaction and the pressure had a great influence on the reaction.The application of the magnetic nano-Rh catalyst in the liquid phase of the high-pressure reactor and the gas phase of the fixed bed are expected to solve the harsh reaction conditions,poor catalytic performance of industrial high-carbon olefin hydroformylation reaction,loss of catalyst,environmental pollutions and other issues.