Rh Nanoparticle And Ir/Rh Bimetallic Nanoparticle Catalyzed Chemoselective Hydrogenation Of Cinnamaldehyde In The Thermoregulated PEG Biphasic System

Soluble Rh nanoparticles and Ir/Rh bimetallic nanoparticles were prepared by hydrogen reduction of RhCl3?3H2O and IrCl3?xH2O in the presence of polyethylene glycol (PEG), which acted as not only the solvent but also the stabilizer. TEM analysis showed that the diameter of Rh nanoparticles in PEG 4000 (Mw= 4000) was 1.7 nm, and the diameter of Ir/Rh bimetallic nanoparticles in PEG 2000 (Mw= 2000) was 1.9 nm. Both of them were emplyed as the catalysts for the chemoselective hydrogenation of cinnamaldehyde in the thermoregulated PEG biphasic system. The activity, chemoselectivity, recovery and recycling efficiency of the catalysts were investigated.PEG 4000-stabilized Rh nanoparticles were employed as the catalyst for the chemoselective hydrogenation of cinnamaldehyde in the thermoregulated PEG biphasic system. The effects of reaction temperture, the pressure of H2, reaction time and the molar ratio of cinnamaldehyde to Rh were investigated in detail. And here Rh nanoparticles mainly show high chemoselectivity to C=C double bond in the molecule of cinnamaldehyde. Under the optimized reaction conditions:T= 130 ?,t= 2h, Ph2= 4 MPa, cinnamaldehyde/Rh= 400 (molar ratio), the conversion of cinnamaldehyde and the selectivity of hydrocinnamaldehde were 98% and>99%, respectively. The catalyst could be reused for 10 times without evident loss in activity and chemoselectivity.PEG 2000-stabilized Ir/Rh bimetallic nanoparticles were employed as the catalyst for the chemoselective hydrogenation of cinnamaldehyde in the thermoregulated PEG biphasic system. The effects of the molar ratio of Ir to Rh, reaction temperture, the pressure of H2, reaction time and the molar ratio of cinnamaldehyde to Ir/Rh were investigated in detail. And Ir/Rh bimetallic nanoparticles mainly show high chemoselectivity to C=O double bond in the molecule of cinnamaldehyde in here. Under the optimized reaction conditions:T= 130 ?, t= 3 h, Ph2= 4 MPa, cinnamaldehyde/(Ir/Rh)= 400 (molar ratio), the conversion of cinnamaldehyde and the selectivity of cinnamyl alcohol were 98% and 91%, respectively. The catalyst could be reused for 14 times without evident loss in activity and selectivity.