Aqueous/Organic Biphasic System To Effect Thermoregulated Phase-transfer Property Of Rhodium Nanoparticles And Its Application

Rhodium nanoparticles stabilized by thermoregulated ligand Ph2P(CH2CH2O)CH3 (n= 22) (L) were prepared by hydrogenation reduction. The rhodium nanoparticle catalyst stabilized by thermoregulated ligand L exhibited the thermoregulated phase-transfer property in the aqueous/1-pentanol, aqueous/1-butanol and aqueous/ethyl acetate biphasic systems. Take aqueous/1-pentanol biphasic system as an example, the rhodium nanoparticle catalyst was in the lower water phase at room temperature, afterwards, when the temperature heated to 60℃, the rhodium nanoparticle catalyst transferred from the water phase into the upper 1-pentanol phase, after cooling to room temperature, the rhodium nanoparticle catalyst could go back to the lower water phase from the upper 1-pentanol phase.The thermoregulated phase-transfer rhodium nanoparticle catalyst was used to catalyze hydrogenation of olefins in the aqueous/1-pentanol biphasic system. For the hydrogenation of cyclohexene, under the optimized reaction conditions of S/Rh=1000(molar ratio), T=60℃, PH2=1 MPa, t=1h, the conversion of cyclohexene reached up to 99%.Catalytic activity remained unchanged within eight successive runs. The average leaching of rhodium to the product phase was 0.1%(wt.%).We extended the application of the thermoregulated phase-transfer rhodium nanoparticle catalyst to the selective reduction of nitroarenes in the aqueous/1-pentanol biphasic system. For the selective reduction of o-chloronitrobenzene (o-CNB), under the optimized reaction conditions of S/Rh=1000(molar ratio), T=70℃, PH2=3 MPa, t=2 h, the conversion of o-CNB and the selectivity of o-chloroaniline (o-CAN) were 100% and 98%, respectively. The catalyst could be easily separated from product by phase separation and used for eight times without decrease in conversion and selectivity was above 91%.