Synthesis Of Palladium Nanoparticle Catalyst For Hydrogenation In The Thermoregulated PEG/Toluene/n-Heptane Biphase System

PEG 4000-stabilized palladium nanoparticle catalyst was prepared by reduction of Pd(OAc)2 with PEG 4000 as reductant in the thermoregulated PEG 4000/Toluene/n-Heptane biphase system. TEM analysis showed that the average size of the palladium nanoparticles was 2.7 nm and the standard deviation was 0.4 nm. The catalyst could dissolve in the PEG4000 phase but insoluble in the upper organic phase(mixture of toluene and n-heptane) at room temperature. During the reaction, the catalyst could be dissolved in the PEG4000/Toluene/n-Heptane monophase system when the reaction temperature was above the miscible temperature. The PEG 4000-stabilized palladium nanoparticle catalyst was characterized by the homogeneous reaction coupled with biphase separation. The PEG4000-Stabilized Palladium Nanoparticle Catalyst was used to catalyze the hydrogenation of styrene. The effects of reaction temperature, time and the ratio of styrene/Pd on the reaction have been investigated in detail. Under the optimized reaction conditions (T=70℃, t=20 min, P(H2)=1 MPa, styrene/Pd=1000:1 (molar ratio)), the conversion of styrene and the yield of ethylbenzene were 100% with TOF of 3000 h-1. The PEG 4000-Stabilized Palladium Nanoparticle Catalyst could be used for six times without loss in activity.The PEG4000-Stabilized Palladium Nanoparticle Catalyst was also used to catalyze the hydrogenation of cyclohexene. Under the optimized reaction conditions (T=80℃, t=90 min, P(H2)=4 MPa, cyclohexene/Pd=1000:1 (molar ratio)), the conversion of cyclohexene and the yield of cyclohexane were 83%. The PEG 4000-Stabilized Palladium Nanoparticle Catalyst could be used for seven times.Meanwhile, the activity nearly keep the same.PEG 2000-stabilized palladium nanoparticle catalyst was prepared by the reduction of Pd(OAc)2 with PEG 2000 as reductant in the thermoregulated PEG 2000/Toluene/n-Heptane biphase system. TEM analysis showed that the average size of the PEG 2000-Stabilized palladium nanoparticles was 2.6 nm and the standard deviation was 0.4 nm. The PEG 2000-Stabilized palladium nanoparticle catalyst was also characterized by the homogeneous reaction coupled with biphase separation. The PEG 2000-stabilized palladium nanoparticle catalyst was used to catalyze the selective hydrogenation of 1,5-COD. Under the optimized reaction conditions (T=70℃, t=40 min, P(H2)=1 MPa,1,5-COD/Pd=1000:1 (molar ratio)), the conversion of 1,5-COD was 100% and the selectivity of COE was 99%. The PEG 2000-stabilized palladium nanoparticle catalyst could be used for eleven times without loss in activity.