Synthesis And Application Of Rhodium And Palladium/Rhodium Nanoparticles Stabilized By Ammonium-based Ionic Liquid With Polyether Chain

Ammonium-based ionic liquids with polyether chain [CH3(OCH2CH2)12N+Et3SO3-CH3 (IL550)] was used as stabilizer for preparation of Rh and Pd/Rh nano-particles by hydrogen reduction of corresponding transition-metal salts at room temperature. TEM images showed that the average size of Rh nanoparticles was 1.0 nm with standard deviation of 0.2nm. The average size of Pd/Rh bimetallic nanoparticles was 3.5 nm with standard deviation of 0.4 nm.The Rh nanoparticles stabilized by IL550 were used as catalyst for the hydrogenation of styrene at room temperature. The effects of reaction time, hydrogen pressure, the ratio of Rh/IL55o and the amount of solvent on the reaction were investigated. Under the optimized reaction conditions (T=25℃, t=90 min, P=2.0 MPa, styrene/Rh=5000:1 (molar ratio), IL550/Rh=100:1 (molar ratio), n-heptane=1g), both the conversion of styrene and the yield of ethylbenzene were 100%. The Rh nanoparticle catalyst could be recycled 8 times without any loss in activity. After 8 recycles, the average size of Rh nanoparticles was the same to those of freshly prepared. The average of loss of Rh was under 0.08%(wt%).IL550-stabilized Pd and Rh bimetallic nanoparticle catalysts were used for the selective hydrogenation of 1,5-cyclooctadiene. The effects of reaction time, hydrogen pressure, the molar ratio of Pd/Rh and the molar ratio of 1,5-COD/catalyst on the reaction were investigated. Under the optimized reaction conditions (T=25℃, t=4h, P=4.0 MPa, Pd/Rh =5:1 (molar ratio),1,5-COD/catalyst=1000:1 (molar ratio)), the conversion of 1,5-COD was 97% and the selectivity of cyclooctene was 79%. The activity of the Pd/Rh nanoparticle catalyst was higher than Rh nanoparticle catalyst and the selectivity of the catalyst was higher than Pd nanoparticles. The ILsso-stabilized Pd/Rh bimetallic nanoparticle catalyst could be reused for 10 times. After 10 recycles, the average size of Pd/Rh the nanoparticles remained nearly the the same. The loss of Pd and Rh was 0.04% and 0.72%(wt%) respectively.