Preparation Of Pd / C Catalyst By Plasma And Catalytic Suzuki Coupling Reaction

Palladium nanoparticles were prepared by impregnation-glow discharge plasma reduction method（Pd/C-P） using different plasma-forming gas with activated carbon as the carrier and Na₂PdCl₄ as the palladium source. The impact of various preparation conditions such as the system pressure, discharge time and discharge power on the pore structure, morphology and particle size distribution of the catalyst and the catalytic activity were studied. The as-prepared Pd/C catalysts were characterized by UV-Vis, N2 adsorption-desorption, XRD, TEM and XPS analysis. The catalytic activity of Pd/C-P catalysts was examined using the Suzuki coupling reactions of aryl bromides and phenylboronic acid.The Pd nanoparticles were prepared by glow discharge plasma using air as plasma-forming gas. The best catalytic results under these preparation conditions, including the system pressure is 80 Pa, discharge time is 15 min and discharge power is 550 W. The as-prepared Pd nanoparticles are mainly for Pd（111） and match well with face centred cubic structure. The Pd nanoparticles have a broader size distribution of 4.76 nm-47.86 nm and an average diameter of about 23.27 nm. A 96.80% yield for the Suzuki coupling reaction of 4-bromotoluene with phenylboronic acid in the presence of 0.5‰ catalyst for substrate is obtained. After three repeated cycles, the yield falls to 84.85%.The Pd nanoparticles were prepared by glow discharge plasma using N₂ as plasma-forming gas. The best catalytic results under these preparation conditions, including the system pressure is 80 Pa, discharge time is 15 min and discharge power is 440 W. The as-prepared Pd nanoparticles are mainly for Pd（111） and match well with face centred cubic structure. The Pd nanoparticles have a distribution of 1.96 nm-11.99 nm and an average diameter of about 6.89 nm. A 98.06% yield for the Suzuki coupling reaction of 4-bromotoluene with phenylboronic acid in the presence of 0.5‰ catalyst for substrate is obtained. There was no obvious loss of catalytic activity after five repeated cycles.The Pd nanoparticles were prepared by glow discharge plasma using Ar as plasma-forming gas. The best catalytic results under these preparation conditions, including the system pressure is 100 Pa, discharge time is 60 min and discharge power is 440 W. The as-prepared Pd nanoparticles are mainly for Pd（111） and match well with face centred cubic structure. The Pd nanoparticles have a narrow distribution range from 2.17-7.39 nm with an average particle size of 3.56 nm. The yield can reach 97.88% for the Suzuki coupling reaction of 4-bromotoluene with phenylboronic acid in the presence of 0.3‰ catalyst for substrate and no obvious loss of catalytic activity even after eight repeated cycles.The results showed that the Pd/C-P catalyst prepared by Ar glow discharge plasma has smaller particles size and exhibit better catalytic activity and recyclability in Suzuki coupling reactions.