Pd Nanoparticles-Loaded Vinyl Polymer Gels: Preparation, Structure and Catalysis

Four vinyl polymer gels (VPGs) were synthesized by free radical polymerization of divinylbenzene, ethane-1,2-diyl dimethacrylate, and copolymerization of divinylbenzene with styrene, and ethane-1,2-diyl dimethacrylate with methyl methacrylate, as supports for palladium nanoparticles. VPGs obtained from divinylbenzene and from divinylbenzene with styrene had spherical shapes while those obtained from ethane-1,2-diyl dimethacrylate and from ethane-1,2-diyl dimethacrylate with methyl methacrylate did not have any specific shapes. Pd(OAc)₂ was impregnated onto VPGs and reduced to form Pd⁰ nanoparticles within VPGs. The structures of Pd⁰-loaded VPGs were analyzed by XRD, TEM, and nitrogen gas adsorption. Pd⁰-loaded VPGs had nanocrystals of Pd⁰ within and on the surface of the polymeric supports. Pd⁰/VPGs efficiently catalyzed the oxidation/disproportionation of benzyl alcohol into benzaldehyde/toluene, where activity and selectivity between benzaldehyde and toluene varied, depending on the structure of VPG and the weight percentage loading of Pd⁰. The catalysts were stable and Pd leaching to liquid phase did not occur. The catalysts were separated and reused for five times without any significant decrease in the catalytic activity.