Solvent-free selective oxidation of aromatic alcohol with O2 over MgAl-LDH supported Pd nanoparticles: Effects of preparation methods and solvents

In this work, layered double hydroxide (LDH) supported Pd samples were prepared by sol-immobilization and impregnation methods in the different solvents. As confirmed by XRD, N-2 adsorption, TEM results and catalytic reaction, the methods and solvents used in the preparing process greatly influenced the dispersions of the supported Pd NPs on LDH support and the textural structures as well as the catalytic performances of the prepared Pd/LDH samples. The samples prepared with ethanol as the colloidal or impregnation solvent (Sol-Pd/ LDH-Et or IM-Pd/LDH-Et) had higher Pd dispersions and surface areas than the corresponding samples prepared with water as the colloidal or impregnation solvent (Sol-Pd/LDH-Aq or IM-Pd/LDH-Aq). These differences were ascribed to different interaction of solvent with stabilizer PVP and LDH support. Sol-Pd/LDH-Et exhibited a better catalytic activity and selectivity in solvent-free oxidation of benzyl alcohol with O-2 than Sol-Pd/LDH-Aq and the samples prepared by impregnation. This work provides an alternative and efficient route to improve the catalytic performances of the LDH supported catalysts via adjusting the solvents and methods of supporting metal NPs.