Preparation of Pd (0) and Pd (II) nanotubes and nanoparticles on modified bentonite and their catalytic activity in oxidation of ethyl benzene to acetophenone

The synthesis and application of palladium nanotubes and nanoparticles on modified bentonite was studied. In the first step, an organo-bentonite was prepared by the exchange of the exchangeable Na(+) cations of a homoionic Na-bentonite by cetyl pyridinium cations (CP-bentonite), especially in the range of low coverage ratios where surfactant ions are adsorbed through cation exchange with the counter ions of bentonite. At this stage, there will be a disordered liquid-like monolayer arrangement of alkyl chain within the gallery. This modified bentonite was loaded with the first generation of amidoamine hyperbranch cascade, 3,3'-(dodecylazanediyl) bis(N-(2-(2-aminoethylamino)ethyl)propanamide) (DAEP), which has a long aliphatic tail (C(12)) and a hydrophilic head. The solid/liquid interfacial layer of this architecturally designed bentonite (DAEP-bentonite) was utilized as a nanoreactor for the synthesis of nanoparticles of Pd(2+) and Pd(0). The structure, specific surface area, and porosity of bentonite are significantly altered by the incorporation of nanoparticles. These alterations were monitored by several techniques such as N(2) adsorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and electrochemical impedance spectroscopy (EIS). The size of the palladium nanoparticles prepared in this work was in the range of 5-15 nm. Solvent free oxidation of ethyl benzene using tert-butyl hydroperoxide as an oxidant showed that the palladium nanocatalysts prepared in this work, were highly active and selective. (C) 2010 Elsevier B.V. All rights reserved.