Preparation of Au catalyst on modified SiO2 via adsorbed-layer nanoreactor technique

Au nanoparticles were supported on modified SiO2 via adsorbed-layer nanoreactor technique. The morphology of the catalysts was analyzed by TEM, and the grain size of Au was determined by X-ray diffraction. Owing to the higher isoelectric point (IEP), the modifying component was significantly helpful for the preparation of much smaller Au nanoparticles on silica. However, the size order of Au was different with the order of IEP of modifying component. The catalysts showed an apparent Au particle size-dependent activity on the oxidation of cyclohexane. The catalyst modified by Ni(OH)2 with the smallest Au particles had the highest catalytic activity, while it had the lowest one when modified by Mg(OH)2 with the biggest Au particles. The selectivity to cyclohexanol and cyclohexanone could maintain at a high value as the conversion increased, which was different from the results of catalysts prepared by other routes.