Catalytic Performance of Silica-Supported Silver Nanoparticles for Liquid-Phase Oxidation of Ethylbenzene

In this study silver nanoparticles were prepared by chemical reduction method using silver nitrate as metal precursor, starch as protecting agent, and sodium borohydride (NaBH4) as a reducing agent. Formation of silver nanoparticles was monitored using UV-vis absorption spectroscopy and dynamic light scattering (DLS). They were supported on silica by dispersing silica powder in the suspension of destabilized silver nanoparticles. Samples containing different proportions of silver were thus prepared. This method is at variance from the conventionally employed method, i.e., impregnation of silver salt from its solution on support. Ag/SiO2 samples were characterized by UV-vis absorption spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), inductive coupled plasma optical emission spectroscopy (ICP-OES), and N-2 adsorption-desorption. Superior catalytic performance of the catalyst prepared by the present method could be observed in a test reaction of ethylbenzene oxidation affording high selectivity to acetophenone as compared to the catalyst prepared by the conventional reported methods. The 5 wt % Ag/SiO2 catalyst was found not much susceptible to sintering as could be inferred from the comparable performance of the regenerated and fresh catalysts.