TRANSMISSION ELECTRON-MICROSCOPY (TEM) STUDY OF POLYCRYSTALLINE RU-AGALUMINA SUPPORTED CATALYST SYSTEM/

Transmission Electron Microscopy (TEM) was used to characterize bimeta llic Ru/Ag Catalyst samples dispersed on a high surface area Alumina s upport. The addition of Ag increases the metal dispersion but no consi stent trend is observed. Ag forms crystallites of various shape and si zes, some of them are present in the close vicinity of Ru but not form ing Ru:Ag bimetallics. A part of Ag crystallites cover the Ru surface hence blocking Ru emission. These irregular shaped crystallites are po ssibly responsible for the increase in metal dispersion. Particles bel ow 2.5 nm were Ag particles, between 2.5 to 5.0 nm were Ru:Ag mixed cr ystallites and above that were Ru particles. The data has been discuss ed in terms of geometric effect caused by the addition of Ag.