Ru-Cu/ZSM5 catalysts: Characterization by FT-IR spectroscopy

H-ZSMS supported Ru-Cu bimetallic catalysts have been studied by FT-IR spectroscopy. Experiments have been carried out on samples prepared from Ru(NO)(NO3)(3) and RuCl3. On the monometallic Ru/ZSMS samples adsorption of CO led to a band at 2046 cm(-1), due to CO linearly adsorbed on Ru-0, and several bands at higher frequencies related to CO on RU(delta+) species. A higher amount of Ru-delta+ species is formed on the ex-Ru(NO)(NO3)(3) sample, due to the smaller metal particle size of this sample compared to the ex-RuCl3 one. On monometallic Cu/ZSMS two bands at 2151 and 2158 cm(-1) are observed, both related to CO adsorbed on Cu+1 sites, formed through a reaction with the OH groups of the zeolite. On the bimetallic Ru-Cu samples, besides all the characteristic bands of the Ru and Cu monometallic samples, a band at 2138 cm(-1) attributed to CO adsorbed on Cu bound to Ru has been detected, denoting the formation of Ru-Cu bimetallic particles. The FT-IR spectra indicate that on the samples prepared from RuCl3 the extent of bimetallic Ru-Cu particles is higher than on those prepared from Ru(NO)(NO3)(3). This behaviour, attributed to the presence of chlorine on the ex-RuCl3 samples, is in agreement with the catalytic performance of these systems in the hydrogenolysis of propane.