RuCuZSM5 catalysts: characterization by FT-IR spectroscopy

H-ZSM5 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 RuZSM5 samples adsorption of CO led to a band at 2046 cm−1, due to CO linearly adsorbed on Ru0, and several bands at higher frequencies related to CO on Ruδ+ species. A higher amount of Ruδ+ 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 CuZSM5 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.