Investigation of co-hosted basic and metal nanoparticles in Pt/Cs-BEA zeolites

Various acido-basic BEA zeolites having different Cs contents and containing supported Pt particles were prepared using two acidic parent BEA supports with same framework Al content but with strongly different morphology of the zeolite crystallites. In spite of highly different exchange capacities in aqueous solution, the two parent BEA supports behaved similarly towards formation of Cs-oxide like nanospecies. Thus, the addition of a similar amount of Cs was necessary in the two samples to extinguish all Brønsted acidic sites and a further introduction of Cs led to the presence of highly dispersed Cs2O like species with strong basic character as shown by the adsorption of CO2 followed at 293 K by FT-IR spectroscopy. FT-IR experiments were also conducted at 100 K and 293 K using CO as probe molecule to give further insights on the Cs and reduced Pt species, respectively. In the presence of co-hosted Cs-oxide like, highly dispersed Pt0 nanoparticles are formed with sizes close to 1 nm as observed by TEM. Both the high dispersion of the Pt0 nanoparticles in the more basic samples and the phenomenon of electro-donation by the basic support contribute to the changes in electronic behaviour of the Pt0 particles shown by FT-IR of adsorbed CO.