Preparation and characterisation of Pt containing NbMCM-41 mesoporous molecular sieves addressed to catalytic NO reduction by hydrocarbons

Pt and Nb-containing MCM-41 molecular sieves addressed to NO reduction by hydrocarbons were prepared via impregnation of NbMCM-41 with Pt(NH3)4(NO3)2 or H2PtCl6 (1 wt.% of Pt). The physicochemical properties of prepared Pt/NbMCM-41 materials were investigated by XRD, N2 adsorption/desorption isotherms, TEM, H2-TPR and FTIR combined with NO and C3H6 coadsorption and were compared with those of Pt/Nb2O5, Pt/SiMCM-41 and Pt/SiO2 samples. From the results, the presence of niobium in the mesoporous matrix (NbMCM-41) affects the properties of platinum species formed. Smaller particle sizes of Pt-clusters after reduction and reducibility of Pt species at lower temperature is obtained on NbMCM-41 in comparison with the other supports applied in this work. Furthermore, the nature of the Pt-source (cationic complex or acid used for the impregnation) influences the morphology of the final material as well as catalytic activity of the Pt species. Pt/NbMCM-41 would be an attractive material for SCR with propene (NSR technology), in which Pt cationic species have been reduced during the reaction simultaneously with NO oxidation to NO2. NbO− species present in NbMCM-41 enhances the oxidative activity in the NO → NO2 step and plays the role of storage for nitrate/nitrite species, whereas metallic platinum species is responsible for hydrocarbon activation.