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

Authors:

• Izabela Sobczak,
• Maria Ziółek,
• Monika Nowacka

Abstract

Pt and Nb-containing MCM-41 molecular sieves addressed to NO reduction by hydrocarbons were prepared via impregnation of NbMCM-41 with Pt(NH ₃)₄(NO₃)₂ or H₂PtCl ₆ (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. © 2004 Elsevier Inc. All rights reserved.