Hyperbranched polyethyleneimine towards the development of homogeneous and highly porous CuO–CeO2–SiO2 catalytic materials

• Highly porous and thermally stable materials with ssa values up to 680 m2/gr.
• PEI provides excellent dispersion of CeO2/CuO phases and formation of a 3D network.
• Catalytic materials are tested under harsh and realistic exhaust environment.
• Very high oxidation and efficient NO removal under fuel rich conditions.
• The developed nanoporous materials can be incorporated into current TWCs.

A novel templating strategy for the development of composite nanoporous CuO/CeO2/SiO2 materials with advanced properties and significant thermal stability is proposed in this work, for potential use in automotive catalysts. The synthetic process is based on the dual role of low cost hyperbranched polyethyleneimine (PEI) acting both as a reactive template to control the formation of a siliceous porous network and as a metal chelating agent to facilitate the incorporation of finely dispersed CuO/CeO2 nanoparticles into the silica matrix. Direct Ce(III)/Cu(II) introduction into the reaction mixture or post-synthetic impregnation of a preformed hybrid organic/inorganic xerogel was employed. Materials properties were assessed by means of XRD, SEM, TEM, N2 adsorption, TPR and XPS techniques. Final Cu loading was determined by a novel UV–Vis spectroscopic method. Activity tests were performed under stoichiometric, O2-deficient and O2-rich conditions simulating realistic exhaust environment. Catalytic performance was found to be strongly depended on the employed synthetic pathway. The CuO/CeO2/SiO2 composites prepared by direct introduction, exhibited enhanced structural characteristics (BET ≈ 680 m2/g), high homogeneity, superior oxidation performance and notable thermal stability, with great potential for use in automotive aftertreatment systems.

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