ZnAl layered double hydroxide based catalysts (with Cu, Mn, Ti) used as noble metal-free three-way catalysts
Résumé
This research presents a novel approach for developing noble metal-free three-way catalysts by using ZnAl layered double hydroxide (LDH) co-precipitated with Mn and Ti. Cu was added as the catalytically active metal. Two methods were explored, namely the addition of Cu during the co-precipitation step and a post-synthesis method using the LDH memory effect. In case the starting material had LDH characteristics high amounts of CuO were adsorbed on the support and high dispersion degrees of CuO were obtained. A four-cycle three-way catalysis test was used for evaluation. The smaller CuO particle size resulted in better performance for oxidation reactions. The addition of Mn had a positive effect on the general performance of the catalysts, while the presence of Ti mainly improved the NO conversion. The developed materials showed good stability in consecutive catalytic testing cycles and even show some NO conversion under stoichiometric conditions. The developed CuO-based ZnAl layered double hydroxide-based materials are very promising catalysts for Three-way catalysis, allowing to reduce the precious metal content compared to the classical catalysts composition.