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Unité de Formation et de Recherche de Chimie

Soutenance de la Thèse de Zhao Wang le 26 juin 2017

Thèse soutenue le 26-06-2017

Sous la direction de Catherine Louis.

à l' Université Pierre et Marie Curie , dans le cadre de École doctorale Physique et chimie des matériaux (Paris) , en partenariat avec Laboratoire de Réactivité de Surface / LRS (laboratoire) .

This work investigates the preparation and characterization of titania-supported non-noble bimetallic Cu-Zn, Ni-Zn and Fe-Zn catalysts with various atomic ratios and their catalytic properties for the selective hydrogenation of polyunsaturated hydrocarbons. Co-deposition-precipitation with urea (DPu) and co-deposition-precipitation at fixed pH (DP8) methods were employed for the samples preparation. The metal ions were sequentially deposited onto the TiO2 surface (the sequence of pH for ions deposition being CuII < ZnII ≈FeII < NiII) during the DPu, while they were simultaneously deposited using DP8 method. After sample reduction at proper temperature (350 °C for Cu-Zn, 450 °C for Ni-Zn and 500 °C for Fe-Zn), XRD and STEM-HAADF coupled with EDS showed that bimetallic nanoparticles were formed in Cu-Zn/TiO2 (Cu3Zn1 or Cu0.9Zn0.1 alloy) and Ni-Zn systems (Ni1Zn1 or Ni4Zn1 alloy) with average particle size smaller than 5 nm. Only metallic Fe was detected by XRD in Fe-Zn/TiO2. Zn is inactive for butadiene selective hydrogenation, and acts as a modifier of the monometallic catalysts whose activity follows the sequence: Cu < Fe < Ni. The addition of Zn slightly decreases the activity and influences the selectivity to butenes, but provides much more stable catalysts. The higher stability of the bimetallic catalysts was ascribed to the formation of lower amount of carbonaceous species during the reaction, resulting from the change in the size of the active metal surface ensembles by alloying with Zn.


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