Recherche d'une optimisation de l'oxydation des suies et des gaz dans l'utilisation massive de biocarburants : Nouvelles formulations catalytiques.

Abstract

This thesis focuses on the impact of the presenceof gold nanoparticles supported on CeZrO2 for the treatment of diesel and biodiesel exhaust. Two synthesis methods are tested for gold deposition: deposition-precipitation (DP) and chemical reduction (RC) The synthesized catalysts CeZrO2, Au/CeZrO2-DP and Au/CeZrO2-RC are tested for the oxidation of gases (CO, NO, C3H6, CH3CHO), taken separately or in a mixture, and for the oxidation of soot, under different oxidizing atmospheres (O2, NO+O2, NO2+NO+O2). The effect of contamination of catalysts by inorganic elements (Na and P) is also discussed The characterization results confirm the formation of gold nanoparticles. The XPS deconvolution of spectra indicates the formation of Au0 and Au3+ species on the surface of Au/CeZrO2-DP, while gold is only in metallic form (Au0) on the surface of Au/CeZrO2-RC The latter is globally more homogeneous compared to Au/CeZrO2-DP, the particles are smaller in size and better dispersed on the surface of the CeZrO2 support Gas oxidation is easier in the presence of gold. CO and CH3CHO are better oxidized on the Au/CeZrO2-DP catalyst. For the other gases and gas mixtures, the Au/CeZrO2-RC is more interesting and has a better reaction stability. In terms of soot oxidation, good results are obtained. The Au/CeZrO2-DP catalyst improves the performance of CeZrO2 support not only in terms of activity but also in terms of CO2 selectivity, which is an important parameter in the oxidation of exhaust gases. However, from the stability point of view, the catalyst Au/CeZrO2 RC is better. The latter is also more efficient in the presence of phosphorus at low temperatures and the presence of sodium is even beneficial for this catalyst .