Identifying the nature of the copper entities over ceria-based supports to promote diesel soot combustion: Synergistic effects

Abstract

The aim of this research is to prepare catalysts exhibiting a wide range of copper incorporation/distribution/contact degrees on ceria-zirconia mixed oxide by preparing catalysts with a high degree of copper incorporation, well-dispersed copper on the surface/porosity and different degrees of physical interaction. Their catalytic activities towards diesel soot combustion and NO oxidation to NO2 were analyzed with the purpose to identify the nature of the copper entities over ceria-based supports to promote diesel soot combustion. The catalysts were characterized by N2 adsorption-desorption isotherms at −196°C, XRD, Raman spectroscopy, XPS, H2-TPR and reducibility tests under inert atmosphere. Activity tests were performed towards NO oxidation to NO2 (from 25°C to 700°C) and diesel soot combustion in NOx/O2 atmosphere, under ramp mode (from 25°C to 700°C) and isothermal conditions (450°C). Results reveal that copper in close contact with ceria greatly promotes its reducibility under H2 and He at low temperatures, as well as catalytic NO oxidation to NO2. Mainly, 2%Cu/ceria-zirconia catalyst prepared by incipient wetness impregnation shows the highest activity towards soot combustion at low temperatures (≤450°C), due to the observed synergistic copper-ceria interactions.