Application of silica-alumina as hydrothermally stable supports for Pt catalysts for acid-assisted soot oxidation

In this work, silica-alumina mixed oxides with different SiO 2 contents (5% and 30%) were adopted as acidic supports for platinum catalysts for soot oxidation. The obtained catalysts were hydrothermally aged in 10% H 2 O/air at 750 °C for 20 h. The catalysts were characterized by X-ray diffraction (XRD), N 2 adsorption, inductively coupled plasma (ICP), CO chemisorption, NH 3 temperature-programmed desorption (TPD), infrared (IR) spectroscopy of CO adsorption, temperature-programmed oxidation (TPO) of NO, and TPD of NO x . The surface acidity of catalyst was positive correlated with the content of SiO 2 , which kept platinum in metallic and partially oxidized states in an oxidizing atmosphere. Compared with sulfation treatment on the alumina support, the application of SiO 2 –Al 2 O 3 mixed oxides does not result in the coverage of Pt active sites and the prepared catalysts exhibit excellent activity for NO oxidation. They promote NO x preferential adsorption on soot and decomposition of surface oxygenated compounds (SOCs) as the sulfated Pt/Al 2 O 3 catalyst does. Graphical abstract