Sintering behavior of platinum and modification effect of ceria on silica-alumina supports for diesel soot oxidation

In this work, silica-alumina mixed oxides with different SiO2 contents (5% and 30%) were adopted as acidic supports for platinum catalysts for soot oxidation. The obtained catalysts were thermally aged in air at 550, 650 and 750 degrees C for 2 h, respectively. The catalysts were characterized by transmission electron microscopy (TEM), CO chemisorption, inductively coupled plasma (ICP), N2 adsorption/desorption, NH3 temperature-programmed desorption (TPD), H2 temperature-programmed reduction (TPR), infrared (IR) spectroscopy of CO and NH3 adsorption, and NO temperature-programmed oxidation (TPO). The acidic support Pt catalysts had higher catalytic activities for NO oxidation and soot oxidation. After aging at 750 celcius, severer sintering of Pt occurred on the acidic supports, and some Pt particles larger than 50 nm formed, resulting in serious deactivation. It was ascribed to metallic state of Pt on the acidic supports with weakened metal-support interactions (SMI). Thus, CeO2 was added to the silica-alumina support by ball milling to strengthen the SMI via forming Pt-O-Ce bonds. In this way, Pt nanoparticles were anchored to the modified support to inhibit sintering at high temperatures, and the obtained Pt/CeO2/SiO2-Al2O3 catalyst exhibited both high soot oxidation activity and superior thermal stability.