Abstract
Samples of Pt/CeO2, Pt/Al2O3 and Ce/Pt/Al2O3 (Pt/Al2O3 promoting by CeO2) were prepared by incipient wetness impregnation method. The prepared samples are used to investigate the decay phenomena of Pt/Al2O3 upon calcination at high temperatures and the promoting effect of CeO2 on Pt/Al2O3.From experimental results, we found three phenomena occurred in Pt/Al2O3 at high temperatures. (1)From XRD and TEM, we found the particle size of active metal will increase due to sinter. (2)From AA, we found Pt will loss by sublimation in the form of PtO2 (g) and the amount of loss increase with TC. (3) From TPR, when TC ? 700oC Pt will interact with Al2O3 to form PtAl2O4 which is difficultly reduced (Tr = 650 oC~750 oC). Those stated above should be the reasons of activity decay in Pt/Al2O3 at elevated temperature.However, when we mixed Pt/Al2O3 with CeO2, we found it will inhibit the sinter and loss of active metal at elevated temperature. In addition, from TPR we found Pt will interact with CeO2 to form PtCeOx (Tr = 225 ℃) in mixed samples calcinated at high temperatures. This specie is more easily reduced than PtAl2O4, so it will be more easily regenerated to Pt by hydrocarbons. Therefore, Ce/Pt/Al2O3 would have better redox activity than Pt/Al2O3.