Effect of rare earth on the thermostability and the surface area of auto-catalyst washcoats

In this paper, the influence of rare earth on the thermostability and surface area of auto-catalyst washcoating was studied by XRD and BET analysis. The results showed that the modification of rare earth was positively effective for the thermostability of gamma-alumina washcoating. With rare earth, the transformation temperature from gamma-alumina to alpha-alumina was increased from 800 degrees C to 1200 degrees C. Rare earth oxides could improve the thermostability of gamma-alumina washcoating better than rare earth nitrates. At the same time, the thermostability was also dependent on the loading amount of rare earth. To make the best thermostability of auto-catalyst washcoating, the additive content into gamma-alumina was about CeO2 6%wt, La2O3 8%wt. According to BET measurement, the biggest surface area of gamma-alumina washcoating could be reached under the condition of CeO2 10%wt, La2O3 2%wt. To modify auto-catalyst washcoating, the thermostability and surface area should be considered synthetically by adding the most appropriate amount of rare earth. (C) 2000 Elsevier Science S.A. All rights reserved.