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 surfa ce area of auto-catalyst washcoating was studied by XRD and BET analysis. T he results showed that the modification of rare earth was positively effect ive for the thermostability of gamma-alumina washcoating. With rare earth, the transformation temperature from gamma-alumina to alpha-alumina was incr eased from 800 degrees C to 1200 degrees C. Rare earth oxides could improve the thermostability of gamma-alumina washcoating better than rare earth ni trates. At the same time, the thermostability was also dependent on the loa ding amount of rare earth. To make the best thermostability of auto-catalys t washcoating, the additive content into gamma-alumina was about CeO2 6%wt, La2O3 8%wt. According to BET measurement, the biggest surface area of gamm a-alumina washcoating could be reached under the condition of CeO2 10%wt, L a2O3 2%wt. To modify auto-catalyst washcoating, the thermostability and sur face area should be considered synthetically by adding the most appropriate amount of rare earth. (C) 2000 Elsevier Science S.A. All rights reserved.