Various alumina-based supports were prepared by adding metal elements such as alkaline and rare earths to sol-gel alumina synthesized from aluminium isopropoxide using 2-methyl-pentane-2,4-diol as a solvent and the influence of the additives on the thermostability of the supports was investigated. It was found that Pa and Sr are the most effective in improving the thermostability of the alumina, La is moderately effective while Zr, Mg and Ca are ineffective. The influence of the additives on the catalytic activities of Pt/CeOx/MO(y)-Al2O3 (M = Ba, Sr, La) after the calcination at 1273 K was also investigated. Pt/CeOx/BaO-Al2O3 and Pt/ CeOx/La2O3-Al2O3 showed higher catalytic activity than Pt/CeOx/Al2O3, while Pt/CeOx/SrO-Al2O3 showed lower catalytic activity. The activity order was Ba>La = none>Sr in terms of CO and C2H4 oxidation.