Alumina prepared by peptizing method with a high specific surface area, moderate pore structure and pore size distribution was studied. Furthermore, the effects of additives La and PEG on thermal stability, particle size, structure and texture of alumina were investigated. The results of characterization of BET and XRD show that the addition of La greatly inhibits the loss of specific surface area and α phase transformation of alumina under the hydrothermal and high temperature conditions. At the same time, PEG as an additive can apparently increase pore volume and pore diameter of alumina. The more the La and PEG content is, the larger the surface area, pore volume and average diameter of alumina are. However, when the quantity ratio of La2O3 to Al2O3 or PEG to Al2O3 is excessive, the negative action of La and PEG are stronger. When the quantity ratio of La2O3/Al2O3 is 2.5%—3.0%, thermal stability of γ-Al2O3 is the best and specific surface area of alumina is more than 140 m2/g after hydro thermally being aged at 1000 ℃ for 5 h. Though PEG plays a good role on making pore and aggregation when the value of quantity ratio of PEG/Al2O3 is 80%, the thermal stability of alumina is worse and specific surface area is only 136.4 m2/g, pore volume is 0.41 mL/g and pore diameter is 9.38 nm under the same aging condition. Fortunately, after hydro thermally being aged at 1000 ℃ for 5 h, the alumina containing 2.5%La2O3 and 80%PEG of quantity of alumina has the best thermal stabilization and the largest specific surface area, pore volume and pore diameter that are 156.2 m2/g, 0.57 mL/g and 11 nm, respectively.
The effect of preparation method on the properties of alumina modified by La2O3 and BaO was investigated by means of Low temperature nitrogen adsorption-desorption, NH3-TPD, NO-TPD and XRD. The results show that alumina prepared by peptizing method exhibits the best textural properties, alumina obtained by co-precipitation method presents the strongest surface acidity and alumina derived from impregnation method shows the best ability of NO adsorption. After calcination at 1 100 ℃, all alumina except that from impregnation method have excellent thermal stability. When the specific surface area and pore volume of alumina are large enough, the activity of catalyst Pd/alumina is affected primarily by the surface acidity of alumina.
