La_2O_3的添加方式对Al_2O_3热稳定性的影响

Effect of La_2O_3-modification methods on alumina thermostability

采用3种不同添加方式制备La2O3改性的Al2O3材料La-Al2O3。La-Al2O3分别经500℃、1 000℃和1 200℃焙烧,采用物理吸附、X射线衍射和荧光光谱等对高温处理的La-Al2O3进行比表面积和结构表征。结果表明,La2O3的添加能有效抑制Al2O3在高温条件下向热力学稳定态α-Al2O3转变,同时提高高温处理后La-Al2O3比表面积,使Al2O3热稳定性得到明显提高。在3种La2O3添加方式中,La(NO3)3浸渍法效果最为显著,制得的La-Al2O3(N)材料经1 200℃焙烧4 h的比表面积为30 m2.g-1,是未经改性的Al2O3样品经同等温度焙烧比表面积的2.2倍。

Al2O3-modified alumina prepared by three different methods and calcined at different tempera- tures （500 ℃, 1 000 ℃ and 1 200 ℃ ）were characterized by physical adsorption, X-ray powder diffraction and fluorescence spectra. The phase analysis results showed that La2O3 could restrain the phase transformation of γ-Al2O3 to α-Al2O3. BET results showed that La203-modified alumina possessed higher specific sur- face area and its thermal stability was obviously increased. The specific surface area of La-Al2O3 （N） pre- pared by La（ NO3 ）3 with impregnation method and calcined at 1 200℃ for 4 h reached 30 m2·g-1 ,which was 2.2 times as large as that of La-free alumina calcined at the same temperature.