锶改性对γ-Al_2O_3的高温热稳定作用

High Temperature Thermal Stability of γ-Al_2O_3 Modified by Strontium

研究了Sr(NO3 ) 2 浸渍改性对γ Al2 O3 的高温热稳定作用 ,考察了Sr含量 (SrO/Al2 O3 摩尔比为 0 0 0 5～0 15 )以及热处理温度 (6 0 0～ 115 0℃ )和气氛等影响因素 .BET比表面积和粉末X射线衍射结果表明 ,高温下Sr物种的引入明显地抑制了氧化铝比表面积的损失和α相变 ,而水蒸气的存在则削弱了Sr物种的高温稳定作用 .随着Sr含量的增大 ,Sr物种的高温稳定作用增强 ,但过度提高Sr含量时 (SrO/Al2 O3 比为 0 15 ) ,Sr物种的纯机械混合掺杂的负作用超过其对Al2 O3 的稳定作用 .焙烧温度从 6 0 0℃升至 115 0℃ ,氧化铝与Sr物种固相反应的产物由二铝酸盐转化至六铝酸盐 .高温动力学研究结果表明 ,Sr的高温稳定作用主要是抑制焙烧过程中最初

The effects of strontium content (SrO/Al 2O 3 molar ratio varied from 0 005 to 0 15), calcination temperature (600～1?150 ℃) and calcination atmosphere on the high temperature thermal stability of Sr modified γ Al 2O 3 prepared by impregnation have been systematically investigated by measuring BET specific surface area and powder X ray diffraction. The results show that the addition of strontium species increases the specific surface area of γ Al 2O 3 and inhibits the transformation into α phase. However, the existence of steam during calcination weakens the stabilization of strontium species. The stabilization of strontium species is strengthened with the increase of strontium content and there exists an optimal modification range of 0 01～0 05. But the further increase of strontium content weakens the high temperature stability of alumina. With the rise in calcination temperature from 600 ℃ to 1?150 ℃, the product of solid state reaction between alumina and strontium transforms from dialuminate to hexaaluminate. Furthermore, the study of the kinetics behaviour of alumina at 1?150 ℃ indicates the stabilization of strontium species can be mainly attributed to retarding the loss of specific surface area due to the sintering and α phase transformation within initial 1h during the calcination process.