摘要
以拟薄水铝石为前驱物 ,采用溶胶法制备了γ Al2 O3 ,在制备初期添加硝酸镧或硝酸铈对氧化铝进行改性 ,并使用红外光谱、氮物理吸附和X射线衍射等方法对样品进行了表征 .实验表明 ,稀土添加物覆盖了部分氧化铝的表面羟基 .在 10 0 0℃下对样品烧结行为的考察发现 ,添加镧或铈化合物都能提高γ Al2 O3 的抗烧结性能和高温稳定性 ,镧改性样品的效果略优于铈改性样品 .烧结动力学研究发现 ,制备的氧化铝的烧结机理为体相扩散 ,加入稀土有效地阻止了氧化铝颗粒内的体相扩散 .用微反装置测定了改性样品的反应性能 ,发现铈改性样品有一定的裂化性能和脱氢性能 ,而镧改性样品几乎无催化活性 .
The effect of rare earth oxides (La and Ce) on the properties of high surface area alumina prepared from pseudo-boehmite by the sol method was studied. The hydrothermal stability of alumina was investigated by IR spectroscopy, X-ray diffraction, and BET surface area measurement. The reactivity experiments of alumina for the cracking of n-cetane and dehydrogenation of cyclohexane were conducted in a standard fixed-bed reactor system. The results show that the additives influence the properties of alumina, such as surface area, pore volume, pore diameter, amount of hydroxyl group, and cracking and dehydrogenation activity. The La and Ce species decrease the amount of surface hydroxyl group of alumina and obviously prevent the sintering and α-phase formation at 1*!000 ℃. At high temperature Ce 3+ is oxidized to Ce 4+ and segregates as CeO 2. The sintering kinetic studies show that gamma alumina sinters via bulk diffusion. Ce-modified alumina shows higher cracking activity and dehydrogenation activity than La-modified alumina.
出处
《催化学报》
SCIE
CAS
CSCD
北大核心
2003年第8期574-578,共5页
关键词
氧化铝
改性
稀土
镧
铈
热稳定性
十六烷
催化裂化
环己烷
脱氢
alumina, modification, rare earth, lanthanum, cerium, thermal stability, cetane, catalytic cracking, cyclohexane, dehydrogenation
