摘要
对镧氢稳Ｙ沸石（ＬａＨＯＳＹ）体系在水热处理条件下，Ｌａ的交换度对表面酸性的影响进行了研究，并与典型的正己烷裂化反应活动相关联。结果表明，无Ｌａ的ＵＳＹ沸石经水热处理后，酸性和裂化活动显著下降；而ＬａＨＵＳＹ沸石的酸性和裂化活动性，先是随着Ｌａ含量的增加而增加，然后通过一个极大值又开始下降。Ｌａ能抑制ＵＳＹ沸石在水热条件下产生的骨架脱铝和结构崩塌。沸石β笼内的多价阳离子Ｌａ￣（３＋）与水分子反应生成镧氢氧化钠以及Ｌａ￣（３＋）的极化作用能夺取骨架羟基的电子而产生强的Ｂｒｏｎｓｔｅｄ酸。过量的Ｌａ￣（３＋）增强的正电场使晶胞中酸质子数目减少，当Ｌａ含量大约为骨架铝含量的１６％（原子比）时，沸石的强酸性和裂化活性出现极大值。
A series of lanthanum-exchanged ultra-stable Y zeolites (LaHUSY)was prepared.The effect of La-ion exchange on the surface acidity,hydrothermal stability and cracking activity of LaHUSY zeolite sytem was studied. The results showed that the acidity and hexane cracking activity first increased with increase of lanthanum loading and then went through a maximum. The content of La￣(3+) play an important role in inhibiting structure collapse and aluminum removal. The presence of polyvalent La cations in theβcages in the form of the lanthanum hydroxide species is responsible for the formation of strong acidity. These cations interact with the framework via a polarizing effect. withdrawing electrons from the O-H bonds. After excess La ions exchange,the positive potential field enhanced by La￣(3+)ions could cause fewer protons,remaining in the unit call and then the acidity decreased.For dll of the LaHUSY after hydrothermal treatment the maximum acidity and activity occurred when the atomic ratio of La￣(3+) was about 16%of the framework Al content.
出处
《石油大学学报（自然科学版）》
CSCD
1994年第3期90-95,共6页
Journal of the University of Petroleum,China(Edition of Natural Science)
关键词
催化剂
稳定性
酸性
催化裂化
Cracking catalysts
Zeolites
Lanthanum
Hydrothermal stability
Acidity cations
