Theoretical study of the enhanced Bronsted acidity of Zn2+-exchanged zeolites

被引：27

作者：

Barbosa, LAMM ^{[1
]}

van Santen, RA ^{[1
]}

机构：

[1] Eindhoven Univ Technol, Schuit Inst Catalysis, Inorgan Chem & Catalysis Lab, NL-5600 MB Eindhoven, Netherlands

来源：

CATALYSIS LETTERS | 1999年 / 63卷 / 1-2期

关键词：

ab initio; Zn2+; ZnOH+; zeolites; Bronsted site and Lewis site acidity;

D O I：

10.1023/A:1019004702119

中图分类号：

O64 [物理化学（理论化学）、化学物理学];

学科分类号：

070304 ; 081704 ;

摘要：

The effect of Zn2+ exchange on the Bronsted acidity of a protonic zeolite has been studied by the ab initio DFT (density functional theory) approach using the BLYP generalized gradient approximation. Three different zeolite cluster models have been compared: two 6"T" models (two 4"T" rings with an oxygen atom bridge) with Si/Al=1 and Si/Al=2 and a 4"T" model (ring form) with Si/Al=1. The Bronsted acidity has been probed by computation of the acetonitrile adsorption and the cluster deprotonation energy. The presence of Zn2+ does not affect the cluster Bronsted acidity but it creates a very strong Lewis site (Zn2+) in all models studied. On the other hand, the presence of ZnOH+ enhanced the Bronsted site acidity in the case of the 6T model with Si/Al=1. This enhancement is due to a change in cluster geometry and position of OH group in ZnOH+ upon acetonitrile adsorption.

引用

页码：97 / 106

页数：10

共 57 条

[51] Effect of extra-lattice aluminium species on the activity, selectivity and stability of acid zeolites in the liquid phase isomerisation of alpha-pinene [J].