Characterization of Ag/Al2O3 de-NOx catalysts by probing surface acidity and basicity of the supporting substrate

被引:32
作者
Wang, ZM [1 ]
Yamaguchi, M [1 ]
Goto, I [1 ]
Kumagai, M [1 ]
机构
[1] Inst Res & Innovat, Div Chem Res, Kashiwa, Chiba 2770861, Japan
关键词
D O I
10.1039/b000226g
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
Ag/Al2O3 catalysts with various Ag contents were characterized by thermal gravimetry (TG), differential thermal analysis (DTA), temperature-programmed desorption (TPD), NH3 and CO2 adsorption calorimetry, FT-IR spectroscopic method, and diffuse reflectance spectra (DRS). It was found that hydroxy groups on alumina have a close relationship with Ag loading either through ion-exchange with the proton of an acidic -OH or bonding with oxygen of a basic -OH species. An Ag loading of less than 240 mu mol g(-1) decreases the Lewis acid sites but increases the Bronsted acid sites with medium NH3 adsorption energy. A greater Ag loading induces interaction between NH3 molecules and Ag oxides, leading to reduction of Ag oxides and dissociation of adsorbed NH3. A large amount of Ag loading produces greatly enhanced basicity. The changes in the loaded form of silver on alumina are discussed. The appropriate acid-base property plays an important role in de-NOx activity using propane as the reductant.
引用
收藏
页码:3007 / 3015
页数:9
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