担载型铱催化剂上CO吸附量热和红外光谱研究  

Microcalorimetric and FT-IR Studies of CO Adsorption on Supported Iridium Catalysts

作　　者：王兴棠[1,2] 李林[1] 黄延强[1] 王晓东[1] 张涛[1] 

机构地区：[1]中国科学院大连化学物理研究所,辽宁大连116023 [2]中国科学院研究生院,北京100049

出　　处：《催化学报》2008年第12期1231-1236,共6页

基　　金：国家杰出青年基金(20325620);国家自然科学基金(20773122,20803079)

摘　　要：分别对Al2O3和SiO2担载的不同含量铱(Ir)催化剂进行了H2程序升温还原、CO微量吸附量热和红外研究.结果表明,还原后,Ir/Al2O3上存在金属态Ir0和氧化态Irδ+两种物种,CO在催化剂表面主要以线式和孪生吸附态存在,测量的CO吸附热为两种吸附形式的平均吸附热.提高还原温度和Ir担载量,Ir/Al2O3表面CO线式吸附物种的比例增加,从而导致CO吸附热值的升高.而在Ir/SiO2上Ir物种主要为金属态Ir0,CO吸附都以线式吸附为主,在所考察的条件下CO吸附热随Ir担载量和还原温度的变化不明显。Ir/Al2O3 and Ir/SiO2 with Ir loadings of 2 %, 10 %, and 20% were investigated by H2 temperature-programmed reduction, microcalorimetry, and FT-IR. For Ir/Al2O3, there existed both Ir^0 and Ir^δ＋ species. A major carbonyl band, varied with the average particle size, was due to CO linearly adsorbed on Ir^0, while an intense pair of bands observed at 2 080 and 2 004 cm^-1 was assigned to gem-dicarbonyl species adsorbed on Ir^δ＋ . The adsorption heat could be the average heat produced by the formation of both gem-dicarbonyl and linear species. The relative intensities of the Ir^0-CO species were enhanced as the Ir loading and the reduction temperature increased, which led to an increase in the adsorption heat. For Ir/SiO2, several bands ranged in 2 100 - 2 000 cm^-1 were identified and attributed to the linearly bonded CO to larger and smaller Ir^0 clusters. As a result, the adsorption heat maintained almost constant though the loading and the reduction temperature increased.

关 键 词：程序升温还原 吸附量热 红外光谱 铱 氧化铝 氧化硅 

分 类 号：O643.36[理学—物理化学]