Ammonia adsorption on Keggin-type heteropolyacid catalysts explored by density functional quantum chemistry calculations

被引：23

作者：

Bardin, BB ^{[1
]}

Davis, RJ ^{[1
]}

Neurock, M ^{[1
]}

机构：

[1] Univ Virginia, Dept Chem Engn, Charlottesville, VA 22903 USA

来源：

JOURNAL OF PHYSICAL CHEMISTRY B | 2000年 / 104卷 / 15期

关键词：

D O I：

10.1021/jp993227t

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：

Density functional quantum chemical calculations have been used to compare the acid strengths of phosphotungstic and phosphomolybdic acids by computing the adsorption energy of ammonia on model clusters of each heteropolyacid. The adsorption of ammonia on a phosphotungstic acid cluster was stronger than the adsorption on a phosphomolybdic acid cluster. The predicted adsorption energies were near -150 and -106 kJ mol(-1) for phosphotungstic and phosphomolybdic acid, respectively. This compares well with the experimental heats of ammonia sorption determined from microcalorimetry. An analysis of different adsorption modes of ammonia on phosphotungstic acid showed that bidentate adsorption of ammonia on the heteropolyacid clusters aided in proton transfer and yielded stronger adsorption energies than did a monodentate adsorption mode. In addition, we report the computed adsorption energies of pyridine on a heteropolyacid cluster.

引用

页码：3556 / 3562

页数：7

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