Infrared study on the adsorbed state of ammonia on heteropoly compounds

Abstract

A heteropoly compound is one of the strongly active acid catalysts which can be used for several acid catalyzed reaction. One property of heteropoly compounds as a solid acid catalyst is that there are acid sites on the surface as well as in the bulk. The other property of these catalysts is that nitrogen compounds such as pyridine and ammonia are easily adsorbed as a pseudo-liquid phase in the bulk. Kim et al. reported that there was no correlation between the adsorbed amounts of pyridine and those of ammonia on heteropoly compounds. They suggested that ammonia could be adsorbed on an acid site of a heteropoly compound as well as on a metal cation. The adsorption of ammonia as an amine structure on copper containing heteropoly compound was discussed by Saito et al. However, a systematic study on the adsorbed state of ammonia on the heteropoly compound was not reported. This paper reports an investigation of the infrared spectra of ammonia adsorbed on a heteropoly compound to illustrate the possible states of the adsorbed ammonia.