Infra-red study of ammonia adsorption on rutile surfaces

Abstract

The adsorption and desorption of ammonia on a rutile surface pretreated with oxygen and evacuated at 400°C has been studied by infra-red spectroscopy. Rutile surfaces equilibrated with water vapour at 45°C or reduced in hydrogen at 400°C were also investigated. Two distinct Lewis acid sites are postulated and probably arise from titanium ions on the surface in two different stereochemical environments. No evidence for Brønsted acidity was found even for a surface which had been exposed to an excess of water vapour.