LOW-TEMPERATURE INFRARED STUDY OF CARBON-MONOXIDE ADSORPTION ON SULFATED TITANIA

Acidic properties of a TiO2 sample containing approximately 1 wt% S were examined by low-temperature IR spectroscopy of CO and by coadsorption of CO and NH3. Due to the almost negligible OH content of the sample, Bronsted acidity could not be detected. However, Lewis acid sites with enhanced acid strengths as compared to sulfate-free titania could clearly be detected. It is inferred that these sites (namely cus Ti4+ sites) are located in close proximity to sulfate groups and that CO (and NH3) coordinated to the Ti4+ sites interact with the sulfate groups presumably via electronic inductive effects.