Infrared study of NH3/CO reactions on Fe/Al2O3 and promoted Fe/SiO2 catalysts

Abstract

Infrared spectra are reported of Fe/Al₂O₃, Fe/SiO₂ and K₂O, Al₂O₃ and doubly promoted Fe/SiO₂ after treatment at 298–723 K in a gaseous mixture of carbon monoxide and ammonia. Product species included isocyanate groups on iron, surface cyano complexes on iron and isocyanate groups either on the oxide supports or involved in interaction with aluminium ions in promoted iron. The formation of FeNCO was enhanced by both promoters separately and was doubly enhanced when both promoters were present simultaneously. The formation of AlNCO(ads) for Fe/SiO₂ promoted by Al₂O₃ provides evidence for the existence of aluminium ions in the promoted iron surface. Migration of NCO from sites on iron to the oxide support was more facile for alumina support than for silica.