Infrared spectroscopic study of isocyanate formation in the reaction of NO and CO over Cr2O3/Al2O3 and Cr2O3/SiO2

Abstract

The formation of an isocyanate complex in the NO + CO reaction on alumina- and silica-supported chromia was investigated by infrared spectroscopy. Isotopically-labelled gases were used to confirm that the bands at 2262 and 2242 cm^–1 on Cr₂O₃/Al₂O₃ are due to surface isocyanate. The effects of the experimental conditions on the intensities of the above bands were investigated in detail. Isocyanate on Cr₂O₃/SiO₂ yielded bands at 2315 and 2210 cm^–1. The band at 2210 cm^–1 was assigned to Cr²⁺–NCO, while the bands at 2262 and 2242 cm^–1 and that at 2315 cm^–1 were attributed to the isocyanate complex residing on alumina and silica, respectively.