POSSIBLE ROLE OF ISOCYANATE SPECIES IN NOX REDUCTION BY HYDROCARBONS OVER COPPER-CONTAINING CATALYSTS

The behavior of an isocyanate intermediate (-NCO) formed during NO(x) reduction has been studied on alumina-supported Cu-Cs oxide catalyst i n the presence of oxygen and hydrocarbons (propene, acetylene, propane and n-heptane) using infrared spectroscopy. While a reaction involvin g NO, O2 and acetylene needs some heat treatment to produce the isocya nate species on the catalyst, no heat treatment is required in the NO/ O2/propene or n-heptane system. No isocyanate intermediate is formed i n a NO/O2/propane system by an ordinary procedure. Adsorbed water on t he catalyst surface is found to suppress the formation of the isocyana te species. This inhibition effect is smaller in the acetylene or n-he ptane containing system than in the propene containing system. The rol e of isocyanate species is discussed with reference to results for the practical reduction of NO(x).