Selective reduction of NOx with ammonia over a titania highly dispersed on mordenite Original Research Article

Titania highly dispersed on mordenite, TiO2/MZ, was prepared by hydrolysis of titanium tetraethoxide. The selective reduction of NOx over the catalyst was studied. The titania dispersion significantly enhances the reduction activity at temperature of 200 to 300°C. Little change of the activity occurs at temperature of 400–600°C. FTIR spectra indicate that the titania dispersion increases the amounts of the adsorption species of NO and (NO)2. The adsorbed species of NO disappeared rapidly upon exposure to NH3 + O2 at 300°C, but (NO)2 disappeared slowly. The main path of NO → (NO)ad → N2 hence is proposed as the reduction mechanism of NO over the catalyst. The shifts in the binding energies of Ti2p and O1s for the TiO2/MZ and ESR data indicate that the supported titania interacts with the mordenite. XRD spectra support that the titania is highly dispersed in the mordenite. From the XPS peak intensities, the amount of titania in the outer surface regions is estimated to be only 1.3 mol% of total titania in the TiO2/MZ at the most. These findings support the incorporation of the most of titania into the mordenite cavities. Hence, the incorporation and high dispersion of titania accelerate the reduction.