On the chemistry of ammonia over oxide catalysts: Fourier transform infrared study of ammonia, hydrazine and hydroxylamine adsorption over iron-titania catalyst

The adsorption and transformation of ammonia over Fe2O3/TiO2 catalyst has b een investigated by FT-IR spectroscopy in vacuum at increasing temperature. Ammonia is first coordinated over Lewis sites and later undergoes hydrogen abstraction giving rise either to NH2 amide species or, to its dimeric for m N2H4, hydrazine. Other species tentatively identified as imide NH and nit roxyl HNO are produced further. The comparison of the infrared spectra of t he species arising from NH3 and N2H4 and NH2OH adsorbed over Fe2O3/TiO2 str ongly suggests that N2H4 is an intermediate in NH3 oxidation to N-2 over th is catalyst. So ammonia is activated in the form of NH2 species for both SC R and SCO. Ammonium ion is detected only in traces at r.t. It seems consequ ently demonstrated that Bronsted acidity is not necessary for the appearanc e of SCR and SCO activity.