Products distribution during the gas phase photocatalytic oxidation of ammonia over the various titania based photocatalysts

The adsorption and photooxidation of gaseous ammonia have been investigated by the FTIR spectroscopy method in a static reactor using TiO(2) and modified TiO(2) as photocatalysts. Two types of modified TiO(2) were tested: TiO(2) impregnated with transition metal oxides (NiO, V(2)O(5), MoO(3), and Fe(2)O(3)) and TiO(2) doped with noble metals like Ag, Au, Pt, Pd by the chemical and photochemical deposition methods. Molecular nitrogen, NO(3)(-), N(2)O and water were found as the major final products of ammonia photocatalytic oxidation (PCO). One of the purposes of the current study was to minimize the N(2)O formation during PCO. The pure unmodified TiO(2) (anatase, S(BET) similar to 350 m(2)/g) turned out to be the best photocatalyst for this purpose giving only 7% of initial NH(3) quantity converted into N(2)O. Long-term experiments were carried out to determine the photocatalysts stability in PCO of NH(3). All the catalysts exhibited stable performance: the rate of deactivation was low due to the transformation of NH(3) nitrogen mainly into N(2). Only approximate to 30% of initial NH(3) quantity was oxidized into HNO(3) which was adsorbed on the catalysts surface in all cases. (C) 2009 Elsevier B.V. All rights reserved.