Selective wet-air oxidation of diluted aqueous ammonia solutions over supported Ni catalysts

Wet-air oxidation (WAO) of diluted aqueous ammonia solutions over Ni supported on Al2O3 catalysts was investigated. A nitrogen selectivity of 90% was achieved by the WAO of ammonia over the 20-wt% Ni/Al2O3 catalyst at 503 K, a reaction time of 2 h and air-feed pressure of 2.0 MPa without the dissolution of Ni during the reaction. Ni/Al2O3 pretreated by calcinations in air at 1173 K for 4 h showed high stability due to the formation of a NiAl2O4 phase.