CATALYTIC WET AIR OXIDATION OF AMMONIA OVER ALUMINA-SUPPORTED METALS

Wet air oxidation (WAO) of ammonia to dinitrogen has been investigated using various heterogeneous catalysts. Among them RuO2/Al2O3 exhibite d remarkable activities that at least 99% of ammonia (1500 ppm) was de composed at 503 K under 1.5 MPa in a NaOH added water (pH of 12). The product was dinitrogen exclusively, and the quantities of NO3- formed were very small. The reaction proceeded rapidly in the high pH region indicating that ammonia was more reactive than ammonium ion. The activ ity and selectivity were found to have a relation with the oxygen affi nity of the metal element. It was discussed that elements (Ru, Pd) wit h medium weakness of M-O bond showed the high activity and selectivity and the reason was proposed. (C) 1998 Elsevier Science B.V.