The effect of nickel (Ni) load (0, 5 and 10 wt.%) and support material (Ce0.9La0.1O2, Ce0.9Zr0.1O2 and gamma-Al2O3), together the amount of oxygen (lambda = 0.25 and lambda = 0.5) and gas hourly space velocity (50 000, 100 000 and 150 000 h(-1)) were investigated for the selective catalytic oxidation of ammonia in gasified biomass. The mixed metal oxide support materials were prepared by microemulsion, whereas the alumina was a commercial product. Ni was added to the different supports by incipient wetness. All the obtained catalysts were characterised by BET and XRD analysis. Cordierite monoliths coated with 20 wt.% catalytic material were tested in a tubular quartz reactor. For simulating the gasified biomass fuel, 500 ppm of NH3 was added to the fuel. Water was also present during the activity tests, which were carried out between 500 and 750 degrees C. The results from the activity tests at lambda = 0.25 and gas hourly space velocity of 100 000 h(-1) indicated that the 10 wt.% Ni on Ce0.9La0.1O2 was the best catalyst obtaining 65 and 97% N-2 yield at 500 and 750 degrees C, respectively. By increasing lambda to 0.5 and decreasing the gas hourly space velocity, the N-2 yield improved considerably at low temperature level (500 degrees C). Moreover, NOx emissions maintained at low levels depending on the experimental conditions. Constant conversion and negligible carbon deposition were also two other important observations from the mixed metal oxide supported catalysts. On the contrary, all the alumina-based catalysts displayed the lowest performance. (c) 2007 Elsevier B.V. All rights reserved.