Synthesis gas generated by the gasification of nitrogen-containing hydrocarbons will contain ammonia. This is a catalyst poison and elevated levels of nitrogen oxides (NOX) will be produced if the synthesis gas is combusted. This paper presents a study of the selective oxidation of ammonia in reducing environments. The concept is the same as in traditional selective catalytic reduction, where NOX are removed from flue gas by reaction with injected ammonia over a catalyst. Here, a new concept for the removal of ammonia is demonstrated by reaction with injected NOX over a catalyst. The experiments were carried out in a model synthesis gas consisting of CO, CO2, H-2, N-2 and NH3/NOX. The performance of two catalysts, V2O5/WO3/TiO2 and H-mordenite, were evaluated. On-site generation of NOX by nitric acid decomposition was also investigated and tested. The results show good conversion of ammonia under the conditions studied for both catalysts, and with on-site generated NOX. (C) 2012 Elsevier Ltd. All rights reserved.