The preparation of some new Pd-Cu and Pd only catalysts dispersed on ZrO2 and SnO2 is reported. All samples are characterized by BET, TPR and powder XRD analysis. The hydrogenation of 100ppm nitrate solutions shows significant differences depending on the pH control method. The Use Of CO2 in the gas feed allows to reduce the formation of ammonia. Pd/SnO2 catalysts represent the best combination between activity and selectivity and both can be improved by decreasing the reduction temperature of the catalyst. These results suggest a possible role for SnOx in the control of the activity and selectivity of the reaction.