Catalytic wet oxidation of ammonia solution: Activity of the copper-lanthanum-cerium composite catalyst

Aqueous solutions that contained 400-1,000 mg/L of ammonia were oxidized in a trickle-bed reactor in this study of copper-lanthanum-cerium composite catalysts, which were prepared by the co-precipitation of copper nitrate, lanthanum nitrate and cerium nitrate at various molar concentrations. Results revealed that the conversion of ammonia by-wet oxidation in the presence of copper-lanthanum-cerium composite catalysts was a function of the molar ratio of the copper-lanthanum-cerium catalyst. The ammonia solutions were barely removed by wet oxidation in the absence of any catalyst, while around 95% of the ammonia was reduced during the wet oxidation over the copper-lanthanum-cerium (7:2:1, molar/molar/molar) catalyst at 503 K and an oxygen partial pressure of 4.0 MPa. The kinetics of ammonia oxidation over a catalyst could be explained by a zero-order rate expression. Furthermore, the effect of the initial concentration and reaction temperature on the removal of ammonia from the effluent streams was also investigated at a liquid hourly space velocity of under 9 h(-1) in wet catalytic processes.