Catalytic Wet Oxidation of Ammonia Solution: Activity of the Copper–Lanthanum–Cerium Composite Catalyst

Abstract

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