NO2− adsorption onto denitration catalysts

The performance of denitration catalysts is usually evaluated according to the concentrations of NO3−, NO2− and NH4+ ions. Catalytic conversion is conventionally calculated from the decrease of NO3− and NO2− in the reaction solution. In this study, batch experiments were performed by contacting NO2− with Pt/Al2O3 under the presence or absence of H2 flow. Significant amounts of NO2− in the reaction solution disappeared even in the absence of H2, i.e., under conditions where reduction did not occur. This phenomenon is explained by NO2− adsorption onto Al2O3. The equilibrium amount of adsorbed NO2− showed a linear decrease with the increase of Pt particles. The adsorption of NO2− onto Al2O3 should be considered when the performance of denitration catalysts is evaluated. In addition, utilizing the high adsorption capacity of Al2O3 for NO2− may realize its potential as a scavenger for the removal of NO2− ions in waste water.

Graphical abstract2 mmol L−1 NaNO2 was reduced by H2 gas on 0.1 wt% Pt/Al2O3 catalyst. The decrease of NO2− (○) was found to be caused by catalytic conversion to N2 or NH4+, and by adsorption onto alumina (▵). The result suggests that a significant amount of NO2− can be adsorbed by alumina and this should be considered when we discuss catalytic conversion and selectivity.Figure optionsDownload full-size imageDownload as PowerPoint slide