Cloth catalysts in water denitrification: III. pH inhibition of nitrite hydrogenation over Pd/ACC

Nitrite hydrogenation over Pd supported on an activated carbon cloth (ACC) has been investigated in an isothermal semi-batch reactor. The reaction is accompanied by increasing pH, which inhibits the reaction. The rate was corrected for pH changes and the reaction was found to be first-order with respect to nitrite concentration and zero-order with respect to hydrogen pressure. The corrected rate constant is of the form keff=k exp[(pH−pzc)/(pH0−pzc)], where k is the intrinsic constant and the pzc is the point of zero charge of catalyst surface. While Pd/ACC catalysts yield better rates than those of Pd supported on glass fiber cloth (GFC), they exhibit much poorer selectivity (in the unbuffered reaction conditions) due to ACC surface enrichment by hydrogen.