Size and Shape Effect of Metal Oxides on Hydrocarbon Selective Catalytic Reduction of Nitrogen Oxides

This work investigated the size and shape effect of -alumina-supported metal oxides on the hydrocarbon selective catalytic reduction of nitrogen oxides. Several metal oxides including Ag, Cu and Ru were used as the catalysts, and n-heptane as the reducing agent. For the Ag/-alumina catalyst, the reduction efficiency in the range of increased as the size of Ag decreased (20 nm>50 nm>80 nm). The shape effect of metal oxides on the reduction was examined with spherical- and wire-shape nanoparticles. Under identical condition, higher catalytic activity for reduction was observed with Ag and Cu wires than with the spheres, while spherical- and wire-shape Ru exhibited similar reduction efficiency to each other. Among the metal oxides examined, the best catalytic activity for reduction was obtained with Ag wire, showing almost complete removal at a temperature of . For Cu and Ru catalysts, considerable amount of NO was oxidized to , rather than reduced to , leading to lower reduction efficiency.