Selective catalytic oxidation of ammonia to nitrogen over zeolite-supported Pt-Au catalysts: Effects of alloy formation and acid sites

Abstract The selective catalytic oxidation of ammonia (NH3-SCO) to N2 and H2O at low temperatures was studied to remove low-concentration (50 ppm) NH3 from the air. A series of mordenite (M20)-supported Pt-Au alloy catalysts with different Pt:Au ratios were synthesized and tested in the NH3-SCO. The NH3 conversion and N2 selectivity both depended on the ratio of Pt to Au. The 0.52 wt% Pt84Au16/M20 catalyst showed the highest NH3 conversion (90% at 144 °C) even better than Pt100/M20, which was ascribed to the combination of electron-deficient Pt and electron-rich Au in the alloy nanoparticles. The effects of acid sites on the NH3-SCO were investigated by NaOH treatment of Pt84Au16/M20 catalyst. Results suggested that the acid sites could help to increase NH3 conversion, and that Bronsted acid sites are essential for the selective formation of N2.