The promotional effect of SO42- on N-2 selectivity for selective catalytic oxidation of ammonia over RuO2/ZrO2 catalyst

摘要

The promoting effects of SO42- on N-2 selectivity for selective catalytic oxidation (SCO) of ammonia to nitrogen over RuO2/ZrO2 catalyst were systematically investigated. The catalysts were measured by different characterization methods (BET, XRD, TEM, NH3-TPD and in situ DRIFTS). The results showed that the introduction of SO42- into RuO2/ZrO2 presented obvious effects on the structure, surface acidity and N-2 selectivity of RuO2/ZrO2. The introduction of SO42- obviously increased the amount of surface acid sites, which could promote the adsorption of ammonia species and prevent the excessive oxidation of ammonia to NOx, improving the N-2 selectivity dramatically. The DRIFTS results confirmed that the SCO of ammonia over RuO2/ZrO2-SO42- followed the in situ selective catalytic reduction of NOx (i-SCR) mechanism, involving NH3 oxidation to NO species and -NH2 reacted with NO to form the main product N-2. The presence of SO42- not only increased the surface acid sites of the catalyst, but also inhibited the production of nitrate species, which was beneficial to improve the N-2 selectivity.