Ozone catalytic oxidation for ammonia removal from simulated air at room temperature

Abstract

Ozone catalytic oxidation (OZCO) for removing ammonia from simulated air over the AgMn/HZSM-5 (AgMn/HZ) catalyst with high ammonia conversion and high N₂ selectivity at room temperature is reported for the first time. HZ, Ag/HZ, Mn/HZ and AgMn/HZ catalysts were compared in the OZCO reactions of gaseous and adsorbed NH₃. In OZCO of gaseous NH₃, N₂ was the major product and N₂O was the minor product. NH₃ conversion dropped quickly with time-on-stream (TOS) over HZ and Ag/HZ catalysts while it remained almost constant at a high level over Mn/HZ and AgMn/HZ catalysts during the entire test. N₂ selectivity of the AgMn/HZ catalyst was higher than that of the Mn/HZ catalyst. When the initial concentration of NH₃ was 521 ppmv and the ratio of initial concentration of O₃ to NH₃ was 1.73, 99% NH₃ conversion with 94% N₂ selectivity was obtained over the AgMn/HZ catalyst at room temperature and 150 000 ml g⁻¹ h⁻¹ gas hourly space velocity (GHSV). Finally, the pathways for OZCO of NH₃ were proposed for the four catalysts based on the comparative investigation of the gaseous products and surface species during OZCO of adsorbed and gaseous NH₃.