Mechanism of the Selective Catalytic Oxidation of Slip Ammonia over Ru-Modified Ce–Zr Complexes Determined by in Situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy

• Published in: Environmental science & technology Vol. 48; no. 20; pp. 12199 - 12205
• Main Authors: Chen, Wanmiao, Ma, Yongpeng, Qu, Zan, Liu, Qinghang, Huang, Wenjun, Hu, Xiaofang, Yan, Naiqiang
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 21.10.2014
• Subjects: Adsorption; Air Pollutants - chemistry; Ammonia; Ammonia - chemistry; Applied sciences; Atmospheric pollution; Catalysis; Catalysts; Catalytic oxidation; Cerium - chemistry; Combustion and energy production; Exact sciences and technology; Fourier transforms; Nitric Oxide - chemistry; Oxidation-Reduction; Oxides - chemistry; Oxygen - chemistry; Pollution; Povidone; Prevention and purification methods; Rubidium - chemistry; Solid solutions; Spectroscopy, Fourier Transform Infrared; Spectrum analysis; Sulfur Dioxide - chemistry; Zirconium - chemistry; Cerium Zirconium Oxides Mixed; Nitrogen oxide; Ruthenium addition; Reaction product; Nitrogen compounds; Doped materials; Reflection spectrometry; Ammonia; Coal power plant; Reaction mechanism; Poison; Physicochemical purification; Oxidation; Fourier-transformed infrared spectrometry; Selective catalytic reduction; Catalyst activity; Flue gas purification; Catalyst; Modified material
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es502369f

The slip ammonia from selective catalytic reduction (SCR) of NO x in coal-fired flue gas can result in deterioration of the utilities or even the environmental issues. To achieve selective catalytic oxidation (SCO) of slip ammonia, Ru-modified Ce–Zr solid solution catalysts were prepared and evaluated under various conditions. It was found that the Ru/Ce0.6Zr0.4O2(polyvinylpyrrolidone (PVP)) catalyst displayed significant catalytic activity and the slip ammonia was almost completely removed with the coexistence of NO x and SO2. Interestingly, the effect of SO2 on NH3 oxidation was bifacial, and the N2 selectivity of the resulting products was as high as 100% in the presence of SO2 and NH3. The mechanism of the SCO of NH3 over Ru/Ce0.6Zr0.4O2(PVP) was studied using various techniques, and the results showed that NH3 oxidation follows an internal SCR (iSCR) mechanism. The adsorbed ammonia was first activated and reacted with lattice oxygen atoms to form an −HNO intermediate. Then, the −HNO mainly reacted with atomic oxygen from O2 to form NO. Meanwhile, the formed NO interacted with −NH2 to N2 with N2O as the byproduct, but the presence of SO2 can effectively inhibit the production of N2O.