Two-stage catalyst system for selective catalytic reduction of NOx by NH3 at low temperatures

• Published in: Applied catalysis. B, Environmental Vol. 68; no. 1-2; pp. 21 - 27
• Main Authors: Kang, Min, Kim, Dae Jung, Park, Eun Duck, Kim, Ji Man, Yie, Jae Eui, Kim, Seoung Hyun, Hope-Weeks, Louisa, Eyring, Edward M.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 26-10-2006; Elsevier
• Subjects: Catalysis; Chemistry; Cu catalyst; Exact sciences and technology; General and physical chemistry; NH3 SCR; NO oxidation; Pt catalyst; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Two-stage catalyst system; Cu catalyst; NO oxidation; NH3 SCR; Two-stage catalyst system; Pt catalyst; Nitrogen oxide; Oxygen; Catalytic reaction; Transition metal; Supported catalyst; Chemical reduction; Ammonia; Heterogeneous catalysis; Platinum; Nitric oxide; Oxidation; Carbon monoxide; Copper; Alumina; Low temperature; Environmental protection
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2006.07.013

Three catalysts, 1wt.% Pt/Al2O3, 20wt.% Cu/Al2O3, and 1wt.% Pt–20wt.% Cu/Al2O3 were evaluated for the oxidation of NO by O2 and the selective catalytic reduction (SCR) of NOx by NH3 in the absence and presence of H2O. The Pt/Al2O3 catalyst exhibited the largest values in NO oxidation efficiency and NOx removal efficiency among the three catalysts. The presence of H2O caused a drop in the NO oxidation and the SCR activities. The SCR performance was significantly improved when Pt/Al2O3 and Cu/Al2O3 catalysts were employed sequentially in a reactor. The highest SCR performance was achieved using two separate stages: oxidation of NO by O2 over the Pt/Al2O3 catalyst followed by reduction of NO2 by NH3 over the Cu/Al2O3 catalyst. Under the condition with H2O, the two-stage catalyst system showed NOx removal efficiency over 80% at low temperatures below 200°C, which was the highest value among the catalyst systems used in this study. The physical and chemical properties of the catalysts were determined using nitrogen adsorption, XRD, TPR, and pulse CO chemisorption experiments.