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Urea Decomposition and Implication for NO x Reduction with Cu‐Zeolite and Vanadia‐Selective Catalytic Reduction
Author(s) -
Wu Yi-Jiang,
Wang Fengshuang,
Tang Weiyong,
Kakwani Ramesh,
Hou Yaling,
Feng Gang
Publication year - 2020
Publication title -
chemical engineering and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.403
H-Index - 81
eISSN - 1521-4125
pISSN - 0930-7516
DOI - 10.1002/ceat.202000036
Subject(s) - urea , selective catalytic reduction , catalysis , zeolite , chemistry , decomposition , inorganic chemistry , hydrolysis , thermal decomposition , organic chemistry
Understanding urea decomposition is critical to achieve highly efficient selective catalytic reduction (SCR). The urea decomposition process in an exhaust pipe and in Cu‐zeolite and vanadia‐SCR (V‐SCR) was studied in engine test cells. The unconverted urea at the SCR inlet can be substantial at lower temperatures. HNCO and NH 3 are two dominant products at the SCR inlet. Urea and HNCO continue to decompose in SCR catalysts, with a rate much faster than in the homogeneous stream. The HNCO hydrolysis process is extremely efficient in Cu‐zeolite SCR and the abundant NH 3 from urea overdosing can improve the NO x conversion efficiency. While for V‐SCR, the HNCO hydrolysis reaction can become the rate‐limiting step (especially after aging), abundant urea at low temperatures impairs NO x reduction.