NOx Selective Catalytic Reduction (NOx-SCR) by Urea: Evidence of the Reactivity of HNCO, Including a Specific Reaction Pathway for NOx Reduction Involving NO + NO2

To treat the NOx emissions from diesel vehicles, NOx selective catalytic reduction (SCR) process by NH3 requires the use of a precursor: an urea aqueous solution. Using an innovative experimental synthetic gas bench adjusted to powdered catalysts and allowing the use of urea or ammonia, the competitive reactivity of the HNCO intermediate species was evidenced. This intermediate species was found to be highly reactive toward NO2, without NOx reduction. During the SCR process, a mix of both NO and NO2 was evidenced to react with HNCO and contribute to the NOx reduction efficiency, resulting in an original pathway.

[1]  G. Djéga-Mariadassou,et al.  On the role of organic nitrogen-containing species as intermediates in the hydrocarbon-assisted SCR of NOx , 2004 .

[3]  Pio Forzatti,et al.  Role of ammonia in the reduction by hydrogen of NOx stored over Pt–Ba/Al2O3 lean NOx trap catalysts , 2008 .

[4]  Alexander Wokaun,et al.  Hydrolysis and thermolysis of urea and its decomposition byproducts biuret, cyanuric acid and melamine over anatase TiO2 , 2012 .

[5]  E. Tronconi,et al.  NH3–NO/NO2 chemistry over V-based catalysts and its role in the mechanism of the Fast SCR reaction , 2006 .

[6]  James A. Sullivan,et al.  NH3 and urea in the selective catalytic reduction of NOx over oxide-supported copper catalysts , 2005 .

[7]  T. Schildhauer,et al.  Catalytic urea hydrolysis in the selective catalytic reduction of NOx: catalyst screening and kinetics on anatase TiO2 and ZrO2 , 2013 .

[8]  E. Weitz,et al.  The role of NO in the mechanism of NOx reduction with ammonia over a BaNa-Y catalyst , 2005 .

[9]  Akira Kato,et al.  Reaction between nitrogen oxide (NOx) and ammonia on iron oxide-titanium oxide catalyst , 1981 .

[10]  Daniel Duprez,et al.  Composition-Dependent Performance of CexZr1–xO2 Mixed-Oxide-Supported WO3 Catalysts for the NOx Storage Reduction–Selective Catalytic Reduction Coupled Process , 2013 .

[11]  M. Elsener,et al.  Reaction Pathways in the Selective Catalytic Reduction Process with NO and NO2 at Low Temperatures , 2001 .

[12]  E. Weitz,et al.  A study of the mechanism for NO x reduction with ethanol on ?-alumina supported silver , 2006 .

[13]  Michel Weibel,et al.  NH3–NO/NO2 SCR for Diesel Exhausts Aftertreatment: Reactivity, Mechanism and Kinetic Modelling of Commercial Fe- and Cu-Promoted Zeolite Catalysts , 2009 .

[14]  D. Duprez,et al.  Use of a µ-Scale Synthetic Gas Bench for Direct Comparison of Urea-SCR and NH3-SCR Reactions over an Oxide Based Powdered Catalyst , 2015 .

[15]  M. Iwamoto,et al.  Reaction of adsorbates derived from cyanuric acid on a Cu-MFI zeolite with nitrogen oxide and oxygen , 1996 .

[16]  M. Koebel,et al.  Thermal and Hydrolytic Decomposition of Urea for Automotive Selective Catalytic Reduction Systems: Thermochemical and Practical Aspects , 2003 .