Impact of Copper Loading on NH3-Selective Catalytic Reduction, Oxidation Reactions and N2O Formation over Cu/SAPO-34

We developed a procedure for aqueous ion exchange to obtain different Cu loadings of Cu/SAPO-34 (between 0 and 2.6 wt %.) The catalysts were washcoated on monoliths and characterised with respect to their activity and selectivity under standard selective catalytic reduction (SCR), fast SCR, NH3 oxidation and NO oxidation reactions. They were further characterised using X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), H2-temperature programmed reduction (H2-TPR), ultraviolet (UV)-vis spectroscopy and NH3 adsorption. As expected, activity of all reactions increased with copper loading, due to increased number of active sites. However, the N2O formation during standard and fast SCR yielded interesting mechanistic information. We observed that N2O formation at low temperature increased with copper loading for the standard SCR reaction, while it decreased for fast SCR. The low-temperature N2O formation during fast SCR thus occurs predominantly over Bronsted sites. Species responsible for N2O formation during standard SCR, on the other hand, are formed on the copper sites. We further found that the fast SCR reaction occurs to a significant extent even over the H/SAPO-34 form. The Bronsted sites in SAPO-34 are thus active for the fast SCR reaction.

[1]  J. Weitkamp,et al.  Zeolites and catalysis , 2000 .

[2]  Hong-xin Li,et al.  Effect of Cu-loading and structure on the activity of Cu-exchanged zeolites for NH3-SCR , 2008 .

[3]  Tie Yu,et al.  The effect of various templates on the NH3-SCR activities over Cu/SAPO-34 catalysts , 2014 .

[4]  L. Fu,et al.  Characterization of commercial Cu-SSZ-13 and Cu-SAPO-34 catalysts with hydrothermal treatment for NH3-SCR of NOx in diesel exhaust , 2013 .

[5]  Pio Forzatti,et al.  Present status and perspectives in de-NOx SCR catalysis , 2001 .

[6]  Junhui Li,et al.  The Effect of NO2/NOx Feed Ratio on the NH3-SCR System Over Cu–Zeolites with Varying Copper Loading , 2013, Catalysis Letters.

[7]  L. Fu,et al.  In situ DRIFTS and temperature-programmed technology study on NH3-SCR of NOx over Cu-SSZ-13 and Cu-SAPO-34 catalysts , 2014 .

[8]  Louise Olsson,et al.  Deactivation of Cu/SAPO-34 during low-temperature NH3-SCR , 2015 .

[9]  A. Nicolle,et al.  Hydrothermal aging effects on Cu-zeolite NH3-SCR catalyst , 2015 .

[10]  Tie Yu,et al.  The effect of synthesis methods on Cu species and active sites over Cu/SAPO-34 for NH3-SCR reaction , 2013 .

[11]  Martyn V. Twigg,et al.  “Urea-SCR Technology for deNOx After Treatment of Diesel Exhausts” , 2015 .

[12]  E. Walter,et al.  Structure–activity relationships in NH3-SCR over Cu-SSZ-13 as probed by reaction kinetics and EPR studies , 2013 .

[13]  M. Shelef.  Selective Catalytic Reduction of NOx with N-Free Reductants , 1995 .

[14]  G. Mauviot,et al.  Modeling of a DOC SCR-F SCR Exhaust Line for Design Optimization Taking Into Account Performance Degradation Due to Hydrothermal Aging , 2016 .

[15]  A. Prakash,et al.  Synthesis of SAPO-34: high silicon incorporation in the presence of morpholine as template , 1994 .

[16]  Peter N. R. Vennestrøm,et al.  Migration of Cu Ions in SAPO-34 and Its Impact on Selective Catalytic Reduction of NOx with NH3 , 2013 .

[17]  Lothar Mussmann,et al.  Influence of NO2 on the selective catalytic reduction of NO with ammonia over Fe-ZSM5 , 2006 .

[18]  Junhui Li,et al.  The effect of Cu-loading on different reactions involved in NH3-SCR over Cu-BEA catalysts , 2014 .

[19]  C. H. Bartholomew,et al.  Kinetic and Mechanistic Study of NO x Reduction by NH 3over H-Form Zeolites , 1997 .

[20]  J. H. Lee,et al.  The Effect of Copper Loading on the Selective Catalytic Reduction of Nitric Oxide by Ammonia Over Cu-SSZ-13 , 2012, Catalysis Letters.

[21]  Olaf Deutschmann,et al.  Heterogeneous Catalysis and Solid Catalysts, 1. Fundamentals , 2011 .

[22]  W. Li,et al.  The influence of silicon on the catalytic properties of Cu/SAPO-34 for NOx reduction by ammonia-SCR , 2012 .

[23]  J. Pihl,et al.  Fe-Zeolite Functionality, Durability, and Deactivation Mechanisms in the Selective Catalytic Reduction (SCR) of NO x with Ammonia , 2014 .

[24]  Tie Yu,et al.  NH3-SCR over Cu/SAPO-34 catalysts with various acid contents and low Cu loading , 2013 .

[25]  Junhui Li,et al.  Investigation of the Effect of Accelerated Hydrothermal Aging on the Cu Sites in a Cu-BEA Catalyst for NH3-SCR Applications , 2013, Topics in Catalysis.

[26]  Di Wang,et al.  NH3-SCR over Cu/SAPO-34 – Zeolite acidity and Cu structure changes as a function of Cu loading , 2014 .

[27]  Krishna Kamasamudram,et al.  A multi-site kinetic model for NH3-SCR over Cu/SSZ-13 , 2015 .

[28]  Kuo Liu,et al.  High hydrothermal stability of Cu–SAPO-34 catalysts for the NH3-SCR of NOx , 2016 .

[29]  E. Tronconi,et al.  The chemistry of the NO/NO2–NH3 “fast” SCR reaction over Fe-ZSM5 investigated by transient reaction analysis , 2008 .

[30]  Y. M. Zhou,et al.  A review on selective catalytic reduction of NOx by supported catalysts at 100–300 °C—catalysts, mechanism, kinetics , 2014 .

[31]  P. Man,et al.  Influence of the Choice of the Template on the Short- and Long-Term Stability of SAPO-34 Zeolite , 1995 .

[32]  Marina Weber.  Reflectance Spectroscopy Principles Methods Applications , 2016 .

[33]  Jihui Wang,et al.  Recent advances in the selective catalytic reduction of NOx with NH3 on Cu-Chabazite catalysts , 2017 .

[34]  Hong He,et al.  Emerging Applications of Environmentally Friendly Zeolites in the Selective Catalytic Reduction of Nitrogen Oxides , 2016 .

[35]  Z. Sobalík,et al.  Coordination of Cu Ions in High-Silica Zeolite Matrixes. Cu+ Photoluminescence, IR of NO Adsorbed on Cu2+, and Cu2+ ESR Study , 1995 .

[36]  C. Peden,et al.  Two different cationic positions in Cu-SSZ-13? , 2012, Chemical communications.

[37]  W. Li,et al.  Location and nature of Cu species in Cu/SAPO-34 for selective catalytic reduction of NO with NH3 , 2012 .

[38]  W. Grünert,et al.  The role of NO2 in the selective catalytic reduction of nitrogen oxides over Fe-ZSM-5 catalysts : Active sites for the conversion of NO and of NO/NO2 mixtures , 2008 .

[39]  S. Oh,et al.  Hydrothermal stability of CuZSM5 catalyst in reducing NO by NH3 for the urea selective catalytic reduction process , 2006 .

[40]  D. Weng,et al.  Migration of Cu species in Cu/SAPO-34 during hydrothermal aging , 2013 .

[41]  E. Walter,et al.  Synthesis and Evaluation of Cu-SAPO-34 Catalysts for Ammonia Selective Catalytic Reduction. 1. Aqueous Solution Ion Exchange , 2013 .

[42]  Wei Li,et al.  Characterization of copper species over Cu/SAPO-34 in selective catalytic reduction of NOx with ammonia: Relationships between active Cu sites and de-NOx performance at low temperature , 2013 .

[43]  B. Wichterlová,et al.  Role of Hydrated Cu Ion Complexes and Aluminum Distribution in the Framework on the Cu Ion Siting in ZSM-5 , 1997 .

[44]  Feng Gao,et al.  A comparative kinetics study between Cu/SSZ-13 and Fe/SSZ-13 SCR catalysts , 2015 .

[45]  Krishna Kamasamudram,et al.  Comparison of Cu/BEA, Cu/SSZ-13 and Cu/SAPO-34 for ammonia-SCR reactions , 2015 .

[46]  F. Ribeiro,et al.  Identification of the active Cu site in standard selective catalytic reduction with ammonia on Cu-SSZ-13 , 2014 .

[47]  Russell G. Tonkyn,et al.  Excellent activity and selectivity of Cu-SSZ-13 in the selective catalytic reduction of NOx with NH3 , 2010 .

[48]  Raul F. Lobo,et al.  The ammonia selective catalytic reduction activity of copper-exchanged small-pore zeolites , 2011 .

[49]  Krishna Kamasamudram,et al.  Mechanistic investigation of hydrothermal aging of Cu-Beta for ammonia SCR , 2011 .

[50]  E. Tronconi,et al.  Diesel NOx aftertreatment catalytic technologies: Analogies in LNT and SCR catalytic chemistry , 2010 .

[51]  Tie Yu,et al.  The migration of Cu species over Cu–SAPO-34 and its effect on NH3 oxidation at high temperature , 2014 .

[52]  E. Walter,et al.  Synthesis and evaluation of Cu/SAPO-34 catalysts for NH 3 -SCR 2: Solid-state ion exchange and one-pot synthesis , 2015 .