(560fi) Impact of Copper Exchange Protocol on Cu-CHA SCR Activity

One
of the major milestones in environmental catalysis is the abatement of environmentally
harmful compounds such as hydrocarbons, nitrogen oxides (NO_x),
sulfur oxides (SO_x) and carbon monoxide, produced
by automobiles and power sources. The discovery of Cu-CHA as a catalyst for selective
catalytic reduction (SCR) of NO_x was a breakthrough and lead to a
rapid commercialization of the technology for the lean-NO_x emissions
control. It is a relatively new technology and requires more research on
identification of active sites of the catalyst in order to develop next
generation catalysts with improved performance, enhanced stability and low cost.

There
have been considerable research and progress in molecular-level understanding
of the nature of active Cu species and the SCR reaction mechanisms. Unfortunately,
many studies were conducted using Cu-CHA prepared via different synthesis
methods. Current work investigated four methods of preparation of copper
exchanged zeolites reported in the literature and the NOx SCR activities were
examined using a packed bed flow system^1-4. The SCR activities of
each sample were considerably different at lower temperature that is relevant
to the lean-burn engine operational temperature (Figure 1.). The differences
between catalysts prepared via different protocols were further studied by CO
binding experiments where it was revealed that each protocol results in
different copper species within the zeolite framework. DFT calculations were
coupled with CO binding and catalytic results to identify active sites. The
poster will show synthesis, characterization and catalytic testing details and
results. 

Figure 1. NO conversion profiles for
Cu-SSZ-13 samples. Cu-SSZ-13(1-4) were prepared by synthesis protocols reported
by Albarracin-Caballero et al., Fickel et al., Grundner et al., and Kwak et al., respectively.

1.             
Albarracin-Caballero, J. D.;  Khurana, I.;  Di Iorio, J. R.;  Shih, A. J.;  Schmidt, J. E.;  Dusselier, M.;  Davis, M. E.;  Yezerets, A.;  Miller, J. T.;  Ribeiro, F. H.; Gounder, R., Structural
and kinetic changes to small-pore Cu-zeolites after hydrothermal aging
treatments and selective catalytic reduction of NOx with ammonia. React Chem Eng 2017, 2 (2), 168-179.

2.             
Fickel, D. W.; 
Fedeyko, J. M.; Lobo, R. F., Copper Coordination in Cu-SSZ-13 and
Cu-SSZ-16 Investigated by Variable-Temperature XRD. J Phys Chem C 2010, 114 (3), 1633-1640.

3.             
Grundner, S.; 
Markovits, M. A. C.;  Li,
G.;  Tromp, M.;  Pidko, E. A.;  Hensen, E. J. M.;  Jentys, A.;  Sanchez-Sanchez, M.; Lercher, J. A.,
Single-site trinuclear copper oxygen clusters in mordenite for selective conversion
of methane to methanol. Nat Commun 2015, 6.

4.             
Kwak, J. H.; 
Tonkyn, R. G.;  Kim, D.
H.;  Szanyi, J.; Peden, C. H. F.,
Excellent activity and selectivity of Cu-SSZ-13 in the selective catalytic
reduction of NOx with NH3. J Catal 2010, 275 (2), 187-190.