Explor­ing the Cat­alytic Prop­er­ties of Cu/SSZ-13 using NO Oxi­da­tion and Stan­dard Selec­tive Reduc­tion of NO with NH3

2014 Spring Symposium

Fabio H. Ribeiro*1, W. Nicholas Del­gass1, William F. Schnei­der2, Jef­frey T. Miller3, Alek­sey Yez­erets4, Truno­joyo Anggara2, Christo­pher Paoluc­ci2, Shane A. Bates1, Anuj Ver­ma1, and Atish Parekh1
1School of Chem­i­cal Engi­neer­ing, Pur­due Uni­ver­si­ty, West Lafayette, Indi­ana 47907 (USA)
2Chem­i­cal and Bio­mol­e­c­u­lar Engi­neer­ing, Uni­ver­si­ty of Notre Dame, Notre Dame, Indi­ana
46556 (USA)
3Argonne Nation­al Lab­o­ra­to­ry, Darien, IL 60439 (USA)
4Cum­mins Inc., Colum­bus, IN 47202 (USA)

Abstract — The Cu/SSZ-13 cat­a­lyst (CHA frame­work) is pre­ferred for SCR appli­ca­tions because it shows both SCR per­for­mance and hydrother­mal sta­bil­i­ty. In this work, the site require­ments of the Stan­dard SCR and NO oxi­da­tion reac­tions have been stud­ied on Cu/SSZ-13. Based on an inte­grat­ed exper­i­men­tal and mod­el­ing approach, the active site for the Stan­dard SCR on Cu/SSZ-13 has been assigned to an iso­lat­ed Cu ion locat­ed near the 6 mem­ber rings of SSZ-13, while NO oxi­da­tion required local Cu – O – Cu bonds in the 8 mem­ber cage of SSZ-13. The for­ma­tion of local Cu – O – Cu bonds was a result of sat­u­ra­tion of the num­ber of favor­able Al pairs near the 6 mem­ber ring to sta­bi­lize iso­lat­ed Cu ions. The vari­a­tion of the NO oxi­da­tion and the SCR rates of reac­tion with Cu/Al ratios was thus a cat­alyt­ic con­se­quence of dif­fer­ent Cu ion con­fig­u­ra­tions with­in SSZ-13. The work­ing state of cat­a­lyst under SCR, more­over, was exam­ined by Operan­do X – Ray Absorp­tion Spec­troscopy (XAS). Under reac­tion con­di­tions, the Stan­dard SCR involved a redox mech­a­nism with both Cu(I) and Cu (II) species present. Fur­ther exper­i­ments using operan­do XAS to probe the redox cycle of Cu were car­ried out by remov­ing the oxi­diz­ing half-reac­tion, which pro­duced most­ly the Cu(I) state, and then the reduc­ing half reac­tion, which pro­duced most­ly the Cu(II) state. Thus, any mech­a­nism of Stan­dard SCR has to incor­po­rate a redox cycle. In sum­ma­ry, the stan­dard SCR on Cu-SSZ13 required iso­lat­ed Cu ions to under­go a redox cycle near the 6 mem­ber ring of SSZ13.
Fabio_H_RibeiroBiog­ra­phy — Fabio H. Ribeiro is cur­rent­ly the R. Nor­ris and Eleanor Shreve Pro­fes­sor of Chem­i­cal Engi­neer­ing at the School of Chem­i­cal Engi­neer­ing, Pur­due Uni­ver­si­ty. He received his Ph.D. degree from Stan­ford Uni­ver­si­ty in 1989, held a post-doc­tor­al fel­low­ship at the Uni­ver­si­ty of Cal­i­for­nia – Berke­ley, and was on the Worces­ter Poly­tech­nic Insti­tute fac­ul­ty before join­ing Pur­due Uni­ver­si­ty in August 2003. His research inter­ests con­sist of the kinet­ics of het­ero­ge­neous cat­alyt­ic reac­tions and cat­a­lyst char­ac­ter­i­za­tion by in situ tech­niques. He was Chair for AIChE’s Catal­y­sis and Reac­tion Engi­neer­ing Divi­sion (2010) and is edi­tor for Jour­nal of Catal­y­sis.