Copper Coordination in Cu-SSZ-13 and Cu-SSZ-16 Investigated by Variable-Temperature XRD

2010 Spring Symposium

Dustin W. Fick­el and Raul F. Lobo
*Cen­ter for Cat­alyt­ic Sci­ence and Tech­nol­o­gy
Depart­ment of Chem­i­cal Engi­neer­ing
Uni­ver­si­ty of Delaware
Newark, Delaware 19716

Abstract — Nitro­gen oxides (NOx) are a major atmos­pher­ic pol­lu­tant pro­duced through the com­bus­tion of fos­sil fuels in inter­nal com­bus­tion engines. Cop­per-exchanged zeo­lites are promis­ing as selec­tive cat­alyt­ic reduc­tion cat­a­lysts for the direct con­ver­sion of NO into N2 and O2, and recent reports have shown the enhanced per­for­mance of Cu-CHA cat­a­lysts over oth­er zeo­lite frame­works in the NO decom­po­si­tion of exhaust gas streams.

In the present study, Rietveld refine­ment of vari­able-tem­per­a­ture XRD syn­chro­tron data obtained for Cu-SSZ-13 and Cu-SSZ-16 is used to inves­ti­gate the loca­tion of cop­per cations in the zeo­lite pores and the effect of tem­per­a­ture on these sites and on frame­work sta­bil­i­ty. The XRD pat­terns show that the ther­mal sta­bil­i­ty of SSZ-13 is increased sig­nif­i­cant­ly when cop­per is exchanged into the frame­work com­pared with the acid form of the zeo­lite, H-SSZ-13. Cu-SSZ-13 is also more ther­mal­ly sta­ble than Cu-SSZ-16. From the refined dif­frac­tion pat­terns, the atom­ic posi­tions of atoms, cop­per loca­tions and occu­pan­cies, and ther­mal dis­place­ment para­me­ters were deter­mined as a func­tion of tem­per­a­ture for both zeo­lites. Cop­per is found in the cages coor­di­nat­ed to three oxy­gen atoms of the six-mem­bered rings. This study also shows the enhanced per­for­mance of cop­per exchanged small-pore zeo­lites towards the selec­tive cat­alyt­ic reduc­tion of nitric oxide com­pared to Cu-ZSM-5 after hydrother­mal­ly treat­ing the zeo­lites.

* Fick­el, D.W., Lobo, R.F., Cop­per Loca­tion Study of Cu-SSZ-13 and Cu-SSZ-16 Vari­able Tem­per­a­ture XRD Riet­feld Refine­ment, J. Phys. Chem. C, DOI: 10.1021/jp9105025.