(758d) DFT Investigations for the Influence of the Framework Topology in Cu2+ Exchange and Siting Preference in Zeolites | AIChE

(758d) DFT Investigations for the Influence of the Framework Topology in Cu2+ Exchange and Siting Preference in Zeolites

Authors 

Zhao, Z. - Presenter, University of Notre Dame
Li, S., University of Notre Dame
Wang, Y., University of Notre Dame
Prasad, S., BASF Corporation
Moini, A., BASF Catalysts LLC
Gounder, R., Purdue University
Schneider, W., University of Notre Dame
Ion-exchanged zeolites are widely used as heterogenous catalysts. In particular, Cu-SSZ-13 (CHA) is the on-board catalysts for NOX selective catalytic reduction (SCR) with NH3. Previous works have shown Cu2+ is exchanged in CHA as ZCuOH, Z2Cu or oxo dimer, where Z indicates a framework Al.1 Both computational and experimental results show ZCuOH in CHA resides in the large 8-membered-ring (8MR) openings, and Z2Cu in CHA prefers to coordinate with 2ndand 3rd nearest neighbor Al pairs in 6MR.1 Since CHA has 3-dimensional pore openings and only 1 symmetry-distinct T-site, how the Cu2+ speciation and siting preference will differ for frameworks with more symmetry-distinct T-site and less dimensional pore openings are still unclear. In this work, we performed plane-wave-based Density Functional Theory (DFT) supercell calculations to investigate the Cu2+ exchange and siting preference in 4 different frameworks. We choose other zeolite frameworks with different dimensional pore openings and numbers of T-sites to be compared with CHA to compare ZCuOH, Z2Cu and Cu dimer exchange energies and siting preferences in those frameworks. We improved a previous reported variable charge model to correlate the Z2Cu exchange energies with descriptors by including symmetry-related factors.2 This work can help the predictions of Cu2+ exchange in other zeolite frameworks to choose a specific zeolite framework for a particular Cu2+ exchange functionality.

[1] Paolucci, Christopher, et al. Journal of the American Chemical Society 138.18 (2016): 6028-6048.

[2] Li, Sichi, et al. The Journal of Physical Chemistry C 122.41 (2018): 23564-23573.