Issue 44, 2022

Real-time regeneration of a working zeolite monitored via operando X-ray diffraction and crystallographic imaging: how coke flees the MFI framework

Abstract

We have monitored the regeneration of H-ZSM-5 via operando time-resolved powder X-Ray diffraction (PXRD) coupled with mass spectroscopy (MS). Parametric Rietveld refinements and calculation of the extra-framework electronic density by differential Fourier maps analysis provide details on the mode of coke removal combined with the corresponding sub-unit cell changes of the zeolite structure. It is clear that the coke removal is a complex process that occurs in at least two steps; a thermal decomposition followed by oxidation. In a coked zeolite, the straight 10-ring channel circumference is warped to an oval shape due to structural distortion induced by rigid aromatic coke species. The data presented explain why the difference in length between the a-vector and the b-vector of the MFI unit cell is a robust descriptor for bulky coke, as opposed to the unit cell volume, which is affected also by adsorbed species and thermal effects. Our approach holds the promise to quantify and identify coke removal (and formation) in structurally distinct locations within the zeolite framework.

Graphical abstract: Real-time regeneration of a working zeolite monitored via operando X-ray diffraction and crystallographic imaging: how coke flees the MFI framework

Supplementary files

Article information

Article type
Paper
Submitted
31 8 2022
Accepted
19 10 2022
First published
19 10 2022
This article is Open Access
Creative Commons BY license

Dalton Trans., 2022,51, 16845-16851

Real-time regeneration of a working zeolite monitored via operando X-ray diffraction and crystallographic imaging: how coke flees the MFI framework

G. N. Kalantzopoulos, D. Rojo Gama, D. K. Pappas, I. Dovgaliuk, U. Olsbye, P. Beato, L. F. Lundegaard, D. S. Wragg and S. Svelle, Dalton Trans., 2022, 51, 16845 DOI: 10.1039/D2DT02845J

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