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

Kalantzopoulos, Georgios N.; Rojo-Gama, Daniel; Pappas, Dimitrios; Dovgaliuk, Iurii; Olsbye, Unni; Beato, Pablo; Lundegaard, L. F.; Wragg, David S.; Svelle, Stian

doi:10.1039/d2dt02845j

Cited by 10 publications

(7 citation statements)

References 51 publications

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“…The refinement of XRD data allows for the acquisition of critical information on lattice changes resulting from ion exchange or heteroatom substitution, which can be used to establish correlations between active sites and catalytic performance. 49,51,52 Herein, we aimed to investigate the correlation between tin incorporation and lattice dimensions by measuring a series of Sn-Beta zeotypes with varying tin loadings and synthesis methods. The resulting lattice parameters are presented in Figure 3 and Table S1.…”

Section: Lattice Distortion Of Ht and Pt Sn-beta Zeotypes 321 Structu...mentioning

confidence: 99%

Tracking Lattice Distortion Induced by Defects and Framework Tin in Beta Zeotypes

Bai,

Taarning,

Luthra

et al. 2023

J. Phys. Chem. C

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The use of powder X-ray diffraction (PXRD) coupled with lattice parameter refinement is used to investigate the crystal structure of Sn-Beta materials. A newly developed semiempirical PXRD model with a reduced tetragonal unit cell is applied to obtain the characteristic crystallographic features. There is a robust correlation between lattice parameters and the concentration of tin and defects for materials prepared via hydrothermal (HT) and postsynthetic (PT) methods. With tin incorporation, PT Sn-Beta samples, which possess a more defective structure, exhibit an extended interlayer distance in the stacking sequence and expansion of the translation symmetry within the layers, leading to larger unit cell dimensions. In contrast, HT Sn-Beta samples, having fewer defects, show a minimal effect of tin site density on the unit cell volume, whereas lattice distortion is directly correlated to the framework tin density. Furthermore, density functional theory (DFT) studies support an identical trend of lattice distortion following the monoisomorphous substitution of T sites from silicon to tin. These findings highlight that PXRD can serve as a rapid and straightforward characterization method to evaluate both framework defects and heteroatom density, offering a novel approach to monitor structural changes and the possibility to evaluate the catalytic properties of heteroatom-incorporated zeotypes.

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Section: Lattice Distortion Of Ht and Pt Sn-beta Zeotypes 321 Structu...mentioning

confidence: 99%

Tracking Lattice Distortion Induced by Defects and Framework Tin in Beta Zeotypes

Bai,

Taarning,

Luthra

et al. 2023

J. Phys. Chem. C

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“…Rapid cell expansion during the induction period and further gradual increase of the unit cell over time on stream have also been demonstrated for ZSM-22 zeolite in MTH reaction . A similar effect of light adsorbates on the unit cell was also observed by Kalantzopoulos et al for HZSM-5 . After the methanol was switched off, we observed the contraction of the unit cell for HZSM-5 and Na/ZSM-5 catalysts.…”

Section: Resultsmentioning

confidence: 51%

“… 111 A similar effect of light adsorbates on the unit cell was also observed by Kalantzopoulos et al for HZSM-5. 112 After the methanol was switched off, we observed the contraction of the unit cell for HZSM-5 and Na/ZSM-5 catalysts. In contrast, Ca/ZSM-5 demonstrated different dynamics of the pore expansion and contraction, specifically a larger increase of the cell volume upon exposure to methanol, which indicates that more adsorbates were retained in the presence of Ca 2+ ions ( Figure 12 c).…”

Section: Resultsmentioning

confidence: 89%

Ca Cations Impact the Local Environment inside HZSM-5 Pores during the Methanol-to-Hydrocarbons Reaction

et al. 2023

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The methanol-to-hydrocarbons (MTH) process is an industrially relevant method to produce valuable light olefins such as propylene. One of the ways to enhance propylene selectivity is to modify zeolite catalysts with alkaline earth cations. The underlying mechanistic aspects of this type of promotion are not well understood. Here, we study the interaction of Ca2+ with reaction intermediates and products formed during the MTH reaction. Using transient kinetic and spectroscopic tools, we find strong indications that the selectivity differences between Ca/ZSM-5 and HZSM-5 are related to the different local environment inside the pores due to the presence of Ca2+. In particular, Ca/ZSM-5 strongly retains water, hydrocarbons, and oxygenates, which occupy as much as 10% of the micropores during the ongoing MTH reaction. This change in the effective pore geometry affects the formation of hydrocarbon pool components and in this way directs the MTH reaction toward the olefin cycle.

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“…These coke mechanisms on ZSM-5 zeolites have also been reported using other techniques, such as operando X-ray diffraction. 69 In terms of carbon number, this external coke is measured within the insoluble coke fraction and the total coke is measured by direct analysis. Interestingly, that does not happen in terms of the DBE, i.e., the external coke measured within the insoluble coke fraction (with DBE >ca.…”

Section: Discussionmentioning

confidence: 99%

“…These coke mechanisms on ZSM-5 zeolites have also been reported using other techniques, such as operando X-ray diffraction. 69…”

Section: Discussionmentioning

confidence: 99%

Direct analysis at temporal and molecular level of deactivating coke species formed on zeolite catalysts with diverse pore topologies

Hita

Mohamed

Yerrayya

et al. 2023

Catal. Sci. Technol.

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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...

Cited by 10 publications

References 51 publications

Tracking Lattice Distortion Induced by Defects and Framework Tin in Beta Zeotypes

Tracking Lattice Distortion Induced by Defects and Framework Tin in Beta Zeotypes

Ca Cations Impact the Local Environment inside HZSM-5 Pores during the Methanol-to-Hydrocarbons Reaction

Direct analysis at temporal and molecular level of deactivating coke species formed on zeolite catalysts with diverse pore topologies

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