Tuning the Aluminum Distribution in Zeolites to Increase their Performance in Acid‐Catalyzed Reactions

Dědeček, Jiřı́; Tábor, Edyta; Sklenák, Štěpán

doi:10.1002/cssc.201801959

Cited by 149 publications

(136 citation statements)

References 105 publications

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“…longer induction) may differently influence Al incorporation and thus DCC. The correlation between DCC measured by Co-exchange and specific Al arrangements was proven by many authors 38,42 and supported by MPO tests (3.3). Nonetheless it should be acknowledged that the individual contribution of the following factors on DCC and the ion-exchange process cannot be excluded: the effect of lattice faulting, defect sites, exchange against external surface [83][84] or T-atom flexibility 85 and film diffusion boundaries altering molecular cobalt diffusion.…”

Section: Molecular Al-assembly In Ssz-13mentioning

confidence: 64%

“…Assuming a reliable link between DCC and internal Alorganization, 34,40,42 we can now analyze how the investigated parameters in the FAU-to-CHA (Na + -free) crystallization space affect the Al distribution in SSZ-13 and engineer formulations to tune these distributions for specific catalytic applications. The results of the OSDA trend ( Figure 1A) indicate that the most favorable conditions for high DCC are related to fast synthesis kinetics, indicating that OH/Si=0.35 represents excellent conditions for swift SSZ-13 crystallization.…”

Section: Analysis Of Synthetic Factors Contributing To DCC Variationmentioning

confidence: 99%

“…Factors including the method of gel preparation or dilution are known to lead to different mechanisms for crystal formation and Al-distribution at the molecular level. 42 Here we study a controlled standard interzeolite transformation from FAU-to-CHA in time to gain insight into the factors governing DCC creation (Experimental Section 2.3). A series of identical synthesis were stopped at different times and particle morphology and crystallinity were monitored by ex-situ TEM and PXRD respectively.…”

Section: Temporal Analysis Of Fau-to-cha Synthesismentioning

confidence: 99%

“…two tetrahedral Al close enough to exchange divalent cations. 38,42 Such probe method is particularly interesting since it includes effects of site accessibility from the aqueous ion-exchange. However, unambiguously relating the exchange of cobalt species to specific Alarrangements remains a difficult task, especially in zeolites with variable properties such as Si/Al, defect sites and of course the variety of possible T-site combinations (2Al), even for topologies with one crystallographic T-atom position (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis–Structure–Activity Relations in Fe-CHA for C–H Activation: Control of Al Distribution by Interzeolite Conversion

et al. 2019

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The search for structurally relevant Alarrangements in zeolites is an important endeavor for single site catalysis. Little is known about the mechanisms and zeolite dynamics during synthesis that are responsible for creating those Al-ensembles. Here, new synthetic strategies for creating Al-hosts in small-pore zeolites suitable for divalent cation catalysis are uncovered, leading to a mechanistic proposal for Al-organization during crystallization. As such, unique synthesis-structure-activity relations are demonstrated for the partial oxidation of methane on Fe-exchanged CHA-zeolites. With modified interzeolite conversions, the divalent cation capacity of the resulting high Si SSZ-13 zeolites (Si/Al ~ 35) can be reproducibly controlled in a range between 0.04 and 0.34 Co 2+ /Al. This capacity is a proxy for the distribution of framework aluminum in pairs and correlates with the methanol production per Al when these zeolites host the -Fe II redox active site. The uncovered IZC synthesis-structure relations paint an Al-distribution hypothesis, where incongruent dissolution of the starting USY zeolite and fast synthesis kinetics with atypical growth modes allow assembling specific Alarrangements, resulting in a high divalent cation capacity. Prolonged synthesis times and high temperatures overcome the energetic barriers for T-atom reshuffling favoring Al-isolation. These mechanisms and the relations uncovered in this work will guide the search for relevant Al-ensembles in a range of zeolite catalysts where controlling the environment for a single active site is crucial.

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Section: Molecular Al-assembly In Ssz-13mentioning

confidence: 64%

Section: Analysis Of Synthetic Factors Contributing To DCC Variationmentioning

confidence: 99%

Section: Temporal Analysis Of Fau-to-cha Synthesismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Synthesis–Structure–Activity Relations in Fe-CHA for C–H Activation: Control of Al Distribution by Interzeolite Conversion

et al. 2019

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“…Ethanol as a green raw material which can be used in the petrochemical industry as starting material for the production of olefins (C 3 -C 4 ) and aromatics (benzene, toluene and xylene) [3][4][5] . Zeolites, because of their acidic properties-originating in the presence of Al atoms-and porous structures, have been widely studied as catalysts for these reactions 3,6,7 . Recently, it was shown that by controlling Al organization in the zeolite framework, it is possible to tune zeolite catalytic properties for the development of new catalysts and processes [6][7][8][9][10][11][12][13] .…”

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confidence: 99%

The proximity of aluminium atoms influences the reaction pathway of ethanol transformation over zeolite ZSM-5

et al. 2020

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The organization of aluminium atoms in zeolites affects their catalytic properties. Here we demonstrate that the aluminium distribution is a key parameter controlling the reaction pathway of acid catalysed reactions over ZSM-5 zeolites. We study ethanol transformation over two ZSM-5 samples with similar Si/Al ratios of~15, and with aluminium atoms located mainly at the channel intersections but differently distributed in the framework. One of the samples contains mostly isolated aluminium atoms while the other has a large fraction of two aluminium atoms located in one ring. The FT-IR time-resolved operando study, supported by catalytic results, reveals that the reaction pathway in ethanol transformation over ZSM-5 is controlled by the proximity of aluminium atoms in the framework. ZSM-5 containing mostly isolated Al atoms transforms ethanol in the associative pathway, and conversely ZSM-5 containing a dominating fraction of two aluminium atoms in one ring transforms ethanol in the dissociative pathway.

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Unraveling the spatial distribution of the acidity of HZSM‐5 zeolite on the level of crystal grains

et al. 2021

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Here we developed a new method to quantitatively characterize the spatial distribution of the Brønsted acidity of HZSM-5 zeolite on the crystal grains level indirectly. The Brønsted acid sites of HZSM-5 zeolite completely covered or blocked by previous coke deposition were released gradually from the outer surface to the center of the crystal grains via shrinking core mode isothermal oxidation with high temperature and low oxygen concentration. The spatial distribution of the coke was obtained based on the one-dimensional position coordinate L rp through building and solving an enhanced shrinking core model. Then the released acidity characterized by npropylamine temperature-programmed decomposition was correlated to the specific position of L rp. The results show that the acid density is roughly homogenous while the acid strength is heterogeneous within the crystal grains. From the outer surface to the center of the crystal grains, the strength of the Brønsted acid sites increase gradually.

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Tuning the Aluminum Distribution in Zeolites to Increase their Performance in Acid‐Catalyzed Reactions

Cited by 149 publications

References 105 publications

Synthesis–Structure–Activity Relations in Fe-CHA for C–H Activation: Control of Al Distribution by Interzeolite Conversion

Synthesis–Structure–Activity Relations in Fe-CHA for C–H Activation: Control of Al Distribution by Interzeolite Conversion

The proximity of aluminium atoms influences the reaction pathway of ethanol transformation over zeolite ZSM-5

Unraveling the spatial distribution of the acidity of HZSM‐5 zeolite on the level of crystal grains

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