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

Devos, Julien; Bols, Max L.; Plessers, Dieter; Goethem, Cédric Van; Seo, Jin Won; Hwang, Son‐Jong; Sels, Bert F.; Dusselier, Michiel

doi:10.1021/acs.chemmater.9b03738

Cited by 63 publications

(131 citation statements)

References 92 publications

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“…Namely, the Fe located in the 6MRs with paired Al in the CHA framework are the active sites for this reaction. Inspired by this fact, Devos et al prepared a series of SSZ-13 samples (Si/Al = 30-45) from amorphous hydrogel precursors and via interzeolite conversion [221]. The materials prepared via interzeolite conversion possessed more paired Al sites and consequently exhibited higher methanol productivity when Fe-modified SSZ-13 materials were employed as catalysts in partial methane oxidation.…”

Section: Chamentioning

confidence: 99%

Analysis and control of acid sites in zeolites

Palčić

Valtchev

2020

Applied Catalysis A: General

118

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The exceptional catalytic performance of zeolites is due to the presence of active sites in a shape-selective environment, i.e., in micropores with molecular dimensions. The present review provides a comprehensive analysis of active sites in zeolite frameworks. It is focused on the active sites generated by the Al incorporation in the framework. The inclusion of other heteroatoms in the zeolite framework is also addressed. After the introduction of zeolite-type materials and a discussion of the structure-properties relationship in zeolites the central part of the review is devoted to i) the analytical methods and their complementarity for the evaluation of the number, strength, and position of active sites and ii) the in situ and post-synthesis methods of acid sites assessment and control. The data presented herein provide guidelines for making zeolite materials by design in terms of acidity.

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Section: Chamentioning

confidence: 99%

Analysis and control of acid sites in zeolites

Palčić

Valtchev

2020

Applied Catalysis A: General

118

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“…Thus, the occluded SDA play a role in the formation of zeolite phase. 27 Al and 29 Si MAS NMR spectrum of both zeolite samples were almost identical. As mentioned above, the Si/Al ratio obtained from 29 Si MAS NMR spectrum was ca.…”

Section: Resultsmentioning

confidence: 82%

“…The conformational location of SDA, its corresponding effect on the zeolite formation and also the location Al which is major player for catalysis are critical for the understanding the zeolite science and application. 22,27 However, the zeolite CHA is polycrystalline material of which the size is in the range of 1-10 μm, making it difficult to obtain the above-mentioned information. Indeed, the position of SDA in the pore can be average of unlimited number of conformation from all the pore and also due to the high symmetry of zeolite (Supporting Information SI).…”

Section: Introductionmentioning

confidence: 99%

Locating Structure Directing Agent and Al inCHA: Combined Study of Structure Determination of X‐Ray Powder Diffraction and Classical Lattice Energy Calculation

Chang

Park

Cho

2021

Bulletin Korean Chem Soc

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Locating the structure directing agent and Al in zeolite CHA has been performed using structure determination of X‐ray powder diffraction combined with General Utility Lattice Program (GULP) calculation. Trimethyladamantylammonium ion (TMAdaOH+) and benzyltrimethyl ammonium ion (BTMAOH+), respectively, have been found to fit in the pore, resulting in the formation of high silica zeolite CHA, which shows the superior catalytic performance in abatement of NOx using NH3 in the exhaust gas stream of mobile car. The intimate interaction between the corresponding structure directing agent (SDA) and the counter ion due to the Al substitution in the framework has been characterized using the lattice energy calculation. The difference in the lattice energy of the zeolite CHA prepared with TMAdaOH was large compared to that of the zeolite CHA prepared with BTMAOH, which can be attributed probably to the molecule's size. Thereby, the SDA in the zeolite pore has been located readily and the resulting information can be useful for increasing the understanding in the zeolite formation mechanism and designing novel zeolite.

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“…In the end, zeolites crystals will further grow at the crystalliquor interface via successive monomer addition at the expense of the amorphous Si-and Al-source (or solution) or by aggregation of available nanoparticles in non-classical ways. [3][4][5][8][9][10][11][12][13][14] In summary, molecular sieves synthesis in general consists of a complex sequence of steps. For a more detailed understanding, the reader is referred to the reviews of Corma and Davis (2004) 2 , and Cundy and Cox (2003 and 2005) 1,3 and the book "zeolites and catalysis" of Cejka, Corma and Zones (2010) 4 .…”

Section: Conventional Hydrothermal Synthesismentioning

confidence: 99%

“…Novel or more profound insights here could accelerate zeolite catalyst designs for specific reactions. 14…”

Section: Interzeolite Conversion (Izc)mentioning

confidence: 99%

Zeolite Synthesis under Nonconventional Conditions: Reagents, Reactors, andModi Operandi

Deneyer

Devos

et al. 2020

Chem. Mater.

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A myriad of tetrahedral molecular sieve frameworks, often siliceous, can be calculated in silico. Only a tiny fraction (<0.1%) of these can be synthesized on purpose. Only a small fraction of these available frameworks, mostly those composed of only Si and Al as T-atoms, i.e. true zeolites, are used commercially. A gap thus exists between what should be possible (thermodynamically) and what can be produced (kinetically) and used in real life. Even if a synthesis is successful (in industry or academia), flexibility with regard to synthesis parameters -in terms of time, amount of unit operations, OSDA-efficiency, etc. -as well as the obtained material properties -in terms of Si/Al ratio, Al-distribution, T-atom variety, crystal size, etc. -remains limited. These limitations are not surprising since conventional zeolite syntheses, i.e. hydrothermal synthesis in batch from amorphous or soluble Si-and Al-sources, have limited degrees of freedom (DOF). Typically, the type of ingredients, their ratios, a constant temperature, synthesis time and the absence or presence of agitation are varied. In order to take new steps towards more cost-competitive syntheses, and more importantly, zeolites with a greater flexibility in terms of structural properties, this review highlights all DOFs that can be introduced in addition to or on top of the conventional way of synthesis. By doing this, a distinction is made between non-conventional DOFs that influence the chemistry of the system (e.g. interzeolite conversion, charge density mismatch approach, ionothermal or free-radical assisted synthesis) and non-conventional DOFs that influence the physical environment (e.g. ultrasounds, alternative energy via microwaves or continuous set-ups). The review concludes with learnings, practical insights and future opportunities. In other words: which zeolite synthesis strategies really make a difference and which ones are just tweaking around the edges?

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

Cited by 63 publications

References 92 publications

Analysis and control of acid sites in zeolites

Analysis and control of acid sites in zeolites

Locating Structure Directing Agent and Al inCHA: Combined Study of Structure Determination of X‐Ray Powder Diffraction and Classical Lattice Energy Calculation

Zeolite Synthesis under Nonconventional Conditions: Reagents, Reactors, andModi Operandi

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