Acidity and accessibility studies on mesoporous ITQ-4 zeolite

Verboekend, Danny; Villaescusa, Luis A.; Thomas, Karine; Stan, Irina; Pérez‐Ramírez, Javier

doi:10.1016/j.cattod.2010.02.004

Cited by 17 publications

(8 citation statements)

References 24 publications

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“…Molecular sieving can influence reactants and probe molecules. 90,91,97,[629][630][631][632][633][634]636,637,641,653 This section is divided into five subsections. This question is also valid for all sites, and not only for those that are catalytically active.…”

Section: Probe Molecules For Characterization Of Zeolite Basicitymentioning

confidence: 99%

“…[89][90][91]97, The question of the accessibility of catalytic sites in these materials has raised new interest in the use of infrared spectroscopy of probe molecules. 90,91,97,[629][630][631][632][633][634]636,637,641,653 This section is divided into five subsections. The first is devoted to the IR investigation of the influence of pores and confinement on the acid strength of OH groups in the supercage and sodalite cage of H-USY zeolite.…”

Section: Identification and Location Of Sites In The Framework Of Zeo...mentioning

confidence: 99%

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Probing zeolites by vibrational spectroscopies

et al. 2015

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This review addresses the most relevant aspects of vibrational spectroscopies (IR, Raman and INS) applied to zeolites and zeotype materials. Surface Brønsted and Lewis acidity and surface basicity are treated in detail. The role of probe molecules and the relevance of tuning both the proton affinity and the steric hindrance of the probe to fully understand and map the complex site population present inside microporous materials are critically discussed. A detailed description of the methods needed to precisely determine the IR absorption coefficients is given, making IR a quantitative technique. The thermodynamic parameters of the adsorption process that can be extracted from a variable-temperature IR study are described. Finally, cutting-edge space- and time-resolved experiments are reviewed. All aspects are discussed by reporting relevant examples. When available, the theoretical literature related to the reviewed experimental results is reported to support the interpretation of the vibrational spectra on an atomic level.

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Section: Probe Molecules For Characterization Of Zeolite Basicitymentioning

confidence: 99%

Section: Identification and Location Of Sites In The Framework Of Zeo...mentioning

confidence: 99%

Probing zeolites by vibrational spectroscopies

et al. 2015

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“…For example, the accessibility index (ACI) enables to standardise acid site accessibility in zeolites. 52,53 The ACI is determined by relating the amount of acid sites probed by alkylpyridines of different sizes to the total amount of acid sites in the zeolite. For example, pyridine (0.57 nm), able to enter the 90 ZSM-5 micropore (0.56 nm), can probe all sites resulting in an ACI near unity.…”

Section: Descriptorsmentioning

confidence: 99%

Design of hierarchical zeolite catalysts by desilication

Verboekend

Pérez‐Ramírez

2011

Catal. Sci. Technol.

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590

455

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Hierarchical (or mesoporous) zeolites have received an ever-increasing attention due their improved performance in catalysed reactions with respect to conventional (purely microporous) zeolites. Desilication in alkaline media has become a widely applied preparation method to tailor these modified zeolites, due to an optimal combination of efficiency and simplicity. This Minireview presents recent developments that have expanded its general understanding and turned this top-down treatment highly versatile, controllable, and scalable. Design aspects of mesoporous zeolites for catalytic applications are emphasised, encircling the establishment of synthesis-property-function relationships. Alkaline treatment is a key step in strategic combinations with other post-synthesis modifications towards superior zeolite catalysts. The outlook of the field, pinpointing present needs and short-term priorities, is discussed. 65 increased zeolite performance in adsorption and catalysis was first patented in the 1960s. 22 It was claimed that alkaline-treated mordenite displayed preserved crystallinity and a significantly increased benzene adsorption capacity. Moreover, catalytic evaluation in gas-oil hydrocracking revealed a 3 times higher 70 conversion for an alkaline-treated Pd/mordenite than for the untreated catalyst. Already then, Young speculated that the improved performance of the modified material could be due to better access to the micropores. In the 70s, other patents claimed superior properties of alkaline-treated zeolites as olefin 75 adsorbents 23 and molecular sieves, 24 but the obtained benefits remained poorly understood from a scientific ground. Remarkably, open literature concerning zeolite modification in 65 65

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“…9,10 Alkaline-treated zeolites exhibit a decreased bulk Si/Al ratio, micropore volume and crystallinity, and an increased amount of Lewis acid sites. [11][12][13][14][15][16] To avoid possible alteration of the catalytic properties arising from alkali-induced surface realumination, sequential acid treatments are increasingly applied. The additional step aims to restore the original framework composition.…”

Section: Introductionmentioning

confidence: 99%

Decoupling porosity and compositional effects on desilicated ZSM-5 zeolites for optimal alkylation performance

Milina

Mitchell

Trinidad

et al. 2012

Catal. Sci. Technol.

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Desilication of conventional zeolites in alkaline medium generates intracrystalline mesoporosity, but inevitably changes other properties such as the Si/Al ratio and aluminium distribution. Assessing the individual effects of porosity, composition, and acidity on the catalytic performance of desilicated zeolites is relevant for their optimal design. Herein, we decouple the respective impacts in the acid-catalysed 10 alkylation of toluene (or cyclohexylbenzene) with benzyl alcohol. These reactions experience strong accessibility constraints to the micropores, providing high sensitivity to the properties of the developed mesopore surface. Through strategic comparison of alkaline-treated ZSM-5 zeolites prepared with and without subsequent acid treatment, we show that while acidity is important, the alkylation activity is dominated by the mesoporous surface area. The selectivity to (methylbenzyl)benzene does not depend on 15 the available external surface. Large mesopore volumes offer no catalytic benefit, and variation in micropore volume has a minimal effect. Acid-treated mesoporous zeolites exhibit higher catalytic activities primarily due to textural enhancements by removal of aluminium-rich amorphous debris. The catalytic results are rationalised on the basis of extensive characterisation (AAS, N2 sorption, XRD, TEM, 27 Al MAS NMR, FTIR, NH3-TPD) and adsorption of toluene and cyclohexylbenzene.

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Acidity and accessibility studies on mesoporous ITQ-4 zeolite

Cited by 17 publications

References 24 publications

Probing zeolites by vibrational spectroscopies

Probing zeolites by vibrational spectroscopies

Design of hierarchical zeolite catalysts by desilication

Decoupling porosity and compositional effects on desilicated ZSM-5 zeolites for optimal alkylation performance

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