Aei

Baerlocher, Ch.; Meier, W.M.; Olson, David H.

doi:10.1016/b978-044450701-3/50294-9

Cited by 262 publications

(411 citation statements)

References 1 publication

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“…Mineral SOD is a fully ordered aluminosilicate framework with a framework density of approximately 16.7 tetrahedra per 1000 Å 3 [ 3 ]. However, a pure silica SOD has been produced by an unusual non-aqueous synthesis [ 15 ].…”

Section: Resultsmentioning

confidence: 99%

Defining the flexibility window in ordered aluminosilicate zeolites

Wells

Leung²,

Edwards³

et al. 2017

R. Soc. open sci.

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The flexibility window in zeolites was originally identified using geometric simulation as a hypothetical property of SiO2 systems. The existence of the flexibility window in hypothetical structures may help us to identify those we might be able to synthesize in the future. We have previously found that the flexibility window in silicates is connected to phase transitions under pressure, structure amorphization and other physical behaviours and phenomena. We here extend the concept to ordered aluminosilicate systems using softer ‘bar’ constraints that permit additional flexibility around aluminium centres. Our experimental investigation of pressure-induced amorphization in sodalites is consistent with the results of our modelling. The softer constraints allow us to identify a flexibility window in the anomalous case of goosecreekite.

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Section: Resultsmentioning

confidence: 99%

Defining the flexibility window in ordered aluminosilicate zeolites

Wells

Leung²,

Edwards³

et al. 2017

R. Soc. open sci.

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show abstract

“…After the modifications made to the catalysts, there was no significant shift in the Q 3 signals around −102 ppm, which refers to Si (1Al, 3Si or SiOH) in different environments and neither in Q 4 (around −111 and −115 ppm, which can be associated with the Si (0Al) environment. Zeolite *BEA presented nine different crystallographic sites [ 37 ], which can cause different chemical shifts to the same Si (nAl) environment [ 28 , 34 , 38 ]. The major modification of Q n distribution was from HB to DB, with the decreased amount of Q 3 .…”

Section: Resultsmentioning

confidence: 99%

Niobium on BEA Dealuminated Zeolite for High Selectivity Dehydration Reactions of Ethanol and Xylose into Diethyl Ether and Furfural

et al. 2020

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In this work, we investigated the role of solid-state dealumination by (NH4)2SiF6 (25% Al removal and 13% Si insertion), the impregnation of niobium (10, 18, and 25 wt. %) on dealuminated *BEA (DB) zeolite and their catalytic properties in ethanol and xylose transformations. Among all the studied catalysts, 18%Nb-DB showed increased mesoporosity and external areas. A leveling effect in the number and strength of the proposed two sites (Brønsted and Lewis) present in the catalyst (n1 = 0.24 mmol g−1, −ΔH1 = 49 kJ mol−1, and n2 = 0.20 mmol g−1, –ΔH2 = 42 kJ mol−1) in the catalyst 18%Nb-DB, might be responsible for its good activity. This catalyst presented the highest selectivity for diethyl ether, DEE (97%) with 61% conversion after 50 ethanol pulses at 230 °C (turnover number, TON DEE = 1.15). These features allowed catalytically fruitful bonding of the ethanol molecules to the neighboring sites on the channels, facilitating bimolecular ether formation through a possible SN2 mechanism. The same catalyst was active and selective for transformation of xylose at 180 °C, showing 64% conversion and 51% selectivity for furfural (TON Furfural = 24.7) using water as a green solvent.

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“…Mordenite (three-letter code MOR for framework type) can be used, in particular, as a sorbent for wastewater treatment. , Yet, the most important application of this structure is industrial catalysis: hydro-isomerization of light naphtha (C5–C6 paraffins) and aromatic processing (e.g., cumene production, ethylbenzene isomerization, toluene disproportionation) …”

Section: Introductionmentioning

confidence: 99%

Ultrasonic Pretreatment as a Tool for the Preparation of Low-Defect Zeolite Mordenite

et al. 2021

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The effects of the ultrasonic (US) pretreatment of synthesis gel for the preparation of mordenite zeolite were studied in comparison with the classical stirring method. Even though the US pretreatment was performed before the hydrothermal crystallization, it significantly affected the properties of the obtained mordenite crystals. The US-assisted procedure resulted in a material with improved textural characteristics, in particular, the micropore volume accessible for nitrogen molecules in the as-made form. On the other hand, mordenite prepared with the classical stirring method demonstrated comparable sorption properties only after a postsynthetic treatment. Moreover, in the case of US-pretreated mordenite, altered crystal shape and more homogeneous morphology were observed. 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR) demonstrated that the US pretreatment introduced structural changes on the atomic level, resulting in fewer defects (reflected in the number of silanol groups) and less pore blockage (affected by Na+ cations) for the as-made sample.

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Aei

Cited by 262 publications

References 1 publication

Defining the flexibility window in ordered aluminosilicate zeolites

Defining the flexibility window in ordered aluminosilicate zeolites

Niobium on BEA Dealuminated Zeolite for High Selectivity Dehydration Reactions of Ethanol and Xylose into Diethyl Ether and Furfural

Ultrasonic Pretreatment as a Tool for the Preparation of Low-Defect Zeolite Mordenite

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