Effect of selective 4-membered ring dealumination on mordenite-catalyzed dimethyl ether carbonylation

Reule, Allen A.C.; Sawada, James A.; Semagina, Natalia

doi:10.1016/j.jcat.2017.03.010

Cited by 67 publications

(53 citation statements)

References 76 publications

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“…Indeed, the modification of micropore size distribution of mordenite upon acid leaching has been observed by several groups. [11][12] It is to note that for PyF samples analog micropore filling is observed as for the parent M10, indicating that the pyridine treatment does not enlarge 8-…”

Section: Influence Of the Hf Etching On The Physicochemical Propertiementioning

confidence: 95%

“…[11] Semagina and co-workers furthermore evidenced that despite of loss of crystallinity microporosity increases, due to selective removal of Al form T3 and T4 sites through acid treatment. [12] The development of microporosity upon dealumination has further been evidenced through computational simulations. [13] Among the various dealumination strategies the etching of zeolites through aqueous HF solutions has firstly been described by Ghosh and Kydd.…”

Section: Introductionmentioning

confidence: 98%

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Mordenite etching in pyridine: Textural and chemical properties rationalized by toluene disproportionation and n-hexane cracking

Issa

Toufaily

Hamieh

et al. 2019

Journal of Catalysis

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Chemical etching with hydrofluoric acid in pyridine medium has been developed as efficient strategy for the crystal engineering of mordenite zeolites. Contrary to the HF etching in aqueous medium, the etching in pyridine allows to preserves the global composition and acidity of parent mordenites. Zeolites etched in pyridine have a similar distribution of Brønsted acid sites (BAS) as the parent, i.e. 16% in 8-MR channels, 19% at the intersection between side pockets and 12MR channels and 65% in the 12-MR channels. Etching in aqueous HF failed to preserve BAS distribution due to strong dealumination, which further leads to enlargement of side pockets. Mordenites etched with HF in pyridine allow for superior catalytic performance in both n-hexane cracking and toluene disproportionation. It has been evidenced that only the BAS located in the 8-MR side pockets prove active for the toluene disproportionation at 450 °C, while for n-hexane cracking at 541°C BAS in both 12-MR channels and 8-MRs pockets catalyze the reaction, yet BAS in side pockets are more active (1.5 times). Moreover, Lewis acid sites generated during the post-synthetic treatments exalt the strength of the active sites, which multiplies TOFs of the active sites by two.

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Section: Influence Of the Hf Etching On The Physicochemical Propertiementioning

confidence: 95%

Section: Introductionmentioning

confidence: 98%

Mordenite etching in pyridine: Textural and chemical properties rationalized by toluene disproportionation and n-hexane cracking

Issa

Toufaily

Hamieh

et al. 2019

Journal of Catalysis

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“…No copper or zinc ions were brought into the framework T sites maintaining the original Si/Al ratio. The calcined samples were characterized, as we described previously, by energy‐dispersive X‐ray spectroscopy, Ar physisorption, DRIFTS, TEM, and TPR . XPS analyses were performed on the calcined samples before and after DME carbonylation using a Kratos Analytical AXIS‐165 spectrometer.…”

Section: Methodsmentioning

confidence: 99%

Copper Affects the Location of Zinc in Bimetallic Ion‐Exchanged Mordenite

2018

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Bimetallic ion exchange on a zeolite often impacts its catalytic properties compared to its monometallic counterparts. Here, we address the synergistic effect of simultaneous copper and zinc ion exchange on mordenite (MOR), as found earlier for dimethyl ether (DME) carbonylation. Samples with various Cu/Zn ratios were characterized by diffuse-reflectance infrared Fourier-transform spectroscopy (DRIFTS) in the 3600 and 720 cm regions, pore distribution analysis through Ar physisorption, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), and transmission electron microscopy (TEM). When ion-exchanged alone, copper preferentially occupies 12-membered rings, whereas zinc occupies 8-membered rings. In bimetallic combinations, the zinc addition was found to prevent the copper from sintering into nanoparticles and to increase its coordination strength to the zeolite. At a Cu/Zn ratio of 0.25 (for MOR with Si/Al=6.5), copper promotes zinc ion exchange into 12-membered rings, more specifically, into T4 sites that are known for the formation of the coke precursor in DME carbonylation on a MOR. The sites became blocked during the bimetallic ion exchange, leading to suppressed catalyst deactivation. The study contributes to the understanding of mutual ion effects in bimetallic exchanged zeolites and highlights the major role of copper as a governing factor in determining the location of co-exchanged zinc on a MOR.

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“…[255] Several other groups used HNO 3 as well in the acid treatment of mordenites. [254,[256][257][258] In a study from Reule et al, the concentration of the HNO 3 solution, as well as the treatment temperature, was varied in order to study the effect on dealumination. [257] Both a higher HNO 3 concentration and a higher temperature resulted in an increase of external surface area, pore volume, and average pore size.…”

Section: Mordenitementioning

confidence: 99%

“…The treated mordenites were subsequently tested in the DME carbonylation to methylacetate. [257] Next to HNO 3 that was used in previous studies, there exist other mineral acids that can be employed as well for the dealumination of mordenites, such as HF [259,260] and NH 4 F, [259] but also organic acids like oxalic acid [255] and citric acid [261] can be used. However, the effect of these acids on for instance the increase in mesopore volume was not as pronounced as was the case with HNO 3 .…”

Section: Mordenitementioning

confidence: 99%

State of the Art and Perspectives of Hierarchical Zeolites: Practical Overview of Synthesis Methods and Use in Catalysis

et al. 2020

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Zeolites are highly crystalline aluminosilicates with welldefined pores that are constructed of SiO 2 and AlO 4 tetrahedra. These tetrahedra can be linked together in different unique ways to form various materials with a specific topology. [1] According to the International Zeolite Association (IZA), more than 250 different topologies, which are all assigned with a three-letter code, have been identified. [2] The micropores in zeolites are typically constructed from 8, 10, or 12 tetrahedral atoms

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Effect of selective 4-membered ring dealumination on mordenite-catalyzed dimethyl ether carbonylation

Cited by 67 publications

References 76 publications

Mordenite etching in pyridine: Textural and chemical properties rationalized by toluene disproportionation and n-hexane cracking

Mordenite etching in pyridine: Textural and chemical properties rationalized by toluene disproportionation and n-hexane cracking

Copper Affects the Location of Zinc in Bimetallic Ion‐Exchanged Mordenite

State of the Art and Perspectives of Hierarchical Zeolites: Practical Overview of Synthesis Methods and Use in Catalysis

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