Textural and catalytic properties of Mo loaded hierarchical meso-/microporous lamellar MFI and MWW zeolites for direct methane conversion

Wu, Yiqing; Emdadi, Laleh; Wang, Zhuopeng; Fan, Wei; Liu, Dongxia

doi:10.1016/j.apcata.2013.10.053

Cited by 47 publications

(34 citation statements)

References 75 publications

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“…The mesh prevented the spill of the sample and allowed access to the Si-or Al-precursor vapor in the ALD process. The ALD-Si was carried out by alternative exposure of zeolite sample to tris(dimethylamino)silane (TDMAS, [45,46]. The same setup was used for the following organic base titration and gas-phase catalytic reaction studies.…”

Section: Ald Modification Of Pmww and Pmfi Zeolitesmentioning

confidence: 99%

Tuning external surface of unit-cell thick pillared MFI and MWW zeolites by atomic layer deposition and its consequences on acid-catalyzed reactions

Lü

Emdadi

et al. 2016

Journal of Catalysis

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The pillared MWW (PMWW or MCM-36) and pillared MFI (PMFI) zeolites are 2dimensional (2D) catalytically active materials made by pillaring of layered MCM-22(P) and multilamellar MFI precursors, respectively. The single-or near single-unit-cell thick 2D microporous layers in PMWW and PMFI expose comparable number of external surface acid sites (i.e., acid sites enclosed in mesopores between zeolitic layers) to those in micropores, which become important or dominant contributor to the catalytic properties. Although the acidity and catalytic activities of PMWW and PMFI have been studied, modification of their external surfaces and its implications on catalytic reactions are not available. In the present study, we report the tailoring of external surfaces of PMWW and PMFI zeolites by atomic layer deposition (ALD) of silicon (ALD-Si) and aluminum (ALD-Al), respectively. The textural, acidic and catalytic properties of the ALD modified pillared zeolites were investigated using a variety of characterization methods. ALD-Al and ALD-Si modifications kept micropore almost intact, but resulted in significant reduction in mesopore volume and considerable changes in external surface composition and acidity. The catalytic tests showed that intrinsic catalytic behavior of Brønsted acid sites in ALD modified pillared zeolites was similar to their parent counterparts. In diffusion constrained parallel reactions, ALD of Al-or Si-species altered catalyst selectivity. In addition, ALD of Si-species on PMFI zeolite deactivated surface active sites, which resulted in improved catalytic activity in direct methane aromatization reactions under optimal ALD cycles. The study exemplified for the first time that ALD is an effective tool for tuning the surface properties of 2D unit-cell thick zeolites.

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Section: Ald Modification Of Pmww and Pmfi Zeolitesmentioning

confidence: 99%

Tuning external surface of unit-cell thick pillared MFI and MWW zeolites by atomic layer deposition and its consequences on acid-catalyzed reactions

Lü

Emdadi

et al. 2016

Journal of Catalysis

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“…Therefore, they enable beneficial effects on adsorption and reaction in processing bulky molecules. There are many reports about enhanced performance that can be achieved in catalysis when using 2D zeolite materials, especially for delaminated and pillared zeolite materials [36][37][38][39][40][41][42]. Overviews of 2D zeolites in catalysis have been published by J.Čejka [6,9,43] and J.…”

Section: Introductionmentioning

confidence: 99%

Two-Dimensional Zeolite Materials: Structural and Acidity Properties

Schulman

Liu

2020

Materials

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Zeolites are generally defined as three-dimensional (3D) crystalline microporous aluminosilicates in which silicon (Si4+) and aluminum (Al3+) are coordinated tetrahedrally with oxygen to form large negative lattices and consequent Brønsted acidity. Two-dimensional (2D) zeolite nanosheets with single-unit-cell or near single-unit-cell thickness (~2–3 nm) represent an emerging type of zeolite material. The extremely thin slices of crystals in 2D zeolites produce high external surface areas (up to 50% of total surface area compared to ~2% in micron-sized 3D zeolite) and expose most of their active sites on external surfaces, enabling beneficial effects for the adsorption and reaction performance for processing bulky molecules. This review summarizes the structural properties of 2D layered precursors and 2D zeolite derivatives, as well as the acidity properties of 2D zeolite derivative structures, especially in connection to their 3D conventional zeolite analogues’ structural and compositional properties. The timeline of the synthesis and recognition of 2D zeolites, as well as the structure and composition properties of each 2D zeolite, are discussed initially. The qualitative and quantitative measurements on the acid site type, strength, and accessibility of 2D zeolites are then presented. Future research and development directions to advance understanding of 2D zeolite materials are also discussed.

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“…[1][2][3][4][5][6][7][8][9][10][11][12] However, industrialization of this reaction encounters a serious bottleneck of rapid deactivation of the catalyst due to coking. [32][33][34][35] Nevertheless, no catalyst has been found to have a sufficiently long lifetime to meet the requirement of a longterm run at industrially required conditions. [32][33][34][35] Nevertheless, no catalyst has been found to have a sufficiently long lifetime to meet the requirement of a longterm run at industrially required conditions.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Fe additive improving the activity stability of microzeolite-based Mo/HZSM-5 catalyst in non-oxidative methane dehydroaromatization at 1073 K under periodic CH₄–H₂switching modes

Song

Suzuki

et al. 2014

Catal. Sci. Technol.

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ARTICLE This journal isThe catalytic stabilities of Fe-modified and -unmodified 5%Mo/HZSM-5 catalysts in the non-oxidative methane dehydroaromatization were compared at 1073 K and three reaction/H 2 -regeneration cycle periods: 5 min CH 4 -5 min H 2 , 5 min CH 4 -10 min H 2 , and 5 min CH 4 -20 min H 2 . Fe addition proved capable of remarkably increasing the catalyst stability over the cycles of 5 min CH 4 -20 min H 2 but hardly effective over the cycles of 5 min CH 4 -5 min H 2 . On the other hand, SEM observation of all spent samples revealed that Fe addition causes a massive accumulation of carbon nanotubes under the latter cyclic condition but little at the former. Thus several sets of comparative tests were specially designed and performed to get insight into the rule of Fe-catalyzed cyclic formation of carbon nanotubes in stabilizing the activity at the cyclic condition of 5 min CH 4 -20 min H 2 . The results further confirmed that at this condition cyclic formation of carbon nanotubes enhances cyclic evolution of H 2 and makes the H 2 concentration of the system higher, which is thermodynamically beneficial for suppression of formation of the activity-deactivating surface coke. Finally, it was further confirmed that at least a 20 min H 2 exposure is required to remove most of the carbon nanotubes and surface coke formed during a 5 min CH 4 exposure and make most of Fe nanoparticles reactivated and available again for catalytic carbon nanotubes formation with an enhanced H 2 evolution, i.e., with a controlled formation of the surface coke in the next CH 4 exposure.

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Textural and catalytic properties of Mo loaded hierarchical meso-/microporous lamellar MFI and MWW zeolites for direct methane conversion

Cited by 47 publications

References 75 publications

Tuning external surface of unit-cell thick pillared MFI and MWW zeolites by atomic layer deposition and its consequences on acid-catalyzed reactions

Tuning external surface of unit-cell thick pillared MFI and MWW zeolites by atomic layer deposition and its consequences on acid-catalyzed reactions

Two-Dimensional Zeolite Materials: Structural and Acidity Properties

Mechanism of Fe additive improving the activity stability of microzeolite-based Mo/HZSM-5 catalyst in non-oxidative methane dehydroaromatization at 1073 K under periodic CH₄–H₂switching modes

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Textural and catalytic properties of Mo loaded hierarchical meso-/microporous lamellar MFI and MWW zeolites for direct methane conversion

Cited by 47 publications

References 75 publications

Tuning external surface of unit-cell thick pillared MFI and MWW zeolites by atomic layer deposition and its consequences on acid-catalyzed reactions

Tuning external surface of unit-cell thick pillared MFI and MWW zeolites by atomic layer deposition and its consequences on acid-catalyzed reactions

Two-Dimensional Zeolite Materials: Structural and Acidity Properties

Mechanism of Fe additive improving the activity stability of microzeolite-based Mo/HZSM-5 catalyst in non-oxidative methane dehydroaromatization at 1073 K under periodic CH4–H2switching modes

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Mechanism of Fe additive improving the activity stability of microzeolite-based Mo/HZSM-5 catalyst in non-oxidative methane dehydroaromatization at 1073 K under periodic CH₄–H₂switching modes