Catalytic properties of synthetic mordenite in the isomerization, hydrogenation, and hydroisomerization of certain hydrocarbons

Миначев, Х. М.; Garanin, V. I.; Харламов, В. В.; Isakova, T. A.; Senderov, É. É.

doi:10.1007/bf00906391

Cited by 7 publications

(8 citation statements)

References 6 publications

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“…To address the pressing question of the Lewis acidityaluminum structure relationship, we turned to MOR zeolites. Mordenite is widely used as a heterogeneous catalyst and support in extensively researched reactions, such as hydroisomerization of hydrocarbons, 30 methane to methanol, 31 and selective catalytic reduction. 32 Five MOR zeolite samples, with different Si/Al ratios given in brackets, were used in this study.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Lewis Acidity Inherent to the Framework of Zeolite Mordenite

2019

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Despite being used extensively as heterogeneous catalysts and supports at the academic and industrial levels alike, the nature of aluminum-based Lewis acidity in zeolites is not completely understood. In this study, we discovered a correlation between Lewis acidity and aluminum structure in the framework of zeolite mordenite. The amount of octahedrally coordinated aluminum in these samples present under wet conditions correlates to the number of Lewis acid sites as detected by Fourier-transform infrared spectroscopy of adsorbed probe molecules in the fully dehydrated state. We illustrate that these aluminum species, which are better considered as framework-associated and not extra-framework aluminum, have Lewis acidic properties when treated under vacuum at high temperature. This observation constitutes important progress in understanding the structure of Lewis acid sites. The Lewis acid sites are framework aluminum species which undergo a change in coordination, from tetrahedral to octahedral, depending on the charge-balancing cation and degree of hydration. These Lewis acid sites exist in the case of charge balancing by protons.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Lewis Acidity Inherent to the Framework of Zeolite Mordenite

2019

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“…4 Protonic zeolites are extensively used for several reactions, in particular, cracking, alkylation, and isomerization. [5][6][7] Apart from Brønsted acid sites, certain aluminum species in zeolites possess Lewis acidic character. Lewis acidic aluminum (Figure 1b) plays a pivotal role not only in traditional cracking reactions, but also in salient biomass valorization reactions, 8,9 which include the conversion of trioses to alkyl lactates, 10 and cellulose to glucose.…”

Section: Introductionmentioning

confidence: 99%

On the location of Lewis acidic aluminum in zeolite mordenite and the role of framework-associated aluminum in mediating the switch between Brønsted and Lewis acidity

2021

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“…Among many metals, rhenium is known for its ability to catalyze hydrogenolysis of heteroatomic X–C bonds − and as a selective hydrogenation catalyst. − It is also able to promote reactions involving C–C and aromatic C–H cleavages . Another remarkable property of rhenium oxide is its ability to reduce selectively carboxyl groups without affecting the aromatic ring …”

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confidence: 99%

“…As mentioned above, rhenium is typically used in concert with a second noble metal such as ruthenium, platinum, and palladium, both deposited over a proper support (carbon, silica, and alumina). Rhenium promotes platinum/carbon catalysts for glycerol conversion, which suggests that its presence facilitates hydrogenolysis of the C–O bonds due to its ability to preferentially bond hydroxyl groups. , Then, these species will react in the second step with hydrogen dissociatively adsorbed and activated on the second noble metal, , resulting in an enhancement of the activity and selectivity . The Lewis acid effect exerted by rhenium in the hydrogenolys of oxygenated compounds has also been demonstrated by the enhancement induced in the selectivity of the bimetallic rhenium–ruthenium catalyst …”

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Lignin Fragmentation onto Multifunctional Fe₃O₄@Nb₂O₅@Co@Re Catalysts: The Role of the Composition and Deposition Route of Rhenium

et al. 2017

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Multifunctional Fe3O4@Nb2O5@Co@Re catalysts with metal loadings in the range of 2–7 wt % were prepared via a multistep process. Magnetic nanoparticles prepared by coprecipitation were covered with a niobia shell precipitated from an ammonium niobate–oxalate complex in the presence of hexadecyltrimethylammonium bromide. The deposition of cobalt was performed using a deposition/precipitation procedure. Finally, rhenium has been deposited following three different routes: (i) impregnation, (ii) deposition and precipitation of rhenium chloride (ImC and PP, respectively), and (iii) impregnation with ammonium perrhenate (ImA). The characterization of these catalysts was achieved by X-ray diffraction, Raman, H2 and NH3 temperature-programmed desorption, X-ray photoelectron spectroscopy, and transmission electron microscopy showing the influence of the preparation procedure, reduction, and Re/Co cooperation on the degree of dispersion and reduction. ImC and ImA routes led to more reduced catalysts, and the decrease in cobalt content corresponded to more reduced rhenium. An inverse relation between the acidity and the degree of reduction has been found. The screening of these catalysts in the fragmentation of the lignin confirmed the role of the structural characteristics and solvent. ImC catalysts exhibited better catalytic activity, especially for low metal loadings [2%Co@3%Re, 85% yield of LF, 15.5% yield of LR in tetrahydrofuran (THF), and 14.5% yield of insoluble LR in THF]. Although the extent was smaller, the PP catalysts allowed a more advanced fragmentation of the lignin to fragments with molecular weights between 200 and 400 Da. The catalysts were totally recovered by application of a magnetic field and recycled six times without any loss of activity or selectivity.

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Catalytic properties of synthetic mordenite in the isomerization, hydrogenation, and hydroisomerization of certain hydrocarbons

Cited by 7 publications

References 6 publications

Lewis Acidity Inherent to the Framework of Zeolite Mordenite

Lewis Acidity Inherent to the Framework of Zeolite Mordenite

On the location of Lewis acidic aluminum in zeolite mordenite and the role of framework-associated aluminum in mediating the switch between Brønsted and Lewis acidity

Lignin Fragmentation onto Multifunctional Fe₃O₄@Nb₂O₅@Co@Re Catalysts: The Role of the Composition and Deposition Route of Rhenium

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Catalytic properties of synthetic mordenite in the isomerization, hydrogenation, and hydroisomerization of certain hydrocarbons

Cited by 7 publications

References 6 publications

Lewis Acidity Inherent to the Framework of Zeolite Mordenite

Lewis Acidity Inherent to the Framework of Zeolite Mordenite

On the location of Lewis acidic aluminum in zeolite mordenite and the role of framework-associated aluminum in mediating the switch between Brønsted and Lewis acidity

Lignin Fragmentation onto Multifunctional Fe3O4@Nb2O5@Co@Re Catalysts: The Role of the Composition and Deposition Route of Rhenium

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Lignin Fragmentation onto Multifunctional Fe₃O₄@Nb₂O₅@Co@Re Catalysts: The Role of the Composition and Deposition Route of Rhenium