Transformation of ethylbenzene-m-xylene feed over MCM-22 zeolites with different acidities

Mihályi, Magdolna R.; Kollár, Márton; Klébert, Szilvia; Mavrodinova, V.

doi:10.1016/j.apcata.2014.02.004

Cited by 11 publications

(6 citation statements)

References 29 publications

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“…As a result, a decrease in the acid strength is of benefit to suppressing the accumulation of aromatics, especially the larger polycyclic ones, and then improving the catalytic stability of H-MCM-22 in MTO. This is also supported by the recent experimental observation of Mihalyi and co-workers; 84 for the transformation of ethylbenzene and m-xylene over H-MCM-22 zeolites with different acidities, they found that the catalytic stability of H-MCM-22 can be enhanced by decreasing its acidity through isomorphous substitution of framework Al with B.…”

Section: Reactivity Of Polymnsupporting

confidence: 83%

Evolution of Aromatic Species in Supercages and Its Effect on the Conversion of Methanol to Olefins over H-MCM-22 Zeolite: A Density Functional Theory Study

et al. 2016

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H-MCM-22 zeolite is a potential catalyst for the conversion of methanol to olefins (MTO). Previous studies indicated that three types of pores in H-MCM-22, viz., the supercages, sinusoidal channels, and pockets, are different in their catalytic action; however, the evolution of aromatic species in the supercages and its effect on MTO are still highly controversial. In this work, density functional theory considering dispersive interactions (DFT-D) was used to investigate the evolution of aromatic species including their formation, reactivity, and deactivation behavior in the supercages; the active role of the supercages in catalyzing MTO was elucidated. The results demonstrated that benzene can be generated in the supercages through aromatization of light olefins; after that, polymethylbenzenes (polyMBs) are formed through methylations, in competition with the construction of naphthalenic species. Both polyMBs (e.g., hexamethylbenzene) and polymethylnaphthalenes (polyMNs, e.g. dimethylnaphthalene) exhibit high reactivity as the hydrocarbon pool species in forming light olefins. Owing to the appropriate electrostatic stabilization and space confinement effects, naphthalenic species in the supercages are inclined to serve as the active intermediates to produce light olefins rather than act as the coke precursors in the initial period of MTO; as a result, the supercages contribute actively to the initial activity of H-MCM-22 in MTO, though they may be prone to deactivation in the later reaction stage in comparison with the sinusoidal channels. The insights shown in this work help to clarify the evolution of aromatic species and the active role of the supercages in MTO over H-MCM-22, which is of benefit to the development of better MTO catalysts and reaction processes.

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Section: Reactivity Of Polymnsupporting

confidence: 83%

Evolution of Aromatic Species in Supercages and Its Effect on the Conversion of Methanol to Olefins over H-MCM-22 Zeolite: A Density Functional Theory Study

et al. 2016

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“…Both samples presented a peak at 3782 cm –1 confirming the presence of EFAl, , which are known to be very strong Lewis acid sites . However, BEA38 presented a larger peak which is consistent with the peaks at 3656 and 3743 cm –1 indicating aluminic species in extraframework positions and SiOH on external surface, respectively. , The aforementioned (EFAl sites) is probably due to the presence of water during calcination of the solid leading to dealumination and therefore higher concentration of Lewis acid sites; more EFAl sites in BEA38 can also be verified by the slightly larger contribution of peak h2 in Table S2. The appearance of said peak depends on the whole procedure of synthesis. , As expected, BEA35 exhibited the largest peak at 3606 cm –1 which corresponds to acid bridging Si–OH–Al groups (Brønsted acid sites). ,, …”

Section: Resultssupporting

confidence: 69%

“…25 However, BEA38 presented a larger peak which is consistent with the peaks at 3656 and 3743 cm −1 indicating aluminic species in extraframework positions and SiOH on external surface, respectively. 30,31 The aforementioned (EFAl sites) is probably due to the presence of water during calcination of the solid leading to dealumination and therefore higher concentration of Lewis acid sites; more EFAl sites in BEA38 can also be verified by the slightly larger contribution of peak h2 in Table S2. The appearance of said peak depends on the whole procedure of synthesis.…”

Section: Resultsmentioning

confidence: 91%

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Xylene Isomerization over Beta Zeolites in Liquid Phase

Shi

Gonçalves

Ferreira

et al. 2018

Ind. Eng. Chem. Res.

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An experimental study of xylene isomers interconversion (isomerization) kinetics was conducted to gain a deeper insight into the field. Two beta zeolites with SiO2/Al2O3 ratio of 35 (BEA35) and 38 (BEA38) were used as catalysts for the performed experiments. The isomerization reactions were carried out under the following conditions: 513, 493, 473, and 453 K at 2.1 MPa in liquid phase. It was verified that all reactions were in the kinetic-controlled regime. Kinetic constants were estimated with four different models; two of them were based on the xylene isomerization thermodynamic equilibrium from the literature. The linear reaction scheme, which does not consider the direct conversion between p- and o-xylene, presented a better fit to the experimental values. Higher conversion of p-xylene was observed when compared with the conversion of the other two isomers. This may be attributed to its smaller molecular size. BEA35 presented better performance due to its higher amount of Brønsted acid sites. Finally, activation energies over the two catalysts, estimated through Arrhenius equation, presented similar values.

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“…For the catalysts based on zeolites as supports and gold NPs as the main active centers it is relatively easy to determine the structure and type of active sites (e.g., Brønsted acid sites (BAS) in zeolites). Moreover, zeolites can be easily modified by isomorphous substitution in their skeleton (e.g., by incorporation of boron instead of aluminum in the aluminosilica framework [10,11]) or by post-synthesis modification (e.g., by functionalization of the zeolite surface with amino-organosilanes [12,13]). Changes in the zeolite composition imply changes in the surface (acid-base) properties and thus modify the interaction between the support and gold NPs.…”

Section: Introductionmentioning

confidence: 99%

Modification of Gold Zeolitic Supports for Catalytic Oxidation of Glucose to Gluconic Acid

et al. 2021

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Activity of gold supported catalysts strongly depends on the type and composition of support, which determine the size of Au nanoparticles (Au NPs), gold-support interaction influencing gold properties, interaction with the reactants and, in this way, the reaction pathway. The aim of this study was to use two types of zeolites: the three dimensional HBeta and the layered two-dimensional MCM-36 as supports for gold, and modification of their properties towards the achievement of different properties in oxidation of glucose to gluconic acid with molecular oxygen and hydrogen peroxide. Such an approach allowed establishment of relationships between the activity of gold catalysts and different parameters such as Au NPs size, electronic properties of gold, structure and acidity of the supports. The zeolites were modified with (3-aminopropyl)-trimethoxysilane (APMS), which affected the support features and Au NPs properties. Moreover, the modification of the zeolite lattice with boron was applied to change the strength of the zeolite acidity. All modifications resulted in changes in glucose conversion, while maintaining high selectivity to gluconic acid. The most important findings include the differences in the reaction steps limiting the reaction rate depending on the nature of the oxidant applied (oxygen vs. H2O2), the important role of porosity of the zeolite supports, and accumulation of negative charge on Au NPs in catalytic oxidation of glucose.

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Transformation of ethylbenzene-m-xylene feed over MCM-22 zeolites with different acidities

Cited by 11 publications

References 29 publications

Evolution of Aromatic Species in Supercages and Its Effect on the Conversion of Methanol to Olefins over H-MCM-22 Zeolite: A Density Functional Theory Study

Evolution of Aromatic Species in Supercages and Its Effect on the Conversion of Methanol to Olefins over H-MCM-22 Zeolite: A Density Functional Theory Study

Xylene Isomerization over Beta Zeolites in Liquid Phase

Modification of Gold Zeolitic Supports for Catalytic Oxidation of Glucose to Gluconic Acid

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