The Propylene Oxide Rearrangement Catalyzed by the Lewis Acid Sites of ZSM-5 Catalyst with Controllable Surface Acidity

Liang, Mengnan; Zhu, Xiangshuai; Ma, Wenhui

doi:10.1007/s10562-019-02687-w

Cited by 17 publications

(12 citation statements)

References 38 publications

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“…Upon heating to 573 K, apparent IR bands at 1700–1600 cm –1 with a pair of weak IR bands at 2815 and 2715 cm –1 gradually emerged with a flow of the mixture of C 3 H 6 –O 2 (Figures a and S20); the same results were observed upon PO adsorption at 323 K (Figure S21). These bands could be attributed to the transition states between C  O and C–O (bands at 1700–1600 cm –1 due to C–O stretching, bands at 2815/2715 cm –1 due to C–H stretching split by Fermi resonance, Table S3), namely, C--O of intermediates for epoxidation reaction. − It is worth noting that such bands could be observed on Co@Y with the successive feeding of O 2 and C 3 H 6 (Figure b), while they were absent with an inversed feeding sequence (Figure c). With further heating to 673 K, strong IR bands at 1320–1230 cm –1 due to C–O–C asymmetric stretching vibrations of epoxide appeared (Figures d and S20), which is in accordance with the mass formation of PO at 673 K (Figure a). − Similarly, the formation of adsorbed PO relies on the feeding sequence of propylene and O 2 (Figure e,f).…”

Section: Resultssupporting

confidence: 67%

Direct Propylene Epoxidation with Molecular Oxygen over Cobalt-Containing Zeolites

et al. 2022

J. Am. Chem. Soc.

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Direct propylene epoxidation with molecular oxygen is a dream reaction with 100% atom economy, but aerobic epoxidation is challenging because of the undesired over-oxidation and isomerization of epoxide products. Herein, we report the construction of uniform cobalt ions confined in faujasite zeolite, namely, Co@Y, which exhibits unprecedented catalytic performance in the aerobic epoxidation of propylene. Propylene conversion of 24.6% is achieved at propylene oxide selectivity of 57% at 773 K, giving a state-of-the-art propylene oxide production rate of 4.7 mmol/gcat/h. The catalytic performance of Co@Y is very stable, and no activity loss can be observed for over 200 h. Spectroscopic analyses reveal the details of molecular oxygen activation on isolated cobalt ions, followed by interaction with propylene to produce epoxide, in which the Co2+–Coδ+–Co2+ (2 < δ < 3) redox cycle is involved. The reaction pathway of propylene oxide and byproduct acrolein formation from propylene epoxidation is investigated by density functional theory calculations, and the unique catalytic performance of Co@Y is interpreted. This work presents an explicit example of constructing specific transition-metal ions within the zeolite matrix toward selective catalytic oxidations.

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Section: Resultssupporting

confidence: 67%

Direct Propylene Epoxidation with Molecular Oxygen over Cobalt-Containing Zeolites

et al. 2022

J. Am. Chem. Soc.

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“…The ethyl carbocation balances the charge of the zeolite to keep the reaction system electrically neutral. Liang et al [29] also found that the skeleton aluminum atom can change from tri-coordination to tetra-coordination with the catalytic cracking of propylene oxide on a Lewis acid. The intermediate Int1 readily undergoes a hydrogen transfer reaction.…”

Section: Cracking Of β-C-c Bondmentioning

confidence: 99%

A DFT Study for Catalytic Deoxygenation of Methyl Butyrate on a Lewis Acid Site of ZSM-5 Zeolite

Chen

Liu

et al. 2020

Catalysts

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The catalytic deoxygenation mechanism of fatty acid esters on a Lewis acid site of ZSM-5 zeolite was elucidated via density functional theory (DFT) by using a methyl butyrate (MB) as the model compound for fatty acid esters. The configurations of the initial reactant, transition states, and products together with the activation barrier of each elementary reaction were determined. The activation barrier of different initial cracking reactions decreases in the order of α-C–C > β-C–C > α-C–O > β-C–O. The best reaction path for catalytic deoxygenation of methyl butyrate over Lewis acid site is CH3CH2CH2C(OCH3)=O⋯Lewis → CH3CH2⋯Lewis⋯C(=CH2)OCH3 → CH2=CH2 + CH3COOCH3 + Lewis. The oxygen of methyl butyrate is mainly removed as CO2, methyl acetate, formaldehyde, and butyraldehyde, while ethylene, propylene, and butane are the main hydrocarbon products. In addition, the group generated by cracking of methyl butyrate form a bond with the Lewis acid site, promoting the transformation between a Lewis acid and a Brønsted acid. The corresponding intermediates have a high single point energy, but the poor stability leads to further deoxygenation and cracking reactions. This work provides a theoretical basis for the modification in the number of Brønsted acid and Lewis acid sites in the ZSM-5 zeolite.

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“…Typical examples here are aluminas and aluminosilicates. − It is also common to create additional Lewis-acid sites on crystalline zeolites via substitutional exchange of some of the original cations with elements such as Mg, Ti, Zr, V, Nb, Ta, Mo, Ga, Sn, and other metal ions. − The acidity of those sites is centered at the metal ion, which can be found in a variety of environments on the surface, surrounded by structurally different ensembles of oxygen atoms. , For this reason, Lewis-acid sites in oxides may be less well-defined than their Brønsted counterparts. Nevertheless, they are capable of promoting a number of complex reactions selectively, especially in applications where hydrocarbon conversions are central such as in oil refining and the processing of biofuels and chemicals. − For instance, in aluminosilicates, the Busca research group established that Lewis-acid sites with alumina-like acid–base neighbors are more selective for the promotion of the dehydrogenation of ethanol to ethylene, whereas Lewis-acid sites with silica-like covalent neighbors catalyze the production of diethyl ether instead. , In another example, operando time-resolved IR spectroscopy was used to determine that in the selective catalytic reduction (SCR) of nitric oxide, the key step is a reaction with ammonia coordinated to the vanadia Lewis-acid sites present on vanadia-tungsta-titania mixed oxides (Figure ). …”

Section: Single-site Catalysismentioning

confidence: 99%

Designing Sites in Heterogeneous Catalysis: Are We Reaching Selectivities Competitive With Those of Homogeneous Catalysts?

Zaera

2022

Chem. Rev.

163

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A critical review of different prominent nanotechnologies adapted to catalysis is provided, with focus on how they contribute to the improvement of selectivity in heterogeneous catalysis. Ways to modify catalytic sites range from the use of the reversible or irreversible adsorption of molecular modifiers to the immobilization or tethering of homogeneous catalysts and the development of well-defined catalytic sites on solid surfaces. The latter covers methods for the dispersion of single-atom sites within solid supports as well as the use of complex nanostructures, and it includes the post-modification of materials via processes such as silylation and atomic layer deposition. All these methodologies exhibit both advantages and limitations, but all offer new avenues for the design of catalysts for specific applications. Because of the high cost of most nanotechnologies and the fact that the resulting materials may exhibit limited thermal or chemical stability, they may be best aimed at improving the selective synthesis of high value-added chemicals, to be incorporated in organic synthesis schemes, but other applications are being explored as well to address problems in energy production, for instance, and to design greener chemical processes. The details of each of these approaches are discussed, and representative examples are provided. We conclude with some general remarks on the future of this field.

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The Propylene Oxide Rearrangement Catalyzed by the Lewis Acid Sites of ZSM-5 Catalyst with Controllable Surface Acidity

Cited by 17 publications

References 38 publications

Direct Propylene Epoxidation with Molecular Oxygen over Cobalt-Containing Zeolites

Direct Propylene Epoxidation with Molecular Oxygen over Cobalt-Containing Zeolites

A DFT Study for Catalytic Deoxygenation of Methyl Butyrate on a Lewis Acid Site of ZSM-5 Zeolite

Designing Sites in Heterogeneous Catalysis: Are We Reaching Selectivities Competitive With Those of Homogeneous Catalysts?

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