Molecular‐level Understanding of the Rate‐determining Step in Esterification Reactions Catalyzed by H‐ZSM‐5 Zeolite. An Experimental and Theoretical Study

Gomes, Gláucio José; Zalazar, María Fernanda; Arroyo, Pedro Augusto; Scremin, Fernando Reinoldo; Costa, Marcelo; Bittencourt, Paulo Rodrigo Stival; Lindino, Cléber Antônio; Peruchena, Nélida María

doi:10.1002/slct.201900689

Cited by 11 publications

(12 citation statements)

References 72 publications

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“…OAc adsorbed complex on the active site results in an adsorption energy of − 25.5 kJ mol −1 , similar values can be found for adsorption of acetic acid in H-ZSM-5 [51,52] and in H-Beta [17]. No experimental value is found for the adsorption of oleic acid.…”

Section: Computational Resultssupporting

confidence: 69%

Oleic Acid Esterification Catalyzed by Zeolite Y-Model of the Biomass Conversion

et al. 2019

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Residual oils and fats are promising renewable sources for the production of liquid fuels and the synthesis of various chemicals with significant life cycle and large-scale economic advantages over other biomass sources. Thus, oleic acid esterification was investigated on zeolites type FAU and sulfuric acid by kinetic, spectroscopic assessments and theoretical calculations using a hybrid ONIOM scheme. In the catalytic tests, the solid catalyst with the highest Si/Al (H-Y-80) ratio showed the highest catalytic activity for esterification (92% conversion) as compared to H-Y-5.2 (66% conversion), Na-Y (15% conversion) and homogeneous acid catalysis (89% conversion). The catalytic activity between different acid catalysts is discussed. It was observed that the acidity of the active sites and the hydrophobicity resulting from the Si/Al molar ratio influence the esterification conversion. Theoretical calcultations predicts that the voluminous confined space of the FAU zeolite perfectly accommodates the oleic acid molecule in the adsorption step (E ads = − 25.5 kJ mol −1 ) and the van der Waals interactions of the zeolite walls with the aliphatic chain help to accommodate the bulky molecule between the supercages. Experimental and theoretical results confirm that H-Y-80 zeolite applied in the esterification reaction can be an efficient catalyst in processes involving conversion of unsaturated fatty acids.

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Section: Computational Resultssupporting

confidence: 69%

Oleic Acid Esterification Catalyzed by Zeolite Y-Model of the Biomass Conversion

et al. 2019

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“…We analyzed the main adsorption modes of AA on the surface of H-Beta and H-ZSM-5 zeolites and characterized the main properties of the adsorbed complexes. 22,23 However, the role of the structure of different zeolites in these processes and its relationship with the confinement effect has not yet been thoroughly studied.…”

Section: Introductionmentioning

confidence: 99%

Comparative Study of Adsorbed Complexes inside Pores and Cavities of Acid Zeolites with Different Topology: Experimental and Theoretical Insights into Confinement Effects

Romero Ojeda,

Gomes,

Bittencourt

et al. 2024

J. Phys. Chem. C

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The distinctive topology of pores and cavities of zeolites plays a key role in several applications including catalysis, adsorption, and ion exchange, where confinement effects are significant and can affect the selectivity, stability, and reactivity of catalytic processes. In this study, the effect of confinement on the adsorption of acetic acid on zeolites H-ZSM-5, H-Beta, H-Y, and H-MOR was evaluated by means of thermogravimetric analysis coupled with Fourier Transform Infrared (TG-FTIR) spectroscopy and density functional calculations, including electron density analysis by quantum theory of atoms in molecules. The catalysts were characterized using X-ray powder diffraction (XRD), attenuated total reflection (ATR), and Fourier transform infrared (FTIR) spectroscopy of adsorbed Pyridine (FTIR-Py). TG-FTIR for the first mass loss process, adsorption energy calculations, and electron density results show that the strength of the adsorption of acetic acid between the different acidic zeolites decreases in the order of H-MOR > H-ZSM-5 > H-Beta > H−Y. Adsorption of acetic acid within H-ZSM-5 and H-MOR allows to maximize the interactions with the zeolite framework and thus the confinement, resulting in an additional stabilization in the adsorption process. In contrast, for H-Beta and H−Y zeolites, the confinement effect on the acetic acid molecule is small, and the adsorption energy is mostly related to the interactions at the active site (BAS and basic site).

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“…Beyond that the transesterification mechanisms of vegetal oils by homogeneous catalysts are well understood, the reactions mechanisms of oils catalyzed by heterogeneous catalyst have not been dealt with in depth because of the complexity of the study of the surface-reactants system. In heterogeneous catalysis, the adsorption is the first step that initiates the reaction, and in general, the reactant molecules are adsorbed in very different ways due to the huge complexity of the solid surfaces [11,12]. Although, MCM-41 material is very commonly used as a support for catalysts, nevertheless, theoretical studies are limited.…”

Section: Introductionmentioning

confidence: 99%

Molecular Insights on the Role of (CTA+)(SiO−) Ion Pair into the Catalytic Activity of [CTA+]–Si–MCM-41

et al. 2019

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In this work, a theoretical study in conjunction with a spectroscopic analysis by FTIR were carried out in order to obtain molecular insights on the role of (CTA + )(≡SiO − ) ion pair into the catalytic activity of [CTA + ]-Si-MCM-41, the non-calcined form of Si-MCM-41. The reaction of transesterification of ethyl acetate with methanol was used as a model of transesterification of vegetal oils using the mesoporous heterogeneous catalyst. The theoretical study was performed in the framework of density functional theory (DFT) in order to provide new insights that could be helpful in the understanding of these chemical reactions on solid surfaces. It is found that the most favorable reaction mechanism is the dual site mechanism and that the presence of the (CTA + )(≡SiO − ) ionic pair is fundamental for the catalytic activity. The basic center of [CTA + ]-Si-MCM-41 catalyst polarizes the adsorbed methanol and the acid center polarizes the carbonyl of adsorbed ethyl acetate. Thus, this bifunctional catalytic site makes possible the concerted adsorption of both reactants at the pore mouth and generates a concerted transition state that gives rise to the beginning of the transesterification reaction and the formation of the unstable tetrahedral intermediate which will give rise to the products.

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Molecular‐level Understanding of the Rate‐determining Step in Esterification Reactions Catalyzed by H‐ZSM‐5 Zeolite. An Experimental and Theoretical Study

Cited by 11 publications

References 72 publications

Oleic Acid Esterification Catalyzed by Zeolite Y-Model of the Biomass Conversion

Oleic Acid Esterification Catalyzed by Zeolite Y-Model of the Biomass Conversion

Comparative Study of Adsorbed Complexes inside Pores and Cavities of Acid Zeolites with Different Topology: Experimental and Theoretical Insights into Confinement Effects

Molecular Insights on the Role of (CTA+)(SiO−) Ion Pair into the Catalytic Activity of [CTA+]–Si–MCM-41

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