Kinetics of fatty acid ketonization in liquid phase with anatase and rutile TiO2 catalysts

Boekaerts, Bert; Lorenz, W. J.; Aelst, Joost Van; Sels, Bert F.

doi:10.1016/j.apcatb.2021.121052

Cited by 20 publications

(30 citation statements)

References 52 publications

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“…These reaction data are obtained in conditions without any mass transfer limitation phenomena, which we have previously shown also for the parent material. 26 For the most severely reduced TiO 2 catalyst (600 °C for 5 h) with the lowest specific surface area, the absence of internal diffusion limitation was shown similarly using the Weisz−Prater criterion (see the Supporting Information for detailed calculation and discussion). After 45 min, the parent material showed an 18.8% conversion of lauric acid, with 99% selectivity to the laurone ketone product.…”

Section: ■ Introductionmentioning

confidence: 83%

“…25 We have recently reported on the latter for liquid-phase ketonization of fatty acids, showing a higher intrinsic activity for the rutile TiO 2 phase compared to anatase. 26 Given the higher sensitivity to product deactivation of rutile, especially in a solvent-less reaction system where anatase achieved higher overall fatty acid conversion and ketone product yields on a mass basis, anatase can be considered the preferred catalyst. In this context, a combined green chemistry and life cycle assessment (LCA) analysis study on a dedicated liquid-phase fatty acid ketonization process with anatase TiO 2 demonstrated that its use significantly contributes to the overall environmental burden of wax ketone production.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Afterward, N 2 physisorption analysis was performed to assess the specific surface areas. The ketonization performance for the set of catalysts was determined at a reaction temperature of 340 °C in a batch reactor, operating at autogenous pressure (∼9.5 bar) while stirring at 600 rpm (to avoid (external) mass transfer limitations 26 ).…”

Section: ■ Introductionmentioning

confidence: 99%

“…Our previous study showed an influence of TiO 2 polymorphism on the ketonization rate, with rutile being intrinsically more active than anatase. 26 It was therefore investigated whether the thermal and reduction treatments could cause any crystal phase transformation of the original anatase parent into rutile TiO 2 . Hereto, XRD analysis was performed (Figure S2, Supporting Information).…”

Section: ■ Introductionmentioning

confidence: 99%

“…While this technique does not strictly distinguish between Lewis and Bronsted acid sites, we have shown via pyridine Fourier-transform infrared (FTIR) analysis that the parent material does not exhibit any Bronsted acidity and that the acidity measured via NH 3 TPD is directly related to its Lewis acidity, being coordinatively unsaturated Ti x+ surface sites (Ti x+ −O 2− Lewis acid−base pairs by extent). 26 The total acid site density values of the thermally treated and reduced anatase TiO 2 catalysts are summarized in Table 2. The reader is further referred to the Supporting Information for a more extensive and detailed description of the NH 3 TPD measurements (Figure S3).…”

Section: ■ Introductionmentioning

confidence: 99%

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Metal-Free Reduction Creates Highly Active TiO₂ Surfaces for Fatty Acid Ketonization

Boekaerts

Sels

2022

ACS Sustainable Chem. Eng.

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TiO2 is one of the most promising catalysts for liquid-phase ketonization of carboxylic acids. As recently reported, its use significantly contributes to the overall environmental impact of the fatty acid ketonization process. Therefore, postsynthetic modifications such as metal addition and thermal treatment under inert and reducing atmospheres were studied to enhance the catalytic activity of anatase TiO2 for the ketonization of lauric acid. Although more active surfaces can be generated by the additional metal through hydrogen spillover effects, its presence led to substantial decarboxylation rather than ketonization. Interestingly, metal-free anatase TiO2 is also substantially activated after thermal treatment in nitrogen or hydrogen gas, while maintaining its full ketonization selectivity. Ascertained by X-ray analysis, this was not related to polymorphism but due to a higher content of Lewis acid sites, of which the hydrogen-treated catalysts possessed the largest density. A quadratic relationship appears between the ketonization rate and surface acid site density, a defining characteristic of rate-determining bimolecular C–C coupling in the ketonization mechanism. In contrast to studies on short-chain carboxylic acids, this liquid-phase study renders hydrogenated TiO2 as the most promising catalyst, while metal addition is less suitable for selectivity reasons. Although less essential for bio-oil upgrading, high selectivity is of utmost importance for on-purpose fatty acid ketonization.

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Section: ■ Introductionmentioning

confidence: 83%

Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Metal-Free Reduction Creates Highly Active TiO₂ Surfaces for Fatty Acid Ketonization

Boekaerts

Sels

2022

ACS Sustainable Chem. Eng.

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Revealing the Mechanism of Ketonization of Acetic Acid on HBEA Zeolite via Metadynamics Simulations

Liu,

Zhao,

Liu

et al. 2024

ChemCatChem

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Ketonization of biomass‐derived carboxylic acids offers a promising approach to remove oxygen and upgrade into valuable chemicals. However, the mechanism on Brønsted acid site (BAS) confined in micropores of zeolite remains elusive, due to the difficulty to observe the reaction intermediates experimentally and to locate the transition state via static density functional theory (DFT) calculations. Herein, ketonization of acetic acid on HBEA at 673 K was studied by metadynamics simulations based on DFT. The first reaction step was the concerted protonation and dehydroxylation of acetic acid, resulting in an electrophilic acylium cation and H2O (ΔG‡ = 1.53 eV). The subsequent likely steps, including C‐C coupling through the nucleophilic attack of acetic acid (path I), ketene (path II), and 1,1‐dihydroxyethene and (path III) toward acylium cation were tracked and compared. The high barriers for formation of more nucleophilic intermediates of ketene and 1,1‐dihydroxyethene made the overall path II and III less favorable than the direct coupling between acetic acid and acylium cation (path I, ΔG‡ = 2.15 eV). These results indicate that acylium cation is a key intermediate, and the C‐C coupling between acetic acid and acylium cation via nucleophilic attach is the most favorable path on BAS confined in zeolite.

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The Underlying Catalytic Role of Oxygen Vacancies in Fatty Acid Methyl Esters Ketonization over TiO_x Catalysts

Yazdanpanah,

Fereidooni,

Márquez

et al. 2023

ChemSusChem

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Recently, interest in converting bio‐derived fatty acid methyl esters (FAMEs) into added‐value products has significantly increased. The selectivity of ketonization reaction in the conversion of the FAMEs has significantly hampered the efficiency of this process. Herein, we prepared catalysts with different levels of oxygen vacancies while the crystal phase remained unchanged. The catalyst with the highest level of oxygen vacancy exhibited the maximum selectivity. The density functional theory (DFT) simulation showed an increase in interatomic distances leading to the formation of frustrated Lewis pairs (FLPs) upon the creation of oxygen vacancies. The surface measurements, type and density of acid sites of the catalysts, showed that the Lewis acid sites enhanced the selectivity for ketone production; while Bronsted acid sites increased the formation of by‐products. Moreover, the ketone formation rate was directly proportional to acid density. The findings of this research provide a different approach for catalyst design, based on defects engineering and their effect on the surface activity, which could be used for enhancing the catalytic performance of novel metal oxides.

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Kinetics of fatty acid ketonization in liquid phase with anatase and rutile TiO2 catalysts

Cited by 20 publications

References 52 publications

Metal-Free Reduction Creates Highly Active TiO₂ Surfaces for Fatty Acid Ketonization

Metal-Free Reduction Creates Highly Active TiO₂ Surfaces for Fatty Acid Ketonization

Revealing the Mechanism of Ketonization of Acetic Acid on HBEA Zeolite via Metadynamics Simulations

The Underlying Catalytic Role of Oxygen Vacancies in Fatty Acid Methyl Esters Ketonization over TiO_x Catalysts

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Kinetics of fatty acid ketonization in liquid phase with anatase and rutile TiO2 catalysts

Cited by 20 publications

References 52 publications

Metal-Free Reduction Creates Highly Active TiO2 Surfaces for Fatty Acid Ketonization

Metal-Free Reduction Creates Highly Active TiO2 Surfaces for Fatty Acid Ketonization

Revealing the Mechanism of Ketonization of Acetic Acid on HBEA Zeolite via Metadynamics Simulations

The Underlying Catalytic Role of Oxygen Vacancies in Fatty Acid Methyl Esters Ketonization over TiOx Catalysts

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Product

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Metal-Free Reduction Creates Highly Active TiO₂ Surfaces for Fatty Acid Ketonization

Metal-Free Reduction Creates Highly Active TiO₂ Surfaces for Fatty Acid Ketonization

The Underlying Catalytic Role of Oxygen Vacancies in Fatty Acid Methyl Esters Ketonization over TiO_x Catalysts