Enhancing the Acylation Activity of Acetic Acid by Formation of an Intermediate Aromatic Ester

Duong, Nhung; Wang, Bin; Sooknoi, Tawan; Crossley, Steven; Resasco, Daniel E.

doi:10.1002/cssc.201700394

Cited by 20 publications

(11 citation statements)

References 45 publications

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“…Staged thermal pyrolysis is one of the most promising approaches to decompose biomass into separate streams, more amenable for subsequent catalytic upgrading to fuels and chemicals. − Furanic compounds obtained from thermal decomposition in the medium range are particularly suited for C–C coupling upgrading. ,− Furfurala representative molecule of this stageis unstable and may easily polymerize and form humins. Then, it would be a good strategy to convert furfural to more stable cyclopentanone via a two-step metal-catalyzed aqueous hydrogenation/isomerization known as the Piancatelli ring rearrangement .…”

Section: Introductionmentioning

confidence: 99%

Aldol Condensation of Cyclopentanone on Hydrophobized MgO. Promotional Role of Water and Changes in the Rate-Limiting Step upon Organosilane Functionalization

et al. 2019

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Aldol condensation is a key CC coupling reaction for upgrading of biomass-derived oxygenates to fuels and chemicals. Here, we investigate the effects of added water on the condensation of cyclopentanone (CPO) on hydrophobized MgO catalysts. We have found that the role of water strongly depends on the degree of hydrophobic functionalization of the MgO surface. That is, on a nonfunctionalized (hydrophilic) high-surface-area MgO catalyst, the rate decreases with the addition of water, mostly due to active site blockage. By contrast, on MgO hydrophobized via silylation with octadecyltrichlorosilane (OTS), the rate actually increases with added water. A concomitant change in kinetics is observed from the pristine (hydrophilic) MgO to the hydrophobized sample. Specifically, on the hydrophilic sample, the reaction is first-order, as expected if the rate-limiting step is the formation of an enolate intermediate via α-H abstraction at a basic site, as widely reported in previous literature. By contrast, on the hydrophobized sample, the reaction becomes second-order, indicating a shift in ratelimiting step to the bimolecular CC coupling. On pristine MgO, acid−base pairs are fully available on the surface, with the acid site polarizing the CO group in the second cyclopentanone (electrophile) and making the attack by the enolate very favorable. It is proposed here that grafted OTS molecules interfere between active sites, making the adsorbate−adsorbate interaction on the surface less likely and reducing the rate of CC coupling. Both isotope effect experiments and ab initio molecular dynamics simulations of cyclopentanone adsorption at the MgO/OTS interface further support this argument. Therefore, the promotional role of water seems to be the assistance of the CC bond-forming step. It is proposed that, at low concentrations, water can help the second molecule (electrophile) be polarized from a remote Mg 2+ site through a chain of Hbonded molecules.

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Section: Introductionmentioning

confidence: 99%

Aldol Condensation of Cyclopentanone on Hydrophobized MgO. Promotional Role of Water and Changes in the Rate-Limiting Step upon Organosilane Functionalization

et al. 2019

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“…However, alternatively, apocynin could be also generated by means of the Fries rearrangement of guaiacol acetate via an intermolecular pathway, which is catalyzed by acid sites. 32,46…”

Section: Resultsmentioning

confidence: 99%

Hydrotreating of Guaiacol and Acetic Acid Blends over Ni₂P/ZSM-5 Catalysts: Elucidating Molecular Interactions during Bio-Oil Upgrading

et al. 2019

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Catalytic hydrodeoxygenation (HDO) is an effective technology for upgrading pyrolysis bio-oils. Although, in the past years, this process has been extensively studied, the relevance of the cross-reactivity between the numerous chemical components of bio-oil has been scarcely explored. However, molecular coupling can be beneficial for improving the bio-oil characteristics. With the aim of gaining a better understanding of these interactions, this work investigates the catalytic hydrodeoxygenation of mixtures of two typical components of pyrolysis bio-oils: guaiacol and acetic acid. The catalytic tests were carried out employing a bifunctional catalyst based on nickel phosphide (Ni2P) deposited over a commercial nanocrystalline ZSM-5 zeolite. The influence of both hydrogen availability and temperature on the activity and product distribution, was evaluated by carrying out reactions under different H2 pressures (40–10 bar) and temperatures (between 260 and 300 °C). Using blends of both substrates, a partial inhibition of guaiacol HDO occurred because of the competence of acetic acid for the catalytic active sites. Nevertheless, positive interactions were also observed, mainly esterification and acylation reactions, which could enhance the bio-oil stability by reducing acidity, lowering the oxygen content, and increasing the chain length of the components. In this respect, formation of acetophenones, which can be further hydrogenated to yield ethyl phenols, is of particular interest for biorefinery applications. Increasing the temperature results in an increment of conversion but a decrease in the yield of fully deoxygenated molecules due to the production of higher proportion of catechol and related products. Additional experiments performed in the absence of hydrogen revealed that esterification reactions are homogeneously self-catalyzed by acetic acid, while acylation processes are mainly catalyzed by the acidic sites of the zeolitic support.

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“…7 They also showed that the rate-limiting step seems to depend on the substrate, a conclusion aligned with what is known about the Friedel−Crafts acylation of aromatics. 8 Specifically, the acylation of 2-methylfuran was found to be controlled by the formation of the acyl group (viz., dissociation of the anhydride), whereas the acylation of the furan was controlled by the deprotonation of the Wheland intermediate. Following up on that work, Park et al achieved the synthesis of tunable oleo-furan surfactants by reacting activated, substituted furans with acid anhydrides over Brønsted acidic SPP.…”

Section: Introductionmentioning

confidence: 99%

“…The acylation of aromatic or furanic compounds is an important carbon–carbon bond-forming reaction for the synthesis of fuels and intermediates for pharmaceuticals and a range of chemicals. , Conventional acylation processes use homogeneous Lewis acid catalysts such as AlCl 3 and BF 3 , which contribute to environmentally hazardous side products and waste. − In recent work, Koehle et al demonstrated that the H-BEA zeolite and the isomorphously substituted Lewis acidic Sn-BEA zeolite can selectively catalyze the acylation of furans with acetic anhydride. , Mechanistic studies proposed that the reaction follows the classic addition–elimination electrophilic substitution mechanism on both H-BEA and Sn-BEA . They also showed that the rate-limiting step seems to depend on the substrate, a conclusion aligned with what is known about the Friedel–Crafts acylation of aromatics . Specifically, the acylation of 2-methylfuran was found to be controlled by the formation of the acyl group ( viz ., dissociation of the anhydride), whereas the acylation of the furan was controlled by the deprotonation of the Wheland intermediate.…”

Section: Introductionmentioning

confidence: 99%

Brønsted Acid Catalysis of the Direct Acylation of 2-Methylfuran by Acetic Acid. Theoretical Insights into the Role of Brønsted Acidity and Confinement

2021

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It has been reported that the rate of the direct acylation of 2methylfuran (2-MF) by acetic acid (AcOH) in H-ZSM5 and H-BEA zeolites is controlled by the dehydration of the acid and the formation of the acyl intermediate, which raises the reasonable question of whether it could be accelerated by an acidic catalyst stronger than an aluminosilicate. We report on a comprehensive computational study of the reaction over the Keggin-type phosphotungstic acid (HPW), widely considered a superacid, and in H-BEA. We find that HPW can catalyze the acylation of 2-MF 1.5 times as fast as H-BEA but not because it is more efficient in catalyzing the dehydration of the acidneither on HPW nor on H-BEA is the acylation reaction rate determined by the dehydration of AcOH. On HPW, the turnover frequency is limited by the dissociation of an acylium−water complex and the desorption of the water molecule; the subsequent electrophilic attack at the furan is non-activated and proceeds spontaneously. On H-BEA, on the other hand, the reaction rate is limited by the deprotonation of the Wheland intermediate after the electrophilic addition of the acylium, which itself is an activated step. Although in light of these findings the need to accelerate the dehydration of AcOH becomes rather moot, our study reveals that confinement and enthalpic stabilization of a transition state can trump sheer Brønsted acidity. Owing to extra enthalpic stabilization of the respective transition state by the zeolite framework and by the furan co-adsorbate, H-BEA is more active than HPW for the dehydration of the organic acid, presenting both the lowest intrinsic free energy barrier, by 3 kcal/mol, and the lowest free energy span, by 6 kcal/mol. By investigating a number of pathways, we find that a mechanistically similar pathway on HPW turns out to be kinetically irrelevant due to significant entropic losses related to the binding of the furan co-adsorbate; on H-BEA, these losses are compensated by the strong enthalpic gains.

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Enhancing the Acylation Activity of Acetic Acid by Formation of an Intermediate Aromatic Ester

Cited by 20 publications

References 45 publications

Aldol Condensation of Cyclopentanone on Hydrophobized MgO. Promotional Role of Water and Changes in the Rate-Limiting Step upon Organosilane Functionalization

Aldol Condensation of Cyclopentanone on Hydrophobized MgO. Promotional Role of Water and Changes in the Rate-Limiting Step upon Organosilane Functionalization

Hydrotreating of Guaiacol and Acetic Acid Blends over Ni₂P/ZSM-5 Catalysts: Elucidating Molecular Interactions during Bio-Oil Upgrading

Brønsted Acid Catalysis of the Direct Acylation of 2-Methylfuran by Acetic Acid. Theoretical Insights into the Role of Brønsted Acidity and Confinement

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Enhancing the Acylation Activity of Acetic Acid by Formation of an Intermediate Aromatic Ester

Cited by 20 publications

References 45 publications

Aldol Condensation of Cyclopentanone on Hydrophobized MgO. Promotional Role of Water and Changes in the Rate-Limiting Step upon Organosilane Functionalization

Aldol Condensation of Cyclopentanone on Hydrophobized MgO. Promotional Role of Water and Changes in the Rate-Limiting Step upon Organosilane Functionalization

Hydrotreating of Guaiacol and Acetic Acid Blends over Ni2P/ZSM-5 Catalysts: Elucidating Molecular Interactions during Bio-Oil Upgrading

Brønsted Acid Catalysis of the Direct Acylation of 2-Methylfuran by Acetic Acid. Theoretical Insights into the Role of Brønsted Acidity and Confinement

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Hydrotreating of Guaiacol and Acetic Acid Blends over Ni₂P/ZSM-5 Catalysts: Elucidating Molecular Interactions during Bio-Oil Upgrading