Theoretical Study of the Thermal Decomposition of Acetic Acid: Decarboxylation Versus Dehydration

Nguyen, Minh Tho; Sengupta, Debasis; Raspoet, Greet; Vanquickenborne, L. G.

doi:10.1021/j100031a015

Cited by 99 publications

(90 citation statements)

References 4 publications

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“…Our measured rate constant data show that the tendency of the dehydration reaction to occur is about two times higher than that of the decarboxylation reaction, as observed previously by [19][20][21]. Mackie and Doolan [18], on the other hand, argued that both reactions have about the same probability.…”

Section: Acetic Acid Pyrolysissupporting

confidence: 86%

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Unimolecular decomposition of formic and acetic acids: A shock tube/laser absorption study

Elwardany

Nasir

Es-sebbar

et al. 2015

Proceedings of the Combustion Institute

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The thermal decomposition of formic acid (HCOOH) and acetic acid (CH 3 COOH), two carboxylic acids which play an important role in oxygenate combustion chemistry, were investigated behind reflected shock waves using laser absorption. The rate constants of the primary decomposition pathways of these acids:were measured using simultaneous infrared laser absorption of CO, CO 2 and H 2 O at wavelengths of 4.56, 4.18 and 2.93 microns, respectively. Reaction test conditions covered temperatures from 1230 to 1821 K and pressures from 1.0 to 6.5 atm for dilute mixtures of acids (0.25 -0.6%) in argon. The rate constants of dehydration (R1) and decarboxylation (R2) reactions of formic acid were calculated by fitting exponential functions to the measured CO, CO 2 and H 2 O time-history profiles. These two decomposition channels were found to be in the fall-off region and have a branching ratio, ! ! , of approximately 20 over the range of pressures studied here. The best-fit Arrhenius expressions of the first-order rates of R1 and R2were found to be:! 6.5 atm = 9.12 ×10 !" exp −30275 s -1 (±32%)The rate constants for acetic acid decomposition were obtained by fitting simulated profiles, using an acetic acid pyrolysis mechanism, to the measured species time-histories. The branching ratio, ! ! , was found to be approximately 2. The decarboxylation and dehydration reactions of acetic acid appear to be in the falloff region over the tested pressure range:! 1 atm = 3.18×10 !! ×exp −28679 s -1 (±30%)! 6 atm = 3.51×10 !" ×exp −31330 s -1 (±26%)! 1 atm = 7.9 ×10 !! exp −29056 s -1 (±34%).! 6 atm = 6.34×10 !" ×exp −31330 s -1 (±31%).

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Section: Acetic Acid Pyrolysissupporting

confidence: 86%

“…! ratio was two and in agreement with the ab-initio calculations of Nguyen et al [20] and Duan and Page [21].…”

Section: Introductionsupporting

confidence: 89%

Unimolecular decomposition of formic and acetic acids: A shock tube/laser absorption study

Elwardany

Nasir

Es-sebbar

et al. 2015

Proceedings of the Combustion Institute

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“…Bond energies for acetic acid are provided14,15 for later comparison with unimolecular decomposition pathways.…”

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confidence: 99%

Comparison of Unimolecular Decomposition Pathways for Carboxylic Acids of Relevance to Biofuels

2013

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Quantum mechanical molecular modeling is used [M06-2X/6-311++G(2df,p)] to compare activation energies and rate constants for unimolecular decomposition pathways of saturated and unsaturated carboxylic acids that are important in the production of biofuels and that are models for plant and algae-derived intermediates. Dehydration and decarboxylation reactions are considered. The barrier heights to decarboxylation and dehydration are similar in magnitude for saturated acids (∼71 kcal mol(-1)), with an approximate 1:1 [H2O]/[CO2] branching ratio over the temperature range studied (500-2000 K). α,β-Unsaturation lowers the barrier to decarboxylation between 2.2 and 12.2 kcal mol(-1) while increasing the barriers to dehydration by ∼3 kcal mol(-1). The branching ratio, as a result, is an order of magnitude smaller, [H2O]/[CO2] = 0.07. For some α,β-unsaturated acids, six-center transition states are available for dehydration, with barrier heights of ∼35.0 kcal mol(-1). The branching ratio for these acids can be as high as 370:1. β,γ-Unsaturation results in a small lowering in the barrier height to decarboxylation (∼70.0 kcal mol(-1)). β,γ-Unsaturation also leads to a lowering in the dehydration pathway from 1.7 to 5.1 kcal mol(-1). These results are discussed with respect to predicted kinetic values for acids of importance in biofuels production.

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“…19 However, kinetically, both pathways are competitive. Both methane and carbon dioxide could serve as carbon sources for deposition of carbonaceous material on the silver particles.…”

Section: Resultsmentioning

confidence: 99%

Amorphous carbon encapsulation of metal aerosol nanoparticles for improved collection and prevention of oxidation

Scharmach¹,

Sharma

Buchner

et al. 2013

AIChE Journal

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A technique to encapsulate silver nanoparticles in an amorphous carbon matrix to facilitate nanoparticle collection and limit nanoparticle oxidation is presented. A carbon source added to the metal salt precursor solution decomposes to generate amorphous carbon, which forms large aggregates that are efficiently collected by filtration. The carbon matrix can be removed by oxidation with hydrogen peroxide without damaging the silver nanoparticles within it. X-ray diffraction showed no evidence of oxidation of encapsulated particles over a two-week period, whereas bare particles showed oxidation after 1 day. Slight oxidation was observed following carbon removal, but no further oxidation was detected over a subsequent two-week period. Carbon encapsulation improves nanoparticle collection efficiency, relative to direct collection of unagglomerated silver nanoparticles with membrane filters. The yield of metal nanoparticles is increased by a factor 1.5 to 3 using this approach. The encapsulating carbon itself forms dendritic nanostructures that may also be of interest.

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Theoretical Study of the Thermal Decomposition of Acetic Acid: Decarboxylation Versus Dehydration

Cited by 99 publications

References 4 publications

Unimolecular decomposition of formic and acetic acids: A shock tube/laser absorption study

Unimolecular decomposition of formic and acetic acids: A shock tube/laser absorption study

Comparison of Unimolecular Decomposition Pathways for Carboxylic Acids of Relevance to Biofuels

Amorphous carbon encapsulation of metal aerosol nanoparticles for improved collection and prevention of oxidation

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