Determination of Carboxylic Acid Dissociation Constants to 350 °C at 23 MPa by Potentiometric pH Measurements

Sue, Kiwamu; Ouchi, Fumiaki; Minami, Kimitaka; Arai, Kunio

doi:10.1021/je049923q

Cited by 23 publications

(19 citation statements)

References 32 publications

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“…Hydrogen peroxide could dissociate to provide protons as

{normalH}_{2} {normalO}_{2} \binom{0false \to}{\leftarrow} H^{+} + {HO}_{2}^{-}

The p K a for this dissociation is of 11.75 at 20°C . Thus, hydrogen peroxide is a very weak acid compared to acetic acid, whose p K a is equal to 4.73 at 20°C, and compared to the second dissociation of sulfuric acid, whose p K a is equal to 1.88 at 20°C . Thus, the enhancement of reaction rate with hydrogen peroxide cannot be linked to the acidity of hydrogen peroxide but maybe on its nucleophile activity.…”

Section: Resultsmentioning

confidence: 99%

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Influence of ring‐opening reactions on the kinetics of cottonseed oil epoxidation

Cai

Zheng

Aguilera

et al. 2018

Int J of Chemical Kinetics

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Production of epoxidized vegetable oils becomes more and more important because they are renewable, nontoxic, and biodegradable chemicals. At the industrial scale, the Prileschajew oxidation is used to produce epoxidized vegetable oils from the corresponding vegetable oils. This oxidation uses an oxygen carrier, which is a percarboxylic acid produced in situ in the aqueous phase, to epoxidize the unsaturated groups on the vegetable oils. One of the main drawbacks of this method is the presence of side reactions: ring-opening reactions of the epoxide group. To minimize the ringopening reactions and to find the most suitable reactor configuration, it is essential to investigate deeply the different ring-opening reactions.For this work, epoxidation of cottonseed oil by peracetic acid in a batch reactor was studied. By developing a suitable modeling strategy, the kinetic constants for the ringopening reactions by water, hydrogen peroxide and acetic and peracetic acids were estimated. It was found that ring opening by acetic and peracetic acids was faster than by water and hydrogen peroxide. Based on this model, it was found that a semibatch reactor where hydrogen peroxide and sulfuric acid were added is the most suitable configuration. K E Y W O R D Sepoxidation, kinetic modeling, liquid-liquid reaction system, parameter estimation 726

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“…Hydrogen peroxide could dissociate to provide protons as

{normalH}_{2} {normalO}_{2} \binom{0false \to}{\leftarrow} H^{+} + {HO}_{2}^{-}

Section: Resultsmentioning

confidence: 99%

“…where

K_{II}^{C}

is the second dissociation of sulfuric acid and

K_{AA - diss}^{C}

is the dissociation of acetic acid …”

Section: Resultsmentioning

confidence: 99%

Influence of ring‐opening reactions on the kinetics of cottonseed oil epoxidation

Cai

Zheng

Aguilera

et al. 2018

Int J of Chemical Kinetics

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“…Acid dissociation is also known to depend on temperature . The temperature effect on acid dissociation was not factored in our kinetic model, as the temperature dependence of carboxylic acid's dissociation constants is generally negligible (<10% compared to 25°C) over the range of temperatures used in this study . Thus, kinetic parameters were calculated based on measured rates and extents of reactions for acids starting at the same measured initial pH.…”

Section: Reaction Modelmentioning

confidence: 99%

Reaction mechanisms and kinetics of xylo‐oligosaccharide hydrolysis by dicarboxylic acids

2012

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in Wiley Online Library (wileyonlinelibrary.com).Hydrothermal pretreatment of lignocellulosic materials generates a liquid stream rich in pentose sugar oligomers. Cost-effective hydrolysis and utilization of these soluble sugar oligomers is an integral process of biofuel production. We report integrated rate equations for hydrolysis of xylo-oligomers derived from pretreated hardwood by dicarboxylic maleic and oxalic acids. The highest xylose yield observed with dicarboxylic acids was 96%, and compared to sulfuric acid, was 5-15% higher with less xylose degradation. Dicarboxylic acids showed an inverse correlation between xylose degradation rates and acid loadings unlike sulfuric acid for which less acid results in less xylose degradation to aldehydes and humic substances. A combination of high acid and low-temperature leads to xylose yield improvement. Hydrolysis time course data at three different acid concentrations and three temperatures between 140 and 180 C were used to develop a reaction model for the hydrolysis of xylo-oligosaccharides to xylose by dicarboxylic acids.

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“…The acidity of chemical compounds is a prerequisite in understanding many fundamental phenomena in chemistry, biological science and medicine, and the knowledge of this thermodynamic property finds applications in control of many industrial processes, including chemical and pharmaceutical manufactures [1,2]. The dissociation constants of carboxylic acids in aqueous solution can be experimentally obtained by measurements of conductance [3,4], calorimetry [5], potentiometry [6][7][8][9] and spectroscopy [10]. In some cases, the experimental methods can be restricted, for instance, to a certain range of temperatures, pH and pK a .…”

Section: Introductionmentioning

confidence: 99%

Acidity constants and its dependence on solvent selection from first-principles calculations using cluster-continuum models

Pham

Taylor

Henson

2014

Chemical Physics Letters

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Dissociation constants of selected carboxylic acids in aqueous and organic solvents were calculated at quantum chemical level. We considered cases in which trace quantities of water may be present, as well as cases in which water was entirely absent. In the latter cases, alternative proton acceptors need to be considered. For aqueous solvent, short-range solvation effects are considered by adding explicit water molecules as the first solvent shell. In the absence of water, corresponding organic solvents are used directly as the proton acceptors and the resulted pK a are quite comparable to those obtained from previous case of aqueous solvent.

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Determination of Carboxylic Acid Dissociation Constants to 350 °C at 23 MPa by Potentiometric pH Measurements

Cited by 23 publications

References 32 publications

Influence of ring‐opening reactions on the kinetics of cottonseed oil epoxidation

Influence of ring‐opening reactions on the kinetics of cottonseed oil epoxidation

Reaction mechanisms and kinetics of xylo‐oligosaccharide hydrolysis by dicarboxylic acids

Acidity constants and its dependence on solvent selection from first-principles calculations using cluster-continuum models

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