Determination of Kinetics in Gas-Liquid Reaction Systems. An Overview

Doğan

Int J of Chemical Kinetics

2020

Increasing energy demand in the world leads to more electricity generation mainly at fossil fuel power plants. Greenhouse gases are thus produced and mostly emitted to the atmosphere directly, resulting in global warming and climate change. Carbon dioxide is believed to be a main pollutant among greenhouse gases responsible from global warming. Conventional systems using mostly amine solutions to capture carbon dioxide at the source have some disadvantages, and alternatives are constantly being searched. In this work, a benign system of aqueous calcium acetate solution was investigated for this purpose. Calcium acetate is easy to produce, relatively cheap, environmentally friendly, nonhazardous, and noncorrosive. These properties make it a great alternative for use in capturing carbon dioxide. This absorption process is accompanied by chemical reaction. Therefore, the reaction kinetics needs to be investigated before its use in absorbers. A stirred cell reactor was used in the experiments using aqueous calcium acetate solution of different concentrations (2‐20% w/w) and different carbon dioxide concentrations in gas mixtures (4.5‐100% v/v dry carbon dioxide) at temperatures ranging from 286 to 352 K. The Gibbs free energy change for the overall reaction between carbon dioxide and aqueous calcium acetate solution was found to be –2.75 kJ/mol that shows the reaction is exergonic and occurs spontaneously. It was also found out that the reaction is pseudo–first order with respect to carbon dioxide which was also proven by calculating the Hatta number. Activation energy and Arrhenius (frequency) constant were also determined experimentally.

Section: Resultssupporting

confidence: 93%

\begin{matrix} true \\ right D_{C {normalO}_{2}}^{Ca {((), normalC H_{3} normalCOO)}_{2}} & = & left (1050.1 - 33.26 \cdot x_{Ca {((), normalC H_{3} normalCOO)}_{2}}) \\ left \times 10^{- 9} \cdot e^{(\frac{- 1895}{T})} . \end{matrix}

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Section: Resultssupporting

confidence: 82%

See 1 more Smart Citation

Kinetics of chemical absorption of carbon dioxide into aqueous calcium acetate solution

Doğan

Int J of Chemical Kinetics

2020

“…That is because the results are pretty much affected by the method of analyses, assumptions made as well as chemicals employed. If the reaction rate constant of the system in this work is compared with the reported data of conventional systems in which alkaline solutions were used and the contribution of the carbonate ion reaction was considered, the results are quite close to each other making the proposed chemical system a good alternative.…”

Section: Resultsmentioning

confidence: 56%

Kinetics of Absorption of Carbon Dioxide into Sodium Metaborate Solution

Doğan

Int J of Chemical Kinetics

2017

Carbon dioxide capture potential of sodium metaborate, which is the main product of the process by means of which hydrogen is obtained from sodium borohydride, was investigated. This work aims at both carbon dioxide capture and finding an alternative use for sodium metaborate. The products of this chemical absorption are sodium carbonate, sodium bicarbonate, and boric acid; all of which are industrially important chemicals. In this study, the kinetics of the reaction between sodium metaborate and carbon dioxide was investigated at atmospheric pressure and temperatures between 17 and 50°C while initial sodium metaborate concentration was changed as 0.5, 1, and 2.5 wt%. The frequency factor and activation energy for this reaction were found as 1.97 × 10−3 m3/mol‐s and 18,062 J/mol, respectively.

“…The kinetic studies are of great importance for both the laboratory research and industrial applications . The intrinsic kinetics, which could also be used as an auxiliary method to verify the mechanism, have not been reported so far for our reaction system.…”

Section: Introductionmentioning

confidence: 99%

Kinetic studies on the liquid‐phase catalytic oxidation of 4‐methyl guaiacol to vanillin

Liu

Mao

et al. 2017

Can J Chem Eng

Kinetic studies on the catalytic oxidation of 4‐methyl guaiacol using an ether intermediate towards vanillin in an agitator bubbling reactor were presented. The reaction was catalyzed by N,N′‐ethylenebis(acetylacetoniminato)‐cobalt(II) hexafluorophosphoric pyridinium (Co‐[Salen‐Py][PF6]2) under strong alkaline conditions with molecular oxygen as the terminal oxidant. The reaction scheme was demonstrated by a detailed analysis of the products distribution and control experiments. The intrinsic kinetics were explored based on our proposed p‐benzoquinone methide mechanism, which revealed that the oxidation rate was determined by the oxidation of phenoxyl anion to phenoxyl radical catalyzed by LCo3+(O2·) (L = [Salen‐Py][PF6]2). The kinetic experiments were performed under a mass transfer‐reaction condition due to the inevitable mass transfer resistance involved. Pseudo‐first order fast reactions were observed for both steps of the consecutive reactions based on the calculated physical and mass transfer parameters. The intrinsic kinetic equations for the first and second steps can be written as RA=5.98×105exp(−31950RT)CCcat.CO2A and RF=1.02×106exp(−29770RT)CCcat.CO2E, respectively, which are well in accordance with the mechanism. These conclusions are expected to give a clue for the mechanistic study, kinetic investigation, reaction optimization, and catalyst design for the oxidation of various p‐cresols.