Einfaches Differential‐Calorimeter zur kinetischen Untersuchung von Lösungsreaktionen zwischen −140 und +90 °C

Koch, E.

doi:10.1002/cite.330371004

Cited by 45 publications

(12 citation statements)

References 6 publications

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“…The DTA experiments were performed in our "all-liquid"-apparatus [11], the temperatureprogrammed measurements of the optical density in a double-beam spectrometer with vacuum-insulated quartz cuvettes [12,13] and an Eurotherm temperature controller.…”

Section: Experiments Evaluation and Resultsmentioning

confidence: 99%

Characteristic temperatures of non-isothermal rate signals of one-step processes

Koch

1987

Journal of Thermal Analysis

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Analytical expressions for the heights, and for the initial, the peak and the final temperature of the rate signals of bimolecular reactions, measured at constantly increased temperature, are derived. They are based on the specific time of the reaction, available from the activation data, and on the relative minimum rate used. DTA and non-isothermal u.v. absorption studies of 29 different organic reactions in solution reveal that the accuracy of the expressions is sufficient to reproduce the true position of peaks of one-step reactions on the temperature or time axis. A program for simple calculations, written in BASIC, is enclosed.In the approximate kinetic theory of the author [1,2], it is shown that the position and shape of the reaction rate peak of an elementary reaction of n-th order, generated for temperature rise proportional to time (T = m.t), can be calculated from the activation data (E, k~) via the specific time u at the maximum,using the heating rate rn (deg/min) and gas constant R. For a first-order process, this theory, which may be called "Theory of the Characteristic Rate Coefficients", is based on typical products of a specific rate coefficient with the u-parameter at characteristic points of the curve (onset, halfwidth points, peak, points of inflection, end), and has been shown to be very useful for the study and discussion of nonisothermal kinetic signals. For example, for a first-order process, the rate coefficients at start, maximum and end are obtained as follows [1,3], ko ~ Z__L (2a)Urne

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Section: Experiments Evaluation and Resultsmentioning

confidence: 99%

Characteristic temperatures of non-isothermal rate signals of one-step processes

Koch

1987

Journal of Thermal Analysis

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“…One problem in gaining reliable overall data is the use of an appropriate weighting procedure [34,38], but such unavoidable shortcomings are partially compensated for by the application of the same evaluation program to both experimental and theoretical records. This concept raises the rather materialistic level of the well-proven reference techniques, realized by twin arrangements [6,39], to the rather intellectual level of referencebased evaluation strategies [27,40]. Experience in the application of probability theory [1,41] will facilitate a realiable interpretation of the thermoanalytical patterns obtained.…”

Section: Discussionmentioning

confidence: 98%

The ‘Theorem of common kinetic runs’ in homogeneous non-isothermal reaction kinetics

Koch¹

1992

Journal of Thermal Analysis

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The kinetic features of the fundamental homogeneous two-reaction models for linearly increasing temperature have been studied systematically by the analysis of 2500 signal curves (organized in 250 series), obtained from computer simulations and compared with numerous TA experiments.For methods based on a proportionality between the particular reaction rates and their contribution to the derivative overall signal, it has been found that characteristic behaviour sets of three order-dependent parameters which refer to definite intervals of the starting concentration in series, can be extracted from the halfwidth and shape index of the curves. Such thermoanalytical patterns agree with those obtained from the distribution lists of some thousand DTA-and UV-experiments. They are presented for the 21 most important two-step model and almost independent of the activation data and of the method-dependent proportionality factors. Therefore, they allow for the direct kinetic identification of the complex reaction involved.

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“…The experiments were carried out at linearly increased temperature, both in our all-liquid DTA apparatus [28] and in a UV spectrometer [13]. All component solutions except one were pipetted into the reaction vessel; the total solution and the reference sample, consisting of the solvent and the stable components, were then thermostatted (cf.…”

Section: Methodsmentioning

confidence: 99%

“…[49, 53, 54, 591 and with our results with subsystems (Table 3; steps 1, 6 and 8); in the case of the kinetically less relevant steps 2, 4, 5, and 7, the activation energies were merely assumed to be small Table 4 may indicate that both theory and practice for such complicated kinetic problems cannot be perfect. Our DTA apparatus [28] has been constructed with the idea of a relatively simple, but universal instrument, which can be applied in a very flexible way to general kinetic and energetic problems in solution. Special high-sensitive calorimeters would yield enthalpies of much higher accuracy, but bear the burden of a cell constant much too slow for effective kinetic studies.…”

Section: The Model Should Involve All Reactants (Without H + ) Onmentioning

confidence: 99%

New strategies for studies on the kinetics and energetics of the Belousov‐Zhabotinskii reaction

Koch

Nagy-Ungvárai

1987

Ber Bunsenges Phys Chem

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Catalysis / Chemical Kinetics / Computer Experiments / Oscillatory Chemical Reactions / Thermal AnalysisThe oscillatory Belousov-Zhabotinskii reaction and its subsystems were studied by z 1700 DTA and UV experiments performed at linearly increased temperature. The starting concentrations of bromate, bromide, catalyst, and malonic acid were varied in order to obtain "concentration codes" of such series. These represent the dependence of any parameters in discrete ranges of the starting concentrations of the different components. Particularly adequate for a model check are the mechanistic codes (= MCC's), which concern the shape index and reaction type index: If these mechanistic coordinates remain constant in such a concentration interval, other data, e.g. activation energies, can be attributed to a rate-determining process. -The results led to a nine-step model which is based on the FKN mechanism and is capable of roughly reproducing the influence of the initial concentrations and heating rate on 11 parameters characteristic of the envelope and of the oscillations of the experimental signals. The MCC's of the experimental and theoretical series are similar, revealing 4-5 rate-determining steps in the different concentration ranges. -The activation energies agree with values from the literature, cited for three steps; these and further resulting activation energies are consistent with our studies with subsystems.

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Einfaches Differential‐Calorimeter zur kinetischen Untersuchung von Lösungsreaktionen zwischen −140 und +90 °C

Cited by 45 publications

References 6 publications

Characteristic temperatures of non-isothermal rate signals of one-step processes

Characteristic temperatures of non-isothermal rate signals of one-step processes

The ‘Theorem of common kinetic runs’ in homogeneous non-isothermal reaction kinetics

New strategies for studies on the kinetics and energetics of the Belousov‐Zhabotinskii reaction

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