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The shape of droplets in liquid-liquid systems influences their mass and momentum transfer processes. The deviation from sphericity of rising droplets in liquid-liquid systems was investigated for different droplet sizes. Rainbow refractometry permits one to test, in this case, whether the use of laser-optical particle sizing will be correct or faulty. Since the assumption of spherical particle geometry is a general basis of laser-optical particle-sizing techniques such as rainbow refractometry or phase Doppler anemometry, deviation from the spherical shape results in a measuring error. A sphericity check based on rainbow refractometry is introduced.

follows. The rate equation for amide formation (A) can be expressed as (10) With quasi-stationarity for dA dt because of a very low amide concentration (compare GC/MS analysis), the formation of e-caprolactam can be described as an overall first order reaction (11) This is consistent with both types of measurements and the apparent activation energy is given by (12) where DG can be replaced by DH for a constant volume for the equilibrium.The measured apparent energy of activation of e-caprolactam formation is consistent with the apparent activation energy of the pyrolysis of carbonic acids which proceeds via a cyclic transition state as well (Scheme 2). In case of ethyl acetate ester an apparent energy of activation of 200 kJ/mol and a preexponential factor of 14.3 log (k 0 /min ±1 ) are determined [12].The preexponential factor is in good agreement with the activation entropy of the cyclic transition state derived from the loss of degree of freedom [12]. ConclusionThe gradient free reactor developed in this work provides a reliable method for kinetic measurements of thermal decomposition reactions under isothermal conditions. The procedure is validated with the decarboxylation of malonic acid. The measured parameters of the decarboxylation of malonic acid correspond with data from literature and dynamic measurements with low heating rates. In the case of polyamide 6, kinetic parameters of the degradation are obtained, which are in accordance with a unimolecular cis-elimination. The kinetic parameters of the dynamic method of TGA are vali-dated as well. The measured apparent energy of activation and the preexponential factor of e-caprolactam formation can be explained by a comparison with the pyrolysis of carbonic acids, which proceeds in a similar way. The advantage of the isothermal method is that the reaction order can be determined with dependence on temperature. In case of polyamide 6 degradation, a higher order of reaction is obtained above 415°C. This is correlated with the formation of the cyclic dimer which occurs above 415°C and, therefore, should proceed via a second order reaction. AcknowledgmentsWe gratefully acknowledge the support of this work by Volkswagenstiftung and Max-Buchner Forschungsstiftung. References[1] Hornung, U.; Bestimmung der Vergasungskinetik von Kunststoffen mit Hilfe eines isotherm betriebenen Kreislaufreaktors, Fortschritt-Berichte VDI, Reihe 3, Band 485, VDI-Verlag, Düsseldorf 1997. [2] Hornung, U.; Bockhorn, H.; Hornung, A.; Teepe, S.; Weichmann, J.; Isotherme und dynamische Messungen zur Bestimmung der Vergasungskinetik von Kunststoffen, Experimente und Modellierung zur heterogenen und homogenen Verbrennung Workshop der Universität Karlsruhe (TH) und desand designing the liquid-liquid extraction process. Within this study laser-optical measurement techniques, Phase-Doppler Anemometry (PDA) and rainbow refractometry (RBR), are employed for the determination of these process data as a result of single-droplet experiments. Theoretical studies and experimental results will underl...