For heterogeneously catalyzed multiphase reactions the formation of bubbles may have an influence on mass and heat transfer as well as on the effective reaction rate. This first of two contributions deals with the Ni-catalyzed decomposition of H 2 O 2 , which was used as a model system for an (almost) isothermal reaction with a gaseous product. (In part II the strongly exothermic hydrogenation of hexene will be analyzed, where gas/vapor bubbles may be generated by overheating of the catalyst.) The discharge of O 2 bubbles formed by decomposition of H 2 O 2 enhances the external mass and heat transfer up to one order of magnitude. This is in analogy to the well-known phenomena during nucleate boiling. The experiments and theoretical considerations also show that the internal mass transfer depends on the intensity of the reaction and thus on the H 2 O 2 concentration, which is in contradiction to the classical Thiele approach. This discrepancy could be explained by a modified model that takes the formation of bubbles into account.

Microcapsules were prepared by a coupling reaction of disuccinimido 4,4'-azobis(4-cyanovalerate) b, with L-lysine, and/or polyallylamine in a waterloil emulsion system. The microcapsules show a light-responsive release of an inner content, succinylated bovine serum albumin, to the outer bulk phase. Effects of the composition of the coupling suspension on the photo-durability of the microcapsules obtained were examined. The microcapsules would be useful as a device of photo-responsive systems.

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For heterogeneously catalyzed multiphase reactions the formation of bubbles may have an influence on the effective reaction rate. This second of a series of two contributions deals with the Ni-catalyzed hydrogenation of hexene, which was used as a model system for an exothermic gas/liquid (G/L) reaction, where gas/vapor bubbles may be generated by overheating of the catalyst. (In part I, results of catalytic H 2 O 2 decomposition were presented, where the evolution of gas bubbles (O 2 ) always occurs.) A criterion for the formation of vapor bubbles for exothermic G/L reactions is presented, which was verified by experiments in a reactor with an inspection window. For a particle diameter of 6 mm, the effective kinetics of hexene hydrogenation is influenced by internal and external mass and heat transfer. A new and simple method to estimate the mass and heat transfer parameters and the effectiveness factors with regard to pore and external diffusion is presented, which combines the measured temperature difference(s) and the effective rate. For the given reaction conditions, the rate of hexene hydrogenation is not influenced by the evolution of vapor bubbles.

bilanz bei längeren Verweilzeiten in der Epoxidierung durch PO-Folgereaktionen zu höhermolekularen Produkten erklärt werden muss.Die kinetische Modellierung gelang mit Hilfe von formalkinetischen Ansätzen, die teil-weise eine kinetische Hemmung durch Propen enthalten.