Exemplary determination and verification of reaction kinetics of a gas-liquid reaction
In the recent decade great progress in simulation of two-phase gas-liquid flow has been achieved. Whereas hydrodynamics and mass transfer can be calculated in great detail, there is still a great uncertainty concerning the quality of reaction kinetics necessary for quantitative predictions of the performance of bubble column or for the development of new types of equipment. This is especially true for industrially relevant gas-liquid reactions which often exhibit complex autocatalytic behavior. The aim of the first project period is the development of a detailed reaction mechanism for the industrial important oxidation of toluene to benzoic acid. The new approach combines theoretical and experimental methods in order to derive reaction pathways and rate expressions in great detail. In the first funding period a flexible reactor for kinetic experiments will be set up. The group of Prof. Zipse, LMU Munich, will predict the reaction pathways and the rate expressions using a quantum mechanical approach. These predictions will be compared with experimental results and improved by combination of theoretical methods with experimental investigations. Once a detailed mechanism has been established, which is able to represent experiments in a very wide range of conditions, the set of elementary reactions will be reduced to an 'effective' kinetic scheme, which is still sufficiently detailed for the prediction of reactions in two-phase flow. The newly-developed reaction mechanism will be used for the simulation of reactions in the vicinity of a single bubble by the group of Prof. Bothe, TU Darmstadt. Subsequently the calculations will be extended to reactions in bubble swarms by the group of Prof. Froehlich, TU Dresden. These simulations will then be compared with experimental results from our pilot plant bubble column in the second funding period. The flow regime can be varied from non-interacting bubbles to more turbulent types of flow by an increase of gas holdup.
Institut für Chemische Verfahrenstechnik
Prof. Dr.-Ing. Ulrich Nieken
Sebastian Gast, M.Sc.