OPTIMIZATION OF CATALYZED EPOXIDATION OF UNSATURATED FATTY-ACIDS BY USING TENDENCY MODELS

Significant economic benefits can be realized by optimizing the operation of batch/semibatch processes even when a detailed understanding of the process fundamentals (stoichiometry, kinetics etc.) is not available. The present study investigates the application of a general purpose modeling and optimization approach, called "Tendency Modeling", to the catalyzed epoxidation of oleic acid. The selection of this reaction was motivated by its complexity, some knowledge of kinetics under limited range of operating conditions (Kuo and Chou, 1987), selectivity losses, and its exothermicity. Experimental data obtained from a pilot plant facility are used to test the proposed modeling approach. The "Tendency Model" of the process is a low order, nonlinear, and dynamic model. It consists of approximate stoichiometric, kinetic and thermodynamic models obtained by fitting the available plant data, coupled with fundamental material and energy balances. This approximate model is used to optimize the process in an evolutionary manner according to a prespecified economic criterion. In the present paper, we report the development of an approximate stoichiometric model for the epoxidation process, a first step in the process optimization. A 2-level fractional factorial design is implemented to collect data for model identification. The approximate stoichiometric model is obtained by factor analysis of an appropriately scaled concentration data matrix to determine the number of independent reactions and to identify the reaction invariants which can be linearly combined to obtain an approximate, but more realistic reaction network. A detailed free radical mechanism consisting of 11 reactions has been proposed for the epoxidation process (Kuo and Chou, 1987). Our results indicate that a simpler model consisting of two or three overall reactions can satisfactorily explain the observed data. © 1990.