(669g) Incremental Model Identification of Reaction and Mass Transfer Kinetics In a Liquid-Liquid Reaction System – An Experimental Study

Due to the efficient product separation and catalyst immobilization, multi-phase catalytic systems are favoured in industrial applications [1]. Nevertheless, it is usually difficult to decouple reaction and mass transfer kinetics such that the experimental determination of reaction kinetics is masked by mass transfer effects. A novel incremental identification methodology tailored to homogeneous reaction systems [2] and extended to multi-phase systems in previous works [3] allows for the decoupling of reaction kinetics and mass transfer and thus avoids the uncertainty in reaction kinetics identification by construction. While the method has been demonstrated in a simulation case study before [3] it is applied in a real experimental study of a multiphase system for the first time in this work.

The chemical system studied comprises a Friedel Crafts acylation of anisole [4]. It follows a complex catalytic reaction mechanism with two reactants and two products. Several reaction rate models, both elementary and complex, were analyzed. The quality of the candidate models has been assessed by the residual sum of squares (RSOS) serving as an objective function and the Akaike Information Criterion (AIC). Optimal experiments were designed to improve model quality using a novel AWDC criterion [5]. It was found out that a reaction rate model comprising only two rate constants for the forward and backward reactions respectively fits the best with a small confidence interval in contrast to the suggested mechanism in literature [6].

Since, mass transfer and chemical reaction can be systematically decoupled in the identification procedure, the best fitting mass transfer rate model of the 4 species involved can also be determined from the same experimental data set. Several mass transfer models of increasing complexity [7] were tested. Our preliminary results show that a simple model which neglects the diffusion cross effect fits the experimental data best. An optimal design of experiments will be conducted next to improve the reliability of the mass transfer model.

References:

[1] Cornils B, Hermann WA, Vogt D, Horvath I, Olivier-Bourbignion H, Leitner W, Mecking S. Multiphase Homogeneous Catalysis. Wiley-VCH, 2005.

[2] Brendel M, Bonvin D, Marquardt W: Incremental identification of kinetic models for homogeneous reaction systems. Chemical Engineering Science, 2006, 61, 5404-5420

[3] Michalik C, Brendel M, Marquardt W: Incremental identification of fluid multi-phase reaction systems. AlChE Journal, 2009, 55(4), 1009-1022

[4] Zayed F, Greiner L, Schulz P S, Lapkin A, Leitner W: Continuous catalytic Friedel–Crafts acylation in the biphasic medium of an ionic liquid and supercritical carbon dioxide. Chemical Communication, 2007, 79-81.

[5] Michalik C, Stuckert M., Marquardt W: Optimal experimental design for discriminating numerous model candidates - The AWDC Criterion. Industrial & Engineering Chemistry Research, 2009, 49(2), 913-919

[6] Dzudza A, Marks J: Lanthanide triflate-catalyzed arene acylation . Relation to classical Friedel-Crafts acylation. The Journal of Organic Chemistry, 2008, 73(11), 4004-4016

[7] Taylor R, Krishna R. Multicomponent Mass Transfer. New York: Wiley, 1993