Esko Tirronen

Development of a kinetic model for the esterification of acetic acid with methanol in the presence of a homogeneous acid catalyst

Abstract The esterification kinetics of acetic acid with methanol in the presence of hydrogen iodide as a homogeneous acid catalyst was studied with isothermal batch experiments at 30–60°C. The catalyst concentration was varied between 0.05 and 10.0 wt%. The experiments revealed that besides the main reaction, the esterification of acetic acid, a side reaction appeared: the catalyst, hydrogen iodide, was esterified by methanol to methyl iodide. Plausible reaction mechanisms for methyl acetate and methyl iodide formation were proposed. The rate-determining step in the acetic acid esterification was assumed to be the nucleophilic attack of methanol to the carbenium ion formed through proton donation to acetic acid, whereas the rate-determining step in the hydrogen iodide esterification was presumed to be the substitution of the iodide to protonated methanol. Hydrogen iodide and acetic acid act as proton donors; thus the protolysis equilibria of acetic acid and hydrogen iodide were included in the mechanism. Rate equations, concentration-based as well as activity-based with UNIFAC activity coefficient estimations, were derived, and the kinetic and equilibrium parameters included in the rate equations were estimated from experimental data with regression analysis. Simulation of the models with the estimated parameters revealed that the rate equations predict correctly the experimental trends in the acid catalyzed esterification.

Process development in the fine chemical industry

Abstract Fine chemicals are an important group of products consisting of pharmaceuticals, agrochemicals, dyes, photographic chemicals and intermediates of all these groups as well as chemicals for the textile industry. They are typically high value-added products. The processes for manufacturing these products are mostly batch and semibatch processes. The development of kinetic models for complex chemical reactions occurring in the fine chemical processes and including these models into batch and semibatch reactor models for scale-up are presented in this paper. A methodological approach to the modelling of these complex systems and the estimation of model parameters is proposed. The methodologies were applied to two case studies: reductive N -alkylation of an aromatic amine with homogeneous reactions and a heterogeneously catalysed reactions and Claisen condensation as organic liquid–solid reaction.

Modelling and scale-up of a loop reactor for hydrogenation processes

A dynamic model for the scale-up of semibatch loop reactors was developed. The mathematical model comprises the essential parts of the loop reactor: the reaction vessel, the ejector and the circulation loop. Tanks-in-series and axial dispersion concepts were applied on the description of the non-ideal flow pattern of the reactor. The dynamic axial dispersion model was discretized with finite differences with respect to the spatial coordinate, and the created ordinary differential equations were solved with the backward difference method suitable for stiff differential equations. The loop reactor model was tested with a case study, a homogeneously-heterogeneously catalyzed reaction system, reductive alkylation of aromatic amines. Simulations showed that rate equations obtained from laboratory-scale experiments can be successfully combined to the flow model of the loop reactor: the behaviour of a large-scale loop reactor was predicted with satisfactory accuracy.

A homogeneous-heterogeneously catalysed reaction system in a loop reactor

Abstract Catalytic three-phase reactions including homogeneous liquid-phase steps were simulated in a loop reactor. The loop reactor consisted of a reaction vessel, an external loop as well as an ejector. The loop reactor was modelled using tanks-in-series or alternatively, axial dispersion models. Kinetics of the reductive alkylation of aromatic amines, which was determined from the experiments in a laboratory autoclave, was used for verifying the reactor model and for concentration profile simulations in the loop reactor.

Modelling of complex liquid–solid reaction systems in semibatch reactors: Claisen condensation in industrial scale

Several organic liquid-phase reactions are carried out in the presence of a sparingly soluble reactive solid phase which is gradually dissolved during the course of the reaction. The presence of the reactive solid phase complicates the treatment of kinetic data, since the overall reaction rate is influenced by the solubility equilibrium and mass transfer rate of the solid compound. A mathematical model has been derived for an organic reaction system with one reactive solid compound. The modelling concept was applied on a linear multistep reaction system, Claisen condensation. The solubility of the solid compound was measured under non-reactive conditions and the kinetic parameters for the reaction system were determined from the data obtained with semibatch experiments. Model simulations elucidated the behaviour of the sparingly soluble reactive compound in the process and they indicated that the rate equations describe the experimental kinetic data well.