The esterification reaction of acetic acid with n-butanol in a continuous catalytic distillation system has been studied. The products of esterification reactionsviz, water and butyl acetates are separated by distillation during the course of the reaction, to overcome the equilibrium limitations. A 3-m-tall column with reactive and nonreactive zones, packed with a commercial catalytic packing (KATAPAK-S) and noncatalytic wire gauze packing, was used for this purpose. For a feed concentration corresponding to that obtained in a one-stage continuously stirred tank reactor at reaction equilibrium, conversion of ∼100% was realized, with selectivity on the order of 99%. Interestingly, in most of the experiments, the bottom stream contained butyl acetate that was almost free of acetic acid. The influence of various operating parameters, such as feed flow rate, feed composition, feed location, and boil-up rate, on the conversion, selectivity, and separation was studied. A dynamic equilibrium stage model was developed and solved to predict the transient and steady-state results. Reasonably good agreement between the experimental and simulation results was realized.

The recovery of acetic acid by reactive distillation through esterification with methanol in the presence of ion-exchange resin as a catalyst has been investigated in detail. A kinetic expression that is valid under the conditions that prevail in a continuous reactive distillation column has been developed. The insensitivity of reaction rate to catalyst loading under certain conditions has been addressed. The recovery as high as 80% was realized experimentally for the feed concentration of 30% (w/w) in a laboratory column. Various alternative scenarios such as effect of reboiler duty, feed flow rate, and feed composition were covered in the experiments. The equilibrium stage model for reactive distillation predicts the performance well in agreement with the experimental results. The effect of changing various design and operating parameters, over a wide range, was also studied through simulation. The model predicts close to quantitative recovery (∼100%) with a properly designed column. Some feasible alternative configurations for a complete recovery system have been suggested.

The paper presents a parametric study for the design of a reactive distillation column used to recover acetic acid from dilute aqueous solution (30% w/w) through the formation of methyl acetate. The parameters such as feed molar ratio, feed location, reflux ratio, and reboil ratio are varied by a one-parameter continuation method, and the best possible configuration is suggested. Close to quantitative recovery may be obtained by a proper choice of parameters, and reactive distillation can be successfully used for the recovery process. An experimental support is provided to the recommended configuration. The system is highly nonlinear, and solution multiplicity is realized in a certain parametric space. Apart from input parameters, a possible role of modeling assumptions, kinetics, and phase equilibrium models on multiplicity has been discussed.

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