(95b) Innovative Process Intensification for Extreme Challenges

The esterification of methanol with acetic acid by Reactive Distillation (RD) was reported for the first time in U.S. patent 1400849 [1]. Eastman started in 1984 large scale production of methyl acetate in a single RD column. Despite the formation of minimum boiling azeotropes and equilibrium limited reaction, the top product was high purity methyl acetate.

Forty years after Eastman developed their process by RD, there is still no similar large-scale process for production of high purity ethyl acetate. Many authors reported simulations or experiments for production of ethyl acetate by RD with limited performance, for example 65% purity [2], or higher performance with suspicious thermodynamic data [3].

This paper presents conceptual design and simulation of a RD process for high purity ethyl acetate taking the advantages of Dividing Wall Columns (DWC). There are extra features to the traditional Eastman RD process, as follows:

1. Using an excess of acetic acid to shift chemical equilibrium to high ethanol conversion above 99%. The acetic acid is the lowest volatile component of the reactive quaternary mixture, therefore it is separated as the bottom product and recycled to the top or reaction section.
2. Separation of water as side stream. A dividing wall at the bottom of the column allows water stripping, condensation and separation. The excess of acetic acid allows water extraction, preventing water-based azeotropes separation at the top of the column.
3. Separation of ethyl acetate as side stream. A second dividing wall at the top of the column allows stripping the lights components and separation of high purity ethyl acetate. The lights separated from the top of the column are recycled back below the reaction section.
4. Heat integration of the condenser required for the 1st dividing wall with the reboiler of the 2nd dividing wall. Internally Heat-Integrated Distillation Column (HIDiC) concept can be used in design since both reaction products require further purification, one by rectification and by stripping.

Contrary to the Eastman process where the ester is separated in the top of the column and the water in the bottom, this state-of-the-art design is based on both reaction products separation as side streams. A benefit of this design is also the possibility to recycle the homogeneous catalyst (e.g. H₂SO₄) with the acetic acid reactant, while in the Eastman process the catalyst is lost with the water product.

References:

[1] V.H. Agreda, L.R. Partin, Reactive Distillation Process for the Production of Methyl Acetate, U.S. Patent 4 435 595, 1984.

[2] J. Leon-Pulido, M. P. Sarmiento, Diego M. Garzon, M. A. Hernándeza, A. Darío Gonzalezc, Y. Y. Peralta-Ruizd, M. Durane, Energy Study of Reactive-HIDiC Simulation for Ethyl Acetate Synthesis from Acetic Acid, Chemical Engineering Transactions, 58, 2017, 547-552.

[3] C. Chilev, E. Simeonov, Reactive Distillation for Ethyl Acetate Production, Journal of Chemical Technology and Metallurgy, 52, 3, 2017, 463-474.