Modeling and Simulation of Ethyl Acetate Reactive Distillation Column

Reactive distillation (RD) is an attractive way of improving process economics by
combining distillation and reaction, especially for equilibrium limited reactions such
as esterification. Two of the most studied esterification reactions via RD in the
literature are methyl acetate synthesis and ethyl acetate synthesis. The ideal
performance of the RD column would be to achieve almost complete conversion of
both reactants while at the same time producing pure esters as distillate. From
literature it was found that unlike other RD systems such as MTBE and ETBE, it is
impossible to achieve ideal performance with normal double feed configuration,
though the achieve conversion and purity of these systems are higher than the
conventional method of reaction followed by separation. This is du,e to the formation
of azeotropes between reaction products and reactant, which in tuin hinders the
achievement of complete conversion and producing pure esters as di~tillate.
Researchers had successfully exploit the mixture properties of methyl acetate system
and device a RD configuration known as reactive-extractive distillation (RED)
column that ultimately overcomes the azeotropic conditions in a single column and
hence able to achieve ideal performance for this system. However, the conditions in
ethyl acetate RD column do not allow us to exploit the mixture properties and
furthermore the presence of four azeotropes as compared to two azeotropes in methyl
acetate system complicates the separation process in ethyl acetate RD column.
Thus in this study attention were given to improve the ethyl acetate RD column
performance. Initially, simulation model for esterification of acetic acid by ethanol in
a RD column was developed and verified against equivalent experimental work and
published simulation results. Upon confirming the applicability of the simulation
model, the effects of changing various operating and design parameters on the column
performance were studied in order to explore the possibility of improving the column
performance. Through this analysis it is evident that the column performance could
not be enhanced significantly due to formation of azeotropes between reaction
products and reactant for nearly equal product split at both end of the column.

Finally a new configuration that involves the introduction of extractive zones below
ethanol feed point and above acetic acid feed point with extraneous component as an
extractive agent in the system in order to break one of the azeotropes between product
and reactant, thus allowing the attainment of higher conversion and purity was
proposed. With this configuration the column performance was significantly
improved.