Mixed succinic acid/acetic acid esterification with ethanol by reactive distillation

Abstract

Esterification of mixtures of succinic acid and acetic acid, commonly produced via fermentation of biomass carbohydrates, with ethanol in a continuous reactive distillation unit has been studied. Experiments were carried out in a 6 m tall, 51 mm diameter pilot-scale stainless steel column with the reactive zone consisting of Katapak-SP11 structured packing containing Amberlyst 70 cation exchange resin as catalyst. Noncatalytic BX structured gauze packing was used in stripping and enrichment sections. Steady-state experiments were performed under different conditions by varying the composition and number of inlet streams, the column pressure, the reboiler power, and the reflux ratio. Conversions approaching 100% for both succinic acid and acetic acid were verified experimentally; succinate esters were obtained as bottom products with purities of diethyl succinate as high as 98%, and ethyl acetate was recovered in the distillate. Computer simulations based upon experimental phase equilibrium data and chemical kinetics were performed in Aspen Plus using RadFrac to reproduce steady-state results. Good agreement between experiment and simulation was observed under diverse operating conditions. The model developed here can be used to design commercial-scale systems for succinic acid production when acetic acid is also formed during the fermentation. © 2011 American Chemical Society.