(476f) Process Alternatives for the Direct Esterification of Fusel Oil By Reactive Distillation

César Augusto Sánchez-Correa, Alvaro Orjuela, Iván D. Gil, Gerardo Rodríguez

Grupo de Procesos Químicos y Bioquímicos,

Departamento de Ingeniería Química y Ambiental

Universidad Nacional de Colombia Sede Bogotá

Fusel oil (FO) is a mixture of linear and branched alcohols, ranging from ethylic to isoamylic, obtained as byproduct of bioethanol industry. Typically, around 1-11 L of FO are generated per each 1000 L of anhydrous ethanol produced [1], [2]. In countries where the bioethanol plays an important economic role (e.g USA, Brazil, China, etc), the valorization of FO is an important issue regarding the sustainability of the whole process, and also an opportunity for creating new value-added products for different market niches.

An alternative process to upgrade FO into more-valuable byproducts is the conversion into esters, which are used mainly as flavoring, fragrances and solvents. There are two main processing alternatives for the esterification of fusel alcohols [3], [4]: 1) the indirect process that consists in the separation of the individual FO alcohols followed by their esterification with a carboxylic acid, and 2) the direct process that consists in the simultaneous reaction of the whole FO alcohol mixture with a carboxylic acid. In the first case, only single esterifications (one-acid to one-alcohol at a time) occur and they can be independently studied. However, when directly reacting the fusel mixture, the chemistry of the process is more complex as it is necessary to consider simultaneous esterification reactions.

Because the isoamyl alcohol is the major component in FO, most literature reports dealing with FO upgrading have focused on the production of iso-amyl esters [5]â??[7]. In the case of FO direct esterification, the process is less developed partly because the numerous interactions that must be considered in terms of thermodynamic and kinetic modeling. For example, when modeling simultaneous esterification of acetic acid with FO (consisting of a mixture of three alcohols), a higly non-ideal thermodynamic model (e.g. activity-based model) is required for the evaluation of the chemical and phase equilibria, taking into account the 8 components in the mixture (three alcohols, three esters, acetic acid, and water). In such system, several binary and ternary azeotropes and also liquid-liquid behavior are observed.

In this work several process alternatives for the direct esterification of the FO using reactive distillation were synthetized and designed with the aid of the geometrical tools based in the reactive residue curve maps. For this purpose the previous works were updated in three directions: 1) the existent thermodynamic model [4] was improved by the addition of new experimental vapor liquid equilibrium data for the binary mixtures of acetates and the quality assessment for the previous reported data, 2) new experimental kinetic data on the ion exchange resin Amberlyst 70 were used to fit a kinetic model that is useful at the distillation operation conditions and 3) sequences of two and three columns thermally coupled (or coupled in the decanter) were considered during the analysis.

At the end of this work we conclude that is possible convert completely the fusel oil in anhydrous mixtures of acetates that can be used as solvent base in the paint synthesis or for the straightforward production of pure acetates. On the other hand, we contribute with the refinement of the available geometrical techniques (shortcuts) for sequencing of columns in reactive distillation process with multiple esterification reactions. Finally, results also confirmed that the simple sequential procedure, where the synthesis and design are based in the geometrical analysis of the residue curve maps, is a powerful tool that providing good approximations to the rigorous calculations in a simulator.

References

 

[1] A. G. Patil, S. M. Koolwal, and H. D. Butala, â??Fusel oil: Composition, removal and potential utilization.,â? Int.Sugar J., vol. 104, no. 1238, pp. 51â??58, 2002.

[2] M. C. Ferreira, A. J. A. Meirelles, and E. A. C. Batista, â??Study of the Fusel Oil Distillation Process,â? Ind. Eng. Chem. Res., vol. 52, no. 6, pp. 2336â??2351, Feb. 2013.

[3] P. Patidar and S. M. Mahajani, â??Esterification of fusel oil using reactive distillation â?? Part I: Reaction kinetics,â? Chem. Eng. J., vol. 207â??208, pp. 377â??387, Oct. 2012.

[4] P. Patidar and S. M. Mahajani, â??Esterification of Fusel Oil Using Reactive Distillation. Part II: Process Alternatives,â? Ind. Eng. Chem. Res., vol. 52, no. 47, pp. 16637â??16647, Nov. 2013.

[5] B. Saha, H. Teo, and A. Alqahtani, â??iso-Amyl acetate synthesis by catalytic distillation,â? Int. J. Chem. React. Eng., vol. 3, no. A11, pp. 1â??14, 2005.

[6] W. Osorio-Viana, H. N. Ibarra-Taquez, I. Dobrosz-Gómez, and M. Á. Gómez-García, â??Hybrid membrane and conventional processes comparison for isoamyl acetate production,â? Chem. Eng. Process. Process Intensif., vol. 76, pp. 70â??82, Feb. 2014.

[7] F. Leyva, A. Orjuela, A. Kolah, C. Lira, D. Miller, and G. Rodríguez, â??Isoamyl propionate production by reactive distillation,â? Sep. Purif. Technol., vol. 146, pp. 199â??212, May 2015.