Design of reactive distillation for acetic acid esterificaction

Design of Reactive Distillations for Acetic Acid Esterification
Yeong-Tarng Tang, Yi-Wei Chen, Hsiao-Ping Huang, and Cheng-Ching Yu Dept. of Chemical Engineering, National Taiwan University, Taipei 106-17, Taiwan Shih-Bo Hung and Ming-Jer Lee
Dept. of Chemical Engineering, National Taiwan University of Sci. Tech., Taipei 106-07, Taiwan DOI 10.1002/aic.10519 Published online April 21, 2005 inWiley InterScience (www.interscience.wiley.com).

The reactive distillation provides an attractive alternative for reaction/separation processes with reversible reactions, especially for etherification and esterification. The discrete nature of chemical species and the complexity of phase equilibria seem to cloud the picture in understanding reactive distillation. The esterifications of acetic acidwith five different alcohols, ranging from C1 to C5, are studied. First, qualitative relationships between macroscopic process flowsheet and microscopic phase equilibria are established, and the process flowsheets are classified into type I, II, and III for these five systems. Next, a systematic design procedure is devised to optimize the design, based on the total annual cost (TAC) and dominant designvariables are identified for different flowsheets. Once quantitative design is available, process characteristic are analyzed and potential problems in process operation are identified. Finally, the economic potentials of these three different flowsheets are explored and explanations are given. The results clearly indicate that it is possible to systemize the design of reactive distillation byqualitatively generating flowsheet from phase equilibria and by quantitatively completing the process flow diagram from a sequential design procedure. Moreover, some of the flowsheets presented in this work cannot be found elsewhere in the open literature. © 2005 American Institute of
Chemical Engineers AIChE J, 51: 1683–1699, 2005

Keywords: esterification, acetate, reactive distillation, process designIntroduction
Reactive distillation provides an attractive alternative for process intensification, especially for reaction/separation systems with reversible reactions. The literature in reactive distillation has grown rapidly in recent years and the books by Doherty and Malone1 and Sundmacher and Kienle2 give updated summaries in the field. Taylor and Krishna3 give an in-depth review onpotential advantages and hardware configCorrespondence concerning this article should be addressed to C.- C. Yu at ccyu@ntu.edu.tw.

© 2005 American Institute of Chemical Engineers

urations. As pointed out by Doherty and Buzad,4 the concept of combining reaction and separation has long been recognized, but rarely put into commercial practice, not until the successful application for the productionmethyl acetate.5 Despite clear advantages of simultaneous reaction/separation,6 commercializing of reactive distillation processes is still quite limited for several reasons. An obvious one is mentioned in4 “There is almost always a conventional alternative to reactive distillation which is seductive because we have always done it this way”. The scenario remains more than a decade later. After themanagement and technical levels were convinced by the clear edge of reactive distillation, another reason is that the process flowsheets seem to change from case to case (for example,
Vol. 51, No. 6 1683

AIChE Journal

June 2005

from methyl acetate, to ethyl acetate, to butyl acetate and so on).5,7,8,9,10,11 Even for the same chemical production (for example, ethyl acetate, butyl acetate,and so on), the flowsheet configurations also vary8,9,10,11 as one went through the literature. Unlike the conventional distillation, the seemingly casebased design approach and a great deal of process configurations (to choose from) add additional complexity to reactive distillation. A number of chemical systems have been studied in the literature using reactive distillation columns and among the...