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Design method for kinetically controlled, stagewise reactive distillation columns

Matthew Joseph Okasinski, University of Massachusetts Amherst


Within the last decade, reactive distillation has become increasingly attractive as a potential process alternative for simultaneously conducting liquid-phase reaction and vapor-liquid separation, with the potential to overcome chemical equilibrium limitations and to simplify flowsheets. This dissertation develops a systematic steady-state design methodology for kinetically controlled, stagewise reactive distillation columns, taking into account a single isomolar or non-isomolar liquid phase reaction, heat effects, nonideal vapor-liquid equilibrium, and a distribution of liquid holdups on the reactive stages. “Kinetically controlled” means that chemical reaction equilibrium is not obtained on every tray, although vapor-liquid equilibrium is assumed. “Stagewise” implies a column consisting of discrete trays. The method is useful for developing a spectrum of feasible designs over a range of design conditions, which provides insight into the effect of such variables as reboil ratio, heat of reaction and Damkohler number on the total number of stages. The method is demonstrated by developing feasible column designs for the dehydration of methanol, the metathesis of 2-pentene, and the production of ethylene glycol. The influence of azeotropes on the design of ordinary distillation columns has been widely studied for many years. Azeotropes alter product distributions and attainable regions; cause distillation boundaries to occur; and have led to the creation of extractive and azeotropic distillation technology. It can be expected that reactive azeotropes have a similar impact on reactive distillation design. However, the influence that key physical property parameters (such as the reaction equilibrium constant) exert on reactive azeotropes is relatively unknown. New tools are needed to determine when reactive systems will exhibit reactive azeotropes and how these azeotropes will influence designs. Such a tool is described in this dissertation: an arc-length continuation technique used to determine the existence and location of both homogeneous and heterogeneous reactive azeotropes in an equilibrium reactive system. Using the techniques and methods developed, the use of reactive distillation in nontraditional applications are explored, such as in a system possessing a small reaction equilibrium constant (Keq [special characters omitted] 1) or kinetically resolving enantiomers from a racemic mixture.

Subject Area

Chemical engineering|Chemistry

Recommended Citation

Okasinski, Matthew Joseph, "Design method for kinetically controlled, stagewise reactive distillation columns" (1998). Doctoral Dissertations Available from Proquest. AAI3013656.