Chapter 12 - Enhanced distillation types

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This chapter discusses several distillation methods such as homogeneous azeotropic distillation, hetrogeneous azeotropic distillation, and reactive distillation. These techniques rely on the differences between the vapor and liquid compositions, as does ordinary distillation, but an additional mechanism is used to alter the behavior of key components. Homogeneous azeotropic distillation is a technique for separating a mixture by adding an entrainer, which then forms a homogeneous minimum or maximum boiling azeotrope with one or more feed components. Where the components of the mixture are not miscible in all proportions with each other, and form two separate phases at some ratios, the azeotrope is heterogeneous. For heterogeneous azeotropes, the vapor-phase composition is equal to the overall composition of two or more liquid phases. Reactive distillation is a process where a chemical reaction occurs in the still, as it is the integration of reaction and distillation into a single unit where the products can be removed to drive a reversible reaction to completion. Separation of the product from the reaction mixture does not require a separate distillation unit, thus saving energy and materials. This technique is especially favorable for systems where equilibrium reactions occur, such as esterification and ester hydrolysis reactions, but undesirable when one of the desired products decomposes. The chapter also studies certain case studies such as manufacture of methyl acetate and reactive distillation of methyl acetate