1 Introduction

Reactive distillation, as the name implies, refers to a distillation process that incorporates a reaction and a separation step within a distillation column. The technique offers a key opportunity for improving the structure of a process. ^{[1] , [2]} It is a so-called hybrid process, i.e. it merges two different unit operations in a single apparatus, namely reaction and distillation. But the combination of distillation and reactions is possible only if the conditions of both unit operations can be combined. This means that the reactions have to show reasonable data for conversions at pressure and temperature levels that are compatible with distillation conditions. Because of the limited hold-up in distillation column, those reactions having a conversion half-time of 10 30 min are preferred. So, the judicious use of the chemical equilibrium constant is the basis for the design of reactive distillation processes.

The advantages of reactive distillation as compared to a reaction plus a separate distillation process are:

• a reduction of the investment,

• a simpler process,

• the use of the heat of reaction (if present) in situ,

• ease of control of the reaction temperature (evaporating system), and

• the possibility of overcoming azeotropes.

A typical reactive distillation set-up is depicted in Figure 1.

Figure 1: The basic elements of a reactive distillation column

The high boiling reactant is fed as feed 1 and the low boiling reactant as feed 2. Between the two feeds, there is the reaction zone. As a special application,...