3.1 Esterification

In the case of reactive distillation, total capital cost is reduced due to two combined process steps held in the single unit. This kind of integration is also beneficial in reducing pump cost and other instrumentation cost. The saving in total energy cost is due to exothermic nature of many chemical reactions which in turn are beneficial in providing heat for separation of components simultaneously [3–10]. The schematic diagram of reactive distillation column is shown in Figure 1.

Reactive distillation, which uses heterogeneous catalysts known as catalytic distillation, was firstly considered for RD [11], but it then remained uninvestigated and lacked research interests until the 1980s. However in 1980, with the advent of reactive distillation technology, Eastman Company tentatively carried out synthesis of high-purity methyl acetate. Later on RD was categorized as hybrid and nonhybrid columns [12, 13]. Hybrid RD is used to describe columns, which have separate reactive and separation sections, while the reaction takes place in the whole

After the success story of Eastman Company, several European countries and universities joined forces to work on a development strategy for reactive distillation process under the umbrella of Brite Euram project. Sulzer Chemtech has developed special structured catalytic packing for reactive distillation columns [14]. RD is an

important method for many chemical syntheses which require recovery of chemicals such as recovery of acetic acid. RD uses cation-exchange resin for many liquid-phase homogeneous catalyst reactions such as butyl acetate synthesis and helps in separating catalyst during downstream processing. The investigation of many such reactions is reported [15–17]. Transesterification for synthesis and characterization of biodiesel from different raw material such as palm oil, mustard oil, etc. has been proposed but still not commercialized using various

2. Industrial application of reactive distillation

Schematic diagram of reactive distillation column (RDC).

Distillation - Modelling, Simulation and Optimization

non-hybrid RD column.

92

Figure 1.

In esterification reaction, alcohol and acid react to form an ester. Esters are chemical compounds having pleasant fruity odor.

ROOR' <sup>þ</sup> NaOH➔ROONa <sup>þ</sup> HOR'

The main application of esters is in the synthesis of artificial flavor and essence and solvent for oil, gum, fat, and resins. They are also used as plasticizers. Esterification is the oldest reaction carried out in a reactive distillation column. For example, in conventional methyl acetate production, the yield of methyl acetate is low because of low boiling azeotrope formation. This constraint is removed in RD and almost pure methyl acetate can be collected. Fatty acid esters are natural chemicals used, among other things in cosmetics; plastics and surfactants were also reported to be synthesized in reactive distillation.
