Production of Esters

Esters are produced by reacting alcohols with organic acids. The reaction is reversible and therefore unless one of the products is removed, the ester yield is limited. Assuming the reaction is equilibrium-limited and not rate-limited, higher conversions can be obtained by removing one of the products. For instance, if during the reaction the water is removed, the reaction will be driven by equilibrium to produce more ester product. High purity esters can be produced with azeotropic distillation to simultaneously remove water and alcohol from the esters using aromatic and aliphatic hydrocarbons as entrainers.

Mato Vazquez et al. found isobutyl acetate, «-butyl acetate and zsoamyl acetate could be purified using an entrainer such as «-heptane, methyl cyclopentane or various other hydrocarbons to simultaneously remove the water and alcohol. The reaction products are fed to an azeotropic column where the entrainer is used to remove the alcohol and water as overhead

Figure 7 Typical ethanol dehydration process using azeotropic distillation.

products. Final purification of the ester product is carried out in a rectification column with only a few stages. The entrainer is recovered using a one-step liquid-liquid extraction (LLE) column with water as the extractant.

Wuest et al. found they could prepare ethyl chloro-acetate by addition of ethanol to a melt of chloro-acetic acid and p-toluene sulfonic acid and purify the ester product using azeotropic distillation. The ester and water form a minimum boiling binary azeotrope and therefore affect the ester/alcohol separation. Water and ethyl chloroacetate are removed overhead and the product is decanted. In this manner the ester is practically alcohol-free. This process avoids formation of the ternary ester/alcohol/water azeotropes which are difficult to separate.

Hills et al. found that azeotropic distillation is useful in the purification of esters produced using an enzymatic route. For example, isopropyl myristate can be prepared with lipase or immobilized lipase from myristic acid and propane-2-ol. The water produced in the reaction is removed by azeotropic distillation.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

Get My Free Ebook


Post a comment