General Chemistry and Process

Esters are made by reacting carboxylic acids with alcohols. The elimination of water is shown by the following equation  

The reaction proceeds by heating the mixture to 150°C or higher with or without a catalyst . Catalysts such as p-toluenesulfonic acid or titaniimi(IV) isopropoxide, are typically used to facilitate reaction rates. The reaction is driven to completion by continuous removal of water from the reaction medium. Sometimes, one component is used in a slight excess to ensure complete conversion. The final product is purified over an adsorbent to remove trace water and acids, both of which are detrimental to base stock quality. Commercially, esters are generally produced by batch processes. 

The choice of acid and alcohol determines the ester molecular weights, viscometrics and low temperature properties, volatility, lubricity, as well as the thermal, oxidative and hydrolytic stabilities. The structure-property relationships of ester base stocks are well documented in the literature. Compared to PAO and mineral oil, ester fluids have a higher degree of polarity, contributing to the following unique properties  

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