Improved sustainable ionic liquid catalyzed production of symmetrical and non-symmetrical biological wax monoesters

Abstract

Biological wax esters are important commercial products used in various industrial and medicinal fields. These valuable compounds can be synthesized via several chemical and enzymatic reactions which have some advantages and more disadvantages. In particular, many strong acid catalysts cause undesirable structural changes in unsaturated fatty acids molecules. In the present study, easily accessible 1-hexadecyl-3-sulfoimidazolium chloride as an ionic liquid is screened as a mild Bronsted acid metal free catalyst for the chemical esterification, or transesterification, of equimolar amounts of long chain fatty acids or fatty acid methyl esters, respectively, with fatty alcohols in a solventless medium. The various parameters affecting the yield of the wax ester are optimized, catalyst reuse studies, and large scale synthesis are also carried out. According to this alternative practical and green process, a series of wax esters (17 examples) are produced readily in good to excellent yields. There is no undesirable geometric cis-trans isomerization in unsaturated fatty acids under the reaction conditions used. The catalyst is also quite effective when triglycerides are converted directly to the wax esters via transesterification reaction. Practical Applications: With an effortless and environmentally friendly method developed in this study, various wax esters can be synthesized as valuable industrial materials. In order to synthesis these esters, there is not any restriction for starting compounds. The most important aspect of the developed procedures is that metallic or strong aggressive acidic catalysts are not used compared to existing procedures. It is possible to carry out large-scale syntheses of esters with high yields. In the present study, a series of industrial and medical important wax esters are synthesized from renewable sources in a solvent-free environment using IL-catalyzed environmentally friendly methods.