Highly selective production of high purity methyl oleate biodiesel by silver-based deep eutectic solvent extraction

Abstract

High-purity methyl oleate is one of the important oleo-chemical products with a wide range of applications (e.g., biodiesel). In this study, an efficient extraction method based on a silver-based deep eutectic solvent (Ag-DES) has been developed for separating high purity (>98 %) methyl oleate from unsaturated fatty acid methyl esters (e.g., camellia seed oil methyl esters). The rapid extraction method involving silver ions can selectively separate the unsaturated fatty acid methyl esters (FAMEs) by forming C = C double bond complexes with the unsaturated FAMEs. Ag-DES exhibited highly selectivity towards monounsaturated FAMEs (C18:1) and polyunsaturated FAMEs (C18:2, C18:3). The extraction conditions of Ag-DES were optimized and its recyclability was investigated. Under the optimal conditions (room temperature extraction for 10 min), the yield of high-purity methyl oleate (98.5 %) was greater than 60 %, while the selectivity of methyl oleate reached 48.07. The Ag-DES could be successfully recycled for 5 times without loss of extraction selectivity. Thus, this sustainable extraction can provide a simple method for producing a biodiesel with excellent oxidative stability.