Identification and quantification of steryl glucosides in biodiesel

Abstract

This paper discusses the nature and the chemical identification of a white, solid and insoluble residue isolated during the production of biodiesel, using palm or soybean oil as starting material. Using different isolation, purification and characterisation techniques, the solid was identified as a mixture of phytosteryl glucosides. A simple method for the quantitative evaluation of steryl glucoside (SG) concentrations in biodiesel samples is presented and discussed. Some preliminary results about the average concentration in biodiesel and about the solubility limits of SG are presented. The final section of this paper is dedicated to the impact of different crude oil refining techniques before the biodiesel synthesis reaction on the final SG concentration in biodiesel.

Biodiesel production, properties, and feedstocks

“…3) in biodiesel is problematic because they result in significant low-temperature operability issues at temperatures above CP (Bondioli et al 2008;Hoed et al 2008;Moreau et al 2008). Steryl glucoside precipitates, which form after production of biodiesel, cause engine failure due to fuel filter plugging Pfalzgraf et al 2007).…”

Nature of some insoluble materials recovered from biodiesel samples

“…It was therefore concluded that the white insoluble precipitate comprised steryl glucosides (SG). A more detailed description of these laboratory techniques, of all issues related to the SG quantification and problems was published recently [8]. The presence of a precipitate caused by SG is an oil-related problem, mainly derived from the use of soy and palm oil as feedstocks.…”

“…Using a GLC analysis carried out under the experimental conditions of EN 14105:2003, a family of peaks showing a retention time between that of diglycerides and sterol esters was detected. A portion of the solid sample was then treated with gaseous 1 N HCl in methanol for 16 h at 80 7C in a sealed vial [8]. After elimination of methanol and acid, the sample was TMS-derivatised and injected again into the same chromatographic system.…”

Biodiesel: Current Trends and Properties

“…On the other hand, mononacylglycerols (and free fatty acids) possess excellent lubricity and are likely to a large part responsible for the lubricity of low-level blends of biodiesel with petrodiesel [67]. As another example, recently sterol glucosides (SG), which have high melting points ([240°C) and limited solubility in biodiesel, have been identified as a cause of precipitates forming when storing biodiesel in the cold or sometimes even at ambient temperature [69][70][71]. Minor constituents influencing biodiesel fuel properties may exist in biodiesel made from all feedstocks, including alternative feedstocks.…”