Crude glycerine characterization: analysis of free fatty acids, fatty acid methyl esters, and acylglycerides
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ORIGINAL ARTICLE
Crude glycerine characterization: analysis of free fatty acids, fatty acid methyl esters, and acylglycerides Maira Alejandra Maquirriain 1 & Lucas Gabriel Tonutti 1 & Carlos Alberto Querini 1
&
María Laura Pisarello 1
Received: 24 May 2020 / Revised: 11 August 2020 / Accepted: 13 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Crude glycerine is a product obtained in a biodiesel production plant by processing the glycerine phase formed in the transesterification reactor. Crude glycerine contains approximately 80 wt% of glycerine, water, salts, and matter organic nonglycerol. This product is used mainly as a feedstock to obtain high-purity glycerine in a refining unit. Due to a large variability in biodiesel production processes and technologies, the crude glycerine has significant variations in its composition, making it difficult to run the latter process. Particularly, the content of saponifiable matter (free fatty acids, fatty acid methyl esters, and mono-, di-, and tri-acylglycerides) is relevant not only in the refining process, but also in other applications such as bioconversion processes to obtain value-added products. In this work, a method to quantify free fatty acids, fatty acid methyl esters, and mono-, di-, and tri-acylglycerides is presented. The method is based on a quantitative extraction with hexanes, and an analysis by GC with derivatization. It is possible to detect very low concentrations of these impurities. The confidence intervals for each of these impurities have been determined, being the highest for the quantification of the fatty acid methyl esters and mono-acylglycerides. In all cases, the 95% confidence intervals represent an error smaller than 20%. Keywords Glycerine characterization . Saponifiable matter . Glycerine purification . Solvent extraction . Hexanes
1 Introduction Biodiesel is obtained mainly by transesterification of vegetable oils. This process generates as a by-product approximately 10 wt% of glycerine relative to the starting oil [1]. Therefore, many industries that produce biodiesel installed glycerine refining plants, since there are many applications for glycerine of high purity in food, beverages, pharmaceutical, and chemical industries [2]. The glycerine phase formed in the transesterification reaction using alkaline homogeneous catalyst (e.g., sodium methoxide) contains approximately 65 wt% glycerine [3], being the main impurities methanol, catalyst, soaps, and other impurities (water, phospholipids, pigments, etc.) [4, 5]. These values have large ranges of variation depending upon the Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13399-020-00962-0) contains supplementary material, which is available to authorized users. * Carlos Alberto Querini [email protected] 1
Instituto de Investigaciones en Catálisis y Petroquímica (INCAPE) – FIQ – UNL – CONICET, RN168, Km 0, 3000 Santa Fe, Argentina
quality of the raw material (acidity, humidity, phospholipids, un
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