Purification of glycerol from biodiesel production by sequential extraction monitored by 1 H NMR Ignacio Contreras-Andrade a,1 , Eliseo Avella-Moreno b,2 , Jonathan Fabián Sierra-Cantor b,3 , Carlos Alberto Guerrero-Fajardo b,3 , José Ricardo Sodré c, ⁎ a University of Sinaloa, Department of Biology and Chemistry, Blvd. Universitarios y Blvd. de las Américas, Culiacán 80007, Sinaloa, Mexico b Universidad Nacional de Colombia, Department of Chemistry, Av. Carrera 14 # 127-25, Cundinamarca, 11001 Bogotá, Colombia c Pontifical Catholic University of Minas Gerais, Department of Mechanical Engineering, Av. Dom José Gaspar, 500, CEP 30535-610, Belo Horizonte, MG, Brazil abstract article info Article history: Received 29 June 2014 Received in revised form 9 December 2014 Accepted 11 December 2014 Available online xxxx Keywords: Glycerin Biodiesel 1 H NMR spectroscopy The purification of raw glycerin in biodiesel production can provide economic benefits and help to avoid residue accumulation, thus reducing environmental impacts. In this work, the glycerin obtained from biodiesel production by catalytic transesterification of waste cooking oil was purified by sequential extraction with organic solvents, followed by discoloration with activated coal and monitoring by 1 H NMR spectroscopy. Through sequential extraction with petroleum ether and toluene, in that order, followed by discoloration with activated carbon, 99.2% pure glycerin was obtained. This technique is shown to allow for glycerin purification using less drastic or hazardous conditions than those commonly applied in vacuum distillation. © 2014 Elsevier B.V. All rights reserved. 1. Introduction In recent years the production of biodiesel has been increased due to high demand for diesel oil replacement. According to the International Energy Agency (IEA) report, biodiesel production has increased tenfold from 2000 to 2011 and has since doubled, close to 21.8 billion liters in 2012 [1]. The main cost in the biodiesel production process is the oilseed, which accounts for 60% to 75% of the total sum and can cause high economic volatility by competing with food if it is an edible source [2]. Many research efforts are dedicated to the development of biodiesel production processes using waste cooking oil as raw material, once this source can be a solution to enhance biodiesel competitiveness [3]. Two main alternatives have been applied to produce biodiesel from waste cooking oil at industrial scale: the conventional alkaline homogeneous transesterification process and two-step esterification– transesterification homogeneous process (Fig. 1). In these processes the waste cooking oil should be pretreated to eliminate the high free fatty acid content, by neutralization or esterification, water content, by drying or distillation, and the presence of solid or colloids, by filter- ing or centrifugation. Other alternatives could be heterogeneous or enzymatic catalyzed or non-catalyzed processes, which can include technologies like reactive distillation, membrane reactor, ultrasonic assisted, etc. [4–8]. The biodiesel production process by methyl transesterification pro- duces two phases. The upper phase contains biodiesel and the lower phase (without methanol) contains raw glycerin of 55–90 wt.% purity [9]. This heavy phase represents 10 wt.% of the total production and con- sists of glycerin and other materials [10–12]. Depending on the raw ma- terial, biodiesel production process and post-treatment of the raw glycerin, its composition can change considerably. The composition of raw glycerin includes methanol, water, salts (classified as ash) and free fatty acids (FFAs), soaps, fatty acid methyl esters (FAMEs) and glycerides, normally known as MONG (Matter Organic Non-Glycerol) [13,14]. Waste glycerin from biodiesel production has found use as an improver of wastewater sludge process performance [15]. Glycerin, or glycerol, finds several applications in the manufacturing of polymers, medicines, cosmetics and foods, among others, to produce alkyl resins, moisturizing creams and lotions, toothpaste or liquids for mouth cleaning, shampoos, and recently as green solvent and important industrial commodities [16–18]. The application has also been found in the production of biosurfactants [19]. Thus, the recovery of glycerin from the biodiesel production process is attractive for practical use [20]. The most common process of glycerin purification is carried out through vacuum distillation in inert atmosphere. Vacuum distillation can produce glycerol with a purity degree from 95.5% wt. up to 99.5% wt. [21]. In recent years, due to the high cost of the purification process, the industry has preferred not to treat the glycerin produced with biodiesel. Current research investigates several alternatives to convert the Fuel Processing Technology 132 (2015) 99–104 ⁎ Corresponding author. Tel.: +55 31 3319 4911; fax: +55 31 3319 4910. E-mail addresses: ica@uas.uasnet.mx (I. Contreras-Andrade), eavellamo@unal.edu.co (E. Avella-Moreno), jfsierraca@unal.edu.co (J.F. Sierra-Cantor), caguerrerofa@unal.edu.co (C.A. Guerrero-Fajardo), ricardo@pucminas.br (J.R. Sodré). 1 Tel.: +52 667 713 7860. 2 Tel.: +57 1 3165 000. 3 Tel.: +57 1 757 2515. http://dx.doi.org/10.1016/j.fuproc.2014.12.016 0378-3820/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Fuel Processing Technology journal homepage: www.elsevier.com/locate/fuproc