Selected physical properties of binary mixtures of crude glycerol and methanol at various temperatures Reza Afshar Ghotli, Abdul Raman Abdul Aziz *, I.M. Atadashi, D.B. Hasan, Pei San Kong, M.K. Aroua Department of Chemical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia 1. Introduction Biodiesel (or methyl esters) is a clean and biodegradable alternative to petroleum-based diesel fuel. The most common method to produce biodiesel is catalytic transesterification of vegetable oils and animal fats using a homogeneous acid or base catalyst in stirred reactors [1]. In the transesterification reaction, triglyceride reacts with alcohol, producing a mixture of fatty acids; alkyl esters and glycerol (see Fig. 1). Different homogeneous catalysts such as potassium hydroxide [2], sodium hydroxide [3], sodium ethoxide [4], sodium methoxide [4], sulfuric acid [5] and hydrochloric acid [6] are used. Despite many benefits from the production and use of biodiesel, there are also challenges involved such as the use of byproducts generated in the transesterification process. Glycerol is the main transesterification byproduct. There is about 1 kg of a crude glycerol byproduct is formed for every 9 kg of biodiesel produced [7]. Glycerol, or 1,2,3-propanetriol, is a trihydric alcohol. It is a colorless, odorless, sweet-tasting, syrupy liquid that melts at 17.8 8C, boils at 290 8C, and is miscible with water and ethanol [8]. Since biodiesel production is increasing rapidly, crude glycerol as the by-product of the production process is also generated in large quantity. Thus, conversion of crude glycerol to value added products can reduce the price of biodiesel. The crude glycerol by- product can be converted to many useful products including 1,3- propanediol [9], 1,2-propanediol [7], dihydroxyacetones [10], hydrogen [11], polyglycerols [12], succinic acid [13], and polyesters [14]. The quality of crude glycerol generated from biodiesel production is low, and therefore, it should not be used directly. Hence, further refining and purification of the crude glycerol is necessary [15]. Generally, crude glycerol treatment consists of filtration, chemical additions, fractional vacuum distillation, bleaching, deodorization, and ion exchange. The impurities in crude glycerol include methanol and soaps. As a result of the application of excess methanol to enhance biodiesel production, methanol is present in the glycerol byproduct. Due to the presence of free fatty acids in the oil feedstock, soap can exists in the glycerol layer. In addition to methanol and soap, crude glycerol may also contain a variety of elements such as calcium, magnesium, phosphorous, or sulfur [16]. It has been reported that glycerol makes up 65% to 85% (w/w) of the crude glycerol streams [17,18]. The remaining weight in the crude glycerol streams is mainly methanol and soaps [16]. Physiochemical properties of the crude glycerol mixtures are fundamental variables that need to be considered for the design of industrial equipment for purification or conversion of crude glycerol to other products. The properties such as density and viscosity are needed to determine behavioral and predictive information to design and optimize the unit operations. Density, Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx * Corresponding author. Tel.: +60 379675300; fax: +60 379675319. E-mail addresses: azizraman@um.edu.my, rshazrin@gmail.com (A.R. Abdul Aziz). A R T I C L E I N F O Article history: Received 17 January 2014 Received in revised form 9 May 2014 Accepted 12 May 2014 Available online xxx Keywords: Glycerol Dynamic viscosities Densities Excess molar volumes Refractive indexes A B S T R A C T Crude glycerol, the main byproduct of biodiesel production, consists of excess methanol and other impurities and can be converted into other useful products through purification or conversion processes. In this work, dynamic viscosities, densities, excess molar volumes and refractive indexes for several mixtures of biodiesel crude glycerol and methanol with were determined at different temperatures. The physiochemical characteristics of crude glycerol in mixture form with methanol could be useful for the design of industrial equipment and purification or conversion process. The results demonstrated temperature dependent behaviors of all binary mixtures. The empirical correlations were obtained based on the experimental results. ß 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. G Model JIEC-2040; No. of Pages 5 Please cite this article in press as: R. Afshar Ghotli, et al., J. Ind. Eng. Chem. (2014), http://dx.doi.org/10.1016/j.jiec.2014.05.013 Contents lists available at ScienceDirect Journal of Industrial and Engineering Chemistry jou r n al h o mep ag e: w ww .elsevier .co m /loc ate/jiec http://dx.doi.org/10.1016/j.jiec.2014.05.013 1226-086X/ß 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.