Preparation of water-in-oil and ethanol-in-oil emulsions by membrane emulsification Javier Silvestre de los Reyes, Catherine Charcosset * Université de Lyon, F-69622, Lyon, France Université Lyon 1, Villeurbanne, France CNRS, UMR 5007, Laboratoire d’Automatique et de Génie des Procédés, France ESCPE-Lyon, Villeurbanne, France article info Article history: Received 8 October 2009 Received in revised form 21 June 2010 Accepted 22 June 2010 Available online 6 July 2010 Keywords: Biofuel Ethanol-in-oil emulsions Membrane emulsification Vegetable oil Water-in-oil emulsions abstract In this work, water-in-oil emulsions (W/O) and ethanol-in-oil emulsions (E/O) emulsions were prepared successfully by membrane emulsification. The emulsifiers selected were PGPR and MO-750 for the W/O and E/O emulsions, respectively. For W/O emulsions prepared with an oil pre-filled membrane, the dis- persed flux was lower and the droplet size sharper than that obtained with a water pre-filled membrane. On the contrary, for E/O emulsions prepared with the membrane pre-filled with oil, the dispersed phase (ethanol) rapidly pushed out the oil from the membrane pores. Therefore, the pre-treatment of the mem- brane had almost no effect on the dispersed phase flux and on the droplet size. The droplet size distribu- tion of the E/O emulsion was close to that obtained with a classical homogenizer. The dispersed phase fluxes were high and no fouling was observed for our experimental conditions (1.6 l emulsion, 10 wt% ethanol). These results confirm that membrane emulsification could be an interesting alternative for the preparation of E/O emulsions for the purpose of biodiesel fuels, considering the scale-up ability of membranes and their potentiality for industrial processes. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Recent increases in petroleum price and uncertainties in its availability have increased the interest in renewable fuels [1]. An interesting alternative of the renewable fuels, among others, is the vegetable oil fuel for diesel engine. Considerable efforts have been made to develop vegetable oil derivates that approach the properties and performance of the hydrocarbon-based diesel fuels. The problems with substituting vegetable oil for diesel fuels are mainly associated with their high viscosities, low volatilities and polyunsaturated character. Pyrolysis, microemulsification, dilution and transesterification are the four techniques applied to solve the problems encountered with the high fuel viscosity [2]. Contrary to the transesterification process which is very expensive due to the required specific material, the microemulsification process re- quires only a mechanical stirrer and emulsifiers. To reduce the high viscosity of vegetable oils, microemulsions with immiscible liq- uids, such as methanol, ethanol and ionic or non-ionic emulsifiers have been investigated [2]. Short engine performances of both io- nic and non-ionic microemulsions of ethanol in soybean oil (E/O emulsions) were nearly as good as that of the fuel [3]. Membrane emulsification should be a suitable process for the preparation of an E/O emulsion as this technique is well suited for large scale production. The preparation of W/O or E/O emul- sions by membrane emulsification is shown in Fig. 1. The dispersed phase (water or ethanol) is pressed through the pores into the con- tinuous phase (oil) flowing tangentially to the membrane surface. Droplets grow at pore openings until they detach when having reached a certain size. The droplet detachment is governed by the balance between the drag force on the droplet from the flowing continuous phase, the interfacial tension forces, the buoyancy of the droplet, and the pressure difference between the phases [4,5]. To prevent droplet coalescence immediately after formation, emulsifier molecules must stabilize the newly formed interfaces fast enough. Reported applications of membrane emulsification in the food and pharmaceutical industries include the preparation of simple emulsions, multiple emulsions, and encapsulated materi- als [6–8]. Membrane emulsification was applied mainly to the prepara- tion of O/W emulsions, although a number of studies also reported the preparation of W/O emulsions. Kandori et al. [9,10] prepared W/O emulsions by using Shirasu-porous-glass (SPG) membranes with a copolymer type emulsifier poly(oxyethylene–oxypropy- lene). The size of the water droplets in the resulting emulsions and their stability were shown to depend strongly on the interfa- cial tension between water and oil phases. Stable monodispersed 0016-2361/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2010.06.036 * Corresponding author at: CNRS, UMR 5007, Laboratoire d’Automatique et de Génie des Procédés, France. Tel.: +33 4 72 43 18 67; fax: +33 4 72 43 16 99. E-mail address: charcosset@lagep.univ-lyon1.fr (C. Charcosset). Fuel 89 (2010) 3482–3488 Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel