Journal of Membrane Science 333 (2009) 141–146 Contents lists available at ScienceDirect Journal of Membrane Science journal homepage: www.elsevier.com/locate/memsci Separation of n-butane from soybean oil mixtures using membrane processes Marcus V. Tres, Stefany Mohr, Marcos L. Corazza, Marco Di Luccio ∗ , J. Vladimir Oliveira Department of Food Engineering, URI - Campus de Erechim, Av. Sete de Setembro, 1621, Erechim 99700-000, RS, Brazil article info Article history: Received 24 December 2008 Received in revised form 5 February 2009 Accepted 8 February 2009 Available online 20 February 2009 Keywords: Soybean oil n-Butane Polymeric membranes Ultrafiltration Nanofiltration abstract Separation of refined soybean oil/n-butane mixtures was studied in this work using different commercial ultra- and nanofiltration membranes, with cut-offs ranging from 1 to 5 kDa. Refined soybean oil/n-butane mixtures at 1:3 (w/w) and 1:1 (w/w) mass ratios were continuously fed to a tangential flow module. The effects of the feed pressure (10–25 bar) and the transmembrane pressure difference (1–10 bar) on oil flux and retention were investigated. Oil retention results ranged from 52.8 to 99.1% and n-butane flux up to 2730 g/m 2 h were obtained. Membrane fouling was observed in all experimental conditions studied. The membrane separation process has proven to be a promising alternative to the recovery of the pressurized solvent. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Edible oils and fats are renewable resources worldwide available with many different applications. However, despite some excep- tions, the crude oil cannot be commercially used without further processing. The crude edible oils need to be refined to meet suit- able properties for commercial applications. This process involves removing unwanted components and concentration of desired sub- stances. Edible oils are usually extracted using n-hexane, therefore demanding a step of solvent removal from the oil [1]. Expensive and time-consuming processes, such as distillation, must be used to remove n-hexane from the oil and the residue. Nevertheless, compressed gases like propane and n-butane can also be used as alternative extraction solvents. In fact, the extraction with compressed fluids may be attractive due to the possibility of operation at mild temperatures, change in the process selectivity by tuning operating pressure hence changing solvent power and also easy recovery from the mixture with essentially no solvent residue [2–9]. Another advantage is the operation at ambient or below- ambient temperatures, which minimizes thermal degradation of proteins, antioxidants and other nutritionally valuable compounds [10]. The major drawbacks of the use of n-propane and n-butane are the risk of flammability, which requires special design, and the costs with the recompression steps involved in the process. Many industries in the world are concerned to reduce costs, investing in alternative economically sustainable processes. Mem- brane processes offer several advantages when compared to the ∗ Corresponding author. Tel.: +55 54 35209000; fax: +55 54 35209090. E-mail address: diluccio@uricer.edu.br (M. Di Luccio). conventional separation techniques and can be used in almost all oil processing stages. Many studies have directed efforts to the development of new methods to separate the oil constituents, deacidification, decolorization and solvent recovery. Degumming and solvent recovery are the most studied process, since they are the most energy-consuming steps in the oil processing industry [1–5,11–24]. One should call attention at this point that in the extraction process using compressed fluids, membrane separation could be advantageously used for minimizing solvent recompres- sion costs [25,26]. An ideal membrane for use in the edible oil processing indus- try should combine the required retention characteristics with a high permeate flux and long term stability. The main problem when processing high viscosity systems is the low permeate flux, due to the high viscosity of fats and oils. An increase in the transmem- brane pressure (TMP) can increase the flux, but there are limits on the operating pressures that membranes can tolerate while keep- ing their rejection characteristics. The viscosity of the feed can be reduced by an increase in temperature, thus improving flux. However, some limitations may apply, since membrane stability generally decreases with temperature [1]. Pressure-driven membrane filtration is primarily a size- exclusion based process. It separates different components according to the molecular or particle sizes. It is also dependent on their interactions with the membrane surfaces and other com- ponents of the mixture. It is well known that performance of membrane separation is affected by membrane composition, tem- perature, pressure and flow rate [21]. The major potential for energy savings due to application of membrane processes in the oil production lies in the replacement or supplementing the conventional degumming, refining and 0376-7388/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.memsci.2009.02.008