Optimization of factors affecting esterification of mixed oil with high percentage of free fatty acid H.A. Farag a , Azza El-Maghraby b, ⁎, Nahla A. Taha b a Chemical Engineering Department, Faculty of Engineering, Alexandria University, Egypt b Department of Fabrication Technology, Institute of Advanced Technology and New Materials, Mubarak City for Scientific Research and Technology Applications, Alexandria, Egypt abstract article info Article history: Received 30 June 2010 Received in revised form 28 October 2010 Accepted 2 November 2010 Available online 27 November 2010 Keywords: Esterification Mixed oil Free fatty acids Biodiesel Increased environmental awareness and depletion of resources are driving industry to develop alternative fuels from renewable sources that are environmentally more acceptable. Biodiesel is a non petroleum based fuel that consists of alkyl esters from transestrification of the refined/edible types of vegetable oils alcohol and alkaline catalysts can be used. These catalysts require anhydrous conditions and feed stocks with low levels of free fatty acids (FFAs). Inexpensive feed stocks are used in biodiesel production to reduce its cost and to get rid of waste oils in environmentally friendly way. These oils may contain high levels of FFAs so it cannot be directly used with the base catalysts currently employed. Acid esterification reduces the FFAs content to the desirable level. The major factors that affect the conversion efficiency of the process are molar ratio of alcohol/ oil, amount of catalyst, reaction temperature, catalyst type and stirring speed according to reaction duration. For this study, we used a model acid produced by mixing pure oleic acid with mixed oil (50% sunflower + 50% soybean oil). Methanol was used in the experiments due to its low cost. The best conversion efficiency obtained was 96.6% for a molar ratio of 6:1 at a temperature of 60 °C, 2.5% H 2 SO 4 and stirring speed of 300 rpm. Finally, different types of waste cooking oil from home and restaurants were used to study the conversion efficiency compared with optimum conditions calculated for model acid oil to be used in biodiesel production with low cost. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Since fossil fuels increase greenhouse gas emissions and cause global warming, the use of alternative resources like biofuels are more pronounced everyday [1]. Liquid fuels from agricultural origin are being increasingly considered as alternatives to gasoline and gas oil as sources of energy. Specifically biodiesel has a substantial potential to reduce oil imports and ensure continuity in the energy supply [2]. A great number of advantages are obtained by using biodiesel instead of normal diesel, namely, biodegradable, non toxic, lower emission of CO due to a better combustion, a better lubricating effect on engines and reduction of the frequency of engine part replacement, non sulfur emissions, non particulate matter pollutants and higher flash point than normal diesel that finally does not contribute in global warming. [3–6]. Biodiesel can be used in neat form or mixed with petroleum based diesel. There are four primary processes for manufacture of biodiesel: first is direct use with blending, micro emulsions, thermal cracking (pyrolysis) and finally transestrification [7]. The most commonly used method is transestrification of triglycerides or the esterification of free fatty acids with low molecular weight alcohol. Refined vegetable oils, animal oils, and waste cooking oils can be used in biodiesel production. Waste cooking oils are an economical choice for biodiesel production, because of their availability and low costs [8]. The annual consumption of vegetable oil in Egypt exceeds million MT/year (1,248,000 MT in 2005 according to the official statistics of the Ministry of Internal Trade in Egypt and the USDA). Egyptians eat fava beans as a source of protein in their diet and fried falafel (green fava bean paste) is the most popular food in Egypt served at houses and fast-food and popular restaurants. As in case of French fries, fried falafel requires frying in vegetable oil. In addition, the Egyptian dietary pattern and habits make use of potatoes and fish. Consequently, millions of liters of oil used for frying foods are discarded each year into sewage systems. Thus, it adds to the cost of treating effluent or pollutes waterways. From a waste management standpoint, producing biodiesel from used cooking oils is environmentally beneficial, since it provides a cleaner way for disposing these products in comparison with what is typical [9]. In spite of its low cost, waste cooking oil pretreatment is still a problem [10] due to its high free fatty acid level, i.e., free fatty acids amount larger than 1 mg/g KOH results in high amounts of undesirable soap produced simultaneously with transestrification reaction. Therefore, to avoid this reaction, alternative technologies should be employed, and when acid oils are used to produce biodiesel, Fuel Processing Technology 92 (2011) 507–510 ⁎ Corresponding author. Mubarak City for Scientific Research and Technology Applications, New Borg Elarab City, Alexandria, Egypt. Tel.: +20 0103087123; fax: +20 03 4593414. E-mail address: maghrabyazza@yahoo.com (A. El-Maghraby). 0378-3820/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.fuproc.2010.11.004 Contents lists available at ScienceDirect Fuel Processing Technology journal homepage: www.elsevier.com/locate/fuproc