Article pubs.acs.org/jced
Water Content in Biodiesel, Diesel, and Biodiesel−Diesel Blends Patricia Bogalhos Lucente Fregolente,* Leonardo Vasconcelos Fregolente,† and Maria Regina Wolf Maciel‡ Separation Process Development Laboratory, Chemical Engineering School, State University of Campinas, 13083-852, Campinas, São Paulo, Brazil ABSTRACT: Biodiesel has a higher affinity toward moisture content than petroleum diesel, and the water retaining capacity of biodiesel is higher than diesel. The water content in fuels can be classified in free, emulsionated, and soluble water. High water content in biodiesel and diesel can cause problems such as water accumulation and microbial growth in fuel tanks and transportation equipment. Currently, there is a lack of information on water absorbance in biodiesel and biodiesel/diesel blends. Experiments were conducted to determine the water absorbance of biodiesel and biodiesel− diesel fuel blends evaluating the temperature and blend ratio parameters. Soluble water in biodiesel ranged from (1500 to 1980) mg·kg−1 in the temperature range of (283.15 to 323.15) K, which was 10 to 15 times higher than diesel. Results also showed that, at constant relative humidities, biodiesel absorbed 6.5 times more moisture than diesel. The presence of free and/or emulsionated water in biodiesel and blends was determined through turbidity experiments.
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system.2,3,5,6 Similarly, the condensation and precipitation of water in fuels may occur during storage and transportation. Biodiesel contains no petroleum products, but it is compatible with conventional diesel and can be blended in any proportion with fossil diesel to create a stable biodiesel blend. Currently, there is a global trend to add more biodiesel in diesel over time, leading to mixtures with higher concentrations of biodiesel, for example, XB > 0.057 (XB is the mass fraction of biodiesel in the biodiesel−diesel blend). However, distributors and consumers are concerned about biodiesel−diesel blends, due to problems that may occur in storage, transportation, and the vehicle fuel injection system. Schleicher et al. (2009) reported that fungal growth was advanced by higher biodiesel content. Moreover, the formation of sediment was observed, especially in B20 (mass fraction of biodiesel in B20 blend is XB = 0.2083, see Table 1) and B5 samples.8−12 Furthermore, the slime formation due to the microbial growth caused by the presence of water in fuels, free/ emulsionated water can cause emulsions or a hazy appearance in diesel and biodiesel, making fuel out of specification for distribution and consumption. Therefore, a better understanding of water content behavior in biodiesel and blends with diesel could improve guidelines for handling and transportation of biodiesel and biodiesel−diesel blends. This research aims to determine the water absorbance of samples of biodiesel and biodiesel−diesel fuel blends by
INTRODUCTION Water content in fuel is an important aspect of fuel quality. Fuels can incorporate water during production, transportation, and storage. The water content in fuels can be classified in free water, emulsionated water, and soluble water. The solubility of water is dependent on temperature and on the composition of fuel. Therefore, the hygroscopic nature of the biodiesel can lead to an increase in soluble water content during the storage. Biodiesel has the feature to absorb more moisture than petroleum diesel since fatty acid methyl esters (FAMEs) are hygroscopic compounds, making the biodiesel much more hydrophilic than the regular diesel.1 The biodiesel industry has a limited amount of published information about fuel quality and on the effects that the presence of water causes on biodiesel and blends with diesel during storage and transportation.2,3 The maximum amount of allowed water content in biodiesel as specified in ASTM standard D6751 is 500 mg·kg−1.4 However, even that the biodiesel presents the water content specification after its production, water absorption occurs throughout the storage time, and this fact is intensified depending on the temperature and relative humidity of the environment. This can lead to an increased water absorption of the stored biodiesel, which then precipitates out (as free water) when the temperature drops. The process may repeat, and water accumulation could occur at the bottom of storage vessels.2 Free water promotes biological growth in storage tanks, which could lead to the corrosion of metals (especially iron and steel), and the formation of sludge and slime, thereby causing blockage of fuel filters and fuel lines, which could in turn damage the vehicle fuel injection © 2012 American Chemical Society
Received: March 2, 2012 Accepted: May 10, 2012 Published: May 17, 2012 1817
dx.doi.org/10.1021/je300279c | J. Chem. Eng. Data 2012, 57, 1817−1821
Journal of Chemical & Engineering Data
Article
Table 1. Values of Mass Fractions for Mixtures of Biodiesel and Diesel Oil
a
blend
XBa
B5 B10 B20 B40 B60 B80 B100
0.052 0.104 0.208 0.412 0.612 0.808 1.00
Table 4. Chemical Compounds Used in Methodology chemical NaNO2 NH4Cl hydranal titrant 2 hydranal oil solvent CS2
evaluating the temperature and blend ratio parameters. Experiments of moisture absorbing and turbidity of fuels were also conducted.
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MATERIALS AND METHODS Materials. All of the experiments were performed employing fuel samples from typical commercial Brazilian biodiesel and S50 diesel fuel (
