Published: April 19, 2011 r2011 American Chemical Society 2175 dx.doi.org/10.1021/je1012235 | J. Chem. Eng. Data 2011, 56, 2175–2180 ARTICLE pubs.acs.org/jced Densities and Viscosities of Minority Fatty Acid Methyl and Ethyl Esters Present in Biodiesel Maria Jorge Pratas, † Samuel Freitas, † Mariana B. Oliveira, † Sílvia C. Monteiro, ‡  Alvaro S. Lima, § and Jo ~ ao A.P. Coutinho* ,† † CICECO, Chemistry Department, University of Aveiro, Campus de Santiago, 3810À193 Aveiro, Portugal ‡ Polytechnic Institute of Leiria, Leiria, Morro do Lena À Alto Vieiro, 2411-901 Leiria, Portugal § Universidade Tiradentes, Av. Murilo Dantas 300, Farol ^ andia, Aracaju-SE, Brasil ABSTRACT: Biodiesels have several known components in their composition. The majority of components is well described in the literature, but a minority of components are poorly characterized. These are however required to develop reliable models to predict the biodiesel behavior. This work considers minor components of biodiesel: the polyunsaturated compounds (in C18), the monounsaturated (in C16, C20, and C22), and the long-chain saturated esters. In this work, densities and viscosities of pure fatty acid ester minor components of biodiesel fuel were measured (three ethyl esters and seven methyl esters), at atmospheric pressure and temperatures from (273.15 to 373.15) K. Correlations for the densities and viscosities with temperature are proposed. Three predictive models were evaluated in the prediction of densities and viscosities of the pure ethyl and methyl esters here reported. The GCVOL group contribution method is shown to be able to predict densities for these compounds within 1.5 %. The methods of Ceriani et al. (CM) and of Marrero et al. (MG) were applied to the viscosity data. The first show a better predictive capacity to provide a fair description of the viscosities of the minority esters here studied. ’ INTRODUCTION Nowadays, biodiesel fuel is seen as an alternative to the con- ventional petroleum-based fuels, reducing the dependency on fossil fuels and controlling greenhouse gas emissions. 1 Biodiesel fuel advantages and applications are well established. 2À9 This biofuel is comprised of monoalkyl esters of fatty acids derived from vegetable oils, animal fats, or mixtures of them. It is usually produced by the transesterification reaction of triglycerides with a short-chain alcohol, usually methanol or ethanol, in the pre- sence of a catalyst, leading to the formation of mixtures of fatty acid methyl esters (FAMEs) or fatty acid ethyl esters (FAEEs), respectively. 7,9 The main components of biodiesel fuel depend on the raw materials used, and consequently, a wide range of esters can be present. 10 Knowing the profile of methyl or ethyl esters in biodiesel is of great importance as it controls its main properties. 10 The fuel density influences the amount of mass injected at the injection systems, pumps, and injectors. 11,12 An amount of fuel precisely adjusted is necessary to provide proper combustion. 13 Combustion is initialized through atomization of the fuel. The use of a viscous fuel leads to a poor atomization which is responsible for premature injector cooking and poor fuel combustion. 11,14 Density and viscosity data are well established for the more important biodiesel compounds; however, some of the minor com- ponents have received little attention in the past. However, they may have a non-negligible influence on the biodiesel fuel proper- ties, and depending on the raw material used, these components can be present in a significant concentration. The main goal of this work is to present new density and viscosity data for the minority components of biodiesel fuel such as methyl palmitoleate, methyl linolenate, methyl arachidate, methyl gadoleate, methyl behenate, methyl erucate, methyl lignocerate, ethyl linoleate, ethyl linolenate, and ethyl arachidate, at atmospheric pressure and temperatures from (273.15 to 363.15) K. Some of these esters can be found in biodiesel fuel from peanut, rapeseed, or canola oils. 9 Among the studied esters, density data with temperature have been found only for methyl linolenate. Ott el al. 15 compiled the available density data. Besides the seven points reported by them, only Gouw and Vlugter 16 measured two other data points, in 1964. For the other esters, some isolated density data were obtained from the compound’s supplier. As experimental measurements are time-consuming and ex- pensive, especially for these minority biodiesel ester components, new models are necessary to predict these properties. Several models have been proposed in the literature to estimate biodiesel fuel density and viscosity. The most important among them rely on the accurate knowledge of the properties of the pure com- pounds. 17 However, the scarcity of density and viscosity data available in the literature restricts the use of these models to predict properties for biodiesel fuel. In a previous work, 17 the densities and viscosities of common pure methyl and ethyl esters were measured and used to evaluate the performance of three predictive models. For prediction of density, the group contribution method GCVOL 18 (group con- tribution method for predicting saturated liquid density) model was evaluated, while the models of Ceriani et al. 19 and Marrero et al. 20 were tested for the viscosity. The behavior of these models is here compared against the data for the compounds here studied. ’ EXPERIMENTAL SECTION Materials and Procedure. Three ethyl ester and seven methyl esters were used in this study. Table 1 reports the name, purity, Received: November 15, 2010 Accepted: April 7, 2011