High-Pressure Soybean Oil Biodiesel Density: Experimental Measurements, Correlation by Tait Equation, and Perturbed Chain SAFT (PC-SAFT) Modeling Rachid Aitbelale,* ,†,‡ Younes Chhiti, ‡ Fatima Ezzahrae M’hamdi Alaoui, ‡ Abdelaziz Sahib Eddine, † Natalia Muñ oz Rujas, § and Fernando Aguilar § † Laboratory of Catalysis and Corrosion of Materials (LCCM), Chemistry Department and ‡ Science Engineer Laboratory for Energy (LabSIPE), National School of Applied Sciences, Chouaïb Doukkali University, 24000 El Jadida, Morocco § Department of Electromechanical Engineering, Superior Polytechnic School, Burgos University, E-09006 Burgos, Spain ABSTRACT: Biodiesel can easily become the crucial solution for environmental problems. The high production rate of soybean oil has been the subject of several research works to transform it into biodiesel. Knowledge of the thermodynamic properties of soybean oil biodiesel (SOB) such as densities and coefficients of expansivity and compressibility play an important role in the understanding of the intermolecular interactions between the different molecules, which in turn have an impact on fuel quality. The difficulty in measuring the thermodynamic properties of biodiesel is because they are complex structures and high-molecular-weight components. The experimental density (136 points) for SOB, as a pseudopure component, at several temperatures (298.15-393.15 K) and pressures up to 140 MPa is reported. An Anton Paar vibrating tube densimeter, calibrated with an uncertainty of ±0.7 kg m -3 , was used to perform these measurements. To determine the chemical fatty acid methyl ester composition, SOB was analyzed by CHNS analysis, 1 H NMR, 13 C NMR, and gas chromatography-mass spectrometry and, then, the density experimental data were correlated by the Tait and perturbed chain-statistical associating fluid theory (PC-SAFT) equations of state (EoS). The experimental data were compared with correlated data, resulting in absolute average deviation (AAD = 0.01%), maximum deviation (MD = 0.03%), average deviation (Bias = -9.88 × 10 -7 %), and standard deviation (σ = 1.18 × 10 -4 g cm -3 ) for the empirical Tait equation. Concerning PC-SAFT EoS, the density was reasonably correlated with AAD = 0.063%. On the other hand, isothermal compressibility, κ T , and isobaric thermal expansivity, α p , were derived from the Tait equation. The same behavior is observed for κ T and α p , consistent with the expected one. The isobaric thermal expansivity, α p , presents a crossing point at nearly 35 MPa, in agreement with what had been observed by other authors. 1. INTRODUCTION As an alternative to petrol and diesel, biodiesel can easily become the crucial solution for environmental problems. 1 Biodiesel is the common name for a variety of ester-based oxygenated fuels from renewable biological sources. It can be obtained from vegetable oils and animal fats. To date, many vegetable oils have been used to produce biodiesel such as soybean, rapeseed, palm oils, etc. Soybean oil alone accounts for 61% of agricultural area in oilseeds, while those devoted to rapeseed, sunflower, and palm are 18, 14, and 7%, respectively. 2 In principle, any source of fat can be used to prepare biodiesel. However, some sources are favored more than others according to the country. 3 The literature reveals that several works are carried out on the synthesis and manufacturing of biodiesel from vegetable oils, 4-10 but there is dearth of experimental data and/or prediction models for thermody- namic properties of vegetable oils. 11 The ability to predict biodiesel density and to determine several thermodynamic properties is important when designing equipment for synthesis processes and solving the engineering problems. This is of particular importance in the oil and gas sector where many flow measurement systems make use of volumetric flow measurement devices. The density at high pressures is essential to optimize and evaluate various chemical processes in the purification and production of biodiesel. The difficulty in predicting these properties is because biodiesels are complex structures and high-molecular-weight components. However, the development of robust equations to describe thermodynamic properties taking into account the effect of molecular interaction becomes paramount. The statistical associating fluid theory (SAFT) equations of state (EoS) has been successfully applied to a wide range of several Received: May 3, 2019 Accepted: August 22, 2019 Article pubs.acs.org/jced Cite This: J. Chem. Eng. Data XXXX, XXX, XXX-XXX © XXXX American Chemical Society A DOI: 10.1021/acs.jced.9b00391 J. Chem. Eng. Data XXXX, XXX, XXX-XXX Downloaded via COLUMBIA UNIV on September 3, 2019 at 16:21:11 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.