(Solid + liquid) equilibrium of binary mixtures containing ethyl esters and p-xylene by differential scanning calorimetry Larissa Castello Branco Almeida Bessa 1 • Maria Dolores Robustillo 1 • Antonio Jose ´ de Almeida Meirelles 2 • Pedro de Alca ˆ ntara Pesso ˆ a Filho 1 Received: 26 April 2018 / Accepted: 14 February 2019 Ó Akade ´miai Kiado ´, Budapest, Hungary 2019 Abstract Current concerns regarding the environmental and economic sustainability of petroleum-based transportation fuels, including jet fuel, are driving interest into alternative fuels. To study the feasibility of using biodiesel in aviation engines, a deeper knowledge on solid–liquid equilibrium (SLE) of biodiesel/jet fuel blends is required. This work presents SLE data of binary mixtures containing p-xylene, a representative compound of aviation fuel, and fatty esters present in ethylic biodiesel. Experimental data were obtained through differential scanning calorimetry. A simple eutectic behavior was observed for all binary systems, although small regions of partial miscibility are also present. Observed eutectic tem- perature and composition (ethyl ester mole fraction) are 259.0 K and 0.45, 269.0 K and 0.32, 275.5 K and 0.22, 280.0 K and 0.15, and 247.7 K and 0.58 for systems containing ethyl laurate, ethyl myristate, ethyl palmitate, ethyl stearate and ethyl oleate, respectively. Good agreement was obtained between experimental and calculated data when using UNIFAC (Dortmund) model or Flory–Huggins equation, with root-mean-square deviations ranging from 0.47 to 1.90 K. The systems exhibit significant deviations from ideality, which cannot be neglected in model calculations. Keywords DSC Á Biodiesel Á p-Xylene Á Ethyl ester Á Solid–liquid equilibrium Introduction Although commercial aviation is currently a relatively small contributor to annual global carbon dioxide (CO 2 ) emissions (approximately 2.6%) [1], its activity is expected to grow by an annual average of more than 5% [2]. To meet this traffic growth with limited environmental impact, the airline industry is committed to reduce its carbon emissions by half by 2050, compared with the 2005 level [3]. As a result, alternative jet fuel technologies have gathered interest as a means to achieve large and near-term emis- sions reductions for this industry [1]. The partial or com- plete replacement of fossil fuels by biofuels is one of the main strategies to reach a low-carbon aviation industry [4]. Sustainable jet fuel has the potential to reduce CO 2 emis- sions by up to 80%, compared with fossil jet fuel [5]. Several fuel properties must be evaluated for biofuels to be considered compatible, including energy content, octane/cetane number, material compatibility, volatility and cold flow properties [6]. For specific fuels such as jet fuels, the use of biofuels requires compliance with a range of stringent specifications such as low freezing point, thermal stability and low viscosity at low temperatures [7]. Indeed, one of the major concerns associated with the use of biodiesel is its poor low-temperature flow properties, indicated by relatively high cloud points and pour points. The cloud point is the temperature at which a liquid fatty material becomes cloudy due to the formation of crystals [8, 9]. Decreasing the temperature, solids and crystals grow and agglomerate, clogging fuel lines and filters and pos- sibly causing major operability problems. Eventually, the Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10973-019-08085-z) con- tains supplementary material, which is available to autho- rized users. & Pedro de Alca ˆntara Pesso ˆa Filho pedro.pessoa@poli.usp.br 1 Department of Chemical Engineering, Engineering School, University of Sa ˜o Paulo (USP), Caixa Postal 61548, Sa ˜o Paulo, SP 05424-970, Brazil 2 Department of Food Engineering (DEA), School of Food Engineering (FEA), University of Campinas (UNICAMP), Rua Monteiro Lobato, 80, Campinas, SP 13083-862, Brazil 123 Journal of Thermal Analysis and Calorimetry https://doi.org/10.1007/s10973-019-08085-z