Binary mixtures of fatty acid ethyl esters: Solid-liquid equilibrium

Evolution of the Study of Phase Diagram of Binary and Ternary Mixtures Involving Fatty Acid Esters

“…Thus, other complementary techniques started being utilized, such as optical microcopy [ 41 , 56 ], X-ray diffraction (XRD) [ 36 ] and Fourier-Transform Infrared spectroscopy (FTIR) [ 48 ], allowing more precise and realistic phase diagrams to be developed. The improvement of the measuring devices also allows the management and reporting of additional data, which enables, for example, the representation of Tammann plots [ 26 , 32 , 34 , 35 , 42 , 43 , 47 , 49 , 50 , 52 , 54 , 55 , 56 ].…”

“…Having a better understanding of the behavior of biodiesel is the main goal of most of the literature reported, as a proper knowledge of the basic compounds’ cloud point leads to a well-known characterization of the global system [ 32 , 34 , 36 , 41 , 49 ]. Nowadays, however, in correlation to the terms “phase diagram”, “eutectic” and “fatty acid esters”, the topic of thermal energy storage is increasingly relevant to researchers in the scientific community as these compounds are becoming more and more popular as potential PCM.…”

“…That is the reason that, when extracting results from the DSC thermograms, the onset temperature is considered the most suitable one to be taken as the start of the phase change [ 43 , 44 ]. However, as DSC curves are studied more in depth, the phenomenon of overlapping peaks requires a new criterion for the data analysis, and the peak temperature is considered appropriate to indicate transitions such as eutectics and peritectics [ 35 , 45 , 46 , 47 , 49 , 50 ]. This temperature shifts when the heating rate is changed, but the onset temperature loses significance when calculated in overlapping peaks.…”

“…Predictive models are studied and evaluated for the measured mixtures by almost all the aforementioned authors, with the exception of older articles [ 27 , 28 , 29 , 38 , 39 , 40 ] and in the work of a few more recent authors evaluating the use of FAE as PCM [ 29 , 48 , 50 ]. Scientists researching on biodiesel are the ones who extensively report the comparison of experimental results with theoretical models, using mainly UNIQUAC [ 31 , 32 , 34 , 37 , 42 , 43 , 44 , 49 , 55 ], UNIFAC [ 30 , 31 , 52 , 53 , 55 , 58 , 59 ], Flory–Huggins (especially Robustillo’s team) [ 35 , 45 , 46 , 47 , 52 , 53 , 55 , 58 , 59 ] and ideal models, based on Schraeder’s equation [ 36 , 43 , 44 , 49 , 52 , 53 , 54 , 55 , 58 , 59 ]. The use of these models allows the description of the mixtures’ phase change behavior using only data from the pure materials, based on thermodynamic equations [ 35 , 45 , 46 , …”

“…All the previous research performed by the aforementioned authors is collated in [ 49 ] and completed with the depiction of nine new solid–liquid phase diagrams involving ethyl caprylate, ethyl caprate, ethyl oleate and ethyl laurate. The experimental results from both this study and the previous ones, which are compared with the liquidus line of the ideal solution predicted by the previously proposed UNIQUAC method, show a good adjustment.…”