A novel method to obtain solid–liquid equilibrium and eutectic points for hydrocarbon mixtures by using differential scanning calorimetry and numerical integration

Abstract

Solid-liquid equilibrium (SLE) is essential for some separation processes in chemical industries. SLE for hydrocarbon mixtures, biofuels, phase change materials (PCM) or deep eutectic solvents (DES) are current topics in literature. Most common study involves binary systems and very often eutectic points are presented.A new method has been developed to determine the solid–liquid equilibrium and the eutectic compositions of hydrocarbon binary systems. Differential Scanning Calorimetry (DSC) and numerical integration are combined and only two DSC analyses are required. A deconvolution procedure with Asymmetric Double Sigmoidal (ADS) equation is proposed to analyse the peaks individually when the thermogram peaks overlap. The ADS equation produced the most accurate fit for five different DSC peaks.The new method was successfully validated against the conventional method by comparing fourteen samples from four eutectic binary systems (naphthalene/n-tetracosane, naphthalene/n-octacosane, p-xylene/n-hexadecane and n-octane/1-methyl-naphthalene).Uncertainty analysis carried out for the new method leads to SLE data errors of 0.612 K and 0.011 for temperature and mole fraction, respectively. The new method for the calculation of compositions, masses and eutectic points was applied for several samples of each system. The SLE and eutectic data obtained were compared with the conventional method, achieving standard deviations of 2.23 K and 0.04 for temperature and mole fraction, respectively. The new method can save at least a 50% of the experimental time and its associated resources compared to the conventional method.