Vapor-liquid equilibria of monoacylglicerol + monoacylglicerol or alcohol or fatty acid at subatmospheric pressures

Evaluation of a Variation of the Differential Scanning Calorimetry Technique for Measuring Boiling Points of Binary Mixtures at Subatmospheric Pressures

“…On the other hand, in the case of systems 7 (C9OH + C11OH) and 8 (C10OH + C12OH), inadequate DIF values were found for almost all the molar fractions investigated, which was not the case for system 1 (C12 + C13). In terms of Δ T b pure , systems 7 and 8 were 25.5 and 25.7 K, respectively, while for systems 1, 2, 4–6, 9, 11, and 12, Δ T b pure values were between 7.5 and 27.0 K. It is of note that Damaceno and Ceriani , and Cunico et al, which used this same technique with a heating rate of 25 K·min –1 and a sample size of 4–5 mg, worked with of Δ T b pure ranging from 13.0 to 24.6 K. Matricarde Falleiro et al and Akisawa Silva et al obtained boiling points of binary mixtures of fatty compounds using a manufacture pinhole of 0.25 mm on the lid. While Akisawa Silva et al kept a heating rate of 25 K·min –1 and worked with Δ T b pure between 18.3 and 22.6 K, Matricarde Falleiro et al applied two different heating rates depending on the difference between the carbon chain length of the compounds, that is, for Δ T b pure of 42.2 K they used a heating rate of 15 K·min –1 , and for Δ T b pure between 20.0 and 22.0 K they used 25 K·min –1 as the heating rate.…”

“…The boiling point was determined from the extrapolated onset temperature calculated from the thermal curves generated by the DSC software (TA Instruments). It is important to emphasize that the same experimental procedure used in previous studies for determining boiling points of pure compounds and binary mixtures ,,,, was applied in this work. Refer to these works for detailed information.…”

“…The samples were prepared by the procedure described by Damaceno and Ceriani. , In brief, known quantities (g) of pure components were mixed in an analytical balance containing approximately 0.2 g of the binary mixture. Next, samples were mixed in a vortex shaker for few minutes to make certain that they were completely homogeneous.…”

“…Considering the experimental determination of boiling points (vapor pressure or vapor–liquid equilibrium data), a nontraditional technique that has been under study is the differential scanning calorimetry (DSC) technique and its variations. The main reasons that support its use are (a) it requires a very small amount of sample (4–5 mg), which is a relevant factor when dealing with high-priced compounds, (b) its short analysis time, and (c) in the case of mixtures (more recent use), it does not require other chemical analysis for direct or indirect quantification (calibration curves) of the compositions of phases in thermodynamic equilibrium. − Yet, it is capable of providing only PTx data, which is a hindrance in terms of thermodynamically consistent experimental data. Detailed information about the DSC technique itself applied for measuring vapor–liquid equilibria and/or vapor pressure of data could be obtained from selected works in the literature. ,,− , …”

“…As a result, an optimized region for the two variables was found, and an optimized condition for the heating rate (24.52 K·min –1 ) and for the sample size (4.6 ± 0.5) mg was applied successfully for tributyrin, monocaprylin, octanoic acid, 1-octadecanol, glycerol, and n -octadecane at 3.47 kPa, and for n -hexadecane at pressures up to 18.66 kPa. Other combinations of these two variables within the optimized region (25 K·min –1 and 4–5 mg) were used successfully for measuring boiling points of pure compounds and binary mixtures. , In the procedure suggested by Troni et al, a mean value of the extrapolated onset temperature is calculated by choosing five different points along the baseline to draw its tangent and intercept it to the thermal event peak. More recently, Khoshooei et al proposed an analysis method to eliminate the effect of preboiling on obtaining an accurate boiling point of binary mixtures of methanol and isopropyl alcohol plus water, and cyclohexane plus toluene.…”