Temperatures and enthalpies of (solid + solid) and (solid + liquid) transitions of n-alkanes

Fundamental Study of Wax Deposition Under Real Flow Conditions

“…The results are summarized in Table 6-2. Within the reported uncertainties, all phase transition temperatures and enthalpies are in agreement with the values reported in the literature (Dirand et al, 2002), except for the enthalpy of fusion of the n-docosane (n-C22). As can be seen in Figure 6-2, the thermogram for n-docosane did not allow to fully resolve the transition peaks, compromising their direct integration.…”

“…It shows a two-peak profile for all samples analyzed. The peak that appears at a lower temperature level is attributed to a solid-solid transition, from an ordered to a disordered (o-d) solid phase (Dirand et al, 2002). The second peak, the one at a higher temperature level, is attributed to melting (solid-liquid transition).…”

A new calorimetric technique for phase change materials and its application to alkane-based PCMs

“…This is not a consequence of a failure of the measurement method, like in DSC, but an indication that a substantial temperature gradient is generated inside the sample. Figure 5 shows that C23 has no less than five transitions between 35 and 50 C. We refer the reader to References [34,[43][44][45] for a detailed description of the different phases of this compound. The exact nature of the phases is not relevant for the discussion here, but we introduce the names of the phases for easy referral to the different transitions.…”

Thermodynamic and structural studies of the solid deposit formation in paraffinic petroleum cuts

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A general review [1,2] is presented concerning jointly the crystallographic structures and the transition physicochemical data (T fus , ∆ fus H, ∆ fus S, ∆ eb H, ∆ sub H, Cp) in the pure normal alkanes, as well as the structural and thermodynamic behavior of their synthetic binary, ternary and multinary model mixtures and of real petroleum waxes, particularly the solubility and mixture properties [3][4][5][6]. A major part of the structural and thermodynamic data of the literature and our experimental results are listed from methane up to the alkane with carbon atom number equal to 390 [1, 2] as well as their variations versus the atom carbon number.

The experimental results [3] and those of literature concerning the pure n-alkane dissolution enthalpies allow to determine the enthalpy of the formation of one or several crystallized solid solutions of the mixtures [4] and to highlight the influence of the characteristic parameters of the paraffinic distribution (theoretical average chain length, n-alkanes number, monophasic or polyphasic state) on the excess properties in the solid state.

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“…A general review [1,2] is presented concerning jointly the crystallographic structures and the transition physicochemical data (T fus , ∆ fus H, ∆ fus S, ∆ eb H, ∆ sub H, Cp) in the pure normal alkanes, as well as the structural and thermodynamic behavior of their synthetic binary, ternary and multinary model mixtures and of real petroleum waxes, particularly the solubility and mixture properties [3][4][5][6]. A major part of the structural and thermodynamic data of the literature and our experimental results are listed from methane up to the alkane with carbon atom number equal to 390 [1, 2] as well as their variations versus the atom carbon number.…”