Evolution structurale en fonction de la température des mélanges binaires n-C₂₂-n-C₂₄ compris entre 20 et 48 % mol en n-C₂₄. Détermination du diagramme de phases du système docosane-tétracosane

Normal Alkanes, Multialkane Synthetic Model Mixtures, and Real Petroleum Waxes: Crystallographic Structures, Thermodynamic Properties, and Crystallization

“…Then Hasnaoui et al also highlighted three orthorhombic intermediate phases in the (C 22 /C 24 ) system; Achour et al ,, showed the similarity between the (C 20 /C 22 ) phase diagram of Lüth et al and those of both of the (C 22 /C 24 ) 149,150,152 and (C 24 /C 26 ) systems determined by Achour-Boudjema et al , At the same time, Gerson and Nyburg 24 determined the structure of one of these intermediate phases of the C 24 /C 26 system: orthorhombic space group Bb 2 1 m…”

“…26,55,65,133,237,256,257 Many phase diagrams have been presented with an orthorhombic continuous solid solution at room temperature even if the two pure C n 's displayed a (n c -n c′ )/n c relative gap between the chain lengths of molecules which was too high, according to Kravchenko's rule (Table 6), and/or a triclinic or monoclinic phase not compatible with Palatnik 170 (C 24 /C 28 ). 194 In 1974, Lu ¨th et al 145 Then Hasnaoui et al 65 also highlighted three orthorhombic intermediate phases in the (C 22 /C 24 ) system; Achour et al 149,150,152 showed the similarity between the (C 20 /C 22 ) phase diagram of Lu ¨th et al 65 and those of both of the (C 22 / C 24 ) 149,150,152 and (C 24 /C 26 ) systems determined by Achour-Boudjema et al 154,157 At the same time, Gerson and Nyburg 24 determined the structure of one of these intermediate phases of the C 24 /C 26 system: orthorhombic space group Bb2 1 m From the structural observations of Smith 143 and Gerson and Nyburg 26 and the phase diagrams determined by Lu ¨th et al 145 (C 20 /C 22 ), by Achour et al 149,150 (C 22 /C 24 and C 24 / C 26 ), 154,157 by Denicolo et al 168 and Nouar et al 165 (i) At room temperature, limited terminal solid solutions with the pure C n crystalline structure exist for the concentrations close to two pure C n 's, and two (∆n c ) 1) or three orthorhombic intermediate solid solutions (∆n c ) 2) appear when the concentration varies; these intermediate phases are respectively denoted β′ 1or2 and β′′ 1or2 . In all the binary systems, the β′ phases are indistinguishable and thus they are isostructural.…”

“…(1) Binary Mixtures of Consecutive C n 's ( Δ n c ≤ 2). The binary mixtures of C n 's have been the subject of numerous articles. ,,,,− ,,, Many phase diagrams have been presented with an orthorhombic continuous solid solution at room temperature even if the two pure C n 's displayed a ( n c − n c ‘ )/ n c relative gap between the chain lengths of molecules which was too high, according to Kravchenko's rule (Table ), and/or a triclinic or monoclinic phase not compatible with Palatnik and Landau's rule: for instance, (C 18 /C 20 ; C 19 /C 21 ; C 21 /C 23 ; C 22 /C 23 ; C 22 /C 24 ; C 24 /C 26 ; C 30 /C 35 ; C 35 /C 36 ), (C 21 /C 23 ), (C 19 /C 21 ), (C 24 /C 28 ) …”

Variation in enthalpy of the systemn-tetracosane-n-hexacosane as functions of temperature and composition

“…The solutions [3{, 13" and 13~ undergo the same solid-state transitions as those observed in n-tricosane [2,[6][7][8][9][10][11][12] and in the binary system n-docosane-n-tetracosane [12,15].…”

“…With increasing temperature, 7t and 5' 2 behave in the same way as n-tetracosane and n-hexacosane [2,[13][14][15]. The solutions [3{, 13" and 13~ undergo the same solid-state transitions as those observed in n-tricosane [2,[6][7][8][9][10][11][12] and in the binary system n-docosane-n-tetracosane [12,15].…”