Étude de la cristallisation d'une cire paraffinique dans nn-tetradecane. Comparaison avec le nn-pentacosane

L'étude de la solubilité d'une cire paraffinique, dite de type “normale”; issue de déparaffinage des huiles lubrifiantes et celle d'un n-alcane pur dont le nombre de carbones est égal au nombre de carbones moyen de la cire, dans un solvant est réalisée par analyse thermique simple et différentielle. Les résultats obtenus montrent, d'une part, que les deux systèmes (Cire, C$_{14}$) et (C$_{25}$, C$_{14}$) ont des diagrammes de phases superposables dans tout le domaine de composition et d'autre part, les deux diagrammes présentent une solidification eutectique binaire. Ce qui nous a donc amener à considérer la cire comme un pseudo constituant pur ou “composé définit”. La prédiction de température de cristallisation commençante du système (C$_{25}$, C$_{14}$) est réalisée à l'aide du modèle de Flory Huggins

Mixtures of numerous different n-alkanes: 2. Studies by X-ray diffraction and differential thermal analyses with increasing temperature

International audienc

Evolution structurale en fonction de la température des mélanges binaires n-C

L’évolution en fonction de la température des mélanges binaires n-C22-n-C24 compris entre 20 et 48% molaire en n-C24 est déterminée par analyse radiocristallographique. Dans ce domaine de concentration les mélanges constituant la phase β" de structure orthorhombique évoluent en fonction de la température vers la phase orthorhombique β sans passer par le domaine β'. Le diagramme de phases du binaire docosane-tétracosane est représenté à partir de l’ensemble des résultats obtenus sur ce système

Binary systems of even-numbered n-alkanes (C

We establish a systematic for the binary phase diagrams of even-numbered n-alkanes (C2p - C2p+2. 10 ≤ p ≤ 12) whose lengths differ by two carbon atoms. The C20 - C22 system has been published by LUTH. We determined the C22 - C24 phase diagram, and we suggest a provisional diagram for the C24 - C26 system

Ternary Mixtures of N-Docosane, N-Tricosane and N-Tetracosane Mélanges ternaires de n-docosane, n-tricosane et n-tétracosane

Binary phase diagrams of the systems: n-docosane: n-tricosane (C22H46 : C23H48), n-tricosane: n-tetracosane (C23H48: C24H50) and n-docosane: n-tetracosane (C22H46: C24H50) have been established by means of structural and differential scanning calorimetry analyses. On the basis of these results and of X-ray examination of forty one ternary mixtures, it is proposed the ternary phase diagram (C22H46: C23H48: C24H50) at room temperature. This work has indicated the existence of limited terminal solid solutions near the three pure n-alkanes and three domains of orthorhombic intermediate phases (noted ß' 1, ß'' 1, ß' 2) identical to those observed in the binary systems. X-ray experiments have showed that the phases ß' 1, ß'' 2 situated on the both sides of the middle intermediate phase ß' 1, are isostructural as in the binary systems. <br> Les diagrammes de phases des systèmes binaires : n-docosane : n-tricosane (C22H46 : C23H48), n-tricosane : n-tétracosane (C23H48 : C24H50) et n-docosane : n-tétracosane (C22H46 : C24H50) ont été établis à partir d'analyses thermiques différentielles (ATD) et structurales. Sur la base de ces résultats, ainsi que de l'examen aux rayons X de 41 mélanges ternaires, le diagramme de phases du ternaire (C22H46 : C23H48 : C24H50) à température ambiante est proposé. Ce travail a indiqué l'existence de domaines limités de solutions solides au voisinage des trois n-alcanes purs, ainsi que de trois régions de phases intermédiaires orthorhombiques (notées ß' 1, ß 1, ß' 2) identiques à celles observées avec les systèmes binaires. Les analyses aux rayons X ont montré que les phases ß' 1 et ß' 2 situées de part et d'autre de la phase médiane intermédiaire ß1 sont isostructurales, tout comme dans le cas des systèmes binaires

Mixtures of numerous different n-alkanes: 1. Structural studies by X-ray diffraction at room temperature—Correlation between the crystallographic long c parameter and the average composition of multi-alkane phases

International audienc

Experimental Determination and Representation of Binary and Ternary Diagrams of N-Hexacosane, N-Octacosane and N-Heptane

Accumulation of waxy deposits is a commonly occurring problem during exploitation and transportation of paraffinic crude oils. Limitation of these undesirable solids or removal by methods such as addition of chemical inhibitor, scrapping or heat tracing of flowlines, increase production costs. A better knowledge of this phenomenon will make it possible to adjust process operating parameters and limit the operating costs. Thermodynamic models can be used in order to calculate the wax appearance temperature and the amount of solid deposit versus temperature. In these models, the crude oil is represented as a mixture of pure or pseudo-components(which content several pure components). To describe the thermodynamic properties of those mixtures, data on pure components and on their mixtures are necessary but they are very scarce for heavy components in the literature. This work is devoted to the study of a mixture of heavy components including two heavy n-alkanes (n-hexacosane, denoted C26 and n-octacosane, denoted C28) and a solvent (n-heptane denoted C7). Measurements of solubility of C26 and C28 and of equimolar mixture of C26 and C28 in C7, and an isothermal ternary diagram of the mixture of the three components at 303K are presented. Their calculations using simple expressions of Gibbs molar energy (NRTL and Redlich-Kister) are in good agreement with experimental data. The work allows to consider calculating complex systems with the only use of binary interaction coefficients

Experimental Determination and Representation of Binary and Ternary Diagrams of N-Hexacosane, N-Octacosane and N-Heptane

International audienceAccumulation of waxy deposits is a commonly occurring problem during exploitation and transportation of paraffinic crude oils. Limitation of these undesirable solids or removal by methods such as addition of chemical inhibitor, scrapping or heat tracing of flowlines, increase production costs. A better knowledge of this phenomenon will make it possible to adjust process operating parameters and limit the operating costs. Thermodynamic models can be used in order to calculate the wax appearance temperature and the amount of solid deposit versus temperature. In these models, the crude oil is represented as a mixture of pure or pseudo-components(which content several pure components). To describe the thermodynamic properties of those mixtures, data on pure components and on their mixtures are necessary but they are very scarce for heavy components in the literature. This work is devoted to the study of a mixture of heavy components including two heavy n-alkanes (n-hexacosane, denoted C26 and n-octacosane, denoted C28) and a solvent (n-heptane denoted C7). Measurements of solubility of C26 and C28 and of equimolar mixture of C26 and C28 in C7, and an isothermal ternary diagram of the mixture of the three components at 303K are presented. Their calculations using simple expressions of Gibbs molar energy (NRTL and Redlich-Kister) are in good agreement with experimental data. The work allows to consider calculating complex systems with the only use of binary interaction coefficients