P. Claudy

Etude du comportement thermique des n-alcanes dans des milieux hydrocarbones complexes par analyse calorimetrique differentielle. II. Determination du taux de n-alcanes contenu dans un gazole. Determination du point de trouble

Abstract The study of the thermal behavior of n -alkanes in a hydrocarbon matrix has been carried out by means of a Mettler TA 2000 B heat flow differential scanning calorimeter. A quantitative method to determine the composition in n -alkanes contained in a gas oil is described. It is assumed that the determination of the cloud point by means of DSC measurements can be obtained with a good precision.

Study of the thermal behaviour of 1,3-propanediol and its aqueous solutions

Abstract Differential scanning calorimetry was used to investigate the thermal behaviour of 1,3-propanediol and its aqueous solutions. The melting temperature of pure 1,3-propanediol and its melting heat were determined as 249xa0K and 11400xa0Jxa0mol −1 , respectively. The 1,3-propanediol–water phase diagram presented three types of behaviour on heating (following annealing), depending on composition: high alcohol–content mixtures that exhibited a eutectic and dissolution (equilibrium phases), intermediate mixtures that vitrified uniquely and high water-content solutions that showed a residual glass transition and dissolution but no eutectic. The fact that crystallization of the eutectic was not observed for high water-content solutions was discussed in terms of relatively strong interactions between water and alcohol in the liquid state, thus impeding crystallization of the alcohol. Computation of the congealing curve of water and the solubility curve of 1,3-propanediol, using the model of associated solutions, confirmed this hypothesis. Finally, a comparison between 1,3-propanediol and its isomer, 1,2-propanediol; was made; it was also discussed as to why the former crystallizes but not the latter.

Physico-chemical characterization of base stocks and thermal analysis by differential scanning calorimetry and thermomicroscopy at low temperature

Abstract A conventional base stock, solvent refined (SR) and a hydroisomerized base stock (HI) in which differences in behavior of Pour Point Depressant Additive are observed, have been dewaxed and these oils and their fractions have been characterized by analytical methods and thermal analysis. Differential scanning calorimetry (DSC) is a rapid and valuable technique for characterization of the thermal behavior of lubricating oils, allowing the determination of crystallization temperature and amount of precipitated fractions versus temperature. Differences between these base stocks, more particularly in the amount of crystals which precipitate versus temperature can explain selective effectiveness of pour point Depressant (PPD) additives.

Denaturation versus pH of lyzozyme and biosynthetic human growth hormone by differential scanning calorimetry and circular dichroism: a comparative study

Abstract The thermal behaviour of lyzozyme and human growth hormone (hGH) in aqueous solutions versus pH was studied by DSC experiments. The temperature and enthalpy of denaturation were determined, showing a maximal stability of lyzozyme at pH 4.5, and a large range of pH (5.0–9.0) corresponding to the maximal stability of hGH. These results are in good agreement with those obtained by circular dichroism measurements. The hGH environment was modified by addition of linear or aromatic small molecules and their influence on the parameters of the denaturation was studied.

Etude du comportement thermique des n-alcanes dans des milieux hydrocarbones complexes par analyse calorimetrique differentielle. I. Etude du comportement thermique des n-alcanes en programmation lineaire de temperature

Abstract Middle distillates contain various amounts of n-alkanes which are responsible for low temperature properties. The thermal behavior of 14 alkanes ranging from n-C12H26 to C25H52 has been studied by means of a Mettler TA 2000 B heat flow DSC. Different hydrocarbon matrices such as gas oil (diesel) where n-alkanes have previously been removed, kerosene and gas oil containing a known distribution of n-alkanes have been used. A comparative study of the values of the enthalpy of dissolution obtained for each n-alkane in a gas oil with or without a distribution of n-alkanes has been carried out.

Composition dependence of the glass transition temperature: Application of Van Laar type equations to the glycerol −1,2-propanediol, glycerol — water and SeGeSe2 systems

Abstract The composition dependence of the glass transition temperature T g was studied using differential scanning calorimetry for three different types of binary mixtures. The fit of the T g curves versus composition with equilibrium thermodynamic equations has led to good agreement between experimental and theoretical curves. This surprising result was discussed in terms of molecular organizations in the glassy state.

Etude du comportement thermique des n-alcanes dans des milieux hydrocarbones complexes par analyse calorimetrique differentielle. III. Etude en programmation discontinue de température

Abstract A study of the thermal behavior of n-alkanes in the solid state or in a hydrocarbon matrix has been carried out using a stepwise programming of temperature. In the case of pure n-alkanes the separation between the transition peak and the melting peak can be easily increased and the enthalpy of each thermal effect can be determined. The precipitated amount of n-alkanes contained in middle distillates has been obtained vs. temperature.

Réalisation d'un capteur thermique de haute sensibilité. Application à l'étude du comportement thermique des solutions de lysozyme et d'hormone humaine de croissance biosynthétique

Abstract A new “home-made” sensor has been developed, using a Mettler TA 2000 B apparatus. A sensitivity of 0.2 μW was obtained. The thermal behaviour of aqueous solutions of proteins was studied. The endothermic enthalpy of transition of lysozyme has been found to be Δ H = + 433 ± 20 kJ mol −1 . A study of reversibility versus thermal history of the samples has been carried out. Solutions of biosynthetic human hormone H.G.H. at a concentration of 5.6 mg ml −1 have been studied. The enthalpy of transition has been determined as Δ H = +181.5±13 kJ mol −1 . The total irreversibility of the phenomenon has been established. No exothermal effect was observed even if a low concentration of l mg ml −1 was used.

Comportement thermique des bitumes routiers. Determination du taux de fractions cristallisees par analyse calorimetrique differentielle

Abstract The thermal behavior of bitumens and their components has been studied out by means of a heat-flow differential scanning calorimeter (Mettler TA 2000 B). A quantitative method to determine the crystallized fractions contained is described.

Etude des transformations liquideahsolideahsolide de l'iodure d'argent divise

Abstract A thermal analysis of phase transformations in divided silver iodide has been carried out by scanning calorimetry and X-ray diffraction techniques. The divided state was obtained by penetration of silver iodide into porous materials with pore radii between 3.5 and 25 nm. According to results previously reported, the results of this study show, as a function of the pore radius, a decrease of the liquidahsolid transformation point, a decrease for falling temperatures and an increase for rising temperatures of the solidahsolid transition temperatures. These results are explained by homogeneous nucleation theory. The peculiar form of the phase transformation curves is attributed to the fact that the mobility of the Ag ions which is responsible for the ionic conduction of the a solid phase, vanished for pore radii smaller than 10 nm.