Solubility dynamic method

With the dynamic methods, the SCCO2 flows continuously on or through the compound. The operating conditions are chosen to ensure that the outlet flow is in solvatization equilibrium. Solubility of SCCO2 in the component is usually neglected. 

The thermodynamic excess functions for the 2-propanol-water mixture and the effects of lithium chloride, lithium bromide, and calcium chloride on the phase equilibrium for this binary system have been studied in previous papers (2, 3). In this paper, the effects of lithium perchlorate on the vapor-liquid equilibrium at 75°, 50°, and 25°C for the 2-propanol-water system have been obtained by using a dynamic method with a modified Othmer still. This system was selected because lithium perchlorate may be more soluble in alcohol than in water (4). 

The dynamic method of studying vapor-liquid equilibria requires the use of an inert gas that is passed over the liquid phase under conditions that equilibrium is attained. Under such conditions the total pressure is controlled and can be made the same in each experiment. The system is actually a three-component system in which the solubility of the inert gas in the liquid phase is extremely small and its effect is neglected. The chemical potential of the first component in the gas phase in equilibrium with the solution is... 

W. Swope, H. Andersen, A molecular dynamics method for calculating the solubility of gases in liquids and the hydrophobic hydration of inert-gas atoms in aqueous solution. J. Phys. Chem. 88, 6548 (1984)... 

In this paper solubility measurements of synthetic and natural dyestuffs are presented using VIS-spectroscopy. The investigations concentrate on two different methods. I. P-carotene was measured as a function of temperature and pressure in near- and supercritical C02 (289 to 309 K, 10 to 160 MPa) and CC1F3 (297 to 326 K, 12 to 180 MPa), respectively, using a static method. II. Additionally, the solubilities of l,4-bis-(n-alkylamino)-9,10-anthraquinones (with n-alkyl = butyl, octyl) were determined with a dynamic method in temperature and pressure ranges from 310 to 340 K and 8 to 20 MPa, respectively this method permits a continuous purification from better soluble impurities as well as the measurement of solubilities at the same time. For both anthraquinone dyestuffs intersection points of the solubility isotherms were found in the plot of concentration versus pressure. This behavior can be explained by a density effect. 

Recently additional measurements on some of these anthraquinone dyes were carried out with a dynamic method using a supercritical fluid chromatography (SFC) technique. This method permits the measurement of solubilities as well as the continuous purification from better soluble impurities which might cause serious errors in the solubility data (see section 3.). 

The dynamic method permits the purification from better soluble impurities as well as continuous solubility measurements at the same time. An adsorption effect of the stationary phase which is used to precipitate the dyestuff on its surface is not found within the experimental accuracy. The measurements of l,4-bis-(n-alkylamino)-9,10-anthraquinone (with n-alkyl = butyl, octyl) show two intersection points in the plot of pressure versus concentration. 

The porous structure of active carbons can be characterized by various techniques adsorption of gases (Ni, Ar, Kr, CO ) [5.39] or vapors (benzene, water) [5,39] by static (volumetric or gravimetric) or dynamic methods [39] adsorption from liquid solutions of solutes with a limited solubility and of solutes that are completely miscible with the solvent in all proportions [39] gas chromatography [40] immersion calorimetry [3,41J flow microcalorimetry [42] temperature-programmed desorption [43] mercury porosimetry [36,41] transmission electron microscopy (TEM) [44] and scanning electron microscopy (SEM) [44] small-angle x-ray scattering (SAXS) [44] x-ray diffraction (XRD) [44]. 

In this paper we propose a dynamic method for tackling the problem of interactions in soluble monolayers. The surface dilational modulus, e, is a dynamic surface quantity very sensitive to interactions. It is defined as the decrease in local surface pressure per unit relative increase in surface area A in an oscillatory experiment ... 

DYNAMIC METHODS FOR MEASURING SOLUBILITIES IN SUPERCRITICAL FLUIDS... 

Dynamic Methods for Measuring Solubilities in Supercritical Fluids 87... 

The p and T conditions chosen for solubility measurements with the dynamic method were limited by the temperature stability of the fiber optic system. The maximum temperature was 70 °C at a maximum pressure of 250 atm. In Figure II eight p/T- conditions for solubility determinations are presented. 

The liquid-vapour equilibrium in the HF-H2SO4 system has been investigated by a dynamic method over the temperature range 30—150 The solubility of... 

Three phase systems have been the main focus of activities in chemical reaction engineering, and the many novel aspects of them are too numerous to cover here, hence only a few examples will be referenced. In the case of gas-1iquid-sparingly soluble solid, it has been demonstrated that particles substantially smaller than the diffusion film thickness of film model can enhance the specific rates of mass transfer if the reaction is sufficiently fast (45). Work in this area has been persistently pursued by Sada and coworkers (46,47). Recently Alper et al. (24) has pointed out and demonstrated that in catalytic slurry reactors similar enhancement can be observed if the catalyst particles are sufficiently small. There is however some dispute on the order of magnitude of the enhancement (48,49). Another aspect is complex reactions and in the case of slurry reactors the product distribution may well depend on the degree of diffusional resistance (50). Dynamic methods have been ingeniously employed to obtain physicochemical parameters in slurry reactors (51). 

Figure 18. Solubility of AQ08 in carbon dioxide as a function of density, according to Tuma [47,76] (the isotherm measured up to concentrations of ca. 70 10 mol dm only (310.1 K) was determined with a Cary 17H spectrophotometer, that at 303.2 K in another optical high-pressure cell [74], all others with a Perkin-Elmer Lambda 18, respectively the data for 310.1 K (indicated by o) were obtained according to the dynamic method [40]).

W. C. Swope and H. C. Andersen,/. Phys. Chem., 88,6548 (1984). A Molecular Dynamics Method for Calculating the Solubility of Gases in Liquiik and the Hydrophobic Hydration of Inert Gas Atoms in Aqueous Solution. 

Isobaric-isothermal methods are often also called dynamic methods. One or more fluid streams are pumped continuoirsly into a thermostated equilibriirm cell. The pressure is kept constant during the experiment by controlling an effluent stream, irsually of the vapor phase. One can distinguish between continuorrs-flow methods and semi-flow methods. In continuous-flow methods, both phases flow throrrgh the eqrrihbrirrm cell. They can be used only for systems where the time needed to attain phase equilibrium is sufficiently short. Therefore, such equipment is usually not applied to polymer solutions. In semi-flow methods, only one phase is flowing while the other stays in the equilibrium phase. They are sometimes called gas-saturation methods or pure-gas circulation methods and can be used to measure gas solubilities in liquids and melts or solubilities of liquid or solid substances in supercritical fluids. 

Surface tension methods measure either static or dynamic surface tension. Static methods measure surface tension at equilibrium, if sufficient time is allowed for the measurement, and characterize the system. Dynamic surface tension methods provide information on adsorption kinetics of surfactants at the air-liquid interface or at a liquid-liquid interface. Dynamic surface tension can be measured in a timescale ranging from a few milliseconds to several minutes [315]. However, a demarkation line between static and dynamic methods is not very sharp because surfactant adsorption kinetics can also affect the results obtained by static methods. It has been argued [316] that in many industrial processes, sufficient time is not available for the surfactant molecules to attain equilibrium. In such situations, dynamic surface tension, dependent on the rate of interface formation, is more meaningful than the equilibrium surface tension. For example, peaked alcohol ethoxylates, because they are more water soluble, do not lower surface tension under static conditions as much as the conventional alcohol ethoxylates. Under dynamic conditions, however, peaked ethoxylates are equally or more effective than conventional ethoxylates in lowering surface tension [317]. 

Prediction of Liquid Solubility with Molecular Dynamics (MD) and Monte Carlo (MC) Methods... 

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