1,721,088 research outputs found
Thermodynamic of Perfluoeoethers: Organic Solvent Mixtures
No full textProceedings (senza ISBN) della Scuola “Summer School on Experimental Methods in the Thermodynamics of Fluids”, Zakopane (PL), 11-17 settembre 198
Solubility Measurements in Dense Gases: Experimental Methods
No full textProceedings (senza ISBN) della Scuola "Summer School on Experimental Methods in the Thermodynamics of Fluids", Zakopane (PL), 11-17 settembre 198
Phase Behaviour Prediction of Oil-Supercritical Solvent Systems
No full textLavoro presentato alla Conferenza “First Conference on Chemical and Process Engineering”, Firenze, 13-15 maggio 1993. -
This paper is related to the phase behavior prediction of an oil fraction in supercritical solvents.
The supercritical fluids investigated in this work are n-hexane and n-heptane using equilibrium data from our laboratory and from literature .
We can consider the oil fraction, (boiling point range: 230-350°C), made by two homogeneus subfractions, a paraffinic-like fraction and an aromatic-like fraction.
These cuts can be obtained by chromatographic separation (1) and analyzed by simulated distillation.
From the informations obtained throught analytical data is possible to find two components, having the same molecular weight of the fraction, one paraffinic and one aromatic, for representing the two subfractions .
The procedure, tested in previous works (2, 3), considers a thermodynamic model (PHCT equation) proposed by Cotterman et al. (4).
The parameters of the pure component have a physical meaning and they can be correlated with the molecular weight within an homologous class.
From the knowledge of these properties and by means of experimental binary data, from literature, of the two systems, solvent with paraffinic and aromatic compound, it is possible the calculation of the PHCT binary interaction coefficients.
Starting from these binary coefficients we can predict the phase behavior of the solvent-oil fraction system
Production of Drugs by Antisolvent Precipitation
No full textProceedings (senza ISBN) del "XIV Congresso dell Divisione di Chimica Industriale della Società Chimica Italiana: Nuovi Orientamenti nell’Industria Chimica”, Milano (I), 3-4 ottobre 2001. -
In many cases the dimensions of the particles and the size distributions in solids obtained from chemical reactions, extractions processes, or crystallization operations do not correspond to the desired standards for the practical applications. A recrystallization process is needed in order to satisfy the standards. The milling process, the thermal recrystallization, and the liquid-antisolvent recrystallization are the most commonly techniques used. Applying these methods may cause a problem with decomposition of the solid due to the high temperatures involved and furthermore it is difficult to obtain a completely solvent-free product. These problems are avoided by use of processes based on supercritical fluids (SCF).
The two main techniques related to supercritical fluid recrystallization processes are the Rapid Expansion of a Supercritical Solution (RESS) and Gas Anti-Solvent recrystallization (GAS). In the RESS process a supercritical solution of the solvent and the solute(s) is expanded through a nozzle and the expansion decreases the solvent power of the supercritical solvent causing the precipitation of the solute. The RESS technique can only be applied to solutes soluble in a SCF, excluding a lot of heavy substances and almost all polymers, and thus making the technique of little interest for practical applications.
The GAS technique takes the advantage of the miscibility of the SCF with the organic solvent. When increasing the pressure by adding the anti-solvent (usually CO2), the solubility of the anti-solvent in the solvent is increased, and at a certain point the reduced solvent power of the mixed solvent causes solute precipitation. Finally, the solvent can be extracted by exploiting its solubility in the anti-solvent, and a dry and pure solute can be obtained
Thermodynamic of Perfluoeoethers: Organic Solvent Mixtures
No full textProceedings (senza ISBN) del Congresso "International Symposium on Thermodynamics in Chemical Engineering and Industry", Pechino (CN), 30 maggio – 2 giugno 1988
Utilizzazione di Solventi Paraffinici a Diverso Peso Molecolare nel Processo di Deasfaltazione
No full textProceedings (senza ISBN) del Congresso "I Fluidi Supercritici e le loro Applicazioni", Amalfi (SA), 24-25 giugno 1991
Applicazioni Analitiche e Preparative della Cromatografia Supercritica
No full textProceedings (senza ISBN) della Conferenza "Applicazioni in Campo Farmaceutico e Biotecnologico dei Fluidi Supercritici", Auditorium Fedegari Albuzzano (PV), 20 aprile 1995
Polymer Characterization by GLC: Influence of Polymer Structure (Polybutadienes)
No full textProceedings (senza ISBN) del Congresso “Fourth Asian Chemical Congress”, Pechino (CN), 26-30 agosto 1991
The infinite dilution activity coefficient of a solvent in a polymer is a thermodynamic property which can given useful information about the interactions between the components. This property can be determined by inverse gas chromatography, which enables to obtain reliable and accurate data in a relatively short time.
In this work activity coefficients at infinite dilution of various solvents, representative of the different classes of organic compounds, are determined in different polybutadienes.
The polymers were well characterized on the basis of structure and molecular weight. The influence of structure and of molecular weight of the polymer on the compatibility with the solvents is pointed out.
Comparison with available data obtained by different authors in similar polymers is reported. The results are qualitatively interpreted by using the Perturbed Hard Chain E0S developed by Cottermann and Prausnitz
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