Kunio Nagahama

Generalized interaction parameters for the Peng—Robinson equation of state: Carbon dioxide—n-paraffin binary systems

Abstract In order to obtain better representation of the phase equilibria in CO2-containing binary mixtures, a new procedure is proposed for evaluating the binary parameter δij of the Peng—Robinson equation of state. By introducing a newly defined function, optimum values of δij are determined for each isotherm of binary systems containing CO2 and C1–C10 n-paraffins. Further, for every binary system, δij is expressed in terms of absolute temperature as a quadratic function of which three coefficients are generalized functions of the n-paraffin acentric factor.

Solubilities of ethanol, 1-propanol, 2-propanol and 1- butanol in supercritical carbon dioxide at 313 K and 333 K

Abstract Suzuki T., Tsuge N. and Nagahama K., 1991. Solubilities of ethanol, 1-propanol, 2-pro-panol and 1-butanol in supercritical carbon dioxide at 313 K and 333 K. Fluid Phase Equilibria, 67: 213-226. Using a flow-type apparatus for supercritical fluid extraction, solubilities of an alcohol in supercritical CO2 have been measured at 313 K and 333 K up to 11 MPa. Ethanol, 1-propanol, 2-propanol and 1-butanol were selected as the alcohols. Consistency of the obtained solubility data was tested by the enhancement factor method, which showed good consistency for all systems. The logarithmic values of the enhancement factors for all the alcohols were observed to be linear functions of pure CO2 density. Employing this linear relationship, the solubility of an alcohol in supercritical CO2 can easily be determined with high accuracy.

Solubility of organic solid mixture in supercritical fluids

An experimental determination of the solubilities of solid mixture in supercritical (SC) fluids was made. By use of a continuous gas flow apparatus, the solubilities of naphthalene + phenanthrene in SC-CO2, phenanthrene in SC-fluoroform (CHF3), and naphthalene + phenanthrene in SC-fluoroform have been measured at 308.2 K and 4.8 to 28 MPa. The solubilities of a component for the two solid-mixture system have been enhanced as much as 130% higher than that for a single pure solid system at the same temperature and pressure. For the naphthalene + phenanthrene mixture, the selectivities between these components in fluoroform were higher than those in carbon dioxide. Finally the experimental solubilities were correlated using not only three equations of state but also two empirical density dependent equations.

Representation of activity coefficients of fundamental biochemicals in water by the UNIFAC model

Abstract The assignment of UNIFAC parameters has been newly examined to represent the activity coefficients of fundamental biochemicals in aqueous solutions containing sugars, imino acids, urea, amino acid salts, inorganic salts, and sugar salts. In this work, several new groups have been introduced to represent the activity coefficients for many biochemicals with better accuracy. For sugars, a portion containing asymmetric carbon atoms in an aldohexose molecule was defined as a new group for many stereoisomers. In the case of electrolytes like amino acid salts, the Pitzer-Debye-Huckel term was added to the UNIFAC equation to take the long-range electrostatic interaction into account. All new interaction parameters for the fundamental biochemicals have been determined from osmotic coefficient as well as activity coefficient data reported in the literature. The new parameters provided good calculated results for these biochemicals. In addition, the activity coefficient data for the ternary systems water/amino acid/urea and water/amino acid/sucrose were used to determine the interaction parameters between the constituent groups of an amino acid and those of the second solute, urea or sucrose. The correlated results for the system containing urea were in satisfactory agreement with the literature data.

Measurements of Solubilities of Two Amino Acids in Water and Prediction by the UNIFAC Model

The solubility of an amino acid in an aqueous solution containing another amino acid was measured at 298 K. The measured amino acid pairs were dl‐alanine/dl‐serine and dl‐alanine/dl‐valine. The invariant eutectic compositions of these pairs of amino acids were also determined. In addition, a prediction model of solubility for such a system was developed on the basis of solid−liquid equilibria. To represent more accurately the activity coefficient of amino acids and homopeptides by Larsens UNIFAC model, new assignments of UNIFAC groups were proposed and their interaction parameters were determined from experimental osmotic coefficient data. Finally, the prediction of solubilities of mixed solid amino acids was made and the results were compared with experimental data.

Permeation rates of aqueous alcohol solutions in pervaporation through Nafion membranes

Abstract Permeation data of methanol-water and 1-propanol-water mixtures in pervaporation (PV) through Nafion membranes with (CH 3 ) 3 NH + as counter ion were obtained. These data showed that water preferentially permeated in PV in spite of the preferential sorption of alcohols. A new permeation model was proposed based on the free volume theory. The model accounted for the effects of solubility and molecular interactions, such as permeant-polymer interactions, on the permeability. Not only the PV data of methanol-water-Nafion and 1-propanol-water-Nafion systems but also those of ethanol-water-nafion and isopropanol-water-Nafions systems listed in the literature supported the validity of the present model.

Extraction of polyunsaturated fatty acid ethyl esters from sardine oil using Ag+-containing o/w/o emulsion liquid membranes

Using silver ion as a carrier in o/w/o type emulsion liquid membranes, batch-wise extraction experiments were performed to separate polyunsaturated fatty acid ethyl esters originating in sardine oil. It was possible to separate polyunsaturated fatty acid (PUFA) esters from the mixture of PUFA and saturated fatty acid esters. The operating conditions for stable liquid membranes were experimentally determined. A new membrane breakage model that successfully describes the membrane stability behavior is proposed.

Recovery of protein from reverse micelles through gas hydrate formation

The recovery of cytochrome c and ribonuclease A from di-2-ethylhexyl sodium sulfosuccinate (AOT) reverse micelles have been examined by the gas hydrate formation. The recovery of cytochrome c depended upon the kind of gas and the water content (w0=[H2O]/[AOT]) of reverse micellar solution containing cytochrome c prepared. Recoveries of cytochrome c and ribonuclease A were more than 80%, when 1,1,1,2-tetrafluoroethane (TFE) was used as a hydrating gas. The activity of cytochrome c recovered from reverse micelles was maintained perfectly.

Enzymatic synthesis of peptide in acetonitrile/supercritical carbon dioxide

SummaryThe peptide synthesis from N-acetyl-L-tyrosine ethyl ester (Ac-Tyr-OEt) and amino acid amides was realized using α-chymotrypsin (CT) in acetonitrile (MeCN) or acetonitrile/supercritical carbon dioxide (SCCO2) containing small amounts of water. In both solvent systems there was an optimum water content for peptide synthesis, above which peptide hydrolysis became more important. After an incubation for 5 hours, the yields of the peptide was 64% in MeCN and 91% in MeCN/SCCO2, respectively.

Increased Thermostability of Cross-Linked Enzyme Crystals of Subtilisin in Organic Solvents

Cross-linked enzyme crystals(CLECs) of subtilisin display the improved thermostability in organic solvents, compared to free subtilisin. CLECs are more stable than the free enzyme in octane with a half life of 200 days at 45°C, while that of free enzyme is 5.4 days. CLECs in octane is more stable than in acetonitrile.