Abstracts 1994 - 1996

Liu, Z.G., Cao, W.X., Sun, Y.H., Su, A.C.L., and Liotta, C.L., Synthesis of polycondensable anthraquinone dyes and coloured nylon fibres .1. Polymer International, 1996. 41 (4): p. 391-394.

The reaction of dihydroxyanthraquinone (DHA) and amines in the presence of catalyst has been reported. We found that DHA reacted easily with hexamethylenediamine in chloroform or toluene without addition of any catalyst, and mono- or dihexamethylenediamine-substituted anthraquinone, a violet green colourant, was formed. Using the colourant as a comonomer in the polycondensation of caprolactam or nylon-6,6 salt, coloured nylon-6 and nylon-6,6 fibres were prepared.

Sherman , S.R., Eckert , C.A. , and Scott, L.S., Modeling multicomponent equilibria from binary equilibrium data for reacting systems. Chemical Engineering and Processing, 1996. 35 (5): p. 363-371.

Although direct phase equilibria measurements of reacting systems are difficult to obtain generally, the thermodynamic behavior of a reacting system Such as that found in a reactive distillation processes can be constructed indirectly from measurements involving the phase equilibria of nonreacting pairs of compounds involved in the reaction in combination with an activity coefficient model. The binary data are used to regress binary interaction parameters for the chosen activity coefficient model. The ternary phase equilibria are estimated from the model. This work will describe the application of this method to the reactive system water/3-pentenoic acid/methyl-3-pentenoate. Vapor-liquid and liquid-liquid equilibrium measurements for the binary components were used to fit NRTL and UNIQUAC parameters. These activity coefficient models were then used to show how the composition-phase behavior can be constructed for the ternary system from the binary information only.

Eckert , C.A. , Knutson, B.L., and Debenedetti, P.G., Supercritical fluids as solvents for chemical and materials processing. Nature, 1996. 383 (6598): p. 313-318.

Fluids near their critical point have dissolving power comparable to that of liquids, are much more compressible than dilute gases, and have transport properties intermediate between gas- and liquid-like. This unusual combination of physical properties can be advantageously exploited in environmentally benign separation and reaction processes, as well as for new kinds of materials processing.

Yun, S.L.J., Dillow, A.K., and Eckert , C.A. , Density measurements of binary supercritical fluid ethane/cosolvent mixtures. Journal of Chemical and Engineering Data, 1996. 41 (4): p. 791-793.

Densities of binary supercritical mixtures of ethane with cosolvents, ethanol, 2,2,2-trifluoroethanol, and 1,1,1,3,3,3-hexafluoro-2-propanol, have been measured by a constant volume apparatus. Measurements were made in the range 0.7 to 2.0 mol % cosolvent and at pressures from 49.8 to 105.7 bar at 308.2 K. Despite the low cosolvent composition, all mixture densities deviate significantly from the density of pure ethane in the highly compressible region. Mixture densities calculated by the PR-EOS give only a qualitative representation of the experimental data.

Pouillot, F.L.L., Chandler , K., and Eckert , C.A. , Sublimation pressures of n-alkanes from C20H42 to C35H72 in the temperature range 308-348 K. Industrial & Engineering Chemistry Research, 1996. 35 (7): p. 2408-2413.

This paper presents a new predictive method for the sublimation pressures of heavy lt-alkanes from C20H42 to C35H72 in the temperature range 308-348 K. The peculiar behavior of solid n-alkanes in terms of their heats of solid transitions is reviewed briefly. Also, the behavior of heat capacities of the n-alkanes through the solid-solid transitions is discussed, and the relative importance of this behavior is evaluated. Finally, the new expression for the sublimation pressures of n-alkanes is compared with other available correlations.

Meredith, J.C., Johnston , K.P., Seminario, J.M., Kazarian, S.G., and Eckert , C.A. , Quantitative equilibrium constants between CO2 and Lewis bases from FTIR spectroscopy. Journal of Physical Chemistry, 1996. 100 (26): p. 10837-10848.

Equilibrium constants measured from the nu(2) bending mode of CO2 by FTIR spectroscopy are reported for the electron donor-acceptor interactions of CO2 with three Lewis bases: triethylamine(TEA), pyridine (PYR), and tributyl phosphate (TBP). The average K-c values are 0.046 (CO2-TEA), 0.133 (CO2-PYR), and 1.29 (CO2-TBP) L/mol at 25 degrees C in the solvent pentane. For the CO2-TBP system, the average enthalpy of association, Delta H degrees, is -4.7 kcal/mol. Ab initio calculations indicate that steric repulsion of the ethyl groups in TEA cause the binding energy of the CO2-TEA complex to be weaker than that of the CO2-PYR complex by 1.34 kcal/mol, a trend that is in agreement with our spectroscopic data. The lattice fluid hydrogen bonding model was used in conjunction with the spectroscopically determined K-c values to predict bubble points for the CO2-TEA and CO2-TBP systems and CO2 sorption in a hypothetical polymer. These calculations indicate that these relatively weak specific interactions have a measurable effect on phase behavior and can influence sorption of CO2 in polymers.

Dillow, A.K., Yun, S.L.J., Suleiman, D., Boatright, D.L., Liotta, C.L., and Eckert , C.A. , Kinetics of a phase-transfer catalysis reaction in supercritical fluid carbon dioxide. Industrial & Engineering Chemistry Research, 1996. 35 (6): p. 1801-1806.

The first example of a phase-transfer-catalyzed reaction carried out in a supercritical fluid (SCF) is reported. The kinetics of the nucleophilic displacement of benzyl chloride with a bromide ion in SCF solvent CO2 in the presence of acetone cosolvent is presented. In addition, the solubility of tetraheptylammonium bromide (THAB) in SCF CO2 in the presence of acetone cosolvent is reported. The reaction rate was measured at 50 and 75 degrees C at pressures to 200 bar; the reaction was found to follow first-order, reversible kinetics for the reactions catalyzed by THAB and zero-order kinetics for reactions catalyzed by 18-crown-6.

Eckert , C.A. and Sherman, S.R., Measurement and prediction of limiting activity coefficients. Fluid Phase Equilibria, 1996. 116 (1-2): p. 333-342.

Limiting activity coefficients are of both theoretical and practical interest. They provide direct information about unlike pair interactions in solution, without the need to use empirical g(E) models for concentration dependence. They also characterize a variety of important separation processes involving dilute solutions, especially in the environmental arena. New experimental and predictive methods are available for measurement, correlation, and estimation of gamma(infinity) data.

Kazarian, S.G., Vincent, M.F., and Eckert , C.A. , Infrared cell for supercritical fluid-polymer interactions. Review of Scientific Instruments, 1996. 67 (4): p. 1586-1589.

A novel high pressure cell for Fourier transform infrared studies of extraction, impregnation, partitioning, and interactions between supercritical fluids and polymers is presented. Two parallel optical paths through the cell permit the measurement of IR spectra of the supercritical fluid and the polymer sample under the same conditions without essential overlapping of the absorption bands studied. This cell has been applied to study the supercritical CO2 drying of poly(methyl methacrylate) using deuterated water to eliminate the overlap of the IR absorption bands of the stretching modes of water with the bands due to combination modes of CO2. The technique for attaining quantitative measurements of the partitioning of the solute between the supercritical fluid and polymer phases is described. (C) 1996 American Institute of Physics.

Sherman , S.R., Trampe, D.B., Bush, D.M., Schiller, M., Eckert , C.A. , Dallas , A.J., Li, J.J., and Carr, P.W., Compilation and correlation of limiting activity coefficients of nonelectrolytes in water. Industrial & Engineering Chemistry Research, 1996. 35 (4): p. 1044-1058.

The phase equilibria of dilute aqueous solutions are treated separately from those of dilute organic systems due to water's unique structure and hydrogen-bonding characteristics. As a result, traditional predictive methods (UNIFAC, ASOG, etc.) tend to be only moderately successful. In addition to inverse solubility measurements, we describe new direct and indirect techniques for precisely measuring these values which are more accurate. A database is compiled from data measured by using these techniques. The data were evaluated and suspect points removed. The data were correlated linearly with the solute solvatochromic alpha, beta, and pi*, solute and solvent molar volume, solute vapor pressure, and the solute gas-liquid partition coefficient between hexadecane and an inert gas phase, log L(16). The correlation fits the data to within an average absolute deviation of 0.294 In units. The correlation provides a direct and relatively accurate method for estimating Henry's constants and thus limiting activity coefficients of nonelectrolytes in water.

Kazarian, S.G., Vincent, M.F., Bright, F.V., Liotta, C.L., and Eckert, C.A., Specific intermolecular interaction of carbon dioxide with polymers. Journal of the American Chemical Society, 1996. 118 (7): p. 1729-1736.

Fourier transform IR spectroscopy has been used to investigate the interaction of carbon dioxide with polymers. IR transmission and attenuated total reflectance spectra were obtained for CO2 impregnated into polymer films. It has been shown that the polymers possessing election-donating functional groups (e.g., carbonyl groups) exhibit specific interactions with CO2, most probably of Lewis acid-base nature. An unusual aspect is the use of the bending mode (nu(2)) of CO2 to probe polymer-CO2 interactions. The evidence of the interaction is the observation of the splitting of the band corresponding to the CO2 nu(2) mode. This splitting indicates that the double degeneracy of the nu(2) mode is removed due to the interaction of electron lone pairs of the carbonyl oxygen with the carbon atom of the CO2 molecule. This splitting has not been observed for polymers lacking electron-donating functional groups (e.g., poly(ethylene)). In contrast, the nu(3) made shows little if any sensitivity to this interaction, which is in accordance with the interaction where CO2 molecule acts as an electron acceptor. Finally, the chemical and engineering implications of this type of specific interaction of CO2 with polymers are discussed; perhaps the changes in spectra of CO2 incorporated into polymers might serve as a basis for prediction of the solubility of CO2 in polymers.

Chandler , K., Pouillot, F.L.L., and Eckert , C.A. , Phase equilibria of alkanes in natural gas systems .3. Alkanes in carbon dioxide. Journal of Chemical and Engineering Data, 1996. 41 (1): p. 6-10.

A chromatographic technique was used to measure experimental capacity factors for the n-alkanes from C9H20 to C36H74 in CO2 from 308.2 to 348.2 K and from 100 to 240 bar. Infinite dilution activity coefficients, gamma(i)(infinity), were calculated for the solid n-alkanes (C24H50 to C36H74) utilizing regular solution theory to characterize the stationary phase. This allowed the estimation of solubilities from capacity factors for the solid n-alkanes in CO2.

Knutson, B.L., Dillow, A.K., Liotta, C.L., and Eckert , C.A. , Kinetics of a Diels-Alder reaction in supercritical propane , in Innovations in Supercritical Fluids . 1995. p. 166-178.

The kinetics of the Diels-Alder reaction of maleic anhydride (MA) and 2,3-dimethyl-1,3-butadiene (DMB) were studied in supercritical fluid propane solutions in the temperature range of 100-140 degrees C and at densities of 6-10 moles/liter, both in excess DMB (a reactive cosolvent) and also in the presence of an unreactive cosolvent (2-10 mole% 2,2,2-trifluoroethanol (TFE)). In the reactive cosolvent systems, low density results at 100 degrees C and 120 degrees C were not in agreement with activation volumes estimated from a cubic equation of state. The effect of unreactive cosolvent on the reaction rate was minimal. Anomalies observed may be the result of a reactive cosolvent-enhanced solute environment in near-critical solutions or enhanced secondary interactions in the transition state.

Kaylor, R.M., Dimmel, D.R., Ragauskas, A.J., and Liotta, C.L., A New Model-Compound for Studying Alkaline Cellulose Chain Cleavage Reactions. Journal of Wood Chemistry and Technology, 1995. 15 (4): p. 431-452.

A conformationally rigid cellulose model, the 4',6'-O-benzylidene derivative of 1,5-anhydrocellobiitol, has been studied to learn more about the mechanisms of chain cleavage reactions under alkaline pulping conditions. Heating the model at 170 degrees C in 2.5N NaOH gave 55% glycon-oxygen (G-O) bond cleavage, and similar to 45% oxygen-aglycon (O-A) bond cleavage. The amount of observed O-A bond cleavage is significantly higher than that for 1,5-anhydrocellobiitol. The benzylidene model also degraded about similar to 35% faster than 1 5-anhydrocellobiitol; much of this rate increase can be attributed to a faster rate of O-A bond cleavage for the benzylidene model. The greater amount of O-A bond cleavage in the benzylidene case may be attributable to a more highly substituted glycosyl ring (making the ring a better anion leaving group) and/or to a more conformationally inflexible glycosyl ring. The inflexibility restricts one of the standard G-O bond cleavage mechanisms, namely the S(N)icB(2') mechanism. The results point out the value of choosing appropriate cellulose models.

Sherman, S.R., Suleiman, D., Hait, M.J., Schiller, M., Liotta, C.L., Eckert, C.A., Li, J.J., Carr, P.W., Poe, R.B., and Rutan, S.C., Correlation of Partial Molar Heats of Transfer at Infinite Dilution by a Linear Solvation Energy Relationship. Journal of Physical Chemistry, 1995. 99 (28): p. 11239-11247.

Linear solvation energy relationships and solvatochromic parameters have been used to develop an improved relationship for the partial molar heats of transfer of an infinitely dilute solute in nonionic solutions which appears to be accurate to +/-4% for the database tested. This result has been coupled with a thermodynamic cycle in order to develop a corresponding correlation for the partial molar excess enthalpy at infinite dilution, h(E infinity). However, because this result represents the difference of large: numbers, the accuracy of prediction of h(E infinity) is only accurate to about +/-28%. The correlation presented provides the insight for understanding, on a chemical and physical basis, the temperature effect on the phase equilibria of dilute solutions.

Eckert , C.A. , Pouillot, F.L.L., Knutson, B.L., Gurdial, G.S., and Scott, L.S., Selective Separation of Valeric Acid from Dibasic Acids Using Supercritical Carbon-Dioxide. Journal of Supercritical Fluids, 1995. 8 (1): p. 1-5.

Separations of coproduct valeric acid from mixed dibasic acids is essential for a new process of producing adipic acid for nylon production. The batch fractionation of valeric acid from mixtures of valeric acid and dibasic acids consisting of methyl glutaric acid and ethyl succinic acid was carried Out with supercritical carbon dioxide using a continuous flow saturation apparatus. Phase equilibria of valeric acid and mixtures of valeric acid with methyl glutaric acid with supercritical carbon dioxide were measured in the range 35-65 degrees C and 68-140 bar. Apparent equilibrium of a mixture of valeric acid, methyl glutaric acid, and ethyl succinic acid with carbon dioxide is also reported. A high-pressure view-cell allowed visual observation of the number of phases present. Results indicate that highly selective removal of valeric acid is possible from the mixtures of dibasic acids using supercritical carbon dioxide at 50 degrees C and 90 bar, with loadings of valeric acid close to 0.1 mol %. Solubility of valeric acid in the fluid phase was increased to almost 6.5 mol % at 50 degrees C and 138 bar but with a decrease in the selectivity for valeric acid. The data obtained were correlated using the Peng-Robinson equation with conventional quadratic mixing rules.

Suleiman, D. and Eckert , C.A. , Phase-Equilibria of Alkanes in Natural-Gas Systems .2. Alkanes in Ethane. Journal of Chemical and Engineering Data, 1995. 40 (3): p. 572-577.

A previously reported novel chromatographic technique for measuring capacity factors to yield infinite dilution activity coefficients for liquid and solid n-alkanes in compressed gases can be used to estimate solubilities, virial coefficients, partial molar volumes, and partial molar enthalpies at infinite dilution. This paper reports experimental capacity factors and their corresponding solubilities for the n-alkanes from C24H50 to C36H74 in C2H6 from 308.2 to 348.2 K and from 80 to 240 bar. The results are interpreted according to the physical differences observed between even- and odd-numbered solid n-alkanes.

Tomasko, D.L., Macnaughton, S.J., Foster, N.R., and Eckert , C.A. , Removal of Pollutants from Solid Matrices Using Supercritical Fluids. Separation Science and Technology, 1995. 30 (7-9): p. 1901-1915.

Several supercritical fluid extraction (SCFE) processes have been proposed for removing toxic and intractable organic compounds from a range of contaminated solids. These include soil remediation and the regeneration of adsorbents used to treat wastewater streams such as granular activated carbon (GAG). As a separation technique for environmental control, SCFE has several distinct advantages over conventional liquid extraction methods and incineration. Most notably, the contaminant is removed from the solvent in a concentrated form via a change in pressure or temperature and can be completely separated upon expansion to atmospheric pressure. The viability of SCFE hinges on process conditions such as solvent-feed ratio and solvent recycle ratio. The necessity of recycling solvent complicates the contaminant separation step since a complete reduction to atmospheric pressure would create large recompression costs. Because of this, the pressure and temperature dependence of contaminant solubility must be understood so that operating conditions for the separation step can be defined. Fortunately, this is the most developed aspect of SCF technology. However, the mass transfer limitations to removing contaminants from solids change with solvent flow rate. This paper discusses the use of SCFE for environmental control and presents results for the removal of DDT and 2-chlorophenol from GAG. 2-chlorophenol is almost completely removed with pure CO2 at 40 degrees C and 101 bar while only 55% of the DDT is removed at 40 degrees C and 200 bar. These differences in regeneration efficiency cannot be understood solely in terms of solubility but point to a need for detailed studies of adsorption equilibrium and mass transfer resistances in supercritical fluid systems.

Suleiman, D. and Eckert , C.A. , Phase-Equilibria of Alkanes in Natural-Gas Systems .1. Alkanes in Methane. Journal of Chemical and Engineering Data, 1995. 40 (1): p. 2-11.

We report the application of a new chromatographic technique to measure capacity factors for several n-alkanes (C7H16 to C36H74) in methane in the range 293.2-423.2 K, and at 120-240 bar. Regular solution theory is used to characterize the stationary phase to permit the calculation of infinite dilution activity coefficients, gamma(i)(infinity); this allows the conversion of the capacity factors to estimates of the solubility of the n-allranes in methane. The solubility results are in good agreement with those data available from more conventional techniques. However, the new method permits investigations of much lower values of the solubility, especially for heavier hydrocarbon solutes, typically inaccessible with other methods. The capacity factor data can also be differentiated to yield directly partial molar volumes and partial molar enthalpies at infinite dilution. The phase equilibrium information obtained with this method provides valuable data for understanding size differences, as well as for helping to ameliorate solid deposition problems of natural gas companies.

Suleiman, D. and Eckert , C.A. , Limiting Activity-Coefficients of Diols in Water by a Dew-Point Technique. Journal of Chemical and Engineering Data, 1994. 39 (4): p. 692-696.

Limiting activity coefficients for 1,2-ethanediol (ethylene glycol), 1,2-propanediol (propylene glycol), 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol and 2,3-butanediol in water were measured over a range of temperatures (297-348 K). The recently developed dew point technique used in this investigation is especially suitable to this type of system with very low relative volatility (e.g., <0.5), where other methods are inapplicable. The experimental results were compared with extrapolated vapor-liquid equilibrium (VLE) data, demonstrating the inadequacy of extrapolating VLE data to gamma(infinity) for complex hydrogen-bonded systems. A one-parameter Wilson equation was used to characterize the results and to estimate gamma(infinity) for water in the diols. Partial molar excess enthalpies at infinite dilution were estimated from the temperature derivative of the limiting activity coefficients. The results are discussed in terms of inter- and intramolecular hydrogen bonding.

Ashby, E.C., Barefield, E.K., Liotta, C.L., Neumann, H.M., Doctorovich, F., Konda, K., Zhang, K., Hurley, J., Boatright, D., Annis, A., Pansino, G., Dawson, M., and Juliao, M., Mechanistic Studies Related to the Thermal Chemistry of Simulated Nuclear Wastes That Mimic the Contents of a Hanford-Site Double-Shell Tank , in Emerging Technologies in Hazardous Waste Management Iv . 1994. p. 249-284.

Certain aspects of the thermal reactions of organic complexants in simulated aqueous nuclear waste mixtures containing NaOH, NaNO2, NaNO3 and NaAl(OH)(4) have been investigated. Since formaldehyde is expected as a degradation product from various complexants, the factors affecting the reaction by which H-2 gas is formed from formaldehyde and OH have been studied. A mechanism consistent with these results is presented. The source of the nitrogen atoms in the gases N2O, N-2, and NH3 formed from the degradation of HEDTA has been determined using N-15 labeling experiments. It was found that the nitrogens in N2O and N-2 are produced from NaNO2 whereas 88% of the nitrogen in NH3 come from NaNO2 and 12% come from HEDTA. A number of degradation products formed in series in the long-term thermal degradation of HEDTA at 120 degrees C were identified by C-13 NMR. In the reaction of glycolate in simulated waste, formate and oxalate are formed, and nitrite (but not nitrate) decreases in amount. Kinetic studies involving glycolate decomposition have resulted in the determination that the reaction is first order in each of the reactants: glycolate, nitrite, and aluminate. A mechanism is proposed for decomposition of glycolate. A scheme for the sequential degradation of HEDTA, based on the same mechanistic ideas, is also presented. Finally,some observations on the effect that O-2 has on the decomposition of organics and on the gas generation in simulated waste are given.

GA Tech home