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  • 1
    Electronic Resource
    Electronic Resource
    Reformulation of Wong-Sandler mixing rule for cubic equations of state (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 683-690 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The cubic equation of state mixing rule of Wong and Sandler is reformulated in a way that eliminates one of its parameters and so that it can go smoothly from activity coefficient-like behavior to the classical van der Waals one-fluid mixing rule merely by variation of its parameters. The parameters in the reformulated mixing rule can be obtained from correlation of vapor-liquid equilibrium data or from the two infinite dilution activity coefficients for each binary pair in the mixture. When these activity coefficients are estimated from the UNIFAC group contribution model, the mixing rule becomes completely predictive. The correlative and completely predictive forms of this mixing rule are tested here and shown to be accurate for five difficult binary systems and one ternary mixture over large ranges of temperature and pressure.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410325
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  • 2
    Electronic Resource
    Electronic Resource
    Letters to the Editor (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 737-740 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410332
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  • 3
    Electronic Resource
    Electronic Resource
    Phase equilibria for the mean-force potential of globular protein solutions (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 218-231 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When polymers are added to a solution containing proteins, the protein may deposit as an amorphous precipitate or as crystals. Experimental evidence indicates that from a thermodynamic viewpoint, an amorphous precipitate should be treated as a liquid phase dense in the protein and crystals as true solids. To understand the conditions under which protein precipitation or crystallization may occur, Gibbs-ensemble Monte Carlo simulation and Gibbs-Duhem integration techniques are used to calculate the liquid-liquid and liquid-solid phase boundaries for protein precipitation induced by polymers. In these simulations, the system is modeled using the pseudo-one-component approximation with an appropriate potential of mean force. The critical point for fluid-fluid phase equilibrium disappears as the attractive part of the mean-force potential becomes very short ranged. The accuracy of the second-order Barker and Henderson perturbation theory is examined by comparing the phase diagram predicted using this method with the simulation results. Perturbation theory is able to predict the general trends observed in the simulations but not with quantitative accuracy. Perturbation theory is then used to examine a broader range of conditions for protein deposition.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430124
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  • 4
    Electronic Resource
    Electronic Resource
    The Benzylphenylether thermolysis mechanism: Insights from phase behavior (1990)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 36 (1990), S. 1129-1136 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The thermolysis of benzylphenylether (BPE) was examined at 320°C in liquid, vapor, and supercritical methanol phases as a probe of the reaction mechanism. Toluene and phenol were the major products in all cases, but observed selectivities were dependent upon the reaction phase. Isotopic labeling experiments demonstrated that methanol participated in the reaction network as a hydrogen donor through a free-radical mechanism. These results are consistent with free-radical steps for neat BPE primary pyrolysis that include BPE fission followed by hydrogen abstraction and radical recombination reactions. A detailed set of 21 free-radical steps quantitatively explains the dependence of the selectivity and conversion on the phase behavior.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690360802
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  • 5
    Electronic Resource
    Electronic Resource
    Computer simulation of molecular fluid mixtures: Results and two new one-fluid models (1993)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 663-676 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Monte Carlo simulation results for binary mixtures of diatomic molecules with spheres, diatomic molecules of different bond lengths, and triatomic molecules with spheres, all interacting with the site-site Lennard-Jones potential, were obtained at three different volume ratios and a range of densities and compositions. We report the configurational internal energy of the mixture and of the 1-1, 1-2 and 2-2 pairs, and the compressibility factors at 195 state points. The site-site correlation functions also computed are available from the authors. Equations of state derived previously (Sowers and Sandler, 1991, 1992) for pure site-site Lennard-Jones fluids from a combination of perturbation theory and a three-parameter corresponding states principle are extended to mixtures using simple one-fluid mixing rules. These simple mixing rules allow us to make satisfactory predictions of the compressibilities computed from simulation without the use of binary interaction parameters. We also show that the effect of composition on the perturbation free energy βAp/N not accounted for by one-fluid mixing rules is quite small, and therefore a more complicated mixing rule is not necessary in our equations of state for the mixtures studied.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690390415
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  • 6
    Electronic Resource
    Electronic Resource
    Thermodynamics of hydrogen bonding from molecular orbital theory: 1. Water (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1589-1596 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To reduce the number of adjustable parameters that appear in the thermodynamic modeling of hydrogen-bonding fluids, the use of ab-initio molecular orbital calculations in the form of Hartree-Fock and density functional theories to compute thermodynamic properties are considered. In particular, the enthalpy and entropy changes on hydrogen bonding for water are computed. The theory, the computational methods and the basis sets used, as well as the results for water, are discussed. The results obtained are compared with those of others and with experimental estimates from the literature to determine the validity of the methods that are then used in this extended study. The results obtained here are also used to examine the validity of mixture group contribution results obtained here are also used to examine the validity of mixture group contribution methods for hydrogen-bonding mixtures, to develop simple estimation procedures for model parameters, and to reduce the number of calculations such as those as those described that need to be done.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430622
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  • 7
    Electronic Resource
    Electronic Resource
    Analysis of excess free energy based equations of state models (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 2327-2334 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A comparison is made of the capabilities of various equation of state (EOS) + excess free energy (Gex) models in representing the activity-coefficient models they incorporate. Such EOS models need to reproduce the excess Gibbs free energy behavior of the activity-coefficient models as closely as possible in order to represent low-pressure vapor-liquid equilibrium behavior of complex mixtures accurately, and also to make accurate the vapor-liquid predictions at higher temperatures and pressures using only low-pressure information. It is demonstrated that the EOS models that use the excess Helmholtz free energy instead of the excess Gibbs free energy, and that combine the EOS with activity-coefficient models at the infinite pressure limit, are successful for calculations of the type just described.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420822
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  • 8
    Electronic Resource
    Electronic Resource
    A theoretically correct mixing rule for cubic equations of state (1992)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 671-680 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new mixing rule developed for cubic equations of state equates the excess Helmholtz free energy at infinite pressure from an equation of state to that from an activity coefficient model. Use of the Helmholtz free energy insures that the second virial coefficient calculated from the equation of state has a quadratic composition dependence, as required by statistical mechanics. Consequently, this mixing rule produces the correct low- and high-density limits without being density-dependent.As a test, the mixing rule is used for ternary mixtures of cyclohexane + benzene + water, ethanol + benzene + water and carbon dioxide + n-propane + water, and all the constituent binaries. The new mixing rule and a simple cubic equation of state can be used for the accurate correlation of vapor-liquid and liquid-liquid equilibria for binary mixtures. Using the parameters obtained from binary systems, the phase behavior of ternary mixtures can be predicted. Also, unlike previous empirical mixing rules, this theoretically based mixing rule is equally applicable and accurate for simple mixtures containing hydrocarbons and inorganic gases and mixtures containing polar, aromatic and associating species over a wide range of pressures. This mixing rule makes it possible to use a single equation of state model with equal accuracy for mixtures usually described by equations of state and for those traditionally described by activity coefficient models. It is the correct bridge between these two classes of models.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690380505
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  • 9
    Electronic Resource
    Electronic Resource
    Vapor-liquid equilibrium of polymer solutions using a cubic equation of state (1994)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 1203-1209 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A recently proposed mixing rule has been combined with a cubic equation of state to correlate the vapor-liquid equilibria of various polymer + solvent and solvent + long chain hydrocarbon mixtures. We find that the two-parameter version of this model can correlate the solvent partial pressure in concentrated polymer solutions with high accuracy over a range of temperatures and pressures with temperature-independent parameters. For the solvent + long chain hydrocarbon systems, for which accurate vapor-phase concentrations are also important, the model is best used as a three-parameter correlation. Advantages of this approach are that it extends the application of cubic equations of state to polymer + solvent systems in a simple fashion and that generally only temperature-independent parameters are required which allow for accurate interpolation and extrapolation of available data.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690400711
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  • 10
    Electronic Resource
    Electronic Resource
    Thermodynamics of hydrogen bonding from molecular orbital theory: 2. Organics (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1597-1604 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Hartree-Fock theory and density functional theory were used to compute the enthalpy and entropy changes of dimerization for a number of hydrogen-bonding compounds. In Part 1, the calculational methods and procedures use for the water dimer are described, and the results obtained are compared with those of others and with experimental estimates in the literature. Here, a variety of organic compounds that can self associate and/or cross associate are considered. The results obtained for the self-association of these compounds are compared with estimates obtained from various types of experimental data. The results are also used to examine the validity of group-contribution methods for hydrogen-bonding mixtures and to test a simple estimation procedure for cross dimerization that can reduce the number of calculations, such as those described here, that need to be done.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430623
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