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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 18 (1972), S. 299-304 
    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 method is described for solving the problem: given fixed pressure, temperature, the amounts of the chemical elements, and the chemical potentials of possible chemical species at the pressure and temperature specified, determine the equilibrium composition. The method requires a minimum of judgment on the part of the user.A modification of Naphtali's method for direct minimization of Gibbs' function provides an estimate of the composition of sufficient accuracy to insure convergence of solution, by the Newton-Raphson method, of the nonlinear equations describing the equilibrium.Problems in treating multiple phaes of unknown stability and chemical species present in small amouts are handled by ignoring unstable phases and small quantitites in the direct minimization until the amounts of the major consitituents have been at least approximately determined. To accomplish this, species temporarily ignored are assigned a ficitious mol fraction so that their re-entry into the calculation can be established. Truncation errors in the direct minimziation can be tolerated because of the two-step method.Examples of some of the problems solved are given.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 19 (1973), S. 1055-1059 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 22 (1976), S. 147-152 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Transient diffusion of n-butane, iso-butane, and 1-butene in synthetic CaX(Na) spherical pellets is studied in a constant volume, well-stirred system. The intracrystalline diffusion coefficients are in the order of 10-14 cm2/s, and the activation energy is about 7.0 Kcal/g-mole. Experimental data agree well with a mathematical model developed to describe transient diffusion.
    Additional Material: 8 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 36 (1990), S. 1569-1576 
    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 mathematical analysis for the pulse responses of a liquid chromatographic column packed with crystal powders having a particle size distribution and a nonlinear adsorption isotherm is presented. The mathematical model is solved numerically by the orthogonal collocation method. Based on the parametric analysis of the model, the effects of a symmetrical and moderately asymmetric PSD on the LC responses are shown to be negligible in comparison with the effects of other parameters, such as isotherm nonlinearity, whose effects are much more profound. The simulated responses are compared with the experimental response data for an LC column packed with silicalite crystals, and a good agreement is found between the theoretical and experimental results. Using the nonlinear LC model, the simultaneous determination of nonlinear adsorption isotherms and intraparticle diffusivities from LC pulse responses is demonstrated for liquids in porous adsorbents.
    Additional Material: 6 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 58-67 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Theoretical models of gas diffusion and permeation in microporous molecularsieve membranes are presented. The effect of the adsorbed diffusant on the total transmembrane flow is insignificant for permanent gases. For highly adsorbable gases the effect of the adsorbed molecules on the total transmembrane flux may be high at low temperatures. The activation energy of diffusion increases when the kinetic diameter of the diffusant increases. The activation energy of gas diffusion compares well with the values calculated based on the Lennard-Jones potential. Maximum possible permeability coefficients calculated for He in the molecular-sieve membranes do not exceed ˜30,000 Barrer at room temperature. The experimentally observed value for He permeability is ˜1,000 Barrer (T=30°C) because of the high tortuosity (τ≍ 25) and low porosity (θ = 0.22) of the membrane porous structure.
    Additional Material: 10 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 20 (1974), S. 279-284 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Transient sorption rates of allene and methylacetylene in synthetic faujasite (Linde 13X) powder and self-bonded pellets are studied in a constant-volume, constant-pressure system at three temperatures. The intracrystalline diffusion coefficients are found to be in the order of 10-11 cm2/s and the activation energy for diffusion is 4.0 kcal/g-mole.A simple bipore distribution model for transient diffusion in macropores and micropores is presented. It agrees well with the experimental data and quantitatively predicts the macropore diffusion coefficients. The flow in the macropores is found to be in the Knudsen flow regime.
    Additional Material: 6 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 33 (1987), S. 1233-1240 
    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 gradientless reactor was used to study the xylene isomerization reaction over a series of cation-exchanged (H+, Li+, Na+, and K+) ultrastable faujasite and on ZSM5 and silicalite to observe the effects of site modification on the reaction. Adsorption, diffusion, and kinetic parameters were determined in the presence of the reaction; the results generally agreed with the available literature data. The gradientless reactor and associated modeling techniques are shown to be effective tools in investigating catalyst behavior. Precise analytical techniques are required to directly measure the diffusion coefficient in the presence of reaction.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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