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  • 1
    Electronic Resource
    Electronic Resource
    Sensitivity of PSA process performance to input variables (1995)
    Springer
    Adsorption 1 (1995), S. 133-151 
    Details
    ISSN: 1572-8757
    Keywords: PSA process ; sensitivity ; equilibria ; kinetics ; heats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Mathematical models for pressure swing adsorption (PSA) processes essentially require the simultaneous solutions of mass, heat and momentum balance equations for each step of the process using appropriate boundary conditions for the steps. The key model input variables needed for estimating the separation performance of the process are the multicomponent adsorption equilibria, kinetics and heats of adsorption for the system of interest. A very detailed model of an adiabatic Skarstrom PSA cycle for production of high purity methane from a ethylene-methane bulk mixture is developed to study the sensitivity of the process performance to the input variables. The adsorption equilibria are described by the heterogeneous Toth model which accounts for variations of isosteric heats of adsorption of the components with adsorbate loading. A linear driving force model is used to describe the kinetics. The study shows that small errors in the heats of adsorption of the components can severely alter the overall performance of the process (methane recovery and productivity). The adsorptive mass transfer coefficients of the components also must be known fairly accurately in order to obtain precise separation performance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00705001
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  • 2
    Electronic Resource
    Electronic Resource
    Why Does the Linear Driving Force Model for Adsorption Kinetics Work? (2000)
    Springer
    Adsorption 6 (2000), S. 137-147 
    Details
    ISSN: 1572-8757
    Keywords: adsorption ; kinetics ; linear driving force model ; process design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The Linear Driving Force (LDF) model for gas adsorption kinetics is frequently and successfully used for analysis of adsorption column dynamic data and for adsorptive process designs because it is simple, analytic, and physically consistent. Yet, there is a substantial difference in the characteristics of isothermal batch uptake curves on adsorbent particles by the LDF and the more rigorous Fickian Diffusion (FD) model. It is demonstrated by using simple model systems that the characteristics of the adsorption kinetics at the single pore or the adsorbent particle level are lost in (a) evaluating overall uptake on a heterogeneous porous solid, (b) calculating breakthrough curves from a packed adsorbent column, and (c) establishing the efficiency of separation by an adsorptive process due to repeated averaging of the base kinetic property. That is why the LDF model works in practice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008965317983
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  • 3
    Electronic Resource
    Electronic Resource
    Pure and Binary Gas Adsorption Equilibria and Kinetics of Methane and Nitrogen on 4A Zeolite by Isotope Exchange Technique (1999)
    Springer
    Adsorption 5 (1999), S. 145-158 
    Details
    ISSN: 1572-8757
    Keywords: kinetics ; isotope-exchange ; nitrogen ; adsorption ; methane ; zeolite ; equilibria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The Isotope Exchange Technique (IET) was used to simultaneously measure pure and binary gas adsorption equilibria and kinetics (self-diffusivities) of CH4 and N2 on pelletized 4A zeolite. The experiment was carried out isothermally without disturbing the adsorbed phase. CH4 was selectively adsorbed over N2 by the zeolite because of its higher polarizability. The multi-site Langmuir model described the pure gas and binary adsorption equilibria fairly well at three different temperatures. The selectivity of adsorption of CH4 over N2 increased with increasing pressure at constant gas phase composition and temperature. This curious behavior was caused by the differences in the sizes of the adsorbates. The diffusion of CH4 and N2 into the zeolite was an activated process and the Fickian diffusion model described the uptake of both pure gases and their mixtures. The self-diffusivity of N2 was an order of magnitude larger than that for CH4. The pure gas self-diffusivities for both components were constants over a large range of surface coverages (0 〈 θ 〈 0.5). The self-diffusivities of CH4 and N2 from their binary mixtures were not affected by the presence of each other, compared to their pure gas self-diffusivities at identical surface coverages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008917308002
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  • 4
    Electronic Resource
    Electronic Resource
    Equilibrium and kinetics of adsorption of Freon-12 at infinite dilution (1994)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 935-943 
    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: Equilibrium and kinetic data for adsorption of trace CF2Cl2 (Freon-12) from various carrier gases on BPL activated carbon are reported. Coadsorption of the bulk carrier gas can severely reduce the equilibrium adsorption capacity and adsorptive mass-transfer coefficient of strongly adsorbed CF2Cl2. The difference in size between CF2Cl2 and the bulk carrier gas molecules plays a major role in establishing the binary or multicomponent equilibrium adsorption properties. The multisite (single and multicomponent) Langmuir model, which accounts for differences in adsorbate sizes, provides a reasonable framework for describing the size effects. The adsorptive mass transfer of CF2Cl2 under the experimental conditions investigated is dominated by surface diffusion into the pores of the activated carbon. The surface diffusivity is a strong function of the extent of coverage and strength of adsorption of the bulk components.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690400604
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  • 5
    Electronic Resource
    Electronic Resource
    Sorption-enhanced reaction process (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 2765-2772 
    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 process for carrying out simultaneous reaction and separation of desired products in a single unit operation is described. It uses a fixed packed column of an admixture of a catalyst and a sorbent that selectively removes a reaction by-product from the reaction zone. The sorbent is periodically regenerated by using the principles of pressure-swing adsorption. The process steps allow direct production of the desired product at high purity and at the reaction pressure. High conversion of the reactants to products in an endothermic, equilibrium-controlled reaction can be achieved while operating the reaction at a substantially lower temperature than would be necessary by a plug-flow reactor packed with the catalyst alone. The equilibrium-controlled reverse water-gas shift reaction for the production of carbon monoxide is experimentally evaluated as a proof of the concept.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690421008
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  • 6
    Electronic Resource
    Electronic Resource
    Separation of bulk hydrogen sulfide-hydrogen mixtures by selective surface flow membrane (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2239-2245 
    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 separation performance of binary hydrogen sulfide-hydrogen mixtures by a nanoporous carbon membrane called selective surface flow (SSF) membrane is described. The membrane selectively permeates H2S from H2, and a H2-enriched stream is produced at the feed-gas pressure. A two-stage embodiment of the SSF membrane is described for production of high-purity H2 with high H2 recovery from an equimolar H2S-H2 feed gas. A novel protocol for operation of the two-stage membrane is needed to achieve that separation goal.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430910
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  • 7
    Electronic Resource
    Electronic Resource
    Estimation of surface diffusion through porous media (1990)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 36 (1990), S. 1249-1254 
    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 mathematical model is developed to describe steady-state nonequilibrium surface diffusion of an adsorbing gas through an energetically homogeneous porous medium by assuming that the adsorption isotherm is linear and that the gas-surface mass transfer can be described by the linear driving force model. Analytical solutions for the model are reported. It is found that the conventional assumption of local thermodynamic equilibrium between the gas and surface phases within the porous medium can seriously underestimate the surface diffusivity when the mass transfer rate is finite. Also, the length of the porous medium becomes a critical variable in that case.Meaningful estimation of surface diffusivity also requires that the gas phase diffusivity through the porous medium be accurately known. The estimated surface diffusivity is model dependent when local thermodynamic equilibrium is not established instantaneously. Modeling surface diffusion can be very complex when the surface is energetically heterogeneous.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690360814
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  • 8
    Electronic Resource
    Electronic Resource
    Kinetics and column dynamics for adsorption of bulk liquid mixtures (1992)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 811-820 
    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 framework is developed to describe kinetics and column dynamics of ad(de)sorption from bulk liquid mixtures using surface excess as the variable to quantify the extent of adsorption. It is found that the transient rate of change of surface excess with time from a multicomponent liquid mixture can be expressed in terms of a surface excess linear-driving-force model. A local-equilibrium model can be developed to describe the column dynamics of ad(de)sorption from liquid mixtures. Both self-sharpening and proportionate pattern mass-transfer zones can be formed depending on the shape of the surface-excess isotherm and the selectivity of adsorption. Analysis of column dynamics for liquid mixture adsorption can be carried out analogous to that for adsorption from gas mixtures, when a constant pattern mass-transfer zone is formed. The length of the mass-transfer zone and the composition-time column effluent profile can also be derived analytically for such a case. Experimental kinetics and column dynamics data for ad(de)sorption of ethanol-water mixtures on a large-pore activated carbon are analyzed using these models.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690380603
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  • 9
    Electronic Resource
    Electronic Resource
    Isotope exchange technique for measurement of gas adsorption equilibria and kinetics (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2456-2470 
    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 isotope exchange technique (IET) can be used to simultaneously measure multicomponent gas adsorption equilibria and self-diffusivities of the components in a single isothermal experiment without disturbing the overall adsorbed phase. An experimental protocol for the IET and corresponding data analysis procedures is described. Isotherms and self-diffusivities for adsorption of N2 as a pure gas were measured on commercial samples of a carbon molecular sieve and a 4-Å zeolite using IET, as well as those of O2 and N2 from their binary mixtures. The carbon molecular sieve did not exhibit thermo-dynamic selectivity for air separation, but had a kinetic selectivity of O2 over N2 Mass-transfer resistances for self-diffusion of N2 and O2 on the carbon molecular sieve were controlled by pore mouth restrictions in the carbon, but those for adsorption of N2 into the 4-Å zeolite by Fickian diffusion inside the adsorbent. A linear driving force model described the uptakes of N2 and O2 in the carbon molecular sieve. The Fickian diffusion model described the N2 uptake in the 4-Å zeolite. Mass-transfer coefficients for both O2 and N2 on the carbon molecular sieve increased linearly with increasing gas-phase partial pressure of these gases, and the pressure of O2 did not affect mass-transfer coefficients for N2. The self-diffusivity of N2 in the 4-Å zeolite decreased with increasing adsorbate loading.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431009
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  • 10
    Electronic Resource
    Electronic Resource
    Adsorption from binary immiscible liquid mixture (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1191-1194 
    Details
    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: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420434
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    Paper (German National Licenses)
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