Determination of Diffusion Coefficients from Sorption Kinetic Measurements Considering the Influence of Nonideal Gas Expansion

Schumacher, Richard; Ehrhardt, K.; Karge, Hellmut G.

doi:10.1021/la9816454

Cited by 9 publications

(3 citation statements)

References 14 publications

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“…The heats of adsorption Δ H ads were calculated from this data as a function of sorbate concentration according to The curves of sorption kinetics were evaluated by fitting the analytical solution of Fick's second law under appropriate boundary conditions to the experimental data. The valve effect was taken into account as described in ref to compensate for the finite rate of gas expansion in a real experiment. The Fickian diffusivities determined therefrom were corrected by Darken's correction…”

Section: Methodsmentioning

confidence: 99%

Thermodynamics and Kinetics of Adsorption of Selected Monoalkylbenzenes in H-ZSM-5

Schumacher

Karge

1999

J. Phys. Chem. B

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In this study, we present the first systematic investigation of the adsorption of n-propylbenzene, isopropylbenzene, and n-butylbenzene in H-ZSM-5. Both the sorption isotherms and the rate of sorption uptake were investigated at temperatures between 315 and 425 K. The adsorption isotherms are of type I and are reasonably well described by the Langmuir−Freundlich model. It is shown that the heat of adsorption of the longer sorbate molecules depends significantly on the concentration, thus indicating an increased influence of sorbate-sorbate interaction. The uptake rates are determined by Fickian diffusion. The activation energies for the diffusion process are identical for all systems (32−36 kJ/mol). The diffusivities are also in the same order of magnitude decreasing noticeably for sorbates with longer or more complex substituents. A tentative explanation based on a simple jump-rate model for intracrystalline diffusion is given.

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Section: Methodsmentioning

confidence: 99%

Thermodynamics and Kinetics of Adsorption of Selected Monoalkylbenzenes in H-ZSM-5

Schumacher

Karge

1999

J. Phys. Chem. B

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“…The experiment consists in injecting a very small amount of CO 2 (0.5 cc STP) in the uptake cell at constant temperature (10 °C) while the pressure is monitored. The choice of a lower temperature for the volumetric experiments relative to the ZLC measurements is mainly dictated by the fact that the piezometric method presents severe limitations if used to measure the adsorption kinetics of fast systems or strongly adsorbed species (Brandani, 1998;Schumacher et al, 1999). For the case under investigation, a lower temperature (i.e.…”

Section: Volumetric Experimentsmentioning

confidence: 99%

Diffusion mechanism of CO2 in 13X zeolite beads

Mangano

Friedrich

et al. 2013

Adsorption

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A systematic study of the diffusion mechanism of CO 2 in commercial 13X zeolite beads is presented. In order to gain a complete understanding of the diffusion process of CO 2 , kinetic measurements with a Zero Length Column (ZLC) system and a volumetric apparatus have been carried out. The ZLC experiments were carried out on a single bead of zeolite 13X at 38 °C at a partial pressure of CO 2 of 0.1 bar, conditions representative of post-combustion capture. Experiments with different carrier gases clearly show that the diffusion process is controlled by the transport inside the macropores. Volumetric measurements using a Quantachrome Autosorb system were carried out at different concentrations. These experiments are without a carrier gas and the low pressure measurements show clearly Knudsen diffusion control in both the uptake cell and the bead macropores. At increasing CO 2 concentrations the transport mechanism shifts from Knudsen diffusion in the macropores to a completely heat limited process. Both sets of experiments are consistent with independent measurements of bead void fraction and tortuosity and confirm that under the range of conditions that are typical of a carbon capture process the system is controlled by macropore diffusion mechanisms.

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“…[18,19,34,61] Mastering multiple length scales in catalyst synthesis is even more poorly developed with zeolites being a prominent exception, at least in the mesoscopic size regime. [63][64][65] The title question may be answered if the term "nanocatalysis" is understood as describing a vision where one might consider a catalyst to be a hierarchical system of basic structural units (active sites) with defined assembling strategies for multiple length scales. The resulting functional materials are dynamic in nature, as a result of catalystreactant and catalyst-reactor interactions.…”

Section: Nanocatalysis: a Visionmentioning

confidence: 99%

Nanocatalysis: Mature Science Revisited or Something Really New?

2004

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"Nanomania" has reached the area of heterogeneous catalysis. Nanosized catalyst constituents are important for functions that require structural control over several scales of dimension. Nanocatalysis may be understood as a redefinition of catalyst synthesis: multidimensional structural control is exerted by considering catalysts as inorganic polymers rather than as close-packed crystals. Primary, secondary, and tertiary structural hierarchies translate into molecular building blocks and linkers, the defect structure of crystals, and particle morphology. High-throughput techniques and in situ synthetic analysis are the tools required to arrive at better defined catalytic materials that can fulfil the high expectations created by the incorporation of catalysts into the "nano" research field.

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Determination of Diffusion Coefficients from Sorption Kinetic Measurements Considering the Influence of Nonideal Gas Expansion

Cited by 9 publications

References 14 publications

Thermodynamics and Kinetics of Adsorption of Selected Monoalkylbenzenes in H-ZSM-5

Thermodynamics and Kinetics of Adsorption of Selected Monoalkylbenzenes in H-ZSM-5

Diffusion mechanism of CO2 in 13X zeolite beads

Nanocatalysis: Mature Science Revisited or Something Really New?

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