Sorption Kinetics of p-Ethyltoluene in NaH-ZSM-5 Crystals-Simultaneous Effect of Intracrystalline Diffusion and a Mass Transport Resistance within the Crystal Surface

1994 ◽  
Vol 59 (7) ◽  
pp. 1525-1535 ◽  
Author(s):  
André Micke ◽  
Peter Struve ◽  
Martin Bülow ◽  
Milan Kočiřík ◽  
Arlette Zikánová
Keyword(s):  
Crystal Surface ◽  
Sorption Kinetics ◽  
Fickian Diffusion ◽  
Variable Pressure ◽  
Surface Barrier ◽  
Model Parameters ◽  
Equilibrium Data ◽  
Uptake Data ◽  
Kinetics Of ◽  
Rate Mechanism

Adsorption equilibrium and sorption uptake data have been measured for the system p-ethyltoluene/NaH-ZSM-5 zeolite under constant volume/variable pressure condition at elevated ambient temperature of 343 K. The equilibrium data are described by a superposition of two Langmuir isotherms. The uptake curves observed in the present paper revealed devations from the second Fick law behaviour. The experimental uptake curves are compatible with rate mechanism involving Fickian diffusion superimposed by a surface barrier. The evaluation of the model parameters was carried out by simulation of the kinetic curves that include both the interactions of the system with the apparatus and the intrinsic sorption kinetics. The dependence of the fitted model parameters on sorbent amount and pressure, respectively, is consistent with Langmuir sorption kinetics at crystal surface on one side and with the concept of molecule jumps on a system of fixed positions in the crystal bulk on the other.

Sorption and Transport of Species in Silicalite Study of Binary Systems Containing Iodine

1998 ◽  
Vol 63 (3) ◽  
pp. 321-337 ◽  
Author(s):  
Vladimír Masařík ◽  
Pavel Novák ◽  
Arlette Zikánová ◽  
Jan Kornatowski ◽  
Jaroslav Maixner ◽  
...  
Keyword(s):  
Binary Systems ◽  
Crystal Morphology ◽  
Crystal Surface ◽  
Vapour Phase ◽  
Sorption Kinetics ◽  
Diffusion Experiment ◽  
Initial Stage ◽  
Pore Mouth ◽  
Kinetics Of ◽  
Counter Diffusion

Sorption of iodine from both the vapour phase and iodine solutions in organic solvents on large Silicalite-1 crystals was investigated. The single component sorption of iodine and sorption from binary mixtures under co-diffusion conditions led to a uniform colouring of the crystals. Under counter-diffusion conditions with crystals saturated initially with vapour of a selected solvent, the sorption kinetics of iodine was 2 or 3 orders of magnitude slower as compared with the corresponding co-diffusion experiment. Colouring of crystals was always, at least in its initial stage, non-uniform with visualized pyramids at crystal basal planes. This finding together with the nature of outer and inner crystal morphology suggests that our Silicalite-1 crystals are 90°-intergrowths which have only pore mouth openings of sinusoidal channels in the crystal surface. The process of crystal colouring under counter-diffusion conditions seems to proceed via diffusion along the boundaries of crystal sections.

Equilibrium and Kinetics of Methane and Ethane Adsorption in Carbon Molecular Sieve

2016 ◽  
Vol 14 (4) ◽  
pp. 887-898 ◽  
Author(s):  
Babak Shirani ◽  
Mladen Eic
Keyword(s):  
Molecular Sieve ◽  
Surface Barrier ◽  
Diffusion Resistance ◽  
Carbon Molecular Sieve ◽  
Transfer Rates ◽  
Equilibrium And Kinetics ◽  
Different Temperatures ◽  
Uptake Data ◽  
Barrier Resistance ◽  
Kinetics Of

Abstract The comprehensive study involving uptake and kinetics behaviour of methane and ethane was carried out on a commercial carbon molecular sieve. The gravimetric technique was applied to measure the adsorption isotherms at different temperatures. The kinetic behaviours of methane and ethane were investigated by extracting the uptake data from isotherms at different pressure steps. Considering CMS as a homogenous microporous adsorbent, only two main resistances: surface barrier (at the pore mouth) and diffusion resistance (inside the pores) were considered in analysing the kinetic data. The kinetic analysis showed dominance of surface barrier resistance at all temperatures and pressures investigated in this study. Modified Darken equation was used to calculate the sorbates’ activation energies for adsorption in CMS pores. Compared to Darken equation, the modified Darken model predicted the concentration dependency of the surface rate constants more accurately, especially at higher sorbates’ concentrations. The activation energy of methane and ethane was greater than the heat of adsorption demonstrating a large impedance and barrier at the pore surface to the methane and ethane molecules. The kinetic selectivity of methane over ethane was calculated from the combined surface barrier/diffusion model parametric analysis. The results generally showed a greater selectivity to methane over ethane, i. e., the higher mass transfer rates.

Modeling of sorption kinetics of U(VI) micro-quantities nanostructured materials with anatase mesoporous structures

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Veniamin Zheleznov ◽  
Aleksey Golikov ◽  
Tatiana Sokolnitskaya ◽  
Sergey Ivannikov
Keyword(s):  
Nanostructured Materials ◽  
Sorption Kinetics ◽  
Uranyl Ion ◽  
Competitive Sorption ◽  
Hydroxyl Groups ◽  
Complex Ions ◽  
The Stability ◽  
Kinetics Of ◽  
Mesoporous Structures ◽  
Ionic Forms

Abstract The sorption kinetics of uranyl ions micro-quantities from fluoride solutions by nanostructured materials with anatase mesoporous structures has been studied. Using the model of competitive sorption of ions and positively charged complexes of uranyl ion on deprotonated hydroxyl groups of an anatase, kinetic curves of changes in the ratio of ionic forms of uranium in solution were calculated. Modeling was carried out under the assumption of a two-stage mechanism of uranium complex ions sorption. The modeling considered the influence of the uranyl ion carbonate complexes formation. The shift in equilibrium among ionic forms of uranyl correlates with the stability of the complexes in solution.

Sorption Kinetics of High Pressure Gases in Polymeric Tubing Materials

2006 ◽  
Author(s):  
P. Jaeger ◽  
S. Buchner ◽  
R. Eggers
Keyword(s):  
Diffusion Coefficients ◽  
Gas Permeability ◽  
Gravimetric Method ◽  
Sorption Kinetics ◽  
Operating Pressure ◽  
Gas Solubility ◽  
Atmospheric Conditions ◽  
High Solubility ◽  
Industrial Practice ◽  
Kinetics Of

A gravimetric method was applied to determine the sorption kinetics of gases into polymers. Diffusivity as well as sorption capacity are determined directly. Data of gas permeability that are required for calculating leakage rates in polymeric flexile gas and oil ducts may be retrieved by multiplying the obtained diffusion coefficients and the gas solubility. In general carbon dioxide enters polymers to the highest extent. In industrial practice, the high solubility of CO2 e.g. may lead to explosive decompression of sealings once the operating pressure is reduced to atmospheric conditions. Diffusion coefficients are presented in the range of 75 to 130°C at 2 to 30 MPa.

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