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Měření vnitřní difuze pomocí kapalinové chromatografie
Soukup, Karel ; Schneider, Petr ; Šolcová, Olga
Liquid chromatography setup was used in liquid diffusion studies. The Kubin-Kucera model was employed for mathematical description of processes inside the chromatographic column. Effective diffusivities were evaluated by time-domain fitting chromatographic response peaks of columns packed with tested porous particles. Axial dispersion coefficients were determined independently by analysis of response peaks of columns packed with nonporous pellets; this improved significantly the confidence of effective diffusion coefficients. An attempt was made to exclude the end effects of chromatographic columns by analyzing response peaks of pairs of columns differing by lengths.
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Standardní adsorpční isotermy argonu a dusíku pro Al2O3, TiO2, MgO a CPG
Matějová, Lenka ; Schneider, Petr ; Šnajdaufová, Hana ; Šolcová, Olga
The standard (master) isotherms describe relation between thickness, t, of adsorbed film and relative pressure, x (x = p/po is the adsorptive pressure, p, relative to adsorptive vapor pressure po, at measurement temperature,).They appear during the assessment of the core size, rk(x) (as determined by the Kelvin equation) in a pore just filled/emptied by/from capillary condensate, r(x) (r(x) = rk(x) +t(x)) and during the evaluation of adsorbed amount in pores free of capillary condensate. Such isotherms were experimentally determined for Ar and N2 on Al2O3, TiO2, MgO and Controlled Porous Glass.
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Podrobné materiálové charakteristiky z transportních procesů a texturní analýzy
Soukup, Karel ; Šolcová, Olga ; Schneider, Petr
The structure of porous solids is traditionally characterized by mercury porosimetry or physical adsorption of inert gases. The transport characteristics can be advantageously determined by evaluation of simple transport processes (e.g. multicomponent gas diffusion or permeation). Transport characteristics and textural properties of a set of porous catalyst pellets with wide range of mean pore radii (from 30 up to 3000 nm) were determined. by evaluated of multicomponent counter-current gas diffusion and permeation measurements. For gas diffusion the results from the Wicke-Kallenbach and Graham cell were compared.
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Transport Parameters and Textural Properties of Porous Solids
Soukup, Karel ; Šolcová, Olga ; Schneider, Petr
Based on a study of a set of porous materials with wide range of mean pore radii (from 50 to 3000 nm) and mono- or bidisperse pore structure, transport characteristics and textural properties are compared. Structure characteristics relevant to transport processes were evaluated from multicomponent gas diffusion and gas permeation measurements. For data analysis the Mean Transport Pore Model (MTPM) based on Maxwell - Stefan diffusion equation and Weber permeation law was used. Two standard methods - physical adsorption of nitrogen and mercury porosimetry (ASAP2010M and AutoPore 9200, Micromeritics, USA) were used for determination of textural properties. Results from liquid expulsion permporometry that correspond to situation in industrial processes were also taken into account.
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Efektivní difuzivity a transportní charakteristiky monolitických automobilových konvertorů s nanesenou vrstvou katalyzátoru
Starý, T. ; Šolcová, Olga ; Schneider, Petr ; Marek, M. ; Schejbal, M.
The effective diffusivity in the pores of catalytic monolith was studied in single pellet-string columns by chromatographic technique. The column was packed with small monolith particles. Dispersion due to extra column effects was eliminated via convolution of responses for two column lenghts. The measurements were done for both cordierite support with alumina based washcoat. The effective diffusion coefficients for two tracer-carrier pairs were evaluated by fitting column response (chromatographic) peaks in time domain. Mean transport parameters were evaluated for both types of porous particles. Obtained mean transport pore radii are in reasonable agreement with pore size distribution from mercury porosimetry.
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Effective Transport Properties of Reconstructed Porous Catalysts
Salejová, G. ; Kosek, J. ; Šolcová, Olga ; Schneider, Petr
The structure of porous catalysts is traditionally characterized by textural analysis, such as mercury porosimetry and BET sorption isotherm. Moreover, the effective transport properties of porous catalysts could be measured in the Graham diffusion cell, in the permeation cell, etc. In this contribution the electron microscopy images of porous catalysts are systematically analyzed, the spatially 3D porous media are reconstructed and their effective transport properties evaluated and critically compared with experimental values of effective transport parameters.
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