Mikrostrukturuntersuchungen an porösen Feststoffen durch Physisorptionsmessungen

Studies of the microstructure of porous solids by physisorption measurements . The principal experimental methods for studying the microstructure of porous solids are based on physisorption measurements. The resulting sorption isotherms can yield data such as surface area and pore radius distribution, which are of great importance for development and characterization of porous catalysts. After a brief presentation of available measuring equipment, the main concern of this survey is the evaluation of sorption isotherms. In particular, methods for determining the micropore contribution to the total pore volume and the pore radius distribution in the micropore range are examined critically with regard to their reliability.     

Stromverteilung in porösen elektroden

In porous electrodes, the current density of the conversion of electronic current into ionic current is not everywhere uniform. The distribution of the current-density depends on the electronic and ionic conductivities and the polarization curve of the electrode material. If the polarization can be represented correctly by an ohmic resistance, then it is possible, in the case of simple geometrical systems, to set up a system of differential equations, the solution of which is the required local current distribution. In the case of plate-forming electrodes, we find the interference of two counteracting hyperbolic cosine functions. By two examples, the influence of the individual electrical data on current distribution and depth of penetration is shown.     

Zur moleküladsorption an porösen styrol-divinylbenzol-copolymeren,I

The study of the adsorption of p-nitrophenol on porous crosslinked styrene-divinylbenzene copolymers enables the calculation of the surface area and is in fairly good agreement with results, which have been obtained from the same adsorption materials using the adsorption of nitrogen. The calculations are based on BET-equation. A typical monomolecular adsorption isotherm is obtained by methylene blue adsorption. It can be shown that the surface area is not completely coated with a layer of molecules.     

Druckverlustberechnung an konzentrischen porösen Hohlzylinderfiltern anhand dimensionsanalytischer Folgerungen und experimenteller Daten

In practice many geometric shapes of filter mediums are possible which differ from the classical case cross‐flow filtration with hollow fiber membranes. In this paper the influence of the filter medium geometry on the filter medium pressure loss due to porous hollow cylindrical tube with inflow from outside was investigated. An increase in resistance of the filter medium as a function of layer thickness and average curvature was observed. Based on dimensional analyses the obtained data were placed in a meaningful context and an empirical model for the calculation of the pressure loss in curved filter mediums could be derived.     

Zur Adsorptionspolymerisation auf porösen Feststoffen. 1. Kinetische Untersuchungen der Adsorptionspolymerisation auf der Oberfläche von porösem Silicagel

The polymerization of different monomers adsorbed from the vapour-phase onto the internal surface of porous silica containing vinyl groups has been investigated. The macromolecules were covalently bound to the inorganic solid. Polymerization was initiated by radicals generated by thermal decomposition of adsorbed AIBN at 60°C. Adsorption and simultaneous polymerization has been measured by a sensitive spring balance. The rate of polymerization in the adsorbed state is given by the equation: A strict first-order reaction related to the adsorbed monomer concentration has been obtained in the multimolecular adsorption range, while a nearly second order reaction could be measured below the monolayer capacity of silica. A formal kinetic scheme of the elementary polymerization steps in the adsorbed state including the reactive centers of the solid surface is proposed to explain the experimental results. The thermal degradation and the structure of porous silica containing polystyrene has been described.