Stofftransport in mikro‐ und mesoporösen Materialien

Mass Transfer in Micro‐ and Mesoporous Materials Mass transfer in micro‐ and mesoporous materials is of crucial relevance for their practical application to separation and catalysis, since the mobility of adsorbed molecules ultimately limits the rate of the overall processes. Diffusion, i.e. the irregular thermal motion of the molecules, is the dominating process. Diffusion measurements are therefore indispensable for the evaluation of the quality parameters of porous materials. Being able to directly follow the diffusion path of the molecules, microscopic techniques hold a key position among the various methods of diffusion measurement. Besides their fundamentals, the contribution describes the application of these techniques to the investigation of structure‐mobility relations in zeolites and in mesoporous materials of type MCM‐41. As features of particular technological relevance, the phenomena of correlated diffusion anisotropy, of single‐file diffusion, and of molecular traffic control are discussed in detail.     

Keramische Membran zur Wasserabtrennung aus Lösungsmitteln

Novel hydrophilic SiO_x modified alumina membranes with high separation factors and flux rates have been prepared for the separation of water from organic solvents. The membranes are prepared by the deposition of SiO_x networks inside the γ‐Al₂O₃ layer of a commercial ultrafiltration membrane by hydrolysis of tetraethylorthosilicate in autoclaves at 250°C. The transport resistance of the individual membrane layers to the permeation flux are described by a model. The membranes are stable towards solvents up to at least 150°C. Pervaporation studies show that water can be separated from solvents like acetonitrile, tetrahydrofuran, 2‐isopropanol, ethanol, dimethylsulfoxide, dimethylformamide, phenol. The separation performance of the membranes allows their use in technical separation processes, especially for the remove of water.     

Membranen für Polymerelektrolyt‐Brennstoffzellen

Membranes for Polymer Electrolyte Fuel Cells The polymer electrolyte membrane is the heart of hydrogen fuelled Polymer Electrolyte Fuel Cells (PEFC) and methanol fuelled Direct Methanol Fuel Cells (DMFC). Membranes of sulfonated fluoropolymers are already commercially available. Important goals for research and development are for PEFCs an increased operating temperature without the need for additional humidification and for DMFC the reduction of methanol transport through the membrane. The use of non‐fluorinated polymers aims at a reduction in membrane cost and environmental hazards. Membranes already in industrial product development are considered as well as novel membrane concepts in fundamental research.     

Protonenleitende Komposit‐Membranen für zukunftsorientierte Anwendungen in Brennstoffzellen,Entsalzungsanlagen und in der Photokatalyse

Inorganic filler materials are often incorporated into polymer membranes to improve their mechanical, thermal and chemical stabilities. In case of proton‐conducting polymers, however, it is necessary to support or at least not to disturb the proton‐conducting matrix. By suitable combination of polymer and filler, effective and highly conductive composite membranes can be prepared. This article gives an overview of the possible applications of a special kind of such proton‐conducting composite membranes containing functionalized SiO₂ particles with ordered mesoporosity in fuel cell, in desalination and in photocatalysis.     

Keramische Membranen: Materialien – Bauteile – potenzielle Anwendungen

Ceramic membranes can be divided into dense and porous membranes. The materials, microstructure, and manufacturing methods are described and insights into current research topics are given. By adapting the material properties and tailoring microstructures, membranes and components suitable for a variety of processes can be developed. In applications, a distinction can be made between pure gas separation and membrane reactors. In the latter ones, in addition to gas separation, a chemical reaction takes place on one or both sides of the membrane. Membrane reactors can be used to produce basic chemicals or synthetic fuels. The supply of gases can be of interest for power plants, cement, steel or glassworks as well as for the medical sector or for mobile applications.