Research in the Inorganic Membrane group encompasses macro as well as micro scale phenomena in the field of:
- the development of new membrane materials,
- a better fundamental understanding of transport mechanisms,
- the design of membrane processes and membrane reactors.
1. Advanced Ceramics
In general, the preparation, processing, and microstructural characteristics of powders, ceramics, and coatings are studied. It implies sol-gel chemistry for modifying micro- and meso-porous ceramic membranes as well as development of new, dense mixed ion/electron conducting membranes.
2. Solid State Ionics
Within this research theme the ionic and electronic transport properties of solid oxides are studied, which includes interfacial and electrode reactions. The focus is towards improved understanding of the fundamentals of technological applications incorporating these oxides, such as dense ceramic membranes and solid oxide fuel cells (SOFC).
3. Porous Ceramic Membranes
Here the objectives are the development of micro- and meso-porous ceramic membranes and the study of molecular transport for use in energy-efficient gas separation, pervaporation, and nanofiltration processes.
Electron microscope picture of a porous membrane, showing supporting layers and a selective hybrid silica top layer (thickness: 0.1 μm; pore size: few Ångströms).
Image of the surface of a two-phase dense, oxygen-selective, ceramic membrane, made by SEM.
Hybrid silica membranes are of great interest for molecular separation owing to their outstanding hydrothermal stability. These membranes are made by solgel methods, using BTESE (1,2-bis(triethoxysilyl)ethane) as precursor. Detailed analysis on the sol-gel process showed that a more dense pore structure is obtained by limiting both the water and acid contents in the dipped sol, resulting in the highest H2/N2 and CO2/CH4 permselectivities found to date for hybrid silica membranes (ref: Hammad Qureshi, Hessel Castrcium et al.). In another study a simple method is developed to incorporate zirconia in the hybrid matrix (Zr-BTESE), which results in an increase in H2/CO2 permselectivity by a factor 4 (from 4 to 16) (ref: Marcel ten Hove et al.).
Better permselectivity by using less water and acid during solgel synthesis; Castricum et al.
Zr-doping in hybrid silica – Increase in (perm)selectivity; Ten Hove et al.
Separation of solvents by membranes is a potential key enabling technique for many chemical processes and advanced energy production technologies. State-of-the art polymeric or ceramic membranes do not always meet stability and/or selectivity demands at process-relevant conditions like separation/purification of harsh organic solvents and operations at high temperatures or pressures. In order to fulfill on these operational requirements, a concept is developed, based on mesoporous (pore size 5 nm) ceramic membranes, as a non-swelling and non-compactable rigid material, acting as a support, on which polymer materials are immobilized. PDMS-modified hydrophobic nanofiltration membranes are synthesized and fully characterized. These membranes remained hydrophobic and showed stable and high solvent fluxes even after exposure for more than 100 days in several solvents at room temperature and subsequently 4 days in isopropanol at 75 °C or 6 days in toluene at 90 °C, while the molecular weight cut-off remained constant (~ 500 Da). Studies on solvent/solute transport mechanisms are in progress.