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.
An example of grafting PDMS on an inorganic surface: Tanardi et al.
Stable permeability in PDMS-grafted ceramic membrane; Pinheiro et al.