Influence of sol–gel process parameters on the micro-structure and performance of hybrid silica membranes

• A single-step sol synthesis route for hybrid silica is described.
• Homogeneous hybrid separation layer is obtained by a single dipping/calcining step.
• Sol viscosity and concentration determine membrane thickness and gas permselectivity.
• A pore size ranging from 0.3 to 0.54 nm is deduced from single-gas permeation data.

A facile, versatile and reproducible sol–gel process to make microporous organosilica membranes by using 1,2-bis (triethoxysilyl) ethane (BTESE) as a precursor is reported. The influence of process parameters on sol particle size and rheology of BETSE-derived sols was investigated to produce defect-free composite membranes by a single dipping procedure and subsequent calcination. The microporous structure of a BTESE layer on mesoporous alumina supports enabled selective molecular sieving of gas molecules. Single gas permeation (SGP) experiments, performed at 200 °C, showed that a H2/CH4 permselectivity of 24 was reproducibly achieved. No SF6 gas permeance through these membranes proof the presence of a defect-free microstructure. SEM cross-section analysis showed a hybrid selective layer with a thickness dependent on the sol precursor concentration.