Preparation and characterization of non-ionic block co-polymer templated mesoporous silica membranes

We report on the preparation and characterization of mesoporous silica membranes via micellar templating using the non-ionic ethylene oxide–propylene oxide–ethylene oxide tri-block copolymer surfactant, Pluronic P123, as a template under various template/silica volume percentages (VTS%). The silica membranes were prepared by dip coating silica sols onto porous α-alumina supports followed by calcination to remove the template. The membranes were characterized by single gas permeation and permporometry measurements. Using a VTS% of 33 we found that silica membranes comprised of three dip/fire cycles resulted in highly reproducible continuous membranes with minimal defects. Helium and nitrogen permeance values were of the order of 10−6 mol m−2 s−1 Pa−1. The pore size distribution, determined from permporometry measurements, indicated a dominant peak at 5 nm diameter and approximately 10% microporosity. In addition, there was 8–10% permeance through pores with diameters between 15 and 40 nm. At higher VTS% (47.5 and 65) the silica membranes had considerable bypass flow. The pore size distribution (PSD) of the membrane via permporometry indicated a shift to smaller values for the membrane when compared to the PSD of the powder from the calcined dipping sol, determined by nitrogen adsorption/desorption.