Pore size and surface chemistry effects on the transport of hydrophobic and hydrophilic solvents through mesoporous γ-alumina and silica MCM-48

Abstract

The structural and solvent transport properties of supported mesoporous γ-alumina and MCM-type silica membranes are reported. Templated mesoporous silica layers and powders were characterized by XRD, permporometry, XPS and BET measurements. The results indicate that the γ-alumina membrane is ∼1 μm thick, while the silica membrane is ∼30 nm thick, has a pore size of 2.8–3.4 nm and possesses the MCM-48 structure. Pressure-driven solvent flow experiments on α-alumina supported γ-alumina and MCM-48 membranes indicate that the permeabilities of the mesoporous layers depend on the chemical nature of the solvents. The permeability of hexane and toluene through γ-alumina with 4.5–7.5 nm pores is lower than that of hydrophilic alcohols and water. The permeability of water and alcohols through MCM-48 appears to be affected by solvent–pore interactions on molecular scale. The MCM-48 layer has a higher permeability than γ-alumina, which can be attributed to its much smaller thickness.