Enhancement of Hydrothermal Stability and Hydrophobicity of a Silica MCM-48 Membrane by Silylation

Abstract

An MCM-48 membrane was prepared on a porous α-alumina support by hydrothermal synthesis. The silylation with trimethylsilane and triethylsilane was used to enhance hydrothermal stability and hydrophobicity of the MCM-48 membrane. The studies of X-ray diffraction, Fourier transform infrared (FTIR), nitrogen adsorption, and water adsorption were carried out using an MCM-48 powder to characterize the pore surface of MCM-48. The FTIR study indicates that the silyl group was substituted for the Si−OH group on the pore surface of MCM-48. The pore sizes of the nonsilylated and the silylated MCM-48 were 2.4 (nonsilylated), 1.9 (trimethylsilylated), and 1.8 nm (triethylsilylated). The water adsorption study showed that the pore surface of MCM-48 significantly changed to hydrophobic by silylation. The nonsilylated and the trimethylsilylated MCM-48 membranes were used for the separation of an ethanol/water mixture. The separation factor was 16 through the silylated membrane, although that of the nonsilylated membran...