Preparation and characterization of hydrophobic microporous silica membranes modified by fluorocarbon groups

Silica membranes were modified by fluorocarbon groups through an acid-catalyzed co-hydrolysis and a condensation reaction of tetraethyl orthosilicate (TEOS) and trifluoropropyltriethoxysilane (TFPTES). The cross-sectional micrograph, pore structure and hydrophobic property of the modified silica membranes were characterized by SEM, nitrogen adsorption, FT-IR and contact angle methods. The results show that the hydrophobic property of the modified silica membranes has been gradually enhanced, whereas the pore structure almost remains unchanged with the increase of TFPTES content. When the molar ratio of TFPTES/TEOS was increased to 0.6, the modified silica membranes possessed a water contact angle of 111.6 degrees +/- 0.5 degrees and a desirable microporous structure, with a pore volume of 0.19 cm(3.)g(-1) and a pore size of 0.97 nm. The hydrogen transport in the modified silica membranes was subjected to a micropore diffusion mechanism, with a H-2 permeability of 1.18 x 10(-7) mol(.)m(-2.)Pa(-1.)s(-1) and a H-2/CO2 separation factor of 7.0.