Supercritical Fluid Extraction of a Nonionic Surfactant Template from SBA-15 Materials and Consequences on the Porous Structure

Abstract

SBA-15 mesoporous materials were synthesized using the method reported by Zhao et al. Surfactant was removed from as-made materials by means of different techniques: thermal treatment under air atmosphere, solvent washing at different temperatures, and supercritical CO 2 extraction in the presence and absence of cosolvents. The structure of resulting materials was characterized using conventional techniques: nitrogen and argon adsorption measurements, powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), infrared spectroscopy (FT-IR), and 29 Si MAS NMR. The efficiency of surfactant removal using CO 2 under supercritical conditions is similar to that obtained by means of solvent washing under reflux but shows some improvements in the presence of cosolvents. Mesoscopic properties of mild-temperature solvent extracted SBA-15 materials depend on the efficiency of the surfactant removal and the use of supercritical CO 2 as solvent. Likewise, the size and volume of the complementary microporosity detected in the treated materials is closely related to the strategy of removal of hydrophilic poly(ethyleneoxide) chains of the triblock copolymer template occluded within the siliceous walls of the SBA-15 mesophase during the synthesis.