Effects of polar modifiers on supercritical extraction efficiency for organic template removal from mesoporous MCM-41 materials

Abstract

The application of polar modifiers usually can make supercritical CO2 extraction more attractive in various potential applications. In this work, several polar modifiers have been examined for the extraction of the template cetyltrimethylammonium bromide (CTMABr) from newly synthesized MCM-41 mesoporous materials, and the modifier content, modifier identity and the sample matrix on supercritical CO2 extraction efficiency are then evaluated. The results show that the polar modifiers employed have strong influences on the template extraction efficiencies and this could be interpreted rather well in terms of solubility parameter and polarity of the modifiers. Methanol, water and acidic methanol are found to result in very high efficiencies of more than 85% for the pure siliceous samples while relatively good extraction efficiencies of 60–80% for aluminum incorporated samples, and the difference is due to that the organic template could form stronger interactions with the Al species than the silanol groups. Nitrogen adsorption/desorption and X-ray diffraction results confirmed that the polar modifiers have strong influences on the final mesoporous structure of the MCM-41 materials and with methanol modified supercritical CO2 extraction the resultant materials possess well-ordered mesostructure and much better structural properties like higher pore volume and specific surface area.