High quality mesoporous materials prepared by supercritical fluid extraction: effect of curing treatment on their structural stability

Mesoporous molecular sieves like SBA-1, SBA-3, MCM-41 and MCM-48 are generally synthesized by using a quaternary ammonium surfactant as a structure-directing agent to form a porous silica framework. The used templating agent is conventionally removed for producing mesopores by calcination at high temperature. In this study, supercritical fluid extraction (SFE) has been employed to remove organic templates from these materials. We found that more than 80% of the templating agent can be successfully removed by using this technique. Among these materials, SBA-3 was observed to experience the collapse of mesoporous structures upon the SFE process. Thus, we have proposed pre-SFE thermal aging as a curing treatment method and found that it has significantly improved the mesoporous structural stability of SBA-3. In the meantime, this curing method has lead to these SFE-processed materials with better ordered mesoporous structures, such as SBA-3 having specific surface area as large as 1670 m2/g.