Extraction of Template Agents from Porous Silica Using Supercritical Carbon Dioxide-Entrainer Method

Abstract

Supercritical fluid extraction of template agents, CTAH (Cetylrimethylammonium hydroxide) and EPE (EO₂₀–PO₇₀–EO₂₀) from mesoporous silica was carried out at 80°C, 8 to 14 MPa and extraction time of 1 to 7 h. The time evolution of templates showed that CTAH was removed after EPE. Among the three alcohols, including methanol, ethanol and 1-propanol as entrainers, methanol was the most efficient solvent that gave 95% recovery of CTAH. This seems to be caused by molecular size and polarity of entrainer. Supercritical carbon dioxide-entrainer method showed high recovery of template agents compared to organic solvent methods. Pore size of silica affected pressure dependence of template recovery, which indicated differences in interaction between pore wall and template. Optimization of extraction condition was achieved by selecting suitable pressure and entrainer for providing better balance of entrainer penetration and extraction power.