Hydrothermal Treatment as a Tool to Tailor the Mesoporous Structure of Sol-Gel Silica

This study presents a simple sol-gel synthesis of silica using Tetraethylorthosilicate, water, and three alcoholic solvents. The gelation was carried out in autoclave between temperatures from ambient to 180 °C. The FTIR analyses showed that the chemical bonds of the synthesized silicas do not depend on the autoclave temperature and solvent used. Then, for both ethanol and isopropanol solvents, it was found that the higher the gelation temperature, the larger the mean diameter and specific pore volume in the prepared samples. The same trend was observed for water vapor adsorption. Such behavior seems to result from a faster network gelation entrapping more residual molecules, which leads to a more porous adsorbent after their removal, despite a stronger structural densification probably occurring for higher hydrothermal temperatures. Besides, such a densification process decreasing the porosity proved to be more significant when using an alcoholic solvent with a higher boiling point.