Process for drying sol-gel derived porous bodies at elevated subcritical temperatures and pressures

A process for drying a wet, porous gel having a matrix that carries a liquid in its pores, comprising;

• placing the gel inside a sealable pressure chamber;
• sealing the pressure chamber;
• heating the sealed pressure chamber to a temperature below the critical temperature of the liquid, without introducing a separate fluid into the chamber, until substantially all of the liquid inside the pressure chamber and inside the pores of the gel matrix vaporizes, causing an increased pressure inside the pressure chamber that is above an ambient pressure but below the critical pressure of the liquid;
• releasing the vapor from the pressure chamber until the pressure inside the pressure chamber reaches the ambient pressure;
• purging the pressure chamber with an inert gas;
• cooling the pressure chamber until the gel reaches an ambient temperature;
• and
• removing the cooled gel from the pressure chamber.

A process for drying a wet, porous gel having a matrix that carries a liquid in its pores, comprising:

• placing the gel in a container containing a drying solvent that is substantially the same as the liquid in the pores;
• placing the container inside a sealable pressure chamber;
• sealing the pressure chamber;
• increasing the temperature inside the sealed pressure chamber at a rate of from about 2.degree. to about 10.degree. C. per hour to a temperature below the critical temperature of the liquid until substantially all of the liquid vaporizes, causing an increased pressure inside the pressure chamber that reaches a substantially constant level above an ambient pressure but below the critical pressure of the liquid;
• releasing the vapor from the pressure chamber while maintaining a constant temperature inside the pressure chamber until the pressure inside the pressure chamber reaches the ambient pressure;
• purging the pressure chamber with an inert gas for at least ten minutes;
• cooling the pressure chamber until the gel reaches an ambient temperature;
• and
• removing the cooled gel from the pressure chamber.