Reduced pressure sublimation of amine compounds of activated carbons

Activated carbon is used in gas-mask canisters for filtering air to remove toxic vapours. For military use, the charcoal is impregnated with inorganic salts or organic compounds for improving the chemical activity of the charcoal with respect to toxic vapours having low boiling points and small molecular sizes, e.g. cyanogen chloride. One such compound, namely triethylenediamine (TEDA) has been added to charcoal by sublimation at atmospheric pressure. A more effective method of impregnating charcoal with TEDA utilizes reduced pressure 0.13 to 13 Pa, preferably 1.3 Pa as a driving force to facilitate vaporization of the TEDA by sublimation. The activated carbon to be impregnated is dried at 110 DEG C to 160 DEG C for three hours and transferred to a vacuum desiccator. The required amount of the amine, namely 1.57 to 12.57%, preferably 4.7% is placed in the container on top of the activated carbon and the container is evacuated to a pressure of about 1.3 Pa and heated at 40 DEG C for two to three days until the amine compound is no longer visible on the carbon. The resulting TEDA impregnated carbon provides improved protection against toxic gases compared to the precursor charcoal.