Patent ID: 7094935

Claim:
An adsorbent for purifying a perfluorocarbon, which is produced using a method comprising the following four steps: (1) washing an original coal with an acid and then with water; (2) deoxidizing and/or dehydrating the original coal obtained in the step (1) at a temperature of 50 to 250° C. in an inert gas stream; (3) re-carbonizing the original coal obtained in the step (2) at a temperature of from 500 to 700° C. in an inert gas stream; and (4) activating the original coal obtained in the step (3) at a temperature of 700 to 900° C. in a mixed gas stream containing an inert gas, carbon dioxide and water vapor, wherein the total content of alkali metals in the adsorbent is 1,000 ppm or less.