(719ad) Fate of Oxygen Atoms Present as CO Complexes on Activated Carbon Under Heat Treatment In Hydrogen Atmosphere

Activated carbon derived from phenolic resin is oxidized by either HNO3 or atmospheric air at several temperatures for varying oxidation times in order to introduce surface oxygen complexes on the carbon surfaces. The types and amounts of oxygen complexes are estimated by temperature programmed desorption (TPD). The temperature programmed reduction (TPR) is also performed in H2, the concentration of which is ranged from 1.95 to 100vol%. Three different gases of CO2, CO and H2O evolving from the carbons during TPD and TPR runs are analyzed by gas chromatograph. The amount of H2O desorbed in TPR is significantly larger by comparison to that in TPD, but an opposite result is found in CO. The quantities of H2O and CO are affected by the concentration of H2 during TPR, indicating that oxygen atoms in CO complexes are removed partially as H2O by H2 during TPR and the remainder of the CO complexes decomposes as CO without being affected by the presence of H2. No significant change is found in the amount of CO2 among TPD and TPR runs. The TPR runs on the various types of oxygen-containing carbons are performed systematically under a fixed concentration of H2 in order to investigate quantitatively how the CO complexes decompose as H2O and CO during TPR.