Activated carbons textural optimization for gas storage processes

For decades a particular interest has been devoted to the enhancement of adsorption processes by means of activated carbons (AC) pore size tailoring. In the present study, an original textural modification route is presented and applied to a commercial AC. It is composed of cyclic treatments of mild-oxidation at 250 degrees C under air followed by a carbonization step under nitrogen. This technique provides series of homologous adsorbents of similar surface chemistry and gradual increase in mean pore size and microporous volume. Comparing the raw material and the modified adsorbent after 12 cycles, a ratio of about two is reached for these two parameters representative of their microtexture. The corresponding performances of the elaborated adsorbents are compared in the case of CO2 storage. According to the amount of CO2 cycled per unit of column volume, the optimal extend in textural modification is found to depend strongly on the temperature-pressure working ranges. At low temperature level as 273 K, the storage capacity is found to be enhanced for all considered loading pressure levels within the range of 1-3 MPa. At higher working temperature as 333 K, the enhancement is severely reduced but still observed for the highest loading pressure level and very first oxidative cycles. (c) 2007 Elsevier B.V. All rights reserved.