GRANULAR AND PELLETIZED ACTIVATED CARBON BASED ON OLIVE STONES FOR METHANE STORAGE

The behavior of an olive stones based activated carbon as an adsorbent for pure methane was investigated at room temperature (298 K) under low pressure of about 10 bars. Two forms of activated carbons was obtained (granular and pelletized) by chemical activation using phosphoric acid. Methane storage was done using two different measure techniques (gravimetric and volumetric). For volumetric measures, a cyclic operation of 5 charge- discharge cycles was carried out using the two forms of adsorbent granular activated carbon CAGOC, and pelletized one CAGOC-Pas. Storage on CAGOC reaches 40 mg/g under 10 bars with a release of about 30 mg/g at atmospheric pressure. In the other hand, CAGOC-Pas without binder reaches huge amount of adsorbed methane of about 68 mg/g under 10 bars with a discharge of about 50 mg/g at atmospheric pressure. For gravimetric measures, under 50 bars a huge increase of adsorbed amount was seen from granular to pelletized activated carbon from 72 mg/g to 105 mg/g. The difference in adsorption capacities and behaviors in cyclic operation can be probably related to best textural properties and surface morphologies of CAGOC-Pas. Temperature- dependent methane isotherms show that the isosteric heat of adsorption reaches 20 kJ/mol for all the stages o loading methane.