All chemicals used were of analytical grade. Commercially
available AC (C. Gigantic Carbon Co., Ltd., Thailand) produced from
steam activation of palm shell was used as the adsorbent. MEA and
DEA of higher than 99% purity were obtained from Carlo Erba
(Italy). Properties of MEA and DEA are listed in Table 1. Methanol
(Carlo Erba) was used as the solvent in MEA and DEA solutions. The
CH4 and CO2 used to prepare the CH4/CO2 gas mixture for test
samples were of high purity grade (HP 99.995%). The helium (He)
used for volume measurements and the nitrogen (N2) used for
pretreatment of the adsorbent and regeneration of the exhausted
adsorbent were of ultra high purity grade (UHP 99.999%). Distilled
water was used throughout the study.