The CH4
adsorption amount over the P-AC sample was very small in
the whole range of pressure, implying that P-AC was not an
excellent adsorbent for adsorbing CH4. It was reported that
the carbon precursors used to prepare activated carbons can
affect the adsorption capacities of the samples, and the CO2
and CH4 adsorption capacities over the activated carbons were
no more than 0.7, and 0.3 mmol/g, respectively, at 25 ◦C and
100 kPa [13].