Methane adsorption storage using microporous carbons obtained from coconut shells

This paper presents an experimental and theoretical study of the adsorption equilibria of methane on activated carbon, focusing on the accurate determination of the absolute adsorbed mass from raw gravimetric measurements performed at high pressures (above 0.1 MPa). Two carbon samples were selected for these studies: a commercial sample (SRD-21) and a sample prepared in laboratory from coconut shells (CAQF-30). A gravimetric set up was used to measure the adsorption properties. Methane isotherms were obtained in the pressure range of 1 to 70 bar and under temperatures from 10 to 80 degrees C. Equilibrium experimental data were evaluated with the aid of three approaches labeled as D, DD and DDA, the latter being proposed for the first time in this paper. The DDA approach provided consistent and physically meaningful results for the adsorbed phase density. The adsorption isotherm that was obtained following the DDA approach matched those obtained following an approach published in the literature. The results indicate that the CAQF-30 sample, despite being prepared from carbonaceous wastes, presents competitive values for the methane adsorption parameters when compared to the commercial sample.