Effects of Particle-Size Combination on the Pore Structure, Compressive Strength and Methane Adsorption of Activated Carbon Monoliths

Activated carbon monoliths require both methane adsorption capacity and mechanical strength for gas storage. In this study, monoliths were prepared from fine, medium and coarse activated carbon particles to examine the effect of particle-size combination on these properties. Single fractions and binary mixtures at a volume ratio of 3:7 were molded under the same conditions. The pore structure, density and compressive strength were analyzed and methane adsorption was evaluated. The coarse-particle monolith had the largest micropore volume of 1.03 cm3/g and the highest methane uptake per unit mass of 3.735 mmol/g at an absolute pressure of 10 bar. The fine–coarse monolith showed a lower uptake of 3.590 mmol/g but a higher density of 0.480 g/cm3. Its calculated uptake per unit volume was the highest at 1.72 mmol/cm3, slightly above the 1.70 mmol/cm3 of the coarse-particle monolith. The higher density therefore compensated for the lower uptake per unit mass. The medium–coarse monolith showed the highest compressive strength of 7.83 MPa. These results indicate that the particle-size combination should be selected by considering monolith density and compressive strength together with methane uptake per unit mass.