Effects of pore structure of granular activated carbons on CH4 enrichment from CH4/N2 by vacuum pressure swing adsorption

• GACs with similar surface properties but different pore structures were prepared.
• The effective pore size for the CH4 enrichment is from 5.0 Å to 13 Å, with the optimum from 5.0 Å to 8.0 Å.
• Adsorption affinity for CH4 of effective micropores is demonstrated by adsorption isotherms.
• Using the best as-prepared GAC, the CH4 purity up to 66.6% from CH4 (30%)/N2(70%) by VPSA.

A series of granular activated carbons (GACs) of similar surface properties but different pore structures were prepared, and used to enrich methane from methane and nitrogen mixture (CH4/N2) by vacuum pressure swing adsorption (VPSA) method. The adsorption isotherms of CH4 and N2 illustrated that the adsorption affinity of GAC for CH4 over N2 is dependent on the pore structure. It was found that larger surface areas are favorable to CH4 enrichment. The effective pore size for the CH4 enrichment is from 5.0 Å to 13 Å, with the optimum effect occurring in the range from 5.0 Å to 8.0 Å. By a single-bed VPSA measurement, the CH4 has a purity up to 66.6 vol%, enriched from CH4 (30 vol%)/N2 (70 vol%) mixture by using optimum pore-size GAC.

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