title: Anomalous isosteric enthalpy of adsorption of methane on zeolite-templated carbon.
abstract: A thermodynamic study of the enthalpy of adsorption of methane on high surface area carbonaceous materials was carried out from 238 to 526 K. The absolute quantity of adsorbed methane as a function of equilibrium pressure was determined by fitting isotherms to a generalized Langmuir-type equation. Adsorption of methane on zeolite-templated carbon, an extremely high surface area material with a periodic arrangement of narrow micropores, shows an increase in isosteric enthalpy with methane occupancy; i.e., binding energies are greater as adsorption quantity increases. The heat of adsorption rises from 14 to 15 kJ/mol at near-ambient temperature and then falls to lower values at very high loading (above a relative site occupancy of 0.7), indicating that methane/methane interactions within the adsorption layer become significant. The effect seems to be enhanced by a narrow pore-size distribution centered at 1.2 nm, approximately the width of two monolayers of methane, and reversible methane delivery increases by up to 20% over MSC-30 at temperatures and pressures near ambient.
authors.affiliation: W. M. Keck Laboratory, California Institute of Technology, 138-78, Pasadena, California 91125, USA. nstadie@caltech.edu
authors.forename: Nicholas P
authors.initials: NP
authors.lastname: Stadie
authors.forename: Maxwell
authors.initials: M
authors.lastname: Murialdo
authors.forename: Channing C
authors.initials: CC
authors.lastname: Ahn
authors.forename: Brent
authors.initials: B
authors.lastname: Fultz
mesh_terms: D000327:Adsorption; D002244:Carbon / Q000737:chemistry*; D008697:Methane / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties; D013816:Thermodynamics; D017641:Zeolites / Q000737:chemistry*
chemical_list: D017641:Zeolites; D002244:Carbon; D008697:Methane