Thermodynamics of methane adsorption on carbon adsorbent prepared from mineral coalстатьяИсследовательская статья
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Дата последнего поиска статьи во внешних источниках: 23 сентября 2021 г.
Аннотация:Methane adsorption on a recuperated activated carbon, AR-V, was studied over the temperature range of 213–393 K andat pressures up to 10 MPa from the perspective of its potential application for adsorption-based storage and separationtechnologies. The porous structure, phase and chemical compositions of AR-V were examined by nitrogen adsorption at77 K, x-ray diffraction, and scanning electron microscopy. The amount of adsorbed methane increased with pressure up to6.3 mmol/g at 243 K and fell dramatically to ~ 1 mmol/g with a temperature rise to 393 K. The molar differential isostericheat of methane adsorption on AR-V was evaluated from the linear isosteres within the studied P,T-range; the effects fromthe non-ideality of a gaseous phase and the AR-V non-inertness were considered. The maximal summarized contributionfrom the AR-V thermal expansion and directly measured adsorption-induced deformation to the molar differential isostericheat of methane adsorption turned out to be less than that from the gas compressibility. The initial drastic changes in thethermodynamic state functions of the adsorption system were attributed to the binding methane molecules with non-uniformlydistributed high-energy adsorption sites. When methane molecules occupied all high-energy adsorption sites, the subsequentvariations in the thermodynamic functions were governed by the intensifying attractive forces between methane moleculesupon methane adsorption resulting in the formation of adsorption clusters. The temperature dependence of the isosteric heatcapacity of the methane/AR-V system varied during adsorption; its value exceeded 2–3 times the isochoric heat capacity ofthe equilibrium methane gaseous phase.