Deformation of Microporous Carbon Adsorbent Sorbonorit‑4\nduring Methane Adsorption

Abstract

The temperature- and methane adsorption-induced\ndeformations of\nmicroporous activated carbon Sorbonorit-4 were measured by in situ\ndilatometry over a wide range of temperatures and pressures. The thermal\nexpansion coefficient of Sorbonorit-4 in vacuum increased linearly\nwith temperature within a range of 293–573 K. Methane adsorption\nin Sorbonorit-4 induced its contraction at low pressures and temperatures\nor expansion at high temperatures throughout the entire pressure range.\nAn inversion of the temperature dependence of adsorption-induced strain\n(AIS) of Sorbonorit-4 was found. At low pressures and temperatures\nbelow 300 K, the AIS isotherm showed a contraction of Sorbonorit-4;\nits magnitude and corresponding pressure interval decreased with temperature.\nAt <i>T</i> > 300 K, the temperature rise was accompanied\nby an adsorption-induced expansion of Sorbonorit-4 up to 0.08% at\n393 K. At high pressures, the expansion decreased from 0.45 to 0.13%\nwhen the temperature increased from 213 to 393 K. The AIS of Sorbonorit-4\nand differential isosteric heat of adsorption presented as functions\nof methane uptake changed within the same intervals of adsorption\nvalues, reflecting variations in the state of adsorbed molecules determined\nby contributions from the adsorbate–adsorbent and adsorbate–adsorbate\ninteractions. The obtained results are essential for practical use\nof carbon adsorbents for natural gas storage.