Adsorption Enthalpy Calculations of Hydrogen Adsorption at Ambient Temperature and Pressures Exceeding 300 bar

Abstract

Hydrogen adsorption isotherms were measured at ambient temperature to pressures exceeding 300 bar for three benchmark adsorbents: two metal-organic frameworks, Cu 3 (btc) 2 (btc = 1,3,5-benzenetricarboxylate) and Zn 4 O(btb) 2 (btb = 1,3,5-benzenetribenzoate), and the activated carbon MSC-30. The Dubinin-Astakhov model was applied to calculated absolute adsorption isotherms as a function of the fugacity to determine the adsorption enthalpy at ambient temperature. Comparisons of the calculated enthalpies and the surface excess concentration (excess adsorption per square meter of surface) show that Zn 4 O(btb) 2 has an adsorption enthalpy comparable to MSC-30, but that the spacing between ad-sorbed molecules is much larger.