Physical characterization of microporous materials using various adsorbates. Correlation between their micropore volume and their capacity to adsorb H2 and CO2

• N2, Ar, and H2 adsorption on three different microporous materials.
• H2 showed better micropore distribution than other adsorbates.
• High pressure H2 and CO2 adsorption.
• Isosteric heats of adsorption calculated.

Microporous solids are characterized by a remarkable textural property that makes them privileged adsorbents among a full range of solids. The small pores called micropores contained in these solids are responsible for their high surface area and large total pore volume. They are capable of adsorbing large amounts of gas at moderate temperatures and pressures. Because of this property their applications in the industry are numerous, including their use for energy sources capable of adsorbing and easily desorbing H2. They can be used as CO2 adsorbents to reduce environmental pollution; they can also be used as industrial molecular sieves for gas enrichment, etc. Therefore, the focus of this work is to select three very different microporous materials and determine their textural properties, including surface area and pore volume, through the classical physisorption technique using N2 at 77.2 K, Argon at 87 K and H2 at 30 K. H2 at 30 K is used as an adsorbate to elucidate the ultra-microporosity of the solids, a property hidden from other adsorbates with higher molecular size. Various adsorption isotherms using H2 and CO2 as an adsorbate at different experimental conditions of temperature and pressure are reported. The textural properties are correlated with the ability to adsorb and retain gases related to the heat of adsorption produced between the adsorbate molecules and the adsorbent.

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