Hydrogen separation from gas mixtures: evaluation of adsorbent performance using the IAST model

Samples of commercial adsorbents – activated carbon (AC), zeolite (ZS), and silica gel (SG) – were studied in the adsorption processes of hydrogen, methane, nitrogen, carbon dioxide, and carbon monoxide in order to assess their efficiency for hydrogen purification from gas impurities. The composition and morphology of the materials were characterized using scanning electron microscopy and energy-dispersive X-ray microanalysis. Textural properties (specific surface area and pore structure) were determined from nitrogen cryosorption data using the BET, Gurvich, and BJH models. Adsorption isotherms were obtained for all studied gases at pressures up to 25 atm and temperatures ranging from 0 to 50 °C. Isosteric heats of adsorption and ideal selectivities for the “impurity gas – hydrogen” pairs were calculated. To evaluate the behavior of the studied adsorbents toward multicomponent gas mixtures, simulations were performed using the Ideal Adsorbed Solution Theory (IAST). This approach revealed that in real mixtures, the selectivity SIAST(CO₂/H₂) increases by a factor of 1.5–3 compared to the values estimated from single-gas data. 

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