Adsorption of Off‐Gases from Steam Methane Reforming (H2, CO2, CH4, CO and N2) on Activated Carbon

Abstract

Hydrogen is the energy carrier of the future and could be employed in stationary sources for energy production. Commercial sources of hydrogen are actually operating employing the steam reforming of hydrocarbons, normally methane. Separation of hydrogen from other gases is performed by Pressure Swing Adsorption (PSA) units where recovery of high‐purity hydrogen does not exceed 80%. In this work we report adsorption equilibrium and kinetics of five pure gases present in off‐gases from steam reforming of methane for hydrogen production (H₂, CO₂, CH₄, CO and N₂). Adsorption equilibrium data were collected in activated carbon at 303, 323, and 343 K between 0‐22 bar and was fitted to a Virial isotherm model. Carbon dioxide is the most adsorbed gas followed by methane, carbon monoxide, nitrogen, and hydrogen. This adsorbent is suitable for selective removal of CO₂ and CH₄. Diffusion of all the gases studied was controlled by micropore resistances. Binary (H₂‐CO₂) and ternary (H₂‐CO₂‐CH₄) breakthrough curves are also reported to describe the behavior of the mixtures in a fixed‐bed column. With the data reported it is possible to completely design a PSA unit for hydrogen purification from steam reforming natural gas in a wide range of pressures.