Abstract <p>A method is described for producing a microporous carbon sorbent based on a heavy oil refining residue—petroleum asphalt—which, after carbonization at 500°C, was mixed with potassium hydroxide in a ratio of from 4 : 1 to 1 : 1 in an AGO-2 planetary centrifugal mill with a centripetal acceleration of the grinding media of 1000 m/s², followed by high-temperature activation at 800°С for 60 min. For the obtained samples, adsorption isotherms were measured of pure gases of CO₂ gases and CH₄ at 273 and 298 K. Thus, for samples obtained with a KOH/asphalt ratio of 1 and 2, at 273 K and 1 bar, the adsorption capacity for CO₂ and CH₄ amounted to 5.6–5.9 and 2.2 mmol/g, respectively. The best CO₂ adsorption capacity at 273 K and 1 bar in the studied series of samples—6.3 mmol/g—was obtained for the KOH : asphalt = 3 : 1 sample. It was found that mechanical activation of asphalt and KOH promotes the formation of carbon materials with a more developed porous structure, namely, an increase in textural characteristics by 30% compared to samples prepared without MA. Thus, the presented approach of using mechanical and chemical activations contributes to the production of porous carbon that meets the requirements of adsorption separation of a mixture of methane and carbon dioxide gases.</p>