Asphaltene-Derived Activated Carbon and Carbon Nanotube Membranes for CO₂ Separation

Due to large energy requirements of the traditional gas separation processes, novel and less energy-intensive technologies, such as adsorption- and membrane-based ones, are anticipated to play major role in future industrial separations. Thus, finding new means for economical fabrication of materials related to these processes is of significant importance to facilitate their implementation in large-scale operations. In this work, we synthesized high-quality activated porous carbons (AC) and carbon nanotube (CNT) membranes using asphaltene, an abundant waste of the petroleum industry. The resulting materials were tested for CO₂ separation in adsorption and membrane modes. Among the various porous carbons produced, AC from raw asphaltene reached a CO₂ sorption capacity of 7.56 mmol/g at 4 bar and 25 °C with a relatively low heat of adsorption (up to 23 kJ/mol) implying low energy requirement for regeneration. The versatility of the asphaltene precursors in the formation of carbon nanomaterials was also demonstrated by growing, for the first time, CNT membranes via template-based, catalyst-free carbonization of asphaltene inside the pores of anodized alumina. The resulting CNT membranes attained a promising separation performance with permeability ratios exceeding the respective Knudsen values for H₂/CO₂, N₂/CO₂, N₂/CH₄, and H₂/CH₄ gas pairs.