Ultra-High Surface Area Activated Porous Asphalt for CO₂ Capture through Competitive Adsorption at High Pressures

This study reports an improved method for activating asphalt to produce ultra-high surface area porous carbons. Pretreatment of asphalt (untreated Gilsonite, uGil) at 400 °C for 3 h removes the more volatile organic compounds to form pretreated asphalt (uGil-P) material with a larger fraction of higher molecular weight π-conjugated asphaltenes. Subsequent activation of uGil-P at 900 °C gives an ultra-high surface area (4200 m² g⁻¹) porous carbon material (uGil-900) with a mixed micro and mesoporous structure. uGil-900 shows enhanced room temperature CO₂ uptake capacity at 54 bar of 154 wt% (35 mmol g⁻¹). The CH₄ uptake capacity is 37.5 wt% (24 mmol g⁻¹) at 300 bar. These are relevant pressures in natural gas production. The room temperature working CO₂ uptake capacity for uGil-900 is 19.1 mmol g⁻¹ (84 wt%) at 20 bar and 32.6 mmol g⁻¹ (143 wt%) at 50 bar. In order to further assess the reliability of uGil-900 for CO₂ capture at elevated pressures, the authors study competitive sorption of CO₂ and CH₄ on uGil-900 at pressures from 1 to 20 bar at 25 °C. CO₂/CH₄ displacement constants are measured at 2 to 40 bar, and found to increase significantly with pressure and surface area.