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

Abstract

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.