Sulfur dioxide as an activating agent for sulfur-impregnated activated carbon produced from dense petroleum coke

Abstract

To develop novel sorbent materials for capturing vapor mercury from industrial flue gases at high temperatures, high-sulfur oil-sands fluid coke was activated using 50% sulfur dioxide (SO2) at 700°C under various pre-treatment conditions. Pyrolysis in nitrogen prior to activation significantly decreased specific surface area (SSA) of the product, which was attributed to the thermoplastic behavior of coke at high temperatures. Air pre-oxidation suppressed this effect and provided an enhancement over non-pyrolyzed coke, with SSA peaking at 447 m2/g after 5 h activation. Acid washing of air pre-oxidized activated coke in 10% hydrochloric acid increased SSA by removal of inorganic ash which added weight but contributed minimal surface area. Decreasing initial particle size range from 212–300 to 53–106 μm significantly increased SSA, which was attributable to an outer porous layer of constant thickness. Under optimized conditions, an SSA of 531 m2/g was achieved – the highest reported in literature for physically activated fluid coke. Coke activated with SO2 displays a high mesoporous fraction and pore surface coverage by sulfur groups that were thermally stable up to 500°C.