Active carbon was prepared from Yallourn brown coal char using steam and carbon dioxide activation in a laboratory rotary kiln. The activation rate with steam was faster than that with carbon dioxide. The pore structure of the active carbons was characterized using the nitrogen isotherms at 77 K. The pore volume and specific surface area of the active carbon increased with the carbon bum-off, and compared to carbon dioxide, steam activation produced active carbon that was richer in mesopores by increasing the pore size from micropores to mesopores. The porosity of the active carbons was related to the ability to adsorb maltene, the normal hexane-soluble fraction, in the vacuum residue of petroleum crude. The steam-activated carbon rich in mesopores had a greater ability to adsorb maltene, which consists of large-molecular-weight hydrocarbons. (C) 2007 Elsevier B.V. All rights reserved.