Narrow pore distribution formed in steam and CO 2 gasified cokes of different origin

Abstract

A new high resolution sorption (HRS) technique has been employed to characterize steam and/or CO 2 gasified petroleum cokes, coal chars, and carbons derived from peat and bone char. A lignite gasified by mild oxidation in steam was also studied. We have found that all of these coke samples show a very narrow pore feature centered at 3.9 nm diameter. High pressure mercury porosimetry of a petroleum coke gasified in a fluidized bed at temperatures >900°C confirm the HRS analysis of 3.9 nm pores formed on gasification. We propose that a primary structural unit, analogous to a micelle or a spherulitic polymer micro domain, forms during the coke-formation process, and this unit is 4 nm in diameter. We believe that gasification attacks these structural units generating a very narrow pore structure within the coke. In other work, gasification of carbon blacks by mild oxidation has been shown to attack the center of the particle and proceed to the exterior of the spherulitic structure. Such a process would account for the generation of narrow pores within a coke following gasification in steam and/or CO 2.