KOH activation of pitch-derived carbonaceous materials-Effect of carbonization degree

Two series of mesophase pitches and semi-cokes of different carbonization degree were produced by heat treatment of anthracene oil derived pitches P1 and P4 in the temperature range of 460-700 degrees C. These carbonaceous materials were activated with potassium hydroxide at 700 degrees C using 1:3 reagents ratio to assess the effects of the precursor optical texture and carbonization degree on the activation behavior. The results show that the increase in the pitch pretreatment temperature suppresses propensity to the pore generation while enhancing particle breaking. The effect can be illustrated by decreases in the BET surface area S-BET from -2700 to similar to 1500 m(2) g(-1) and the micropore volume V-DR from similar to 0.85 to similar to 0.45 cm(3) g(-1). These parameters are inversely related with the H/C atomic ratio of precursor. In contrast, the anisotropic development of pitch coke, varying from flow type to mosaics, has a slight effect on the activation behaviour. The mechanism of porosity generation, that is proposed, stresses the role of hydrogen occurring at the edges of graphene layers and potassium metal insertion/deinsertion on the porosity development and particle disintegration during KOH activation of pitch-derived carbons. (C) 2010 Elsevier B.V. All rights reserved.