A study on the porosity development for biomass based carbonaceous materials

Abstract

This study deals with the structural and morphological changes occurring during pyrolysis and activation steps for the production of porous carbons from an arid-land plant Euphorbia rigida. A fixed-bed retort was used for slow pyrolysis and for further activation processes. Effect of pyrolysis atmosphere was examined at 550 degrees C and char yields were calculated to be 22.6, 23.1 and 17.5% under static, nitrogen and steam atmospheres respectively. Solid product obtained under static atmosphere was then impregnated with different chemicals (HCl, KOH, K2CO3, H2SO4, H3PO4, NaOH, ZnCl2) and a second thermal treatment was applied under different activation atmospheres. It was observed that the impregnation material, impregnation ratio and activation technique showed a strong influence on the yield and porous texture of the resulting carbons. On the basis of BET surface areas, most effective chemical agent was selected as K2CO3 giving a specific surface area of 1079 m(2)/g and microspore volume of 0.443 cm(3)/g. The physical-chemical properties of the chars and activated carbons were investigated by proximate and ultimate analyses, FT-IR, SEM, EDX, XRD and iodine number. In addition, surface functional groups were classified by Boehm titration method. Results suggest that chemical activation of E. rigida char produces valuable activated carbons under proper conditions.