Activated carbons prepared by pyrolysis of mixtures of carbon precursor/alkaline hydroxide

摘要

In the present paper, heat-treatments in N_2 atmosphere of mixtures of different precursors and alkaline hydroxides are studied. The paper analyses the effect that the precursors' nature (coals, lignocellulosic materials and carbon fibre) has on the final porosity of the resulting activated carbons. The results show that this physical mixing method can be effectively used for all the selected precursors, both with NaOH and KOH. However, differences in adsorption capacity and porosity distribution are observed depending on the precursor and on the hydroxide used. The different behaviour exhibited by both activating agents can be explained by the different structural order in the raw materials. As a general trend, NaOH is more efficient in the activation of low structural-ordered materials, whereas KOH is more effective for the highly ordered materials, what indicates differences in the activation performance of both hydroxides. The results obtained from precursors submitted to a pyrolysis step previous to the heat-treatment of the carbon precursor-hydroxide mixtures corroborate the observed tendencies.