NO adsorption on activated carbon fibers from iron-containing pitch

Abstract

Iron-containing activated carbon fibers (Fe-ACF) have been prepared by a novel method consisting of mixing an iron precursor with raw pitch before carbon fiber formation, and further CO2 activation of the Fe-CF. The NO adsorption experiment revealed that iron species are accessible to gases and that they activate NO improving adsorption into the fiber microporosity. The chemisorption of NO and the subsequent dimer (N2O2) formation is, in general, the rate-limiting step. Metallic iron and/or partially reduced iron compounds are the most active iron species. However, in the fibers with narrow micropores dimer diffusion in the microporosity is the slowest step and, consequently, an appropriate pore size is required from a kinetic point of view. The most suitable samples prepared were those with pores wider than 0.7 nm which contain partially reduced iron species. Finally, NO adsorbed can be further recovered by heating the spent adsorbents at a quite low temperature (500 K). Fresh and regenerated adsorbents show similar NO adsorption capacity.