Catalytic activity of active carbons impregnated before activation of pinewood sawdust and nutshells to be used on the control of atmospheric emissions

Abstract

This work analyses the catalytic activity of metal oxides impregnated on activated carbons to be used for the complete oxidation of benzene present in atmospheric emissions. When the impregnation step is performed before CO 2 activation, the knowledge about catalytic activity is as yet quite scarce, being the main objective of the study here reported. Pinewood sawdust and nutshells were recycled to produce the activated carbons. Non-expensive metal oxides (CoO, Co 3O 4 and CrO 3) were impregnated. When the impregnation was performed before CO 2 activation instead of after activation, at 523 K the kinetic constants were 3.6–4.3 times higher for sawdust carbons, and 2.1–2.7 times higher for nutshell carbons, due to a better metal oxide dispersion on higher mesopore areas and on wider micropores. With Co 3O 4 as catalyst, a benzene conversion of 90% was reached at a lower temperature than with CrO 3 (472 and 558 K, respectively). The carbons impregnated before CO 2 activation allowed very good conversions at temperatures that guarantee carbon stability (lower than 575 K). The results obtained led to the conclusion that activated carbon is a suitable support for metal oxide catalyst aiming the complete oxidation of benzene, mainly if an adequately porous texture is induced, proceeding to the impregnation before CO 2 activation.