Improving Alkaline Peroxide Delignification Using a Vanadium Activator, 1998 Pulping Conference Proceedings

Transition metals have been used as additives in peroxide bleaching, mostly under acidic conditions. The effectiveness of such systems may be due to the in situ formation of peroxometal complexes. To examine this hypothesis, we synthesized one of these compounds. We then examined its delignification efficiency by paying attention to the reaction parameters and pulp properties. The effects of ammonium triperoxo-phenanthroline vanadate (ATPV) were examined under conditions compatible with conventional P-stage bleaching practices. Vanadium (V) peroxo complexes transfer oxygen to aromatic hydrocarbons at room temperature. The presence of 0.5% of APTV in the bleach liquor improved the delignification efficiency and pulp brightness. At this charge the delignification efficiency of the peroxide stage increased by at least 50%. The delignification efficiency of an activated P stage is affected more by temperature than by retention time. At the same kappa number, the viscosity values for an activated and a control pulp were approximately the same. Transition metal peroxo complexes offer structural possibilities that have yet to be explored as active oxygen carrier compounds, with the possibility of regeneration.