Catalysis and activation of oxygen and peroxide delignification of chemical pulps: a review.

Application: This review serves as guide to recent research and patents pertaining to oxygen and per-oxide delignification, peracids, and dioxiranes.

Oxygen and hydrogen peroxide have always been technologically attractive oxidants to the pulp and paper industry, with their significance becoming of increasing important as environmental regulations become more stringent.

This paper critically reviews a variety of research endeavors that have focused on catalyzing oxygen delignification and activating peroxide delignification of chemical pulps. We also cover peracids, which we consider as organic molecules containing active oxygen. Peroxymonosulfuric acid, another example of an inorganic molecule containing active oxygen, improves oxygen delignification of kraft pulps. Dioxiranes also can transfer a single activated oxygen atom onto aromatic and unsaturated substrates. Consequently, we include dimethyldioxirane in our review for its potential as a novel and selective non-chlorine containing bleaching agent for the production of fully bleached, totally chlorine-free pulp.

Another form of activated oxygen may be present within peroxycarboximidic acid, which is thought to be an intermediate in the interaction of cyanamide with peroxide, proposed as a peroxide activator for the bleaching of sulfite pulps. Finally, our critical review covers the recent scientific and patent literature which contains a number of examples where transition metals have been used as additives in peroxide and oxygen delignifications, such as tungsten, molybdenum, certain manganese complexes, silicomolybdates, and polyoxometalates.

Suchy and Argyropoulos are with PAPRICAN and the Department of Chemistry, McGill University Pulp and Paper Research Centre, 3420 University St., Montreal, Quebec, Canada H3A 2A7. Contact Argyropoulos by email at [e-mail] or Suchy at [e-mail].