Degradation of cellulosic key chromophores by ozone: a mechanistic and kinetic study

Abstract Chromophores, colored substances of rather high stability that reduce brightness, are present in all kinds cellulosic products, such as pulp, fibers, aged material, and even very low concentrations highly bleached pulps. Thus, they the prime targets industrial pulp bleaching. In this study, three key chromophores 2,5-dihydroxy-1,4-benzoquinone (DHBQ, 1 ), 5,8-dihydroxy-1,4-naphthoquinone (DHNQ, 2 2,5-dihydroxyacetophenone (DHAP, 3 ) were with ozone at pH resembling conditions (Z-stage). Bleaching kinetics followed by UV/Vis spectrophotometry. The chemical structures degradation products analyzed using NMR spectroscopy well GC/MS confirmed comparison authentic reference compounds. main, stable intermediates ozonation reactions have been elucidated employing not excess but roughly stoichiometric amounts: mesoxalic acid ( 4 from DHBQ rhodizonic 5 DHNQ hydroxy-[1,4]-benzoquinone 8 DHAP ). As final a large ozone, complex mixture carboxylic acids (C to C was obtained, being formed subsequent condensation smaller fragments (malonic acid) than directly products. At shorter reaction times lower excess, some aldehydes ketones contained addition. completely tended undergo further changes, decarboxylation reactions. mechanisms intermediate formation re-condensation described discussed. Graphic abstract