CATALYTIC OXYGEN BLEACHING OF WOOD PULP WITH METAL PORPHYRIN AND PHTHALOCYANINE COMPLEXES

A series of porphyrin and phthalocyanine complexes of Co, Fe, and Mn is screened for catalytic activity in the oxygen bleaching of unbleached softwood kraft pulp in 1 M KOH at 25 and 100 degrees C under 0.8 MPa oxygen pressure. The Mn(III) complex of meso(tetrasulfonatophenyl) porphyrin, isolated as Na3Mn(TSPP).4H(2)O and abbreviated as Mn(TSPP), is shown to promote delignification and suppress cellulose degradation in oxygen bleaching. The influence of bleaching time, pH, temperature, oxygen pressure, and Mn(TSPP) charge on catalytic activity is assessed by factorial and parametric experiments. The Mn(TSPP) is effective at a minimum concentration of about 0.025 g/L (0.023 x 10(-3) M) and is most beneficial for bleaching rate and selectivity in 1 M KOH at high temperature and oxygen pressure (100 degrees C, 0.8 MPa O-2).