Production of fully bleached chemical pulp from Eucalyptus grandis wood chips and sugar cane bagasse.: Combining peroxyformic acid pulping and photochemical bleaching

An improvement in the peroxyformic acid process for the production of chemical pulps from Eucalyptus grandis wood chips and sugar cane bagasse is described. Good quality unbleached pulps were obtained (kappa number (KN) = 14 and 13, intrinsic viscosity [eta] = 1130 and 980 dm(3) kg(-1), respectively, for E. grandis and sugar cane bagasse). Efficient distillation of the spent liquor allowed the recovery of a large quantity of formic acid and phenolic lignin. The structure of the lignin fractions was studied by size exclusion chromatography, methoxyl content analysis, elemental analysis and UV, IR, H-1, C-13 and P-31 NMR spectrometries. The photobleaching of the pulps was performed using UV and visible light in presence of oxygen, hydrogen peroxide, semiconductor photocatalyst and sensitizer absorbing in the visible.