PEROXYFORMIC ACID PULPING OF EUCALYPTUS-GRANDIS WOOD CHIPS AND SUGAR-CANE BAGASSE IN ONE-STAGE AND CHARACTERIZATION OF THE ISOLATED LIGNINS

An improvement in the peroxyformic acid process for the production of chemical pulps from Eucalyptus grandis wood chips and sugar cane bagas se is described. The pulping of these lignocellulosics was carried out in a single stage at 75 degrees C (3 h) in order to benefit from the action of the peroxyformic acid and a subsequent formic acid reflux (1 10 degrees C, 2 h), using the same liquor. Efficient distillation of t he spent liquor allowed recovery of a large quantity of formic acid an d phenolic lignin, the latter obtained after mild saponification, foll owed by precipitation in acidic media. The pulping process was complet ed with a 0.25M NaOH extraction of the pulp at 60 degrees C to dissolv e more lignin. Good quality unbleached pulps were obtained. Kappa numb ers (KN) of 14 and 13, and intrinsic viscosities [eta] of 1130 and 980 dm(3) kg(-1) were obtained, respectively, for E. grandis and sugar ca ne bagasse. The structures of the lignin fractions were studied by siz e exclusion chromatography; methoxyl content analysis; elemental analy sis; UV; IR; and H-1, C-13, and P-31 NMR. The lignins were found to un dergo demethylation, condensation, ring opening, formylation of hydrox yl groups, and aryl-alkyl ether cleavage during pulping.