THE EFFECT OF LIGNIN COMPOSITION ON DELIGNIFICANTION RATE OF SOME TROPICAL HARDWOODS
The effect of lignin composition on delignification rate and pulp properties of albizin (Paraseriantes falcataria L. Nielsen). Gmelina (Gmelina arborea Linn), yellow meranti (Shorea acuminatissima Sym), and kapur (Dryobalanaps aromatica Gaertn.) woods was determined. The lignin characterization showed that the syringl-guaiacyl rattio of albizia, gmelina, kapur, and yellow meranti woods are 2.03, 2.02, 1.87, and 1.30, respectively. It means that the lignin structure of the above mentioned woods are predominated by syringyl units. To asseas the influence of lignin structure on delignification rate and pulp properties, these wood samples were then subjected to the kraft pulping process under the following conditions: wood-to-liquor ration = 1:4, cooking temperature = 170°C, time to cooking temperature = 90 minutes, cooking time = 90 minutes, total active alkali =16%, sulfidity = 22.5%. From the present investigation it can be explained that the delignification rate of hardwood containing syringyl-rich lignin was higher than that of hardwood containing syringyl-poor lignin. The physical properties of pulp from hardwood containing syringyl-rich lignin are also higher than that of hardwood containing syringyl-poor lignin.