Analytical characteristics of plantation eucalypt woods relating to kraft pulp yields

Abstract

Correlations of the chemical composition of a series of 11 Eucalyptus globulus wood samples ranging in ages from 6 to 32 years, and 21 seven year old E.nitens wood samples have been made with the yields and the composition of their kraft pulps. Analyses for extractives, lignin, pentosan, acetyl, glucuronic acid, and carbohydrates were carried out. The carbohydrates were determined as pentosans, and as their constituent sugar monomers after acid hydrolysis of the unextracted woodmeals and analysis of the hydrolysates by high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). The total carbohydrates (calculated by difference) and extractives contents of E.globulus wood samples were well correlated with pulp yield at Kappa no.15, and lignin was moderately well correlated total carbohydrates for both species (measured by HPAEC-PAD) were only moderately well correlated with pulp yield. For both species, the correlation of pulp yield with cellulose and glucose was good, but was slightly inferior with hemicellulose, xylose, and pentosan. Wood samples which gave high pulp yields had cellulose as a high proportion of their polysaccharide fraction, and this trend was also evident in the pulps derived from them. Both wood samples showed variation in their oxidation products ; for the E.globulus woods the syringaldehyde/vanillin ratios were moderately well correlated with pulp yield, but for the E.nitens woods, the correlation was poor. The hydrolysis-HPAEC-PAD method for carbohydrates is proposed as a suitable basis to explore the relationship between the chemical composition of plantation eucalypt woods and their pulp yields and papermaking properties.