Effect of chemical composition and wood properties on kraft pulping of eucalyptus - Difference in soluble and insoluble wood extractives between Eucalyptus viminalis and Eucalyptus globulus

The corrected kraft pulp yield (41.5 %) of Eucalyptus viminalis was 6.1 % lower than that (47.6%) of Eucalyptus globulus. To elucidate the difference of the pulp yields, the contents of soluble and insoluble extractives were determined. Experimental results indicated the following from comparison of the two species: (1) E. viminalis contained 0.9% more lignin and 0.7% less a-cellulose, (2) E. viminalis contained 0.8 % more alcohol-benzene soluble extractives, (3) although both species had the same amount of insoluble hydrolyzable tannin, E. viminalis contained 2.3% more aqueous acetone soluble extractives mainly composed of hydrolyzable ellagitannin, (4) E. viminalis contained at least 0.8% more insoluble condensed tannin mainly composed of proanthodelphinidin, and (5) difference (2.6%) in the lignin-free kraft pulp yields of soluble extractives-free E. globulus and E. viminalis may attributable mainly to that of the content of insoluble condensed tannin. These observations suggest that the lower kraft pulp yield of E. viminalis can, to a large extent, be attributed to higher soluble and insoluble tannin contents.