Production of kraft pulp from Ochroma pyramidale wood

ABSTRACT Brazil stands out in the international scenario in the production of short-fiber pulp. Despite the great Brazilian biodiversity, that production is based on exotic Eucalyptus clones. In this sense, there may be great potential in the assessment of new sources of fibers from the Brazilian flora, including the Amazon. The present study aimed to assess the technical potential of the wood of Ochroma pyramidale (Malvaceae) for the production of kraft pulp. Four-year-old trees were harvested from a commercial forest for lumber production in Mato Grosso state (Brazil). We determined the wood’s chemical compositions (holocellulose, Klason lignin, soluble lignin, extractives and ash contents), physical properties (density and porosity), and fiber morphology (fiber length, width and thickness, lumen diameter, wall fraction, coefficient of flexibility, and slenderness and Runkel ratios). The wood was subjected to pulping with an effective alkali charge ranging from 10 to 24%, with intervals of 2%. Ochroma pyramidale wood presented characteristics favorable to the production of cellulosic pulp, such as appropriate fiber dimensions and low lignin, extractives, and ash content. The amount of residual active alkali and pH of the black liquor were positively related to the increase of the alkali charge employed in the pulping process. The increase of alkali charge decreased the pulp yield, kappa number and waste content, and increased the hexenuronic acid concentration.