Lipophilic Extractives in Eucalyptus globulus Kraft Pulps. Behavior during ECF Bleaching

Abstract

The composition of E. globulus kraft pulp lipophilic extractives and their behaviour during an ECF (DEDED) bleaching sequence were investigated. Sterols; fatty acids, including several α‐ and ω‐hydroxyfatty acids; and long‐chain aliphatic alcohols are the major lipophilic extractives of the unbleached pulp. During the bleaching, about 80% of the aliphatic extractives are removed from pulp (ca. 70% of the sterols, 70% of the fatty acids, and 90% of the long‐chain aliphatic alcohols). The decrease of sterols is mainly due to the degradation of β‐sitosterol by chlorine dioxide, while the decrease of fatty acids and alcohols is essentially assigned to their extraction and elimination with the alkaline filtrates. The major chemical transformations in pulp extractives composition and structure occur in the last bleaching stages. Thanks are due to FCT and ESF for the awarding of a PhD grant to C. S. R. Freire, within the European Community Support Framework III, to the Forest and Paper Research Institute RAIZ, for supplying the industrial E. globulus kraft pulp and for the facilities conceded for the kraft pulping trials. Finally, thanks are due to Dr. Les West from Kraft Foods, USA for his kind offer of a sample of 2‐hydroxyoctadecanoic acid.