Behavior of Eucalyptus Kraft Pulp Extractives Components across ECF Bleaching and Their Impact on Brightness Reversion

Abstract

This study investigated the chemical composition of the dichloromethane and acetone extracts of eucalypt pulp across D(EP)DP and AZDP bleaching sequences by gas chromatography-mass spectrometry (GC-MS). The bleaching stages led to the partial removal and to several oxidative transformations of fatty acids and sterols, the main lipophilic extractives found in the unbleached pulp. The pulp samples were bleached to 90–91% ISO by D(EP)DP and AZDP sequences and their brightness stability and chemical characteristics determined. The effect of aging on brightness was investigated. The AZDP bleaching sequence resulted in pulps of higher brightness stability. Furoic structures representing the main acid degradation products of HexA are suggested as the actual intermediates that cause yellowing by forming colored compounds. The AZDP process removed larger amounts of HexA across bleaching.

Keywords:

• Eucalyptus kraft pulp
• pulp bleaching
• GC-MS
• lipophilic extractives
• brightness reversion

Acknowledgments

We thank the Brazilian Research Council CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico) for research fellowships (LCAB, CRAM, JLC) and FAPEMIG (Fundação de Amparo à Pesquisa do Estado de Minas Gerais) for financial support.