Pulps

Background: The effective separation of wood pulp components to produce high-quality, high-yield cellulose products is of high economic interest for global market players in the pulp and paper industry. Technological advances offer the opportunity to generate value out of currently unutilized wood constituents, which are normally combusted for power generation. In particular, hardwood xylan shows enormous potential, as it remains almost unaffected during alkaline Kraft cooks and can be separated from cellulose by a simple process-integrated alkaline post-extraction step. Objective: To obtain a valuable xylan product with high purity, the selective extraction of xylan without impurities is sought. Yet, residual lignin is co-extracted with xylan under alkaline conditions. To define strategies for the removal of this lignin, its solution behavior in extraction lyes should be clarified. Method: In this project, experiments including enzymatic xylan digests coupled with size exclusion chromatography (SEC) were conducted to explore the effects of lignin-xylan complexes. Results: The simultaneous decline of UV and RI signal intensities in size exclusion chromatograms after enzymatic xylan digest indicated the presence of linkages between hardwood xylan and residual technical lignin. Conclusion: The indication of linkages between xylan and lignin allows for defining bleaching strategies for the production of a high purity xylan product.