The pulp and paper industry produces millions of tons of products every year. From wood to a perfectly white sheet of paper, chemical processing is required. In this work, the focus lies on the bleaching of cellulosic pulp. Great progress has been made in bleaching since chlorine based technologies have been abandoned and peroxide, oxygen and ozone based elemental chlorine free (ECF) or totally chlorine free (TCF) processes dominate in many parts of the world. In bleaching, the financial aspect is directly linked to the environmental one – effective bleaching with a lower chemical load is both, more sustainable and cheaper. Customers value bright cellulose products - paper or clothes from regenerated cellulose fiber, such as viscose - thus the bleaching also has to have a long-lasting effect, reducing the aging (discoloration) of the product as much as possible. Bleaching efficiency, aging and discoloration are directly linked to chromophoric compounds formed from polysaccharides due to chemical (oxidation) or physical stress (temperature, radiation, etc.). These compounds, conjugated carbonyl structures, are unified by their high stability towards oxidizers, moderate solubility in aqueous meadia, high extinction coefficient in the Vis range and very low amounts (ppm to ppb) in the pulp. Hydroxy-[1,4]-benzoquinone, hydroxy-[1,4]-naphthoquinone, and hydroxyacetophenone type structures dominate in cellulosic chromophores. The compounds 2,5-dihydroxy-[1,4]-benzoquinone (DHBQ), 5,8-hydroxy-[1,4]-naphthoquinone (DHNQ), and 2,5-dihydroxyacetophenone (2,5-DHAP) are particularly prevalent and are thus regarded as key chromophores.<br/>The paper will discuss advances in the chemistry of cellulosic chromophores based on the recently submitted doctoral thesis, and the corresponding publications.

Chromophores in pulp and paper: approaches towards their detection and degradation mechanisms

2019 Spring National Meeting

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