Softwood Kraft Digestion Yield Fundamentals and Hemicellulose Degradation
Preserving softwood galactoglucomannan during kraft cooking through redox chemistry increases pulp yield by three percent while reducing refining power.
Anthraquinone Catalyst
Chemical Additive
Acceleration of the delignification process in chemical pulping occurs when a cyclic organic compound is added to the cooking liquor. This substance, functioning as an anthraquinone catalyst, increases the rate of lignin removal during kraft or soda pulping processes. By increasing the reaction rate, it reduces the required cooking time and temperature.
Pulp mills utilize this compound to lower energy consumption and chemical consumption in the digester, allowing a higher throughput of raw materials. The chemical remains active in small quantities, typically making it an efficient option for modern mills.
Catalyst Mechanism
Reduction of the quinone compound by reducing sugars in the pulp slurry initiates the catalytic cycle. This reduced form of the anthraquinone catalyst then reacts with the lignin polymer, causing it to fragment and dissolve more readily. Simultaneously, the reaction oxidizes the carbohydrate end groups, which protects them from alkaline degradation.
The catalyst continuously cycles between oxidized and reduced states, allowing very small doses to be effective.
Yield Retention
Protection of the wood carbohydrates during pulping directly increases the final yield of the usable pulp. Applying the anthraquinone catalyst prevents the peeling reactions that otherwise destroy cellulose. This preservation yields a stronger fiber sheet suitable for high performance packaging.