Termination Reaction
Alkaline chemical transformations terminate the progressive degradation of wood polysaccharides during high-temperature pulping. In kraft and soda pulping, a stopping reaction converts reducing end-groups on cellulose and hemicellulose chains into stable alkali-resistant aldonic acid groups. The chemical mechanism occurs in wood chip digesters during the heating phase of alkaline pulping.
It ceases to protect carbohydrate polymers when alkaline cleavage creates new reducing end-groups at elevated cooking temperatures.
Chemical Kinetic
Peeling reactions sequentially remove monomer units from polysaccharide chain ends until a competitive chemical transformation halts the chain shortening. Base-catalyzed rearrangement converts the terminal glucose unit into a stable glucoisosaccharinic acid structure attached to the polymer chain. This stabilization reaction possesses a higher activation energy than the peeling process, causing termination to dominate at higher temperatures.
Anthraquinone additions accelerate stopping reactions, preserving hemicellulose yield during early digestion stages. Preserving hemicellulose increases pulp yield and enhances bonding strength in paper manufacturing. Uncontrolled peeling without adequate stopping lowers pulp yield, increasing wood consumption per tonne of pulp produced.
Pre-impregnation conditions and chemical concentration profiles determine the balance between peeling loss and chain stabilization.
Yield Preservation
Pulping yield optimisation relies on maximizing stabilization reactions relative to unselective polysaccharide dissolution. Digester control protocols optimize heating profiles to promote early termination before main delignification begins. Higher end-group stability directly improves pulp yield and fibre strength properties.
