Origin and Nature of Kraft Colour: 1 Role of Aromatics

Abstract

The chromophores responsible for kraft colour have been generally assumed to be derived from the aromatic portions of the lignin molecule. Analytical studies of the high molecular weight dissolved materials from kraft lignin, kraft cooked sugars, and extraction stage effluent by pyrolysis GC-MS, permanganate/periodate oxidation, and UV-visible spectroscopy showed that these materials had a wide variation in aromatic content but similar spectral properties. It is now proposed that carbohydrate degradation products produced by the kraft cooking of sugars are primarily responsible for the kraft colour.