The Formation of Coniferyl Alcohol During Alkaline Delignification with Anthraquinone

Abstract

Coniferyl alcohol is the major building block of softwood lignin. Although its formation in the cooking liquor during kraft pulping is predicted by the proposed mechanism, it has not been previously found at any appreciable concentration during alkaline delignification. The reason for this is its instability in hot caustic liquors I have observed the formation of coniferyl alcohol at suprisingly high concentrations as a transient product of delignification of softwood chips in soda, sodaanthraquinone (AQ), kraft and kraft-AQ pulping under normal conditions. Higher yields were obtained with woodmeal than with chips. The maximum concentration is reached at the end of the initial delignification phase during the rise-to-temperature and is particularly dependent on the nature and quantity of additives such as Na₂S, AQ and anthraquinone mono-sulphonate. This observation supports the proposed mechanism of alkaline delignification and is, in fact, the first evidence of this mechanism based on wood rather than model compounds.