Effect of autohydrolysis on alkaline delignification of mixed hardwood chips and on lignin structure

Autohydrolysis (AH) prior to the kraft process is one way to valorize hemicelluloses. The presented results show that AH also has a beneficial effect insofar as kraft cooking can be substituted by soda cooking, and higher brightness levels can be achieved under the same bleaching conditions. The lignin has more free phenolic groups after All, which is attributable to depolymerization, and which could partly explain the better pulping and bleaching results. Another explanation could be the lower amount of lignin involved in lignin carbohydrate complexes after an AH step.