The results of beech wood extraction using green liquor, NaOH, Na2CO3, NaHCO3
and NaAc solutions were compared with hot water extraction in order to select a method of
hemicelluloses extraction for preparation of value added products from xylose or furfural and
simultaneously to utilize the extracted wood for kraft pulp manufacture.
Extraction of beech wood with hot water is resulting in considerably higher dissolution
of wood components, mainly xylan when compared with extraction by alkali solutions.
A disadvantage of wood extraction by water is degradation of polysaccharides remaining in
the extracted wood resulting in the following alkaline cooking process decrease of yield and
strength properties of pulp. In view of the high xylose yield in the hydrolysed water extract it
will be necessary to find out at which level of extraction degree no significant degradation of
polysaccharides occurs in the extracted wood.
Alkaline extraction agents promote alkaline degradation of the dissolved hemicelluloses and
thus reduce the content of sugars particularly xylose in hydrolysed extracts.
Out of tested extraction agents good results were obtained in extraction of beech wood with
green liquor. In extraction with green liquor pH decreases to the near neutral region and the
rate of wood components dissolution is high. However, xylose yield is about by half lower when
compared with hot water extraction. The advantages of green liquor extraction is absence of
significant degradation of polysaccharides in the extracted wood and availability of green liquor
from the recovery cycle of a kraft pulp mill.