Due to cotton’s
declining sustainability, more lignocellulosic
materials are being used to produce dissolving pulp for textile applications.
Pre-hydrolysis kraft is one of the main processes used to produce
this material. Pre-hydrolysis under conventional conditions removes
most of the hemicelluloses, but the majority end up as xylose and
furfural, traditionally burned in a recovery boiler. The xylooligosaccharides
(XOS), derived from hemicelluloses are a specialty product and can
be recovered but requires adapted operative conditions. Thus, the
objective was to recover XOS and evaluate the effect of pre-hydrolysis
conditions on the final pulp characteristics. A flow-through reactor
(FTR) was used to study the pre-hydrolysis, which allowed for modification
of the retention time of the xylan in the free liquor after extraction
from wood. The results have shown that by changing the fluid retention
time in the pre-hydrolysis, the proportion of XOS/xylose/furfural
recovered can be strongly changed. The hemicellulose content of the
dissolving pulp decreased from 6.8% to about 2.6% using the FTR pretreatment.