Abstract:
Pretreatment is critical to the conversion of biomass into valuable chemicals. Willow
(Salix spp), consisting mainly of polysaccharides and lignin, was used in this study of
lignin in three stages. The delignification reaction using the organosolv process, the
recovery of lignin from organosolv spent liquor by precipitation and dissolved air
flotation, and the use of lignin for polymer production were studied.
A novel method of determining delignification activation energy using fewer pulping
experiments was developed. Several reaction rate constants were determined during a
single pulping run by examining kinetics at different reaction times with a slowly
increasing temperature. The effects of changing ethanol concentration were then
investigated using this method. Only the change in pH caused by changing ethanol
concentration had a significant effect on delignification rate.
Prehydrolysis has been used to selectively remove hemicellulose prior to organosolv
pulping. De-ashing is a treatment to remove the acid-neutralising components (ash and
extractives) of biomass. It was previously thought that organosolv delignification
proceeded faster after prehydrolysis due to increased accessibility of solvent to lignin.
However, prehydrolysis did not result in faster subsequent delignification compared to
de-ashing. De-ashing and prehydrolysis treatments removed the acid neutralising
components of wood while prehydrolysis also removed a portion of the polysaccharides.
It may be the lower pH resulting from prehydrolysis that increases subsequent organosolv
delignification rate compared to untreated feedstock.
Upon dilution of organosolv black liquor, lignin forms a precipitate, which is
typically removed by filtration or centrifugation. The use of dissolved air flotation (DAF)
presents a low cost alternative that utilizes the hydrophobicity of organosolv lignin. The
parameters important to the dissolved air flotation of organosolv lignin were studied
using fractional factorial design. Fastest flotation occurs when saturation pressure is high
and black liquor-water mixing is rapid resulting in the redistribution of micro-bubbles
Abstract
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during floc formation. Precipitation must occur below 35°C to cause sufficient
flocculation.
Phenol formaldehyde resins were prepared with 20% w/w of the phenol replaced by
lignin (lignin-PF resin). Lignin-PF resins prepared from the most depolymerised lignin
had comparable strength to pure PF resin when strength was compared using a lap joint
test.