Abstract
Ph.D.
The main objective of this study was to investigate the presence, variations and the fate of
lipophilic extractives during all the stages in the dissolving pulp production process.
Lipophilic wood extractives which include fatty acids, sterols, hydrocarbons, steroid
hydrocarbons and ketones are organic compounds present in the wood and dissolving pulp
which are soluble in organic solvents. Their presence in wood and pulp has negative
effects on both the pulping process and the quality of the produced dissolving pulp.
Comparison of two Eucalyptus species (E. grandis and E. dunnii) at three different sites
(Richmond, Umvoti and Ixopo in KwaZulu-Natal Province, South Africa) revealed that
lipophilic extractives were higher in E. dunnii than in E. grandis in all the sampled sites
and that the woods at the Ixopo site were found to have the highest amount of lipophilic
extractives. The quantitative variation of lipophilic extractives in wood was found to be
significantly affected by respective sites and tree species.
The principal component analysis (PCA) model, which was used to correlate soil
parameters and amount of lipophilic extractives in woods per each site, revealed that high
amounts of lipophilic extractives were found in trees grown at sites with a high
composition of clay soil and organic matter. Thus if the industry is to avoid the high levels
of lipophilic extractives in wood, sandy sites should be the choice to grow the trees. Partial
least squares (PLS) modelling revealed that sterols and saturated fatty acids significantly
influence the quality parameters (Kappa number, viscosity, copper number, cellulose yield
and retained carbohydrates) of dissolving pulp, whereas unsaturated fatty acids and
unsaturated sterols in particular were found to positively correlate with the Kappa number,
thus affecting its measurement.The main objective of this study was to investigate the presence, variations and the fate of
lipophilic extractives during all the stages in the dissolving pulp production process.
Lipophilic wood extractives which include fatty acids, sterols, hydrocarbons, steroid
hydrocarbons and ketones are organic compounds present in the wood and dissolving pulp
which are soluble in organic solvents. Their presence in wood and pulp has negative
effects on both the pulping process and the quality of the produced dissolving pulp.
Comparison of two Eucalyptus species (E. grandis and E. dunnii) at three different sites
(Richmond, Umvoti and Ixopo in KwaZulu-Natal Province, South Africa) revealed that
lipophilic extractives were higher in E. dunnii than in E. grandis in all the sampled sites
and that the woods at the Ixopo site were found to have the highest amount of lipophilic
extractives. The quantitative variation of lipophilic extractives in wood was found to be
significantly affected by respective sites and tree species.
The principal component analysis (PCA) model, which was used to correlate soil
parameters and amount of lipophilic extractives in woods per each site, revealed that high
amounts of lipophilic extractives were found in trees grown at sites with a high
composition of clay soil and organic matter. Thus if the industry is to avoid the high levels
of lipophilic extractives in wood, sandy sites should be the choice to grow the trees. Partial
least squares (PLS) modelling revealed that sterols and saturated fatty acids significantly
influence the quality parameters (Kappa number, viscosity, copper number, cellulose yield
and retained carbohydrates) of dissolving pulp, whereas unsaturated fatty acids and
unsaturated sterols in particular were found to positively correlate with the Kappa number,
thus affecting its measurement. Viscosity of pulp which is an important quality parameter
was also found to be positively influenced by sterol residues, whereas the reducing properties of pulp were found to be affected by sterols and saturated fatty acids with a
carbon chain length of less than C20.