Tamara Bush

Lignin content versus syringyl to guaiacyl ratio amongst poplars.

Two oxidation techniques that afford high yields of monomers and dimers were used to more accurately estimate the syringyl to guaiacyl (S:G) ratio of hardwood lignins. Permanganate oxidation of the woodmeal after a CuO pre-hydrolysis step gave poor results and this was attributed to preferential oxidation and degradation of syringyl nuclei by CuO. However, this procedure did provide a good estimate of the percentages of both S and G phenylpropane (C(9)) units that were uncondensed. When the total S and G products from nitrobenzene oxidation (NBO) of the uncondensed fractions were corrected, credible S:G ratios were obtained. These ratios were in good agreement with results from KMnO4 oxidation of dissolved kraft lignin without CuO pre-hydrolysis. The corrected NBO method was used to determine the S:G ratio of 13 poplars, and the values ranged from 1.01 to 1.68. Unlike results from other investigations, an excellent linear correlation (R(2) =0.846) was obtained for a decreasing lignin content (28% to 16.5%) with an increase in the S:G ratio.

Cross polarisation/magic angle spinning C-13-NMR spectroscopic studies of cellulose structural changes in hardwood dissolving pulp process

Abstract Cross polarisation/magic angle spinning 13C NMR spectroscopy has been used to study structural changes in cellulose induced by the dissolving pulp process. The cellulose structure in several dissolving pulps was investigated for commercial and laboratory cooked Eucalyptus 92α and 96α. The average lateral dimension, or average thickness, of the cellulose fibril aggregates is related to the amount of surface area exposed and could be one controlling factor for the chemical reactivity of commercial dissolving pulps during modification reactions. The thickness of the cellulose fibril aggregates governs the amount of surface area present in the fibre wall, and cellulose surface material constitutes the part of the cellulose that is directly accessible to reagents. In all sample series investigated, the raw pulp was found to be less aggregated than the corresponding bleached final pulp. Furthermore, an irreversible increase in fibril aggregate width was observed on free drying for both laboratory cooked and commercial pulps. Upon rewetting with water, the freely dried 96α pulp was found to be more aggregated than the freely dried 92α pulp, although sugar analysis showed very similar carbohydrate compositions. As indicated by the molecular mass distribution, the commercial 92α pulp contained larger amounts of degraded cellulose; this may be a plausible explanation for the different behaviour of the 92α and 96α pulps during free drying.

Equilibrium and Kinetic Studies for Extracting Cu, Mn, and Fe From Pulp Wastewater onto a C-18 Column with Acetylacetone Complexing Ligand

A preconcentration procedure using solid phase extraction of heavy metals in pulp wastewater is reported. The procedure was optimized by using model solutions of selected heavy metals to investigate the effect of matrix constituents. Equilibrium studies highlighted the bonding and adsorption characteristics. The metal recoveries after spiking pulp waste filtrate with Cu, Ni, and Pb each at 0.1 and 0.2 ppm was 120, 91, and 93%, respectively. The Freundlich adsorption isotherms with correlation coefficients (R2) 0.612, 0.810, and 0.750, showed a better fit compared to Langmuir isotherm values of 0.277, 0.389, and 0.272 for Cu, Mn, and Fe, respectively.

An accurate and non-labor intensive method for the determination of syringyl to guaiacyl ratio in lignin

The syringyl to guaiacyl (S:G) ratio of hardwood lignin has long been identified as a significant parameter in delignification processes and more recent results have shown that it is also important in determining the amount of ethanol that can be obtained from fermentation of hydrolyzed wood. Acidolysis of Klason or acid insoluble lignin in dioxane/water/HCl was being investigated when syringyl and guaiacyl nuclei with a diketone-containing sidechain were observed as the major products. The area ratio of the two gas chromatogram peaks appeared to be indicative of the S:G ratio. After optimization of the method the relative standard deviation was found to be in the range of 0.3-3.76% for Klason lignin from a wide range of Eucalyptus grandis grown in South Africa. The method was then compared to nitrobenzene oxidation (NBO) using 13 poplars in a double-blind study. The respective S:G ratios were used to calculate percentages of S units and when these values were plotted against each other a linear correlation was obtained with a slope of approximately 1.0 (R(2)=0.86). The largest discrepancy for any poplar was 6.9% (62% vs. 58% S units). Both methods convincingly demonstrated a significant decrease in lignin content with an increase in the S:G ratio. Discussion is presented on a series of reaction that could lead to the formation of the two diketones.

Supra-Molecular Structure and Chemical Reactivity of Cellulose I Studied Using CP/MAS 13C-NMR

© 2013 Chunilall et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Supra-Molecular Structure and Chemical Reactivity of Cellulose I Studied Using CP/MAS C-NMR

Quantitative assessment of xylan distribution across the secondary cell wall layers of Eucalyptus dissolving pulp fibres

Abstract A quantitative method has been developed for assessment of the distribution of xylan across the secondary cell wall layers of Eucalyptus dissolving pulp fibres by means of a carbohydrate binding module (CBM), CtCBM6, in combination with transmission electron microscopy (TEM). To ensure reproducibility and to minimise non-specific labelling, various parameters were optimised, namely the size of the gold colloid marker, CtCBM6 concentration, and the selection of buffer solutions. The method was replicated on processed Eucalyptus fibres containing different xylan contents. Reproducible xylan counts and distributions across the secondary cell wall layers were obtained for unbleached and bleached Eucalyptus fibres. The xylan distribution pattern across the cell wall layers S1, S2 and S3 was similar, but the S1 and S3 layers contained after bleaching more xylan than the S2 layer. The technique has a wide range of applications in basic wood research as well as in the analysis of technological processes.

Evaluation of the influence of lipophilic extractive residues on dissolving pulp quality parameters by partial least squares method of chemometrics

Dissolving pulp samples collected from the various pulping stages of the acid-bisulphite process were analysed for the lipophilic extractive residues as well as their effects and influence on the quality parameters of dissolving pulp were evaluated. The results obtained using the partial least squares (PLS) regression model showed that sterols, fatty alcohol, saturated and unsaturated fatty acids significantly influenced/affected the viscosity, Kappa number and carbohydrates in the pulp. The PLS model clearly separated the analysed pulp in terms of the species of the raw materials and pulping stages. Furthermore, it was observed that lipophilic extractives are negatively correlated to the yield of α-cellulose. Sterols, fatty acids and alcohols negatively influenced glucose in pulp, while xylose was found to be positively correlated to these components. Generally, the components of lipophilic extractives that have a major influence on the quality parameters were found to be sterols and saturated fatty acids.

Study of the Fate of Lipophilic Wood Extractives During Acid Sulphite Pulping Process by Ultrasonic Solid-Liquid Extraction and Gas Chromatography Mass Spectrometry

Abstract Lipophilic extractives in dissolving pulp are still a big concern for pulp industries due to their detrimental effect on the quality of pulp. Since lipophilic extractives remaining in pulp are trapped in low-accessible fiber structures, effective extraction methods need to be established for studying their fate in the process. A simple, ultrasonic, solid liquid extraction established in this study was found to be more effective in capturing extractive residues in all “elemental chlorine-free” bleaching stages. Its efficiency was dependent on the extraction temperature, time, and solvent composition. A linearly correlated removal pattern of sterols and unsaturated fatty acids by the bleaching sequence was observed. It was further found that the bleaching combination did not fully remove lipophilic extractives. This study suggests an opportunity to explore ultrasonication-based extraction as an effective extraction procedure prior to gas chromatography mass spectrometry analysis for monitoring extractives in pulp.