Spruce lignin content

Figure 11. Molecular weight distributions of middle molecular weight phenolic (solid line) and acidic (broken line) fractions from methanol extract, and higher molecular weight acidic (dotted line) fraction from subsequent aqueous 96% dioxane ract, of spruce wood chips degraded by P, ckrysosporium to 20% loss in lignin content Sephadex LH60A).10 M LiQ-DMF profiles adapted and redrawn from reference 67.

Figure 2 shows the extent of dissolution of red spruce in methylamine, the amount of precipitate collected in the first trap upon complete depressurization to 1 bar, and the Klason lignin content in the wood residue after extraction, as functions of extraction time. The total dissolution and precipitation are normalized with respect to oven dry weight of initial wood. The extraction conditions were 185°C, 275 bar, and 1 g/min solvent flow rate. As shown in the figure, dissolution initially increases with time and levels off at about 28% by weight. The precipitates which were collected as solids follow a similar trend. The Klason lignin content of the wood residue decreases with extraction time, from an initial value of 26.5% down to 10.1% after 5 h of extraction. 

Dissolution of almost 40% of powdered beechwood in this way 20) suggests that the benzyl aryl ether content of beech lignin is much higher than that of spruce lignin. 

Coniferaldehyde structures are the major leucochromophore present in spruce lignin. These end groups are also present to a large extent in unbleached mechanical pulps and are responsible for a major portion of the absorption of UV-radiation above 350 nm. Mild sulfite treatment leads to a considerable reduction in the content of coniferaldehyde structures. After bleaching of mechanical and chemimechanical pulps with alkaline hydrogen peroxide, coniferaldehyde structures are to a large extent eliminated and they cannot be considered to be major contributor to the photo-... 

Fig. 7-3. UV absorbance (222 nm, 0.5 p,m section thickness) by various morphological regions of spruce fibers delignified to various lignin contents by the kraft and acid sulfite method (Wood and Goring, 1973). S, secondary wall P, primary wall CCP, primary wall at the cell corner.

Convert the lignin content in g/cm1 to gig by multiplying by the specific volume of the water-swollen cell wall (e.g., 1.07cinVg for spruce wood). 

I. Isolated lignin preparations. Tappi 45 826-829 Boutelje JB, Eriksson 1 (1982) A UV-microscopy study of lignin in middle lamella fragments from fibers of mechanical pulp of spruce. Sven Papperstidn 85 R39-R42 Boutelje JB, Jonsson U (1980) Ultraviolet microscope photometry of pulp fibers. UV-absorbance and its relationship to chlorine number, kapp number and lignin content. Cellul Chem Technol 14 53-67... 

Effect of Temperature on Reaction Rate. The Klason lignin contents of red spruce residue extracted by methylamlne at four different temperatures along with the predicted curves from the reaction-diffusion model are shown In Figure 2. 

Figure 1. Comparison of the extent of delignificatlon predicted by the homogeneous (first-order, second-order and third-order) models and by the reaction-diffusion kinetic model. The open circles are the measured Klason lignin contents In the residues obtained from methylamine extraction of red spruce at 276 bar, 185 C and 1 g/mln solvent flow rate.

Effect of Pressure on Reaction Rate. The variation of Klason lignin contents of red spruce residue with extraction pressure Is shown In Figure 3. Based on these data points, the rate constants at different pressures have been estimated and are given In Table III. 

J Costa e SUva, BJ Nielsen, J Rodrigues, H Pereira, and H Wellendorf. Rapid Determination of the Lignin Content in Sitka Spruce (Picea sitchensis (Bong.) Carr.) Wood by Fourier Transform Infrared Spectrometry. Holzforschung 53 597-602, 1999. 

---