Lignin numbering system

Fig. 2.30 A partial, random, structure of beechwood lignin, illustrating the types of condensation linkages present (after Nimz 1974 Me = CH3), together with unit names and C numbering system.

Figure 9.2 (a) Numbering system in monolignols. (b) Types of monolignols found as building blocks in lignin. 

The sulfonated lignin products function primarily as dispersants in aqueous systems and help to form stable dispersions of a number of insoluble materials. For example, lignin dispersants find use in pigments, carbon black, gypsum, ceramics, coal slurry and water treatment systems to mention some of the more prominent applications. 

Alkali lignin was fused with caustic in the presence of sodium sulfide (/, 2) a number of times. Several compounds such as protocatechuic, vanillic, p-hydroxybenzoic, and oxalic acids were obtained, but the degradation of the alkali lignin was relatively low. Alkali fusion in nonaqueous systems 4y 20) also gave only small amounts of desirable products, and most of the starting lignin was recovered undegraded. 

An example of cometabolism of pollutants is provided by the white rot fungus Phanerochaete chrysosporium, which degrades a number of kinds of organochlorine compounds, including DDT, PCBs, and chlorodioxins, under the appropriate conditions. The enzyme system responsible for this degradation is one that the fungus uses to break down lignin in plant material under normal conditions. 

Fig. 4.1.8. Triangular coordinate system displaying the three types of lignin (C, GS, and HGS) in realtion to the composition of the lignins (H, G, and S units expressed as mol % and the methoxyl contents as the number/100 phenylpropane units). According to Faix 1991...

The influence of the solvent system employed on the extent of aromatic adsorption has been studied by a number of authors. Thus, it has been demonstrated that chloroform negates the effects of aromatic adsorption on LH-20 [188, 189] and Carnegie [190] was able to determine the molecular weights or aromatic amino acids on G-25 in phenol-acetic acid-water (1 1 1 w/v/v). Similarly, dioxane-water (1 1) greatly diminishes or eliminates the adsorption of lignin degradation products to G-25 and LH-20 [191]. 

Analysis of reprecipitated xylan on fibres from kraft pulping of hardwoods by modern methods indicated that the model system of 20 years earlier had been very perceptive both hexeneuronic acid residues and p-L-iduronyl residues were found (The finding caused a stir in the pulp industry, since a KMn04 titre ( kappa number ) had been used traditionally as measure of the residual lignin in the pulp, but in hardwood pulps these titres were too high, by factors of <2, because of the reaction of permanganate with the hexeneuronic acids" ). 

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