Lignin-glycerol

The alkoxylation of lignin is possible in a solvent (dimethylformamide, N-methylpyrrolidone or in liquid PO [20]). A process using a lignin-glycerol mixture (3 1) in a polyether polyol based on lignin was developed [20]. The catalysts of this reaction are KOH, but a tertiary amine, such as dimethylaminoethanol is preferred. By alkoxylation with a PO-EO mixture (e.g., 18-25% ethylene oxide EO) a totally liquid dark-brown lignin-based polyether polyol with a viscosity in the range 4,700-8,000 mPa-s at 25 °C, with an hydroxyl number... 

Stevens, E.S., Willett, J.L., Shogren, R.L. Thermoplastic starch— kraft lignin—glycerol blends. J. Biobased Mat Bioen. 1(3), 351-359 (2007)... 

Hardwoods appear to have a much higher content of such aryl-glycerol-p,y-diaryl ethers because of the more restricted possibilities for condensations in the aromatic ring of sinapyl-type units owing to their two methoxyl groups. This is reflected in the greater susceptibility of hardwood lignins to mild hydrolysis (see Section I). 

Naturally lignins that have been modified by chemical reactions, e.g. condensed or sulfonated by pulping, are far less susceptible to biological decay than natural lignins, because the weak, readily hydrolyzable benzyl aryl ether bonds or the readily oxidisable benzyl alcohols of guaiacyl-glycerol units have been sulfonated or transformed by condensation reactions into strong carbon-carbon bonds. 

Fractionation by Stepwise Elution. Information obtained from the analytical separation was applied for a preparative purification. Lignin peroxidase concentrate was bound to a Q-Sepharose colunm (0= 5 cm, V = 1000 ml) after ultrafiltration and eluted stepwise with 0.08 M, 0.18 M and 0.28 M sodium acetate, pH 6.0. The fraction which was eluted with 0.28 M buffer (V= 3.91, 4400 U/1) was purified further. It was bound to Q-Sepharose and eluted with 0.18 M and 0.3 M sodium acetate. En rnie in the latter fraction was precipitated and dissolved in glycerol as previously described. The volume was 15 ml. 

Aromatic acids and aldehydes (e g, vanillic acid/vamlhn) 6 Lignin model compounds (e g, guaiacyl and veratryl glycerol fi-guaiacyl ethers, substituted phenylcoumarans and acetophenone dimers Hartley and Buchan 1979, Villeneuve et al 1982, Pecina et al 1986, Bourbonnais and Paice 1987, Pometto and Crawford 1988 Bourbonnais and Paice 1987... 

Lignin model compounds (c.g., guaiacyl-and veratryl-glycerol-/f-guaiacyl ethers, substituted phcnylcoumarans, and acetophenone dimers... 

As previously mentioned, the triglycerides found in biomass are esters of the triol, glycerol, and fatty acids (Fig. 3.6). These water-insoluble, oil-soluble esters are common in many biomass species, especially the oilseed crops, but the concentrations are small compared to those of the polysaccharides and lignins. Many saturated fatty acids have been identified as constituents of the lipids. Surprisingly, almost all the fatty acids that have been found in natural lipids are straight-chain acids containing an even number of carbon atoms. Most lipids in biomass are esters of two or three fatty acids, the most common of which are lauric (Cn), myristic (Cu), palmitic (Cia), oleic (Cis), and linoleic (Cis) acids. Palmitic acid is of widest occurrence and is the major constituent (35 to 45%) of the fatty acids of palm oil. Lauric acid is the most abundant fatty acid of palm-kemel oil (52%), coconut oil (48%), and babassu nut oil (46%). The monounsaturated oleic acid and polyunsaturated linoleic acid comprise about 90% of sunflower oil fatty acids. Linoleic acid is the dominant fatty acid in com oil (55%), soybean oil (53%), and safflower oil (75%). Saturated fatty acids of 18 or more carbon atoms are widely distributed, but are usually present in biomass only in trace amounts, except in waxes. 

Other ionization techniques were also utilized in LC/MS such as FAB, which puts the sample in a liquid matrix such as glycerol and uses fast atom bombardment as the source of energy for the ions. This technique practically does not heat the sample, allowing the formation of molecular ions for certain unstable molecules. An example of a FAB spectrum for syringoresinol detected in lignin pyrolysis is given in Figure 5.7.4. 

Support for the occurrence arylglycerol units (54) was obtained in mild hydrolysis studies of lignin [102]. According to studies of the formation of formaldehyde on periodate oxidation [103] only a few percent units with glycerol chain could be present in MWLs. The fact that arylglycerols were formed on enzymatic oxidation of p-hydroxycinnamyl alcohols provided further support for the occurrence of units of type 54 in lignins [104]. Final confirmation of this was later obtained in 2D NMR spectroscopic studies [74]. 

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