Lignin lignocellulose

Wood, textiles and paper consist of lignocellulose, which is a polymer blend of cellulose and lignin. Lignocellulosic products are more or less rapidly photo-degraded on exposure to sunlight or outdoor conditions, i.e. weathering. 

Figure 2. Mineralization of C[Lignin]-Lignocellulose (closed circles) and C[Polysaccharide]-Lignocellulose (open circles) From S, alterniflora In Salt Marsh Water and Sediment.

Figure 3. Semi-Log Plot of Mineralization of 14C[Lignin]-Lignocellulose from S, alterniflora. The line represents the best fit to a negative exponential equation. 

Fibers for commercial and domestic use are broadly classified as natural or synthetic. The natural fibers are vegetable, animal, or mineral ia origin. Vegetable fibers, as the name implies, are derived from plants. The principal chemical component ia plants is cellulose, and therefore they are also referred to as ceUulosic fibers. The fibers are usually bound by a natural phenoHc polymer, lignin, which also is frequentiy present ia the cell wall of the fiber thus vegetable fibers are also often referred to as lignocellulosic fibers, except for cotton which does not contain lignin. 

Lu and Pizzi [83] showed that lignocellulosic substrates have a distinct influence on the hardening behavior of PF-resins, whereby the activation energy of the hardening process is much lower than for the resin alone [84]. The reason is a catalytic activation of the PF-condensation by carbohydrates like crystalline and amorphous cellulose and hemicellulose. Covalent bonding between the PF-resin and the wood, especially lignin, does not play any role [84]. 

Holzfaser, /. wood fiber, ligneous fiber wood pulp = Holzfaserstoff. -papier, n. wood-pulp paper, -stoff, m. lignin cellulose lignocellulose. 

Lignocellulose is the fibrous material that forms the cell wall of a plants architecture . It consists of three major components (Fig. 2.1) cellulose, hemicellulose and lignin [3, 14-16]. It contrasts with the green parts of the plants and the seeds, which are rich in proteins, starch and/or oil. 

Alternatively, lignocellulose can also be hydrolyzed to liberate the lignin and de-polymerize the polysaccharides to sugars. The sugars can subsequently be converted into various fuel and chemical components via chemical or biological routes. 

Various processes have been developed for hydrolyzing lignocellulose to its major constituents, i.e., to sugars and (partly) depolymerized lignin. The lignin is usually precipitated from the aqueous solution and either used as chemical feedstock or burned as process fuel. The aqueous sugar solution is then applied for fermentation to ethanol after neutralization and purification. 

Various solvents are being investigated to dissolve lignocellulosic materials. Some approaches focus on the selective depolymerization and extraction of lignin and hemicellulose as pre-treatment to produce clean cellulose fibers for subsequent fermentation or for pulping. Other approaches attempt to dissolve the whole lignocellulose with or without depolymerization. The liquefaction processes that are carried out at high temperature (>300 °C), and produce a complex oil mixture, are discussed above with the pyrolysis processes. 

Lignocellulose biomass is a mixture of phenolic lignin and carbohydrates -cellulose and hemi-cellulose. It grows abundantly on earth and is largely available as agricultural and forestry residues. Lignocellulose can be converted via four major routes pyrolysis, gasification, hydrolysis and fermentation. 

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