Lignin modification

The chemical and technological aspects of lignin modification and utilization are discussed. Competition with petrochemicals does not, for a number of reasons, permit the commercial utilization of non-oil based products made from lignin. However, pressure from governments and the public for a cleaner environment and new pulping processes (organosolv processes) may inevitably result in full scale industrial use of lignin other than fuel within the not too distant future. 

It is evident from the above discussion that lignin is still a material of the future in the areas of structural plastics and as a source of chemicals. However, the ever-increasing demand for a clean environment hastens the day when lignin is used on a large industrial scale. This day is much nearer than was predicted only a few years ago. From this point of view, it is evident that research should continue and more funds should be allocated to research work on lignin modification. 

This paper presents two different directions of lignin modification research ... 

The lignin modifications in solid (C) were carried out using lignins (1.0 g) mixed with corresponding amounts of hydrogen chloride acceptor and chlorophosphazenes. The reaction was carried out by heating at a temperature of 100°C, i.e., above the melting point of chlorophosphazene. The reaction mixture was poured into ice water, and then the solid product was purified as described before (9). 

Lignin modification with chlorophosphazenes is an example of how this renewable resource may be utilized in special polymeric materials. 

Another potential lignin modification method concerns the reaction with difunctional acid chlorides, especially terephthaloyl chloride, to form cross-linked polymeric materials (1,10,14,20). Several studies have dealt with... 

Anterola, A. M., and Lewis, N. G., 2002, Trends in lignin modification a compehensive analysis of the effects of genetic manipulations/ mutations on lignification and vascular integrity, Phytochem. 61 221-294. 

Chen F, Dixon RA. 2007. Lignin modification improves fermentable sugar yields for biofuel production. Nature Biotech 25 759-761. 

Apart from hemicellulose and cellulose, lignin is also a promising raw material for various applications. Huttermann et al. (2001) described various potential technologies for lignin modification for the production of new compounded materials. Pan et al. (2005) demonstrated that lignin extracted during ethanol organosolv... 

The developments represented by these studies now permit the facile analysis, identification, and quantification of constituents of the type described above in plant extracts, and the associated methods may also be used to help define reaction pathways and conditions for both delignification and lignin modification. To illustrate the utility of HPLC, selected examples will be discussed, as appropriate, in the accompanying text chosen examples simply reflect the author s interests and should not be misconstrued as being comprehensive. 

Choice of the Lignin Modification Reaction. The phenolysis reaction was selected as a means of modifying the structure and reactivity of the ammonium lignin sulfonate for three main practical reasons. First, because this lignin derivative is soluble in (and will ultimately be used in conjunction with) liquid phenol itself second, because unreacted phenol, unlike other reaction solvents, would not have to be removed from the phenolated product after reaction and before conversion to the adhesive resin and third, because lignins and carbohydrates are known to react with phenols under acidic conditions (6,7). 

Capraru A.M. Disertation thesis Contributions on lignin modification by hydroxymethylation and epoxydation reactions GH. Asachi Technical University, Iasi, Romania, (2010)... 

A large number of lab scale, lignin modifications were... 

Thielemans, W., Wool, R. P. (2005). Lignin esters for use in unsaturated thermosets Lignin modification and solubility modeling., (4), 1895-1905. 

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