A wide array of both commodity and specialty chemicals can be derived from wood, either as a primary product or by-product of another process. The technologies in which chemicals are the primary products include thermal degradation, hydrolysis/ fermentation, direct collection, and extraction methods. Chemicals collected as by-products generally come from ï¬ber-producing processes, including pulp and paper and steam explosion. While cellulose, lignin, and derivatives thereof could be classiï¬ed as chemicals derived from wood, the current review will be limited to low-molecular-weight chemicals from wood. The synthesis and utilization of various chemicals from renewable resources have received considerable recent attention through research efforts in green chemistry. Perhaps the oldest of the chemicals produced from wood are those derived from the extractives. The term 'naval stores' provides a clue to the water-prooï¬ng applications for which these chemicals were originally used. The extractives can broadly be divided into terpenes, resin acids, and fatty acids.
[...] Natural rubber (cis-1, 4-polyisoprene) comes from Hevea brasiliensis, and is still collected by tapping living trees and collecting the latex sap. Resin Acids The resin acids, the main components of rosin, are diterpenoids such as abietic acid, neoabietic acid, palustric acid, pimaric acid, and isopimaric acid. Rosins can be isolated from directly collected oleoresins, but are now more commonly separated from tall oil as a by-product of the kraft, black liquor recovery process. Metallic salts and esters of resin acids are used as additives to printing inks to improve gloss, mechanical stability and resistance to chemicals. [...]
[...] Thermal Degradation The production of chemicals from wood by the action of heat includes a broad continuum of processes, varying with respect to conditions and products. In general, these methods are done in the absence of air or other oxidizing agents, such that the substrate is thermally degraded, rather than combusted. The general terms used to describe this process include pyrolysis, liquefaction, and gasification, the latter two selectively producing liquid and gas, respectively, while pyrolysis results in a mixture of all three, the relative amounts of which are a function of the conditions. [...]
[...] Pharmaceuticals The extractives from wood and bark have had both a long history and recent success with respect to the isolation of important drugs. Perhaps the oldest and best known of these applications is the alkaloid quinine, present in the bark of Cinchona calisaya, C. cussiruba, C. legeriana,and C. officinalis. These trees are native to the Andes and the bark may contain up to 15% quinine. Natives of South America used the bark as medicinal, but it appears that Jesuit missionaries first found that the powdered bark had antimalarial properties. [...]
[...] The energy content can range from 100–300 Btu/SCF (standard cubic foot) in processes that utilize direct contact of the wood with air (due to dilution), 300–700 Btu/ SCF when oxygen is used, and 700–1000 Btu/SCF when conditions favor the formation of light hydro- carbons such as methane (which is responsible for a large proportion of the energy). SUMMARY A wide array of both commodity and specialty chemicals can be derived from wood, either as a primary product or by-product of another process. [...]
[...] Several species of Tabebuia (Pau d'Arco), from the rainforests of Central and South America, have been examined as a source of the compound lapachol that has been reported to be effective against some tumor cells. Severe toxicity problems have been reported, however, and to date this compound is not used in cancer therapies. Polysaccharides In addition to extractives, polysaccharides have been examined as possible therapeutic agents. A methylglucuronoxylan has been isolated from Fagus crenata and tested in mice. Cancers in the peritoneal cavity were suppressed, as were the growth rates of tumors. [...]
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