Lignin from coals

The addition of anthraquinone (a chemical catalyst produced from coal tar) to the pulping liquor has been shown to speed up the kraft pulping reaction and increase yield by protecting cellulose fibers from degradation. The anthraquinone accelerates the fragmentation of lignin, allowing it to be... 

Dynaphen A process for converting mixed alkyl phenols (from coal liquids or lignin) to benzene, phenol, and fuel gas, by noncatalytic hydrogenation at high temperature. Developed and offered by Hydrocaibon Research. 

The chemical reactions that accompany the extraction of volatiles (1) from hydrocarbon resources are frequently obscured by the complexities of the reaction system. In contrast, the comparative simplicity of model compound structures and product spectra permit resolution of reaction fundamentals 2) and subsequent inference of the factors that control real reacting systems. Herein is described the use of model compounds to probe the kinetics of pyrolysis and solvolysis reactions that likely occur during the extraction of volatiles from coals and lignins. 

Flash pyrolysis in FFR is a usefnl means to remove snlphnr from coal [19, 21]. As shown by Li et al. [22], it can also be ntilized to remove heteroatom molecules from biomass. Both the yield and the composition of the resnltant gas depend on the biomass composition. The gas ontpnt is richer in hydrogen in the case of cellulose and hemicel-Inlose than in the case of lignin. Smaller biomass particle sizes and higher fast pyrolysis temperatnres also boost hydrogen content. The total of carbon monoxide and hydrogen content is reported to be 65.4% for legnme straw and 55.7% for apricot stone. 

Gasification is seen as a key pathway towards hydrogen when starting from coal or lignin-containing biomass (wood, wood scrap or other solid-structure plant material). The gasification takes place by heating with steam ... 

The structures of the lignins are amenable to conversion to several classes of substituted phenols by thermochemical and thermal degradation methods. The displacement of pyroligneous tars by coal tars eliminated much of the demand that existed for the lignin-based products. Creosote oil or cresylic acid, a mixture of o-, m-, and p-cresols, is now manufactured mainly from coal tars, while only small amounts of cresols are made from wood tars. The use of wood tars and other biomass-derived tars as substitutes for a major portion of the phenol and formaldehyde in phenol-formaldehyde resins could reverse this trend (Himmelblau, 1995). The key to this process seems to be that the... 

As was noted early, under the action of polyethylene the conversion of pine wood was increased by 1,4 times. After removing 11% wt, of lignin from pine wood by extraction with dimethyl sulfoxide this effect was less (1.2 times). In the runs with cellulose / polyethylene mixtures no positive influence of polyethylene on pine wood conversion was defected. The maximum increase of the conversion degree (1.5 times) was observed for coal / polyethylene mixture. 

In general, commonly used oxidants destroy phenolic rings or give complex products (25, 26). Some of the oxidants such as nitrobenzene produce reaction byproducts that may interfere with the analysis of the oxidation products (23, 27, 28). To obtain lignin oxidation products from coals, we resorted to the alkaline cupric oxide oxidation method which has been applied successfully to analysis of lignins in plants (23), fulvic and humic acids (24, 27), and land-derived marine sediments (23). 

Soil is extremely rich in bacteria (10 —10 cells per g soil), which survive by utilizing nutrients and carbon sources present there. Naturally occurring aromatic compounds are present in soil from the breakdown of lignin from woody plants and phenylpropanoids found in plants the aromatic fraction of leached oil and coal as well as the aromatic amino acids L-phenylalanine, L-tyrosine, and L-tryptophan from protein breakdown (Figure 1). Man-made aromatic compounds include pesticides, detergents, oils, solvents, paints, and explosives. 

Molecules of lignin and its primary breakdown products, which are the most important coal precursors, are now generally considered to be based on phenyl-propylene units, derivatives of which have been obtained from coal by oxidizing it with performic acid (41-43). 

The interesting aspect of one of these examples (Figure 3.20) is the inclusion of carbon dioxide within the cycle. Both postulates recognize the production of carbon dioxide from coal, thereby pointing out the relationship of carbon dioxide and coal but recognition of carbon dioxide as part of the natural cycle between plants, lignin, humus, and coal underscores the closeness of the relationship and the end product of the environmental aspects of coal use. 

The fuel properties of wood can be summarized by ultimate and proximate analyses and deterrnination of heating value. The analytical procedures are the same as those for coal, but with some modifications. Analytical results generally vary about as much within a species as they do between species, except that softwood species generally have a higher carbon content and higher heating values than hardwood species because of the presence of more lignin and resinous materials in softwood species (see Fuels from waste). 

Supercritical fluid solvents have been tested for reactive extractions of liquid and gaseous fuels from heavy oils, coal, oil shale, and biomass. In some cases the solvent participates in the reactions, as in the hydrolysis of coal and heavy oils with water. Related applications include conversion of cellulose to glucose in water, dehgnincation of wood with ammonia, and liquefaction of lignin in water. 

Most electricity from biofuels is generated by direct combustion. Wood fuels are burned in stoker boilers, and mill waste lignin is combusted in special burners. Plants are generally small, being less than 50 MW in capacity. There is considerable interest in combustion of biomass in a process called cofiring, when biomass is added to traditional fuels for electricity production. Cofiring is usually done by adding biomass to coal, but biomass also can be cofired with... 

Certain compositional differences between coals of differing origins can be inferred from available data. Differing anatomical distributions of cellulose, lignin and suberin, with implications for the origins of vitrinites, and differing distribution of phenolic substances in plants of different orders and families, have been referred to above. Some biochemical investigations of modern representatives of ancient plants have been made (e.g., refs. 14,... 

Wondrack, L. Szanto, M., and Wood, W. A., Depolymerization of Water-Soluble Coal Polymer from Subbituminous Coal and Lignite by Lignin Peroxidase. Applied Biochemistry and Biotechnology, 1989. 20-1 pp. 765-780. 

M. J. Wornat, E. B. Ledesma, and N. D. Marsh, PolycycUc aromatic hydrocarbons from the pyrolysis of catechol (ordio-dihydroxybenzene), a model fuel representative of entities in tobacco, coal, and lignin, Fuel 80,1711-1726 (2001). 

Lignin-derived compounds have been observed in pyrolysis products of low rank coals and associate woody tissue FI- 61. Mycke and Michaelis [2] isolated lignin-derived methoxyphenols from a Miocene coal by catalytic hydrogenolysis. Sigleo [S] reported the presence of phenolic compounds derived from iteration of lignin in pyrolysis products of silicified woody tissue as old as Triassic age. However,... 

In an attempt to delineate the degree of preservation of lignin in pre-Tertiary coal, we examined numerous coalified wood samples ranging in age from Carboniferous to Cretaceous. The samples were initially screened by solid-state l C nuclear magnetic resonance to detect the possible presence of methoxyl carbon. Once such carbons were detected, the samples were subjected to analytical pyrolysis to determine the relative yields of methoxyphenols which would provide an indication of the state of preservation of the lignin-derived structu units. We report here on the identification of lignin-derived methoxyphenols in the coalified wood samples selected for analytical pyrolysis. 

The phenol, the cresol isomers, and the dimethylphenols, major pyrolysis products in e Moscow wood sample, are probably also derived frt>m lignin precursors that have been altered through coalification reactions. Hatcher [fr] have shown that an increase is observed in the relative proportion of phenols and cresols as rank of coaHfred wood samples increases to subbituminous coal. Comparing the distribution of pyrolysis products from the Moscow wood to that of other coalified wood samples of Hatcher allows us to deduce that the... 

Scholz, C. and Gross, R. 2000. Polymers from Renewable Resources. ACS, Washington, DC. Steinbuchel, A. 2001. Lignin, Humic, and Coal. Wiley, New York. 

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