Lignin elemental composition

Lignin preparation Carbohydrate content Percent of lignin Elemental composition", % C H 0 S OCH., Cl, Unit Formula... 

Its nature as a lignin component is confirmed by its elemental composition and IR-spectrum compared with corresponding data for a milled wood lignin preparation, Table I and Figure 12. 

Table I. Elemental Composition of the Water-Insoluble Lignin...

Data concerning the elemental composition and methods for isolating lignin from the wood structure, as well as the mean molar masses and distributions of the obtained fragments, are given in Table II (1,5). 

Our constitutional scheme is based on different kinds of information. The first type of information comes from an analytical study of milled spruce wood lignin prepared according to Bjorkman (3). The analytical data considered comprise the elemental composition of lignin, its content of methoxyl groups and other ether bonds, the types and amount of its different hydroxyl groups, carbonyl, and lactone groups, and the kind and number of its biphenylyl linkages and other bonds in which the benzene nucleus is involved. The work that led to data of this kind has been carried out in various laboratories and has been described previously (9,11). 

Bio-oil from rapid pyrolysis is usually a dark brown, free-flowing liquid having a distinctive smoky odor. It has significantly different physical and chemical properties compared to the liquid from slow pyrolysis processes, which is more like a tar. Bio-oils are multicomponent mixtures comprised of different size molecules derived primarily from depolymerization and fragmentation reactions of the three key biomass building blocks cellulose, hemicellulose, and lignin. Therefore, the elemental composition of biooil resembles that of biomass rather than that of petroleum oils. Basic properties of biooils are shown in Table 33.7. More detail on fuel-related characteristics is provided in the literature.571... 

Table 6.2.3. Carbohydrate content, elemental composition, and C9 unit formula of some lignin preparations... 

The total hydroxyl content of the lignin/C9 unit may also be calculated directly from the elemental composition of the acetylated lignin, i.e., % C, % H and the total O-acetyl and methoxyl contents (Freudenberg 1962). 

The observed properties of DOM are reasonably expected to be some kind of weighted average of the properties of the individual compounds of which DOM is comprised. Ideally, DOM could be studied at this level— the level of individual compounds. Practically, the mixture is too complex for this approach, so DOM is studied at the level of elemental composition and at the level of functional groups and structural subunits, the latter of which include the amino acids, sugars, and lignin-derived phenols that can be liberated from DOM by hydrolysis or oxidative degradation. 

This section of the review of DOM in freshwaters will examine its isolation by XAD resins and by membranes, the molecular weight distribution of DOM, its elemental composition, its acidic functional groups, its distribution of carbon among structural subunits, and the low-molecular-weight molecules (amino acids, sugars, and lignin-derived phenols) that are liberated from DOM by hydrolysis or oxidative degradation. For each of these subtopics, a statistical summary of published data will be presented. 

The main objective of the lEA PYRA Round Robin was to determine the interlaboratory precision and methods applied for elemental composition, water, pyrolytic lignin and main cotiqjounds. Two poplar oils were analysed by the lEA PYRA participants. It was concluded that the precision of carbon and hydrogen was very good, liquid sample handling plays a very important role in the C, H analysis, water by Karl-Fischer titration was acceptable, but should be checked carefully, and the method for the determination of pyrolytic lignin should be improved (3). 

There are two major chemical components in wood lignin (18-35%) and carbohydrate (65-75%). Both are complex, polymeric materials. Minor amounts of extraneous materials, mostly in the form of organic extractives and inorganic minerals (ash), are also present in wood (usually 4-10%). Overall, wood has an elemental composition of about 50% carbon, 6% hydrogen, 44% oxygen, and trace amounts of several metal ions. 

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