Hydrogenolysis of lignins

Applied Biochemistry and Biotechnology - Hydrolytic eucalyptus lignin was converted to oils by hydrogenolysis. The lignin was obtained by acid hydrolysis of eucalyptus chips from two...     

Cotton plant lignins

This paper generalizes the results of studies on lignins isolated from the stems, bolls, and seed hulls of cotton plants of a number of varieties as functions of the vegetation periods of the plants. The UV, IR and¹H and¹³C NMR spectra of the lignins have been studied. The dioxane lignin (DLA) and the natural lignins have been subjected to nitrobenzene oxidation and to cleavage with sodium in liquid nitrogen. A structure of the lignin macromolecules consisting of 18 phenylpropane structural units has been done up. Information is given on the use of lignins in agriculture, the food industry, and the paint and varnish industry. The anticorrosion and sorption properties of hydrolysis and modified hydrolysis lignins have been studied.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 40 64 75. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 465–496, July–August, 1997.     

Ammonolysis of technical lignins

The oxidative ammonolysis of hydrolysis lignin, cellolignin, and lignosulfonate takes place effectively with the greatest formation of a water-soluble fraction at 140–150°C in 2 h. On oxyammonolysis, cellolignin forms approximately twice as much water-soluble fraction as hydrolysis lignin, while lignosulfate desulfonates under conditions exceeding the optimum. The maximum amount of nitrogen in the water-soluble fraction of lignin (nitrogen-containing lignin) amounts to 9.0% for cellolignin and is 2–3% less for the others.M. V. Frunze Simferopol' State University. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 275–278, March–April, 1987.     

Electrochemical modification of lignins

The results of the electrochemical sililation, phosphorylation, and fluorination of lignin are described. Lignin is a natural polymer, a large-scale side product of the hydrolysis and pulp-and-paper industries. The electrochemical modification processes and mechanisms of some reactions are presented. Applications of electrochemically obtained lignin derivatives are considered Deceased.     

Sorption of polar components of cottonseed oil by hydrolysis lignins and modified lignins

The sorption activities of hydrolysis lignins from wood and from rice and cottonseed hulls and of modified lignins relative to the polar components of crude cottonseed oil in a nonpolar solvent have been studied.Institute of Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 414–416, May–June, 1991.     

Infra-red spectroscopic study of lignins

Infra-red spectra from 200–4000cm⁻¹ of lignin precipitated from black liquor produced from different pulping processes of bagasse, e.g. soda, kraft, sulfite, peroxyacid and butanol, have been characterized. Peroxyacid lignins are more degraded than other lignins. However, peroxyacid lignin has a higher intensity band at 1720cm⁻¹ than other types of lignins. At the same time, the aromatic ring of lignin produced from peroxyacid pulping of bagasse undergoes severe degradation. Syringyl type of lignin is predominant in all isolated lignins. Peroxyacid and butanol lignins have lower quantities of syringyl lignin shown by the lower ratio of relative absorbance of band intensity at 1500cm⁻¹ to the band at 1600cm⁻¹ than other lignins. Kraft lignin has a broad weak band at about 630cm⁻¹ that is probably due to a C---S bond. A sharp band at 655cm⁻¹, which is due to SO₃H, is characteristic of lignosulfonate, which is precipitated from black liquor produced from sulfite pulping process of bagasse. Generally, degradation of different lignins during pulping of bagasse with different processes has the following sequence: peroxyformic > peroxyacetic > butanol-water > butanol-alkali > kraft > sulfite > soda.     

Surfactant properties of kraft lignins

Formation of the adsorption layer at the solution-air interface is characterized by data on the surface tension in alkaline solutions of kraft lignins extracted from deresined spruce and birch wood. The effects of the lignin nature and solution concentration on intermolecular interaction in the surface layer are studied.     

Hydrogenolysis of rice husk lignins

The hydrogenolysis of the protolignin, the hydrolysis lignin, and the dioxane lignin of rice husks in the presence of demethylated lignin as catalyst has been studied. The breakdown of the lignins into low-molecular-mass compounds took place with yields comparable with those obtained by hydrogenolysis using other catalysts.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 611–613, July–August, 1995. Original article submitted November 21, 1994.     

Catalytic nitrobenzene oxidation of lignins

Alkaline nitrobenzene oxidation of hardwood and softwood lignins in the presence of redox and phase-transfer catalysts was studied. The selectivity of oxidation of lignins increased by 1.7 to 1.9 times. A possible mechanism of catalysis is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 3004–3007, December, 1996.     

Cross-coupling of hydroxycinnamyl aldehydes into lignins

Pathways for hydroxycinnamyl aldehyde incorporation into lignins are revealed by examining transgenic plants deficient in cinnamyl alcohol dehydrogenase, the enzyme that converts hydroxycinnamyl aldehydes to the hydroxycinnamyl alcohol lignin monomers. In such plants the aldehydes incorporate into lignins via radical coupling reactions. As diagnostically revealed by long-range (13)C-(1)H correlative NMR, sinapyl aldehyde (3, 5-dimethoxy-4-hydroxy-cinnamaldehyde) 8-O-4-cross-couples with both guaiacyl (3-methoxy-4-hydroxyphenyl-propanoid) and syringyl (3, 5-dimethoxy-4-hydroxyphenyl-propanoid) units, whereas coniferyl aldehyde cross-couples only with syringyl units.     

Analytical methodology for sulfonated lignins

There is a significant need to characterize and classify lignins and sulfonated lignins. Lignins have so far received a good deal of attention, whereas this is not true for sulfonated lignins. There is a clear demand for a better understanding of sulfonated lignins on a chemical as well as physical level. Many of the analytical methods have been developed with different goals in mind, for example, detection of sulfonated lignins in pulp‐mill effluents, elucidation of structural changes in lignosulfonates during a pulping process, or identification of properties that may affect a formulation when sulfonated lignins are used as a dispersant. When sulfonated lignins are used in industrial applications, analytical data obtained using different techniques may be necessary to enable prediction of their behavior in the target application. In the present review, a critical discussion of established and promising analytical techniques for the characterization of sulfonated lignins is presented.     

Thermal degradation of lignins isolated from wood

The lignin preparations isolated from pine and beech wood were subjected to a thermogravimetric analysis (TG). The lignin preparations were also used to obtain samples of different degrees of thermal degradation characterised by mass-losses in the interval from 10 to 60% of their initial mass. These samples were subjected to elementary analysis and the content of methoxy groups. It was observed that the content of these functional groups declined in products in which the degree of thermal degradation exceeded 30%, which corresponds to temperatures over 450°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dioxane lignins of kenaf bast and tow

Summary 1. Dioxane lignins have been isolated from the outer (bast) and inner (tow) parts of kenaf of the variety Uzbekskii 15–74, and the semiempirical formulas of the phenylpropane structural units of these dioxanes have been calculated on the basis of elementary and functional analyses.2. It has been shown by measurements of molecular-weight distribution that the DLAKK was more polydisperse than the DLALK.3. A study of the products of alkaline nitrobenzene oxidation and of decomposition by metallic sodium in liquid ammonia has shown that the DLAKK and DLALK were constructed of p-coumaryl, guaiacyl, and syringyl structural units, with the latter predominating.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 74–82, January–February, 1979.     

lignins of Allochruza paniculata and Glycyrrhiza glabra

The natural lignin of Allochruza paniculata and Glycyrrhiza glabra is studied by catalytic hydrogenolysis. Three types of lignin structural units are present: guaiacyl, syringyl, and p-coumaryl, which are characteristic of annual and perennial herbaceous plants. The structure of DLA from these plants is confirmed by UV, IR and PMR spectra.     

Oxidation of organosolv lignins in acetic acid

The oxidation of four lignins obtained by organosolv pulping of eucalyptus wood (Acetosolv-eucalyptus Acetosolv lignin [EAL]), sugarcanebagasse (Acetosolv-bagasse Acetosolv lignin [BAL] and in acetone/water/FeCl₃-bagasse acetone/water lignin [BAWL]), and a softwood mixture (Organocell, Munich, Germany) was performed to obtain vanillin, vanillic acid, and oxidized lignin. Experiments were carried out in a cetic acid under oxygen flow using HBr, cobalt(II), and manganese(II) acetates as catalysts. After 10 h the total vanillin and vanillic acid yields were BAL 0.05 mmol, EAL 0.38 mmol, BAWL 0.45 mmol, and Organ ocell 0.84 mmol. Acetosolv lignins are crosslinked, which explains the lower yields in mononuclear products. The reaction volume (Δ V) of this reaction is −817 cm³/mol, obtained in experiments performed under oxygen pressure, showing the high influence of pressure on the oxidation. The major part of the, lignin stays in solution (oxidized lignin), which was analyzed by infrared spectroscopy, showing an increased in carbonyl and hydroxyl groups in comparison with the original lignin. The oxidized lignin can be used as chelating agent in the treatment of effluents containing heavy metals.