Lignin, ozone

Dorland et al (1939) used 95% formic acid in water and Miura et al (1985) 50% formic acid in dichloromethane as reaction media In the latter study, the results were not strikingly different from those obtained using acetic or propanoic acids in parallel experiments, even though formic acid is known to be consumed by ozone in dilute aqueous perchloric acid This finding is also consistent with the appearance of formic acid as a lignin ozonation product Bonnet et al (1989) found that up to 36% of the total acidity that developed on ozonation of alkali lignin in water was due to the presence of formic acid... 

In most lignin ozonation studies, residual ozone is purged from the system by a stream of nitrogen. Ozonides and ozone-generated peroxides can survive in the crude product mixture for several days (Kolsaker and Bailey 1967, Soteland 1971). Conversion of the ozonation products to stable, more easily identifiable products can be achieved by further oxidation, reduction, acid- or base-induced decomposition, or some combination of such methods. 

Lignin ozonation products contain some diacids that occur in nonesterified, partially esterified, and fully esterified forms (typically methyl esters derived from cleavage of the methoxylated aromatic rings). Bonnet et al. (1989) chose to esterify the free carboxyl groups by use of diazomethane to simplify the... 

Keywords Concrete form, dry process defibrator, lignin, ozone treatment, tropical rainforest, wastepaper. 

A technique based on ozonation, in contrast, provides information on the stmcture of the lignin side chain by degrading the aromatic rings (33). Thus the side chain of the dominant stmcture ia all native lignins, the arylglycerol—P-aryl ether moiety, can be obtained ia the form of erythronic and threonic acids. Ozonation proves to be an elegant method for determination of the stereospecificity ia lignin. 

The aromatic ring of a phenoxy anion is the site of electrophilic addition, eg, in methylolation with formaldehyde (qv). The phenoxy anion is highly reactive to many oxidants such as oxygen, hydrogen peroxide, ozone, and peroxyacetic acid. Many of the chemical modification reactions of lignin utilizing its aromatic and phenoHc nature have been reviewed elsewhere (53). 

Many of the chemical reactions used to modify lignosulfonates are also used to modify kraft lignins. These include ozonation, alkaline—air oxidation, condensation with formaldehyde and carboxylation with chloroacetic acid (100), and epoxysuccinate (101). In addition, cationic kraft lignins can be prepared by reaction with glycidjiamine (102). 

Phenols. The first stable ozone oxidation product of phenol in water is ds ds-raucomc acid, which requires - 2 mol O /mol phenol. In practice, larger dosage levels of ozone are required because other ozone-reactive substances are present in most wastes. Ozone oxidation of phenoHc effluents is employed in paper mills, coke mills, oil refineries, and thermoplastic resin manufacture, producing effluents that are safe to freshwater biota (122,123) (see Lignin Pulp). 

Akiyama, T. Magara, K. Matsumoto, Y. Meshitsuka, G. Ishizu, A. Lundquist, K. Proof of the presence of racemic forms of arylglycerol-p-aryl ether structure in lignin studies on the stereo structure of lignin by ozonation. J. Wood Sci. 2000, 46, 414-4-15. 

Miksche, G. E. Lignin reactions in alkaline pulping processes (rate processes in soda pulping). In Chemistry of Delignification with Oxygen, Ozone, and Peroxides Nakano, J. Singh, R. P.,Eds. Uni Publishers Co Tokyo, Japan, 1980 pp. 107-120. 

Akiyama, T. Sugimoto, T. Matsumoto, Y. Meshitsuka, G. Erythrolthreo ratio of [i-O-4 structures as an important structural characteristic of lignin. I improvement of ozonation method for the quantitative analysis of lignin side-chain structure. J. Wood Sci. 2002, 48, 210-215. 

Matsumoto, Y. Ishizu, A. Nakano, J. Studies on chemical structure of lignin by ozonation. Holzforschung 1986, 40, 81-85. 

Lignosulfonates have recently been tried as a filler for rubber but are slightly less efficient than carbon black, the cheap conventional filler with which it must compete. However, it is conceivable that lignin could increase the stability of rubber to ozone, the natural reagent which causes vulcanized rubber to "perish. ... 

Dence, C. W. In Reactions of Hydrogen Peroxide with Lignin Current Status in Chemistry of Delignification with Oxygen, Ozone and Perox-... 

Ozonization of lignin forms derivatives of muconic acid that have the unique chemical structure of conjugated double bonds with two carboxyl groups. These derivatives have great potential for chemical modification. The ozonized lignin of white birch was soluble in epoxy resin at 120°C, and the free carboxyl groups were found to react with epoxide. This paper discusses developmental work on the preparation of pre-reacted ozonized lignin/epoxy resins the dynamic mechanical properties of cured resins and preliminary results of the application of these resins as wood adhesives. 

Ozone has recently become industrially available at low cost. From the point of view of the development of complete wood utilization, the pretreatment of wood with ozone enhances the yield of glucose by enzymatic saccharification. Ozonized lignin is thereby obtained as a by-product. 

The lignin isolated from white birch after steaming was ozonized. The ozonized lignin was soluble in epoxy resins at 120°C. It was also found that free carboxyl groups (introduced by ozonization) react with epoxide only by heating. Previous developmental work on the blending of lignin with epoxy resin has been reported by Ball and his co-workers (3). They synthesized... 

Isolation and Ozonization of Lignin. The wood meal of white birch (Be-tula papyrifera Marsh.) was steamed for 15 min at 180°C, and extracted with water at 60°C, followed by extraction with methanol as shown in Figure 2. The methanol-soluble part was dried under vacuum after removal of methanol. The yield of methanol extract was 75% based on the amount of lignin present in the original wood. 

The lignin (50 g) was dissolved in a mixture of dioxane (500 ml) and methanol (1,000 ml), and ozonized at 0°C with an oxygen flow rate of 0.5 ml/min and ozone concentration of 3% as shown in Figure 3. After treatment with ozone, the solution was treated with an excess amount of ether, and the insoluble fraction was filtered off, followed by drying under vacuum. Three samples (No. 1, No. 2, and No. 3) differed in the extent of ozone treatment as shown in Table I. The molar equivalents were based on the ratio of ozone to each phenylpropane (C9) unit. The yield of each sample is also shown in Table I. 

Gel Permeation Chromatography. Each ozonized lignin was analyzed by liquid chromatograph (ALC/GPC 201 with R-401 Differential Refractome-ter Water-Associates). Columns and solvent conditions were as follows p-Styragel 1,000, 500, 500,100A in series and tetrahydrofuran at 2.0 ml/min. Molecular weight was estimated by use of polystyrene standards. 

Preparation of Ozonized Lignin/Epoxy Resins. Each ozonized lignin (1.0 g) was mixed with DGEBA and heated at 120°C with stirring as described in the previous section. After heating for 30 min, the mixture was cooled to room temperature. The solidified reactants were dissolved in acetone (2 ml) and the curing reagents, diethylenetriamine (DETA) or hexamethylenedi-amine (HMDA), were added at 90% of the stoichiometric amount to epoxy equivalent. 

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