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  • 1
    Electronic Resource
    Electronic Resource
    Degradation of lignin by ozone. I. The kinetics of lignin degradation of ozone (1981)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 2053-2063 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ozonolysis of spruce periodate and cuoxam lignins and protolignin in spruce wood has been studied in 45% aqueous acetic acid at room temperature. Stirring affected the rate of reaction and a tentative explanation is given. Degradation followed first-order kinetics characterized by a rate constant K with values of 6.96 × 10-4s-1 for periodate lignin, 5.10 × 10-4s-1 for cuoxam lignin, and 5.09 × 10-4s-1 for protolignin in spruce wood. The similarity of the rate constants shows (1) that periodate and cuoxam lignins are good models for wood lignin and (2) that the carbohydrate matrix has an insignificant effect on the rate of delignification of the protolignin by ozone. The average rate of ozone consumption per C9 unit for periodate lignin was determined as 0.12 mol/min and 0.08 mol/min for cuoxam lignin. The implications of the various results are discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1981.170190817
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  • 2
    Electronic Resource
    Electronic Resource
    Degradation of lignin by ozone. II. Molecular weights and molecular weight distributions of the alkali-soluble degradation products (1981)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 2065-2078 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular weights and molecular weight distributions of the alkali-soluble degradation products from the ozonolysis of spruce periodate and cuoxam lignins and spruce protolignin have been studied by gel permeation chromatography and ultracentrifugation. The bimodal distribution previously reported for soluble lignins was found to be an artifact; the correct distribution has one broad lowmolecular-weight maximum, with a long tail extending toward the high-molecular-weight end of the distribution. Weight-average molecuar weights of the alkali-soluble degradation products, obtained by sedimentation equilibrium measurements, increased with time of ozonization up to about 15 min. Beyond this time fragmentation of the partly degraded products results in a decrease in molecular weight. Lignin degradation followed the pattern expected of a three-dimensional, infinite-network polymer gel undergoing breakdown. Based on the molecular weights and the molecular weight distributions, a random stepwise mechanism is suggested as the mode of lignin degradation by ozone.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1981.170190818
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  • 3
    Electronic Resource
    Electronic Resource
    Degradation of lignin by ozone. III. The fate of the carbohydrate matrix during the degradation of spruce protolignin by ozone (1981)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 2079-2089 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solvent-extracted spruce wood meal was ozonized in 45% aqueous acetic acid at room temperature. The ozone-treated wood meal was then extracted with dilute alkali at 65°C for 1 h. Lignin, α-cellulose, and hemicellulose content and the viscosities of the pulped wood-meal samples were measured as a function of the time of ozonization. Results indicate that although the attack on the wood components by ozone is not selective in this medium cellulose and hemicelluloses are degraded slowly compared with lignin. Lignin degraded approximately four times faster than the carbohydrates. At the fiber liberation point the pulp retained 78% of the original hemicelluloses and about 90% of the α-cellulose compared with 25% of the lignin. The pulp samples obtained during ozonization of the wood meal showed a slow decrease in the average degree of polymerization (DP); the limit reached near 350 was attributed to the inaccessibility of the ordered regions in native cellulose to ozone.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1981.170190819
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