Lignin Modification during Eucalyptus globulus Kraft Pulping Followed by Totally Chlorine-Free Bleaching: A Two-Dimensional Nuclear Magnetic Resonance, Fourier Transform Infrared, and Pyrolysis

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• 作者：David Ibarra ; Marí ; a Isabel Chá ; vez ; Jorge Rencoret ; José ; Carlos Del Rí ; o ; Ana Gutié ; rrez ; Javier Romero ; Susana Camarero ; Marí ; a Jes&uacute ; s Martí ; nez ; Jes
• 刊名：Journal of Agricultural and Food Chemistry
• 出版年：2007
• 出版时间：May 2, 2007
• 年：2007
• 卷：55
• 期：9
• 页码：3477 - 3490
• 全文大小：1164K
• 年卷期：v.55,no.9(May 2, 2007)
• ISSN：1520-5118

文摘

Chemical modification of eucalypt lignin was investigated during kraft pulping and chlorine-freebleaching by comparing milled wood lignin, kraft lignin, and pulp enzymatic residual lignins. Thesyringyl-to-guaiacyl ratio (S/G) from analytical pyrolysis slightly changed during pulping and bleaching(S/G, 3-4) but was higher in the kraft lignin. Semiquantitative heteronuclear single quantum correlation(HSQC) nuclear magnetic resonance (NMR) showed that the relative amount of -O-4' (around80% side chains) and resinol type substructures (15%) was slightly modified during pulping and oxygendelignification. However, a decrease of resinol substructures (to only 6%) was found after alkalineperoxide bleaching. The relative amount of surviving linkages in the highly phenolic kraft lignin wasdramatically modified; resinols were predominant. Oxygen delignification did not change interunitlinkages, but a relative increase of oxidized units was found in the HSQC aromatic region, in agreementwith the small increase of pyrolysis markers with oxidized side chains. NMR heteronuclear multiplebond correlations showed that the oxidized units after oxygen delignification bore conjugated ketonegroups.