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|Type:||Artigo de periódico|
|Title:||Pyrolysis-gas Chromatography Of The Macromolecular Fractions Of Oxidized Organocell Lignins|
|Abstract:||Spruce Organocell lignin has been oxidized by O2 under pressure in acetic acid and in the presence of NaBr or NH4Br and Co(OAc)2 as catalyst in order to obtain chelating agents. The reaction time, O2 pressure, and the Co(OAc)2/bromide ratios were varied and the product quality was monitored by analytical pyrolysis-gas chromatography. The main pyrolysis products were phenol, guaiacol, 4-methyl-and 4-ethylguaiacol, catechol, isoeugenol, vanillin, and vanillic acid. In the oxidized lignins the moiety of demethoxylated, demethylated and oxidized guaiacyl units was increased. Vanillin and vanillic acid were used as marker for determination of the oxidation increments. The longer the reaction time and the more bromide as promoter was used the higher oxidation increments between 2 and 9 were observed. The oxidation increments correlate with the severity of oxidation. The yield of degradation products with low molecular weight was low. Bromides promote mainly the oxidation and not the depolymerisation of lignins. © 1997 Published by Elsevier Science B.V.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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