Determinação da relação siringila/guaiacila em ligninas de Eucalyptus spp. por pirólise associada à cromatografia gasosa e à espectrometria de massas

• Ano de defesa: 2007
• Autor(a) principal: Marcelo, Cristiana Resende
• Orientador(a): Lima, Claudio Ferreira
• Banca de defesa: Maltha, Célia Regina álvares , Neves, Antônio Augusto
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Agroquímica
• Departamento: Agroquímica analítica; Agroquímica inorgânica e Físico-química; Agroquímica orgânica
• País: BR
• Palavras-chave em Português: Relação siringila/guaiacila; Lignina; Pirólise; Cromatografia à gás; Espectrometria de massa
• Palavras-chave em Inglês: Syringyl/guaiacyl ratio; Lignin; Pyrolysis; Gas chromatography; Mass spectrometry
• Área do conhecimento CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ANALITICA
• Link de acesso: http://locus.ufv.br/handle/123456789/2182

Lignin is one of the main components of the wood together with cellulose and hemicellulose. Its structure is quite complex being built up by p-hydroxyphenyl (H), guaiacyl (G) and syringyl (S) units. Some studies show that the lignin structural composition may affect the pulping process. Thus, some analyses of the wood of six species of eucalyptus were done by Py-GC-MS. The samples were pyrolysed to 550 °C and 42 composts were identified from which 11 were derived from carbohydrates and 31 from lignin. The syringyl/guaiacyl (S/G) ratio was calculated based upon the area values of the recorded signals and compared to the result obtained by the alkaline nitrobenzene oxidation method. The estimative values through pyrolysis were not satisfactory for all the species, principally for Eucalyptus globulus. However, there were some improvements in the results when the guaiacol, 4-methylguaiacol, 4-vinylguaiacol, vanillin, 4-ethylsyringol, 4- vinylsyringol, homosyringaldehyde, acetosyringone and syringylacetone composts were used as lignin markers, except for E. globulus. For this particular species, it was necessary to add one more marker, the trans-4- propenylsyringol. By comparing the variability of S/G ratio in the eucalyptus species, the one which had the lowest value was E. urograndis (2,0), almost half the value found for E. globulus (4,3). The proposed methodology employing the lignin markers was useful for the establishment of S/G ratio in eucalyptus wood by Py-GC-MS for the quickness of the analysis, the consumption of small amounts of the sample and the possibility of working with the material in situ.