Identificação de constituintes químicos potencialmente envolvidos na reversão de alvura de polpa Kraft branqueada pelas seqüências OZDHT (PO)D e OZ/EDP / Chemical representatives identification potentially involved in the reversion of whiteness of pulp kraft whitened by the sequences OZDHT(PO)D and OZIEDP

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

The pulp and paper section significantly contributes to the Brazilian economy. The industries produces million of tons of pulp yearly, yielding superavit of billion of dollars in the section of paper and pulp. The quality of Kraft cellulose commercialized in the international marked is evaluated, mainly because of its physical properties, anatomical characteristics and the whiteness and reversion of whiteness parameters. The chemical study detailed on the reversion of whiteness is extremely important to the industry of pulp of cellulose and paper. However, there are few study on the reversion of whiteness in Brazil, a problem that directly affects the exportation of cellulose and paper. A chemical study of the industrial pulp pre-deslignifyed with oxygen (pre-O2) was carried out in this study. This pulp was whitened in laboratory by using two sequences of whitened with ozone, a reagent with a great oxidative force. Following this, the pulps were submitted to the process of reversion of whiteness. The pulps deslignifyed with oxygen were whitened with OZDHT(PO)D and OZ/EDP, which represented process free of elementary chlorine (EFC), and the final whiteness of ISO 90% was obtained. Better results were obtained with the sequence OZDHT(PO)D, since values of whiteness and reversion of whiteness were almost the same of those obtained in the sequence OZ/EDP and with the advantage of a lower consumption of reagents. The analyses of pulps through spectroscopy in the Visible-UV didn t give significant information concerning to the process of reversion of whiteness. After each stage of whitened, sequential extracts from the pulps in dichloromethane e acetate de ethyla were obtained. Those extracts were analyzed through spectroscopic in the infrared. The noted differences between the spectra of the pulps reverted and non-reverted were more marked in the case of extracts in acetate de methyla. The extract were analyzed through the gas chromatography technique coupled to the spectrometric of mass (GC-MS), which drove to the identification of hydrocarbons, fatty acid, alcohols, steroids, carbohydrates, aromatic compounds, furanciso compounds and carboxylic acids with low molecular weight. The acid 2-furanocarboxilic, aromatic compounds derived from lignin and carboxylic acids with low molar mass were identified in the extracts of pulps reverted at the end of whitened. It is believed that they are possibly related to the process of reversion of whiteness. However, those compounds were identified in a low quantity, being not sufficient to completely explain the reversion of whiteness. The results of analyses through GC-MS suggest that oxidated compounds derived from carbohydrates and aromatics derived from lignin were linked to the carbohydrates chain or polymerized. The pyrolisys coupled to the gas chromatography and mass spectrometry (Py-GC-MS) was the technique used to ideintify the compounds which were not extracted and that, possibly, are related to the reversion of whiteness. This analyses allowed the identification of some aromatic compounds (phenols and derived) probably originating from lignin. Those results suggest that remained lignin represents a considerable part of contribution to the reversion of whiteness, and that probably was not extracted because it was linked to the carbohydrates chain or polymerized.

ASSUNTO(S)

ozone bleaching cellulose polpa de madeira wood pulp espectrometria de massa residual lignin effect efeito da lignina residual branqueamento com ozônio celulose quimica organica mass spectrometry branqueamento

ACESSO AO ARTIGO

Documentos Relacionados