Gary Furman - Academia.edu (original) (raw)

Papers by Gary Furman

The dark color of kraft lignin represents a major drawback to the kraft pulping process, since kr... more The dark color of kraft lignin represents a major drawback to the kraft pulping process, since kraft pulps must be subjected to extensive bleaching sequences for many end uses. This dark color has also hindered the use of kraft lignin as a feedstock for the production of more valuable products. Although various chromophores have been identified in kraft lignin, they have not accounted for the total color which is observed. The possible role that chargetransfer complexes play in the color development of kraft lignins was the subject of this investigation. Specifically, work was directed at determining whether charge-transfer complexes occur in kraft lignin, and, if so, what contribution they make to its color. Electronic absorption spectroscopy was employed as the major investigative tool for determining the presence of charge-transfer complexes in kraft lignin. Spectra clearly revealed the occurrence of a complex between kraft lignin and the added model quinone, 3,5-di-tert-butyl-1,2-benzoquinone. The spectral response of a periodate oxidized kraft lignin to solvent and pressure changes and derivatization (acetylation) demonstrated the likely presence of chargetransfer complexes. The periodate oxidation served to introduce ortho-quinone structures into the lignin. The determination of the quinone content of an unreacted kraft lignin by a carbon-14 labeling technique showed the presence of approximately three quinone groups per one-hundred lignin C 9 units. The calculated molar absorptivity of these quinones (528 lit/mol-cm) indicated only one-third of the absorbance decrease caused by the sodium borohydride reduction of this lignin could be accounted for by this number of quinones. The remainder of the decrease in absorbance (two-thirds) was assigned to the disruption of charge-transfer

The dark color of kraft lignin represents a major drawback to the kraft pulping process, since kr... more The dark color of kraft lignin represents a major drawback to the kraft pulping process, since kraft pulps must be subjected to extensive bleaching sequences for many end uses. This dark color has also hindered the use of kraft lignin as a feedstock for the production of more valuable products. Although various chromophores have been identified in kraft lignin, they have not accounted for the total color which is observed. The possible role that chargetransfer complexes play in the color development of kraft lignins was the subject of this investigation. Specifically, work was directed at determining whether charge-transfer complexes occur in kraft lignin, and, if so, what contribution they make to its color. Electronic absorption spectroscopy was employed as the major investigative tool for determining the presence of charge-transfer complexes in kraft lignin. Spectra clearly revealed the occurrence of a complex between kraft lignin and the added model quinone, 3,5-di-tert-butyl-1,2-benzoquinone. The spectral response of a periodate oxidized kraft lignin to solvent and pressure changes and derivatization (acetylation) demonstrated the likely presence of chargetransfer complexes. The periodate oxidation served to introduce ortho-quinone structures into the lignin. The determination of the quinone content of an unreacted kraft lignin by a carbon-14 labeling technique showed the presence of approximately three quinone groups per one-hundred lignin C 9 units. The calculated molar absorptivity of these quinones (528 lit/mol-cm) indicated only one-third of the absorbance decrease caused by the sodium borohydride reduction of this lignin could be accounted for by this number of quinones. The remainder of the decrease in absorbance (two-thirds) was assigned to the disruption of charge-transfer