- Photocatalytic degradation of lignin and lignin models, using titanium dioxide: The role of the hydroxyl radical
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The role of hydroxyl radicals on the degradation of lignins during a cellulosic pulp bleaching process including a photocatalytic stage, was assessed using peroxyformic acid lignins EL1 and REL1 and two phenolic biphenyl lignin models 1 and 2. The irradiations were performed in the absence of photocatalyst TiO2 and H2O2 (condition a), in the presence of TiO2 (condition b) and in the presence of H2O2 (condition c). The experiments were conducted in alkaline (pH? 11) aqueous ethanol solutions with oxygen bubbling. The relative phenolic content of the irradiated solutions, which is indicative of the involvement of hydroxyl radicals, was determined by ionization absorption spectroscopy. The results obtained show that the catalyzed reaction involves both degradation of the phenolate groups by electron transfer and hydroxylation of the lignin aromatic structure. Benzyl alcohol structural elements in sodium borohydride reduced lignin REL1 and compound 2 were also found as good trapping agents for the hydroxyl radicals. The degradation of EL1 was studied by measuring its fluorescence emission by comparison to the fluorescence of compound 2. The emission spectra indicate that some biphenyl phenolate anions in EL1 are reacting under UV/visible irradiation and some others, probably polyphenolic chromophores emitting less fluorescence, are formed.
- MacHado, Antonio E.H.,Furuyama, Aline M.,Falone, Sandra Z.,Ruggiero, Reinaldo,Perez, Denilson Da Silva,Castellan, Alain
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- MULTISTAGE FRACTIONATION PROCESS FOR RECALCITRANT C5 OLIGOSACCHARIDES
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Methods are disclosed for increasing the level of C5 monosaccharides produced from lignocellulosic biomass using a multistage fractionation process to handle recalcitrant C5 oligosaccharides without producing unwanted degradation products. Methods for reducing C5 monosaccharides degradation products produced from lignocellulosic biomass are also disclosed. In addition, compositions and products produced by the methods are disclosed.
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