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Browsing FE - DCTP | Documentos por Auto-Depósito by Author "Duarte, Ana Paula"
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- Behaviour of two main portuguese wood species towards enzymatic hydrolysisPublication . Spiridon, Iuliana; Belgacem, Mohamed Naceur; Duarte, Ana PaulaThis paper presents the influence of cellulolytic and hemicellulolytic enzymes on the papermaking properties of pulps from Eucalyptus globulus and Pinus pinaster wood species from Portugal. It was shown that these enzymes increased the delignification efficiency and degraded the cellulose macromolecules, having effects on the fiber strength. Thus, it was found that these treatments decreased strongly the burst index, but increased significantly the tearing properties. The zero span tensile strength was also affected, especially for Eucalyptus globulus pulps. Finally, these treatments were found to increase the brightness of the treated pulps.
- Characterization of kraft lignin from Pinus pinasterPublication . Duarte, Ana Paula; Batista, Cecilia; Belgacem, Mohamed NaceurThis paper presents the results about the lignin from Pints pinaster, the only softwood used in Portuguese pulp and paper industries. Six samples of lignin were collected and studied. The first three samples were precipitated from kraft black liquors at different H-factors. using conventional batch pulping. The other three corresponded to the lignin obtained from black liquors of flow-through reactor at the same H-factors. The residual sugars from the lignin obtained were hydrolysed according to the trifluoroacetic acid method and quantified by HPLC. The main residual sugars on the lignin samples from both reactors were found to be xylose, galactose and arabinose, which indicates that the lignin-carbohydrate linkages are similar to other common softwoods. The elemental analyses of these samples showed that, in the initial stage of delignification, the HS' anions are strongly involved in the delignification mechanism. It was also shown that the C/H ratio was relatively constant, which indicated the weak participation of condensation reactions. The infrared spectra of these samples evidenced the presence of the main peaks corresponding to different functional groups of softwood lignin structure. They also showed that the content of conjugated carbonyl groups decreased with the reaction time. Finally, the permanganate potassium oxidation of the lignin samples showed the presence of the principal fragments present in softwood lignin. It was also shown that. when the time of delignification increased, the amount of non-condensed units decreased, whereas that corresponding to condensed ones increased.
- Determination of sugar content in Pinus pinaster and its corresponding hollocellulose, cellulose and kraft pulpsPublication . Duarte, Ana Paula; Gaiolas, Carla Sofia Cardona Jorge; Belgacem, Mohamed Naceur; Simões, RogérioThis paper deals with the study of the polysaccharide complex from Portuguese Pinus pinaster, as well as from its main components, i.e., holocellulose, cellulose and pulps obtained using different cooking conditions. Nordic Pinus sylvestris was also studied in order to compare it with Portuguese pine. Two methods were used: one consisted of the hydrolysis of polysaccharides with trifluoroacetic acid (TFA) and quantification of the amount of each sugar using High Performance Liquid Chromatography (HPLC). The latter approach used here consisted of the hydrolysis of the samples under scrutiny by sulphuric acid and converting it into alditols, which were then esterified before injecting to Gas Chromatography coupled with Mass Spectrometry. Myo-inositol was used as an internal standard. The results obtained by the two methods showed that the TFA procedure prevents monosaccharide degradation, comparatively with the sulphuric acid one. In fact, the overall sugar yield was found systematically higher than 93% for TFA hydrolysis, whereas that corresponding to H2SO4 treatment never exceeded 77%. The sugar composition of both pines was found very similar and the sulfidity level (from 10 to 55%) did not affect the pulp sugar composition. The glucose/mannose and xylose/arabinose ratios were found to be around 3.5 for both Portuguese and Nordic pines. Finally, kraft pulping of Pinus pinaster was found to affect drastically galactose, mannose and arabinose.
- Influence of xilanase treatment on Pinus pinaster kraft pulpPublication . Spiridon, Iuliana; Duarte, Ana Paula; Curto, JoanaIn Portugal, pulp and paper industry uses especially two wood species, Eucalyptus globules and Pinus pinaster. The second species gives pulps with low bleachability (compared with other common softwood species, like Pinus silvester), utilised for packaging papers. It is known that treatments with different hydrolytic enzymes could improve the bleaching capacity of softwood pulp. That is why, xylanases were used to improve Pinus pinaster kraft pulp characteristics. The enzymatic hydrolysis improved brightness and some papermaking properties.
- Some preliminary data on the enzymatic hydrolysis of Pinus pinaster kraft pulpPublication . Duarte, Ana Paula; Spiridon, IulianaEnzymes' applications in pulp and paper manufacturing processes and products is gaining global attention. In fact, several applications, including pitch deposits, drainage enhancement, deinking of wastepapers, pulp bleaching enhancement and modification of fibers' characteristics are already used at industrial level. Enzymes are being produced on a commercial scale and are available at a relatively low price. Research to establish the effect of enzymatic treatment continues in an effort to increase knowledge about the action of enzymes. The present paper, an additional contribution to this field, studies the potential utilization of hydrolytic enzymes to enhance the fiber characteristics derived from Pinus pinaster kraft pulp.
- The effect of wood extractives on pulp properties of maritime pine kraft pulpPublication . Baptista, Cecília; Belgacem, Mohamed Naceur; Duarte, Ana PaulaThe effect of wood extractives on pulp properties, namely the colour of the unbleached pulp and its bleaching aptitude, was evaluated by carrying out kraft cookings after extractive removal of the Pinus pinaster wood. The colour of the pulps thus obtained was compared to a reference pulp prepared without any wood extraction. Two types of wood extraction were realised. The first one consisted on using different non-swelling and swelling solvents allying upon 8 different extractions, whereas the second one was an alkaline pre-treatment of the wood chips. For the first set of extractions, acetone and ethanol-toluene appeared to be the most efficient, since the pulps obtained from wood previously extracted by these solvents showed an increase in the reflectance factor by up to 7,5% and a decrease in the kappa number of about 4 points. For the second type of pre-treatment, the results obtained showed improvements of 10% in the reflectance factor of unbleached pulp and about 12% in the kappa number. The influence of the extractives on the pulp bleachability was studied by submitting the most promising samples to a DE bleaching sequence. These pulps showed increments in the reflectance factor more than 30% higher when compared with the reference.