Loureiro P.E.G.,University of Coimbra |
Fernandes A.J.S.,University of Aveiro |
Furtado F.P.,Research Institute of Forestry and Paper |
Carvalho M.G.V.S.,University of Coimbra |
Evtuguin D.V.,University of Aveiro
Journal of Raman Spectroscopy | Year: 2011
Ultraviolet-resonance Raman (UV-RR) micro-spectroscopy is an appropriate and sensitive tool to assess the chromophore structures in bleached cellulosic pulps used for papermaking. The particular selectivity in detection and identification of chromophores in pulps is achieved by acquiring the UV-RR spectra in the solid state with laser excitation at 325 nm. This wavelength corresponds to absorption of poly-unsaturated chromophore structures in partially bleached/fully bleached pulps, and linearly correlated with the signal at ca 1600 cm-1 in the UV-RR spectra. The characteristic vibrations from particular pulp chromophore structures have been assigned from experiments with model compounds, thus allowing the establishment of a UV-RR database. Among the components of bleached pulp, the xylan-lignin complex was suggested to be an important source of chromophores. The monitoring of pulp bleaching by UV-RR allowed us to suggest that it is the formation of new polysaccharide-derived chromophores upon bleaching that hinders development of further brightness and is co-responsible for the brightness reversion of fully bleached pulps. Copyright © 2011 John Wiley & Sons, Ltd.
Pinto P.C.R.,Research Institute of Forestry and Paper |
Pinto P.C.R.,University of Porto |
Sousa G.,Research Institute of Forestry and Paper |
Sousa G.,Poyry |
And 3 more authors.
ACS Sustainable Chemistry and Engineering | Year: 2013
This paper reports the extraction of Eucalyptus globulus bark and a concentration strategy to obtain a phenolic-rich extract for application in the leather tanning industry. The profiles of total phenolic compounds (TPC) and tannins contents in water and dilute alkali as a function of extraction temperature and time led to the selection of the best conditions concerning extraction yield and selectivity. The selectivity profile for TPC and tannins was established, and a maximum of 20 g per kg of bark was found, representing 2.5 g per L of extract produced. On the basis of these results, the conditions selected to produce the extract for the application envisaged in this work were: water, 140 C and 120 min. To increase the extract concentration, recirculation of the extracts over fresh bark (similar to a continuous bark extraction process) was performed and evaluated. The increment in phenolic compounds was about 4, attaining the final concentration of 8.6 g/L for TPC and 6.5 g/L for tannins. The final extracts showed leather retanning aptitude equivalent to a commercial extract of chestnut and revealed good performance in the production of leather articles like box-calf and nubuck. © 2013 American Chemical Society.
Mendes C.V.T.,University of Coimbra |
Mendes C.V.T.,Research Institute of Forestry and Paper |
Rocha J.M.S.,University of Coimbra |
Sousa G.D.A.,Research Institute of Forestry and Paper |
Carvalho M.G.V.S.,University of Coimbra
O Papel | Year: 2011
Two treatments, an induced autohydrolysis and an acid hydrolysis, were applied to Eucalyptus globulus wood chips prior to the cooking stage to extract the hemicellulosic fraction that otherwise would be dissolved in the black liquor and burnt in the recovery boiler. The obtained hydrolysates, rich in xylose, were detoxified by overliming and used for ethanolic fermentation. Impacts of each wood pretreatment on the kraft cooking process and on the quality of the produced pulp were evaluated. Both pretreatments promoted an increase in the cooking rate, but had a negative effect on pulp quality and overall yield. Autohydrolysis showed a less negative influence. However, autohydrolysates led to lower values of ethanol concentration, productivity and yield compared to the fermentation of acid hydrolysates. To get more profit from the autohydrolysates they were also submitted to secondary acid hydrolysis and vacuum evaporation processes. Overliming followed by evaporation (with a concentration factor of 3) gave better results than the inverse method. This procedure raised the fermentable sugar content and led to the production of ethanol with a concentration of ~10 geth L-1 (productivity of 0.23 geth L-1 h-1 and yield of 0.50 g eth gxyl eq -1) which compares well with the results obtained with the fermentation of acid hydrolysates.
Sousa G.D.A.,Research Institute of Forestry and Paper |
Abreu C.T.,Portucel |
Amaral J.L.,Research Institute of Forestry and Paper |
O Papel | Year: 2011
This work aimed at identifying the primary causes of paper bulk variations at an industrial paper machine by multivariate process data analysis and experimental design techniques as a tool to define production strategies that minimize bulk's variations and/or maximize bulk's objective. Process data for two different paper products of a paper mill were collected, corresponding to a two-year period. These data were used as input for a multivariate analysis, including PCA and PCR using paper bulk as a dependent variable. PCR models of paper bulk identified the most significant variables affecting it: pulp beatability, refining strategy, shoe-press operating conditions and some furnish properties. The interpretation of the main principal components suggests that paper bulk variations are most probably caused by the misalignment of refining operating conditions in the presence of pulp quality variations, which are compensated by shoe-press variables in order to assure paper machine runnability. Based upon the multivariate analysis conclusions, a preliminary laboratorial experimental design was performed involving the controlled variation, at three levels, of industrial pulp specific refining energy and pressure of a lab press. ANOVA analysis of these results revealed that bulk depends on the quadratic effect of press pressure.
Da Mota M.I.F.,University of Porto |
Pinto P.C.O.R.,University of Porto |
Novo C.C.,University of Porto |
Novo C.C.,Research Institute of Forestry and Paper |
And 8 more authors.
O Papel | Year: 2013
Eucalyptus globulus bark, one of the main by-products of the pulp and paper industry in Southern Europe, is a potential source of valuable chemicals. In this work, chemical composition of E. globulus bark was studied with detail, including its carbohydrate composition. Response surface methodology (RSM) modeling and optimization was developed for the selective extraction of polyphenolic material from E. globulus bark. The RSM method was based on the Box-Behnken design, aiming to obtain the optimal combination of extraction conditions considering the parameters ethanol percentage in the extraction medium, temperature and time. Conditions for maximum of polyphenols in the extract are 52% ethanol, extraction temperature of 82.5°C and extraction time of 264 min. The polyphenolic compounds - quantified as gallic acid equivalents - in the extract produced at the optimal conditions was 32%, corresponding to about 2% of bark weight, with a carbohydrate co-extraction of about 1.6% of bark carbohydrate content. Some of the extracts revealed low values of IC50 against human breast cancer cells, indicative of high biological activity. This work has demonstrated the potential of E. globulus bark as a source of polyphenolic compounds with anti-proliferative activity and gives a positive contribution to the increase in products portfolio diversification in pulp industry and biorefineries.