Eucalyptus Globulus Pulp Research Articles

Predicting bleachability of Eucalyptus mechanical pulp by moisture content-dependent near-infrared spectroscopy

As the main raw materials in the pulp and paper industry, Eucalyptus wood has different bleachability due to the variety of species. In this study, moisture content-dependent near-infrared (NIR) spectroscopy was developed to predict the bleachability of two different Eucalyptus mechanical pulp from Eucalyptus globulus (EG) and Eucalyptus urophylla (EU). Two-dimensional (2D) correlation analysis was applied to explain the distinctive spectral change of EG and EU mechanical pulps under moisture content perturbation, the susceptible extent and sequential order of spectral changes were displayed in the synchronous and asynchronous maps, respectively. In the synchronous map of EU pulp, the spectral intensity at 1685 nm related to lignin changed significantly with moisture content, and the spectral change at 1432 nm related to cellulose was stronger than that at 1373 nm related to holocellulose, while the opposite behaviors were observed in the synchronous map of EG pulp. Meanwhile, the two Eucalyptus species had different sequential orders of spectral change occurring at the lignin-related band (1164 nm) and carbohydrate-related bands (1432 nm and 1590 nm) in the asynchronous maps. Then the correlation between moisture content-dependent spectral features and bleachability of pulps was confirmed by principal component analysis (PCA). Finally, a radial basis function neural network (RBFNN) predictive model was built using moisture content-dependent spectral features to describe the brightness response of Eucalyptus mechanical pulp under different bleaching conditions and exhibited excellent prediction accuracy and generalization performance. Therefore, moisture content-dependent NIR spectroscopy may be a promising technique for predicting the bleachability of raw material in pulping and papermaking processes.

Utilization of genetic algorithms to optimize Eucalyptus globulus pulp yield models based on NIR spectra

An optimization problem was developed by using a genetic algorithm to select wavelengths for establishing multivariate calibration models based on partial least squares (PLS) regression. Two near infrared (NIR) data sets represented by untreated and second derivative spectra were used to predict Eucalyptus globulus pulp yield. The optimization process was run with the number of variables (i.e., wavelengths) varied from 10 to 100 to determine the optimum wavelengths and number of latent variables for PLS regression model. A linear function of R-squares for calibration and prediction sets was utilized as the objective function of the optimization problem. The optimum wavelengths selected by genetic algorithm helped to considerably improve the performance of the PLS regression model, not only for the calibration sets but also for the prediction sets. The optimum number of latent variables varied over a wide range, from the maximum allowed (20) to a lower limit of six. Representative wavelengths for each data set were also statistically determined and assigned to corresponding wood components through a band assignment process, which showed strong agreement.

Effect of microwave-involved ClO2 bleaching on the characteristics of lipophilic extractives of bleached Eucalyptus globulus pulps

The preparation of bleached pulp from Eucalyptus globulus pulp was evaluated after utilizing chlorine dioxide (ClO2) with or without microwave irradiation. The three ClO2-bleaching processes examined were water-bath heating; microwave heating; and microwave pretreatment combined with water-bath heating. These processes were applied to eucalypt pulps that were oxygen-delignified. The effects of the treatments on the levels of lipophilic extractives and properties of the resulting pulps were compared with one another. The microwave-induced treatment had a remarkable effect, leading to an increase in pulp brightness and a decrease in lipophilic extractives when compared with the control (i.e., A). The sample under the condition of microwave pretreatment combined with water-bath heating achieved a higher brightness and reduced lipophilic extractives, which were increased by 45.8% and reduced by 37.4%, respectively. This study demonstrated an effective microwave-pretreated method in ClO2 bleaching process, which provides a promising route for alleviating pitch deposition problems occurring during pulp manufacture.

Enzymatic treatment applied as a final stage in E. globulus kraft pulp bleaching

AbstractBACKGROUNDBrightness stability of bleached chemical pulps is often associated with the final bleaching stages that should provide the removal of chromogenic species responsible for brightness reversion without compromising the papermaking potential. Aiming at promoting higher brightness stability, a partially bleached Eucalyptus globulus pulp (DED) of c. 88% ISO brightness was involved in a study of a final enzymatic stage (X) alternative to conventional chlorine dioxide (D) and hydrogen peroxide (P) bleaching stages (DEDX vs. DEDD and DEDX vs. DEDP). X stage was also applied before and after the final P or D stages (DEDDX/DEDXD and DEDPX/DEDXP) to produce high brightness pulps (c. 91%).RESULTSX stage with xylanase Pulpzyme HC allowed an increase of c. 1.5% in pulp brightness while decreasing the brightness reversion and a concomitant pulp yield loss of only 0.5%. Significant chemical savings were obtained in the final D (70%) or P (45%) stages to achieve targeted final brightness of c. 91%. DEDXD or DEDXP sequences had advantage over DEDDX and DEDPX, respectively, in terms of brightness stability of fully bleached pulps.CONCLUSIONSXylanase interferes with structures responsible for the brightness reversion. X stage allows production of pulp with extra brightness in sequences with a final P stage. © 2014 Society of Chemical Industry

Inverse gas chromatography and XPS of extracted kraft pulps

Abstract Kraft pulps at the κ number level of 15 obtained from Acer saccharum (sugar maple) and Eucalyptus globulus prepared with and without hot water extraction (HWE) were analyzed by inverse gas chromatography (IGC) and X-ray photoelectron spectroscopy (XPS). In the case of A. saccharum pulps, the dispersive component of the surface energy (γ s d) at 40°C determined by IGC was 39.8 mJ m-2 (control pulp without HWE) and 36.7 mJ m-2 (HWE pulp). Eucalyptus globulus pulps resulted in γ s d values of 30.8 mJ m-2 (control) and 34.9 mJ m-2 (HWE). The higher values of γ s d for sugar maple pulps were interpreted as the influence of lower amounts of extractives or lignin at their surface, as revealed by XPS. It is also discussed why the acid-base character of the sugar maple pulp surface was slightly reduced with previous HWE, whereas, for E. globulus, it was greatly enhanced.

Infrared Spectroscopy as Alternative to Wet Chemical Analysis to Characterize Eucalyptus globulus Pulps and Predict Their Ethanol Yield for a Simultaneous Saccharification and Fermentation Process

Bioethanol can be obtained from wood by simultaneous enzymatic saccharification and fermentation step (SSF). However, for enzymatic process to be effective, a pretreatment is needed to break the wood structure and to remove lignin to expose the carbohydrates components. Evaluation of these processes requires characterization of the materials generated in the different stages. The traditional analytical methods of wood, pretreated materials (pulps), monosaccharides in the hydrolyzated pulps, and ethanol involve laborious and destructive methodologies. This, together with the high cost of enzymes and the possibility to obtain low ethanol yields from some pulps, makes it suitable to have rapid, nondestructive, less expensive, and quantitative methods to monitoring the processes to obtain ethanol from wood. In this work, infrared spectroscopy (IR) accompanied with multivariate analysis is used to characterize chemically organosolv pretreated Eucalyptus globulus pulps (glucans, lignin, and hemicellulosic sugars), as well as to predict the ethanol yield after a SSF process. Mid (4,000-400 cm(-1)) and near-infrared (12,500-4,000 cm(-1)) spectra of pulps were used in order to obtain calibration models through of partial least squares regression (PLS). The obtained multivariate models were validated by cross validation and by external validation. Mid-infrared (mid-IR)/NIR PLS models to quantify ethanol concentration were also compared with a mathematical approach to predict ethanol yield estimated from the chemical composition of the pulps determined by wet chemical methods (discrete chemical data). Results show the high ability of the infrared spectra in both regions, mid-IR and NIR, to calibrate and predict the ethanol yield and the chemical components of pulps, with low values of standard calibration and validation errors (root mean square error of calibration, root mean square error of validation (RMSEV), and root mean square error of prediction), high correlation between predicted and measured by the reference methods values (R (2) between 0.789 and 0.997), and adequate values of the ratio between the standard deviation of the reference methods and the standard errors of infrared PLS models relative performance determinant (RPD) (greater than 3 for majority of the models). Use of IR for ethanol quantification showed similar and even better results to the obtained with the discrete chemical data, especially in the case of mid-IR models, where ethanol concentration can be estimated with a RMSEV equal to 1.9 g L(-1). These results could facilitate the analysis of high number of samples required in the evaluation and optimization of the processes.

Evaluation of the papermaking potential of Ailanthus altissima

In this work, Ailanthus altissima (tree-of-heaven) wood was analyzed for its chemical, morphological and papermaking properties. The A. altissima wood was cooked under kraft conditions using different active alkali charges and then handsheets were produced with the pulps having a kappa number of 16. Based on structural, strength and optical data it was found that the kraft pulp of A. altissima is not suitable to be used alone for the production of printing and writing papers. Notwithstanding, the handsheets exhibit a favorable value of brightness in comparison to those produced from Eucalyptus globulus pulp (with similar kappa number). Therefore, the wood of A. altissima seems to have a good potential to be used as a partial substitute of the main raw material of the Portuguese pulp industry. In fact, the results showed that when beaten E. globulus and A. altissima pulps were mixed (50:50, w/w), the papermaking properties were comparable to those of beaten eucalypt kraft pulps. Therefore, the use of A. altissima wood seems promising for the production of uncoated wood-free papers, which has advantages both from an economical and environmental perspective.

β-Glucosidase immobilisation on synthetic superparamagnetic magnetite nanoparticles and their application in saccharification of wheat straw and Eucalyptus globulus pulps

β-Glucosidase from Trichoderma reesei was immobilised on synthetic superparamagnetic magnetite (Fe3O4) nanoparticles with a mean diameter of 10 nm and were used to supplement cellulase in the enzymatic hydrolysis of three substrates: wheat straw pretreated by steam explosion, Eucalyptus globulus pretreated by hydrothermolysis and E. globulus pretreated by hydrothermolysis followed by alkaline extraction. The hydrolysis yields for each pretreated material, using immobilised β-glucosidase (I-βG) and free cellulase, were 76.1%, 83.6% and 75.6%, respectively, and resulted in an improved hydrolysis yields compared with only cellulase. These yields were at most 10% lower than yields reached with free enzymes. The (I-βG) was magnetically recovered and successfully reused twice. The differences in the hydrolysis yields were not significant (p > 0.05) in the case of steam-exploded wheat straw and E. globulus pretreated by hydrothermolysis followed by alkaline extraction. The immobilisation of enzymes provides an opportunity to reduce the costs of enzymes in the bioethanol production process.

Antioxidant Activity of Lignin Phenolic Compounds Extracted from Kraft and Sulphite Black Liquors

The antioxidant activity of the phenolic compounds present in industrial black liquors obtained from the two cooking processes (kraft and sulphite) used in Portugal to produce Eucalyptus globulus pulp was evaluated. The black liquors treated at several pH values were extracted with ethyl acetate. Phenolic fractions were further separated by liquid chromatography of the crude extracts of kraft liquor at pH = 6 and sulphite liquor at the original pH. Total phenolic content was determined in terms of gallic acid equivalents (Folin-Ciocalteu colorimetric method), and the antioxidant activity in the crude extracts at several pH values and in the separated fractions was measured using the DPPH test for radical scavenging capacity. The total phenolic content of crude extracts and separated fractions ranged from 92.7 to 181.6 and from 91.6 to 1,099.6 mg GAE/g, respectively, while the antioxidant activity index (AAI) ranged from 2.20 to 3.41 and from 2.21 to 11.47 respectively, showing very strong antioxidant activity in all studied cases. The fractions separated by column chromatography were submitted to mass spectrometry analysis and the results were compared to others in the literature of natural products, mainly from Eucalyptus, and the characteristic bands of functional groups were identified by 1H-NMR and FTIR. These methods allowed the identification of 17 phenolic compounds.

Effect of high pressure treatment on structure and properties of cellulose in eucalypt pulps

Bleached acid sulphite and kraft Eucalyptus globulus pulps were subjected to treatment at high hydrostatic pressure (400 MPa during 10 min). The associated structural changes of cellulose were evaluated by X-ray scattering, solid-state NMR and infrared spectroscopy. The high pressure treatment promoted the growth of crystalline domains predominantly via lateral aggregation (cocrystallization) and, to some extent, due to the accretion of cellulose from noncrystalline domains (recrystallization). The treated pulps exhibited increment of the amount of strongly bound water and improved accessibility to amorphous domains. The high pressure treatment of dried sulphite pulp led to restoration, at least partially, of its swelling capacity thus diminishing the hornification features. Pressure treated dried sulphite pulp showed improved fibre bonding capacity at simultaneously increased bulk of the produced handsheets. The results obtained clearly showed the potential of high pressure treatments for the modification of cellulosic fibres in different applications.

Influence of operation conditions on laccase-mediator removal of sterols from eucalypt pulp

The way how sterols, the main lipophilic compounds present in eucalypt kraft pulp, are eliminated by an enzymatic stage using the laccase-mediator system was evaluated. With this purpose laccase-mediator stage (L) was applied on an Eucalyptus globulus pulp under different operation conditions following a three-variable (laccase dose, mediator dose and reaction time) sequential statistical plan, to optimise the removal of sterols. The decrease in pulp sterol content during the enzymatic treatment was related to the decrease in kappa number and to brightness increase, as well as with the increase in some oxidation products of sitosterol (namely 7-oxositosterol and stigmasta-3,5-dien-7-one). The increase in reaction time from 1 to 5 h strongly reduced the sterol content, while no more sterols were eliminated during the 5–7 h period. Increasing the laccase dose from 1 to 20 U g −1 of pulp produced a high reduction in pulp sterols, whereas the increase in mediator (1-hydroxybenzotriazole) dose (from 0.5 to 2.5% of pulp weight) had only a slight influence in removing sterols. Therefore, at 16 U g −1 laccase dose, 0.5% mediator dose, 4 h of reaction, practically all the sterols were removed. Finally, it was demonstrated that sterols were more sensitive to a L stage (practically 100% of sterols were eliminated) than to a chlorine dioxide stage (54% of sterols eliminated).

Cynara cardunculus L. alkaline pulps: Alternatives fibres for paper and paperboard production

The pulping of Cynara cardunculus L. (cardoon) was performed under conditions for kraft, kraft-AQ and soda-AQ processes. The best results in terms of delignification degree, expressed as kappa number, pulp viscosity and screened yield, were obtained for the kraft-AQ process with 0.20% of anthraquinone (AQ). The papermaking potential of the selected pulp was studied attending to biometric fibre characterisation, refining aptitude, optical and strength properties. All properties were compared against a Eucalyptus globulus pulp at different refining degrees. The cardoon pulp was also evaluated concerning its potential to board manufacture, alone and in mixtures with pine pulp, giving rise to promising results for liner manufacture.

Pressurized hydrogen peroxide bleaching of Eucalyptus globulus pulps. Part II: Kinetics

Pressurized hydrogen peroxide bleaching of Eucalyptus globulus pulps. Part II: Kinetics

Pressurized hydrogen peroxide bleaching of Eucalyptus globulus pulps. Part I: Effect of process variables

Article Pressurized hydrogen peroxide bleaching of Eucalyptus globulus pulps. Part I: Effect of process variables was published on January 1, 2007 in the journal Nordic Pulp & Paper Research Journal (volume 22, issue 1).

Life cycle assessment of printing and writing paper produced in Portugal

The environmental sustainability is one of the current priorities of the Portuguese pulp and paper industry. Life Cycle Assessment (LCA) was the methodology chosen to evaluate the sustainability of the printing and writing paper production activity. This paper grade represents about 60% of the total production of paper in Portugal and its production is expected to increase in the near future. The main goal of this study was to assess the potential environmental impacts associated with the entire life cycle of the printing and writing paper produced in Portugal from Eucalyptus globulus pulp and consumed in Germany, in order to identify the processes with the largest environmental impacts. Another goal of this study was to evaluate the effect on the potential environmental impacts of changing the market where the Portuguese printing and writing paper is consumed: German market vs. Portuguese market. The main stages considered in this study were: forestry, pulp production, paper production, paper distribution, and paper final disposal. Transports and production of chemicals, fuels and energy in the grid were also included in these stages. Whenever possible and feasible, average or typical data from industry were collected. The remaining data were obtained from the literature and specialised databases. A quantitative impact assessment was performed for five impact categories: global warming over 100 years, acidification, eutrophication, non-renewable resource depletion and photochemical oxidant formation. In the German market scenario, the paper production stage was a remarkable hot spot for air emissions (non-renewable CO2, NOx and SO2) and for non-renewable energy consumption, and, consequently, for the impact categories that consider these parameters: global warming, acidification and non-renewable resource depletion. These important environmental impacts are due to the energy requirements in the printing and writing paper production process, which are fulfilled by on-site fuel oil burning and consumption of electricity from the national grid, which is mostly based on the use of fossil fuels. The pulp production stage was identified as the largest contributor to water emissions (COD and AOX) and to eutrophication. Considering that energy consumed by the pulp production processes comes from renewable fuels, this stage was also the most contributing to renewable energy consumption. The paper distribution stage showed an important contribution to NOx emissions, which, however, did not result in a major contribution to acidification or eutrophication. The final disposal stage was the main contributor to the photochemical oxidant formation potential due to CH4 emissions from wastepaper landfilling. On the other hand, paper consumption in Portugal was environmentally more favourable than in Germany for the parameters/impact categories where the paper distribution stage has a significant contribution (non-renewable CO2, NOx, non-renewable energy consumption, acidification, eutrophication and non-renewable resource depletion) due to shorter distances needed to deliver paper to the consumers. For the remaining parameters/impact categories, the increase observed in the final disposal stage in the Portuguese market was preponderant, and resulted from the existence of significant differences in the final disposal alternatives in the analysed markets (recycling dominates in Germany, whereas landfilling dominates in Portugal). The pulp and paper production stages were found to be of significance for almost all of the inventory parameters as well as for the impact assessment categories. The paper distribution and the final disposal stages were only of importance for some of the inventory parameters and some of the impact categories. The forestry stage played a minor role in the environmental impacts generated during the paper life cycle. The consumption of paper in Portugal led to a decrease in the environmental burdens of the paper distribution stage, but to an increase in the environmental burdens of the final disposal stage, when compared with the consumption of paper in Germany. This study provides useful information that can assist the pulp and paper industry in the planning of future investments leading to an increase in its sustainability. The results of inventory analysis and impact assessment show the processes that play an important role in each impact category, which allow the industry to improve its environmental performance, making changes not only in the production process itself, but also in the treatment of flue gases and liquid effluents. Besides that concern regarding pollution prevention, other issues with relevance to the context of sustainability, such as the energy consumption, can also be dealt with.

Rheological behaviour of carboxymethylcellulose manufactured from TCF-bleached Milox pulps

Carboxymethylcellulose (CMC) samples with different degrees of substitution were obtained from Eucalyptus globulus pulps made in formic acid-peroxyformic acid medium (Milox delignification) and subjected to Totally Chlorine Free bleaching. In order to assess the rheological behaviour of the synthesized materials, their properties (rheological behaviour, solubility and molar mass) were determined and examined in relation to their total degree of substitution. Additional discussion on the structure and purity of pulps, alkali celluloses, and CMC is provided.

Lipophilic Extractives from Eucalyptus globulus Pulp during Kraft Cooking Followed by TCF and ECF Bleaching

SummaryThe chemical composition of lipophilic extractives in paper pulps fromEucalyptus globuluswood during kraft cooking followed by TCF (“totally chlorine free”) and ECF (“elemental chlorine free”) bleaching sequences has been determined by gas chromatography and gas chromatography-mass spectrometry. The chemical analyses revealed that the composition of the lipophilic extractives in pulp after kraft cooking and TCF bleaching with hydrogen peroxide was similar to that ofE. globuluswood extractives, sitosterol and sitosterol esters being the predominant compounds. In contrast, the presence of these compounds was almost negligible in pulp after ECF bleaching with chlorine dioxide and only the saturated sterol stigmastanol, in both free and esterified forms, survived the bleaching.