Mercedes Oliet

Solvent effects in autocatalyzed alcohol–water pulping: Comparative study between ethanol and methanol as delignifying agents

Abstract The autocatalyzed pulping (without additives) of Eucalyptus globulus with ethanol–water and methanol–water is studied in order to compare the effects of the two more frequently used solvents in Organosolv pulping. The study about the influence of the pulping alcohol on pulp properties (measured as Kappa number, yield and viscosity) is carried out by means of a 2 4 factorial design including the type of alcohol as a categorical variable. The effects for the variables (temperature, time, concentration and type of alcohol) and the interactions among them are determined. The statistical analysis for each response makes it possible to evaluate if the type of alcohol has a significant influence on the properties of the pulp obtained. In the range of temperature, time and solvent concentration studied, methanol yields pulps with lower Kappa number, on average; whereas ethanol provides better delignification at high-intensity cooking conditions. Both alcohols show similar selectivity when pulp total yield is considered, but higher screened yield values can be obtained in ethanol pulping. The viscosity is better for ethanol pulps on average, however, in the 20–30 Kappa number range methanol pulps exhibit higher viscosity.

Recovery of Solvent and By-Products from Organosolv Black Liquor

The recovery of alcohol and by-products from ethanol-water and methanol-water pulping liquors was studied. The recovery system proposed consists of three stages: black liquor flashing, lignin precipitation, and precipitation distillation of mother liquor. At the flash stage, 47 and 51% of the alcohol in the black liquor are recovered for ethanol and methanol processes, respectively. The lignin recovery yield at the precipitation stage is 67% for ethanol black liquor and 73% for methanol black liquor. The distillation of precipitation mother liquors enables recovery of 98% ethanol and 96% methanol from this stream as distillate, whereas the distillation residue contains significant amounts of sugars, furfural, and acetic acid that can be recovered. The study concludes with the overall mass balance for the recovery system proposed.

Relation between differential solubility of cellulose and lignin in ionic liquids and activity coefficients

In this work, the excess enthalpies and activity coefficients were evaluated as reference parameters of the solubility of cellulose and lignin in ionic liquids (ILs) using COSMO-RS. Guided by experimental tests, a variety of solubility behaviours of these compounds in 12 ILs with different anions was reported. Appropriate molecular models able to simulate the behaviour of real cellulose and lignin compounds were selected with the aid of experimental data on their dissolution in ILs. The aim was to develop a reliable COSMO-RS computational approach to predict the ability of an IL to dissolve cellulose and/or lignin. A 3 × 3 cellulose structure was optimized in order to achieve an adequate model for describing cellulose solubility, and nine different models were obtained. Several molecules were evaluated as lignin models in COSMO-RS calculations, such as pinoresinol, guaiacylglycerol-2-coniferyl ether, and p-coumaryl, coniferyl and sinapyl alcohols. The results showed that the activity coefficient was the most consistent property to predict the ability of ILs to dissolve these compounds, allowing a tentative classification of the cellulose and lignin differential solubility in ILs in terms of this parameter value. In addition, the study of the differential solubility of cellulose and lignin, based on the developed COSMO-RS approach, was extrapolated to a wide sample of 750 ionic liquids, including 25 cations and 30 anions.

Preliminary study on products distribution in alcohol pulping of Eucalyptus globulus

The aim of the present work was to study the fractionation of Eucalyptus globulus wood into pulp and by-products by alcohol-water pulping. Under the cooking conditions employed low lignin content pulp and a high yield of by-products were attained. The laboratory-scale alcohol and by-products recovery system studied consisted of three stages: black liquor flashing, lignin precipitation from black liquor, and distillation of precipitation mother liquor. The mass balance for the process enabled the amount of pulp and by-products produced and the consumption of chemicals to be estimated.

Acid Precipitation and Purification of Wheat Straw Lignin

The acid precipitation and purification of lignin from wheat straw soda pulping effluent were studied. Prior to lignin precipitation, the suspended solids and dissolved silica were removed from the effluent to avoid lignin contamination. Suspended solids and dissolved silica were removed by centrifugation and selective precipitation at pH 5, respectively. After these treatments, the pH of the effluent was reduced to an optimum pH value of 3.5 with sulfuric acid in order to precipitate lignin. About 80% of the total lignin was recovered. Effluent color and COD were simultaneously reduced by 82 and 71%, respectively. Lignin precipitate purification was carried out by washing with aqueous acidic solutions. Only the time and the agitation rate influenced the washing process. The purity of the lignin was very high when the time and rate of agitation during washing were low. Under optimum conditions, lignin with a purity of 99.5% can be obtained.

PHENOLIC OH GROUP ESTIMATION BY FTIR AND UV SPECTROSCOPY. APPLICATION TO ORGANOSOLV LIGNINS

The phenolic hydroxyl group content of 34 acetylated organosolv lignins, obtained by ethanol or methanol autocatalyzed pulping of Eucalyptus globulus was measured by FTIR spectroscopy. The absorbance of aromatic IR ester bands of acetylated lignins at 1765 cm−1 was employed to estimate the lignin phenolic hydroxyl group content. To compare different samples the spectra recorded were baseline corrected and normalized with the bands around 1500, 1600 and 1423 cm−1. Partial least-squares (PLS) and multiple linear regression (MLR) calibrations were carried out to establish a mathematical correlation between UV data sets and FTIR spectra. The best results were shown by the models obtained by PLS regression. In these models the band at 1766 cm−1 was normalized using the band at 1744 cm−1 and the baseline corrections were performed with the bands at 1423 cm−1 (ethanol lignin) and 1507 cm−1 (methanol lignin).

Lignin behavior during the autocatalyzed methanol pulping of Eucalyptus globulus. Changes in molecular weight and functionality.

Summary The molecular weight distribution and functional group contents (phenolic and carbonyl) of lignin samples from the autocatalyzed pulping of Eucalyptus globulus wood were determined. A total of 17 pulping runs were carried out at different conditions according to a surface response design experimental matrix (central composite). The influence of pulping temperature (170–200°C), pulping time (40–120 min) and methanol concentration (30–70%, w/w) on the characteristics of the isolated lignins was studied. Empirical models were developed and used to predict the lignin properties as a function of the cooking conditions. Under high temperature, long cooking time and low alcohol concentration, a rise in functional groups content and a drop in molecular weight of lignin

Characterization of cellulose regenerated from solutions of pine and eucalyptus woods in 1-allyl-3-methilimidazolium chloride

Cellulose is currently separated from lignocellulosic materials using non-environmentally friendly processes. The development of new methods for treating biomass and separating cellulose remains a challenge and would be very useful in the context of the biorefinery philosophy. In this work, cellulose has been regenerated from solutions of Pinus radiata and Eucalyptus globulus woods in 1-allyl-3-methylimidazolium chloride. Wood dissolution was performed in a microwave oven at 120 °C for 20 min. Cellulose was characterized and compared to the reference material, microcrystalline cellulose (MCC). Regenerated celluloses showed lower crystallinity and thermal stability than MCC, although the ash contents at 400 °C were higher than in MCC. The regenerated celluloses were obtained without lignin and almost free from hemicellulose. Furthermore, cellulose was not significantly degraded in the dissolution process of both woods. The insoluble solids showed higher content of lignin and hemicellulose than the raw materials.

The effect of autocatalyzed ethanol pulping on lignin characteristics

The development of phenolic hydroxyl and carbonyl groups and the changes in the molecular weight of lignin during the autocatalyzed ethanol-water pulping of Eucalyptus globulus wood was modeled. The models were developed using a response surface method and were employed to study the influence of cooking temperature, cooking time and ethanol concentration on lignin characteristics. The functional groups content was found to increase as the cooking time was risen and the concentration of ethanol in the pulping liquor was reduced. These cooking conditions lead to a more extensive cleavage of the bonds between lignin units due to the longer treatment, higher temperature and increased acidity of the pulping liquor. The cleavage of lignin bonds resulted in the occurrence of new functional groups and a reduction in lignin molecular weight. The steady decrease in molecular weight with the intensity of cooking conditions indicates that lignin condensation does not play an important role under the conditions studied.

Self-organizing maps and learning vector quantization networks as tools to identify vegetable oils.

Self-organizing map (SOM) and learning vector quantification network (LVQ) models have been explored for the identification of edible and vegetable oils and to detect adulteration of extra virgin olive oil (EVOO) using the most common chemicals in these oils, viz. saturated fatty (mainly palmitic and stearic acids), oleic and linoleic acids. The optimization and validation processes of the models have been carried out using bibliographical sources, that is, a database for developing learning process and internal validation, and six other different databases to perform their external validation. The models performances were analyzed by the number of misclassifications. In the worst of the cases, the SOM and LVQ models are able to classify more than the 94% of samples and detect adulterations of EVOO with corn, soya, sunflower, and hazelnut oils when their oil concentrations are higher than 10, 5, 5, and 10%, respectively.