M. Virginia Alonso

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.

Combining autohydrolysis and ionic liquid microwave treatment to enhance enzymatic hydrolysis of Eucalyptus globulus wood

The combination of autohydrolysis and ionic liquid microwave treatments of eucalyptus wood have been studied to facilitate sugar production in a subsequent enzymatic hydrolysis step. Three autohydrolysis conditions (150 °C, 175 °C and 200 °C) in combination with two ionic liquid temperatures (80 °C and 120 °C) were compared in terms of chemical composition, enzymatic digestibility and sugar production. Morphology was measured (using SEM) and the biomass surface was visualized with confocal fluorescence microscopy. The synergistic cooperation of both treatments was demonstrated, enhancing cellulose accessibility. At intermediate autohydrolysis conditions (175 °C) and low ionic liquid temperature (80 °C), a glucan digestibility of 84.4% was obtained. Using SEM micrographs, fractal dimension (as a measure of biomass complexity) and lacunarity (as a measure of homogeneity) were calculated before and after pretreatment. High fractals dimensions and low lacunarities correspond to morphologically complex and homogeneous samples, that are better digested by enzyme cocktails.

Effect of autohydrolysis on Pinus radiata wood for hemicellulose extraction

The extraction of hemicellulose from pine wood was studied by applying autohydrolysis treatment. A central composite experimental design was carried out using different temperatures (150-190 °C) and times (30-90 min) to select the most favorable operating conditions for maximizing the extraction of hemicellulose and minimizing its degradation. This liquid phase was analyzed by HPLC to quantify oligosaccharides, monosaccharides and degradation products. The composition of the autohydrolyzed wood was determined and characterized, employing FTIR and TGA. Herein, 60% of the hemicelluloses were extracted under a temperature of 170 °C in 60 min, presenting primarily in an oligomeric form in the liquid phase, with the solid phase remaining enriched in cellulose and lignin.