Eucalyptus bleached kraft pulp-ionic liquid inks for 3D printing of ionogels and hydrogels

3D printing has been recently recognized as one of the most promising technologies due to the multiple options to fabricate cost-effective and customizable objects. However, the necessity to substitute fossil fuels as raw materials is increasing the research on bio-based inks with recyclable and eco-friendly properties. In this work, we formulated inks for the 3D printing of ionogels and hydrogels with bleached kraft pulp dissolved in [Emim][DMP] at different concentrations (1-4 wt%). We explored each ink's rheological properties and printability and compared the printability parameters with a commercial ink. The rheological results showed that the 3 % and 4 % cellulose-ionic liquid inks exhibited the best properties. Both had values of damping factor between 0.4 and 0.7 and values of yield stress between 1900 and 2500 Pa. Analyzing the printability, the 4 wt% ink was selected as the most promising because the printed ionogels and the hydrogels had the best print resolution and fidelity, similar to the reference ink. After printing, ionogels and hydrogels had values of the elastic modulus (G') between 10³ and 10⁴ Pa, and the ionogels are recyclables. Altogether, these 3D printed cellulose ionogels and hydrogels may have an opportunity in the electrochemical and medical fields, respectively.

Effect of autohydrolysis and ionosolv treatments on eucalyptus fractionation and recovered lignin properties†

Wood fractionation is key for the integral valorization of its three main components. In this sense, recovering the hemicellulosic fraction after the ionosolv treatment of lignocellulosic materials is one of the main drawbacks of this process. Thus, the incorporation of a previous autohydrolyisis step to recover the hemicellulosic sugars before the ionosolv treatment is an interesting approach. The influence of both treatments, autohydrolysis and ionosolv, on the biomass fractions recovery yields was studied by a central composite design of experiments, varying the autohydrolysis temperature in a 175–195 °C range and ionosolv time between 1–5 h. Lignin recovery and cellulose purity were maximized at 184 °C and 3.5 h of autohydrolysis temperature and ionosolv time, respectively. In addition, lignin properties were incorporated to the statistical model, revealing lignin recondensation at severe conditions and a higher influence of the ionosolv treatment on lignin characteristics. These results remarked the importance of studying the effect of both treatments in the whole fractionation process and not each process separately and enhanced the understanding of the treatments combination in a complete fractionation biorefinery approach.

This work enhances the understanding of the effect of autohydrolysis and ionosolv treatments combination on fractionation yields and lignin properties.

Organosolv and ionosolv processes for autohydrolyzed poplar fractionation: Lignin recovery and characterization

Biomass fractionation plays a major role in the search for competitive biorefineries, where the isolation and recovery of the three woody fractions is key. In this sense, we have used autohydrolyzed hemicellulose-free poplar as feedstock to compare two fractionation processes, organosolv and ionosolv, oriented to lignin recovery. The recovered lignins were then characterize by different techniques (NMR, GPC, TGA). Both treatments were tested at different temperatures to analyze temperature influence on lignin recovery and properties. The highest lignin recovery was obtained with the ionosolv process at 135 °C, reaching a solid yield of ~70%. Lignin characterization showed differences between both treatments. Lignins enriched in C-O linkages and G units were recovered with the organosolv process, where increasing temperature led to highly depolymerized lignins. However, lignins with higher C-C linkages and S units contents were obtained with the ionosolv process, producing more thermically stable lignins. In addition, increasing temperature caused lignin repolymerization when employing ionic liquids as solvents. Therefore, this work outlines the most important differences between ionosolv and organosolv processes for biomass fractionation, focusing on lignin recovery and its properties, which is the first step in order to valorize all biomass fractions.

Cellulose ionogels, a perspective of the last decade: A review

Cellulose ionogels have been extensively studied due to the variability of their properties and applications. The capability of trapping an ionic liquid in a biodegradable solid matrix without losing its properties makes this type of material a promising substitute for fossil fuel-derived materials. The possibility to formulate ionogels chemically or physically, to choose between different ionic liquids, cellulose types, and the possibility to add a wide range of additives, make these ionogels an adaptable material that can be modified for each target application in many fields such as medicine, energy storage, electrochemistry, etc. The aim of this review is to show its versatility and to provide a summary picture of the advances in the field of cellulose ionogels formulation (chemical or physical methods), as well as their potential applications, so this review will serve as a stimulus for research on these materials in the future.

Thermal degradation kinetics of a lignin particle-reinforced phenolic foam

In the present work, the thermal degradation kinetics of a phenolic (PF) and lignin particle-reinforced phenolic (LRPF) foam and the lignin used as the reinforcement (LR) were studied. The activation energies of the degradation processes were obtained using a discrete distributed activation energy model (discrete DAEM) and the Vyazovkin model-free kinetic (MFK) method. The discrete DAEM was validated by comparing the predicted values with the data obtained at 8 °C min−1. Heating ramps of 6 and 12 °C min−1 were used to calculate the kinetic parameters through the model. The effect of the reinforcement on the kinetics of the LRPF was studied by comparison with the results obtained for the PF. For reactions with non-zero mass fractions, the activation energies of the PF were in the range between 79.9 and 177.6 kJ mol−1, and the activation energy for the LRPF ranged from 91 to 187 kJ mol−1. For the LR, the activation energy values were in a narrower range than for the foams: 150–187 kJ mol−1. The degradation process of the LRPF was modified due to the use of LR: the range of activation energy for LRPF was between the ranges for the PF and LR. The activation energy dependence on conversion was also calculated using the Vyazovkin method and compared with the DAEM results; no compensation effect for the kinetic parameters was found.

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.

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 model's 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.

Modification of ammonium lignosulfonate by phenolation for use in phenolic resins

The structural modification of softwood ammonium lignosulfonate by phenolation was studied. A central factorial design was applied to determine the influence of reaction conditions (temperature, time and lignosulfonate content) on the properties of phenolation products. The reaction was monitored through the concentration of free phenol determined by gas chromatography (GC). The characterization of phenolation products was accomplished by gel permeation chromatography (GPC), fourier transform infrared (FTIR) and 1H nuclear magnetic resonance (1H NMR). Empirical models were developed to predict phenol conversion and adduct formation according to operating conditions. The optimum phenolation conditions, attained by means of a response surface method, were found to be 120 degrees C; 160 min and 30% lignosulfonate content