María González Alriols

Ultrasound-assisted fractionation of the lignocellulosic material

In the present work the effectiveness of different lignocellulosic biomass fractionation processes based on ultrasounds technology was evaluated. Organosolv (acetic acid 60% v/v), alkaline (sodium hydroxide 7.5% w/w) and autohydrolysis treatments were applied at low temperature and the fractionation effectiveness was measured at different sonication conditions of the raw material. The obtained solid fractions were characterized using TAPPI standard methods, and the liquid fractions main components were quantified with the purpose of studying the effect that the treatment conditions had on the obtained by-products quality. Therefore, obtained lignin samples were characterized by ATR-IR spectroscopy and their thermal behaviour by TGA technique. The results showed that ultrasounds application improved the yield and selectivity of the studied processes and that the obtained lignin did not suffer significant modifications in its physicochemical properties.

Evaluation of the effect of ultrasound on organosolv black liquor from olive tree pruning residues

Ultrasonic treatments (0, 15, 30, 60 and 120 min) were applied to black liquor resulting from organosolv fractionation of olive tree pruning residues (ethanol/water 60/40 v/v, 180 °C, 60 min) in order to determine their effect on black liquor components. HPLC analyses of ultrasound-treated liquid fractions demonstrated that ultrasonic irradiation promoted up to 20% degradation of monosaccharides for 15 min of sonication and an increase of monomeric sugars from 3% to 16% due lignin-carbohydrate complex rupture. The quality and purity of the lignin precipitated from sonicated liquors by adding acidified water were assessed. Attenuated-total reflectance infrared spectroscopy (ATR-IR), gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) confirmed that main lignin structure did not change due sonication, and thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and chemical composition and antioxidant behavior showed purification of lignin samples. These results established sonication as a suitable intensification technology in biorefinery processes.

Assessment of biorefinery process intensification by ultrasound technology.

In the present work, on the basis of literature data, correlations for ultrasound-assisted dissolution of lignin and hemicelluloses from lignocellulosic raw material were defined in Aspen Plus® as function of applied power and duration of the ultrasound treatment. The dissolution yield of these biomass components was represented against the applied acoustic energy, taking into account the volume of solvent–solid treated in each case, making possible the calculation of ultrasonic power consumption in a simulated biorefinery pretreatment process. The proposed ultrasound-assisted process was techno-economically evaluated in terms of process yield and utility requirements. Furthermore, energy and exergy analyses were performed in order to assess the profitability of the simulated ultrasound-assisted biomass fractionation processes.

Energetic assessment of lignin extraction processes by simulation

Abstract The energetic requirements of several processes for high-purity lignin production from lignocellulosic waste streams has been studied in this work, based on simulation analysis performed with experimental data. The introduced variables were: two different raw materials (almond shell and olive tree pruning), the use of a pre-treatment stage and the application of two different sulphur-free delignification methods (organosolv and soda processes) with their subsequently lignin precipitation steps. In total, four scenarios were approached and assessed in terms of desirable product yields, water and chemical consumptions and energetic duties. Results showed a more efficient process when almond shell was used as raw material. In terms of the delignification process, organosolv method required a much lower quantity of chemicals due to the recycle and recirculation of the solvent (ethanol). The energy consumption associated to this recycle implied an increase of 18-12 % in the total energy consumption. On the other hand, lignin product yield was higher with soda process although its chemical consumption was found to be much higher, in terms of soda and sulfuric acid requirements.