Valorisation of crude glycerol in the production of liquefied lignin bio-polyols for polyurethane formulations.

Bio-polyols, produced by liquefying lignin with polyhydric alcohols, offer a promising alternative to conventional polyols for polyurethane production. To enhance the sustainability on the production of these bio-polyols, this study proposes the use of crude glycerol and microwave-assisted liquefaction as substitutes for conventional methods and commercial glycerol. This approach reduces the energy requirements of the reaction while also adding value to this by-product. The synthesis of bio-polyols with suitable properties to produce elastic and rigid polyurethane was carried out using previously optimised reaction conditions. Organosolv lignins obtained from Eucalyptus globulus and Pinus radiata were employed, using polyethylene glycol and crude glycerol as solvents and sulphuric acid as a catalyst. Several parameters of the bio-polyols were analysed, including hydroxyl number (IOH), acid number (An), and functionality (f), suggesting that the bio-polyols were suitable for polyurethane synthesis. Bio-polyols formulated to produce rigid polyurethanes exhibited IOH values of 554 and 383 (mg KOH/g), An values of 1.91 and 4.21 (mg KOH/g), and functionalities of 4.16 and 3.14 for Eucalyptus globulus and Pinus radiata lignin. In the case of bio-polyols for elastic polyurethanes, the values were 228 and 173 (mg KOH/g) (IOH), 20.94 and 25.09 (mg KOH/g) (An), and functionalities of 3.51 and 2.08.

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.

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.