Eco Valorization of Eucalyptus globulus Bark and Branches through Liquefaction

Eucalyptus globulus forest residues, bark, and branches, were characterized by wet chemistry methods and involved in the liquefaction process using a glycerol-ethylene glycol reaction mixture (1:1, v/v) catalyzed by strong mineral acid (3% H2SO4) or strong mineral base (6% KOH). The effect of the reaction conditions (temperature and duration) and the particle size on the yield of liquefied products have been evaluated. Acid catalysis revealed remarkably higher yields (25–50%) than when using basic catalyst. It was considered that bark was more vulnerable to liquefaction with respect to particle size than branches. Too high temperatures (>180 °C) are not advantageous regarding the liquefaction yields and, therefore, temperatures around 160–180 °C would be preferable. The best yield for the bark sample (>80 mesh fraction) was obtained at 180 °C for 60 min (61.6%), while for the branches the best yield was obtained at 160 °C for 60 min (62.2%). Under compromised conditions (180 °C for 60 min), the fine fraction (>80 mesh) of bark and branches did not show significant differences between their liquefaction yields and can be processed together while adjusting the suitable processing time. The main advantage of the use of these residues instead of solid wood is that it would bring the Forest managing companies a much higher income for their wastes that are usually burned and the use of lignocellulosic materials in detriment of petroleum-based materials for the production of polymers would make industry less dependent on oil prices fluctuations.

Thermal Degradation Kinetics of Urea-Formaldehyde Resins Modified by Almond Shells

Almond shell-modified urea-formaldehyde resins (AUF) were prepared in this study. The optimal addition amount of almond shells was selected by formaldehyde emission and wet shear strength. The activation energy (E _a) values at different conversion rates and the reaction kinetics were estimated based on the Flynn-Wall-Ozawa method. The results indicated that almond shells can significantly reduce the formaldehyde emission and increase wet shear strength and thermal stability of the urea-formaldehyde resin adhesive. The optimal addition of almond shells is 3 wt %.