Abstract
Cork wastes and by-products were used as raw materials to access sustainable biopolyols in a fast and clean manner. Contributing for the mitigation of a residue recorded as industrial residues in the European waste catalogue and hazardous waste list reducing, therefore, its environmental impact. Cork powder resulting from the cork industry as a waste and/or by-products with no commercial value was subjected to liquefaction in 2-ethyl hexanol/DEG in the presence of p-toluene sulfuric acid. Microwave radiation was used as the heating source. Pulsed microwaves from 150-300 W power were applied for 5-20 min. This alternative energy source was successfully applied leading to a high conversion of cork powder into liquid biopolyols. The efficiency of liquefaction increased with higher microwave power and shorter reaction time. This study evidenced that cork powder can be liquidized via microwave. ATR experiments indicated that microwave led to a more intense oxidized cleavage of the lignocellulosic material and more extensive liquefaction reaction when compared to the conventional procedure.
Highlights
Liquefaction of biomass, such as lignocellulosic residues, is a process that has been largely investigated, consisting in the conversion into polyols towards the depolymerization and solubilisation of biomass at high temperatures [1,2,3,4,5].Being wood and forestry biomass a renewable, biodegradable, and abundant resource, it can be, and should be, seen as a source of raw materials for the chemical industry
The yields of the liquefaction processes were determined and the products obtained characterized by Scanning electron microscopy (SEM) and Attenuated total reflectance (ATR)
The liquefaction extent of cork powder as a function of reaction time is shown in Figure 1 for conventional, ultrasounds- and microwave- assisted liquefaction
Summary
Liquefaction of biomass, such as lignocellulosic residues, is a process that has been largely investigated, consisting in the conversion into polyols towards the depolymerization and solubilisation of biomass at high temperatures [1,2,3,4,5].Being wood and forestry biomass a renewable, biodegradable, and abundant resource, it can be, and should be, seen as a source of raw materials for the chemical industry. This process can lead to a wide variety of reagents used in the formulations of biomaterials, resin and coatings and others. This means that could be possible to project different chemical structures of liquid wood aiming their final application [10]. Amongst them is esterification or etherification of free hydroxyl groups in cellulose or lignin along with reactions that decomposes cellulose into smaller units This complex set of reactions is even more extensive due of the large number of minor wood components ranging from gums and resins to minerals and salts [11]. The reaction pathway of lignin depolymerization is not known but it was shown that the presence of lignin plays a major role in the post-liquefaction re-condensation reactions, leading to insoluble precipitates [13]
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