Pré-tratamento organossolve com glicerina bruta em resíduos florestais de Pinus e Eucalipto no conceito de biorrefinarias

Abstract

The high consumption of energy from fossil sources, coupled with worsening environmental issues worldwide, has underscored the urgent need for rapid development and consolidation of efficient methods to produce advanced fuels and products from renewable resources. Lignocellulosic biomasses emerge as viable alternatives to replace fossil sources, not only to meet the growing energy demand but also to mitigate environmental impacts associated with greenhouse gas emissions. However, due to their complex structure, biomass and its residues require specific treatments for effective utilization. The pretreatment using organic solvents, known as organosolv, has proven to be efficient in fractionating the main components of biomass, which are cellulose, hemicellulose, and lignin, and in obtaining value-added bioproducts. Nevertheless, there are still few studies aiming to investigate the effect of this pretreatment on forest biomass and residues. Therefore, this study aimed to promote and evaluate the pretreatment of residual biomass from the country's two main cultivated forest species, pine and eucalyptus, using crude glycerin as a solvent to facilitate biomass delignification and component fractionation, as well as to generate other economically valuable bioproducts. The experiments were conducted in a batch reactor under previously determined conditions: 220°C, 40% crude glycerin/water ratio, for 120 minutes. After pretreatment, the solid fraction (pretreated biomass) and the liquid phase (black liquor) were separated through filtration. The in nature and pretreated biomasses were chemically and structurally characterized (XRD) to evaluate the efficiency of the pretreatment, and the lignin was recovered from the black liquor, quantified, and characterized (FT-IR). The black liquor was also analyzed by liquid chromatography (HPLC). As a result, high delignification rates were achieved for both residual biomasses, reaching 71.79% for pine and 83.77% for eucalyptus. The pretreated biomasses showed an increase in crystallinity index, indicating the removal of amorphous materials such as lignin and hemicellulose. In washing tests of the pretreated biomasses, methods involving NaOH solution and refluxing acetone were effective in solvent removal and obtaining residue-free biomass. As a means to validate the potential and usage of crude glycerin as a solvent, comparative tests were conducted with the purified form. The chosen solvent demonstrated superiority by achieving greater delignification and preserving cellulose to a higher degree.Lignins extracted from the pretreated biomasses were recovered from the black liquor and exhibited significant similarities to commercial lignin despite originating from different species. Other commercially valuable products identified in the black liquor included HMF, furfural, acetic acid, and their potential utilization and applicability require further investigation. Based on the results obtained, the organosolv pretreatment proved efficient and met the proposed objectives, particularly by using forest residues and crude glycerin as a solvent, thus representing a significant process in generating bioproducts, biofuels, and advancing lignocellulosic biorefineries.