Abstract
Energetic efficiency of sugarcane mills in Brazil has been increasing in the past decades, generating a surplus of bagasse. Even though bagasse has a low energy density, it has been used as fuel in boilers. Pyrolysis, a thermochemical process, produces bio-oil and biochar, being an alternative to increasing the energy density of biomass. In this context, bio-oil, when compared to bagasse, is more versatile in terms of use, storage, and transport. However, this biofuel is typically a viscous, acid, and thermally unstable liquid, which is harmful to engines and boilers. Furthermore, polymerization of bio-oil occurs during aging, which increases viscosity, average molar mass, and water content. In order to avoid these problems, upgrading techniques can be used. These techniques are usually applied to the whole oil. Nonetheless, the upgrading may be more effective if the bio-oil is fractioned and each fraction is processed separately. This study assessed the upgrade of the heavy fraction of bio-oil (HBO) through solvent addition. Initially, two different concentrations (10 wt. % and 15 wt. %) of methanol, ethanol, and acetone were added into HBO. The mixtures were submitted to an accelerating aging process: storage for 24 h at 80 °C. Physical properties including viscosity, pH, and water content were measured before and after storage. According to the properties analyzed, all blends met the appropriate specifications of ASTM D7544 (2017) for fast pyrolysis bio-oil. The results also indicated that all solvents had a significant effect on HBO properties, whereas their addition reduced its viscosity, improving stability. The blended HBO with 15 wt. % methanol achieved the lowest viscosity and aging rate. Therefore, in this case, methanol was more efficient than ethanol or acetone.
