Ethanol quenching in fast-pyrolysis of sugarcane bagasse and straw: Implications for bio-oil hydrodeoxygenation

The development of biofuels from sugarcane residues is attractive due to the abundance of sugarcane bagasse and straw, which can be converted into bio-oil via fast pyrolysis. Ethanol, also produced in sugarcane biorefineries, can be used as a direct quenching medium (QM) in fast pyrolysis to improve the vapor condensation step. However, the influence of ethanol quenching on downstream upgrading processes such as hydrodeoxygenation (HDO) has not yet been investigated. Thus, in this study, the properties of the organic condensate (hereafter referred to as bio-oil) produced via indirect cooling using a heat exchanger system (BS) were compared with one obtained through direct quenching with ethanol (BS-ET). Subsequently, both bio-oils were subjected to HDO to assess the impact of the condensation strategy on the upgrading step. Switching from indirect cooling to direct quenching with ethanol increased the ethanol content of the bio-oil from 1 wt% (BS) to 24 wt% (BS-ET). Remarkably, the concentration of reactive compounds prone to polymerization in the bio-oil (e.g., aldehydes and sugars) decreased beyond the dilution effect expected due ethanol quenching. ... mehrThe HDO of the BS yielded a two-phase product (viscous upgraded oil, and aqueous phase), while the HDO of BS-ET led to a single-phase product, with lower polymerization degree and reduced CO and CO$_2$ formation. These results indicate that quenching modified the phase equilibria and reaction pathways during fast pyrolysis, leading to improved performance in subsequent HDO upgrading.