Valorização do bio-óleo do resíduo de sisal

Abstract

Bio-oil from sisal residue, produced through the process of fast pyrolysis in a fluidized bed, has a differentiated composition, which stands out due to its high viscosity and pour point, low O/C ratio, high thermal stability and high content of phenols. However, it still needs to be improved in order to be used in biorefineries and for the production of chemical species of industrial interest. Therefore, the present work aims to evaluate the reduction of oxygenated species in the bio-oil from sisal residue by manipulating the operational variables of the fast pyrolysis process and its catalytic transformation via hydrodeoxygenation (HDO). The process/product relations of the pyrolysis were studied by varying the nitrogen flow rate, biomass mass flow rate, temperature and pressure. In general, the bio-oil composition was intensely dependent on the process parameters. The lowest pressure studied was the best condition for obtaining bio-oil with high yield (up to 17 wt%), with higher yield of monomers (44.51 wt%) and lower O/C ratio (0.11). The results also indicated that the bio-oil from the sisal residue has a composition with high levels of phenolic, aliphatic and naphthalene compounds. It has, therefore, great potential for obtaining biofuels and/or aromatics and phenols with high added value via catalytic upgrade, due to the low oxygen content and high degree of depolymerization. In the HDO step, Ni-Cu/Al-MCM-41 type catalysts were active in the hydrotreatment of bio-oils from sisal residue and pinewood. The bimetallic catalysts 20Ni5Cu and 20Ni10Cu showed the best performances, promoting yields of 53.1 wt% and 51.2 wt% in the organic phase, higher than the benchmark RU/C (47.1%), in addition to promoting yields of 43.35 wt% and 42.84 wt% of monomers, respectively. There was a reduction in the average molecular weight (Mw), as well as in the O/C ratio and an increase in the H/C ratio, indicating a predominance of the hydrogenation/hydrodeoxygenation/hydrocracking route. In the case of bio-oil from sisal residue, the repolymerization route was predominant, resulting in lower H2 uptake, increased Mw and reduced monomer yields. However, there was a reduction in the O/C ratio of approximately 48 wt% on average compared to the feed, as well as an increase in aliphatic and aromatic hydrocarbons, alcohols and ketones.