Catalytic Pyrolysis of Açaí (<em>Euterpe oleracea</em> Mart.) Seeds: Circular Economy for Agro-industrial Waste-to-Energy in the Amazon

In this study, the influence of chemical impregnation with an aqueous sodium hydroxide (NaOH) solution at 2 mol·L⁻¹, as well as process temperature, was systematically investigated at a pilot scale on the yield of pyrolysis products (bio-oil, gas, water, and biochar), as well as on the physi-cochemical properties (acid value, density, and kinematic viscosity) and chemical composition (hydrocarbons and oxygenated compounds) of the bio-oil obtained from açaí seeds (Euterpe oleracea Mart.). The pyrolysis reactions were carried out in a 143 L batch reactor at temperatures of 350 °C, 400 °C, and 450 °C under a pressure of 1.0 atmosphere. The NaOH impregnation played a crucial role in modifying the thermal degradation pathway of the biomass, promoting the formation of specific chemical structures and altering the product yields. NaOH acted as a catalyst, enhancing the deoxygenation of the biomass and stimulating the formation of hydrocarbons. As a result, the yields of bio-oil, water, biochar, and gas varied from 5.77 to 7.20% (by mass), 14.90 to 19.77% (by mass), 41 to 54% (by mass), and 25.33 to 32.03%, respectively, influenced by the increase in temperature. FT-IR analyses indicated the presence of characteristic chemical functions of hydrocarbons (alkanes, alkenes, and aromatics) and oxygenated compounds (phenols, cresols, ketones, esters, carboxylic acids, aldehydes, and furans), with an intensification of hydrocarbon signals at higher temperatures. GC-MS analysis confirmed hydrocarbons and oxygenated compounds as the main chemical classes in the bio-oil, showing a strong dependence on pyrolysis temperature. It was observed that the hydrocarbon concentration increased from 49.7% to 57.88% (area) with rising temperature, while the concentration of oxygenated compounds decreased from 13.88% to 6.69% (area), demonstrating that NaOH impregnation, combined with temperature elevation, favors the formation of hydrocarbons and the reduction of oxygenated compounds, thereby improving the quality of the produced bio-oil.