Thermochemical Transformation and Valorization of Fresh Açaí (Euterpe oleracea, Mart.) Seeds: Waste-to-Energy, Green Gaso-Line, Bio-Adsorbents Characterization, Adsorption of Organic Acids

In this work, the fresh seeds of Açaí (Euterpe oleracea Mart.), a rich lignin-cellulose residue, has been submitted to pyrolysis to produce a bio-oil like fuel. The pyrolysis reaction was carried out in a reactor of 143 L, operating in batch mode at 450 °C, 1.0 atmosphere. The morphology of the seeds of Açaí in nature and after pyrolysis process, were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The bio-oil and distillation fractions were physical-chemistry characterized by AOCS, ASTM, and ABNT/NBR methods for density, kinematic viscosity, acid value and refractive index. The chemical composition and qualitative analysis of chemical functions and/or groups present in bio-oil and distillation fractions were determined by GC-MS and FT-IR spectroscopy. The experimental data shows that bio-oil, a pyrolysis reaction liquid product, gas, H2O, and coke yields were 4.37% (wt.), 27.00, 33.63, and 35.00% (wt.), respectively. The bio-oil density and viscosity were 1.0468 g/cm3 and 162.96 mm²/s, respectively, with and acid value of 70.26 mg KOH/g. The GC-MS analysis shows that bio-oil is composed by 21.52% (wt.) hydrocarbons, and 78.48% (wt.) oxygenates (4.06% esters, 8.52% carboxylic acids, 3.53% ketones, 35.16% phenols, 20.52% cresols, 5.75% furans, and 0.91% (wt.) aldehydes. The distillation of bio-oil carried out in a laboratory scale column (Vigreux Column) according to the boiling temperature range of fossil fuels (gasoline, light kerosene, and kerosene). The distillation of bio-oil yielded gasoline, light kerosene, and kerosene-like fuel fractions of 16.16, 19.56, and 41.89% (wt.), respectively. The densities of gasoline, light kerosene, and kerosene-like fuel fractions were 0.9146, 0.9191, and 0.9816 g/cm3, respectively, while the kinematic viscosities were 1.457, 3.106, and 4.040 mm²/s, respectively, with acid values of 14.94, 61.08, and 64.78 mg KOH/g, increasing with boiling range temperature. The GC-MS analysis identified in gasoline, light kerosene, and kerosene-like fuel fractions 64.00%, 66.67%, and 19.87% (wt.) hydrocarbons. The pyrolysis has caused substantial changes on the morphological structure of Açaí seeds in nature by destructing the plant cell walls. The results of EDX show that carbon content increases from 79.28 to 89.98% (wt.), while that of oxygen decreases from 20.71 to 6.94% (wt.) at 450 °C. The results of XRD confirm the presence of 03 crystalline phases: graphite (C), cristobalite (SiO2), and quartz (SiO2), being the graphite the peak of high intensity (100%). The pyrolysis favors the formation of mineralogical phase graphite. The bio-adsorbent has been applied to selectively adsorb acetic acid from aqueous solutions, showing its ability to be applied as a bio-adsorbent.