Process Analysis by Pyrolysis of Açaí (Euterpe Oleracea, Mart.) Seeds: Reaction Products Yields, Physicochemical Properties and Chemical Composition

In this work, the influence of temperature on the yield of reaction products (bio-oil, gas, H2O, and coke), physicochemical properties (acid value, density, and kinematic viscosity) and chemical composition (hydrocarbons and oxygenates) of bio-oil obtained by pyrolysis of Açaí (Euterpe oleracea Mart.) seeds, a rich lignin-cellulose residue, has been systematically investigated in technical scale. The pyrolysis reaction carried out in a reactor of 143 L, operating in batch mode at 350, 400, and 450 ºC, 1.0 atmosphere. The distillation of bio-oil carried out in a laboratory scale (Vigreux) column according to the boiling temperature range of fossil fuels. The bio-oil and distillation fractions were physical-chemistry characterized for density, kinematic viscosity, acid value and refractive index. The chemical composition and qualitative analysis of chemical functions and/or groups present in bio-oils were determined by GC-MS and FT-IR. The yields of bio-oil, H2O and gas varied between 2.0 and 4.39% (wt.), 26.58 and 29.39% (wt.), and 18.76 and 30.56% (wt.), respectively, increasing with process temperature, while that of solid phase (coke) varied between 35.67 and 52.67% (wt.), decreasing with temperature. 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 bio-oil densities and kinematic viscosities ranged between 1.0236 and 1.0468 g/cm3, and 57.22 and 68.34 mm²/s, respectively, increasing with temperature, while bio-oil acid values varied between 70.26 and 92.87 mg KOH/g, decreasing with temperature. 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 FT-IR analysis identified in bio-oil chemical functions characteristics of hydrocarbons (alkanes, alkenes, and aromatics) and oxygenates (phenols, cresols, ketones, esters, carboxylic acids, aldehyds, and furans). The GC-MS analysis identified hydrocarbons and oxygenates as major chemical compounds in bio-oil, with chemical composition strongly dependent on pyrolysis temperature. The concentration of hydrocarbons in bio-oil varied between 13.505 and 21.542% (area.), increasing with temperature, while that of oxygenates varied between 78.458 and 86.495% (area.), decreasing with pyrolysis temperature. The composition of alkanes, alkenes, and aromatics increase with temperature, showing that higher temperatures favor the formation of hydrocarbons.