The overall goal of this experiment was to detect whether kinetic modeling can explain effects of temperature, acid concentration, time and solid contents on the production of glucose by concentrated acid hydrolysis of walnut green skin. For this purpose, sulfuric acid concentration of 20, 40 and 60% (w/w), processing temperature of 65, 80 and 90°C, reaction time of 120, 180 and 240 min and solid content of 5, 10 and 15% (w/w) were used as hydrolysis conditions. High performance liquid chromatography (HPLC) was used to analyze the products. The process was modeled by first-order irreversible reaction in series and kinetic constant, relating reaction time to glucose released. To relate temperature with kinetic constant and calculate activation energy, Arrhenius equation was employed. Optimal conditions occurred at 40% H2SO4, 90°C and 15% solid content for 285 min, which yielded a solution with 10.72 g glucose/L. In these conditions, 45% of the cellulose was hydrolyzed.
Key words: Kinetic modeling, fermentable sugar, acid hydrolysis, walnut green skin.
NOMENCLATURE: α = Ratio between susceptible polymer to total; a = Regression parameter; Ac0= Potential concentration of acetyl group; Ac = Acetic acid concentration; CG0= Initial composition for Cellulose; Cmax= Maximum concentration of Glucose; E= Activation energy; k1 = Rate of conversion of polymer; k2= Rate of decomposition of monomer; tmax= Time for maximum concentration; M = The monomer concentration; n = Regression parameter; P0= The polymer concentration;R = Gas constant; T = Reaction temperature; R2= Regression parameter; WGS= Walnut green skin; WSR = Water solid ratio; g/L = gram / liter; w/w% = Percentage weight/weight; TT= Thousand ton.
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