Diego Galvan

Kinetic and thermodynamic parameters of biodiesel oxidation with synthetic antioxidants: simplex centroid mixture design

Temperatures influence on biodiesel oxidation was evaluated by kinetic and thermodynamic data in biofuel from soybean oil and lard with synthetic antioxidants: butylatedhydroxyanisol (BHA), butylatedhydroxytoluene (BHT), tert-butylhydroquinone (TBHQ), and propylgallate (PG) by simplex centroid mixture design. The kinetic parameters ware obtained by Arrhenius equation and showed that addition of antioxidants in all tests increased activation energy (Ea) and that TBHQ and PG were more efficient and presented synergistic effect. BHT and BHA were the least efficient, as well as their mixtures. The thermodynamic activation parameters of the reactions, evaluated by the Eyring equation and based on the theory of the activated complex (ACT), indicated no spontaneous processes (∆G‡ > 0) with positive ∆H‡ values and positive and negative ∆S‡ values. The application of simplex centroid mixture design, using Ea as response, showed the optimised value of 174.46 kJ mol-1 for a mixture containing 33.33 and 66.67% of TBHQ and PG, respectively.

Study of oxidation kinetics of b100 biodiesel from soybean and pig fat: activation energy determination.

The quality of biodiesel is extremely important for its commercialization and use; oxidation of biodiesel is a critical factor because it decreases the fuel storage time. A commercial biodiesel was mixed with synthetic antioxidants, according to a simplex-centroid experimental mixture design, and its stability was evaluated through induction period and activation energy. In all trials, addition of antioxidants increased activation energy in the mixtures containing tertiary butylhydroquinone (TBHQ). When a mixture containing 50% TBHQ and 50% butylated hydroxyanisole was used, synergistic effect was observed, and the major activation energy obtained was 104.43 kJ mol-1.

Vinegar rice (Oryza sativa L.) produced by a submerged fermentation process from alcoholic fermented rice

Considering the limited availability of technology for the production of rice vinegar and also due to the potential consumer product market, this study aimed to use alcoholic fermented rice (rice wine (Oryza sativa L.)) for vinegar production. An alcoholic solution with 6.28% (w/v) ethanol was oxidized by a submerged fermentation process to produce vinegar. The process of acetic acid fermentation occurred at 30 ± 0.3°C in a FRINGS® Acetator (Germany) for the production of vinegar and was followed through 10 cycles. The vinegar had a total acidity of 6.85% (w/v), 0.17% alcohol (w/v), 1.26% (w/v) minerals and 1.78% (w/v) dry extract. The composition of organic acids present in rice vinegar was: cis-aconitic acid (6 mg/L), maleic acid (3 mg/L), trans-aconitic acid (3 mg/L), shikimic + succinic acid (4 mg/L), lactic acid (300 mg/L), formic acid (180 mg/L), oxalic acid (3 mg/L), fumaric acid (3 mg/L) and itaconic acid (1 mg/L).

Mathematical modeling of multicomponent NaCl and KCl diffusion process during the salting of pre-cooked champignon mushrooms

Wet salting is an old preservation method however the NaCl has been frequently associated to high blood pressure issues. The KCl has been used as partial replacement without affecting the acceptability of the final product. In this study, the simultaneous diffusion of NaCl and KCl in champignon mushrooms in static brine and brine under agitation was modeled based on the generalization of Ficks second diffusion law and simulated using the finite element method. Main and crossed diffusion coefficients, as well as the Biot number, were determined using the super modified simplex optimization method by means of percentage error minimization. Deviations between the simulated and experimental data were 5.78% for NaCl and 4.78% for KCl in static brine and 4.95% for NaCl and 4.35% for KCl in brine with agitation and, the main diffusion coefficients 2.692 × 10-10 m2s-1 for sodium and 2.953 × 10-10 m2s-1 for potassium were obtained.