Fernanda C. Corazza

Kinetics of Solvent-Free Lipase-Catalyzed Glycerolysis of Olive Oil in Surfactant System

This work reports experimental data and kinetic modeling of solvent-free glycerolysis of olive oil using a commercial immobilized lipase (Novozym 435) in the presence of Triton X-100 surfactant for the production of monoacylglycerols (MAG) and diacylglycerols (DAG). The experiments were performed in batch mode evaluating the effects of temperature (30-70 degrees C), enzyme concentration (2.5-18 wt %), Triton X-100 concentration (10-20 wt %), and glycerol to oil molar ratio (3:1, 6:1, and 9:1). Experimental results showed that lipase-catalyzed solvent-free glycerolysis with the addition of Triton X-100 might be a potential alternative route to conventional organic solvent methods, as good conversions were obtained with relatively low enzyme concentrations (9 wt %) in short reaction times (240 min). The glycerolysis and hydrolysis parallel reactions were considered with rate constants estimated by minimizing a maximum likelihood function. A very satisfactory agreement between experimental data and model results was obtained, thus allowing a better understanding of the reaction kinetics.

Determinação experimental da viscosidade e condutividade térmica de óleos vegetais

This work reports experimental data of thermal conductivity and dynamic viscosity of the following refined vegetable oils: rice, soybean, corn oil, sunflower, cottonseed, and olive oil. Measurements of thermal properties were carried out in a cell coupled to a thermostatic bath in the temperature range of 20-70 °C, using a single-needle stainless steel sensor. It was experimentally observed that the thermal conductivity decreased slightly with increasing temperature for all samples investigated. The gravimetric method was employed for density data acquisition, and revealed no significant difference among the values obtained. The Brookfield apparatus was employed in measuring the dynamic viscosity and it was verified that a raise in temperature led to a sharp decrease for this property for all samples investigated.

Inulinase production in a batch bioreactor using agroindustrial residues as the substrate: experimental data and modeling.

The production of inulinase employing agroindustrial residues as the substrate is a good alternative to reduce production costs and to minimize the environmental impact of disposing these residues in the environment. This study focused on the use of a phenomenological model and an artificial neural network (ANN) to simulate the inulinase production during the batch cultivation of the yeast Kluyveromyces marxianus NRRL Y-7571, employing a medium containing agroindustrial residues such as molasses, corn steep liquor and yeast extract. It was concluded that due to the complexity of the medium composition it was rather difficult to use a phenomenological model with sufficient accuracy. For this reason, an alternative and more cost-effective methodology based on ANN was adopted. The predictive capacity of the ANN was superior to that of the phenomenological model, indicating that the neural network approach could be used as an alternative in the predictive modeling of complex batch cultivations.

Influência da temperatura na solubilidade de beta-caroteno em solventes orgânicos à pressão ambiente

This work reports experimental data of the solubility of b-carotene in pure acetone, ethyl acetate, ethanol and dichloromethane and in mixtures of these organic solvents in the temperature range of 10 to 60 °C under ambient pressure. The gravimetric method was employed to determine the solubility, using glass equilibrium cells. The results showed that the best solvents were those having solubility parameter values close to that of the solute. It was found that raising the temperature caused the solute solubility values for both pure and solvent mixtures to increase under all the experimental conditions. Moreover, no synergetic effects were observed on the solubility of b-carotene in solvent mixtures compared to pure solvents in the temperature range investigated. The UNIFAC model proved to be useful in predicting the solubility data.

A subdivision algorithm for phase equilibrium calculations at high pressures

Phase equilibrium calculations at high pressures have been a continuous challenge for scientists and engineers. Traditionally, this task has been performed by solving a system of nonlinear algebraic equations originating from isofugacity equations. The reliability and accuracy of the solutions are strongly dependent on the initial guess, especially due to the fact that the phase equilibrium problems frequently have multiple roots. This work is focused on the application of a subdivision algorithm for thermodynamic calculations at high pressures. The subdivision algorithm consists in the application of successive subdivisions at a given initial interval (rectangle) of variables and a systematic test to verify the existence of roots in each subinterval. If the interval checked passes in the test, then it is retained; otherwise it is discharged. The algorithm was applied for vapor-liquid, solid-fluid and solid-vapor-liquid equilibrium as well as for phase stability calculations for binary and multicomponent systems. The results show that the proposed algorithm was capable of finding all roots of all high-pressure thermodynamic problems investigated, independent of the initial guess used.

High-pressure cloud point data for the system glycerol + olive oil + n-butane + AOT

This work reports high-pressure cloud point data for the quaternary system glycerol + olive oil + n-butane + AOT surfactant. The static synthetic method, using a variable-volume view cell, was employed for obtaining the experimental data at pressures up to 27 MPa. The effects of glycerol/olive oil concentration and surfactant addition on the pressure transition values were evaluated in the temperature range from 303 K to 343 K. For the system investigated, vapor-liquid (VLE), liquid-liquid (LLE) and vapor-liquid-liquid (VLLE) equilibrium were recorded. It was experimentally observed that, at a given temperature and surfactant content, an increase in the concentration of glycerol/oil ratio led to a pronounced increase in the slope of the liquid-liquid coexistence curve. A comparison with results reported for the same system but using propane as solvent showed that much lower pressure transition values are obtained when using n-butane.