Navegando por Autor "Mattedi, Silvana"
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Artigo Effect of different variables in the solubility of ampicillin and corresponding solid phase(Elsevier, 2018-03-15) Chiavone Filho, Osvaldo; Bezerra, Ítalla Medeiros; Moreira, Leila Cabral; Mattedi, SilvanaAmpicillin belongs to the class of beta-lactam antibiotics, which corresponds the most prescribed antibiotics in medicine. This justifies the importance of elucidating the effect of several variables for the synthesis process (pH, temperature, co-solvent) on the behavior of the compounds involved in the enzymatic reaction. This paper aims to present new ampicillin solubility data in aqueous medium and the characterization of the solid phase of the antibiotic. In the phase equilibrium experiments it was considered the effect of pH (3 up to 7.5), temperature (283.15 K up to 298.15 K) and the ethanol concentration in the aqueous solution (varying between 0 and 70 wt% ethanol). The solubility curves deviate from U-shape solubility curves with respect to pH in the range of 0e70 wt%. This is due to ampicillin anhydrous becomes trihydrated molecule in the solid phase at alkaline pH region, changing the antibiotic properties significantly. This change in crystalline structure was confirmed by characterization of antibiotic solid phase carried out from thermogravimetric (TGA), Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) analyses. Dissociation constants have also been measured at the studied values of temperature and ethanol composition, using potentiometric titration. Finally, a thermodynamic model considering the ideal solution was applied to describe mathematically the solubility curves measured close to experimental uncertaintiesArtigo Optimization of a petroleum fractional distillation column using distop calibration and statistical methods(Brazilian Journal of Petroleum and Gas, 2021) Chiavone Filho, Osvaldo; Nóbrega, M. B. M. M.; Zimmermann, A. S.; Mattedi, SilvanaDistillation columns are important separation equipment that comprise most of the investment needed in a petroleum refining plant. Utilities and energy demands, though, are a concerning factor in the current economic and environmental scenario. The present work proposes a methodology to optimize the energy consumption of a crude oil distillation column using the Distop Calibration technique that allows faster convergence than the Tray-to-Tray method. The methodology presented involves process simulation, sensitivity analysis, factorial design, and the use of response surface methodology. Results show that it is possible to achieve significant gains by changing feed temperature and rectifying vapor flow, causing a relevant reduction in energy consumption. Hence, the methodology can be used as an optimization tool to increase energetic efficiencyArtigo Solid-liquid equilibrium data of amoxicillin and hydroxyphenylglycine in aqueous media(Brazilian Society of Chemical Engineering, 2013-03) Chiavone Filho, Osvaldo; Bezerra, Ítalla Medeiros; Mattedi, SilvanaThe enzymatic synthesis of amoxicillin is catalyzed by Penicillin G Acylase (PGA). As byproducts, hydroxyphenylglycine and alcohol are also formed from hydrolytic reactions and antibiotic synthesis, respectively. The design of this process should be directed to promote the synthesis reaction. At the same time, it is necessary to reduce the hydrolytic reaction of amoxicillin through its crystallization or separation from the reaction medium. This work presents measurements of solid-liquid equilibrium data for amoxicillin and hydroxyphenylglycine in water at different temperatures (283.15 – 298.15 K), pH (5.5 – 7.5) and ethanol composition (0 – 70 wt.%). This information is relevant to determine the conditions that offer the lowest solubility for the antibiotic, favoring its separation and purification. All solubility data were obtained using an analytical method with indirect determination by UV spectroscopy. Ideal thermodynamic modeling was applied to describe the experimental solubility data setsArtigo Solubility measurements of amoxicillin in mixtures of water and ethanol from 283.15 to 298.15 K(Elsevier, 2016-08-25) Chiavone Filho, Osvaldo; Félix, Ítalla Medeiros Bezerra; Moreira, Leila Cabral; Mattedi, SilvanaAmong the various types of existing antibiotics, amoxicillin stands out as a semi synthetic penicillin widely used on a world scale. The enzymatic synthesis of amoxicillin has arisen as an alternative to the drawbacks of conventional chemical synthesis. Nevertheless, to make it feasible a wide data basis of solubility is required in different conditions of industrial interest, aiming at crystallization and subsequent purification of the antibiotic. In this case, the variables such as temperature, pH and solvent composition are of fundamental importance. This work presents solubility data of amoxicillin in aqueous media using an analytical method. The solubility measurements were carried out at 283.15e298.15 K, varying the pH between 2 and 8, and ethanol composition up to 70 wt%. Dissociation constants have also been measured at the studied values of temperature and ethanol composition, using potentiometric titration. The values of pKa demonstrated to be in agreement with the solubility behavior observed experimentally. Thus, the ideal model based on pKa values has been applied as reference for the representation of the solubility data. Furthermore, the experimental solubility and pKa data sets can be used for correlation and thermodynamic modeling purposes