Alexandre Santos | UFPR - Academia.edu (original) (raw)
Papers by Alexandre Santos
Brazilian Journal of Chemical Engineering, 2019
The Open Chemical Engineering Journal, 2018
Objective: Biodiesel is a renewable fuel considered as the main substitute for fossil fuels. Its ... more Objective: Biodiesel is a renewable fuel considered as the main substitute for fossil fuels. Its industrial production is mainly made by the transesterification reaction. In most processes, information on the production of biodiesel is essentially done by off-line measurements. Methods: However, for the purpose of control, where online monitoring of biodiesel conversion is required, this is not a satisfactory approach. An alternative technique to the online quantification of conversion is the near infrared (NIR) spectroscopy, which is fast and accurate. In this work, models for biodiesel reactions monitoring using NIR spectroscopy were developed based on the ester content during alkali-catalyzed transesterification reaction between soybean oil and ethanol. Gas chromatography with flame ionization detection was employed as the reference method for quantification. FT-NIR spectra were acquired with a transflectance probe. The models were developed using Partial Least Squares (PLS) regr...
Anais do XX Congresso Brasileiro de Engenharia Química, 2015
ABSTRACT O efeito do aquecimento micro-ondas foi avaliado em reações de polimerização em emulsão ... more ABSTRACT O efeito do aquecimento micro-ondas foi avaliado em reações de polimerização em emulsão dos monômeros: metacrilato de metila, estireno e acrilato de butila. As reações de polimerização de acrilato de butila foram conduzidas com e sem agente de transferência de cadeia. Foi observado aumento da taxa de reação quando utilizado micro-ondas, em comparação ao método de aquecimento convencional, para todos os monômeros estudados, exceto para a polimerização de acrilato de butila na ausência de agente de transferência de cadeia, em que houve retardo da reação sob ação das micro-ondas. O diâmetro médio das partículas poliméricas também foi afetado pelo modo de aquecimento, sendo que o efeito dependeu do sistema avaliado. Os resultados diferentes encontrados para cada monômero foram atribuídos as suas propriedades físicas e constantes cinéticas diferenciadas, que contribuem para um efeito micro-ondas específico sobre cada sistema. Palavras-chave: Micro-ondas; polimerização em emulsão; metacrilato de metila; estireno; acrilato de butila. Comparison of microwave effects in emulsion polymerizations using different monomers The effect of microwave irradiation heating was evaluated for emulsion polymerization reactions involving the monomers methyl methacrylate, styrene and butyl acrylate. Reactions with butyl acrylate were performed with and without a chain transfer agent. Reaction rate enhancements were observed in microwave-assisted reactions, in comparison with the conventional ones, for all the studied monomers. An exception was obtained in butyl acrylate polymerization, conducted without the chain transfer agent, which showed a decrease in reaction rate under microwave heating. The average diameter of the polymer particles was also affected by the heating method and varied in accordance with the evaluated system. The different results found for each monomer were ascribed to their different physical properties and kinetics constants, which lead to specific microwave effects on each system.
Materials Science and Engineering: C, 2009
Microwave irradiation has been an interesting alternative for heating systems and several chemica... more Microwave irradiation has been an interesting alternative for heating systems and several chemical reactions. In polymerization processes, microwaves can enhance reaction rates or improve specific characteristics of the formed polymer. In this work, the use of microwave irradiation in emulsion polymerization reactions has been studied, using a commercial microwave reactor, which is able to perform syntheses under controlled conditions of temperature and power. Methyl methacrylate emulsion polymerization reactions were faster, resulting in smaller polymer particles, in comparison to the conventional heating method (reactions in a jacketed reactor). Different effects were observed in the emulsion polymerization of butyl acrylate. To study the effect of high power microwave irradiation upon the emulsion polymerization, a pulsed irradiation strategy was developed, in which the samples were repeatedly heated within short intervals of time (about 27 s) at the maximum microwave power. A significant reduction of the total time of irradiation was observed in reactions carried out under the pulsed scheme, showing the kinetic advantages of using microwaves in emulsion polymerization processes.
European Polymer Journal, 2009
Anais do XX Congresso Brasileiro de Engenharia Química, 2015
CHIMIA International Journal for Chemistry
ABSTRACT
ABSTRACT In this work, the application of microwave technology is investigated for breaking water... more ABSTRACT In this work, the application of microwave technology is investigated for breaking water-in-crude oil emulsions focusing upon the identification of acidic species existing in the aqueous phase recovered by the microwave demulsification process. To accomplish this, a methodology for fractionation and characterization of acidic species based on chromatographic techniques has been developed. To evaluate the effect of operating conditions on the partitioning of acidic species, a set of variables was investigated including the type of heating, temperature and pH of the aqueous phase. According to the obtained results, the process temperature was the most important variable upon the partitioning of the acids. As expected, the increase of temperature favors the partitioning of a larger number of acidic species, including cyclic compounds of low molecular weight that were not extracted at low temperature. Based on information gathered in this study, new perspectives may be open up concerning the application of the microwave technology in the oil industry to achieve two relevant goals simultaneously: the separation of emulsions and the removal of acidic species of the oil phase.
Quimica Nova, Dec 1, 2007
Latin American applied research Pesquisa aplicada latino americana = Investigación aplicada latinoamericana
Macromolecular Reaction Engineering, 2014
Fuel, 2015
ABSTRACT Droplet size distribution (DSD) and water content (WC) are two parameters that affect th... more ABSTRACT Droplet size distribution (DSD) and water content (WC) are two parameters that affect the type/intensity of treatment of water-in-crude oil (W/O) emulsions in the production fields. Besides, the crude oil viscosity and emulsion stability are strongly dependent of DSD and WC. Several papers have reported different techniques for evaluation of these properties; however, most of them were based on experiments performed at conditions of temperature and mainly pressure far from those found in the production fields. In this work, we demonstrate that optical microscopy and standard PLS models can be combined for calibration of a Near Infrared (NIR) spectrophotometer with regard to DSD of W/O emulsions with different water contents. Additionally, the NIR calibration models were validated considering the prediction of the DSD and WC of a distinct crude oil not used during the calibration step. Then, a new apparatus for online monitoring of W/O emulsions at pressures up to 30 bar is presented. The proposed apparatus employed both techniques (optical microscopy and near infrared spectroscopy) installed in series in the pressurized pipeline. The results indicate that the proposed apparatus is efficient for online monitoring of pressurized emulsions with water contents up to 17 wt% and average diameter (D(4,3)) from 6 to 40 μm.
Macromolecular Symposia, 2008
Page 1. Coagulation of Carboxylic Acid-Functionalized Latexes Adeīlia Santos,1 Alexandre F. Santo... more Page 1. Coagulation of Carboxylic Acid-Functionalized Latexes Adeīlia Santos,1 Alexandre F. Santos,1 Claīudia Sayer,2 Pedro HH Arauījo,2 Montserrat Fortuny*1 Summary: In the present work, the stability of particles produced ...
Macromolecular Symposia, 2006
Page 1. Investigation of Stabilization and Kinetics in the Semi-Continuous Emulsion Copolymerizat... more Page 1. Investigation of Stabilization and Kinetics in the Semi-Continuous Emulsion Copolymerization of Vinyl Acetate and Butyl Acrylate using Carboxylic Monomers Pedro HH Arau´jo,1 Cla´udia Sayer,1 Elba Caldas,1 Alexandre F. Santos,2 Montserrat Fortuny*2 ...
Macromolecular Symposia, 2011
ABSTRACT Emulsion polymerization reactions were performed under microwave irradiation and convent... more ABSTRACT Emulsion polymerization reactions were performed under microwave irradiation and conventional heating using anionic or cationic initiators and surfactants. Microwave irradiation promoted higher reaction rates for both initiators and surfactants, in comparison with the conventional heating. The effect of high power microwave irradiation was studied using a method of cycles of heating and cooling, where rapid polymerization reactions were obtained. In the reactions with anionic initiator and surfactant, a decrease in the particle diameters was observed with microwave heating, and even smaller particles were obtained using high power microwave irradiation. Moreover, the decrease in the particle size was acompanied by an increase in the polymer molecular weight. On the other hand, these effects were not observed for reactions with cationic initiator and surfactant.
Macromolecular Symposia, 2004
Macromol. Symp. 2004, 206, 433^442 433 On-line Monitoring of Emulsion Polymerisation Using Conduc... more Macromol. Symp. 2004, 206, 433^442 433 On-line Monitoring of Emulsion Polymerisation Using Conductivity Measurements Christian Graillât, Alexandre Santos,1' José Carlos Pinto,1 Timothy F. McKenna*1 1LCPP-CNRS/ESCPE - Villeurbanne, France Programa de Engenharia ...
Brazilian Journal of Chemical Engineering, 2019
The Open Chemical Engineering Journal, 2018
Objective: Biodiesel is a renewable fuel considered as the main substitute for fossil fuels. Its ... more Objective: Biodiesel is a renewable fuel considered as the main substitute for fossil fuels. Its industrial production is mainly made by the transesterification reaction. In most processes, information on the production of biodiesel is essentially done by off-line measurements. Methods: However, for the purpose of control, where online monitoring of biodiesel conversion is required, this is not a satisfactory approach. An alternative technique to the online quantification of conversion is the near infrared (NIR) spectroscopy, which is fast and accurate. In this work, models for biodiesel reactions monitoring using NIR spectroscopy were developed based on the ester content during alkali-catalyzed transesterification reaction between soybean oil and ethanol. Gas chromatography with flame ionization detection was employed as the reference method for quantification. FT-NIR spectra were acquired with a transflectance probe. The models were developed using Partial Least Squares (PLS) regr...
Anais do XX Congresso Brasileiro de Engenharia Química, 2015
ABSTRACT O efeito do aquecimento micro-ondas foi avaliado em reações de polimerização em emulsão ... more ABSTRACT O efeito do aquecimento micro-ondas foi avaliado em reações de polimerização em emulsão dos monômeros: metacrilato de metila, estireno e acrilato de butila. As reações de polimerização de acrilato de butila foram conduzidas com e sem agente de transferência de cadeia. Foi observado aumento da taxa de reação quando utilizado micro-ondas, em comparação ao método de aquecimento convencional, para todos os monômeros estudados, exceto para a polimerização de acrilato de butila na ausência de agente de transferência de cadeia, em que houve retardo da reação sob ação das micro-ondas. O diâmetro médio das partículas poliméricas também foi afetado pelo modo de aquecimento, sendo que o efeito dependeu do sistema avaliado. Os resultados diferentes encontrados para cada monômero foram atribuídos as suas propriedades físicas e constantes cinéticas diferenciadas, que contribuem para um efeito micro-ondas específico sobre cada sistema. Palavras-chave: Micro-ondas; polimerização em emulsão; metacrilato de metila; estireno; acrilato de butila. Comparison of microwave effects in emulsion polymerizations using different monomers The effect of microwave irradiation heating was evaluated for emulsion polymerization reactions involving the monomers methyl methacrylate, styrene and butyl acrylate. Reactions with butyl acrylate were performed with and without a chain transfer agent. Reaction rate enhancements were observed in microwave-assisted reactions, in comparison with the conventional ones, for all the studied monomers. An exception was obtained in butyl acrylate polymerization, conducted without the chain transfer agent, which showed a decrease in reaction rate under microwave heating. The average diameter of the polymer particles was also affected by the heating method and varied in accordance with the evaluated system. The different results found for each monomer were ascribed to their different physical properties and kinetics constants, which lead to specific microwave effects on each system.
Materials Science and Engineering: C, 2009
Microwave irradiation has been an interesting alternative for heating systems and several chemica... more Microwave irradiation has been an interesting alternative for heating systems and several chemical reactions. In polymerization processes, microwaves can enhance reaction rates or improve specific characteristics of the formed polymer. In this work, the use of microwave irradiation in emulsion polymerization reactions has been studied, using a commercial microwave reactor, which is able to perform syntheses under controlled conditions of temperature and power. Methyl methacrylate emulsion polymerization reactions were faster, resulting in smaller polymer particles, in comparison to the conventional heating method (reactions in a jacketed reactor). Different effects were observed in the emulsion polymerization of butyl acrylate. To study the effect of high power microwave irradiation upon the emulsion polymerization, a pulsed irradiation strategy was developed, in which the samples were repeatedly heated within short intervals of time (about 27 s) at the maximum microwave power. A significant reduction of the total time of irradiation was observed in reactions carried out under the pulsed scheme, showing the kinetic advantages of using microwaves in emulsion polymerization processes.
European Polymer Journal, 2009
Anais do XX Congresso Brasileiro de Engenharia Química, 2015
CHIMIA International Journal for Chemistry
ABSTRACT
ABSTRACT In this work, the application of microwave technology is investigated for breaking water... more ABSTRACT In this work, the application of microwave technology is investigated for breaking water-in-crude oil emulsions focusing upon the identification of acidic species existing in the aqueous phase recovered by the microwave demulsification process. To accomplish this, a methodology for fractionation and characterization of acidic species based on chromatographic techniques has been developed. To evaluate the effect of operating conditions on the partitioning of acidic species, a set of variables was investigated including the type of heating, temperature and pH of the aqueous phase. According to the obtained results, the process temperature was the most important variable upon the partitioning of the acids. As expected, the increase of temperature favors the partitioning of a larger number of acidic species, including cyclic compounds of low molecular weight that were not extracted at low temperature. Based on information gathered in this study, new perspectives may be open up concerning the application of the microwave technology in the oil industry to achieve two relevant goals simultaneously: the separation of emulsions and the removal of acidic species of the oil phase.
Quimica Nova, Dec 1, 2007
Latin American applied research Pesquisa aplicada latino americana = Investigación aplicada latinoamericana
Macromolecular Reaction Engineering, 2014
Fuel, 2015
ABSTRACT Droplet size distribution (DSD) and water content (WC) are two parameters that affect th... more ABSTRACT Droplet size distribution (DSD) and water content (WC) are two parameters that affect the type/intensity of treatment of water-in-crude oil (W/O) emulsions in the production fields. Besides, the crude oil viscosity and emulsion stability are strongly dependent of DSD and WC. Several papers have reported different techniques for evaluation of these properties; however, most of them were based on experiments performed at conditions of temperature and mainly pressure far from those found in the production fields. In this work, we demonstrate that optical microscopy and standard PLS models can be combined for calibration of a Near Infrared (NIR) spectrophotometer with regard to DSD of W/O emulsions with different water contents. Additionally, the NIR calibration models were validated considering the prediction of the DSD and WC of a distinct crude oil not used during the calibration step. Then, a new apparatus for online monitoring of W/O emulsions at pressures up to 30 bar is presented. The proposed apparatus employed both techniques (optical microscopy and near infrared spectroscopy) installed in series in the pressurized pipeline. The results indicate that the proposed apparatus is efficient for online monitoring of pressurized emulsions with water contents up to 17 wt% and average diameter (D(4,3)) from 6 to 40 μm.
Macromolecular Symposia, 2008
Page 1. Coagulation of Carboxylic Acid-Functionalized Latexes Adeīlia Santos,1 Alexandre F. Santo... more Page 1. Coagulation of Carboxylic Acid-Functionalized Latexes Adeīlia Santos,1 Alexandre F. Santos,1 Claīudia Sayer,2 Pedro HH Arauījo,2 Montserrat Fortuny*1 Summary: In the present work, the stability of particles produced ...
Macromolecular Symposia, 2006
Page 1. Investigation of Stabilization and Kinetics in the Semi-Continuous Emulsion Copolymerizat... more Page 1. Investigation of Stabilization and Kinetics in the Semi-Continuous Emulsion Copolymerization of Vinyl Acetate and Butyl Acrylate using Carboxylic Monomers Pedro HH Arau´jo,1 Cla´udia Sayer,1 Elba Caldas,1 Alexandre F. Santos,2 Montserrat Fortuny*2 ...
Macromolecular Symposia, 2011
ABSTRACT Emulsion polymerization reactions were performed under microwave irradiation and convent... more ABSTRACT Emulsion polymerization reactions were performed under microwave irradiation and conventional heating using anionic or cationic initiators and surfactants. Microwave irradiation promoted higher reaction rates for both initiators and surfactants, in comparison with the conventional heating. The effect of high power microwave irradiation was studied using a method of cycles of heating and cooling, where rapid polymerization reactions were obtained. In the reactions with anionic initiator and surfactant, a decrease in the particle diameters was observed with microwave heating, and even smaller particles were obtained using high power microwave irradiation. Moreover, the decrease in the particle size was acompanied by an increase in the polymer molecular weight. On the other hand, these effects were not observed for reactions with cationic initiator and surfactant.
Macromolecular Symposia, 2004
Macromol. Symp. 2004, 206, 433^442 433 On-line Monitoring of Emulsion Polymerisation Using Conduc... more Macromol. Symp. 2004, 206, 433^442 433 On-line Monitoring of Emulsion Polymerisation Using Conductivity Measurements Christian Graillât, Alexandre Santos,1' José Carlos Pinto,1 Timothy F. McKenna*1 1LCPP-CNRS/ESCPE - Villeurbanne, France Programa de Engenharia ...