Carmen Guedes - Academia.edu (original) (raw)

Papers by Carmen Guedes

Research paper thumbnail of Characterization of Paramagnetic Species in Seeds by Electron Paramagnetic Resonance (EPR)

Renewable energy & power quality journal, Mar 1, 2013

Research paper thumbnail of Obtaining of Additive for Aviation Kerosene from a Co-Product of the Sugar and Alcohol Industry

Revista Virtual de Química, 2019

Aviation industry consumes about 177 billion liters of kerosene, moving more than 25,000 aircraft... more Aviation industry consumes about 177 billion liters of kerosene, moving more than 25,000 aircraft and 6 billion passengers. To achieve this, civil aviation generated around 781 million tons of CO2 in 2015, corresponding to 2 % of all anthropogenic emissions of this greenhouse gas, with all the energy required coming from fossil sources. This work aims to synthesize 2-isopropyl-5-methyl-2-hexen-1-ol from fusel oil, a sugarcane industry co-product, for the partial replacement of aviation kerosene. The additive obtained mixed in 3 %, 5 % and 10 % contents in Jet A1 kerosene (QAV-1) exhibited viscosity (1,78 mm 2 s-1), flash point (>40 °C) and performance (<-54 °C) the current international standards, in addition to a potential biodegradability superior to fossil kerosene and a calorific value estimated in the mixture compatible with those required by ANP n° 37.

Research paper thumbnail of Utilization of Glycerin from Biodiesel Production in Textile Waste Recycling

Revista Virtual de Química, 2017

Research paper thumbnail of Extraction, characterization, and optimization of biodiesel production from Pachira aquatica Aubl

Research, Society and Development, 2021

Given the great energy demand to meet the needs of modern society, it is essential that new alter... more Given the great energy demand to meet the needs of modern society, it is essential that new alternatives to replace fossil diesel are studied. And biodiesel is an alternative that has been gaining prominence on the world stage, mainly with the use of vegetable oils with a high lipid content, such as Pachira aquatica Aubl, also known as munguba. Given the above, the objective of this work was to extract the oil from the seeds of Pachira aquatica, evaluate the physicochemical characteristics of the oil and define the best conditions for catalytic mixing with temperature variation in the production of biodiesel from the oil obtained. Thus, the acidity index, saponification, refraction, peroxide, water content and fatty acid profile of the oil were evaluated. Fourteen treatments of biodiesel produced with different amounts of sulfuric acid and temperature were evaluated. They were analyzed for water content, specific mass, kinematic viscosity at 40 ºC, refractive index and ester content...

Research paper thumbnail of 8 Crude Oil by EPR

Electron paramagnetic resonance (EPR) or Electron spin resonance (ESR) is a high resolution spect... more Electron paramagnetic resonance (EPR) or Electron spin resonance (ESR) is a high resolution spectroscopy that consists in energy absorption of microwave, for electron spin, in the presence of a magnetic field (Ikeya, 1993). As the name itself suggests, EPR is applied in samples containing some paramagnetic species or used as an investigative method, to verify the presence of some paramagnetic species. Paramagnetism is characteristic of species with a total magnetic moment different from zero.

Research paper thumbnail of Aviation Fuels and Biofuels

Renewable Energy - Resources, Challenges and Applications, 2020

Research paper thumbnail of Cryopreservation of Chlorella vulgaris Using Different Cryoprotectant Agents

Journal of Agricultural Science, 2020

The objective of this study is to evaluate the cryopreservation of Chlorella vulgaris using diffe... more The objective of this study is to evaluate the cryopreservation of Chlorella vulgaris using different substances. The C. vulgaris was cultured in medium MH, the microalgae were grown under a 12:12 h light: dark photoperiod, illumination with 40 W led lamps, and a controlled temperature of 28±1 ºC. C.vulgaris was cultured for 15 days and the culture was aliquoted into 3-mL cryogenic tubes. The 3-mL aliquot was centrifuged, the supernatant was discarded, and the pellet was resuspended in different cryoprotectant solutions, T1-PVS1, T2-PVS2, T3-PVS2 (1% phloroglucinol), T4 (2 M glycerol), and T5 (5% methanol). The samples were rapidly frozen in liquid nitrogen (-196 °C) and analyzed after 15, 150, and 300 days of freezing. Cell viability was determined in cultures grown for 20 days. The only effective treatment was T5, which promoted the growth of thawed cultures in both solid and liquid media. After 15 days of freezing in liquid nitrogen and 20 days of culture growth, the number of vi...

Research paper thumbnail of Obtaining of Additive for Aviation Kerosene from a Co-Product of the Sugar and Alcohol Industry

Revista Virtual de Química, 2019

Aviation industry consumes about 177 billion liters of kerosene, moving more than 25,000 aircraft... more Aviation industry consumes about 177 billion liters of kerosene, moving more than 25,000 aircraft and 6 billion passengers. To achieve this, civil aviation generated around 781 million tons of CO2 in 2015, corresponding to 2 % of all anthropogenic emissions of this greenhouse gas, with all the energy required coming from fossil sources. This work aims to synthesize 2-isopropyl-5-methyl-2-hexen-1-ol from fusel oil, a sugarcane industry co-product, for the partial replacement of aviation kerosene. The additive obtained mixed in 3 %, 5 % and 10 % contents in Jet A1 kerosene (QAV-1) exhibited viscosity (1,78 mm 2 s-1), flash point (>40 °C) and performance (<-54 °C) the current international standards, in addition to a potential biodegradability superior to fossil kerosene and a calorific value estimated in the mixture compatible with those required by ANP n° 37.

Research paper thumbnail of Análise de Hidrocarbonetos Policíclicos Aromáticos (HPAs) em solos utilizando agitação ultra-sônica, tubo aquecedor/minicondensador e cromatografia gasosa

Semina: Ciências Exatas e Tecnológicas, 2006

Research paper thumbnail of EPR and Fluorescence Spectroscopy in the Photodegradation Study of Arabian and Colombian Crude Oils

International Journal of Photoenergy, 2006

EPR and fluorescence spectroscopy were used to evaluate the degradation of crude oils of differen... more EPR and fluorescence spectroscopy were used to evaluate the degradation of crude oils of different origins that were submitted to photochemical weathering under tropical conditions. The EPR spectra obtained showed signals of the paramagnetic species: the vanadylVO2+ion and organic free radicals. A decrease in linewidth of free radical signals was observed for both oils irradiated for 100 hours with sunlight of 350 W/m2. The reduction in the linewidth of the free radical of 9.8% in Arabian oil and 18.5% in Colombian oil, as well as the decrease in radical numbers, indicated photochemical degradation, especially in Colombian oil. The linewidth narrowing corresponding to free radicals in the irradiated oils occurred due to the rearrangement among radicals and aromatic carbon consumption. The irradiated oils showed a reduction in the relative intensity of fluorescence of the aromatics with high molecular mass, polar aromatics, and asphaltene. The fluorescent fraction was reduced by 61% ...

Research paper thumbnail of Otimização das condições de obtenção de biodiesel de óleo de soja utilizando o delineamento experimental de mistura

Semina: Ciências Exatas e Tecnológicas, 2010

A otimização do rendimento da reação de transesterificação de obtenção do biodiesel B100 foi estu... more A otimização do rendimento da reação de transesterificação de obtenção do biodiesel B100 foi estudada utilizando hidróxido de sódio, hidróxido de potássio, metóxido e etóxido de sódio como catalisadores. Foi aplicado o delineamento experimental de mistura simplex centróide e os resultados da otimização indicaram, com metanol, um rendimento de 97,61% quando se usa 30,77% de NaOH e 69,23% de metóxido de sódio e, com etanol, um rendimento de 89,32% quando se usa apenas o etóxido de sódio. A análise cromatográfica indicou que o biodiesel B100 obtido encontra-se dentro dos parâmetros estabelecidos pela Legislação Brasileira. Palavras-chave: Biodiesel. Transesterificação. Delineamento de mistura.

Research paper thumbnail of <b>Application of the simplex-centroid design with process variable in the optimization of production conditions of B100 biodiesel from sunflower oil

Acta Scientiarum. Technology, 2014

Research paper thumbnail of Comparação dos métodos de determinação da estabilidade oxidativa de biodiesel B100, em mistura com antioxidantes sintéticos: aplicação do delineamento simplex-centroide com variável de processo

Química Nova, 2013

Recebido em 12/4/12; aceito em 14/8/12; publicado na web em 27/11/12 COMPARISON OF METHODS FOR DE... more Recebido em 12/4/12; aceito em 14/8/12; publicado na web em 27/11/12 COMPARISON OF METHODS FOR DETERMINATION OF OXIDATIVE STABILITY OF B100 BIODIESEL MIXED WITH SYNTHETIC ANTIOXIDANTS. APPLICATION OF SIMPLEX-CENTROID DESIGN WITH PROCESS VARIABLE. The Rancimat and accelerated stove tests were used to determine the oxidative stability of B100 biodiesel mixed with synthetic antioxidants. The predictive equations, with process variable, were obtained by applying a simplex-centroid design. Regardless of the antioxidant used, all assays carried out with the accelerated stove test presented storage time longer than 177.88 d, the greatest value obtained by applying the Rancimat test. The t test, applied to the parameters containing the process variable, showed a statistically significant difference (at the level of 5%) between the methods used.

Research paper thumbnail of Aplicação do delineamento simplex-centroide no estudo da cinética da oxidação de biodiesel B100 em mistura com antioxidantes sintéticos

Química Nova, 2010

THE SIMPLEX-CENTROID DESIGN APPLIED TO STUDY OF THE KINETICS OF THE OXIDATION OF B100 BIODIESEL I... more THE SIMPLEX-CENTROID DESIGN APPLIED TO STUDY OF THE KINETICS OF THE OXIDATION OF B100 BIODIESEL IN BLEND WITH SYNTHETIC ANTIOXIDANTS. Antioxidants are an alternative to prevent or slow the degradation of the biofuel. In this study, it was evaluated the oxidative stability of B100 biodiesel from soybean oil in the presence of three commercial synthetic antioxidants, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ), pure or blended, from the experimental design of simplex-centroid mixture. The reaction order and rate constant were also calculated for all tests. The treatment containing pure TBHQ proved to be the most effective, proven by design, the optimum mix obtained and the rate constant. Binary and ternary mixtures containing TBHQ also showed appreciable antioxidant effect.

Research paper thumbnail of Photochemical weathering study of Brazilian petroleum by EPR spectroscopy

Marine Chemistry, 2003

The EPR spectrum of the petroleum of the Campos Basin, Rio de Janeiro, Brazil shows signals chara... more The EPR spectrum of the petroleum of the Campos Basin, Rio de Janeiro, Brazil shows signals characteristic of free radical, vanadyl (VO 2 +) and iron III ion (Fe 3 +). The value of g = 2.0045 F 0.0001 corresponds to free radical species with a peak-topeak line width DH = 4.64 F 0.03 G. The g spectroscopic factor suggests the presence of free radicals in aromatic systems containing carbon, nitrogen and oxygen. Dg o (chemical shift) = 21.6 F 0.1 determined for the VO 2 + species characterizes porphyrin and non-porphyrin (with sulfur) complexes in asphaltenes of the crude oil. The species observed with g = 2.16 F 0.01 corresponds to Fe 3 + in Fe 2 O 3 , and therefore is not part of the molecular structure of the oil under study. The photochemical weathering of Brazilian oil as a film over seawater was monitored by EPR. After 100 h of solar irradiation the line width of the radical decreased by 10.6%, indicating rearrangement among radicals. The Dg o value for VO 2 + in the irradiated oil decreased to 19.5 F 0.1, characterizing degradation of porphyrin systems. Solar irradiation promotes the partial destruction of the asphaltenic fraction of the oil.

Research paper thumbnail of Genotoxic evaluation of an industrial effluent from an oil refinery using plant and animal bioassays

Genetics and Molecular Biology, 2010

Polycyclic aromatic hydrocarbons (PAHs) are genotoxic chemicals commonly found in effluents from ... more Polycyclic aromatic hydrocarbons (PAHs) are genotoxic chemicals commonly found in effluents from oil refineries. Bioassays using plants and cells cultures can be employed for assessing environmental safety and potential genotoxicity. In this study, the genotoxic potential of an oil refinery effluent was analyzed by means of micronucleus (MN) testing of Alium cepa, which revealed no effect after 24 h of treatment. On the other hand, primary lesions in the DNA of rat (Rattus norvegicus) hepatoma cells (HTC) were observed through comet assaying after only 2 h of exposure. On considering the capacity to detect DNA damage of a different nature and of these cells to metabolize xenobiotics, we suggest the association of the two bioassays with these cell types, plant (Allium cepa) and mammal (HTC) cells, for more accurately assessing genotoxicity in environmental samples.

Research paper thumbnail of EPR, FT-IR and XRD investigation of soils from Paraná, Brazil

Applied Clay Science, 2011

Samples of Araucária area soil from Paraná state, Brazil, were separated by particle size fractio... more Samples of Araucária area soil from Paraná state, Brazil, were separated by particle size fractionation and investigated by electron paramagnetic resonance (EPR) in X-Band of 9.5GHz at room temperature and 77K, infra-red spectroscopy and X-ray diffractometry. The paramagnetic species in the soil samples were identified by comparison with EPR spectra of some minerals studied recently by our group, several soil

Research paper thumbnail of Tratamento de Solo Contaminado com Petróleo Utilizando Tensoativos e Peróxido de Hidrogênio

Semina: Ciências Exatas e Tecnológicas, 2010

Research paper thumbnail of Potential of babassu biofuels use as aviation fuel

Research, Society and Development, 2022

Through a review of the bibliographic base was identified the potential and difficulties of using... more Through a review of the bibliographic base was identified the potential and difficulties of using biofuels based on babassu culture for use as aviation biofuel. Babassu palm is one of the most important crops for family farming in the north and northeast of Brazil due to its vast use potential. From babassu oil, by transesterification, good quality biodiesel can be obtained. However, it does not have the properties necessary to be used as aviation biofuel. Researches with biofuels from this culture and cultures with a similar organic profile were analyzed pointing out the feasibility of these biofuels as a mixture in aviation kerosene, nevertheless, these biofuels present several problems when used alone. Among the physical-chemical properties analyzed, the freezing point was a critical factor for not using these biofuels. This review points out the best results to improve the physicochemical properties of babassu biofuels to use as aviation fuel and present an important social fact...

Research paper thumbnail of Lipase Production by Botryosphaeria ribis EC-01 on Soybean and Castorbean Meals: Optimization, Immobilization, and Application for Biodiesel Production

Applied Biochemistry and Biotechnology, 2013

The effects of soybean and castorbean meals were evaluated separately, and in combinations at dif... more The effects of soybean and castorbean meals were evaluated separately, and in combinations at different ratios, as substrates for lipase production by Botryosphaeria ribis EC-01 in submerged fermentation using only distilled water. The addition of glycerol analytical grade (AG) and glycerol crude (CG) to soybean and castorbean meals separately and in combination, were also examined for lipase production. Glycerol-AG increased enzyme production, whereas glycerol-CG decreased it. A 2(4) factorial design was developed to determine the best concentrations of soybean meal, castorbean meal, glycerol-AG, and KH2PO4 to optimize lipase production by B. ribis EC-01. Soybean meal and glycerol-AG had a significant effect on lipase production, whereas castorbean meal did not. A second treatment (2(2) factorial design central composite) was developed, and optimal lipase production (4,820 U/g of dry solids content (ds)) was obtained when B. ribis EC-01 was grown on 0.5 % (w/v) soybean meal and 5.2 % (v/v) glycerol in distilled water, which was in agreement with the predicted value (4,892 U/g ds) calculated by the model. The unitary cost of lipase production determined under the optimized conditions developed ranged from US$0.42 to 0.44 based on nutrient costs. The fungal lipase was immobilized onto Celite and showed high thermal stability and was used for transesterification of soybean oil in methanol (1:3) resulting in 36 % of fatty acyl alkyl ester content. The apparent K m and V max were determined and were 1.86 mM and 14.29 μmol min(-1) mg(-1), respectively.

Research paper thumbnail of Characterization of Paramagnetic Species in Seeds by Electron Paramagnetic Resonance (EPR)

Renewable energy & power quality journal, Mar 1, 2013

Research paper thumbnail of Obtaining of Additive for Aviation Kerosene from a Co-Product of the Sugar and Alcohol Industry

Revista Virtual de Química, 2019

Aviation industry consumes about 177 billion liters of kerosene, moving more than 25,000 aircraft... more Aviation industry consumes about 177 billion liters of kerosene, moving more than 25,000 aircraft and 6 billion passengers. To achieve this, civil aviation generated around 781 million tons of CO2 in 2015, corresponding to 2 % of all anthropogenic emissions of this greenhouse gas, with all the energy required coming from fossil sources. This work aims to synthesize 2-isopropyl-5-methyl-2-hexen-1-ol from fusel oil, a sugarcane industry co-product, for the partial replacement of aviation kerosene. The additive obtained mixed in 3 %, 5 % and 10 % contents in Jet A1 kerosene (QAV-1) exhibited viscosity (1,78 mm 2 s-1), flash point (>40 °C) and performance (<-54 °C) the current international standards, in addition to a potential biodegradability superior to fossil kerosene and a calorific value estimated in the mixture compatible with those required by ANP n° 37.

Research paper thumbnail of Utilization of Glycerin from Biodiesel Production in Textile Waste Recycling

Revista Virtual de Química, 2017

Research paper thumbnail of Extraction, characterization, and optimization of biodiesel production from Pachira aquatica Aubl

Research, Society and Development, 2021

Given the great energy demand to meet the needs of modern society, it is essential that new alter... more Given the great energy demand to meet the needs of modern society, it is essential that new alternatives to replace fossil diesel are studied. And biodiesel is an alternative that has been gaining prominence on the world stage, mainly with the use of vegetable oils with a high lipid content, such as Pachira aquatica Aubl, also known as munguba. Given the above, the objective of this work was to extract the oil from the seeds of Pachira aquatica, evaluate the physicochemical characteristics of the oil and define the best conditions for catalytic mixing with temperature variation in the production of biodiesel from the oil obtained. Thus, the acidity index, saponification, refraction, peroxide, water content and fatty acid profile of the oil were evaluated. Fourteen treatments of biodiesel produced with different amounts of sulfuric acid and temperature were evaluated. They were analyzed for water content, specific mass, kinematic viscosity at 40 ºC, refractive index and ester content...

Research paper thumbnail of 8 Crude Oil by EPR

Electron paramagnetic resonance (EPR) or Electron spin resonance (ESR) is a high resolution spect... more Electron paramagnetic resonance (EPR) or Electron spin resonance (ESR) is a high resolution spectroscopy that consists in energy absorption of microwave, for electron spin, in the presence of a magnetic field (Ikeya, 1993). As the name itself suggests, EPR is applied in samples containing some paramagnetic species or used as an investigative method, to verify the presence of some paramagnetic species. Paramagnetism is characteristic of species with a total magnetic moment different from zero.

Research paper thumbnail of Aviation Fuels and Biofuels

Renewable Energy - Resources, Challenges and Applications, 2020

Research paper thumbnail of Cryopreservation of Chlorella vulgaris Using Different Cryoprotectant Agents

Journal of Agricultural Science, 2020

The objective of this study is to evaluate the cryopreservation of Chlorella vulgaris using diffe... more The objective of this study is to evaluate the cryopreservation of Chlorella vulgaris using different substances. The C. vulgaris was cultured in medium MH, the microalgae were grown under a 12:12 h light: dark photoperiod, illumination with 40 W led lamps, and a controlled temperature of 28±1 ºC. C.vulgaris was cultured for 15 days and the culture was aliquoted into 3-mL cryogenic tubes. The 3-mL aliquot was centrifuged, the supernatant was discarded, and the pellet was resuspended in different cryoprotectant solutions, T1-PVS1, T2-PVS2, T3-PVS2 (1% phloroglucinol), T4 (2 M glycerol), and T5 (5% methanol). The samples were rapidly frozen in liquid nitrogen (-196 °C) and analyzed after 15, 150, and 300 days of freezing. Cell viability was determined in cultures grown for 20 days. The only effective treatment was T5, which promoted the growth of thawed cultures in both solid and liquid media. After 15 days of freezing in liquid nitrogen and 20 days of culture growth, the number of vi...

Research paper thumbnail of Obtaining of Additive for Aviation Kerosene from a Co-Product of the Sugar and Alcohol Industry

Revista Virtual de Química, 2019

Aviation industry consumes about 177 billion liters of kerosene, moving more than 25,000 aircraft... more Aviation industry consumes about 177 billion liters of kerosene, moving more than 25,000 aircraft and 6 billion passengers. To achieve this, civil aviation generated around 781 million tons of CO2 in 2015, corresponding to 2 % of all anthropogenic emissions of this greenhouse gas, with all the energy required coming from fossil sources. This work aims to synthesize 2-isopropyl-5-methyl-2-hexen-1-ol from fusel oil, a sugarcane industry co-product, for the partial replacement of aviation kerosene. The additive obtained mixed in 3 %, 5 % and 10 % contents in Jet A1 kerosene (QAV-1) exhibited viscosity (1,78 mm 2 s-1), flash point (>40 °C) and performance (<-54 °C) the current international standards, in addition to a potential biodegradability superior to fossil kerosene and a calorific value estimated in the mixture compatible with those required by ANP n° 37.

Research paper thumbnail of Análise de Hidrocarbonetos Policíclicos Aromáticos (HPAs) em solos utilizando agitação ultra-sônica, tubo aquecedor/minicondensador e cromatografia gasosa

Semina: Ciências Exatas e Tecnológicas, 2006

Research paper thumbnail of EPR and Fluorescence Spectroscopy in the Photodegradation Study of Arabian and Colombian Crude Oils

International Journal of Photoenergy, 2006

EPR and fluorescence spectroscopy were used to evaluate the degradation of crude oils of differen... more EPR and fluorescence spectroscopy were used to evaluate the degradation of crude oils of different origins that were submitted to photochemical weathering under tropical conditions. The EPR spectra obtained showed signals of the paramagnetic species: the vanadylVO2+ion and organic free radicals. A decrease in linewidth of free radical signals was observed for both oils irradiated for 100 hours with sunlight of 350 W/m2. The reduction in the linewidth of the free radical of 9.8% in Arabian oil and 18.5% in Colombian oil, as well as the decrease in radical numbers, indicated photochemical degradation, especially in Colombian oil. The linewidth narrowing corresponding to free radicals in the irradiated oils occurred due to the rearrangement among radicals and aromatic carbon consumption. The irradiated oils showed a reduction in the relative intensity of fluorescence of the aromatics with high molecular mass, polar aromatics, and asphaltene. The fluorescent fraction was reduced by 61% ...

Research paper thumbnail of Otimização das condições de obtenção de biodiesel de óleo de soja utilizando o delineamento experimental de mistura

Semina: Ciências Exatas e Tecnológicas, 2010

A otimização do rendimento da reação de transesterificação de obtenção do biodiesel B100 foi estu... more A otimização do rendimento da reação de transesterificação de obtenção do biodiesel B100 foi estudada utilizando hidróxido de sódio, hidróxido de potássio, metóxido e etóxido de sódio como catalisadores. Foi aplicado o delineamento experimental de mistura simplex centróide e os resultados da otimização indicaram, com metanol, um rendimento de 97,61% quando se usa 30,77% de NaOH e 69,23% de metóxido de sódio e, com etanol, um rendimento de 89,32% quando se usa apenas o etóxido de sódio. A análise cromatográfica indicou que o biodiesel B100 obtido encontra-se dentro dos parâmetros estabelecidos pela Legislação Brasileira. Palavras-chave: Biodiesel. Transesterificação. Delineamento de mistura.

Research paper thumbnail of <b>Application of the simplex-centroid design with process variable in the optimization of production conditions of B100 biodiesel from sunflower oil

Acta Scientiarum. Technology, 2014

Research paper thumbnail of Comparação dos métodos de determinação da estabilidade oxidativa de biodiesel B100, em mistura com antioxidantes sintéticos: aplicação do delineamento simplex-centroide com variável de processo

Química Nova, 2013

Recebido em 12/4/12; aceito em 14/8/12; publicado na web em 27/11/12 COMPARISON OF METHODS FOR DE... more Recebido em 12/4/12; aceito em 14/8/12; publicado na web em 27/11/12 COMPARISON OF METHODS FOR DETERMINATION OF OXIDATIVE STABILITY OF B100 BIODIESEL MIXED WITH SYNTHETIC ANTIOXIDANTS. APPLICATION OF SIMPLEX-CENTROID DESIGN WITH PROCESS VARIABLE. The Rancimat and accelerated stove tests were used to determine the oxidative stability of B100 biodiesel mixed with synthetic antioxidants. The predictive equations, with process variable, were obtained by applying a simplex-centroid design. Regardless of the antioxidant used, all assays carried out with the accelerated stove test presented storage time longer than 177.88 d, the greatest value obtained by applying the Rancimat test. The t test, applied to the parameters containing the process variable, showed a statistically significant difference (at the level of 5%) between the methods used.

Research paper thumbnail of Aplicação do delineamento simplex-centroide no estudo da cinética da oxidação de biodiesel B100 em mistura com antioxidantes sintéticos

Química Nova, 2010

THE SIMPLEX-CENTROID DESIGN APPLIED TO STUDY OF THE KINETICS OF THE OXIDATION OF B100 BIODIESEL I... more THE SIMPLEX-CENTROID DESIGN APPLIED TO STUDY OF THE KINETICS OF THE OXIDATION OF B100 BIODIESEL IN BLEND WITH SYNTHETIC ANTIOXIDANTS. Antioxidants are an alternative to prevent or slow the degradation of the biofuel. In this study, it was evaluated the oxidative stability of B100 biodiesel from soybean oil in the presence of three commercial synthetic antioxidants, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ), pure or blended, from the experimental design of simplex-centroid mixture. The reaction order and rate constant were also calculated for all tests. The treatment containing pure TBHQ proved to be the most effective, proven by design, the optimum mix obtained and the rate constant. Binary and ternary mixtures containing TBHQ also showed appreciable antioxidant effect.

Research paper thumbnail of Photochemical weathering study of Brazilian petroleum by EPR spectroscopy

Marine Chemistry, 2003

The EPR spectrum of the petroleum of the Campos Basin, Rio de Janeiro, Brazil shows signals chara... more The EPR spectrum of the petroleum of the Campos Basin, Rio de Janeiro, Brazil shows signals characteristic of free radical, vanadyl (VO 2 +) and iron III ion (Fe 3 +). The value of g = 2.0045 F 0.0001 corresponds to free radical species with a peak-topeak line width DH = 4.64 F 0.03 G. The g spectroscopic factor suggests the presence of free radicals in aromatic systems containing carbon, nitrogen and oxygen. Dg o (chemical shift) = 21.6 F 0.1 determined for the VO 2 + species characterizes porphyrin and non-porphyrin (with sulfur) complexes in asphaltenes of the crude oil. The species observed with g = 2.16 F 0.01 corresponds to Fe 3 + in Fe 2 O 3 , and therefore is not part of the molecular structure of the oil under study. The photochemical weathering of Brazilian oil as a film over seawater was monitored by EPR. After 100 h of solar irradiation the line width of the radical decreased by 10.6%, indicating rearrangement among radicals. The Dg o value for VO 2 + in the irradiated oil decreased to 19.5 F 0.1, characterizing degradation of porphyrin systems. Solar irradiation promotes the partial destruction of the asphaltenic fraction of the oil.

Research paper thumbnail of Genotoxic evaluation of an industrial effluent from an oil refinery using plant and animal bioassays

Genetics and Molecular Biology, 2010

Polycyclic aromatic hydrocarbons (PAHs) are genotoxic chemicals commonly found in effluents from ... more Polycyclic aromatic hydrocarbons (PAHs) are genotoxic chemicals commonly found in effluents from oil refineries. Bioassays using plants and cells cultures can be employed for assessing environmental safety and potential genotoxicity. In this study, the genotoxic potential of an oil refinery effluent was analyzed by means of micronucleus (MN) testing of Alium cepa, which revealed no effect after 24 h of treatment. On the other hand, primary lesions in the DNA of rat (Rattus norvegicus) hepatoma cells (HTC) were observed through comet assaying after only 2 h of exposure. On considering the capacity to detect DNA damage of a different nature and of these cells to metabolize xenobiotics, we suggest the association of the two bioassays with these cell types, plant (Allium cepa) and mammal (HTC) cells, for more accurately assessing genotoxicity in environmental samples.

Research paper thumbnail of EPR, FT-IR and XRD investigation of soils from Paraná, Brazil

Applied Clay Science, 2011

Samples of Araucária area soil from Paraná state, Brazil, were separated by particle size fractio... more Samples of Araucária area soil from Paraná state, Brazil, were separated by particle size fractionation and investigated by electron paramagnetic resonance (EPR) in X-Band of 9.5GHz at room temperature and 77K, infra-red spectroscopy and X-ray diffractometry. The paramagnetic species in the soil samples were identified by comparison with EPR spectra of some minerals studied recently by our group, several soil

Research paper thumbnail of Tratamento de Solo Contaminado com Petróleo Utilizando Tensoativos e Peróxido de Hidrogênio

Semina: Ciências Exatas e Tecnológicas, 2010

Research paper thumbnail of Potential of babassu biofuels use as aviation fuel

Research, Society and Development, 2022

Through a review of the bibliographic base was identified the potential and difficulties of using... more Through a review of the bibliographic base was identified the potential and difficulties of using biofuels based on babassu culture for use as aviation biofuel. Babassu palm is one of the most important crops for family farming in the north and northeast of Brazil due to its vast use potential. From babassu oil, by transesterification, good quality biodiesel can be obtained. However, it does not have the properties necessary to be used as aviation biofuel. Researches with biofuels from this culture and cultures with a similar organic profile were analyzed pointing out the feasibility of these biofuels as a mixture in aviation kerosene, nevertheless, these biofuels present several problems when used alone. Among the physical-chemical properties analyzed, the freezing point was a critical factor for not using these biofuels. This review points out the best results to improve the physicochemical properties of babassu biofuels to use as aviation fuel and present an important social fact...

Research paper thumbnail of Lipase Production by Botryosphaeria ribis EC-01 on Soybean and Castorbean Meals: Optimization, Immobilization, and Application for Biodiesel Production

Applied Biochemistry and Biotechnology, 2013

The effects of soybean and castorbean meals were evaluated separately, and in combinations at dif... more The effects of soybean and castorbean meals were evaluated separately, and in combinations at different ratios, as substrates for lipase production by Botryosphaeria ribis EC-01 in submerged fermentation using only distilled water. The addition of glycerol analytical grade (AG) and glycerol crude (CG) to soybean and castorbean meals separately and in combination, were also examined for lipase production. Glycerol-AG increased enzyme production, whereas glycerol-CG decreased it. A 2(4) factorial design was developed to determine the best concentrations of soybean meal, castorbean meal, glycerol-AG, and KH2PO4 to optimize lipase production by B. ribis EC-01. Soybean meal and glycerol-AG had a significant effect on lipase production, whereas castorbean meal did not. A second treatment (2(2) factorial design central composite) was developed, and optimal lipase production (4,820 U/g of dry solids content (ds)) was obtained when B. ribis EC-01 was grown on 0.5 % (w/v) soybean meal and 5.2 % (v/v) glycerol in distilled water, which was in agreement with the predicted value (4,892 U/g ds) calculated by the model. The unitary cost of lipase production determined under the optimized conditions developed ranged from US$0.42 to 0.44 based on nutrient costs. The fungal lipase was immobilized onto Celite and showed high thermal stability and was used for transesterification of soybean oil in methanol (1:3) resulting in 36 % of fatty acyl alkyl ester content. The apparent K m and V max were determined and were 1.86 mM and 14.29 μmol min(-1) mg(-1), respectively.