Leopoldo Alcazar | UFPB - Universidade Federal da Paraíba (original) (raw)

Papers by Leopoldo Alcazar

Materials research express, Nov 1, 2021

This paper studies the influence of metal precursors in the CVD´s catalyst synthesis of carbon na... more This paper studies the influence of metal precursors in the CVD´s catalyst synthesis of carbon nanotubes (CNTs) used as fillers in a polypropylene (PP) matrix (∼0.3 wt%). Two catalytic schemes, Fe/Al2O3 (50:50) and Ni–Fe/Al2O3 (40:10:50), were prepared to determine the influence of the reduction temperature over the characteristics and mechanical properties of CNT as PP fillers. The conversion temperature was varied to see the dependance of the CNT structure to this variable (700 °C–750 °C–800 °C). CNTs products were characterized by SEM and Raman spectroscopy. The SEM micrographs showed a sharper fiber type CNTs for the bimetallic catalyst and the Raman confirmed that better crystallites are obtain over the Fe catalyst. The Fe–PP composite presented enhanced mechanical properties when compare with Fe–Ni–PP, with tensile strength, hardness, and impact properties are higher in 16%, 9%, and 9% respectively. Other carbonaceous materials, as CNF, with less crystallinity presented poorer mechanical properties. Finally, can be stated that for the use of CNF as fillers in PP composites a Fe/Al2O3 catalyst, and a reaction temperature 700 °C–750 °C will produce a CNF with 60 nm mean diameter, is better than the use of Fe-Ni based catalysts.

Universidade Federal do Rio Grande do Norte, Mar 2, 2012

Amorphous silica-alumina and modified by incipient impregnation of iron, nickel, zinc and chromiu... more Amorphous silica-alumina and modified by incipient impregnation of iron, nickel, zinc and chromium were synthetized in oxide and metal state and evaluated as catalysts for the chloromethane conversion reaction. With known techniques their textural properties were determined and dynamics techniques in programmed temperature were used to find the acid properties of the materials. A thermodynamic model was used to determine the adsorption and desorption capacity of chloromethane. Two types of reactions were studied. Firstly the chloromethane was catalytically converted to hydrocarbons (T = 300-450 o C e m = 300 mg) in a fixed bed reactor with controlled pressure and flow. Secondly the deactivation of the unmodified support was studied (at 300 °C and m=250 g) in a micro-adsorver provided of gravimetric monitoring. The metal content (2,5%) and the chloromethane percent of the reagent mixture (10% chloromethane in nitrogen) were fixed for all the tests. From the results the chloromethane conversion and selectivity of the gaseous products (H 2 , CH 4 , C 3 and C 4) were determined as well as the energy of desorption (75,2 KJ/mol for Ni/Al 2 O 3-SiO 2 to 684 KJ/mol for the Zn/Al 2 O 3-SiO 2 catalyst) considering the desorption rate as a temperature function. The presence of a metal on the support showed to have an important significance in the chloromethane condensation. The oxide class catalyst presented a better performance toward the production of hydrocarbons. Especial mention to the ZnO/Al 2 O 3-SiO 2 that, in a gas phase basis, produced C 3 83 % max. and C 4 63% max., respectively, in the temperature of 450 o C and 20 hours on stream. Hydrogen was produced exclusively in the FeO/Al 2 O 3-SiO 2 catalysts (15 % max., T = 550 o C and 5,6 h on stream) and Ni/SiO 2-Al 2 O 3 (75 % max., T = 400 o C and 21,6 h on stream). All the catalysts produced methane (10 à 92 %), except for Ni/Al 2 O 3-SiO 2 and CrO/Al 2 O 3-SiO 2. In the deactivation study two models were proposed: The parallel model, where the product production competes with coke formation; and the sequential model, where the coke formation competes with the product desorption dessorption step. With the mass balance equations and the mechanism proposed six parameters were determined. Two kinetic parameters: the hydrocarbon formation constant, 8,46 10-4 min-1 , the coke formation, 1,46 10-1 min-1 ; three thermodynamic constants (the global, 0,003, the chloromethane adsorption 0,417 bar-1 , the hydrocarbon adsorption 2,266 bar-1), and the activity exponent of the coke formation (1,516). The model was reasonable well fitted and presented a satisfactory behavior in relation with the proposed mechanism.

Proceedings of the XXXVIII Iberian Latin American Congress on Computational Methods in Engineering, 2017

Coleção desafios das engenharias: Engenharia de computação 2, 2021

Ceramics International, 2016

Proceedings of the 19th LACCEI International Multi-Conference for Engineering, Education, and Technology: “Prospective and trends in technology and skills for sustainable social development” “Leveraging emerging technologies to construct the future”, 2021

Blucher Chemical Engineering Proceedings, 2018

RESUMO-A medição de algumas variáveis cruciais para o controle de um reator, como a concentração,... more RESUMO-A medição de algumas variáveis cruciais para o controle de um reator, como a concentração, geralmente não está disponível. Buscando contornar isso, foram desenvolvidos nesse trabalho sensores virtuais baseados em identificação de processos. Sendo aqui empregadas o modelo semi-empírico do filtro de Kalman extendido (FKE) e a rede neural artificial (RNA), dotada do método do algoritmo de otimização de Levenberg-Marquardt, para o monitoramente do processo de produção do propileno glicol (C3H8O2). Sendo estimada a concentração do reagente óxido de propileno (C3H6O) na corrente de saída de um reator químico continuamente agitado, simulado no software Simulink-Matlab®. Os resultados obtidos indicaram melhor desempenho à RNA em comparação com os reaultados do FKE, sendo empregados critérios de erro na avaliação. Para superar esses problemas, surgiram os sensores virtuais (SV), baseados em algoritmos matemáticos, implementados em softwares, os quais utilizam medições físicas, como vazões, pressões, temperaturas, para estimar variáveis químicas oi bioquímicas, tais como as concentrações de reagentes e produtos (MORAIS JR., 2015). Nesse trabalho, foram desenvolvidos dois SV, o filtro de Kalma extendido (FKE) e uma rede neural artificial (RNA) com o método de treinamento de Levenberg-Marquardt, para o monitoramento da concentração de etileno glicol num processo de produção em reator continuamente agitado (CSTR), operando exotermicamente.

Creative Education, 2017

In this article, we discuss the possibility of starting heat transfer coursework with transient p... more In this article, we discuss the possibility of starting heat transfer coursework with transient problems. We begin with the analysis of a microscopic transient problem, from when the process begins until it reaches a steady state. In addition, we propose that the students perform four or five activities per month in the classroom, in pairs, instead of requiring traditional exams. We developed a questionnaire to check the level of student satisfaction with the methodology used. Of the students, 59% had little difficulty understanding the theory, 59% did not have difficulty calculating microscopic transient balances, and 46% had no difficulty with steady-state calculations. A total of 59% preferred that all the evaluations were conducted as activities in the classroom, and 41% and 51% preferred that the course began with transient and steady-state problems, respectively.

Blucher Chemical Engineering Proceedings, 2017

Ceramics International, 2016

In this work, we investigated the effects of two different synthetic routes, Pechini and microwav... more In this work, we investigated the effects of two different synthetic routes, Pechini and microwave-induced combustion method, on the properties of nickel-based catalysts derived from NiO-Ce 0.75 Zr 0.25 O 2 nanocomposite. Powder samples were characterized by specific surface area (SSA) via BET method, X-ray diffraction (XRD), scanning electron microscopy (SEM) and temperature-programmed reduction (TPR). It was found that the synthesis method has a significant influence on the powder morphology, which may affect the catalytic activity. The nickel-based catalysts were tested for the partial oxidation of methane showing high CH 4 conversion, 80% and 81% after the first hour on stream, for the samples prepared by Pechini and combustion method, respectively. These samples also exhibited catalytic stability, keeping CH 4 conversion levels about 77% and 80% after ten hours on stream, respectively. We suggest that such good performance is related to the good dispersion and particle size of the metallic nickel over Zr-CeO2 support.

Anais do XX Congresso Brasileiro de Engenharia Química, 2015

RESUMO-Este trabalho tem como objetivo o estudo avançado das variáveis que afetam as temperaturas... more RESUMO-Este trabalho tem como objetivo o estudo avançado das variáveis que afetam as temperaturas e as composições de interesse em um processo de destilação azeotrópica de alta pureza. Trata-se de uma coluna de destilação azeotrópica de alta pureza do processo de purificação do composto 1,2 Dicloroetano (1,2-EDC), sendo simulada em regime estacionário com dados reais de uma planta industrial no software Aspen Plus TM. A análise de sensibilidade para seleção de variáveis de entrada, ditas secundárias, que afetam diretamente as temperaturas e as composições dos produtos de interesse é feita com os métodos da Decomposição dos Valores Singulares (SVD) e da Matriz de Ganho Relativo (RGA) no software Matlab®. São selecionadas pares de variáveis manipuladascontroladas para tomada de decisões. Os resultados obtidos nas análises indicam caminhos onde pode ser aplicado controle de temperatura/composição singular ou dual (singular/dual composition control), ou até quais variáveis de entrada podem compor um modelo de inferência de composição de produtos de base, possibilitando a construção de analisadores virtuais e a aplicação de controle inferencial.

Brazilian Journal of Petroleum and Gas, 2011

CuCl 2 catalysts supported on silica were used in the oxychlorination of methane. The materials w... more CuCl 2 catalysts supported on silica were used in the oxychlorination of methane. The materials were synthesized by the ion-exchange technique in a basic solution, using a copper-ammonia complex with 3 and 6 % of nominal copper load. The materials where characterized by Thermogravimetry (TG), X-ray Fluorescence Spectroscopy (XRF), Temperature Programmed Reduction (TPR), Scanning Electron Microscopy with X-ray microanalysis (SEM/EDS), BET specific area, and Pore Distribution. The characterization confirmed the presence of copper on the support surface, concluding that the ionexchange technique was adequate for the catalyst synthesis. During reaction assays, an oxychlorination bench-scale unit was employed. The tests were carried out at 673 and 773 K. The results demonstrated the influence of temperature and catalyst copper content on methane conversion.

Brazilian Journal of Chemical Engineering, 2009

In the present work, a synthetic effluent of phenol was treated by means of a total oxidation pro... more In the present work, a synthetic effluent of phenol was treated by means of a total oxidation process-Catalyzed Wet Oxidation (CWO). A mixed oxide of Mn-Ce (7:3), the catalyst, was synthesized by co-precipitation from an aqueous solution of MnCl 2 and CeCl 3 in a basic medium. The mixed oxide, MnO 2 /CeO 2 , was characterized and used in the oxidation of phenol in a slurry reactor in the temperature range of 80-130ºC and pressure of 2.04-4.76 MPa. A phenol solution containing 2.4-dichlorophenol and 2.4dichlorophenoxyacetic acid was also degraded with good results. A lumped kinetic model, with two parallel reaction steps, fits precisely with the integrated equation and the experimental data. The kinetic parameters obtained are in agreement with the Arrhenius equation. The activation energies were determined to be 38.4 for the total oxidation and 53.4 kJ/mol for the organic acids formed.

Revista de la Sociedad Química del Perú, 2018

Se prepararon y caracterizaron catalizadores de Níquel–Cobre soportados sobre alúmina (Al2O3) med... more Se prepararon y caracterizaron catalizadores de Níquel–Cobre soportados sobre alúmina (Al2O3) mediante el método de impregnación, en el cual se realizaron variaciones en las proporciones Ni:Cu de 7:1, 9:1 y 11:1. Se caracterizó el catalizador por difracción de rayos X, Fluorescencia de Rayos X, microscopia electrónica de barrido, análisis Terrmogravimétrico y la medición de superficie de área BET; además se realizaron ensayos de síntesis de nanofibras de carbono mediante la descomposición catalítica de metano a 600°C. Los resultados sugieren que la carga del Níquel influye en la deposición de carbono, siendo la relación con el mayor contenido de Níquel (Ni:Cu 11:1) la que mostró mayor rendimiento (19,4 gC/gcat). Además las propiedades estructurales del carbono depositado dependían de la composición del catalizador, pasando de un carbono fino y largo sobre el catalizador Ni:Cu 11:1 a un carbono ancho y algo más corto sobre las muestra de Ni:Cu 7:1 y 9:1.

Brazilian Journal of Development, 2019

Effect of temperature and flow rate on parallel flow co2 absorption by distilled water in co-curr... more Effect of temperature and flow rate on parallel flow co2 absorption by distilled water in co-current microchannel device Efeito da temperatura e taxa de fluxo na absorção paralela de co2 por água destilada em dispositivo de microcanal co-atual

Materials Research, 2002

The acid properties of palygorskite clay (R1) were studied using n-butylamine as probe molecule. ... more The acid properties of palygorskite clay (R1) were studied using n-butylamine as probe molecule. A comparison was made of these properties in palygorskite clay (R1), in an acidified palygorskite (R2) and in acid palygorskite loaded with 2% of lanthanum (R3). The total ...

In this work, we investigated the effects of two different synthetic routes, Pechini and microwav... more In this work, we investigated the effects of two different synthetic routes, Pechini and microwave-induced combustion method, on the properties of nickel-based catalysts derived from NiO-Ce 0.75 Zr 0.25 O 2 nanocomposite. Powder samples were characterized by specific surface area (SSA) via BET method, X-ray diffraction (XRD), scanning electron microscopy (SEM) and temperature-programmed reduction (TPR). It was found that the synthesis method has a significant influence on the powder morphology, which may affect the catalytic activity. The nickel-based catalysts were tested for the partial oxidation of methane showing high CH 4 conversion, 80% and 81% after the first hour on stream, for the samples prepared by Pechini and combustion method, respectively. These samples also exhibited catalytic stability, keeping CH 4 conversion levels about 77% and 80% after ten hours on stream, respectively. We suggest that such good performance is related to the good dispersion and particle size of the metallic nickel over Zr-CeO2 support.

Materials research express, Nov 1, 2021

This paper studies the influence of metal precursors in the CVD´s catalyst synthesis of carbon na... more This paper studies the influence of metal precursors in the CVD´s catalyst synthesis of carbon nanotubes (CNTs) used as fillers in a polypropylene (PP) matrix (∼0.3 wt%). Two catalytic schemes, Fe/Al2O3 (50:50) and Ni–Fe/Al2O3 (40:10:50), were prepared to determine the influence of the reduction temperature over the characteristics and mechanical properties of CNT as PP fillers. The conversion temperature was varied to see the dependance of the CNT structure to this variable (700 °C–750 °C–800 °C). CNTs products were characterized by SEM and Raman spectroscopy. The SEM micrographs showed a sharper fiber type CNTs for the bimetallic catalyst and the Raman confirmed that better crystallites are obtain over the Fe catalyst. The Fe–PP composite presented enhanced mechanical properties when compare with Fe–Ni–PP, with tensile strength, hardness, and impact properties are higher in 16%, 9%, and 9% respectively. Other carbonaceous materials, as CNF, with less crystallinity presented poorer mechanical properties. Finally, can be stated that for the use of CNF as fillers in PP composites a Fe/Al2O3 catalyst, and a reaction temperature 700 °C–750 °C will produce a CNF with 60 nm mean diameter, is better than the use of Fe-Ni based catalysts.

Universidade Federal do Rio Grande do Norte, Mar 2, 2012

Amorphous silica-alumina and modified by incipient impregnation of iron, nickel, zinc and chromiu... more Amorphous silica-alumina and modified by incipient impregnation of iron, nickel, zinc and chromium were synthetized in oxide and metal state and evaluated as catalysts for the chloromethane conversion reaction. With known techniques their textural properties were determined and dynamics techniques in programmed temperature were used to find the acid properties of the materials. A thermodynamic model was used to determine the adsorption and desorption capacity of chloromethane. Two types of reactions were studied. Firstly the chloromethane was catalytically converted to hydrocarbons (T = 300-450 o C e m = 300 mg) in a fixed bed reactor with controlled pressure and flow. Secondly the deactivation of the unmodified support was studied (at 300 °C and m=250 g) in a micro-adsorver provided of gravimetric monitoring. The metal content (2,5%) and the chloromethane percent of the reagent mixture (10% chloromethane in nitrogen) were fixed for all the tests. From the results the chloromethane conversion and selectivity of the gaseous products (H 2 , CH 4 , C 3 and C 4) were determined as well as the energy of desorption (75,2 KJ/mol for Ni/Al 2 O 3-SiO 2 to 684 KJ/mol for the Zn/Al 2 O 3-SiO 2 catalyst) considering the desorption rate as a temperature function. The presence of a metal on the support showed to have an important significance in the chloromethane condensation. The oxide class catalyst presented a better performance toward the production of hydrocarbons. Especial mention to the ZnO/Al 2 O 3-SiO 2 that, in a gas phase basis, produced C 3 83 % max. and C 4 63% max., respectively, in the temperature of 450 o C and 20 hours on stream. Hydrogen was produced exclusively in the FeO/Al 2 O 3-SiO 2 catalysts (15 % max., T = 550 o C and 5,6 h on stream) and Ni/SiO 2-Al 2 O 3 (75 % max., T = 400 o C and 21,6 h on stream). All the catalysts produced methane (10 à 92 %), except for Ni/Al 2 O 3-SiO 2 and CrO/Al 2 O 3-SiO 2. In the deactivation study two models were proposed: The parallel model, where the product production competes with coke formation; and the sequential model, where the coke formation competes with the product desorption dessorption step. With the mass balance equations and the mechanism proposed six parameters were determined. Two kinetic parameters: the hydrocarbon formation constant, 8,46 10-4 min-1 , the coke formation, 1,46 10-1 min-1 ; three thermodynamic constants (the global, 0,003, the chloromethane adsorption 0,417 bar-1 , the hydrocarbon adsorption 2,266 bar-1), and the activity exponent of the coke formation (1,516). The model was reasonable well fitted and presented a satisfactory behavior in relation with the proposed mechanism.

Proceedings of the XXXVIII Iberian Latin American Congress on Computational Methods in Engineering, 2017

Coleção desafios das engenharias: Engenharia de computação 2, 2021

Ceramics International, 2016

Proceedings of the 19th LACCEI International Multi-Conference for Engineering, Education, and Technology: “Prospective and trends in technology and skills for sustainable social development” “Leveraging emerging technologies to construct the future”, 2021

Blucher Chemical Engineering Proceedings, 2018

RESUMO-A medição de algumas variáveis cruciais para o controle de um reator, como a concentração,... more RESUMO-A medição de algumas variáveis cruciais para o controle de um reator, como a concentração, geralmente não está disponível. Buscando contornar isso, foram desenvolvidos nesse trabalho sensores virtuais baseados em identificação de processos. Sendo aqui empregadas o modelo semi-empírico do filtro de Kalman extendido (FKE) e a rede neural artificial (RNA), dotada do método do algoritmo de otimização de Levenberg-Marquardt, para o monitoramente do processo de produção do propileno glicol (C3H8O2). Sendo estimada a concentração do reagente óxido de propileno (C3H6O) na corrente de saída de um reator químico continuamente agitado, simulado no software Simulink-Matlab®. Os resultados obtidos indicaram melhor desempenho à RNA em comparação com os reaultados do FKE, sendo empregados critérios de erro na avaliação. Para superar esses problemas, surgiram os sensores virtuais (SV), baseados em algoritmos matemáticos, implementados em softwares, os quais utilizam medições físicas, como vazões, pressões, temperaturas, para estimar variáveis químicas oi bioquímicas, tais como as concentrações de reagentes e produtos (MORAIS JR., 2015). Nesse trabalho, foram desenvolvidos dois SV, o filtro de Kalma extendido (FKE) e uma rede neural artificial (RNA) com o método de treinamento de Levenberg-Marquardt, para o monitoramento da concentração de etileno glicol num processo de produção em reator continuamente agitado (CSTR), operando exotermicamente.

Creative Education, 2017

In this article, we discuss the possibility of starting heat transfer coursework with transient p... more In this article, we discuss the possibility of starting heat transfer coursework with transient problems. We begin with the analysis of a microscopic transient problem, from when the process begins until it reaches a steady state. In addition, we propose that the students perform four or five activities per month in the classroom, in pairs, instead of requiring traditional exams. We developed a questionnaire to check the level of student satisfaction with the methodology used. Of the students, 59% had little difficulty understanding the theory, 59% did not have difficulty calculating microscopic transient balances, and 46% had no difficulty with steady-state calculations. A total of 59% preferred that all the evaluations were conducted as activities in the classroom, and 41% and 51% preferred that the course began with transient and steady-state problems, respectively.

Blucher Chemical Engineering Proceedings, 2017

Ceramics International, 2016

In this work, we investigated the effects of two different synthetic routes, Pechini and microwav... more In this work, we investigated the effects of two different synthetic routes, Pechini and microwave-induced combustion method, on the properties of nickel-based catalysts derived from NiO-Ce 0.75 Zr 0.25 O 2 nanocomposite. Powder samples were characterized by specific surface area (SSA) via BET method, X-ray diffraction (XRD), scanning electron microscopy (SEM) and temperature-programmed reduction (TPR). It was found that the synthesis method has a significant influence on the powder morphology, which may affect the catalytic activity. The nickel-based catalysts were tested for the partial oxidation of methane showing high CH 4 conversion, 80% and 81% after the first hour on stream, for the samples prepared by Pechini and combustion method, respectively. These samples also exhibited catalytic stability, keeping CH 4 conversion levels about 77% and 80% after ten hours on stream, respectively. We suggest that such good performance is related to the good dispersion and particle size of the metallic nickel over Zr-CeO2 support.

Anais do XX Congresso Brasileiro de Engenharia Química, 2015

RESUMO-Este trabalho tem como objetivo o estudo avançado das variáveis que afetam as temperaturas... more RESUMO-Este trabalho tem como objetivo o estudo avançado das variáveis que afetam as temperaturas e as composições de interesse em um processo de destilação azeotrópica de alta pureza. Trata-se de uma coluna de destilação azeotrópica de alta pureza do processo de purificação do composto 1,2 Dicloroetano (1,2-EDC), sendo simulada em regime estacionário com dados reais de uma planta industrial no software Aspen Plus TM. A análise de sensibilidade para seleção de variáveis de entrada, ditas secundárias, que afetam diretamente as temperaturas e as composições dos produtos de interesse é feita com os métodos da Decomposição dos Valores Singulares (SVD) e da Matriz de Ganho Relativo (RGA) no software Matlab®. São selecionadas pares de variáveis manipuladascontroladas para tomada de decisões. Os resultados obtidos nas análises indicam caminhos onde pode ser aplicado controle de temperatura/composição singular ou dual (singular/dual composition control), ou até quais variáveis de entrada podem compor um modelo de inferência de composição de produtos de base, possibilitando a construção de analisadores virtuais e a aplicação de controle inferencial.

Brazilian Journal of Petroleum and Gas, 2011

CuCl 2 catalysts supported on silica were used in the oxychlorination of methane. The materials w... more CuCl 2 catalysts supported on silica were used in the oxychlorination of methane. The materials were synthesized by the ion-exchange technique in a basic solution, using a copper-ammonia complex with 3 and 6 % of nominal copper load. The materials where characterized by Thermogravimetry (TG), X-ray Fluorescence Spectroscopy (XRF), Temperature Programmed Reduction (TPR), Scanning Electron Microscopy with X-ray microanalysis (SEM/EDS), BET specific area, and Pore Distribution. The characterization confirmed the presence of copper on the support surface, concluding that the ionexchange technique was adequate for the catalyst synthesis. During reaction assays, an oxychlorination bench-scale unit was employed. The tests were carried out at 673 and 773 K. The results demonstrated the influence of temperature and catalyst copper content on methane conversion.

Brazilian Journal of Chemical Engineering, 2009

In the present work, a synthetic effluent of phenol was treated by means of a total oxidation pro... more In the present work, a synthetic effluent of phenol was treated by means of a total oxidation process-Catalyzed Wet Oxidation (CWO). A mixed oxide of Mn-Ce (7:3), the catalyst, was synthesized by co-precipitation from an aqueous solution of MnCl 2 and CeCl 3 in a basic medium. The mixed oxide, MnO 2 /CeO 2 , was characterized and used in the oxidation of phenol in a slurry reactor in the temperature range of 80-130ºC and pressure of 2.04-4.76 MPa. A phenol solution containing 2.4-dichlorophenol and 2.4dichlorophenoxyacetic acid was also degraded with good results. A lumped kinetic model, with two parallel reaction steps, fits precisely with the integrated equation and the experimental data. The kinetic parameters obtained are in agreement with the Arrhenius equation. The activation energies were determined to be 38.4 for the total oxidation and 53.4 kJ/mol for the organic acids formed.

Revista de la Sociedad Química del Perú, 2018

Se prepararon y caracterizaron catalizadores de Níquel–Cobre soportados sobre alúmina (Al2O3) med... more Se prepararon y caracterizaron catalizadores de Níquel–Cobre soportados sobre alúmina (Al2O3) mediante el método de impregnación, en el cual se realizaron variaciones en las proporciones Ni:Cu de 7:1, 9:1 y 11:1. Se caracterizó el catalizador por difracción de rayos X, Fluorescencia de Rayos X, microscopia electrónica de barrido, análisis Terrmogravimétrico y la medición de superficie de área BET; además se realizaron ensayos de síntesis de nanofibras de carbono mediante la descomposición catalítica de metano a 600°C. Los resultados sugieren que la carga del Níquel influye en la deposición de carbono, siendo la relación con el mayor contenido de Níquel (Ni:Cu 11:1) la que mostró mayor rendimiento (19,4 gC/gcat). Además las propiedades estructurales del carbono depositado dependían de la composición del catalizador, pasando de un carbono fino y largo sobre el catalizador Ni:Cu 11:1 a un carbono ancho y algo más corto sobre las muestra de Ni:Cu 7:1 y 9:1.

Brazilian Journal of Development, 2019

Effect of temperature and flow rate on parallel flow co2 absorption by distilled water in co-curr... more Effect of temperature and flow rate on parallel flow co2 absorption by distilled water in co-current microchannel device Efeito da temperatura e taxa de fluxo na absorção paralela de co2 por água destilada em dispositivo de microcanal co-atual

Materials Research, 2002

The acid properties of palygorskite clay (R1) were studied using n-butylamine as probe molecule. ... more The acid properties of palygorskite clay (R1) were studied using n-butylamine as probe molecule. A comparison was made of these properties in palygorskite clay (R1), in an acidified palygorskite (R2) and in acid palygorskite loaded with 2% of lanthanum (R3). The total ...

In this work, we investigated the effects of two different synthetic routes, Pechini and microwav... more In this work, we investigated the effects of two different synthetic routes, Pechini and microwave-induced combustion method, on the properties of nickel-based catalysts derived from NiO-Ce 0.75 Zr 0.25 O 2 nanocomposite. Powder samples were characterized by specific surface area (SSA) via BET method, X-ray diffraction (XRD), scanning electron microscopy (SEM) and temperature-programmed reduction (TPR). It was found that the synthesis method has a significant influence on the powder morphology, which may affect the catalytic activity. The nickel-based catalysts were tested for the partial oxidation of methane showing high CH 4 conversion, 80% and 81% after the first hour on stream, for the samples prepared by Pechini and combustion method, respectively. These samples also exhibited catalytic stability, keeping CH 4 conversion levels about 77% and 80% after ten hours on stream, respectively. We suggest that such good performance is related to the good dispersion and particle size of the metallic nickel over Zr-CeO2 support.