Estudo de caracterização e avaliação da influência do tempo na redução carbotérmica do pó de aciaria elétrica

O pó de aciaria elétrica (PAE) é um resíduo sólido gerado na coleta do material particulado no processo de fabricação do aço em forno elétrico a arco. A classificação segundo norma NBR 10004 para o mesmo é classe I – Perigoso, porque apresenta metais pesados (chumbo e cádmio) em sua constituição, que lixiviam em água excedendo os limites máximos estabelecidos por esta norma. Os elementos ferro e zinco são os constituintes majoritários presentes no PAE. O conhecimento da forma como estes elementos estão combinados é de suma importância antes do estudo de novas tecnologias para processamento do resíduo. Este trabalho teve como objetivos principais caracterizar química, física, estrutural e morfologicamente o PAE e avaliar a influência do tempo na redução carbotérmica deste resíduo. Na etapa de caracterização do PAE as seguintes técnicas foram utilizadas: análise granulométrica, análise química, microscopia eletrônica de varredura (MEV), análise por dispersão de energia (EDS), análise digitalizada de mapeamento de raios-x, difração de raios-x (DRX) e espectroscopia Mössbauer. Os experimentos de redução foram realizados em forno mufla na temperatura de 1050°C, em três tempos de redução: 15, 30 e 60 minutos. O agente redutor utilizado foi um carvão gaúcho, proveniente da mina de Faxinal, beneficiado e contendo 17% de cinza. A quantidade de carbono utilizada nos experimentos foi de 50% em excesso em relação a quantidade estequiométrica. O grau de metalização do ferro das amostras reduzidas foi avaliado via técnicas de análise química via-úmida e espectroscopia Mössbauer. O grau de remoção do zinco nas amostras reduzidas foi avaliado via técnica de análise química por Espectrometria de Emissão Atômica por Plasma – ICP. Através da etapa de caracterização verificou-se que o ferro e o zinco são os elementos majoritários presentes no PAE, e estão combinados na forma dos seguintes óxidos: Fe3O4, ZnFe2O4, FeCr2O4, Ca0,15Fe2,85O4 e ZnO. Nos ensaios de redução verificou-se que inicialmente ocorre a redução dos óxidos de ferro. O máximo grau de metalização obtido no tempo de 60 minutos foi em torno de 50%. A análise estatística mostrou que objetivando maximizar a variável de resposta (grau de metalização) e garantir economia o tempo de 15 minutos se mostrou o mais adequado. Para as fases com zinco, verificou-se que após a decomposição da ZnFe2O4 e tempos maiores de redução teve início a redução da ZnO. Com 60 minutos na temperatura de 1050°C o grau de remoção do zinco foi de 95%.

Estudo do tratamento de inclusões com cálcio na fabricação do aço SAE 8620

O tratamento de modificação de óxidos (e sulfetos) com cálcio tornou-se usual na produção de aços de elevada limpeza interna. O conhecimento da composição química de inclusões, dependendo da composição do aço líquido, é requisito fundamental para garantir a lingotabilidade desses aços e propriedades mecânicas adequadas dependendo da aplicação dos mesmos. O objetivo deste trabalho foi o estudo da composição química de inclusões ao longo do processo de refino secundário, com enfoque no tratamento com cálcio. Para tanto, foram comparados dados experimentais (planta industrial) com simulações via termodinâmica computacional (software FactSage). A metodologia utilizada consistiu em: a) obtenção de dados experimentais para determinar os dados de entrada das simulações; b) utilizar os bancos de dados e a rotina de minimização da Energia de Gibbs do software FactSage, para calcular o equilíbrio entre as fases aço líquido (modelo associado) e inclusões (escória - modelo quase-químico modificado) e; c) comparar os resultados obtidos na planta industrial com os simulados via FactSage. O acompanhamento do processo de elaboração do aço na Gerdau Aços Especiais Piratini (AEP) foi fundamental para identificar eventuais desvios de processo, bem como para interpretar eventuais discrepâncias entre os resultados Na simulação de todas as provas, verificou-se que é fundamental um baixo desvio-padrão na análise dos elementos, se o objetivo é simular um padrão de elaboração de aço. Como resultado deste trabalho, verificou-se ainda que entre 10 e 14 ppm é a faixa ideal de cálcio para a formação de inclusões líquidas com teor mínimo de CaS, para os níveis de oxigênio, enxofre e alumínio do SAE 8620 na etapa final do processo de elaboração desse aço na AEP. É importante destacar que faixas mais amplas de cálcio podem ser utilizadas, dependendo do tipo de processo na aciaria e do tipo de produto requerido.

Contributo da informação gemelar para a investigação da síndrome metabólica: um estudo da famílias na Região Autónoma da Madeira

Os objectivos gerais deste trabalho foram: (1) estimar a magnitude dos respectivos efeitos genéticos e ambientais nos indicadores da síndrome metabólica; (2) estimar a prevalência da síndrome metabólica nos gémeos monozigóticos e dizigóticos; e (3) estimar o risco de agregação nos indicadores da síndrome metabólica. A amostra envolveu 414 sujeitos madeirenses, nomeadamente 207 pares de gémeos (84 pares de gémeos monozigóticos e 123 pares de gémeos dizigóticos), dos 3 aos 18 anos, que participaram no projecto de investigação: "Influências Genéticas e Envolvimento na Actividade Física, Aptidão e Saúde – O Estudo de Famílias da Madeira" (GEAFAS). A síndrome metabólica teve por base as recomendações do Adult Treatment Panel III (2001), com os pontos de corte propostos por Ferranti et al. (2004). As estimativas de heritabilidade revelaram efeitos genéticos em todos os indicadores da SM: perímetro da cintura (a2 = 0.80), seguida dos triglicerídeos (a2 = 0.61), pressão arterial sistólica (a2 = 0.59), glicose (a2 = 0.55) e colesterol HDL (a2 = 0.34). As estimativas dos efeitos do ambiente único da glicose, pressão arterial sistólica, triglicerídeos, colesterol HDL e perímetro da cintura foram 0.45, 0.41, 0.39, 0.22 e 0.20, respectivamente. O ambiente comum reportou uma estimativa de 0.44 para o colesterol HDL. Foi encontrada uma prevalência da síndrome metabólica de 4.1%, 2.4% para os gémeos monozigóticos e de 5.3% para os gémeos dizigóticos. O colesterol HDL foi o factor de risco mais prevalecente (22.9%). Os gémeos monozigóticos apresentam um maior risco de agregação da síndrome metabólica. Da amostra total, 48.1% das crianças e adolescentes apresentou no mínimo um factor de risco. As crianças e adolescentes madeirenses demonstraram uma etiologia multifactorial nos componentes da síndrome metabólica incluindo os factores genéticos e ambientais. A prevalência da SM foi baixa. Os dados sugerem agregação familiar no risco dos diferentes indicadores da síndrome metabólica.

Índices de obesidade central e fatores de risco cardiovascular na síndrome dos ovários policísticos

Fundamento: A obesidade abdominal apresenta elevada prevalência em mulheres com síndrome dos ovários policísticos (SOP) e está associada a um aumento do risco cardiovascular. Objetivo: Verificar a acurácia da circunferência da cintura (CC), da relação cintura-quadril (RCQ), da relação cinturaestatura (RCEST) e do índice de conicidade (índice C), no que se refere à detecção de fatores de risco cardiovascular (FRCV) em mulheres com SOP. Métodos: Por meio de estudo transversal, foram alocadas 102 mulheres (26,5 ± 5 anos) com diagnóstico de SOP, de acordo com o consenso de Rotterdam. O colesterol total (CT), os triglicerídeos (TG), o LDL-colesterol (LDL-C), o HDLcolesterol (HDL-C), a glicemia de jejum, a glicemia após teste oral de tolerância à glicose (TOTG) e a pressão arterial (PA) foram avaliados em todas as pacientes, além das variáveis antropométricas. Resultados: A relação cintura-estatura foi o marcador que apresentou correlações positivas significativas com o maior número de FRCV (PA, TG e glicemia após TOTG), destacando-se ainda a correlação negativa com HDL-C. Todos os marcadores antropométricos avaliados se correlacionaram positivamente com PA, enquanto CC e RCQ apresentaram correlação positiva também com TG. No tocante à acurácia para detecção de FRCV, os indicadores antropométricos considerados apresentaram taxas de sensibilidade superiores a 60%, com destaque para a RCEST, que apresentou sensibilidade superior a 70%. Conclusão: A RCEST demonstrou ser o indicador antropométrico com a melhor acurácia para a predição de FRCV. Nesse sentido, propõe-se a inclusão desse parâmetro de fácil mensuração na avaliação clínica para o rastreamento de mulheres com SOP e FRCV----------------------ABSTRACT Background: Women with polycystic ovary syndrome (PCOS) present a high prevalence of abdominal obesity, which is associated with an increased cardiovascular risk. Objective: To verify the accuracy of the waist circumference (WC), waist-to-hip ratio (WHR), waist-to-height ratio (WHtR) and the conicity index (CI) in the detection of cardiovascular risk factors (CVRF) in women with PCOS. Methods: The present transversal study allocated 102 women (26.5 ± 5 years) with a diagnosis of PCOS, according to the Rotterdam criteria. Total cholesterol (TC), triglycerides (TG), LDL-cholesterol (LDL-C), HDL-cholesterol (HDL-C), fasting glucose, glucose after the oral glucose tolerance test (OGTT) and blood pressure (BP) were evaluated in all patients, in addition to the anthropometric variables. Results: The WHtR was the marker that presented significant positive correlations with the highest number of CVRF (BP, TG and post-OGTT glucose), whereas there was a negative correlation with HDL-C. All the evaluated anthropometric markers were positively correlated with BP, whereas WC and WHR also presented a positive correlation with TG. Regarding the accuracy for the detection of CVRF, the anthropometric markers presented a sensibility > 60%, especially the WHtR, which had a sensibility > 70%. Conclusion: The WHtR showed to be the most accurate anthropometric indicator for the prediction of CVRF. In this sense, we propose the inclusion of this easily-measured parameter in the clinical assessment for the screening of women with PCOS and CVRF

Synthesis and characterization of lanthanum- and yttrium-doped Fe2O3 pigments

MELO, D. M. A. et al. Synthesis and charactezarion of lanthanum and yttrium doped Fe2O3 pigments. Cerâmica, São Paulo, v. 53, p. 79-82, 2007.

A infecção por Leishmania infantum chagasi altera o metabolismo lipídico do hospedeiro

American visceral leishmaniasis (AVL), caused by Leishmania infantum chagasi (L.i.chagasi), stands as a public health problem in Brazil, with human and canine cases related in all states..Lipid metabolism can be modified in several status of infection. For example, experimental studies show that the cholesterol is necessary to internalization and replication of L.i.chagasi in macrophages through caveolar domains. Patients with AVL present low levels of cholesterol and a visible triglycerides increase. This work aimed to evaluate the lipid metabolism in several post-infection status by L.i.chagasi, including individuals with symptomatic infection (AVL), and asymptomatic. The levels of cholesterol, triglycerides, HDL and reactive C protein, were measured. Individuals with AVL were compared with individuals with assymptomatic infection and presented low levels of total cholesterol (128 ± 6.180 mg/dL vs. 158 ±5.733 mg/dL, p=0.0001), HDL (29 ± 1.746 mg/dL vs. 37 ± 1.647 mg/dL, p=0.0001), increased levels of triglycerides (149.5 mg/dL ± 12.72 vs. 78.00 ± 10.43 mg/dL, p=0.0095) and higher levels of reactive C protein (1.750± 0.4939 mg/dL vs. 0.40 ± 0.1707 mg/dL; p=0.0001). The expression of genes related to lipid metabolism, such as LXR-a, LXR-b, PPAR-a, PPAR-d, PPAR-g and APOE was evaluated by real time PCR. A reduction in the expression of those genes was found in the group of AVL patients corroborating the serum levels of the metabolites earlier quantified. Our findings suggest a modulation of metabolism of lipids, in the chronic phase of AVL, this could facilitate the survival of leishmania, due to the known reduction on the ability of macrophages in presenting antigens efficiently to the T cells due to the reduction in the cholesterol available, it results in a subversion of the host immunity.

Efeito sacietogênico de um novo inibidor de tripsina da paçoca do amendoim com aumento plasmático de colecistocinina (cck)

Obesity is increasing, reaching epidemic levels in many regions of the world. Studies have shown that consumption of peanuts influences on weight control and this influence may be due to the action of trypsin inhibitors sacietogênica that condition increased plasma colescistocinina (CCK). Moreover, the peanut has other health benefits, and these assignments are guaranteed to increase their production and consumption of several of its products, including the paçoca peanut. The aim of this study was to identify the presence of a trypsin inhibitor in paçoca peanut and evaluate its effect on food intake, weight gain and histomorphological changes in swiss mice (n = 8) and Wistar rats (n = 6). Experimental diets were prepared based on the AIN-93G and supplemented with tack or peanut trypsin inhibitor partially purified paçoca peanut (AHTI). After each treatment, the animals were anesthetized and euthanized, their bloods were collected by cardiac puncture for the determination of CCK and other biochemical parameters (glucose, triglycerides, total cholesterol, high density lipoprotein, low density lipoprotein, glutamic-pyruvic transaminase, glutamic oxaloacetic transaminase and albumin) and their pancreas removed for histologic and morphometric analysis. The supplementation with paçoca peanut and the AHTI showed a decrease of body weight gain and food intake in both mice and rats, due to the satiety, since the animals showed no evidence of impairment of nutritional status conditioned by consumption the AHTI. There were also observed biochemical or morphological important when compared with controls. However, AHTI led to increased secretion of CCK, a peptide sacietogênico. Thus, these results indicate that AHTI present in paçoca peanut, is able to enhance the secretion of plasma CCK and thereby reduce the weight gain associated with lower food intake of experimenta animals

Ação de polissacarídeos sulfatados de Fucus Vesiculosus na Hemostasia e no sistema complemento

Fucans are a family of sulfated homo and teropolysaccharides respectively, composed mainly of a- (1®2) and a- (1®3) linked by L-fucose residues. Properties such as the ability to act as an anti-contraceptive, to reduce cholesterol levels, and to act as an anti-tumor agent are much related. We have focused our attention on the anticoagulant properties, platelet aggregation, hemorrhagic activity and complement system in vitro of commercial fucoidan (F) and their purified fractions (F1, F2 and F3) from Fucus vesiculosus obtained from fractionation of the fucoidan with different concentrations of acetone 1, 2 and 3v. These compounds were chemically characterized and the fucoidan (F) was modified by desulfation. The anticoagulant activity of the compounds was assessment by activated partial thromboplastin time (APTT) and prothrombine time assay (PT) using citrated normal human plasma. The results of APPT test showed that F, F1 and F2 have high anticoagulants activities 240.0 s (5 µg). The F3 showed 73.7 s in the same concentrations. The results obtained with PT test to F, F1, F2 and F3 were 81.5 s, 120.0 s, 57.1 and 32.5 s respectively with 50 µg. The dessulfated polymer showed a decrease in the anticoagulant activity in these two tests. Platelet aggregation assay was measured turbidimetrically with platelet aggregometer by method of Born. The aggregation platelet with F and fractions F1, F2 and F3 exhibited a two-phase answer in the concentration of 5 mg/mL with maximum aggregation of 76.36 ± 10.3% ; 69.54 ± 9.40%; 75.94 ± 9.01%; 51.13 ± 9.59% respectively. However, was observed a hipoaggregate profile F (15.17 ± 5.2%), F1 (7.40 ± 3.04 %), F2 (19.1 ± 5.41%) and F3 (5.09 ± 3.02%) at 0.1 mg/mL. The hemorrhagic activity assay was carried in Wistar rats and showed that these compounds have low hemorrhagic effect when compared to heparin. The complement system ( alternative pathway was made using non-sensibilized rabbit red blood cells The results of complement system essay showed that F , F2 and F3 have action inhibitory in relation to the group control 0.544, 0.697, 0.622 and 0.958 respectively The results showed that these compounds have action on this system. Interaction of the polisaccharides with proteins C3 and C4 showed that the fraction F1 stimulated the activity assay hemolytic using red blood cells

Ação Sacietogênica de um inibidor de tripsina da semente de tamarindo (Tamarindus indica L.)

The seeds are excellent sources of proteinase inhibitors and have been highlighted owing to various applications. Among these applications are those in effect on food intake and weight gain that stand out because of the increasing number of obese individuals. This study evaluated the effects of trypsin inhibitor present in the seed of tamarind (Tamarindus indica L.) reduction in weight gain, biochemical and morphological alterations in Wistar rats. For this, we partially purified a trypsin inhibitor tamarind seed. This inhibitor, ITT2 at a concentration of 25 mg / kg body weight, over a period of 14 days was able to reduce food intake in rats (n = 6) by approximately 47%, causing a reduction in weight gain approximately 70% when compared with the control group. With the evaluation of the in vivo digestibility was demonstrated that the animals lost weight due to satiety, presented by the reduction of food intake, since there were significant differences between true digestibility for the control group (90.7%) and the group treated with inhibitor (89.88%). Additionally, we checked the deeds of ITT2 on biochemical parameters (glucose, triglycerides, total cholesterol, high-density lipoprotein, low-density lipoprotein, glutamic-pyruvic transaminase, glutamic oxaloacetic transaminase, gamma glutamyl transferase albumin, globulin, total protein and C-reactive protein) and these, when assessed in the study groups showed no statistically significant variations. We also evaluate the histology of some organs, liver, stomach, intestine, and pancreas, and showed no changes. And to evaluate the effect of trypsin inhibitor on food intake due to the satiety is regulated by cholecystokinin (CCK) were measured plasma levels, and it was observed that the levels of CCK in animals receiving ITT2 were significantly higher ( 20 + 1.22) than in animals receiving only solution with casein (10.14 + 2.9) or water (5.92 + 1.15). Thus, the results indicate that the effect caused ITT2 satiety, reducing food intake, which in turn caused a reduction in weight gain in animals without causing morphological and biochemical changes, this effect caused by the elevation of plasma levels CCK

Efeito da suplementação com retinol palmitato em codornas (Coturnix coturnx japonica) nos níveis de retinol na gema dos ovos

Vitamin A deficiency is a serious public health problem in developing countries, and it causes death and blindness among children in the developing countries. The fortification of food could be an important source of vitamins to control deficiency. 60 Coturnix coturnix japonica quails were used in a randomized design with duration of seven weeks. The birds were assigned into five treatments with four repetitions. The objective was to evaluate the influence of the supplementation with different levels of retinyl palmitate (2,000 IU, 4,000 IU, 8,000IU and 16,000 IU) in quails under the levels of retinyl in egg yolks. The method used to dose retinyl in yolks of quail eggs was High Performance Liquid Chromatography and the enzymatic method to quantify the cholesterol concentration. The weight and production of eggs was significantly modified by the supplementation with retinyl in the birds. The results showed a gradual increase in the incorporation of retinyl in the egg yolk as a response to the supplementation, reaching values 384% higher than the control values. By the end of the supplementations a significant reduction in the concentrations of retinyl in the eggs yolk was observed. The most lasting supplementations were with 8,000 IU and 16,000 IU which lasted for three weeks. The cholesterol content in eggs was not significantly modified. The consumption of one egg enriched with 16000UI of retinol palmitate in the present study, by day, would probably reach 10 and 7,3% of the daily recommendations of this micronutrient for children of 1 to 3 years of age, and for 4 to 8 years, respectively. The nutritional value of eggs, related to the vitamin A, can be improved by supplementation of quails

Síntese e caracterização de NiO-CGO para anodo e eletrólitos sólidos e base de Céria para SOFC

The direct use of natural gas makes the Solid Oxide Fuel Cell (SOFC) potentially more competitive with the current energy conversions technologies. The Intermediate Temperature SOFC (IT-SOFC) offer several advantages over the High Temperature SOFC (HT-SOFC), which includes better thermal compatibility among components, fast start with lower energy consumption, manufacture and operation cost reduction. The CeO2 based materials are alternatives to the Yttria Stabilized Zirconia (YSZ) to application in SOFC, as they have higher ionic conductivity and less ohmic losses comparing to YSZ, and they can operate at lower temperatures (500-800°C). Ceria has been doped with a variety of cations, although, the Gd3+ has the ionic radius closest to the ideal one to form solid solution. These electrolytes based in ceria require special electrodes with a higher performance and chemical and termomechanical compatibility. In this work compounds of gadolinia-doped ceria, Ce1-xGdxO2-δ (x = 0,1; 0,2 and 0,3), used as electrolytes, were synthesized by polymeric precursors method, Pechini, as well as the composite material NiO - Ce0,9Gd0,1O1,95, used as anode, also attained by oxide mixture method, mixturing the powders of the both phases calcinated already. The materials were characterized by X ray diffraction, dilatometry and scanning electronic microscopy. The refinement of the diffraction data indicated that all the Ce1-xGdxO2-δ powders were crystallized in a unique cubic phase with fluorite structure, and the composite synthesized by Pechini method produced smaller crystallite size in comparison with the same material attained by oxide mixture method. All the produced powders had nanometric characteristics. The composite produced by Pechini method has microstructural characteristics that can increase the triple phase boundaries (TPB) in the anode, improving the cell efficiency, as well as reducing the mass transport mechanism effect that provokes anode degradation

Influência do uso de combustíveis alternativos na síntese por combustão via microondas para a produção de materiais cerâmicos com estrutura espinélio

The development and study of detectors sensitive to flammable combustible and toxic gases at low cost is a crucial technology challenge to enable marketable versions to the market in general. Solid state sensors are attractive for commercial purposes by the strength and lifetime, because it isn t consumed in the reaction with the gas. In parallel, the use of synthesis techniques more viable for the applicability on an industrial scale are more attractive to produce commercial products. In this context ceramics with spinel structure were obtained by microwave-assisted combustion for application to flammable fuel gas detectors. Additionally, alternatives organic-reducers were employed to study the influence of those in the synthesis process and the differences in performance and properties of the powders obtained. The organic- reducers were characterized by Thermogravimetry (TG) and Derivative Thermogravimetry (DTG). After synthesis, the samples were heat treated and characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), analysis by specific area by BET Method and Scanning Electron Microscopy (SEM). Quantification of phases and structural parameters were carried through Rietveld method. The methodology was effective to obtain Ni-Mn mixed oxides. The fuels influenced in obtaining spinel phase and morphology of the samples, however samples calcined at 950 °C there is just the spinel phase in the material regardless of the organic-reducer. Therefore, differences in performance are expected in technological applications when sample equal in phase but with different morphologies are tested

Síntese e caracterização de catalisadores nanométricos de LaSrNiO4 para aplicação em dessulfurização de tiofeno

The mixed metal oxides constitute an important class of catalytic materials widely investigated in different fields of applications. Studies of rare earth nickelates have been carried by several researchers in order to investigate the structural stability afforded by oxide formed and the existence of catalytic properties at room temperature. So, this study aims synthesize the nanosized catalyst of nickelate of lanthanum doped with strontium (La(1-x)SrxNiO4-d; x = 0,2 and 0,3), through the Pechini method and your characterization for subsequent application in the desulfurization of thiophene reaction. The precursor solutions were calcined at 300ºC/2h for pyrolysis of polyester and later calcinations occurred at temperatures of 500 - 1000°C. The resulting powders were characterized by thermogravimetric analysis (TG / DTG), surface area for adsorption of N2 by BET method, X-ray diffraction (XRD), scanning electron microscopy (HR_SEM) and spectrometry dispersive energy (EDS). The results of XRD had show that the perovskites obtained consist of two phases (LSN and NiO) and from 700ºC have crystalline structure. The results of SEM evidenced the obtainment of nanometric powders. The results of BET show that the powders have surface area within the range used in catalysis (5-50m2/g). The characterization of active sites was performed by reaction of desulfurization of thiophene at room temperature and 200ºC, the relation F/W equal to 0,7 mol h-1mcat -1. The products of the reaction were separated by gas chromatography and identified by the selective detection PFPD sulfur. All samples had presented conversion above 95%

Síntese de pigmentos cerâmicos inorgânicos nanométricos e encapsulados com estrutura core-shell pela rota dos precursores poliméricos

The present work has as objective the development of ceramic pigments based in iron oxides and cobalt through the polymeric precursor method, as well as study their characteristics and properties using methods of physical, chemical, morphological and optical characterizations.In this work was used iron nitrate, and cobalt citrate as precursor and nanometer silica as a matrix. The synthesis was based on dissolving the citric acid as complexing agent, addition of metal oxides, such as chromophores ions and polymerization with ethylene glycol. The powder obtained has undergone pre-ignition, breakdown and thermal treatments at different calcination temperatures (700 °C, 800 °C, 900 °C, 1000 °C and 1100 °C). Thermogravimetric analyzes were performed (BT) and Differential Thermal Analysis (DTA), in order to evaluate the term decomposition of samples, beyond characterization by techniques such as BET, which classified as microporous materials samples calcined at 700 ° C, 800 º C and 900 º C and non-porous when annealed at 1000 ° C and 1100 º C, X-ray diffraction (XRD), which identified the formation of two crystalline phases, the Cobalt Ferrite (CoFe2O4) and Cristobalite (SiO2), Scanning Electron Microscopy (SEM) revealed the formation of agglomerates of particles slightly rounded;and Analysis of Colorimetry, temperature of 700 °C, 800 °C and 900 °C showed a brown color and 1000 °C and 1100 °C violet

Síntese de catalisadores do tipo LaNixFe1-xO3 como precursores catalíticos para reação oxidação parcial do metano

Nickel-bases catalysts have been used in several reform reactions, such as in the partial oxidation of methane to obtain H2 or syngas (H2 + CO). High levels of conversion are usually obtained using this family of catalysts, however, their deactivation resulting from carbon deposition still remains a challenge. Different approaches have been tested aiming at minimizing this difficulty, including the production of perovskites and related structures using modern synthesis methods capable of producing low cost materials with controlled microstructural characteristics at industrial scale. To establish grounds for comparison, in the present study LaNixFe1-xO3 (x=0, 0.3 or 0.7) perovskites were prepared following the Pechini method and by microwave assisted self-combustion. All samples were sub sequently calcined at 900 °C to obtain the target phase. The resulting ceramic powders were characterized by thermogravimetric analysis, infrared spectroscopy, X ray diffraction, specific area and temperature programmed reduction tests. Calcined samples were also used in the partial oxidation reaction of methane to evaluate the level of conversion, selectivity and carbon deposition. The results showed that the calcined samples were crystalline and the target phase was formed regardless of the synthesis method. According to results obtained by Rietveld refinement, we observed the formation of 70.0% of LaNi0.3Fe0.7O3 and 30.0% of La2O3 for samples LN3F7-900- P, LN3F7-900-M and 41,6% of LaNi0.7Fe0.3O3, 30.7% of La2NiO4 and 27.7% of La2O3 for samples LN7F3-900-P and LN7F3-900-M.Temperature-programmed profiles of the LaNiO3 sample revealed the presence of a peak around 510 °C, whereas the LaFeO3 sample depicted a peak above 1000°C. The highest l evel of methane conversion was obtained for LaNiO3 synthesized by the Pechini method. Overall, catalysts prepared by the Pechini method depicted better conversion levels compared to those produced by microwave assisted self-combustion