Avaliação cinética e potencial do Nb2O5 obtido a partir de um complexo de nióbio para formação do oleato de metila através da reação de esterificação do ácido oleico

Among the heterogeneous catalysts materials made from niobium show up as an alternative to meet the demand of catalysts for biodiesel production. This study aims to evaluate the potential of a heterogeneous catalyst derived from a complex of niobium in the reaction of methyl esterification of oleic acid. The catalyst was synthesized after calcination at different temperatures of a niobium complex ((NH4)3[NbO(C2O4)3].H2O) generating a niobium oxide nanostructure with a different commercial niobium oxide used to synthesize the complex. The commercial niobium oxide, the complex niobium and niobium catalyst were characterized by thermogravimetry (TG and DTA), surface area analysis (BET), scanning electron microscopy (SEM) and X-ray diffraction (XRD), showing the catalyst has researched morphological and crystallographic indicating a catalytic potential higher than that of commercial niobium oxide characteristics. Factorial with central composite design point, with three factors (calcination temperature, molar ratio of alcohol/oleic acid and mass percentage of catalyst) was performed. Noting that the optimal experimental point was given by the complex calcination temperature of 600°C, a molar ratio alcohol/oleic acid of 3.007/1 and the catalyst mass percentage of 7.998%, with a conversion of 22.44% oleic acid in methyl oleate to 60 min of reaction. We performed a composite linear and quadratic regression to determine an optimal statistical point of the reaction, the temperature of calcination of the complex at 450°C, the molar ratio of alcohol/oleic acid 3.3408/1 and mass percentage of catalyst of 7.6833% . Kinetic modeling to estimate parameters for heterogeneous catalysis it set well the experimental results with a final conversion of 85.01% with 42.38% of catalyst and without catalyst at 240 min reaction was performed. Allowing to evaluate the catalyst catalytic studied has the potential to be used in biodiesel production

Síntese e caracterização de CuNb2O6 e CuNbC através de reação sólido- sólido e gás- sólido a baixa temperatura

The refractory metal carbides have proven important in the development of engineering materials due to their properties such as high hardness, high melting point, high thermal conductivity and high chemical stability. The niobium carbide presents these characteristics. The compounds of niobium impregnated with copper also have excellent dielectric and magnetic properties, and furthermore, the Cu doping increases the catalytic activity in the oxidation processes of hydrogen. This study aimed to the synthesis of nanostructured materials CuNbC and niobium and copper oxide from precursor tris(oxalate) oxiniobate ammonium hydrate through gas-solid and solid-solid reaction, respectively. Both reactions were carried out at low temperature (1000°C) and short reaction time (2 hours). The niobium carbide was produced with 5 % and 11% of copper, and the niobium oxide with 5% of copper. The materials were characterized by X-Ray Diffraction (XRD), Rietveld refinement, Scanning Electron Microscopy (SEM), X-Ray Fluorescence Spectroscopy (XRF), infrared spectroscopy (IR), thermogravimetric (TG) and differential thermal analysis (DTA , BET and particle size Laser. From the XRD analysis and Rietveld refinement of CuNbC with S = 1.23, we observed the formation of niobium carbide and metallic copper with cubic structure. For the synthesis of mixed oxide made of niobium and copper, the formation of two distinct phases was observed: CuNb2O6 and Nb2O5, although the latter was present in small amounts

Desenvolvimento de um protótipo para alimentação de pós para aspersão térmica em tocha de plasma

The nanometric powders have special features that usually result in new properties, originating applications or expanding them in various fields of knowledge. Because having a high area/volume ratio, phenomena such as superficial strength of adsorption becomes greater than the weight of the powder which makes more difficult its handling. The high power of agglomeration of these powders requires study and development of equipments to enable its management into the plasma torch. The objective of this work is to develop a powder feeder which can solve the mainly problems about insertion of powder into the thermal spray developed in the laboratory of plasmas, which are carried out with plasma torch arc not transferred (plasma spray). Therefore, it was made a aluminum s powder feeder and tests were performed to verify their operation and determine its rate of deposition by spraying powders of niobium pentoxide (Nb2O5) and titanium dioxide (TiO2) with particle sizes less than 250 mesh (<0.063 mm). We used masses of 0.5 g - 1.0 g and 1.5 g of each powder in tests lasting 15 seconds - 20 to 25 seconds for each mass. The tests were performed in two ways: at atmospheric pressure using argon gas with a flow of 9 l / min as carrier gas and through a Venturi pipe also using argon gas with a flow of 9 l / min as carrier gas and with a flow of 20 l/min as the feed gas passing through the Venturi pipe. The powder feeder developed in this paper is very easy to be handling and building, resulting in feeding rate of 0.25 cm3/min - 1.37 cm3/min. The TiO2 showed higher feeding rates than the Nb2O5 in all tests, and the best rates were obtained with tests using mass 1.5 g and time of 15 seconds, reaching feeding rate of 1.37 cm3/min. The flow of feed had low interference in feeding rate during the tests

Obtenção de pós de Nb a partir da redução aluminotérmica com ignição por plasma

The aluminothermic reduction consists in an exothermic reaction between a metallic oxide and aluminum to produce the metal and the scum. The extracted melted metal of that reaction usually comes mixed with particles of Al2O3 resulting of the reduction, needing of subsequent refine to eliminate the residual impure as well as to eliminate porosities. Seeking to obtain a product in powder form with nanometric size or even submicrometric, the conventional heat source of the reaction aluminothermic , where a resistor is used (ignitor) as ignition source was substituted, for the plasma, that acts more efficient way in each particle of the sample. In that work it was used as metallic oxide the niobium pentoxide (Nb2O5) for the exothermal reaction Nb2O5 + Al. Amounts stoichiometric, substoichiometric and superestoichiometric of aluminum were used. The Nb2O5 powder was mixed with aluminum powder and milled in planetarium of high energy for a period of 6 hours. Those powders were immerged in plasm that acts in a punctual way in each particle, transfering heat, so that the reaction can be initiate and spread integrally for the whole volume of the particle. The mixture of Nb2O5 + Al was characterized through the particle size analysis by laser and X-ray diffraction (DRX) and the obtained product of reaction was characterized using the electronic microscopy of sweeping (MEV) and the formed phases were analyzed by DRX. Niobium powders with inferior sizes to 1 mm were obtained by that method. It is noticed, through the analysis of the obtained results, that is possible to accomplish the aluminothermic reduction process by plasma ignition with final particles with inferior sizes to the original oxide

Síntese de Fischer-Tropsch sobre perovskitas LayCu0,4Fe0,6O3

The current natural gas production of 52 Mm3d-1 and the large projects for its expansion has been setting new boundaries for the Brazilian industry of oil and gas. So far, one of the biggest challenges regards to the logistics for gas transportation from offshore fields. Therefore, the transformation of natural gas into gasoline, diesel and/or olefins via Fischer-Tropsch synthesis would be an alternative to this matter. In this work, the production of hydrocarbons by Fischer-Tropsch synthesis in a slurry reactor was investigated and a perovskite-type catalyst (LayCu0,4Fe0,6O3 ± d) was used with y varying from 0 to 1 on a molar basis. In addition, Nb2O5 support was also applied in order to observe the selectivity of the produced hydrocarbons by the Fischer-Tropsch process. It is shown that the hydrogen conversion was influenced by the support as well as the different phases of the samples. The kinetic results for the CO2 production suffered great influence with the introduction of the Nb2O5 support throughout the series of samples studied. The catalysts allowed obtaining welldefined cuts of hydrocarbons in the range of C1-C6 and C17-C28, and these results were clearly influenced by the support and the lanthanum content. The higher olefin/paraffin ratio obtained was 1.8 when using a non-supported perovskite with y equal to 0.8. This would indicate the suitability of using this material for the production of olefins

Síntese e caracterização de CuNb2O6 e CuNbC através de reação sólido- sólido e gás- sólido a baixa temperatura

The refractory metal carbides have proven important in the development of engineering materials due to their properties such as high hardness, high melting point, high thermal conductivity and high chemical stability. The niobium carbide presents these characteristics. The compounds of niobium impregnated with copper also have excellent dielectric and magnetic properties, and furthermore, the Cu doping increases the catalytic activity in the oxidation processes of hydrogen. This study aimed to the synthesis of nanostructured materials CuNbC and niobium and copper oxide from precursor tris(oxalate) oxiniobate ammonium hydrate through gas-solid and solid-solid reaction, respectively. Both reactions were carried out at low temperature (1000°C) and short reaction time (2 hours). The niobium carbide was produced with 5 % and 11% of copper, and the niobium oxide with 5% of copper. The materials were characterized by X-Ray Diffraction (XRD), Rietveld refinement, Scanning Electron Microscopy (SEM), X-Ray Fluorescence Spectroscopy (XRF), infrared spectroscopy (IR), thermogravimetric (TG) and differential thermal analysis (DTA , BET and particle size Laser. From the XRD analysis and Rietveld refinement of CuNbC with S = 1.23, we observed the formation of niobium carbide and metallic copper with cubic structure. For the synthesis of mixed oxide made of niobium and copper, the formation of two distinct phases was observed: CuNb2O6 and Nb2O5, although the latter was present in small amounts