Laédna Souto Neiva

Evaluation of the Cu Doping Effects in CeO2 Catalytic Supports Obtained by Combustion Reaction

This work has for aim to synthesize CeO2 catalytic supports doped with Cu2+ by combustion reaction method. Thus were obtained catalytic supports with the composition Ce1-xCuxO2 and the effect caused by doped element in the structure of the CeO2 was evaluated. The concentration value (x) of the Cu doped took over the values of 0.0; 0.3 and 0.5 mol. The catalytic supports developed were submitted to the structural characterization by X-ray diffraction, morphologic analysis by SEM and textural analysis by means of adsorption-dessorption of N2 by BET method. The results showed that the doped element (Cu) was not completely incorporated in the CeO2 structure and was evidenced that how much larger the quantity of Cu larger maid the disorder of the atomic structure of the obtained material. The analyzed supports present mesoporous nature structure.

The Importance of Natural Gas Reforming

Natural gas is a fossil fuel found in nature reserves, associated or not with petroleum. Its composition is a mixture of light hydrocarbons, generally alkanes, which are normally gaseous at room temperature. Methane is the most abundant gas, accounting for more than 85% of the natural gas, and the other constituents are light alkanes such as ethane, propane, butane, among others. The percentages of each constituent of natural gas vary depending on factors such as geological formation of the reservoir rock, as well as the type of organic matter that gave rise to the natural gas found. Recently, natural gas has attracted the interest of many researchers and the large amount of methane contained in natural gas has been considered an input in the production of other high-value products such as syngas and high purity hydrogen. Considering the global trend toward environmental preservation, which emphasizes clean and sustainable energy generation, it can be said that the interest of researchers for natural gas will increase significantly from now on (Odell & Rosing, 1983). The interest in natural gas is directly related to the search for alternatives to replace petroleum-based fuels and for generating energy from sources less aggressive to the environment. This behavior resulted in the intensification of research and exploration, particularly among developing countries. The result was not only the increase in proven oil reserves but also in its geographic expansion (the existence of reserves and the possibility of their exploitation must be proven by tests). Until 1970, these reserves were concentrated in a few regions of the world, like North America and the former Soviet Union (ANEEL, 2008). Awareness of the imminent scarcity of oil in the next decades is stimulating the search for a fuel that can partially replace petroleum-based fuels. Worldwide reserves of natural gas are under-exploited because they are not as valuable as the petroleum reserves. In some cases, when natural gas is associated with oil reserves, while the valuable petroleum is fully exploited, the associated gas of the same reserves is considered undesirable, volatilized into the atmosphere or burnt in the platform’s flare. Fortunately, though, this situation is gradually changing, and natural gas is getting more attention, due to the growing need to produce hydrogen from hydrocarbons. Among the fossil fuels, natural gas is the most suitable for this application (Fishtik et al., 2000). Energy generation is fundamental to the socioeconomic development of a country or region. Somehow, it is present in the entire chain of production, distribution and comsumption of goods and services. Equally important is the role of technology in the balanced and sustainable development of various economic sectors, especially power generation. The 3

Evaluation of Calcined Temperature on the Structural and Morphological Characterization of TiO2 Doped with Zr Nanopowders Obtained by the Pechini Method

Because of the unique properties that the system TiO2-ZrO2 has, this system has attracted great interest in catalytic circles. In general, the TiO2-ZrO2 oxides composites have a greater surface area and a stronger acidity when compared to the single oxide and they are used as catalysts supports for many catalytic reactions. This work is to evaluate the effect of calcined temperature in structural and morphological characteristics of Ti1-xZrxO2 nanopowders obtained by Pechini method. For this study, the doping value was 0.25 moles of Zr. The powders were calcined at temperature of 500 to 900°C for one hour. The powders were characterized by XRD, SEM and BET. The X-ray diffraction showed that the powders present a TiO2 anatase phase and another of ZrO2 tetragonal. The crystallite size ranged from 4.8 to 14.6 nm for the temperature of 500 to 900°C, respectively. The analysis of scanning electron microscopy showed soft homogeneous agglomerates with particles around 100 nm. The main particles sizes by BET were ranged from 10 to 20 nm, showing that the synthesis is effective to obtain nanometric powders.

Reforma catalítica do metano sobre 1,5%Ni/α-Al2O3 dopado com elementos metálicos diferentes

The aim this work is to develop Ni catalysts supported on α-Al2O3 doped with the following metallic elements: iron, zinc, cerium and zirconium. The catalytic supports composed by α-Al2O3 doped were obtained by means method of synthesis of the combustion reaction and the nickel in the active catalytic species condition, was deposited over the supports by the method of wet impregnation. The structural characterizations, as well as the evaluation of performance of these ceramic materials in catalytic reaction of steam reforming of methane are among the objectives of this work. The catalytic supports synthesized showed crystalline structures with dimensions of its pores in the range of microporosity associated with the presence of mesopores. The catalytic evaluation of the samples obtained in this work, in reaction of steam reforming of methane revealed that the catalytic performance of this materials is influenced by physical characteristics her structure, such as, value of surface area of the particles that make up the structure, but also, the average diameter of pores of the same. Among the four samples developed in this work, the sample of α-Al2O3 doped with zinc containing 1.5% Ni as active catalytic species, showed percentages of conversion of methane higher than the other samples.

Ni/α-Al2O3 Catalysts Modified with ZnO and Fe2O3 for Steam Reforming of the Natural Gas

This work has as objective the synthesis for the method by combustion reaction of catalytic supports of α-Al2O3 modified with ZnO and Fe2O3 with and without impregnation of the species it activates (Ni) and your structural and morphologic characterization. The catalytic supports were obtained by method of the synthesis da combustion reaction. The catalytic supports were characterized by XRD, adsorption of nitrogen by BET method and infrared. The results of XRD showed the formation of powders with high cristalinity, characteristic picks of difraction of the phase α-Al2O3 indicating that there was the partial substitution of the ions of Al3+ for Zn2+ and Fe3+ in the hexagonal net of the alumina. The impregnation of the nickel promoted an increasing in the size of the particles, this carried to reduction of the superficial area of the same, of the volume and of the diameter of the pores of the structure of the material. Were accomplished catalytics tests in row of seats scale. The result of catalytic tests showed that the developed catalysts in this work were efficient in the methane conversion process.

Avaliação de sistemas catalíticos à base de CuO/CeO2 na reação de oxidação preferencial do CO em presença de H2

The preferential CO oxidation (PROX) is the most suitable for the purification of gas streams rich in H2 method. Catalysts CuO/CeO2 have been developed and presented in the literature as a promising alternative for the reaction preferential oxidation of CO - CO-PROX. The objective of this work is to synthesize catalysts based on CuO/CeO2 via Pechini synthesis method, characterize and analyze their structures and evaluate the catalytic performance of these materials used in CO-PROX reaction. Two samples of catalysts were developed based on CuO/CeO2, containing 0.1 mol and one containing 0.5 mole of CuO. Both synthesized samples proved suitable for use in processes of conversion of CO to CO2. However, the sample containing 0.1 mol CuO was catalytically more active than the sample containing 0.5 mol of the same active species.

Evaluation of Structural and Morphological Characteristics of the System Ni1-xZnxFe2O4 Obtained by Combustion Reaction

The synthesis by combustion reaction stands as an alternative technique for preparing powders with high purity level, nanometric particle size and low cost. Therefore, this study had as objective the synthesis and characterization of ferrite powders with nominal composition NI1-xZnxFe2O4 (x = 0.6, 0.7 and 0.8 mol) prepared by combustion reaction using urea as fuel. The influence of the quantity of zinc in the final characteristics of the powders was also investigated. The powders were characterized by X-ray diffraction (XRD), nitrogen adsorption (BET) and scanning electron microscopy (SEM). All compositions resulted in nanometric powders of Ni-Zn ferrites with direct formation of the inverse spinel phase, showing the effectiveness of the synthesis method applied. The increase of zincs concentration caused an increase in surface area, ranging 4 m2g-1 from 23 m2 g-1. And the SEM micrographs show that the powders have thinner particle morphology with increasing zinc content.

Synthesis of ZnAl2O4 Catalytic Support by Combustion Reaction Using Different Fuels

This work shows the influence of the fuels aniline, carbohydrazide and glycine on structural and morphological characteristics of ZnAl2O4 synthesized by combustion reaction. Samples were prepared according to the propellants and explosives theory using a vitreous silica crucible and a muffle furnace as heating source. During the synthesis was measured the time and temperature of the reaction. After The samples were structurally and morphologically characterized by the following techniques: XRD, nitrogen adsorption / desorption (BET / BJH), and SEM. The higher temperature was achieved by the synthesis using aniline, whose value was of 876°C. XRD results showed that all the samples presented the ZnAl2O4 spinel as majority phase and, ZnO and Al2O3 as segregated phases. The samples also showed low surface area, varying of 23.6 to 28.7 m2/g, and particle size of 45 to 55 nm, besides mesoporous characteristic and irregular agglomerates formation.

Influence of Preparation Method of the CeO2 over their Structural Characteristics

The aim this work is to synthesize the CeO2 in the ceramic powder form through three different methods of synthesis, they are: method of combustion, Pechini method and hydrothermal method. Will be evaluated the influence exerted by these methods of preparing of the metallic oxide on the structural features presented in the same. Three samples of CeO2 were synthesized in this work, they were analysed by x-ray diffraction, SEM and adsorption and desorption of N2 by BET method. According to the results has been observed that the synthesis method has great influence on the structural characteristics of CeO2 obtained. The sample of CeO2 synthesized by Pechini method showed a structure with a higher percentage of crystallinity and average pore diameter smaller when compared to samples of CeO2 synthesized by means of the combustion method and of the hydrothermal method. The sample synthesized by the combustion reaction method presented larger agglomerated of unitary particles.

Catalisadores cerâmicos à base de CuO/CeO2 aplicados na reação de oxidação preferencial do CO

The preferential oxidation of CO (PROX) is the most suitable method for the purification of gas streams rich in H2. CuO/CeO2 catalysts have been developed and presented as a promising alternative for the preferential oxidation reaction of CO - CO-PROX. The aim this work is to synthesize CuO/CeO2 ceramic catalysts by means of the synthesis Pechinis method, characterization and analysis the structures and evaluation of the performance of these materials used in catalytic reaction of CO-PROX. Two samples ceramic catalysts based on CuO/CeO2 were synthesized, the first containing 0.1 mol of CuO and the second containing 0.5 mol of CuO. According to the results, both synthesized samples were ready to be used in a process of converting CO to CO2. However, the sample containing 0.1 mol of CuO was more active than the catalyst sample containing 0.5 mol of the same active species.