Normanda Lino de Freitas

Influence of Fuel in the Synthesis of ZnAl2O4 Catalytic Supports by Combustion Reaction

The aim of this work is to evaluate the influence of fuel in the synthesis of ZnAl2O4 catalytic supports by combustion reaction. For this, it was used the fuels: urea, carbohidrazide, glycine and aniline. The total amount of reagents was calculated according to the theory of propellants and explosive using urea in the stoichiometric proportion (Φe = 1). The structural and morphological characteristics of the powders were evaluated by XRD, FTIR, TEM, SEM and particle size distribution. The results from XRD showed the formation of the normal cubic spinel structure. The powders presented nanosized particles with narrow agglomerates size distribution. The powders prepared with urea showed better value of surface area and smaller crystallite size.

Combustion synthesis of α-Al2O3 powders

Among ceramic materials, the alumina has high importance because of its characteristics of resistance and refractory. The possibility to improve the final characteristics of this material, open possibilities for new applications. The aim of this work is to synthesize (α-Al2O3) alumina powders by combustion reaction and to evaluate the effect of the urea content in the final characteristics of the α-Al2O3 powders. Three compositions were studied : a) stoichiometric, b) with 10% of urea reduction and c) with 20% of urea reduction. The initial solution composition was based on the total valence of the reagents by using chemical concepts of the propellant. This powders were characterized by X-ray diffraction (XRD), granulometric determination by laser diffraction, nitrogen adsorption by BET, scanning electron microscopy (SEM), infrared spectroscopy (IR) and helium picnometer. The results showed that the urea reduction change the temperature of the reaction from 525 to 463oC , the characteristics of the powders, and principally the reduction of the particles size.

Membranas cerâmicas assimétricas tubulares: influência do tempo de deposição da camada filtrante na morfologia das membranas

Esse trabalho tem como objetivo obter membranas cerâmicas assimetricas para aplicacao em processos de microfiltracao e avaliar a influencia do tempo de deposicao (5 e 10 s) de uma dispersao de argila sobre um suporte tubular de alumina comercial e bentonita. O suporte tubular foi caracterizado por microscopia otica e eletronica de varredura e por porosimetria. A membrana assimetrica foi caracterizada por microscopia eletronica de varredura e por porosimetria. Os resultados mostraram suportes porosos com espessura de 1092µm, diâmetro medio de poro de 0,99 uf0b5uf06d e porosidade de 39%. A membrana assimetrica foi obtida com sucesso para os tempos de deposicao avaliados, sendo classificada para aplicacoes em processos de microfiltracao atingindo diâmetro medio de poro de 0,25 µm e porosidade de 35%.

Influence of the External Heating Type in the Morphological and Structural Characteristics of Alumina Powder Prepared by Combustion Reaction

The aim of this work is to evaluate the influence of the external heating in the morphological and structural characteristics of the alumina powder prepared by combustion reaction. It was evaluated different types of external heating: muffle oven, microwave oven and ceramic plate with electrical spiral resistance. The powders were prepared according to the propellants and explosives theory, using urea in the stoichiometric proportion (Φe = 1). During the synthesis parameters such as flame combustion time and temperature were measured. The structural and morphological characteristics of the powders were evaluate by XRD, particle size distribution, SEM and nitrogen adsorption (BET). The results showed the production of uf061-alumina as unique phase and formed by agglomerates with irregular plate shape of thin particles for all studied conditions. The powders prepared by electrical oven presented small particle size, with narrow agglomerates size distribution.

Effect of Sintering Temperature on Membranes Manufactured with Clays for Textile Effluent Treatment

The aim of this work is to use cheap raw materials, such as kaolin and ball clay, for the manufacture of ceramic membranes for application in effluent treatment from textile industry and to evaluate the influence of sintering temperature in the structural and morphological characteristics of those membranes. The ceramic mass was characterized by X-ray diffraction and thermal analysis. The membranes were characterized by scanning electron microscopy, Hg porosimetry, and water permeability with desalinated water. The variation in the sintering temperature directly affected the structural and morphological characteristics of the membranes. The increase in sintering temperature of the membranes has raised the average pores diameter from 0.116 to 0.179u2009µm but decreased the porosity of the membrane, from 40.30 to 25.16% for temperatures from 900 to 1100°C, respectively. The reduction in porosity of the membrane affected the water permeated flux and decrease from 35.82u2009Kg/h·m2 (at 1000°C) to 15.68u2009Kg/h·m2 (at 1100°C). All the membranes have been applied with success in the effluent treatment from textile industry, resulting in the decrease in turbidity and discoloration, reaching approximately 100% of rejection of solid particles.

Combustion Synthesis of ZnAl2O4 Catalyst Using Glycine as Fuel for the Esterification and Transesterification of Soybean Oil: Influence the Form of Heating

The aim of this work is to evaluate the esterification and transesterification activity of ZnAl2O4 catalysts obtained by different ways of heating during the combustion synthesis using glycine as fuel. Samples were prepared according to the propellants and explosives theory using a vitreous silica crucible as container, and as heating source, plate, muffle furnace and microwave oven. After synthesis, the samples were structural and morphologically characterized by: XRD, nitrogen adsorption and carbon content analysis, and employed in the esterification and transesterification reactions, the percentage of biodiesel formed (FAME) was determined by gas chromatography. The samples obtained on the plate, muffle furnace and microwave showed that even using different heating ways, led to the formation of ZnAl2O4 as majority phase, with crystallite sizes of 11, 15 and 10 nm, respectively. The samples present values of surface area ranging from 16 to 77 m2/g, particle size from 17 to 81 nm, and carbon content lower than 11%. The forms used for heating influenced the esterification and transesterification reactions, showing that there was a gap in the production of biodiesel, which is a promising indication that this material has potential to be used as catalysts on the biodiesel production.

Synthesis of Ni-Zn Ferrite Catalysts by Combustion Reaction Using Different Fuels

The aim of this work is to evaluate the effect of different fuels in the preparation of Ni-Zn ferrites by combustion reaction. The catalysts were prepared according to the propellants chemistry, in stoichiometric composition, using a vitreous silica container. Carbohydrazine, monohydrated citric acid and glycine fuels were used. During the synthesis parameters as flame combustion time and temperature were measured. The structural and morphological characteristics of the powders were evaluated by XRD, textural analysis by nitrogen adsorption and SEM. The fuel monohydrated citric acid presented the greatest time and temperature of combustion reaction. The results show that the type of fuel changed the final characteristics of the powders. The XRD results showed the formation of Ni-Zn ferrite phase for all fuels used in this study. The powders prepared with carbohydrazine resulted in largest value of surface area. All powders showed morphology constituted by soft agglomerates of nanoparticles.

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.

Porous Anisotropic Alumina Ceramic Membrane: Preparation and Characterization

Through different field of application and productive growth that membrane technology has been presented in the last years, the aim of this work is to prepare and characterize anisotropic porous ceramic membrane. The membrane were done with alumina, prepared by combustion reaction in microwave oven from urea as combustible and after deposited on support based on a commercial alumina. The results showed that it was obtained α-alumina as unique phase with average agglomerate size of 10µ and surface area of 33 m2/g. The alumina morphology was constituted by pre-sintering particles with hard agglomerates and/or aggregates. In relation to the membranes, it was observed a longitudinal section without cracks and uncovers support surface, also it can be observed grain formation well distributed and a layer of alumina with approximately 35.25µm. In relation to the permeate flux, the membrane presented initially values relatively high that is decrease with the permeation time, due to adsorption of water in the internal surface of the pores of the membrane, experiencing a decrease in size.

Evaluation of the Thickness and Permeability in Asymmetric Membranes of TiO2 Supported on Alumina

The aim of this study is to evaluate the thickness and permeability of the membranes of TiO2 supported on Al2O3. The TiO2 samples were prepared by combustion reaction method using monohydrated citric acid, aniline and urea as fuel. It was prepared three samples with different morphological characteristics. The membranes were prepared by dip coating, and characterized by scanning electron microscopy (SEM), permeate flux and turbidity in laboratory test. The membrane obtained with urea presented layer formed at 16 µm of thickness. For membrane obtained with powder from citric acid and aniline do not presented layer formation. The membrane obtained with samples synthesized urea showed: higher permeated flux (185.46 kg/ h.m ²), higher particle rejection (97%) and lower turbidity (0.99 NTU) with contaminated water. The membrane obtained with powders from citric acid and aniline showed: permeated flux of 128.61 and 138.41 kg/h.m², rejection of 96 and 95% and turbidity of 1.33 and 1.13 NTU, respectively.