Síntese e caracterização de zeólita beta hierarquizada e materiais híbridos micro-mesoporosos aplicados no craqueamento de PEAD

A catalyst of great interest to the scientific community tries to unite the structure of ordered pore diameter from mesoporous materials with the properties of stability and acid activity to microporous zeolites. Thus a large number of materials was developed in the past decades, which although being reported as zeolites intrinsically they fail to comply with some relevant characteristics to zeolites, and recently were named zeolitic materials of high accessibility. Among the various synthesis strategies employed, the present research approaches the synthesis methods of crystallization of silanized protozeolitic units and the method of protozeolitic units molded around surfactant micelles, in order for get materials defined as hierarchical zeolites and micro-mesoporous hybrid materials, respectively. As goal BEA/MCM-41 hybrid catalysts with bimodal pore structure formed by nuclei of zeolite Beta and cationic surfactant cetyltrimethylammonium were developed. As also was successfully synthesized the hierarchical Beta zeolite having a secondary porosity, in addition to the typical and uniform zeolite micropores. Both catalysts were applied in reactions of catalytic cracking of high density polyethylene (HDPE), to evaluate its properties in catalytic activity, aiming at the recycling of waste plastics to obtain high value-added raw materials and fuels. The BEA/MCM-41 hybrid materials with 0 days of pre-crystallization did not show enough properties for use in catalytic cracking reactions, but they showed superior catalytic properties compared to those ordered mesoporous materials of Al-MCM-41 type. The structure of Beta zeolite with hierarchical porosity leads the accessibility of HDPE bulky molecules to active centers, due to high external area. And provides higher conversion to hydrocarbons in the gasoline range, especially olefins which have great interest in the petrochemical industry

Síntese de catalisadores nanoporosos na ausência total e parcial de direcionadores orgânicos para pirólise catalítica de óleos pesados e intermediários

The processing of heavy oil produced in Brazil is an emergency action and a strategic plan to obtain self-sufficiency and economic surpluses. Seen in these terms, it is indispensable to invest in research to obtain new catalysts for obtaining light fraction of hydrocarbons from heavy fractions of petroleum. This dissertation for the degree of Doctor of Philosophy reports the materials preparation that combine the high catalytic activity of zeolites with the greater accessibility of the mesoporosity, more particularly the HZSM-5/MCM-41 hybrid, done by synthesis processes with less environmental impact than conventional ones. Innovative methodologies were developed for the synthesis of micro-mesoporous hybrid material by dual templating mechanism and from crystalline zeolitic aluminosilicate in the absence of organic template. The synthesis of hybrid with pore bimodal distribution took place from one-single organic directing agent aimed to eliminate the use of organic templates, acids of any kind or organic solvents like templating agent of crystalline zeolitic aluminosilicate together with temperature-programmed microwave-assisted, making the experimental procedures of preparation most practical and easy, with good reproducibility and low cost. The study about crystalline zeolitic aluminosilicate in the absence of organic template, especially MFI type, is based on use of H2O and Na+ cation playing a structural directing role in place of an organic template. Advanced characterization techniques such as X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Highresolution Transmission Electron Microscopy (HRTEM), Adsorption of N2 and CO2, kinetic studies by Thermogravimetric Analysis (TGA) and Pyrolysis coupled to Gas Chromatography/Mass Spectrometry (Pyrolysis-GC/MS) were employed in order to evaluate the synthesized materials. Achieve the proposed objectives, has made available a set of new methodologies for the synthesis of zeolite and hybrid micro-mesoporous material, these suitable for catalytic pyrolysis of heavy oils aimed at producing light fraction

Síntese e caracterização de niobiosilicatos para produção de biocombustível

The mesoporous materials has been an special attention, among them was discovered in the 1990´s the mesoporous molecular sieve of SBA-15 type. The good features of the SBA- 15 makes this material very promising in catalysis, however, due to the absence of native active sites, it has low catalytic activity. In this way, different metals and oxides have been included in this molecular sieve as a means of introducing active sites and increase its catalytic activity. Among the oxides that are being researched, there is the niobium oxide, which presents strong acid sites and exists in abundance. Brazil is the largest producer of the mineral. On the other hand, the production of biofuels has been desired, but it requires the development of new catalysts for this purpose. The aim of this work was to develop silicate of niobium by impregnation and by new synthesis method for application in the cracking of moringa oil. The methodology consisted of inserting the niobium oxide either by postsynthesis process using wet impregnation and direct insertion. For direct insert a new method was developed for pH adjustment, being tested different pH, and the pH 2.2 was used different ratios of Si/Nb. The materials were characterized by different techniques such as: XRD, N2 adsorption, SEM, EDS, UV-visible, TG/DTG, DSC, TEM, acidity by thermodesorption of n-butilamine and FTIR. After this part of the catalysts developed by the two methods were tested in the thermocatalytic cracking of moringa oil, being used a simple distillation. All silicates of Niobium obtained showed a highly ordered structure, having high specific areas, good distribution of pore diameters, beyond present a morphology in the form of fibers. In the catalysts after synthesis was observed that the niobium inserted has so as octahedrally and tetrahedrally coordinated, demonstrating that there were also oxides formed on the external surface of SBA-15. The materials obtained in the direct synthesis are only tetrahedrally coordinated. The new synthesis method of pH adjusting by using the buffer solution for it, proved to be very efficient for the production of such materials, because the materials obtained showed characteristics and structures similar to the molecular sieve of SBA-15 type. Among the pH tested the material that presented better characteristics was synthesized at pH 2.2. The application of these materials in catalytic cracking showed a higher formation of organic liquids when compared to thermal cracking, in addition to significantly reducing the acidity and residues formed, demonstrating that the use of silicates of Niobium increases both the conversion and the selectivity of the products.

Elaboração de pós de ferrita de cobalto, CoFe2O4, nanoestruturados e hierarquizados: influência da morfologia sobre a detecção e oxidação catalítica de gases poluentes

This thesis is part of research on new materials for catalysis and gas sensors more active, sensitive, selective. The aim of this thesis was to develop and characterize cobalt ferrite in different morphologies, in order to study their influence on the electrical response and the catalytic activity, and to hierarchize these grains for greater diffusivity of gas in the material. The powders were produced via hydrothermal and solvothermal, and were characterized by thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, transmission electron microscopy (electron diffraction, highresolution simulations), and energy dispersive spectroscopy. The catalytic and electrical properties were tested in the presence of CO and NO2 gases, the latter in different concentrations (1-100 ppm) and at different temperatures (room temperature to 350 ° C). Nanooctahedra with an average size of 20 nm were obtained by hydrothermal route. It has been determined that the shape of the grains is mainly linked to the nature of the precipitating agent and the presence of OH ions in the reaction medium. By solvothermal method CoFe2O4 spherical powders were prepared with grain size of 8 and 20 nm. CoFe2O4 powders exhibit a strong response to small amounts of NO2 (10 ppm to 200 ° C). The nanooctahedra have greater sensitivity than the spherical grains of the same size, and have smaller response time and shorter recovery times. These results were confirmed by modeling the kinetics of response and recovery of the sensor. Initial tests of catalytic activity in the oxidation of CO between temperatures of 100 °C and 350 °C show that the size effect is predominant in relation the effect of the form with respect to the conversion of the reaction. The morphology of the grains influence the rate of reaction. A higher reaction rate is obtained in the presence of nanooctahedra. In order to improve the detection and catalytic properties of the material, we have developed a methodology for hierarchizing grains which involves the use of carbonbased templates.

Desenvolvimento de material BaCexPr1-xO3 (0 ≤ X ≤ 1) com estrutura perovskita para oxidação catalítica do CO a CO2 em reator de leito fixo

Barium Cerate (BaCeO3) is perovskite type structure of ABO3, wherein A and B are metal cations. These materials, or doped, have been studied by having characteristics that make them promising for the application in fuel cells solid oxide, hydrogen and oxygen permeation, as catalysts, etc .. However, as the ceramic materials mixed conductivity have been produced by different synthesis methods, some conditions directly influence the final properties, one of the most important doping Site B, which may have direct influence on the crystallite size, which in turn directly influences their catalytic activity. In this study, perovskite-type (BaCexO3) had cerium gradually replaced by praseodymium to obtain ternary type materials BaCexPr1-xO3 and BaPrO3 binaries. These materials were synthesized by EDTA/Citrate complexing method and the material characterized via XRD, SEM and BET for the identification of their structure, morphology and surface area. Moreover were performed on all materials, catalytic test in a fixed bed reactor for the identification of that person responsible for complete conversion of CO to CO2 at low operating temperature, which step can be used as the subsequent production of synthesis gas (CO + H2) from methane oxidation. In the present work the crystalline phase having the orthorhombic structure was obtained for all compositions, with a morphology consisting of agglomerated particles being more pronounced with increasing praseodymium in the crystal structure. The average crystal size was between 100 nm and 142,2 nm. The surface areas were 2,62 m²g-1 for the BaCeO3 composition, 3,03 m²g-1 to BaCe0,5Pr0,5O3 composition and 2,37 m²g-1 to BaPrO3 composition. Regarding the catalytic tests, we can conclude that the optimal flow reactor operation was 50 ml / min and the composition regarding the maximum rate of conversion to the lowest temperature was BaCeO3 to 400° C. Meanwhile, there was found that the partially replaced by praseodymium, cerium, there was a decrease in the catalytic activity of the material.

Catalisadores bifuncionais à base de silicoaluminofosfato e fosfatos de nióbio para emprego em reações de hidroisomerização e hidrocraqueamento do n-hexadecano

Lubricants and cutting middle distillates typically have large amounts of n-paraffins to increase its freezing point and fluidity. Accordingly, the removal of n-paraffins of long chain lubricants oils and diesel is essential to get a product with good cold flow properties. The development of new catalysts, which exhibit thermal stability and catalytic activity for the hydroisomerization reaction is still a challenge. Thus, silicoaluminophosphates (SAPO) were synthesized by different routes. Have been used also post-synthesis treatment for obtaining hybrid structures and others synthesis have been carried out with mesoporous template (soft and hard-template). Therefore, SAPO have been impregnated with H2PtCl6 solution by the incipient wetness method. Then assessments of catalytic activities in hydroisomerization and hydrocracking reactions of hexadecane have been held. Besides SAPO, niobium phosphate - NbP - were also impregnated with platinum and evaluated in the same reaction. After impregnation, these catalysts have been characterized by X-ray diffraction (XRD), nitrogen adsorption, infrared spectroscopy with adsorbed pyridine (IV-PY), scanning electron microscopy (SEM) and resonance nuclear magnetic 29Si (29Si-NMR). The characterization results by XRD have shown that it has been possible to obtain mesoporous SAPOs. However, for the syntheses with soft template there was collapse of the structure after removal of the organic template. Even so, these catalysts have been actives. It was possible to obtain hybrid materials through the synthesis of SAPO-11 made with hard templates and by means of post-synthesis treatments samples of SAPO-11. Moreover, NbP has shown characteristic XRD of amorphous materials, with high acidity and were active in the conversion of hexadecane.

Catalisadores bifuncionais à base de silicoaluminofosfato e fosfatos de nióbio para emprego em reações de hidroisomerização e hidrocraqueamento do n-hexadecano

Lubricants and cutting middle distillates typically have large amounts of n-paraffins to increase its freezing point and fluidity. Accordingly, the removal of n-paraffins of long chain lubricants oils and diesel is essential to get a product with good cold flow properties. The development of new catalysts, which exhibit thermal stability and catalytic activity for the hydroisomerization reaction is still a challenge. Thus, silicoaluminophosphates (SAPO) were synthesized by different routes. Have been used also post-synthesis treatment for obtaining hybrid structures and others synthesis have been carried out with mesoporous template (soft and hard-template). Therefore, SAPO have been impregnated with H2PtCl6 solution by the incipient wetness method. Then assessments of catalytic activities in hydroisomerization and hydrocracking reactions of hexadecane have been held. Besides SAPO, niobium phosphate - NbP - were also impregnated with platinum and evaluated in the same reaction. After impregnation, these catalysts have been characterized by X-ray diffraction (XRD), nitrogen adsorption, infrared spectroscopy with adsorbed pyridine (IV-PY), scanning electron microscopy (SEM) and resonance nuclear magnetic 29Si (29Si-NMR). The characterization results by XRD have shown that it has been possible to obtain mesoporous SAPOs. However, for the syntheses with soft template there was collapse of the structure after removal of the organic template. Even so, these catalysts have been actives. It was possible to obtain hybrid materials through the synthesis of SAPO-11 made with hard templates and by means of post-synthesis treatments samples of SAPO-11. Moreover, NbP has shown characteristic XRD of amorphous materials, with high acidity and were active in the conversion of hexadecane.

Síntese e caracterização de cerâmicas nanométricas para produção de gás de síntese

In this work, ceramic powders belonging to the system Nd2-xSrxNiO4 (x = 0, 0.4, 0.8, 1.2 and 1.6) were synthesized for their use as catalysts to syngas production partial. It was used a synthesis route, relatively new, which makes use of gelatin as organic precursor. The powders were analyzed at several temperatures in order to obtain the perovskite phase and characterized by several techniques such as thermal analysis, X-rays diffraction, Rietveld refinement method, specific surface area, scanning electron microscopy, energy dispersive spectroscopy of X-rays and temperature programmed reduction. The results obtained using these techniques confirmed the feasibility of the synthesis method employed to obtain nanosized particles. The powders were tested in differential catalytic conditions for dry reforming of methane (DRM) and partial oxidation of methane (POM), then, some systems were chosen for catalytic integrals test for (POM) indicating that the system Nd2-xSrxNiO4 for x = 0, 0.4 and 1.2 calcined at 900 °C exhibit catalytic activity on the investigated experimental conditions in this work without showing signs of deactivation

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

Síntese, caracterização e aplicação de LaSBA-15 e como catalisador para obtenção de biodiesel de soja via rota etílica

Biodiesel is an alternative fuel, renewable, biodegradable and nontoxic. The transesterification of vegetable oils or animal fat with alcohol is most common form of production of this fuel. The procedure for production of biodiesel occurs most commonly through the transesterification reaction in which catalysts are used to accelerate and increase their income and may be basic, acid or enzyme. The use of homogeneous catalysis requires specific conditions and purification steps of the reaction products (alkyl ester and glycerol) and removal of the catalyst at the end of the reaction. As an alternative to improve the yield of the transesterification reaction, minimize the cost of production is that many studies are being conducted with the application of heterogeneous catalysis. The use of nano-structured materials as catalysts in the production of biodiesel is a biofuel alternative for a similar to mineral diesel. Although slower, can esterify transesterified triglycerides and free fatty acids and suffer little influence of water, which may be present in the raw material. This study aimed at the synthesis, characterization and application of nano-structured materials as catalysts in the transesterification reaction of soybean oil to produce biodiesel by ethylic route. The type material containing SBA-15 mesoporous lanthanum embedded within rightly Si / La = 50 was used catalyst. Solid samples were characterized by X-ray diffraction, thermogravimetric analysis, infrared spectroscopy, nitrogen adsorption and desorption. For the transesterification process, we used a molar ratio of 20:1 alcohol and oil with 0.250 g of catalyst at 60°C and times of 6 hours of reaction. It was determined the content of ethyl esters by H-NMR analysis and gas chromatography. It was found that the variable of conversion obtained was 80%, showing a good catalytic activity LaSBA-15 in the transesterification of vegetable oils via ethylic route