Esterificação de ácidos graxos utilizando zircônia sulfatada e compósitos carvão ativado/zircônia sulfatada como catalisadores

In this work sulfated zirconia (SZr) and activated carbon/SZr composites produced by impregnation method with or without heating treatment step (CABC/SZr-I and CABC/SZr-I SC) and by the method of synthesis of SZr on the carbon (CABC/SZr-S) was used as catalysts in the esterification reactions of fatty acids. The SZr presented very active, conversions higher than 90% were obtained after 2 h of reaction. The activity of the composite CABC/SZr-I20%SC was up to 92%, however, this was directly related to time and temperature reactions. CABC/SZr-I and CABC/SZr-S were less active in esterification reactions, what could be attributed to its low acidity

Cerâmicas porosas a base de zircônia na forma de filmes suportados preparados a partir de emulsões

Pós-graduação em Química - IQ

Produção de biodiesel por catálise heterogénea

Mestrado em Engenharia Química. Ramo optimização energética na indústria química.

Produção de biodiesel a partir de pastas de gordura e resíduo de glicerol

O principal objectivo deste trabalho consistiu na produção de biodiesel a partir de resíduos fornecidos pela Empresa SOCIPOLE, S.A. Esta, forneceu, pastas de gordura (depósito formado nos óleos usados), só aproveitadas pela empresa para a produção de sabões, e resíduo de glicerol proveniente da produção de biodiesel. Com as pastas de gordura, foi feito um estudo onde se variaram alguns parâmetros, tais como: o tipo de reactor, catalisador, temperatura, agitação, tempo de reacção, razão molar gordura:metanol e condições de secagem. O estudo mais pormenorizado foi efectuado com o NaOH, como catalisador. Foram feitos vários ensaios para os tempos de reacção de 30minutos, 1hora e 2horas, a 65ºC e razão molar gordura:metanol 1:6, tendo-se obtido respectivamente 86,7; 88,1 e 87,5% para o teor de ésteres. No caso da resina catiónica forte como catalisador, aparentemente não houve reacção ao fim de 12h, enquanto no ensaio que utilizou o ácido sulfúrico, o teor de ésteres foi de 82,6%, ao fim de 12h com razão molar gordura:metanol igual a 1:11. Quanto à produção de biodiesel a partir do resíduo de ácidos gordos resultante da purificação do resíduo de glicerol, foi feito um estudo preliminar usando diferentes catalisadores, uma resina catiónica forte, ácido sulfúrico e zircónia sulfatada. Este resíduo continha cerca de 60% de ácidos gordos e aproximadamente 39% de ésteres metílicos. Dos três catalisadores usados, o que permitiu obter maior teor de ésteres foi a zircónia sulfatada, tendo-se obtido 82,9% trabalhando a 60ºC durante 18horas com agitação de 230rpm e razão molar ácidos gordos:metanol de 1:12 . O ensaio em que se obteve menor percentagem de ésteres (56,4%) foi com resina catiónica. Com as duas matérias-primas obteve-se sempre um teor de ésteres, no produto final, abaixo dos 96,5% estabelecidos pela Norma Europeia EN 14103. Estes resultados reflectem provavelmente a composição complexa das matérias-primas. As pastas de gordura podem conter compostos não esterificáveis, solúveis no biodiesel, ou mais dificilmente esterificáveis nas condições operacionais usadas. Já o resíduo de ácidos gordos apresenta uma cor escura o que indica a existência de compostos corados, talvez polímeros. Portanto, para se tirar conclusões fundamentadas é necessário fazer análises mais completas das pastas de gordura e do resíduo de ácidos gordos, assim como ao biodiesel produzido de forma a identificar as possíveis contaminações existentes nos produtos com esta proveniência.

Espumas cerâmicas produzidas pela conjugação dos processos sol-gel, aeração e emulsificação

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Respostas de culturas à adubação sulfatada e deposição de enxofre atmosférico

Solos com baixo teor de argila e matéria orgânica apresentam baixa disponibilidade de enxofre (S) e, por isso, as culturas podem responder à adubação sulfatada. No entanto, a mobilidade de S no perfil do solo e sua deposição atmosférica pela água da chuva dificultam o estabelecimento do nível de suficiência do nutriente no solo. Este trabalho objetivou avaliar a resposta de culturas à adubação sulfatada e quantificar o S atmosférico depositado no solo pela água da chuva. Os cultivos avaliados (mamoneira, trigo, feijão-de-porco e milheto) foram realizados entre 2006 e 2009, em um Argissolo Vermelho distrófico arênico. As doses de S aplicadas em cada cultivo foram de 0, 5, 10 e 20 kg ha-1, utilizando-se gesso agrícola como fonte de S. Avaliaram-se a produção de matéria seca e o acúmulo de S na parte aérea do milheto e do feijão-de-porco, e a produção e o teor de S nos grãos de mamona e de trigo. Determinou-se o teor de S disponível no solo até 60 cm de profundidade e a deposição de S pelas precipitações. A maior produção de grãos da mamona e de matéria seca do segundo cultivo de feijão-de-porco foi obtida com aplicação de 14,5±0,35 kg ha-1 de S. Mesmo com teores de S abaixo dos níveis de suficiência, não houve respostas do trigo, do milheto e do primeiro cultivo de feijão-de-porco à adubação sulfatada. O aporte de S atmosférico ao solo foi de 4,5 kg ha-1 ano-1 e pode ter contribuído para a ausência de resposta desses cultivos.

Preparação de sílica organofuncionalizada à base de zircônia e estudos de adsorção de hidrocarbonetos policíclicos aromáticos e pesticidas organoclorados

O trabalho realizado conjuga informações de preparação e caracterização de materiais à base de sílica, com avaliação de possível aplicação potencial na área de química analítica ambiental. As sílicas organofuncionalizadas foram preparadas segundo 2 métodos: grafting e sol-gel. Os 4 sólidos obtidos por grafting diferem essencialmente na natureza da esfera de coordenação em torno do centro metálico (átomo de zircônio), enquanto que os 2 sólidos obtidos pelo processo sol-gel são sólidos híbridos, contendo ligantes indenil, grupos silanóis e etóxidos na superfície, diferindo entre si pela presença de centro metálico. Os teores de metal, determinados por RBS, nas sílicas organofuncionalizadas ficaram em torno de 0,3 % para os sólidos preparados por grafting e 4,5 %,no caso, do sólido preparado por sol-gel. A análise por DRIFTS confirmou a presença dos ligantes orgânicos e, ainda, grupos silanóis residuais nos adsorventes preparados por grafting. A capacidade de adsorção das sílicas organofuncionalizadas foi avaliada frente a duas famílias de compostos: HPAs e pesticidas organoclorados. A identificação e quantificação dos HPAs foi conduzida através de cromatografia gasosa com detector seletivo de massas. Os resultados da capacidade de adsorção para os 16 HPAs prioritários não foram quantitativamente considerados satisfatórios, em parte devido à dificuldade de solubilidade em água. A determinação quantitativa da eficiência dos adsorventes sólidos, na pré-concentração/extração dos pesticidas organoclorados, foi realizada através da cromatografia gasosa com detector de captura de elétrons. Os resultados de recuperação, para os compostos organoclorados: heptacloro epóxido, dieldrin e endrin foram considerados satisfatórios e em concordância com valores encontrados com o adsorvente comercial LC-18. O lindano apresentou boa recuperação especificadamente nos adsorventes preparados por sol-gel. De uma forma geral, os resultados indicam a possibilidade de utilização futura dos adsorventes sólidos preparados em protocolos de pré-concentração/extração de organoclorados a nível de traços.

Atividades antinociceptiva e anti-inflamatória de uma fração rica em heterogalactana sulfatada extraída da alga codium isthmocladum (vickers 1905)

Sulfated polysaccharides comprise a complex group of macromolecules with a range of several biological activities, including antiviral activity, anticoagulant, antiproliferative, antiherpética, antitumor, anti-inflammatory and antioxidant. These anionic polymers are widely distributed in tissues of vertebrates, invertebrates and algae. Seaweeds are the most abundant sources of sulfated polysaccharides in nature. The green algal sulfated polysaccharides are homo or heteropolysaccharides comprised of galactose, glucose, arabinose and/or glucuronic acid. They are described as anticoagulant, anti-inflammatory, antiviral, anti-angiogenic, antitumor compounds. However, there are few studies about elucidation and evaluation of biological/pharmacological effects of sulfated polysaccharides obtained from green algae, for example, there is only one paper reporting the antinociceptive activity of sulfated polysaccharides of these algae. Therefore this study aimed to obtain sulfated polysaccharides of green seaweed Codium isthmocladum and evaluates them as potential antinociceptive agents. Thus, in this study, the total extract of polysaccharides of green alga C. isthmocladum was obtained by proteolytic digestion, followed by fractionation resulting in five fractions (F0.3, F0.5, F0.7, F0.9 and F1.2) by sequential precipitation with acetone. Using the test of abdominal contractions we observed that the fraction F0.9 was the most potent antinociceptive aompound. F0.9 consists mainly of a sulfated heterogalactana. More specific tests showed that Fo.9 effect is dose and time dependent, reaching a maximum at 90 after administration (10 mg / kg of animal). F0.9 is associated with TRPV1 and TRPA1 receptors and inhibits painful sensation in animals. Furthermore, F0.9 inhibits the migration of lymphocytes induced peritonitis test. On the other hand, stimulates the release of NO and TNF-α. These results suggest that F0.9 has the potential to be used as a source of sulfated galactan antinociceptive and anti-inflammatory

Estudo da zircônia reforçado com alumina

Ceramics materials have good properties including chemical stability, high hardness and wear resistance. Moreover, due to its fragility, can suffer failure under relatively low levels of tension. Actually zirconia is the material of choice in metal free dental prostheses used in dentistry due its inertia in physiological environment, good bending strength, hardness and fracture toughness. The alumina and mixed tungsten and titanium carbides additions, acting as reinforcement elements in the zirconia matrix, have as their main objective the improvement of mechanical properties of this material. In this work, samples of zirconia, zirconia with 30% wt of alumina and zirconia with 30% wt mixed carbides were analyzed. The samples were sintered by uniaxial hot pressing on 30 MPa pressure, for 1 hour in an argon atmosphere. They were physically characterized by porosity and density measurements, and mechanically by 3-points bending strength and Vickers microhardness. The X-ray diffraction was used for the phase identifications and microstructure was examined by scanning electron microscopy (SEM). The addition of mixed carbides as reinforcement elements in zirconia matrix provides improvements in all properties analyzed in this work. The alumina addition has dropped the zirconia strength, although it caused improvement in other properties

Estruturas cerâmicas a base de zircônia e alumina utilizadas na confecção de infra - estruturas para coroas e pontes fixas

The continuous advances in ceramic systems for crowns and bridges infrastructure getting researchers and manufacturers looking for a material that has good mechanical properties and aesthetic. The purpose of this study was to verify in which composition and sintering temperature the ceramic system for infrastructure composed of alumina and zirconia would have the best mechanical properties. With this objective we made in UFRN laboratories 45 test bodies in the form of rectangular bars with the following dimensions: 30mm x 8mm x 3mm, where we separated by the sintering temperature: 1200°C, 1300ºC and 1400ºC, and by comp osition: 33% Zirconia + 67% Alumina; 50% Zirconia + 50% Alumina and 25% Zirconia + 75% Alumina, these test bodies were not infiltrated with glass. Also, were made nine test bodies by a technical from a laboratory with a commercial ceramic system: in the Ceram Zircônia (Vita - Zahnfabrik) with the following dimensions: 20mm x 10mm x 0.5mm, these test bodies following all recommendations of the manufacturer and were infiltrated with glass. Were realized optical and electronic microscopy analyses, hardness testing, resistance to bending in three points, porosity and bulk density. After analysis of the results we verified that with the increasing of sintering temperature, increased the value of resistance to bending, but with the same temperature there was no significant difference between the different compositions, samples made with the commercial ceramic that were infiltrated, presented a resistance to bending six times greater than the samples sintered to 1400°C and which have not been infiltra ted. There was no significant difference between the values of apparent porosity for the samples made in UFRN laboratories, but the samples of commercial ceramic obtained 0% in porosity apparent value. In tests of Rockwell Hardness there is an increase in the value of Hardness, with the increase of sintering temperature for the samples not infiltrated. Samples infiltrated showed similar values as the samples sintered in 1400°C. There was no significant difference between the values of apparent density among samples manufactured in UFRN laboratories and samples made with a commercial ceramic

Estudo da influência da temperatura de brasagem nas uniões zircônia/aço inox 304 utilizando metalização mecânica

Metal-Ceramic (M/C) Zirconia-stainless steel interfaces have been processed through brazing techniques due to the excellent combination of properties such as high temperature stability, high corrosion resistance and good mechanical properties. However, some M/C interfaces show some defects, like porosity and cracks results in the degradation of the interfaces, leading even to its total rupture. Most of time, those defects are associated with an improper brazing parameters selection to the M/C system. In this work, ZrO2 Y-TZP and ZrO2 Mg - PSZ were joint with the stainless steel grade 304 by brazing using a eutectic silver-copper (Ag28Cu) interlayer alloy with different thermal cycles. Ceramic surfaces were previous mechanically metallized with titanium to improve adhesion of the system. The effect of temperature on the M/C interface was studied. SEM-EDS and 3 point flexural bend test were performed to evaluate morphology, chemical composition and mechanical resistance of the M/C interfaces. Lower thermal cycle temperatures produced better results of mechanical resistance, and more regular/ homogeneous reaction layers between braze alloy and metal-ceramic surfaces. Also was proved the AgCu braze alloy activation in situ by titanium

Caracterização de cerâmicas porosas de alumina reforçada com zircônia produzidas pelo método da réplica

Porous ceramics have many applications: thermal insulation, catalytic support, materials to fire protection, filters, and others. There are many techniques to production of ceramic filters. One technique to obtain ceramic filters is the replication method. This method consists in the impregnation of polymeric foam with ceramic slurry followed by a heating treatment that will burn out the organic elements and sintering of the material, resulting of a replication of the original foam. To perform their functions ceramic filters must satisfy mechanical requirements and permeability parameters (darcian k1 and no-darcian k2). The permeability and the strength of the ceramic material are dependent of the pore size and pore distribution. To the use at high temperatures the evaluation of mechanical properties in these temperatures is necessary. In this work the mechanical behavior of two commercial porous ceramics (10 and 40 poros per inch) was studied these materials were submitted to compression and four-point flexure test (room temperature, at 1000 °C, after thermal shock). Density and porosity measurements, permeability tests and microstructural analysis by scanning electronic microscopy (SEM) were realized. The Results showed that the decrease of mechanical strength of these materials, when submitted to thermal shock, occur for propagation of new cracks from cracks pre-existing and the permeability depends of the pore size

Síntese pelo método pechini e caracterização da zircônia dopada com cério e neodímio

In this study five compositions were synthesized zirconia doped with cerium and neodymium ions in the system Ce10-xNdx Zr90O2 with 0,5 ≤ x ≤ 4,0 using the Pechini method. The powders were characterized by thermogravimetric analysis, differential thermal analysis, infrared spectroscopy and X-ray diffraction, with application of Rietveld refinement of the calcination temperatures of 350ºC/3h and 30 minutes at 900ºC/3h. All compositions stabilized with a mixture of cubic and tetragonal phase zirconia. The samples were pressed into bars and sintered at 1500°C/3h and 1500°C/6h, being characterized by Xray diffraction, with application of the Rietveld refinement, density and porosity using Archimedes method, scanning electron microscopy and resistance the three point bending. It has been observed the increase in strength with increasing sintering temperature for the compositions x = 2,0 and x = 4,0. For x = 2,0 the main phase was the cubic with 92,56% with crystallite size of 0,56 μm, density and porosity of 96,82% from 1,36%. For x = 4,0 was a mixture of cubic and tetragonal phase with 21% and 37,98%, respectively. The crystallite size was 54,21 nm and 49,64 nm with a density porosity of 97,45% and 1,32% respectively. In the analysis of the fracture surface was observed a greater amount of grain fracture intragranular type, which contribute to increase the mechanical strength of the ceramic. Increased addition of the neodymium ion in the crystal lattice of the zirconium showed a nearly linear behavior with increasing mechanical strength of the zirconia ceramic. Was obtained a bending resistance of 537 ± 38 MPa for the composition x = 2,0 predominantly attributed to cubic phase with 92,56%

Influência de protocolos de jateamento na rugosidade da superfície de uma cerâmica de zircônia tetragonal parcialmente estabilizada por ítria

Objective: To evaluate the influence of different air abrasion protocols on the surface roughness of an yttria-stabilized polycrystalline tetragonal zirconia) (Y-TZP) ceramic, as well as the surface topography of the ceramic after the treatment. Method: Fifty-four specimens (7.5×4×7.5mm) obtained from two ceramic blocks (LAVA, 3M ESPE) were flattened with fine-grit sandpaper and subjected to sintering in the ceramic system's specific firing oven. Next, the specimens were embedded in acrylic resin and the surfaces to be treated were polished in a polishing machine using sandpapers of decreasing abrasion (600- to 1,200-grit) followed by felt discs with 10μm and 3μm polishing pastes and colloidal silica. The specimens were then randomly assigned to 9 groups, according to factors particle and pressure(n=6): Gr1- control; Gr2- Al 2O 3(50μm)/2.5 bar; Gr3- Al 2O 3(110μm)/2.5 bar; Gr4- SiO 2(30μm)/2.5 bar; Gr5- SiO 2(30μm)/2.5 bar; Gr6- Al 2O 3(50μm)/3.5 bar; Gr7- Al2O3(110μm)/3.5 bar; Gr8- SiO 2(30μm)/3.5 bar; Gr9- SiO 2(30μm)/3.5 bar. After treatments, surface roughness was analyzed by a digital optical profilometer and the morphology was examined by scanning electron microscopy (SEM). Data (μm) were subjected to statistical analysis by Dunnett's test (5%), two-way ANOVA and Tukey's test (5%). Results: The type of particle (p=0.0001) and the pressure (p=0.0001) used in the air abrasion protocols influenced the surface roughness values among the experimental groups (ANOVA). The mean surface roughness values (μm) obtained for the experimental groups (Gr2 to Gr9) were, respectively: 0.37 D; 0.56 BC; 0.46 BC; 0.48 CD; 0.59 BC; 0.82 A; 0.53B CD; 0.67 AB. The SEM analysis revealed that Al 2O 3, regardless of the particle size and pressure used, caused damage to the surface of the specimens, as it produced superficial damages on the ceramic, in the form of grooves and cracks. Conclusion: Al2O3 (110 μm/3.5 bar) air abrasion promoted the highest surface roughness on the ceramics, but it does not mean that this protocol promotes better ceramic-cement union compared to the other air abrasion protocols.

Produtividade e qualidade de grãos de canola em função da adubação nitrogenada e sulfatada

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)