Análise comparativa da eficácia mastigatória entre doentes portadores de PPR acrílica e esquelética

Dissertação para obtenção do grau de Mestre no Instituto Superior de Ciências da Saúde Egas Moniz

Estudos comparativos do ciclo de regeneração de diferentes tipos de silicoaluminofosfatos

Different types of heterogeneous catalysts of the silicoaluminophosphate type, (SAPO-5, SAPO-11, SAPO-31, SAPO-34 and SAPO-41), molecular sieves with a: AFI, AEL, ATO, CHA and AFO structure, respectively, were synthesized through the hydrothermal method. Using sources such as hydrated alumina (pseudobohemita), phosphoric acid, silica gel, water, as well as, different types of organic structural templates, such as: cetyltrimethylammonium bromide (CTMABr), di-isopropylamine (DIPA), di-n- propylamine (DNPA) and tetraethylammonium hydroxide (TEOS), for the respective samples. During the preparation of the silicoaluminophosphates, the crystallization process of the samples occurred at a temperature of approximately 200 ° C, ranging through periods of 18-72 h, when it was possible to obtain pure phases for the SAPOs. The materials were furthermore washed with deionized water, dried and calcined to remove the molecules of the templates. Subsequently the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), absorption spectroscopy in the infrared region (FT-IR), specific surface area and thermal analysis via TG/DTG. The acidic properties were determined using adsorption of n-butylamine followed by programmed termodessorption. These methods revealed that the SAPO samples showed a typically weak to moderate acidity. However, a small amount of strong acid sites was also detected. The deactivation of the catalysts was conducted by artificially coking the samples, followed by n-hexane cracking reactions in a fixed bed with a continuous flow micro-reactor coupled on line to a gas chromatograph. The main products obtained were: ethane, propane, isobutene, n-butane, n-pentane and isopentane. The Vyazovkin (model-free) kinetics method was used to determine the catalysts regeneration and removal of the coke

Variabilidade espacial do estoque de raízes finas em cultivo de palma de óleo em sistemas agroflorestais na Amazônia Oriental.

O objetivo do trabalho foi avaliar o estoque de raízes finas (<2mm) com uma variabilidade espacial e distribuídas horizontalmente em três cultivos de palma de óleo (Elaeis guineensis), sendo dois em sistemas agroflorestais (SAF?s) e em um cultivo convencional. O estudo foi realizado no município de Tomé-Açu (PA), em área de agricultor familiar. As amostras foram coletadas entre 0 e 10 cm através de um trado com as dimensões de anel de 10 cm de profundidade e com um diâmetro de 5 cm, em diferentes locais e distâncias da planta. Os locais foram: entre saf?s, entre plantas e entre o carreador, e as distâncias foram: 0,6; 1,2; 2 e 4m. Em seguida, foram lavadas com água corrente sobre peneiras de 2 e 1 mm, nessa ordem, para retirada de partículas de solo e separadas nas classes de diâmetro: ≤2,0; 2,1-5,0 e 5,1-10,0. Depois foram secas em estufa (65 ºC, 48 h) e pesadas. Grande parte da biomassa de raízes, foi encontrada na primeira distância da planta, nas outras distâncias houve um decréscimo na biomassa de raízes, evidenciando uma distribuição horizontal decrescente.

Reforma a seco de metano com catalisadores Ni/MCM-41 sintetizados a partir de fontes alternativas de sílica

The production of synthesis gas has received renewed attention due to demand for renewable energies to reduce the emissions of gases responsible for enhanced greenhouse effect. This work was carried out in order to synthesize, characterize and evaluate the implementation of nickel catalysts on MCM-41 in dry reforming reactions of methane. The mesoporous molecular sieves were synthesized using as silica sources the tetraethyl orthosilicate (TEOS) and residual glass powder (PV). The sieves were impregnated with 10% nickel to obtain the metallic catalysts (Ni/MCM-41). These materials were calcined and characterized by Thermogravimetric Analysis (TG), Infrared spectroscopy (FTIR), X-ray Diffraction (XRD), Temperature-Programmed Reduction (TPR) and N2 Adsorption/Desorption isotherms (BET/BJH). The catalytic properties of the samples were evaluated in methane dry reforming with CO2 in order to produce synthesis gas to be used in the petrochemical industry. The materials characterized showed hexagonal structure characteristic of mesoporous material MCM-41 type, being maintained after impregnation with nickel. The samples presented variations in the specific surface area, average volume and diameter of pores based on the type of interaction between the nickel and the mesoporous support. The result of the the catalytic tests showed conversions about 91% CO2, 86% CH4, yelds about 85% CO and 81% H2 to Ni/MCM-41_TEOS_C, and conversions about 87% CO2, 82% CH4, yelds about 70% CO and 59% H2 to Ni/MCM-41_PV_C. The similar performance confirms that the TEOS can be replaced by a less noble materials