Obtenção de diesel verde por craqueamento termocatalítico de óleo de buriti (Mauritia flexuosa L.) sobre materiais nanoestruturados do tipo LaSBA-15

In order to obtain a biofuel similar to mineral diesel, lanthanum-incorporated SBA- 15 nanostructured materials, LaSBA-15(pH), with different Si/La molar ratios (75, 50, 25), were synthesized in a two-steps hydrothermal procedure, with pH-adjusting of the synthesis gel at 6, and were used like catalytic solids in the buriti oil thermal catalytic cracking. These solids were characterized by X-ray fluorescence (XRF), powder X-ray diffraction (XRD), thermogravimetric analysis (TG/DTG), infrared spectroscopy (FTIR), nitrogen porosimetry and ethanol dehydration, aiming to active sites identify. Taken together, the analyses indicated that the synthesis method has employed to obtain materials highly ordered mesostructures with large average pore sizes and high surface area, besides suggested that the lanthanum was incorporated in the SBA-15 both into the framework as well as within the mesopores. Catalytic dehydration of ethanol over the LaSBA-15(pH) products has shown that they have weak Lewis acid and basic functionalities, indicative of the presence of lanthanum oxide in these samples, especially on the La75SBA-15(pH) sample, which has presented the highest selectivity to ethylene. The buriti oil thermal and thermal catalytic cracking, realized from the room temperature to 450 ºC in a simple distillation system, has allowed obtaining two liquid fractions, each consisting of two phases, one aqueous and another organic, organic liquid (OL). The OL obtained from first fractions has shown high acid index, even in the thermal catalytic process. One the other hand, OL coming from second ones, called green diesel (GD), have presented low acid index, particularly that one obtained from the thermal catalytic process realized over LaSBA-15(pH) samples. The acid sites presence in these samples, associated to their large average pore sizes and high surface areas, have allowed them, especially the La75SBA-15(pH), to present deoxygenating activity in the buriti oil thermal catalytic cracking, providing an oxygenates content reduction, particularly carboxylic acids, in the GD. Furthermore, the GD comes from the second liquid fraction obtained in the buriti oil thermal catalytic cracking over this latest solid sample has shown hydrocarbons composition and physic-chemical properties similar to that mineral diesel, beyond sulfur content low

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.