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.

Síntese e caracterização de materiais mesoporosos para a captura de CO2: influência do óxido de níquel

Several materials are currently under study for the CO2 capture process, like the metal oxides and mixed metal oxides, zeolites, carbonaceous materials, metal-organic frameworks (MOF's) organosilica and modified silica surfaces. In this work, evaluated the adsorption capacity of CO2 in mesoporous materials of different structures, such as MCM-48 and SBA- 15 without impregnating and impregnated with nickel in the proportions 5 %, 10 % and 20 % (m/m), known as 5Ni-MCM-48, 10Ni-MCM-48, 20Ni-MCM-48 and 5Ni-SBA-15, 10NiSBA-15, 20Ni-SBA-15. The materials were characterized by means of X-ray diffraction (XRD), thermal analysis (TG and DTG), Fourier transform infrared spectroscopy (FT-IR), N2 adsorption and desorption (BET) and scanning electron microscopy (SEM) with EDS. The adsorption process was performed varying the pressure of 100 - 4000 kPa and keeping the temperature constant and equal to 298 K. At a pressure of 100 kPa, higher concentrations of adsorption occurred for the materials 5Ni-MCM-48 (0.795 mmol g-1 ) and SBA-15 (0.914 mmol g-1 ) is not impregnated, and at a pressure of 4000 kPa for MCM-48 materials (14.89 mmol g-1) and SBA-15 (9.97 mmol g-1) not impregnated. The results showed that the adsorption capacity varies positively with the specific area, however, has a direct dependency on the type and geometry of the porous structure of channels. The data were fitted using the Langmuir and Freundlich models and were evaluated thermodynamic parameters Gibbs free energy and entropy of the adsorption system