Navegando por Assunto "Hidrotalcita"

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Acesso aberto (Open Access)
Síntese de hidróxidos duplos lamelares do sistema Cu, Zn, Al-CO3: propriedades morfológicas, estruturais e comportamento térmico
(2011-09) SANTOS, Sheila Silva dos; CORRÊA, José Augusto Martins
Hydrotalcite-like compounds are anionic clays, also known as layered double hydroxides (LDH), which have structure similar to brucite mineral. The LDHs of the system Cu, Zn, Al-CO3 were synthesized under conditions to promote the formation of small crystals with high surface area. The characterization was done by X-ray diffraction, thermogravimetric analysis, FTIR spectroscopy, and scanning electron microscopy. The synthesis were based on the co-precipitation method, under different conditions (hydrothermal bath, titration time) using copper and zinc sulfate, aluminum and sodium hydroxide solutions. The X-ray diffraction patterns show that synthesized compounds have high crystallinity, the peak intensities show that they are well organized and stacked with the lamellae. The infrared spectrum shows bands associated with carbonate anion in the interlayer region.
Acesso aberto (Open Access)
Síntese e caracterização do material hidrotalcita-hidroxiapatita e sua aplicação na reação de transesterificação do óleo de soja
(Universidade Federal do Pará, 2016-11-28) PEREIRA, Patricia Magalhães; CORRÊA, José Augusto Martins; http://lattes.cnpq.br/6527800269860568
The development of new materials with different properties (acid-base, composites, hybrids, among others) allied in a single product can present a relevant performance regarding the application in catalysis processes. The hydrotalcite characterized by high surface area and basic character, and hydroxyapatite because of its ion exchange capacity and amphoteric character, can be synthesized as the only material with catalytic potential for the transesterification reaction of soybean oil. This coexistence of phases in a Single material represents a new form of synthesis with the advantage of using an efficient route, low cost and with a decrease in the energy process. In this context, the general objective of this work is the synthesis of the HT-HAp material using the co-precipitation and homogenization method in ultrasonic bath (2h / 40 ° C), pH = 10, aging (24h), filtration and drying (24h/80 ° C). These materials were synthesized varying the molar ratio Mg / Al = 3, 1 and 0.33 and maintaining the Ca / P = 1.67 ratio. For comparison purposes the HT and HAp materials were synthesized and the material with a Mg / Al = 3 ratio was calcined at temperatures of 500 ° C and 900 ° C. The catalytic tests were performed under the following reaction conditions: Time (4h), Temperature (180 ° C), oil: alcohol ratio (1:12) and 2.5 % w/w material. The chemical physical characterization was performed by different analytical techniques: X-ray diffraction (XRD), Infrared Region Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), EDS chemical analysis, Thermal Analysis (TGA / DTA) and Superficial Analyses (BEHT / BHJ). The catalytic activity was analyzed by the Hammett (Qualitative and Quantitative) and Hydrogen Nuclear Magnetic Resonance (1H NMR) tests. The XRD spectrum showed the typical basal planes of the HT phase (003), (009), (110) and (113) of the phase HAp (002) (211) (300), (202), (213), (222), in the Mg / Al = 1 ratio and 0.33, there was the appearance of the manasseite, a hydrotalcite politype. The cell parameters and unit cell volume calculated were characteristic of the identified phases. The HT and HAp presented lamellar and granular morphology, and in the HTHAp materials, there is presence of both forms. The HT and HAp phases present in HTHAp materials presented cationic ratios of Mg / Al = 2 and Ca / P ~ 1.5, respectively. The FTIR spectrum recorded the characteristic bands of HT and HAp (OH-, CO3 2-, PO4 3- and H2O). The materials presented events of loss of endothermic mass, with appearance of peaks exotherm in the 0.33HTHAp material, dehydration, dehydroxylation and decarbonation events attributed. The materials presented a basic character in the pKBH range between 6.8 and 9.8. All materials showed the conversion of soybean oil into monoesters (biodiesel) and in the 1HTHAp material the best conversion rate (70%) was recorded.