Formação de micelas de cloreto de laurelcarnitina em soluções aquosas de etileno glicol

Dissertação (mestrado) - Universidade Federal de Santa Catarina. Centro de Ciencias Fisicas e Matematica

Amorphization Effects on the Basic Sites of Nanometric Magnesium Oxide

The paper reports the catalytic action of the basic sites of nanocrystalline particles of rare earth-doped magnesium oxide in the aldolization reaction between acetone and methanol leading to the C–C bond formation of an a,b-unsaturated compound (methyl vinyl ketone), also forming methyl ethyl ketone and isopropyl alcohol. Undoped and doped MgO samples were prepared by high-energy mechanical milling of commercial Mg, Y and Ce oxide powders. Catalytic activity and surface basicity of these compounds were strongly influenced by doping and the time of mechanical milling (amorphization process). Such milling leads to the formation of nanocrystalline materials. Influence of mechanical processing of these compounds was investigated by means of N2 adsorption (BET), X-ray diffraction (XRD), TEM, CO2 chemisorption and room temperature photoluminescence emission. Strong changes of polar groups such as hydroxyl groups on the surface of the solid were directly related to the photoluminescence emission observed

New use for succinylated sugarcane bagasse containing adsorbed Cu2+ and Ni2+ : efficient catalysts for gas-phase n-hexane and n-heptane oxidation reactions.

This study describes the use of succinylated twice-mercerized sugarcane bagasse containing adsorbed Cu2+ or Ni2+ ions from spiked aqueous solutions (2MSBA-Cu and 2MSBA-Ni) as heterogeneous catalysts for the catalytic oxidation of n-hexane and n-heptane in gas phase. To the best of our knowledge, this is the first study in which a spent adsorbent material based on lignocellulose biomass is used in the catalytic oxidation of volatile organic compounds. The adsorbent and spent adsorbent materials were characterized by FTIR, TGA and XRD. The amount of Cu2+ and Ni2+ adsorbed on 2MSBA was 0.49 and 2.49 mmol g?1, respectively. The catalysts were active for total oxidation of n-hexane and n-heptane, even at low temperatures. 2MSBA-Cu exhibited higher catalytic activity than 2MSBA-Ni and surprisingly their performances were comparable or superior to those of some catalysts reported in the literature, including noble metal-based catalysts

Effect of different synthesis methods on the textural properties of calcium tungstate (CaWO4 ) and Its catalytic properties in the toluene oxidation.

Calcium tungstate (CaWO4) crystals were prepared by microwave-assisted hydrothermal (MAH) and polymeric precursor methods (PPM). These crystals were structurally characterized by X-ray diffraction (XRD), N2 adsorption, X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) measurements. The morphology and size of these crystals were observed by field emission scanning electron microscopy (FE-SEM). Their optical properties were investigated by ultraviolet visible (UV-Vis) absorption and photoluminescence (PL) measurements. Moreover, these materials were employed as catalysts towards gas phase toluene oxidation reaction. XRD indicates the purity of materials for both preparation methods and MAH process produced crystalline powders synthesized at lower temperatures and shorter processing time compared to the ones prepared by PPM. FE-SEM images showed particles with rounded morphology and particles in clusters dumbbells-like shaped. PL spectra exhibit a broad band covering the visible electromagnetic spectrum in the range of 360 to 750 nm. XANES and EXAFS results show that preparation method does not introduce high disorders into the structure, however the H2-TPR results indicated that the catalyst reducibility is affected by the preparation method of the samples

Methane conversion to hydrogen and nanotubes on Pt/Ni catalysts supported over spinel MgAl2O4.

Methane decomposition is an endothermic process. Therefore a high temperature increases the methane conversion and improves the carbon accumulation. Nevertheless at high temperature conditions a faster deactivation of catalyst is generally observed. To keep the stability of the catalyst, lower reaction temperatures can be used as well as methane dilution but the catalytic activity is lowered. The aim of the present work consists in the study of the catalytic properties of Ni–Pt supported over MgAl2O4 for the selective conversion of methane into hydrogen and carbon nanotubes. The addition of a small amount of Pt to a nickel–MgAl2O4 catalyst promotes the formation of carbon nanotubes with a significant selectivity to MWCNT. The interest of using a bimetallic (Pt–Ni) catalyst is to favour the reduction of the Ni precursor (and the formation of small nickel particles). For the catalyst that we prepared methane is mainly transformed into structured MWCNTs if the reduction is complete while graphitization is observed over partially reduced catalysts. A fine characterization of the catalyst surface after each step of the preparation and use is currently under investigation in order to progress in the relationships between the surface composition and the CNTs formation

Use of Al2O3 in an automated on-line pre-concentration system for determination of cadmium(II) by FAAS.

This paper presents the development of an on-line pre-concentration system to determine cadmium(II) in aqueous samples. The analyte was trapped in a mini-column filled with Al2O3 in the form of macro-spheres obtained by the mixture of Al(NO3)3•9H2Oaq and chitosan dissolved in acetic acid. The mixture was dropped into an NH4OH aqueous solution under rigorous agitation using a peristaltic pump, the macro-spheres were separated from alkaline solution and dried, and finally were submitted to thermal treatment. The pre-concentration system was linear between 1.0 and 100 _gL−1, with a linearity of 0.999, sensitivity of 3.58×10−3 L_g−1 and enrichment factor of 21.9. The limits of detection and quantification were 0.08 _gL−1 and 0.28 _gL−1, respectively. The repeatability was between 2.6 and 5.9%. Recovery tests were carried out with a real aqueous sample

Preparation, characterization and catalytic properties of titanium oxide nanoparticles coated with aluminum oxide.

In the present study, TiO2 nanopowder was partially coated with Al2O3 precursors generated by a polymeric precursor method in aqueous solution. The system of nanocoated particles formed an ultra thin structure on the TiO2 nanoparticle surfaces, where the particle is the core and the nanocoating (additive) is the shell. The nanocoating process led to the obtainment of nanoparticles with important surface characteristics and catalytic behavior in the bioethanol dehydration reaction, with improved activity and particular selectivity in comparison to their non-coated analogs. Ethylene production was disfavored and selectivity toward acetaldehyde, hydrogen and ethane increased with increasing Al2O3 content in the catalysts. It is important to highlight that the TiO2–Al2O3 catalysts presented satisfactory values of selectivity toward hydrogen, in spite of the deactivation observed during the period of the test

Hydrogen production from ethanol steam reforming over Ni/CeO2 nanocomposite catalysts.

The organic polymer chitosan was used as the polymeric precursor for the synthesis of Ni/CeO2 nanocomposite catalysts. The materials were characterized by N2 physisorption, H2 chemisorption, AA, XRD, TGA, TPR, SEM and TEM analyses. The catalysts provide very good reactivity in ethanol steam reforming compared to the conventional Ni/CeO2 catalyst prepared by the impregnation method using a commercial support. High hydrogen selectivity (>75%) was obtained on Ni/CeO2 catalysts by operating at a temperature range of 325–500 C and a H2O/ C2H5OH molar ratio of 3. It was verified that the catalytic behavior could be influenced depending on the experimental conditions employed

Synthesis, characterization and catalytic properties of nanocrystaline Y2O3-coated TiO2 in the ethanol dehydration reaction

In the present study, TiO2 nanopowder was partially coated with Y2O3 precursors generated by a sol-gel modified route. The system of nanocoated particles formed an ultra thin structure on the TiO2 surfaces. The modified nanoparticles were characterized by high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD) analysis, Zeta potential and surface area through N2 fisisorption measurements. Bioethanol dehydration was used as a probe reaction to investigate the modifications on the nanoparticles surface. The process led to the obtainment of nanoparticles with important surface characteristics and catalytic behavior in the bioethanol dehydration reaction, with improved activity and particular selectivity in comparison to their non-coated analogs. The ethylene production was disfavored and selectivity toward acetaldehyde, hydrogen and ethane increased over modified nanoparticles.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq