Ultrasound assisted electrodeposition of Cu-SiO2 composite coatings: Effect of particle surface chemistry

Electrodeposition of Cu-SiO2 composite coatings from an alkaline non-cyanide electrolyte containing glutamate as complexing agent was studied. Silica mesoporous particles were synthesized using a modified Stöber methodology, and later their surface chemistry was changed by functionalizing them with 3-aminopropyltriethoxysilane. Particles microstructure and morphology were characterized (SEM, TEM, XRD) and their charging behavior in several electrolytes was studied through ζ-potential measurements. Galvanostatic deposition was performed in electrolytes containing both as-prepared and functionalized SiO2 at various current densities, and the influence of ultrasonic irradiation (37 Hz) was evaluated. For some experiments, 1.5 g L− of Polyquaternium 7 were added to the solution. SEM and XRD were used to characterized coatings morphology and microstructure, whereas EDS was used to estimate SiO2 wt%. The results showed that the effect of ultrasound on the codeposition process depends on current density and particle surface chemistry. All the trends observed in this study could be explained taking into account ζ-potential values recorded and previously reported theories. Adjusting the experimental conditions, it was possible to obtain deposits with SiO2 contents of ≈5 wt%. Finally, it was found that both ultrasonic irradiation and Polyquaternium 7 affect the morphology and crystal orientation of the deposits.Fil: Bengoa, Leandro Nicolás. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Tecnología de Pinturas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones en Tecnología de Pinturas; ArgentinaFil: Ispas, Adriana. Technische Universität Ilmenau; AlemaniaFil: Bengoa, Jose Fernando. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Tecnología de Pinturas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones en Tecnología de Pinturas; ArgentinaFil: Bund, A.. Technische Universität Ilmenau; AlemaniaFil: Egli, Walter Alfredo. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Tecnología de Pinturas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones en Tecnología de Pinturas; Argentin

Phosphorus as a promoter of a nickel catalyst to obtain 1-phenylethanol from chemoselective hydrogenation of acetophenone

Two catalysts were prepared using monodisperse pre-synthetized nanoparticles of metallic nickel and nickel phosphides with the same average diameter. Both nanoparticles species were deposited on the same support: mesoporous silica nano-spheres of MCM-41. This support is suitable to inhibit agglomeration and sintering processes during preparation steps. Therefore, two supported and activated catalysts with the same average nanoparticles diameter were obtained. They differ only in the nature of the active species: metallic nickel and nickel phosphides. The effect of the presence of a second element (phosphorus), more electronegative than nickel, on the activity and selectivity in the chemoselective hydrogenation of acetophenone was studied. The reaction conditions were: H2 pressure of 1 MPa, 80 °C using n-heptane as solvent. With the aim to understand the catalytic results, nanoparticles, support and catalysts were carefully characterized by X-ray diffraction, diffuse light scattering, transmission electron microcopy, high resolution transmission electron microcopy, selected area electron diffraction, scanning electron microcopy, Fourier transformer infrared spectroscopy, N2 adsorption at -196 °C, atomic absorption, H2 and CO chemisorption and volumetric oxidation. Considering these results and geometric and electronic characteristics of the surface of both active species, a change in the adsorption intermediate state of acetophenone in presence of phosphorus is proposed to explain the hydrogenation chemoselectivity of nickel phospides.Fil: Costa, Dolly Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Soldati, Analía Leticia. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; ArgentinaFil: Bengoa, Jose Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Marchetti, Sergio Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Vetere, Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; Argentin

ZSM-5 zeolite films on cordierite modules. Effect of dilution on the synthesis medium

Continuous, multilayered ZSM-5 zeolite films have been grown by direct synthesis on cordierite modules. The influence of the H2O/SiO2 ratio used in the synthesis mixture on the film properties was studied by inspecting the film formed in the external module surface at several water contents. It is shown that dilution prevents the film to become dense, modifies zeolite crystal morphology and reduces markedly the crystallization of zeolite into a non-adhered powder form. © 2002 Elsevier Science B.V. All rights reserved.Fil: Basaldella, Elena Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Kikot, Ana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Bengoa, Jose Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Tara, Juan Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; Argentin

Role of CeO2 in Rh/a-Al2O3 Catalysts for CO2 Reforming of Methane

The Rh/alpha-Al2O3 catalyst was modified by CeO2 in order to improve the thermal stability and the carbon deposition resistance during the CO2 reforming of methane, The carbon formation was determined by TPO, TEM and Raman spectroscopy. Characterization results showed that the incorporation of Ce in the support inhibits the carbon deposition, increasing the useful life and the stability of the Rh base catalysts.Fil: Ocsachoque, Marco Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Investigación y Desarrollo En Ciencias Aplicadas; ArgentinaFil: Bengoa, Jose Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; ArgentinaFil: Gazzoli, Delia. Universita Di Roma; ItaliaFil: Gonzalez, Maria Gloria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas; Argentin

Impact of the surface hydrophobicity/hydrophilicity ratio on the catalytic properties of Ni nanoparticles/MCM-41 system used in the hydrogenation of acetophenone

Three nickel catalysts were prepared supporting pre-synthetized monodisperse Ni nanoparticles of 16 nm. As support, nanospheres of MCM-41 were used. Two batches of these supports were superficially modified by silylation treatments with different functionalizing agents: methyltrimethoxysilane and hexamethyldisilazane. These procedures led to three catalysts whose only structural differences were the surface hydrophobicity degrees. These catalysts were tested in chemoselective hydrogenation of acetophenone and the conversion level was increased by effect of the silylation. Instead, selectivity to 1-phenylethanol, the product of interest, stayed at very similar and high values, about 95 %. The sequence of activity levels was explained considering local effects (steric and energetic) of the different functionalizing groups.Fil: Costa, Dolly Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Bengoa, Jose Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Marchetti, Sergio Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Vetere, Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; Argentin

Aminopropyl-modified mesoporous silica nanospheres for the adsorption of Cr(VI) from water

Aminopropyl-functionalized mesoporous silica spherical particles were obtained through post-synthetic route. The suitability of this material as an adsorbent for heavy metals from aqueous media was tested by Cr(VI) adsorption experiments performed at various pH conditions, chromium concentrations and time. The synthesized particles were characterized before and after functionalization by X-ray diffraction at low angles,nitrogen adsorption?desorption isotherms, infrared Fourier transform spectroscopy, scanning electron microscopy and thermogravimetric analysis. It was found that Cr(VI) adsorption occurs more efficiently in the pH range between 2 and 3. As a consequence of the nanometer scale of the particles, concentration profiles do not develop inside of them and thus there are no diffusional restrictions within the pores, leading to a higher Cr(VI) adsorption than that previously reported for similar systems. Chromium desorption for material reutilization was carried out in basic media. Results showed that the amino groups were grafted successfully without mesostructure damage. These groups are essential for the metal ion removal and no significant leaching was observed after fouruse/regeneration/use cycles. The batch equilibrium data fitted well the Langmuir isotherm with a maximum adsorption capacity of 87.1 mg/g at 25ºC. A discussion about the relationship between structure and its behavior as adsorbent, including regeneration and reusability, is given.Fil: Fellenz, Nicolás Antonio. Universidad Nacional de Rio Negro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte; ArgentinaFil: Martin, Pedro Pablo. Universidad Nacional de Rio Negro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte; ArgentinaFil: Marchetti, Sergio Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Bengoa, Jose Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas; Argentin

Changes in the surface hydrophobicity degree of a MCM-41 used as iron support: a pathway to improve the activity and the oleins production in the Fischer–Tropsch synthesis

The effect of surface hydrophobicity degree of MCM-41 support on activity and selectivity in Fischer?Tropsch synthesis has been studied. The Fe/MCM-41 catalyst was prepared by impregnation of the mesoporous support with iron. A portion of this product was silylated with hexamethyldisilazane. The samples were characterized by atomic absorption spectroscopy, X ray diffraction at low angles, N2 adsorption at 77 K, Fourier transform infrared spectroscopy and Mössbauer spectroscopy at 25 and 298 K in controlled atmosphere. Catalytic tests were performed simulating industrial operating conditions and showed that the silylated system presents higher activity, lower selectivity toward methane and higher olefin/paraffin ratio. The higher methane production and the lower amount of olefins observed for the non-silylated catalyst indicate that this system has a larger amount of hydrogen on its surface than the silylated one. A detailed discussion about the relationship among surface chemistry, stability, selectivity and the changes in iron species of the catalysts is presented.Fil: Fellenz, Nicolás Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bengoa, Jose Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas ; ArgentinaFil: Cagnoli, Maria Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas ; ArgentinaFil: Marchetti, Sergio Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas ; Argentin

Zinc and Chromium elimination from complex aqueous matrices using a unique aminopropyl-modified MCM-41 sorbent: Temperature, kinetics and selectivity studies

An aminopropyl-modified MCM-41 sorbent obtained by grafting amino groups on the surface of a previously synthesized MCM-41, was used for the removal of Cr(VI) and Zn(II) from different aqueous matrices: solutions of Zn(II) and Cr(VI) in distilled water, in distilled water with high-salt content, and in a natural river water sample. The sorbent particles are spherical with a mean diameter of ≈500nm, surface area >600m2g−1 and uniform aminopropyl function distribution. Single component adsorption batch experiments, fitted with the Langmuir model, show that MCM-41-NH2 has high removal capacity for Cr(VI) and for Zn(II), 87.5 and 58.9mgg−1, respectively. Binary component adsorption experiments show that the selectivity toward chromium oxyanions or zinc cations could be adjusted by changing the pH of the solution to be treated. When pH was fixed at acidic conditions chromium was preferentially removed, while the MCM-41-NH2 sorbent retained selectively zinc species when pH was increased up to 7. The presence of salts, either added (i.e. KCl) or natural as those present in river water, resulted in an improvement in the selectivity for both metals removal reaching values of up to 97%. The obtained results indicate that MCM-41-NH2 is an efficient and selective sorbent capable of removing Cr(VI) oxyanions and/or Zn(II) cations from complex polluted water matrices.Fil: Martin, Pedro Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Universidad Nacional de Río Negro; ArgentinaFil: Agosto, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Universidad Nacional de Río Negro; ArgentinaFil: Bengoa, Jose Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas ; ArgentinaFil: Fellenz, Nicolás Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Universidad Nacional de Río Negro; Argentin