Influence of copper on nickel-based catalysts in the conversion of glycerol

The catalytic transformation of glycerol to value-added compounds was investigated over bimetallic Ni-Cu/gamma-Al2O3 catalysts with Ni/Cu atomic ratios of 8/1, 4/1, 2/1, 1/1, 1/2, 1/4, and 1/8. XPS analysis revealed that the surface composition of the catalyst exhibited progressive enrichment of Cu as its content in the catalyst increased. H-2-chemisorption indicated that the total number of exposed Ni atoms decreased as the Cu content increased. As a result, deep hydrogenolysis to produce CH4 was inhibited by the addition of Cu to the Ni catalyst, yielding higher selectivity toward the dehydration products of glycerol such as hydroxyacetone.; FTIR spectra of adsorbed CO reveal that Cu asserts both geometric and electronic effects on the adsorption properties of Ni. The geometrical effect is visualized by the progressive disappearance of the bridge bound adsorbed CO on metallic Ni by the incorporation of Cu. This suggests that the deep hydrogenolysis of glycerol to CH4 formation requires an ensemble of adjacent active Ni atoms. The electronic effect of Cu on Ni is indicated by the red shift of the IR peak of adsorbed CO as the Cu content increases. The electronic interaction between Cu and Ni species was also substantiated by XANES results. HTREM revealed metal particles very well distributed on the support with particle size of 1.5 to 5 nm. The Ni Cu samples were not a total intermetallic alloys. (C) 2014 Elsevier B.V. All rights reserved.Postprint (published version

Water-soluble gold nanoparticles : from catalytic selective nitroarene reduction in water to refractive index sensing

Water-soluble gold nanoparticles (Au NPs) stabilized by a nitrogen-rich PEG-tagged substrate have been prepared by reduction of HAuCl₄ with NaBH₄ in water at room temperature. The morphology and size of the nanoparticles can be controlled by simply varying the gold/stabilizer ratio. The nanoparticles have been fully characterized by TEM, HRTEM, ED, EDS, UV-vis, p-XRD and elemental analysis. The material is efficient as a recyclable catalyst for the selective reduction of nitroarenes with NaBH₄ to yield the corresponding anilines in water at room temperature. Furthermore, the potential ability of the Au NPs as a refractive index sensor due to their localized surface plasmon resonance (LSPR) effect has also been assessed

A autoavaliaçao na aprendizagem de língua inglesa: subsídio para reconhecimento da própria aprendizagem e gestao do erro

Resumo: Os documentos oficiais para o ensino de língua estrangeira, na educação básica, apresentam a necessidade de oferecer subsídios para que o indivíduo se posicione criticamente no contexto no qual está inserido e estabeleça diálogo com outras realidades. Como a aprendizagem de uma língua demanda estudo constante, até mesmo após o período escolar – quando não há mais a figura do professor como mediador –, o desenvolvimento de maior autonomia para com o aprender se faz relevante. Uma das opções, revelada pela literatura como desencadeadora de maior independência cognitiva, é a utilização da autoavaliação. Este estudo é um recorte de uma dissertação de mestrado em andamento, e tem por objetivo expor a análise da efetividade da autoavaliação no reconhecimento da situação na qual se encontra a aprendizagem e do tratamento do erro como possibilidade para aprender. A pesquisa, de abordagem qualitativa, na modalidade estudo de caso, teve a participação de 36 alunos da 8ª série de uma escola pública da região Norte do Paraná. As informações dos instrumentos de coleta foram submetidas à análise de conteúdo temática, permitindo constatar que a maioria dos alunos, após trabalho com a autoavaliação, mostrou ser capaz de reconhecer seus pontos fortes e suas dificuldades e considerou o erro como alavanca para mudanças na aprendizagem, revelando o potencial deste instrumento para desencadear reflexão sobre a situação de aprendizagem. Palavras-chave: Aprendizagem de língua inglesa. Autoavaliação. Regulação da aprendizagem. Autonomia. Abordagem do erro

Hydrogenolysis Of Methylcyclopentane Over The Bimetallic Ir-au/γ-al2o3 Catalysts

The gas-phase hydrogenolysis of methylcyclopentane (MCP) was investigated over the bimetallic Ir-Au/γ-Al2O3 catalysts. The bimetallic systems containing the atomic Au/Ir ratios in the range of 0.125-8 and a fixed total metal content of 8 wt.%, were prepared by the sequential impregnation (SI) and co-impregnation (CI) methods. The corresponding monometallic Ir/γ-Al2O3 and Au/γ-Al2O3 catalysts were also prepared. The materials were characterized by ICP, XRD, N2 adsorption, TEM, and H2 chemisorption. Highly dispersed Ir nanoparticles were obtained in all cases, while the size of Au nanoparticles increased (up to 50 nm) upon the increasing Au content in the catalyst. The monometallic gold catalyst did not adsorb H2. The incorporation of Au increased the amount of irreversible adsorbed H2 in the Ir-Au/γ-Al2O3 catalysts with respect to the monometallic ones. The products obtained in the MCP hydrogenolysis were 2-methylpentane (2-MP), 3-methylpentane (3-MP) and n-hexane (n-H). The initial rate (molecules of MCP reacted s-1 gIr -1) increased with the Au content. The deactivation was lower for bimetallic catalysts, particularly for the CI ones. The addition of Au played a significant effect on chemisorption and catalytic properties of Ir. © 2007 Elsevier B.V. All rights reserved.25313 SPEC. ISS.58885893Boudart, M., (1969) Adv. Catal., 20, p. 153Leclercq, G., Leclercq, L., Maurel, R., (1977) J. Catal., 50, p. 87Dartigues, J.M., Chambellan, A., Gault, F.G., (1976) J. Am. Chem. Soc., 98, p. 856Sinfelt, J.H., (1983) Bimetallic catalysts. Discoveries, Concepts and Applications, , John Wiley & Sons, New YorkPaál, Z., Tétényi, P., (1977) Nature, 267, p. 234Gault, F.G., (1980) Adv. Catal., 30, p. 1Ciapetta, F.G., Wallace, D.N., (1971) Catal. Rev., 5 (1), p. 67Mills, G.A., Heinemann, H., Milliken, T.H., (1953) Ind. Eng. Chem., 45, p. 134Anderson, J.B.F., Burch, R., Cairns, J.A., (1987) J. Catal., 107, p. 351Corolleur, C., Corolleur, S.R., Gault, F.G., (1972) J. Catal., 24, p. 385Juszczyk, W., Karpinski, Z., (2001) Appl. Catal., 206, p. 67Clarke, J.K.A., Kane, A.F., Baird, T., (1980) J. Catal., 64, p. 200Huang, Y.J., Fung, S.C., Gates, W.E., Mcvicker, G.B., (1998) J. Catal., 118, p. 192Balakkrishnan, K., Schwank, J., (1979) J. Catal., 132, p. 458Lam, Y.L., Boudart, M., (1977) J. Catal., 50, p. 530Foger, K.E., Anderson, J.R., (1980) J. Catal., 64, p. 448Barron, Y., Maire, G., Muller, J.M., Gault, F.G., (1966) J. Catal., 5, p. 428Somorjai, G.A., (1977) Adv. Catal., 26, p. 1Guil, J.M., Masía, A.P., Panigo, R.A., Menayo, J.M.T., (1998) Thermochim. Acta, 312, p. 115Hansen, M., (1958) Constitution of Binary Alloys, , McGraw-Hill, New YorkSomorjai, G., (1980) Chemistry in Two Dimensions, , Cornell University Press, CornellKramer, R.E., Zuegg, H., (1984) J. Catal., 85, p. 530Sinfelt, J.H., (1975) Prog. Solid State Chem., 10, p. 5

On the role of ultrasound and mechanical stirring for iodide adsorption by calcined layered double hydroxides.

10.1016/j.clay.2014.02.012Improving the adsorption of long-term radioactive species in the underground disposal of waste waters from nuclear reactors is a key issue. The natural metal oxides or hydroxides underground have the low retention ability of anionic species. Here, calcined Mg/Al LDHs were used as adsorbents. The influence on the adsorption capacity of different intercalated guest anions (carbonate (CO32 -) and nitrate (NO3-)) in the parent LDH was investigated, along with the effect of ultrasonication. Two Mg/Al molar ratios (3/1 and 2/1) were compared. Adsorption capacity was strongly affected by material textural properties, and the carbonate LDH-derived mixed oxides showed the largest adsorption capacity. Mixed oxides with an Mg/Al molar ratio equal to 3 presented higher iodide adsorption due to their lower charge density. The adsorption assisted by ultrasound increased iodide removal efficiency by reducing internal diffusion limitation. Two models were used to determine adsorption capacity: Langmuir and Freundlich. The iodide adsorption was best fitted by the Langmuir equilibrium model

Resolution and metallurgical studies with a scanning electron acoustic microscope

SIGLELD:9091.9F(AERE-R--10473) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Cobalt hydrotalcites as catalysts for bioethanol steam reforming. The promoting effect of potassium on catalyst activity and long-term stability

Cobalt hydrotalcite-derived catalysts, doped with potassium, are active materials for the ethanol steam reforming reaction. Potassium addition reduces the acid sites number and strength. It acts as a promoter of the ethanol steam reforming (ESR); ethanol conversion is higher at lower temperature, as the amount of potassium at the surface of the catalyst increases. The catalysts are stable for long-term experiments (300 h) under high loads of ethanol and bioethanol (0.036 gEtOH min−1, H2O:CH3CH2OH = 4:1 molar). Moreover, they generate a low amount of carbon (0.0067 gC gcatalyst−1 h−1). The catalysts after reaction contain almost exclusively high spin Co2+ in cobalt oxide (or in (Co,Mg)O); only traces of metallic cobalt are identified by magnetometry, <0.1 wt.% Co0, suggesting that oxidized cobalt is an active species in ESR

Oxidation of Ethanol to Acetaldehyde over Na-promoted vanadium oxide catalysts

Sodium-promoted vanadium oxide catalysts supported on MCM-41 and TiO2 (anatase) were investigated for the partial oxidation of ethanol to acetaldehyde. The catalysts were prepared by incipient wetness impregnation with a vanadium oxide content of 6 wt.%. The experimental characterization was performed by X-ray diffraction (XRD), N-2 adsorption, temperature-programmed reduction (TPR), and diffuse reflectance UV-vis. Temperature-programmed oxidation (TPO) was also used to identify carbon deposits on the spent catalysts. The presence of sodium plays a strong role in the dispersion and reducibility of the vanadium species as detected by TPR analysis and optical absorption spectroscopy. While sodium addition increases the dispersion of the VOx species, its presence also decreases their reducibility. Additionally, TPO of the spent catalysts revealed that an increase in the Na loading decreases the carbon deposition during reaction. In the case of the catalysts supported on MCM-41, these modifications were mirrored by a change in the activity and selectivity to acetaldehyde. Additionally, on the VOx/TiO2 catalysts the catalytic activity decreased with increasing sodium content in the catalyst. A model in which sodium affects dispersion, reducibility and also acidity of the supported-vanadia species is proposed to explain all these observations.close1