Antimony (V) Oxide Adsorbed on a Silica-Zirconia Mixed Oxide Obtained by the Sol-Gel Processing Method: Preparation and Acid Properties

The preparation, degree of dispersion, thermal stability and Lewis and Brønsted acidity of antimony (V) oxide adsorbed on SiO2/ZrO2 mixed oxide, previously prepared by the sol-gel processing method, are described herein. The samples SiO2/ZrO2/Sb2O5, with compositions (in wt %): (a) Zr= 8.1 and Sb= 6.3; (b) Zr= 14.9 and Sb= 11.4, were prepared. Scanning electron microscopy images connected to a X-ray energy dispersive spectrometer showed that both metals, Zr and Sb, were highly dispersed in the matrices. The X-ray diffraction patterns of SiO2/ZrO2/Sb2O5 heated at different temperatures showed that, up to 1023 K, the matrix was amorphous. At 1273 K a crystalline phase of ZrO2 (baddeleyite) was observed and raising the temperature to 1573 K, crystalline phases of SiO2 (cristobalite) and presumably of ZrO2/Sb2O5 were observed. Using pyridine as a molecular probe, Brønsted acid sites on the SiO2/ZrO2/Sb2O5 matrix, heat treated up to 523 K, were shown to be very stable.A preparação, o grau de dispersão, estabilidade térmica e a acidez de Lewis e de Brønsted do óxido de antimônio (V) adsorvido sobre SiO2/ZrO2, preparado previamente pelo processo sol-gel, são descritas neste trabalho. Amostras de SiO2/ZrO2/Sb2O5 de composições (% em massa): (a) Zr= 8,1 e Sb= 6,3; (b) Zr= 11,4 e Sb= 11,4, foram preparadas. As imagens de microscopia eletrônica de varredura conectada a um espectrômetro de energia dispersiva de raios X mostraram que os metais, Zr e Sb, estão homogeneamente dispersos em ambas as matrizes. Os padrões de difração de raios X de SiO2/ZrO2/Sb2O5 aquecido a diversas temperaturas mostraram que até 1023 K a amostra apresentou-se amorfa. Em 1273 K a formação da fase cristalina ZrO2 (baddeleita) foi observada e elevando-se a temperatura a 1573 K, as fases cristalinas de SiO2 (cristobalita) e possivelmente de ZrO2/Sb2O5 foram observadas. Utilizando a piridina como sonda molecular, sítios ácidos de Brønsted do sólido SiO2/ZrO2/Sb2O5, aquecido até 523 K, mostraram ser bastante estáveis.611617Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Comparative Study of Catalytic Oxidation of Ethanol to Acetaldehyde Using Fe(III) Dispersed on Sb2O5 Grafted on SiO2 and on Untreated SiO2 Surfaces

Fe(III) was supported on Sb(V) oxide grafted on the silica gel surface and directly on the silica gel surface using ion-exchange and impregnation processes producing Fe/Sb/SiO2 and Fe/SiO2, respectively. The catalytic conversion of ethanol to acetaldehyde was much more efficient using Fe/Sb/SiO2 than Fe/SiO2 as catalyst. This higher efficiency of the former catalyst takes into account two aspects: a) the new phase FeSbO4 formed when Fe/Sb/SiO2 is heat treated and, b) it is higher dispersion on the matrix.O Fe(III) foi suportado sobre o óxido de Sb(V) enxertado na superfície de sílica gel e diretamente sobre a superfície da sílica gel, respectivamente por um processo de troca iônica e de impregnação. A conversão catalítica do etanol a acetaldeído foi muito mais eficiente usando Fe/Sb/SiO2 do que Fe/SiO2, como catalisador. Esta maior eficiência do primeiro em relação ao segundo, leva em conta dois aspectos: a) a nova fase FeSbO4 que se forma quando Fe/Sb/SiO2 é submetido ao aquecimento e, b) é mais dispersa na superfície da matriz.46947

Structure of cobalt (II) perchlorate adsorbed on silica gel surface chemically modified with benzimidazole molecule

Covalently attached benzimidazole molecules on silica gel surface, ≡SiL (where L = N-propyl-benzimidazole), adsorbs Co(ClO4)2 from non-aqueous solvent by forming a surface complex according to the reaction: m ≡SiL + Co(ClO4)2 → (≡SiL)mCo(ClO4)2. The equilibrium constant and the adsorption capacity, determined by applying the Langmuir equation were b = 3.0 × 103 L mol-1 and Ns= 0.098 × 10-3 mol g-1, respectively. The metal is bonded through the nitrogen atom and the perchlorate ion is not coordinated. The ESR study indicated that the complex has essentially an octahedral geometry with tetragonal distortion, with the electrons of the four nitrogen atoms interacting with the cobalt central metal ion in the equatorial plane. Only one complex species was detected on the surface

Al2o3 Coated With 3-n-propyl-1-azonia-4-azabicyclo[2. 2.2]octane Silsesquioxane Chloride And Its Use For Immobilization Of Cobalt(ii) Tetrasulfonated Phthalocyanine In Oxalic Acid Electrooxidation

A water-soluble polymer prepared by sol-gel process, 3-n-propyl-1-azonia-4- azabicyclo[2.2.2]octane silsesquioxane chloride, was adsorbed on alumina surface. This polymer-coated alumina was able to effectively immobilize cobalt(II) tetrasulfonated phthalocyanine complexes as counter ions. Cobalt phthalocyanine immobilized in this way is well and tightly adsorbed on Al 2O3/3-n-propyl-1-azonia-4-azabicyclo[2.2.2]octane silsesquioxane chloride surface. Furthermore, when incorporated to a carbon paste electrode showed a good electrocatalytic response toward the acid oxalic oxidation, making it a suitable electrode material. A linear relationship (r = 0.998) between the current responses obtained by chronoamperometric measurements and the oxalic acid concentration in the range of 7.4 × 10-5 - 9.1 × 10-4 mol L-1 was observed. A detection limit of 18 μmol L-1 was also determined. ©2008 Sociedade Brasileira de Química.194755761Templin, M., Franck, A., Du Chesne, A., Leist, H., Zhang, Y., Ulrich, R., Schädler, V., Wiesner, U., (1997) Science, 278, p. 1795Lee, K., Itharaju, R.R., Puleo, D.A., (2007) Acta Biomaterialia, 3, p. 515Yuan, J., Zhou, S., You, B., Wu, L., (2005) Chem. Mater, 17, p. 3587Fujiwara, M., Nishiyama, M., Yamamura, I., Ohtsuki, S., Nomura, R., (2004) Anal. Chem, 76, p. 2374Sayari, A., Hamoudi, S., (2001) Chem. Mater, 13, p. 3151Tien, P., Chau, L.K., Shieh, Y.Y., Lin, W.C., Wei, G.T., (2001) Chem. Mater, 13, p. 1124Gushikem, Y., Alfaya, R.V.S., Alfaya, A.A.S., (1998) Br PI, , 9.803.053-AArenas, L.T., Langaro, A., Gushikem, Y., (2003) J. Sol-Gel Sc. Tech, 28, p. 51Tundo, P., Venturello, P., Angeletti, E., (1982) J. Am. Chem. Soc, 104, p. 6547Wotring, V.J., Johnson, D.M., Bachas, L.G., (1990) Anal. Chem, 62, p. 1506Scindia, Y.M., Pandey, A.K., Reddy, A.V.R., (2005) J. Membr. Sci, 249, p. 143Arenas, L.T., Vaghetti, J.C.P., Moro, C.C., Lima, E.C., Benvenutti, E.V., Costa, T.M.H., (2004) Mater. Lett, 58, p. 895Kobayasbit, J., Anson, F.C., (1991) J. Phys. Chem, 95, p. 2595Ribeiro, E.S., Gushikem, Y., (1999) Electroanalysis, 11, p. 1280Lucho, A.M.S., Pissetti, F.L., Gushikem, Y., (2004) J. Sol-Gel Sc. Tech, 275, p. 251Arenas, L.T., Aguirre, T.A.S., Langaro, A., Gushikem, Y., Benvenutti, E.V., Costa, T.M.H., (2003) Polymer, 44, p. 5521Castellani, A.M., Gonçalves, J.E., Gushikem, Y., (2002) J. New Mat. Electrochem. Syst, 5, p. 169Arenas, L.T., Dias, S.L.P., Moro, C.C., Costa, T.M.H., Benvenutti, E.V., Lucho, A.M.S., Gushikem, Y., (2006) J. Colloid Interface Sci, 297, p. 244Min Jin, Z., Jiang Pan, Y., Feng Li, X., Lin Hu, M., Shen, L., (2003) J. Mol. Struct, 660, p. 67Marzocchi, M.P., Sbrana, G., Zerbi, G., (1965) J. Am. Chem. Soc, 87, p. 1429Fidalgo, A., Ilharco, L.M., (2004) Chem. Eur. J, 10, p. 392Ray, S., Vasudevan, S., (2003) Inorg. Chem, 42, p. 1711Tackley, D.R., Dent, G., Smith, W.E., (2001) Phys. Chem. Chem. Phys, 3, p. 1419Anson, F.C., (1966) Anal. Chem, 38, p. 54Xuan, G.S., Jang, S., Kwag, G., Kim, S., (2005) Bull. Korean Chem. Soc, 26, p. 671Lucho, A.M.S., Oliveira, E.C., Pastore, H.O., Gushikem, Y., (2004) J. Electroanal. Chem, 73, p. 55Bard, A.J., Faulkner, L.R., (2001) Electrochemical Methods. Fundamentals and Applications, , 2nd ed, Wiley: New York, ch. 9Yamazaki, S., Yamada, Y., Fujiwara, N., Ioroi, T., Siroma, Z., Senoh, H., Yasuda, K., (2007) J. Electroanal. Chem, 602, p. 96Casella, I.G., (1999) Electrochim. Acta, 44, p. 3353Mandanas, M.M., Shaffer, W., Adair, J.H., (2002) J. Am. Ceram. Soc, 85, p. 2156Shaidarova, L.G., Chelnokova, I.A., Gedmina, A.V., Budnikov, G.K., Ziganshina, S.A., Mozhanova, A.A., Bukharaev, A.A., (2006) J. Anal. Chem, 61, p. 37

Synthesis and characterization Of SiO2-Nb2O5 systems prepared by the sol-gel method: structural stability studies

X-Ray diffraction (XRD), N-2 absorption (BET specific surface area), transmission electron microscopy (TEM), Raman and Fourier infrared (FT-IR) spectroscopic techniques have been applied to characterize the texture, structure and niobia-silica interaction of SiO2-Nb2O5 systems prepared by the sol-gel method containing different amounts of Nb2O5 and calcined at temperatures between 393 and 1473 K. For a small loading of niobia, amorphous niobium species were well dispersed in the silica LIP to 1273 K. Crystallization is observed only after thermal treatment at 1473 K, with the T-phase predominating as observed by XRD and TEM analyses and confirmed by Raman spectra. For samples with a higher amount of niobia. the formation of a T-Nb2O5 phase was observed at 1273 K, and the H-Nb2O5 phase predominates at 1473 K. FT-IR results indicate the presence of Si-O-Nb linkages at the silica-niobia interface, formed during preparation, which are responsible for the higher structural stability of the SiO2-Nb2O5 system. The stability of the SiO2-Nb2O5 system is confirmed by obtaining high specific surface areas even after the high temperature of calcination.1282552255

Adsorption of hidrogen peroxide on the surface of silica - titania mixed oxide obtained by the sol-gel processing method

This work describes the sol-gel mixed oxide SiO2/TiO2 property, ST, as prepared, and submitted to heat treatment a 773 K, STC. SEM and EDS images show, within magnification used, a uniform distribution of the TiO2 particles in SiO2/TiO2 matrix. Both, ST and STC adsorb hydrogen peroxide on the surface and through EPR and UV-Vis diffuse reflectance spectra, it was possible to conclude that the species on the surface is the peroxide molecule attached to the Lewis acid site of titanium particle surface, alphaTi(H2O2)+. As the material is very porous, presumably the hydrogen peroxide molecule is confined in the matrix pores on the surface, a reason why the adsorbed species presents an exceptional long lived stability.4145Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

X-ray Photoelectron Spectroscopy And Mossbauer Spectroscopy Study Of Iron(iii) And Antimony(v) Oxides Grafted Onto A Silica Gel Surface

[No abstract available]191325132

Nitrogen Containing Organosilicon Bonded an Al2O3-Cellulose Acetate Hybrid Material: Preparation, Characterization and Use for Adsorption of Fe(III), Cu(II) and Zn(II) from Ethanol Solutions

This work describes the preparation and characterization of a cellulose acetate fiber coated with Al2O3, resulting in the organic-inorganic hybrid Cella/Al2O3. Furthermore, it was modified by attaching organofunctional groups, by reaction with the precursor reagents (RO)3Si(CH2)3L (L = -NH2, NH(CH2)2NH2, NH(CH2)2NH(CH2) 2NH2 and NC3H3N), resulting in Cella/Al2O3/Si(CH2 )3NH2 (1), Cella/Al2O3/Si(CH2 )3NH(CH2)2NH2 (2), Cella/Al2O3/Si(CH 2)3NH(CH2)2 NH(CH2)2NH2 (3) and Cella/Al2O3/Si(CH2 )3NC3H3N (imidazole) (4). The amount of attached organofunctional groups were (in mmol per gram of the material): 1 = 1.90, 2 = 1.89, 3 = 1.66 and 4 = 1.35. The adsorption isotherms from ethanol solutions of FeCl3, CuCl2 and ZnCl2 by Cella/Al2O3/Si(CH2 )3L were obtained at 298 K. The results obtained in flow experiments showed a retention and recovery of ca. 100% of the metal ions by Cella/Al2O3/Si(CH2 )3L packed in a column, for a solution containing either one or mixture of the ions.Este trabalho descreve a preparação e a caracterização da fibra acetato de celulose recoberta com Al2O3, resultando no híbrido orgânico-inorgânico Cella/Al2O3. Posteriormente, este híbrido foi modificado, imobilizando-se grupos organofuncionais, através da reação com o precursor (RO)3Si(CH2)3L (L = -NH2, -NH(CH2)2NH2, -NH(CH2)2NH(CH2) 2NH2 e -NC3H3N), o que resultou nos materiais Cella/Al2O3/Si(CH2 )3NH2 (1), Cella/Al2O3/Si(CH2 )3NH(CH2)2NH2 (2), Cella/Al2O3/Si(CH2 )3NH(CH2)2NH(CH 2)2NH2 (3) e Cella/Al2O3/Si(CH2 )3NC3H3N (imidazol) (4). A quantidade de grupos organofuncionais ligados foram (em mmol por grama de material): 1 = 1,90, 2 = 1,89, 3 = 1,66 e 4 = 1,35. As isotermas de adsorção das soluções etanólicas de FeCl3, CuCl2 e ZnCl2 por Cella/Al2O3/Si(CH2 )3L foram obtidas à 298 K. Os resultados obtidos pela análise em fluxo mostraram uma retenção e recuperação de praticamente 100% dos íons metálicos na coluna empacotada com Cella/Al2O3/Si(CH2 )3L, para uma solução contendo apenas um ion ou uma mistura de íons.8894Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Cobalt(II) phthalocyanine bonded to 3-n-propylimidazole immobilized on silica gel surface: preparation and electrochemical properties

Co-Phthalocyanine complex was immobilized on 3-n-propylimidazole groups grafted on a porous SiO2 surface (specific surface area S BET = 500 m² g-1) and efficiently electrocatalyzed the oxalic acid oxidation on a carbon paste electrode surface made of this material. Intermolecular interactions of the complex species which can normally interfere in the redox process practically are not observed in the present case because of a low average surface density, delta = 4.7 x 10-13 mol cm-2 (delta = Nf/S BET, where Nf is the amount of adsorbed Co-phtalocyanine per gram of modified silica gel) of the complex species material prepared. The linear response of the electrode to oxalic acid concentration, between 6.5 x 10-4 and 3.2 x 10-3 mol L-1, associated with its high chemical stability makes the covalently immobilized Co-phtalocyanine complex material very attractive in preparing a new class of chemical sensors.A ftalocianina de cobalto(II) imobilizada sobre a sílica gel (área superficial S BET = 500 m² g-1) modificada com 3-n-propilimidazol, foi incorporada a um eletrodo de pasta de carbono e mostrou-se eficiente na eletrocatálise da oxidação do ácido oxálico. As interações intermoleculares do complexo, as quais podem normalmente interferir no processo redox, praticamente não foram observadas no presente caso, devido a baixa densidade média do complexo na superfície do material sintetizado delta = 4,7 x 10-13 mol cm-2 (delta= Nf/S BET, onde Nf é a quantidade de Co-Ftalocianina adsorvida por grama de silica gel modificada ). A resposta linear do eletrodo para concentrações do ácido oxálico entre 6,5 x 10-4 e 3,2 x 10-3 mol L-1, associado com sua alta estabilidade química tornam o material com a ftalocianina de cobalto(II) ligado covalentemente muito atrativo na preparação de uma nova classe de sensores químicos.389393Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq