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ABSTRACT: A family of anionic iron(III) porphyrins (FePor) was immobilized onto zinc oxide (ZnO) obtained by the in situ hydrothermal decomposition of zinc hydroxide nitrate, a layered hydroxide salt. The immobilization probably occurred via the interaction between the anionic charges on the porphyrins and the positively charged surface of the ZnO, in slightly acidic to neutral pH. The resulting solids were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRDP), Fourier transform infrared spectroscopy (FTIR), electron paramagnetic resonance (EPR), and ultraviolet-visible spectroscopy (UV-Vis) (solid samples), which confirmed the formation of ZnO and the immobilization of the FePor. The prepared materials were employed as catalysts for the heterogeneous catalytic oxidation of cyclooctene, cyclohexane, and n-heptane, using iodosylbenzene as the oxygen donor. Good catalytic results were achieved for all the substrates, and selectivity for the alcohol was verified during the oxidation of alkanes. The reuse capacity of the solid catalyst was also investigated.
Journal of Colloid and Interface Science 04/2012; 377(1):379-86. · 3.07 Impact Factor
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ABSTRACT: Raw kaolinite was modified with triethanolamine (TEA), in an attempt to create a new support for the immobilization of metalloporphyrins. Anionic metalloporphyrins containing Fe(3+) or Mn(3+) as metallic centers were immobilized on the prepared support, and the obtained solids were characterized by Fourier-transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRPD), thermal analysis (thermogravimetric and differential thermal analyses--TGA/DTA), and scanning electron microscopy (SEM). The solids were used in heterogeneous oxidation catalysis of cyclooctene and cyclohexane. The yields from the oxidation of cyclooctene depended on the amount of TEA and/or water present in the solids. Good reaction yields were obtained for the oxidation of cyclohexane, with selectivity for the alcohol. In one specific case, a possible co-catalytic activity was verified for TEA during the oxidation of cyclohexane.
Journal of Colloid and Interface Science 02/2012; 374(1):278-86. · 3.07 Impact Factor
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ABSTRACT: The development of alternative methods of biodiesel production still remains a major priority of the biofuel industry. In this work, the catalytic activity of anhydrous and insoluble sodium tungstate (Na2WO4) and its heterogenized form in silica (Na2WO4/SiO2) in soybean oil methanolysis was studied. The sol–gel process was conducted by both the acid and basic routes, and it was observed that the obtained solid catalysts Na2WO4/SiO2 presented different characteristics depending on the conditions employed during their synthesis. The solid catalysts afforded high methyl esters yields (above 95%) in one single reaction step, and they were amenable to recovery and recycling for at least four consecutive reaction cycles, during which high catalytic activity was maintained. Recovery and recycling were carried out by simple solid catalyst filtration and washing. In general, all the investigated silica-based solids were catalytically active for soybean oil transesterification; however, there was a decrease in the catalytic yield after each recycling process. The catalytic activity of the heterogenized silica solids was influenced by various physical parameters, such as specific surface area and textural properties. The structure of the solid catalysts and their catalytic behavior was also evaluated by X-ray fluorescence (XRF), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and textural analyses.
06/2011;
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ABSTRACT: Nanofibrous and nanotubular materials, natural and synthetic, are important alternative matrices for the immobilization of metallocomplexes, especially metalloporphyrins, as oxidation catalysts. The process permits a regular and controllable distribution of the active phase at the outer and/or inner surfaces of the tubes, promoting a special environment for the approximation of a substrate to the catalytic active species. The immobilization also prevents the molecular aggregation and bimolecular self-destruction reactions, facilitates the recovery and reuse of the catalyst, reduce de cost of material preparation and environmental concerns. A variety of nanofibrous and nanotubular structures are presented and specific examples of immobilization of iron porphyrins in different supports and their oxidation catalytic activities are presented and discussed.
Journal of Colloid and Interface Science 12/2007; 315(1):142-57. · 3.07 Impact Factor
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ABSTRACT: Metalloporphyrins are exceedingly useful building blocks for the design and synthesis of molecularly based solids. The use of hydrogen bonding or metal ion coordination provides a wide range of framework solids. Using various polyfunctionalized porphyrins, we have created porous solids that are thermally robust and that retain their internal porosity upon loss of solvates. Their pore dimensions are comparable to zeolites, and they show shape and size selectivity in sorption of guest molecules and in epoxidation of alkenes.
Accounts of Chemical Research 05/2005; 38(4):283-91. · 21.64 Impact Factor
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ABSTRACT: Mg-Al layered double hydroxide (LDH) intercalated with glycinate anions was synthesized through co-precipitation and exfoliated in formamide and the single-layer suspension was reacted with aqueous iron porphyrin solutions (Fe(TDFSPP) and Fe(TCFSPP)). The obtained materials were characterized by X-ray powder diffraction, UV-vis, and electron paramagnetic resonance and investigated in the oxidation reaction of cyclooctene and cyclohexane using iodosylbenzene as oxidant. The iron porphyrin seems to be immobilized at the surface of the glycinate intercalated LDH. The catalytic activities obtained in heterogeneous media for iron porphyrin, Fe(TDFSPP), was superior to the results obtained under homogeneous conditions, but the opposite effect was observed on the Fe(TCFSPP), indicating that, instead of the structural similarity of both iron porphyrins (second-generation porphyrins), the immobilization of each one produced different catalysts. The best catalytic activity of the Fe(TDFSPP)/Gly-LDH, compared to Fe(TCFSPP)/Gly-LDH, can be explained by the easy access of the oxidant and the substrate to the catalytic sites in the former, probably located at the surface of the layered double hydroxide pillared with glycinate anions. A model for the immobilization and a mechanism for the oxidation reaction will be discussed.
Journal of Colloid and Interface Science 02/2005; 281(2):417-23. · 3.07 Impact Factor
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ABSTRACT: The use of nonporphyrin complexes encapsulated in zeolites as catalysts for oxidation reactions has been improved in the past decades by the discovery of increasing numbers of nonheme monoxygenases. The zeolite lattice can change the oxidative chemistry of the metallocomplexes, resulting in a catalytic effect different from those observed in homogeneous reactions. We report the encapsulation of iron and copper metallocomplexes with the ligand (2-hydroxybenzyl)(2-methylpyridyl)amine, Hbpa, and iron complexes with the ligand N,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-methylpyridyl) ethylenediamine, H(2)bbpen. The zeolite-encapsulated metallocomplexes were prepared by diffusion of the ligands through the pores of the zeolites, already exchanged with the respective metal. The syntheses were performed in methanol and toluene solutions. Elemental analysis of solids with the Hbpa ligand have indicated better complexation for synthesis in toluene, where 74% of the iron atoms were coordinated by the ligand, against 37% for the synthesis in methanol. For the immobilization with the H(2)bbpen ligand in toluene it was observed that 46% of the iron atoms are coordinated, showing that the diffusion of the small ligand Hbpa through the zeolite cage was facilitated. The EPR spectra of the solids show signals at g = 2.0, which was attributed to an Fe-Fe interaction from the noncoordinated atoms, and g = 4.3 attributed to iron (III) in a rhombic geometry.
Journal of Colloid and Interface Science 10/2004; 277(1):138-45. · 3.07 Impact Factor
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ABSTRACT: The first immobilization of Ni(II) and Mn(III) metallotetraazaannulene compounds in nanometric pores of an inorganic matrix (porous Vycor glass,PVG) by diffusion of the complex through the glass pores is reported. The immobilization processwas monitored by UV–vis spectroscopy at room temperature and electron paramagnetic resonance spectroscopy (EPR) at 77 and 300 K. Results showed that the manganese(III)complex was reduced inside the PVG after the immobilization process. On the other hand, the NiTMTAA (tetramethyl dibenzotetraaza[14]annulene of nickel(II)) remained stable. The catalytic activity of NiTMTAA as model of Factor F430 on the reductive dehalogenation of alkyl halides (iodocyclohexane or bromocyclohexane) was studied in homogeneous and heterogeneous systems in the presence of NaBH4 as reducing agent. The promising catalytic results have shown adequate characteristics of PVG for immobilization of the Ni(II) tetraazaannulene complex. These nanocomposites display high potential for heterogeneous catalytic procedures.
Journal of Molecular Catalysis A Chemical 01/2004; 222:213-222. · 2.95 Impact Factor
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ABSTRACT: Understanding the interaction of metal ions with melanin structures is essential to know some intricate functions of this kind of compounds in the living systems. The coordination chemistry of vanadyl oxycation, VO(II), and copper, Cu(II), in a synthetic l-dopa melanin (SM) was investigated using electron paramagnetic resonance (EPR), Fourier transform infrared (FT IR) and ultraviolet–visible (UV–Vis) spectroscopy. The EPR and FT IR spectra indicated axially coordinated VO(II) ions bound to catecholate functional groups, and a fraction of the Cu(II) ions in a square planar structure partially coordinated to carboxylate functional groups. The resolved EPR perpendicular super hyperfine splitting constant, AN⊥, and the Cu(II) complex EPR parallel parameters g‖ and A‖ values indicated two magnetically equivalent nitrogen atoms in a plane with the coordination sphere, CuN2O2. The ultraviolet–visible (UV–Vis) spectra of solid samples indicate supramolecular structure constitution for the synthesized VO(II)SM and Cu(II)SM complexes.
Inorganica Chimica Acta 01/2003; 356:243-248. · 1.85 Impact Factor
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ABSTRACT: Two samples of montmorillonite (one of Brazilian origin, BNC1 clay, and the other STX-1, supplied by the Clay Mineral Society Repository (University of Missouri, USA) were allowed to react with biomimetic metalloporphyrins of Fe(III) and Mn(III) in cationic form. The compounds were characterized by several techniques, showing that the metalloporphyrins molecules were adsorbed at the surface of the clay platelet crystals. The catalytic activities of the intercalated complexes for the oxidation of alkane were dependent upon the concentration of the porphyrin immobilized in the clay and factors such as the metal ion species in the porphyrins, choice of solvent, and concentration of the iodosylbenzene oxidant. Good selectivity to cyclohexanol instead of cyclohexanone was observed for the catalytic oxidation of cyclohexane by iodosylbenzene.
Journal of Colloid and Interface Science 11/2002; 254(1):158-64. · 3.07 Impact Factor
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ABSTRACT: In this paper we report the immobilization and characterization of neutral and pentacationic iron porphyrins into the nanometric pores of an inorganic matrix (porous vycor glass, PVG) and the use of these materials as catalyst in mimetic– enzymatic processes. The concentration of iron porphyrin in the large glass pores depends on the conditions present during the incorporation process. The materials obtained were used as catalyst in the oxidation reaction of cyclohexane and cyclohexene by iodosylbenzene. The catalytic results were promising, evidencing adequate characteristics of PVG for immobilization of iron porphyrin and strong potential of these nanocomposites for heterogeneous catalytic procedures. © 2002 Elsevier Science B.V. All rights reserved.
Journal of Molecular Catalysis A Chemical 01/2002; 185:203-210. · 2.95 Impact Factor
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ABSTRACT: This paper describes the immobilization of anionic and cationic metalloporphyrins into the nanotubes/nanoscrolls of natural halloysite and investigates the catalytic activity of these novel materials in the oxidation of organic substrates. Two methods for metalloporphyrin immobilization were tested: immobilization under pressure and immobilization under stirring/reflux conditions. The best immobilization rate (100%) was obtained with the anionic iron(III) porphyrin immobilized via the pressurized system. A cationic iron(III) porphyrin was also immobilized into the support with relatively good yields, but no encouraging results were obtained for the immobilization of a neutral iron(III) porphyrin. The obtained materials were characterized by UV–vis and infrared spectroscopies, X-ray diffraction, and transmission electron microscopy. The catalytic activity of a fully immobilized iron(III) porphyrin was evaluated in the oxidation of cyclo-octene, cyclohexane and n-heptane, using iodosylbenzene as the oxygen donor. It has been shown that these novel immobilized catalysts are a promising system for selective oxidation reactions.Graphical abstractThe process of metalloporphyrin immobilization into the nanotubes/nanoscrolls of natural halloysite is described. Immobilization of 100% was attained with an anionic iron(III) porphyrin via a pressurized system. The catalytic activities of the new materials were evaluated in the oxidation of cyclo-octene, cyclohexane and n-heptane. The results obtained in the present study show that these novel immobilized catalysts are a promising system for selective oxidation reactions.
Journal of Molecular Catalysis A Chemical 283:99-107. · 2.95 Impact Factor
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ABSTRACT: This paper describes the synthesis of a first-generation iron porphyrin catalyst immobilized in a tubular/delaminated kaolinite. Kaolinite was mechanochemically intercalated with urea followed by n-hexylamine, and the catalyst was prepared by submitting the kaolinite/hexylamine intercalation compound to a sonication procedure in the presence of two different iron porphyrin solutions. The materials thus obtained were characterized by UV–vis and IR spectroscopies, XRD, and TEM. The procedure delaminated part of the kaolinite, yielding scroll-like nanotubes, with the metalloporphyrins immobilized in the mixture. The catalytic activity of the materials for cyclohexane and n-heptane oxidation was investigated using iodosylbenzene as the oxygen donor and the products were analyzed by gas chromatography. The results show a promising catalytic system for selective oxidation reactions.
Journal of Catalysis. 242(1):110-117.
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ABSTRACT: An Mg–Al layered double hydroxide containing intercalated NO3− anions (LDH-N) was synthesized and subsequently submitted to a reaction with triethanolamine as modifying agent (LDH-TEA). A neutral iron(III) porphyrin was immobilized onto both solids LDH-N and LDH-TEA, and the catalytic activity of the resulting FePor-LDH-N and FePor-LDH-TEA was evaluated in the oxidation of (Z)-cyclooctene, cyclohexane, and heptane using iodosylbenzene as oxidant. Characterization of FePor-LDH-N and FePor-LDH-TEA by UV–vis, FTIR, XRD, XPS, EPR, TGA/DTA, and SEM was also accomplished. The products from the catalytic reactions were analyzed by GC, using an FID detector. The catalytic activity of FePor-LDH-TEA in the oxidation of cyclohexane was around 5 times higher than that obtained with FePor-LDH-N, which does not contain the modifying agent. Moreover, the FePor-LDH-TEA solid displayed significant selectivity in the oxidation of heptane, a substrate that is difficult to oxidize; in fact, a total product yield over 30.0% was achieved. Finally, the performance of the FePor-LDH-TEA catalyst can be attributed to the higher FePor load in this solid, which is 3 times larger compared with FePor-LDH-N. A proposal concerning the mode of FePor immobilization onto the modified LDH is suggested.Graphical abstractView high quality image (67K)Research highlights▶ A neutral ironporphyrin was immobilized onto an Mg–Al HDL-NO3− (FePor-LDH-N) (a). ▶ A neutral ironporphyrin was immobilized onto Mg–Al–TEA(FePor-LDH-TEA) (b). ▶ Catalytic oxidation of cyclooctene, cyclohexane and heptanes was studied. ▶ Catalytic activity of FePor-LDH-TEA was around 5 times higher than FePor-LDH-N. ▶Significant selectivity in the oxidation of heptane was achieved (30.0%).
Applied Catalysis A: General. 386:51-59.
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Journal of Catalysis. 274(2):130-141.
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ABSTRACT: An anionic iron(III) porphyrin was immobilized on a synthetic aluminosilicate obtained by the sol–gel process and used as catalyst in the oxidation of organic substrates. Aluminosilicate was prepared by modification of a method previously described in the literature, using an ethanol/water solution of AlCl3·6H2O and Si(OC2H5)4 (TEOS). Iron(III) porphyrin immobilization was carried out using magnetic stirring and reflux, and a good immobilization rate (88%) was obtained. Immobilization of a neutral iron(III) porphyrin on the solid was also tested, without success. The obtained materials were characterized by ultraviolet–visible and infrared spectroscopies, X-ray diffraction, TGA analysis, nitrogen absorption, and electron paramagnetic resonance (EPR). The catalytic activity of the immobilized iron(III) porphyrin was evaluated in the oxidation of cyclooctene, cyclohexane, and n-heptane, using iodosylbenzene as the oxygen donor. The results obtained in the present study show that the novel immobilized catalyst is a promising system for efficient and selective oxidation reactions. Besides that, the stable interaction between the iron(III) porphyrin complex and the support enables reuse of the heterogeneous catalyst.
Colloids and Surfaces A Physicochemical and Engineering Aspects 349:162-169. · 2.24 Impact Factor
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ABSTRACT: This paper reports the intermediate species of six different manganese porphyrins of first, second and third generation obtained by electrolysis and homogeneous chemical oxidation catalysis of cyclohexane. In order to understand some of the electrochemical processes and transitions involved, studies focused on coupling techniques involving electro-generated species and UV–vis and EPR spectroscopy methods applied to characterize the species formed in situ. Homogenous catalysis for cyclohexane oxidation showed that Mn-second-generation porphyrins are better catalysts than the other classes, and also have the most catalyst recovery, with lower destruction of the catalyst during the run. For all porphyrins, it was possible to observe various intermediate species such as Mn(II), Mn(IV) and radicals. Only for the third-generation porphyrin was it possible to observe a radical species during electro-reductive procedures with SEC–EPR spectroscopy.
Applied Catalysis A: General. 308:172-181.
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ABSTRACT: MgAl layered double hydroxide (LDH) intercalated with dodecylsulfate, was exfoliated in toluene, and the single-layer suspension was reacted with (3-aminopropyl)triethoxysilane (3APTS) in the same solvent. After washing with toluene and acetone to remove the excess reagent and drying procedure, the solid was reacted with neutral and anionic iron(III) porphyrins in toluene and methanol, respectively. The products were analyzed by powder X-ray diffraction, Fourier transform infrared spectroscopy, electron paramagnetic resonance, ultraviolet–visible light, and atomic absorption spectrometric techniques. All of the data are consistent with the grafting of the LDH interlayers with 3APTS and immobilization of the iron porphyrins on the pendent terminal amino groups positioned at the top the grafted molecule. Based on these results, a schematic representation for the immobilization and preliminary catalytic oxidation reactions is presented.
Journal of Catalysis.
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ABSTRACT: Realizaçăo : UFPRTV Reportagem : Eduardo Bettega Narraçăo : Caio Marques Imagens : Beto Luthi Ediçăo de imagens : Celso Bahl Entrevistado : Alesandro Bail, mestrando em Quimica Inorganica, UFPR Entrevistada : Maria Aparecida F.César-Oliveira, Coordenadora do Laboratorio de Quimica de Polimeros - UFPR Entrevistada : Shirley Nakagaki, coordenadora do Laboratorio de Catalisadores Heterogeneos - UFPR Entrevistada : Prof. Nadia Krieger, coordenadora do Laboratorio de Tecnologia Enzimatica - UFPR Entrevistado : Prof. Luiz Pereira Ramos, coordenador do Grupo de Pesquisa do Biodiesel
oai:ufpr.br:243842.
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ABSTRACT: In this paper we report the immobilization and characterization of neutral and pentacationic iron porphyrins into the nanometric pores of an inorganic matrix (porous vycor glass, PVG) and the use of these materials as catalyst in mimetic–enzymatic processes. The concentration of iron porphyrin in the large glass pores depends on the conditions present during the incorporation process. The materials obtained were used as catalyst in the oxidation reaction of cyclohexane and cyclohexene by iodosylbenzene. The catalytic results were promising, evidencing adequate characteristics of PVG for immobilization of iron porphyrin and strong potential of these nanocomposites for heterogeneous catalytic procedures.
Journal of Molecular Catalysis A: Chemical.
