16 research outputs found

    Revalorizaci贸n de Residuos Agr铆colas por Pir贸lisis T茅rmica y Catal铆tica

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    Se realizaron pirolisis t茅rmicas y catal铆ticas de c谩scaras de man铆 en un reactor de lecho fijo a 500潞C y durante 20 minutos, con una relaci贸n biomasa:catalizador de 1:1, en pos de lograr la revalorizaci贸n del desecho. Los materiales catal铆ticos evaluados fueron zeolitas Y en forma prot贸nica y con 3 y 6% de n铆quel incorporado a la misma. Se estudi贸 el efecto de los catalizadores sobre la composici贸n y el rendimiento de los productos de reacci贸n y los resultados se compararon con las corridas netamente t茅rmicas. No se observaron diferencias cualitativas entre los bio-oils de las experiencias t茅rmicas y catal铆ticas. En contraposici贸n, el rendimiento del l铆quido aument贸 al aumentar la proporci贸n de n铆quel en el catalizador

    Tungstophosphoric acid heterogenized onto NH<sub>4</sub>ZSM5 as an efficient and recyclable catalyst for the photocatalytic degradation of dyes

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    Materials based on tungstophosphoric acid (TPA) immobilized on NH4ZSM5 zeolite were prepared by wet impregnation of the zeolite matrix with TPA aqueous solutions. Their concentration was varied in order to obtain TPA contents of 5%, 10%, 20%, and 30% w/w in the solid. The materials were characterized by N2 adsorption-desorption isotherms, XRD, FT-IR, 31P MAS-NMR, TGA.-DSC, DRS-UV-Vis, and the acidic behavior was studied by potentiometric titration with n-butylamine. The BET surface area (SBET) decreased when the TPA content was raised as a result of zeolite pore blocking. The X-ray diffraction patterns of the solids modified with TPA only presented the characteristic peaks of NH4ZSM5 zeolites, and an additional set of peaks assigned to the presence of (NH4)3PW12O40. According to the Fourier transform infrared and 31P magic angle spinning-nuclear magnetic resonance spectra, the main species present in the samples was the [PW12O40]3- anion, which was partially transformed into the [P2W21O71]6- anion during the synthesis and drying steps. The thermal stability of the NH4ZSM5TPA materials was similar to that of their parent zeolites. Moreover, the samples with the highest TPA content exhibited band gap energy values similar to those reported for TiO2. The immobilization of TPA on NH4ZSM5 zeolite allowed the obtention of catalysts with high photocatalytic activity in the degradation of methyl orange dye (MO) in water, at 25 掳C. These can be reused at least three times without any significant decrease in degree of degradation.Facultad de Ciencias ExactasCentro de Investigaci贸n y Desarrollo en Ciencias Aplicada

    Tungstophosphoric acid heterogenized onto NH<sub>4</sub>ZSM5 as an efficient and recyclable catalyst for the photocatalytic degradation of dyes

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    Materials based on tungstophosphoric acid (TPA) immobilized on NH4ZSM5 zeolite were prepared by wet impregnation of the zeolite matrix with TPA aqueous solutions. Their concentration was varied in order to obtain TPA contents of 5%, 10%, 20%, and 30% w/w in the solid. The materials were characterized by N2 adsorption-desorption isotherms, XRD, FT-IR, 31P MAS-NMR, TGA.-DSC, DRS-UV-Vis, and the acidic behavior was studied by potentiometric titration with n-butylamine. The BET surface area (SBET) decreased when the TPA content was raised as a result of zeolite pore blocking. The X-ray diffraction patterns of the solids modified with TPA only presented the characteristic peaks of NH4ZSM5 zeolites, and an additional set of peaks assigned to the presence of (NH4)3PW12O40. According to the Fourier transform infrared and 31P magic angle spinning-nuclear magnetic resonance spectra, the main species present in the samples was the [PW12O40]3- anion, which was partially transformed into the [P2W21O71]6- anion during the synthesis and drying steps. The thermal stability of the NH4ZSM5TPA materials was similar to that of their parent zeolites. Moreover, the samples with the highest TPA content exhibited band gap energy values similar to those reported for TiO2. The immobilization of TPA on NH4ZSM5 zeolite allowed the obtention of catalysts with high photocatalytic activity in the degradation of methyl orange dye (MO) in water, at 25 掳C. These can be reused at least three times without any significant decrease in degree of degradation.Facultad de Ciencias ExactasCentro de Investigaci贸n y Desarrollo en Ciencias Aplicada

    Tungstophosphoric acid heterogenized onto NH<sub>4</sub>ZSM5 as an efficient and recyclable catalyst for the photocatalytic degradation of dyes

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    Materials based on tungstophosphoric acid (TPA) immobilized on NH4ZSM5 zeolite were prepared by wet impregnation of the zeolite matrix with TPA aqueous solutions. Their concentration was varied in order to obtain TPA contents of 5%, 10%, 20%, and 30% w/w in the solid. The materials were characterized by N2 adsorption-desorption isotherms, XRD, FT-IR, 31P MAS-NMR, TGA.-DSC, DRS-UV-Vis, and the acidic behavior was studied by potentiometric titration with n-butylamine. The BET surface area (SBET) decreased when the TPA content was raised as a result of zeolite pore blocking. The X-ray diffraction patterns of the solids modified with TPA only presented the characteristic peaks of NH4ZSM5 zeolites, and an additional set of peaks assigned to the presence of (NH4)3PW12O40. According to the Fourier transform infrared and 31P magic angle spinning-nuclear magnetic resonance spectra, the main species present in the samples was the [PW12O40]3- anion, which was partially transformed into the [P2W21O71]6- anion during the synthesis and drying steps. The thermal stability of the NH4ZSM5TPA materials was similar to that of their parent zeolites. Moreover, the samples with the highest TPA content exhibited band gap energy values similar to those reported for TiO2. The immobilization of TPA on NH4ZSM5 zeolite allowed the obtention of catalysts with high photocatalytic activity in the degradation of methyl orange dye (MO) in water, at 25 掳C. These can be reused at least three times without any significant decrease in degree of degradation.Facultad de Ciencias ExactasCentro de Investigaci贸n y Desarrollo en Ciencias Aplicada

    Aplicaci贸n de Fotocatalizadores Obtenidos a partir de 脕cido Tungstofosf贸rico sobre NH4ZSM5 en Remediaci贸n de Aguas Contaminadas

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    Se prepararon materiales a partir de la inmovilizaci贸n de 谩cido tungstofosf贸rico sobre zeolita NH4ZSM5 mediante impregnaci贸n h煤meda para ser aplicados en la degradaci贸n de mol茅culas representativas de contaminantes presentes en efluentes empleando fotocat谩lisis heterog茅nea. La concentraci贸n de 谩cido tunstofosf贸rico incorporada fue de 10 y 30% p/p en el s贸lido obtenido. Los materiales se caracterizaron mediante diferentes t茅cnicas fisicoqu铆micas. El 谩rea superficial disminuy贸 respecto de la matriz sin modificar como resultado de bloqueo de los poros de la zeolita. Los patrones de difracci贸n de rayos X de las muestras modificadas presentaron los picos caracter铆sticos de zeolita NH4ZSM5 y un conjunto de picos adicionales asignados a la presencia de la sal (NH4)3[PW12O40]. Adem谩s, las muestras exhibieron valores de band gap similares a los reportados para los semiconductores m谩s estudiados. Se obtuvieron catalizadores con elevada actividad fotocatal铆tica en las mol茅culas de estudio

    Aplicaci贸n de fotocatalizadores obtenidos a partir de 谩cido tungstofosf贸rico sobre NH4ZSM5 en remediaci贸n de aguas contaminadas

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    Se prepararon materiales a partir de la inmovilizaci贸n de 谩cido tungstofosf贸rico sobre zeolita NH4ZSM5 mediante impregnaci贸n h煤meda para ser aplicados en la degradaci贸n de mol茅culas representativas de contaminantes presentes en efluentes empleando fotocat谩lisis heterog茅nea. La concentraci贸n de 谩cido tunstofosf贸rico incorporada fue de 10 y 30% p/p en el s贸lido obtenido. Los materiales se caracterizaron mediante diferentes t茅cnicas fisicoqu铆micas. El 谩rea superficial disminuy贸 respecto de la matriz sin modificar como resultado de bloqueo de los poros de la zeolita. Los patrones de difracci贸n de rayos X de las muestras modificadas presentaron los picos caracter铆sticos de zeolita NH4ZSM5 y un conjunto de picos adicionales asignados a la presencia de la sal (NH4)3[PW12O40]. Adem谩s, las muestras exhibieron valores de band gap similares a los reportados para los semiconductores m谩s estudiados. Se obtuvieron catalizadores con elevada actividad fotocatal铆tica en las mol茅culas de estudio.Tungstophosphoric acid inmobilized on NH4ZSM5 zeolite were prepared by the wet impregnation technique for their application as catalyst in photocatalytic degradation reactions of representative molecules of pollutants present in effluents. Tungstophosphoric acid concentrations in the solid were 10 and 30 w/w %, respectively. These materials were characterized by different physicochemical techniques in order to determine their properties. When tungstophophoric acid content was increased, surface area decreased with respect to the unmodified matrix as result of the blockage of the zeolite麓s pores. XRD patterns of the modified solids, showed NH4ZSM5 characteristic peaks and new signals assigned to (NH4)3[PW12O40] salt. Moreover, the samples exhibited similar band gap values to those reported for the most studied semiconductors. According to catalytic results, the obtained materials resulted adequate photocatalysts for the studied molecules degradation.Centro de Investigaci贸n y Desarrollo en Ciencias Aplicada

    Greener Method to Obtain a Key Intermediate of Vitamin E over Cu-ZSM-5

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    The catalytic oxidation of 2,3,5-trimethylphenol was performed over transition metals modified ZSM-5 zeolites employing hydrogen peroxide as oxidant under mild reaction conditions. Catalysts samples were characterized by several techniques (XRD, FTIR, BET, AA) and cristallinity and orthorhombic symmetry were confirmed for all of them. Best catalytic results were obtained for Cu-ZSM-5 sample, so further activity studies were done over this material. 2,3,5-trimethyl-1,4-benzoquinone was obtained as the main product of the selective oxidation. Reaction parameters (nature of the solvent, hydrogen peroxide concentration, reaction time, catalyst mass, substrate initial concentration and reaction temperature) were evaluated to reach the optimum reaction conditions. According to the obtained results, an apparent activation energy of 52.33 kJ/mol was calculated.Fil: Saux, Clara. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Cordoba. Centro de Investigacion y Tecnologia Quimica; Argentina. Universidad Tecnologica Nacional. Facultad Regional Cordoba; ArgentinaFil: Renzini, Maria Soledad. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Cordoba. Centro de Investigacion y Tecnologia Quimica; Argentina. Universidad Tecnologica Nacional. Facultad Regional Cordoba; ArgentinaFil: G贸mez, Silvina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Cordoba. Centro de Investigacion y Tecnologia Quimica; Argentina. Universidad Tecnologica Nacional. Facultad Regional Cordoba; ArgentinaFil: Pierella, Liliana Beatriz. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Cordoba. Centro de Investigacion y Tecnologia Quimica; Argentina. Universidad Tecnologica Nacional. Facultad Regional Cordoba; Argentin

    S铆ntesis selectiva de benzaldeh铆do usando zeolitas modificadas con metales de transici贸n.

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    The selective styrene oxidation to benzaldehyde was studied over ZSM-5 zeolites modified with various transition metal cations (chromium, cobalt, iron, zinc, manganese and cupper) and using hydrogen peroxide as oxidant agent. As best results were obtained using Cr-ZSM-5, they were studied evaluating reaction time, catalyst mass, styrene/hydrogen peroxide molar ratio, solvent nature and reaction temperature effect. Best results under evaluated conditions were obtained using a 0.45 substrate/oxidant molar ratio and acetonitrile as solvent, because of its aprotic and highest polar character of all the evaluated solvents (acetonitrile, acetone, 2-butanol and 2-propanol). The reaction temperature enhancement produced an increase on styrene conversion, which was decelerated over 60 潞C by hydrogen peroxide thermal decomposition.Se estudi贸 la oxidaci贸n selectiva de estireno para la obtenci贸n de benzaldeh铆do sobre zeolitas ZSM-5 modificadas con diferentes metales de transici贸n (cromo, cobalto, hierro, zinc, manganeso y cobre) y utilizando per贸xido de hidr贸geno como oxidante. Dado que los mejores resultados se obtuvieron utilizando Cr-ZSM-5, estos materiales se estudiaron evaluando el efecto del tiempo de reacci贸n, la masa de catalizador, la relaci贸n molar estireno/hidroper贸xido, la naturaleza del solvente y la temperatura de reacci贸n. Los mejores resultados de las condiciones evaluadas se obtuvieron trabajando con una relaci贸n molar sustrato/oxidante de 0,45 y utilizando acetonitrilo como solvente, dado su car谩cter apr贸tico y de mayor polaridad de los solventes evaluados (acetonitrilo, acetona, 2-butanol y 2-propanol). El aumento en la temperatura de reacci贸n mostr贸 un incremento en la conversi贸n de estireno, el cual se desaceler贸 al superar los 60 潞C por descomposici贸n t茅rmica del per贸xido de hidr贸geno

    Revalorizaci贸n de Residuos Agr铆colas por Pir贸lisis T茅rmica y Catal铆tica

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    Thermal and catalytic pyrolysis of peanut shells were performed in a fixed-bed reactor at 500潞C for 20 minutes and with a biomass:catalyst ratio of 1:1, in order to reach this discard revalorization. The catalytic materials tested were Y zeolites in the proton form and with the addition of 3 and 6% of nickel. The effect of the catalysts over the composition and product yields was investigated and the results were compared with the non-catalytic experiments. No qualitative differences were observed in the bio-oils obtained from catalytic and thermal runs. On the contrary, bio-oil yield increased with increasing the proportion of nickel over the zeolite.Se realizaron pirolisis t茅rmicas y catal铆ticas de c谩scaras de man铆 en un reactor de lecho fijo a 500潞C y durante 20 minutos, con una relaci贸n biomasa:catalizador de 1:1, en pos de lograr la revalorizaci贸n del desecho. Los materiales catal铆ticos evaluados fueron zeolitas Y en forma prot贸nica y con 3 y 6% de n铆quel incorporado a la misma. Se estudi贸 el efecto de los catalizadores sobre la composici贸n y el rendimiento de los productos de reacci贸n y los resultados se compararon con las corridas netamente t茅rmicas. No se observaron diferencias cualitativas entre los bio-oils de las experiencias t茅rmicas y catal铆ticas. En contraposici贸n, el rendimiento del l铆quido aument贸 al aumentar la proporci贸n de n铆quel en el catalizador

    S铆ntese de Ze贸litos ZSM-11 com Porosidade de Hierarquia

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    In this work we propose the creation of additional porosity in microporous zeolites with ZSM-11 structure by direct synthesis using a cationic surfactant (CTAB) as a mesoporous template. The effects of crystallization time and CTAB content on the crystalline structure and the mesoporosity generation were investigated. The obtained solids were characterized by X-ray diffraction (XRD), nitrogen adsorption and desorption isotherms, BET surface area, scanning electron microscopy (SEM) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The results confirmed that the obtained zeolites possess mesoporosity in their structure conserving the intrinsic microporosity of this kind of materials.En este trabajo se propone la creaci贸n de porosidad adicional en zeolitas microporosas&nbsp; con estructura ZSM-11 mediante s铆ntesis directa utilizando un surfactante cati贸nico (CTAB) como plantilla mesoporosa. Se investig贸 el efecto del tiempo de cristalizaci贸n y la modificaci贸n del contenido de CTAB en la s铆ntesis sobre la obtenci贸n de la estructura cristalina y la generaci贸n de mesoporosidad. Los s贸lidos obtenidos fueron caracterizados por Difracci贸n de Rayos X (DRX), Isotermas de adsorci贸n y desorci贸n de nitr贸geno, 谩rea superficial BET, Microscopia electr贸nica de barrido (SEM) y Espectroscopia de emisi贸n at贸mica con plasma inductivamente acoplado (ICP- AES). Los resultados confirmaron que las zeolitas obtenidas poseen mesoporosidad en su estructura conservando la microporosidad intr铆nseca de la zeolita.Este trabalho prop玫e a cria莽茫o de porosidade adicional em ze贸litos microporosos com estrutura ZSM-11 por s铆ntese direta usando um surfactante cati么nico (CTAB) como modelo mesoporoso. O efeito do tempo de cristaliza莽茫o e a modifica莽茫o do conte煤do de CTAB na s铆ntese sobre a obten莽茫o da estrutura cristalina e a gera莽茫o de mesoporosidade foram investigados. Os s贸lidos obtidos foram caracterizados por difra莽茫o de raios X (DRX), isotermas de adsor莽茫o e dessor莽茫o de nitrog锚nio, 谩rea de superf铆cie BET, microscopia eletr么nica de varredura (MEV) e espectroscopia de emiss茫o at么mica com plasma indutivamente acoplado (ICP-AES). Os resultados confirmaram que os ze贸litos obtidos possuem mesoporosidade em sua estrutura, preservando a microporosidade intr铆nseca do ze贸lito
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