Tungstophosphoric acid heterogenized onto NH₄ZSM5 as an efficient and recyclable catalyst for the photocatalytic degradation of dyes

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 °C. These can be reused at least three times without any significant decrease in degree of degradation.Facultad de Ciencias ExactasCentro de Investigación y Desarrollo en Ciencias Aplicada

Revalorización de Residuos Agrícolas por Pirólisis Térmica y Catalítica

Se realizaron pirolisis térmicas y catalíticas de cáscaras de maní en un reactor de lecho fijo a 500ºC y durante 20 minutos, con una relación biomasa:catalizador de 1:1, en pos de lograr la revalorización del desecho. Los materiales catalíticos evaluados fueron zeolitas Y en forma protónica y con 3 y 6% de níquel incorporado a la misma. Se estudió el efecto de los catalizadores sobre la composición y el rendimiento de los productos de reacción y los resultados se compararon con las corridas netamente térmicas. No se observaron diferencias cualitativas entre los bio-oils de las experiencias térmicas y catalíticas. En contraposición, el rendimiento del líquido aumentó al aumentar la proporción de níquel en el catalizador

Tungstophosphoric acid heterogenized onto NH₄ZSM5 as an efficient and recyclable catalyst for the photocatalytic degradation of dyes

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 °C. These can be reused at least three times without any significant decrease in degree of degradation.Facultad de Ciencias ExactasCentro de Investigación y Desarrollo en Ciencias Aplicada

Tungstophosphoric acid heterogenized onto NH₄ZSM5 as an efficient and recyclable catalyst for the photocatalytic degradation of dyes

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 °C. These can be reused at least three times without any significant decrease in degree of degradation.Facultad de Ciencias ExactasCentro de Investigación y Desarrollo en Ciencias Aplicada

Aplicación de fotocatalizadores obtenidos a partir de ácido tungstofosfórico sobre NH4ZSM5 en remediación de aguas contaminadas

Se prepararon materiales a partir de la inmovilización de ácido tungstofosfórico sobre zeolita NH4ZSM5 mediante impregnación húmeda para ser aplicados en la degradación de moléculas representativas de contaminantes presentes en efluentes empleando fotocatálisis heterogénea. La concentración de ácido tunstofosfórico incorporada fue de 10 y 30% p/p en el sólido obtenido. Los materiales se caracterizaron mediante diferentes técnicas fisicoquímicas. El área superficial disminuyó respecto de la matriz sin modificar como resultado de bloqueo de los poros de la zeolita. Los patrones de difracción de rayos X de las muestras modificadas presentaron los picos característicos de zeolita NH4ZSM5 y un conjunto de picos adicionales asignados a la presencia de la sal (NH4)3[PW12O40]. Además, las muestras exhibieron valores de band gap similares a los reportados para los semiconductores más estudiados. Se obtuvieron catalizadores con elevada actividad fotocatalítica en las moléculas 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´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 Investigación y Desarrollo en Ciencias Aplicada

Aplicación de Fotocatalizadores Obtenidos a partir de Ácido Tungstofosfórico sobre NH4ZSM5 en Remediación de Aguas Contaminadas

Se prepararon materiales a partir de la inmovilización de ácido tungstofosfórico sobre zeolita NH4ZSM5 mediante impregnación húmeda para ser aplicados en la degradación de moléculas representativas de contaminantes presentes en efluentes empleando fotocatálisis heterogénea. La concentración de ácido tunstofosfórico incorporada fue de 10 y 30% p/p en el sólido obtenido. Los materiales se caracterizaron mediante diferentes técnicas fisicoquímicas. El área superficial disminuyó respecto de la matriz sin modificar como resultado de bloqueo de los poros de la zeolita. Los patrones de difracción de rayos X de las muestras modificadas presentaron los picos característicos de zeolita NH4ZSM5 y un conjunto de picos adicionales asignados a la presencia de la sal (NH4)3[PW12O40]. Además, las muestras exhibieron valores de band gap similares a los reportados para los semiconductores más estudiados. Se obtuvieron catalizadores con elevada actividad fotocatalítica en las moléculas de estudio

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

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: Gómez, 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

Síntesis selectiva de benzaldehído usando zeolitas modificadas con metales de transición.

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 ºC by hydrogen peroxide thermal decomposition.Se estudió la oxidación selectiva de estireno para la obtención de benzaldehído sobre zeolitas ZSM-5 modificadas con diferentes metales de transición (cromo, cobalto, hierro, zinc, manganeso y cobre) y utilizando peróxido de hidrógeno como oxidante. Dado que los mejores resultados se obtuvieron utilizando Cr-ZSM-5, estos materiales se estudiaron evaluando el efecto del tiempo de reacción, la masa de catalizador, la relación molar estireno/hidroperóxido, la naturaleza del solvente y la temperatura de reacción. Los mejores resultados de las condiciones evaluadas se obtuvieron trabajando con una relación molar sustrato/oxidante de 0,45 y utilizando acetonitrilo como solvente, dado su carácter aprótico y de mayor polaridad de los solventes evaluados (acetonitrilo, acetona, 2-butanol y 2-propanol). El aumento en la temperatura de reacción mostró un incremento en la conversión de estireno, el cual se desaceleró al superar los 60 ºC por descomposición térmica del peróxido de hidrógeno

Revalorización de Residuos Agrícolas por Pirólisis Térmica y Catalítica

Thermal and catalytic pyrolysis of peanut shells were performed in a fixed-bed reactor at 500ºC 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 térmicas y catalíticas de cáscaras de maní en un reactor de lecho fijo a 500ºC y durante 20 minutos, con una relación biomasa:catalizador de 1:1, en pos de lograr la revalorización del desecho. Los materiales catalíticos evaluados fueron zeolitas Y en forma protónica y con 3 y 6% de níquel incorporado a la misma. Se estudió el efecto de los catalizadores sobre la composición y el rendimiento de los productos de reacción y los resultados se compararon con las corridas netamente térmicas. No se observaron diferencias cualitativas entre los bio-oils de las experiencias térmicas y catalíticas. En contraposición, el rendimiento del líquido aumentó al aumentar la proporción de níquel en el catalizador

Síntese de Zeólitos ZSM-11 com Porosidade de Hierarquia

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 creación de porosidad adicional en zeolitas microporosas  con estructura ZSM-11 mediante síntesis directa utilizando un surfactante catiónico (CTAB) como plantilla mesoporosa. Se investigó el efecto del tiempo de cristalización y la modificación del contenido de CTAB en la síntesis sobre la obtención de la estructura cristalina y la generación de mesoporosidad. Los sólidos obtenidos fueron caracterizados por Difracción de Rayos X (DRX), Isotermas de adsorción y desorción de nitrógeno, área superficial BET, Microscopia electrónica de barrido (SEM) y Espectroscopia de emisión atómica con plasma inductivamente acoplado (ICP- AES). Los resultados confirmaron que las zeolitas obtenidas poseen mesoporosidad en su estructura conservando la microporosidad intrínseca de la zeolita.Este trabalho propõe a criação de porosidade adicional em zeólitos microporosos com estrutura ZSM-11 por síntese direta usando um surfactante catiônico (CTAB) como modelo mesoporoso. O efeito do tempo de cristalização e a modificação do conteúdo de CTAB na síntese sobre a obtenção da estrutura cristalina e a geração de mesoporosidade foram investigados. Os sólidos obtidos foram caracterizados por difração de raios X (DRX), isotermas de adsorção e dessorção de nitrogênio, área de superfície BET, microscopia eletrônica de varredura (MEV) e espectroscopia de emissão atômica com plasma indutivamente acoplado (ICP-AES). Os resultados confirmaram que os zeólitos obtidos possuem mesoporosidade em sua estrutura, preservando a microporosidade intrínseca do zeólito