Reduction of ethanol emissions using manganese oxides supported metallic monoliths: a pilot-scale plant study

Metallic monoliths were prepared by anodized aluminum-scale pilot plant, using sulfuric acid as electrolyte. Anodisation tests were conducted at different times and different temperatures of the electrolytic bath. Aluminum monolith anodized at 40ºC for 30 min was selected for catalysts support. The monoliths were impregnated by two methods: i) impregnation in two stages using two Mn salts in an aqueous medium, and ii) impregnation using a KMnO4 solution in acetone. The last monolith presented a higher and a more homogeneous deposit of manganese oxide layer. The catalytic activity was tested in the total oxidation reaction of ethanol in a pilot-scale reactor at 50 L min-1, and ethanol concentrations of 900, 1800 and 3600 ppm. Monolith impregnated using acetone solution was more active that prepared in aqueous solution in all the experiments carried out.Fil: Peluso, Miguel Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Sambeth, Jorge Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Thomas, Horacio Jorge. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina. Universidad Nacional de La Plata; Argentin

Reduction of ethanol emissions using manganese oxides supported metallic monoliths: a pilot-scale plant study

Metallic monoliths were prepared by anodized aluminum-scale pilot plant, using sulfuric acid as electrolyte. Anodisation tests were conducted at different times and different temperatures of the electrolytic bath. Aluminum monolith anodized at 40ºC for 30 min was selected for catalysts support. The monoliths were impregnated by two methods: i) impregnation in two stages using two Mn salts in an aqueous medium, and ii) impregnation using a KMnO4 solution in acetone. The last monolith presented a higher and a more homogeneous deposit of manganese oxide layer. The catalytic activity was tested in the total oxidation reaction of ethanol in a pilot-scale reactor at 50 L min-1, and ethanol concentrations of 900, 1800 and 3600 ppm. Monolith impregnated using acetone solution was more active that prepared in aqueous solution in all the experiments carried out.Centro de Investigación y Desarrollo en Ciencias AplicadasComisión de Investigaciones Científicas de la provincia de Buenos Aire

A study of the temperature effect on Hantzsch reaction selectivity using Mn and Ce oxides under solvent-free conditions

In this communication, four materials (CeO2, CeO2(Cu), MnOx, and MnOx(Cu))were prepared, characterized and tested as catalysts, in solvent-free conditions, for the multicomponent Hantzsch reactions to obtain alternatively the 1,4-dihydropyridine or 2-phenylpyridine depending on the reaction conditions. 1,4-Dihydropyridine 4 was the main product formed at 80 °C (76%), and 2-phenylpyridine 7 was the main product at 40 °C (91%), in oxidant-free conditions, using CeO2 catalyst. It is the first report that shows that, not only the temperature but also the nature of the catalyst may change the product selectivity in Hantzsch reactions.Centro de Investigación y Desarrollo en Ciencias Aplicada

Adsorción de fenol en sólidos mesoporosos Mn-Ce-O comúnmente utilizados en CWAO

Se prepararon una serie de óxidos de Mn-Ce por co-precipitación a partir de sus nitratos en medio alcalino. Los sólidos así obtenidos fueron caracterizados por DRX, FTIR, XPS, sortometría de N2 y adsorción de fenol. El estudio de la remoción de fenol se llevó a cabo a 100 ºC y Presión atmosférica. Los estudios de caracterización señalan la formación de una solución sólida y una fuerte interacción Mn- Ce cuyas propiedades dependen de la cantidad relativa de los metales principales. La muestra Mn-Ce (Na) 7/3 es la que resulta ser la más activa para la remoción de fenol debido a una menor interacción Mn-Ce en el ensamble Mn-Ce-O lo cual favorecería la adsorción-oxidación del contaminante sobre este sólido.Centro de Investigación y Desarrollo en Ciencias Aplicada

Removal of phenol from aqueous solutions by adsorption onto Mn-Ce-K solids

Mn-Ce solids were used for the adsorption of phenol from aqueous solution at 25 and 50 C. The samples were prepared with a Mn-Ce molar ratio Between 0 and 100 % by the alkaline co-precipitation method (KOH). Structural studies showed the formation of cryptomelane, Mn2O3, Mn5O8, Mn3O4 and CeO2. The formation of different phases is a function of the Ce concentration. The adsorption isotherms of phenol were determined and modelled with Langmuir and Freundlich equations. Sample 7/3 had a high adsorption capacity. Thermodynamic parameters, in flat and vertical position of phenol, were calculated. These parameters indicated that the adsorption of phenol onto Mn-Ce was spontaneous and exothermic. The DRIFTS study detected of both phenol and phenolate species adsorbed on the surface and the aromatic ring of phenol is parallel to the surface. The interaction between Mn and Ce enhanced the reducibility of the oxides and activated oxygen, which is favorable for the adsorption process.Centro de Investigación y Desarrollo en Ciencias Aplicada

An analysis of the first steps of phenol adsorption-oxidation over coprecipitated Mn–Ce catalysts: a DRIFTS study

A series of Mn–Ce(M) solids (M = K or Na), with molar ratios 100–0, 50–50 and 0–100 were prepared by co-precipitation of manganese and cerium nitrate from NaOH or KOH solutions at pH = 11. In addition, part of the solids precipitated with NaOH were dried and impregnated with a Cu²⁺ salt. The solids were characterized by XRD, Specific Surface Area, XPS and EDS. The characterization analyses show the formation of Mn mixed oxides with different oxidation states (Mn³⁺, Mn⁴⁺), for samples without Ce or Mn–Ce(M) 50–50. In the latter solid and in the one where there is no Mn, the formation of CeO₂ (fluorite type) was detected. The samples were tested in the phenol removal in water at 100 °C and at atmospheric pressure with the aim to analyze the adsorbed species in the first stage of the adsorption-oxidation mechanisms. The results indicate, on the one hand, that [MnOₓ] is the active species in the process and that the most active solids are those that present (i) a higher concentration of OI, (ii) a higher amount of Mn⁴⁺ ions. DRIFT spectroscopy showed a possible mechanism of phenol adsorption on two sites, in the first one by H interaction of OH (phenol) with an OH of the catalyst and in the second, by the formation of a phenolate species between an O (OH phenol) and Mnⁿ⁺.Centro de Investigación y Desarrollo en Ciencias AplicadasPlanta Piloto Multipropósito - Laboratorio de Servicios a la Industria y al Sistema Científic

A theoretical-experimental study of Wells-Dawson phospho-tungstic heteropolyacid: An explanation of the pseudoliquid or surface-type behaviour

The aim of the present work is to predict theoretically the nature of the mechanism of catalytic behaviour, pseudoliquid or surface-type, of Wells-Dawson solid acid (WDA). For this purpose, we took into account the dipolar moment of the substrates and the presence of H5O2 + species in their structure, considering both theoretical and experimental results. In the present paper we studied experimentally the deprotection reaction of aldehydes from 1,1-diacetates. These theoretical and experimental results together with our previous works indicate that the catalytic behaviour of WDA is a function of the dipolar moment of organic molecules and the presence of H5O2 + species. The pseudoliquid or surface-type behaviour depends on the physicochemical properties of the organic structure and its possibility of interaction with H5O2 +.Centro de Investigación y Desarrollo en Ciencias AplicadasFacultad de Ciencias Agrarias y ForestalesConsejo Nacional de Investigaciones Científicas y Técnica

Structural and optical properties of ZnO and manganese-doped ZnO

The structural, morphological and optical properties of manganese oxides supported on commercial ZnO,prepared by impregnation with manganese nitrate, were investigated. The nominal compositions of Mnin the samples were 5, 10, 15 and 20%w/w.The X-ray diffraction (XRD) experiments revealed the presenceof the ZnO wurtzite phase in all the samples, and ZnMnO3 was also found in the samples with 15 wt% and20 wt% of Mn. X-ray photoelectron spectroscopy (XPS) showed the presence of Mn2þ and Mn4þ in thexMnZnO samples. The results showed that the Mn2þ ions had substituted the Zn2þ ions without changing the wurtzite structure of ZnO, while Mn4þ might be assigned to the ZnMnO3 impurity phase.The optical band gap was found to be 3.3 eV for undoped ZnO samples and 3.10 eV for Mn-doped samples. The lattice defect distribution was investigated using the positron annihilation method. The results revealed that the average lifetime is a function of the Mn concentration and the formation of theZnMnO3 phase.Centro de Investigación y Desarrollo en Ciencias AplicadasInstituto de Física La PlataLaboratorio de Servicios a la Industria y al Sistema Científic

A theoretical-experimental study of Wells-Dawson phospho-tungstic heteropolyacid: An explanation of the pseudoliquid or surface-type behaviour

The aim of the present work is to predict theoretically the nature of the mechanism of catalytic behaviour, pseudoliquid or surface-type, of Wells-Dawson solid acid (WDA). For this purpose, we took into account the dipolar moment of the substrates and the presence of H5O2 + species in their structure, considering both theoretical and experimental results. In the present paper we studied experimentally the deprotection reaction of aldehydes from 1,1-diacetates. These theoretical and experimental results together with our previous works indicate that the catalytic behaviour of WDA is a function of the dipolar moment of organic molecules and the presence of H5O2 + species. The pseudoliquid or surface-type behaviour depends on the physicochemical properties of the organic structure and its possibility of interaction with H5O2 +.Centro de Investigación y Desarrollo en Ciencias AplicadasFacultad de Ciencias Agrarias y ForestalesConsejo Nacional de Investigaciones Científicas y Técnica

Structural and optical properties of ZnO and manganese-doped ZnO

The structural, morphological and optical properties of manganese oxides supported on commercial ZnO,prepared by impregnation with manganese nitrate, were investigated. The nominal compositions of Mnin the samples were 5, 10, 15 and 20%w/w.The X-ray diffraction (XRD) experiments revealed the presenceof the ZnO wurtzite phase in all the samples, and ZnMnO3 was also found in the samples with 15 wt% and20 wt% of Mn. X-ray photoelectron spectroscopy (XPS) showed the presence of Mn2þ and Mn4þ in thexMnZnO samples. The results showed that the Mn2þ ions had substituted the Zn2þ ions without changing the wurtzite structure of ZnO, while Mn4þ might be assigned to the ZnMnO3 impurity phase.The optical band gap was found to be 3.3 eV for undoped ZnO samples and 3.10 eV for Mn-doped samples. The lattice defect distribution was investigated using the positron annihilation method. The results revealed that the average lifetime is a function of the Mn concentration and the formation of theZnMnO3 phase.Centro de Investigación y Desarrollo en Ciencias AplicadasInstituto de Física La PlataLaboratorio de Servicios a la Industria y al Sistema Científic