Effect of manganese substitution on the physicochemical properties and catalytic toluene oxidation activities of Mg–Al layered double hydroxides

Velu, S.; Shah, Naimish; Jyothi, T. M.; Sivasanker, S.

doi:10.1016/s1387-1811(99)00123-7

Cited by 205 publications

(115 citation statements)

References 32 publications

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“…A wide and strong band is located between 300 and 700 nm for Mn/SBA-15. The band at 300-500 nm can be assigned to a mixture of Mn 3+ and Mn 4+ oxo species and that at 500-700 nm to Mn 2+ [30,31], as shown in Table 2. Two adsorption bands can be observed at 219 and 404 nm for Ag/SBA-15, which are assigned to Ag + and Ag [32].…”

Section: Bet Resultsmentioning

confidence: 99%

The improved reactivity of manganese catalysts by Ag in catalytic oxidation of toluene

Qin

et al. 2013

Applied Catalysis B: Environmental

184

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Section: Bet Resultsmentioning

confidence: 99%

The improved reactivity of manganese catalysts by Ag in catalytic oxidation of toluene

Qin

et al. 2013

Applied Catalysis B: Environmental

184

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“…Sin embargo, el parámetro c, que corresponde al espesor de tres láminas del tipo de la brucita más su espacio interlaminar, reveló un valor ligeramente menor en HTMn (2,26 nm) que en HTMgAl (2,34 nm). Este resultado se atribuyó a un incremento de las fuerzas electrostáticas entre las láminas y las interláminas, efecto que sólo es posible si se encuentran los iones Mn 3+ presentes en las láminas brucíticas (Velu, et al, 1999). La presencia de estos iones dentro de la estructura laminar explicaría, igualmente, por qué el Mn no afecta el parámetro a de la hidrotalcita HTMn.…”

Section: Caracterización Del Precursor Hidrotalcitaunclassified

“…La formación de Mn 3 O 4 probablemente se debe a que parte del Mn 2+ se oxida hasta Mn 3+ en medio básico (condiciones de síntesis empleadas). Estos resultados concuerdan con los valores de los parámetros cristalográficos calculados para esta hidrotalcita (Fernández, et al, 1994;Velu, et al, 1999).…”

Section: Caracterización Del Precursor Hidrotalcitaunclassified

“…Cuando existe la relación Mg:Mn:Al=2,2:0,8:1, se produce la formación de una única fase hidrotalcita y con el incremento del contenido de Mn se obtiene la mezcla de las fases LDH, Mn(OH) 2 y MnCO 3 . Igualmente, los autores han reportado que cuando las hidrotalcitas se calcinan a 500 °C, se genera una solución sólida de MgO y cargas elevadas de Mn y, además de MgO, se forman las espinelas Mn 3 O 4 y MnAl 2 O 4 (Velu, et al, 1999). En la evaluación de la oxidación del tolueno, del etanol y del butanol sobre óxidos mixtos de Mn, Co-Mn y Cu-Mn preparados por la descomposición térmica de hidrotalcitas, los materiales han exhibido un excelente comportamiento en la oxidación de los compuestos orgánicos volátiles (COV), atribuido principalmente a la generación de fases amorfas y ciclos de redox en los óxidos (Aguilera, et al, 2011).…”

Section: Introductionunclassified

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Catalizadores de manganeso sintetizados por autocombustión y coprecipitación y su empleo en la oxidación del 2-propanol

Castaño

Molina

Moreno

2015

Rev. Acad. Colomb. Cienc. Ex. Fis. Nat.

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ResumenSe sintetizaron óxidos mixtos de manganeso a través de las metodologías de autocombustión y coprecipitación manteniendo constantes las relaciones Mn 2+ /Mg 2+ =1 y M 2+ /M 3+ =3, las cuales son características de los óxidos obtenidos a través de la descomposición térmica de precursores del tipo de la hidrotalcita. Los catalizadores se caracterizaron mediante las técnicas de fluorescencia de rayos X (FRX), difracción de rayos X (DRX), microscopía electrónica de barrido (SEM), adsorción de N 2 , reducción a temperatura programada y se evaluaron en la oxidación catalítica del 2-propanol. Los resultados evidenciaron que el empleo de la autocombustión como método de síntesis permite generar óxidos con propiedades estructurales, texturales, de reducción-oxidación (redox) y catalíticas similares a las obtenidas para el óxido preparado a través del precursor tipo hidrotalcita. El desempeño catalítico de los óxidos mixtos se asoció directamente con sus propiedades redox. El óxido de manganeso obtenido por autocombustión se depositó sobre monolitos metálicos de FeCrAlloy y se evaluó el efecto de la adherencia de la fase activa por medio del recubrimiento previo de los materiales con alúmina coloidal. La oxidación del 2-propanol sobre el monolito evidenció que no hay pérdida de actividad cuando el catalizador está sobre un material estructurado.Palabras clave: hidrotalcita, autocombustión, coprecipitación, monolito, COV. Self-combustion and Co-precipitation manganese catalysts and their use in the oxidation of 2-propanol AbstractManganese mixed oxides were synthesized by self-combustion and co-precipitation, maintaining constant the relationship Mn 2 + / Mg 2 + = 1 and M 2 + / M 3 + = 3, which are characteristic of the oxides obtained by thermal decomposition of hydrotalcite-like precursors. The catalysts were characterized using X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), N 2 adsorption, and temperature-programmed reduction, and they were evaluated in the catalytic oxidation of 2 -propanol. The results showed that the use of such self-combustion synthesis method allows generating oxides with structural, textural, redox and catalytic properties similar to those obtained for the oxide prepared via a hydrotalcite-like precursor. The catalytic performance of mixed oxides was directly related to their redox properties. We evaluated the manganese oxide obtained by self-combustion deposited on Fecralloy metal monoliths, as well as the effect of the adhesion of the active phase of the precoat materials using colloidal alumina. The oxidation of 2-propanol over the monolith showed that there is no loss of activity when a catalyst is on a structured material.

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“…This indicates that these transition metal cations have isomorphously replaced Mg 2+ or Al 3+ in the HTLC structure. On the other hand, the values of parameter c, which is related to the layer thickness (brucite-like sheet plus an interlayer), probably reflect the influence of various factors such as the amount of interlayer water, the size of the interlayer anion and of M 2+ -M 3+ cations, and the strength of electrostatic attractive forces between layer and interlayer [27,28]. As to the crystallite size, estimated using Scherrer equation considering the line broadening associated to (0 0 3) basal reflection, the results in Table 1 confirm the lower crystallite size of sample Cr-HT which can be related to the lower crystallization rate of this sample.…”

Section: Physicochemical Characterizationmentioning

confidence: 99%

Influence of the Incorporation of Transition Metals on the Basicity of Mg,Al-Mixed Oxides and on Their Catalytic Properties for Transesterification of Vegetable Oils

Veiga

Sousa

Polato

et al. 2013

Journal of Catalysts

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The transesterification of vegetable oils produces fatty acid methyl esters (biodiesel). Biodiesel is a nonpolluting alternative fuel produced from renewable resources whose chemical and physical properties closely resemble those of the petroleum diesel fuel and does not contribute to the greenhouse effect. The use of solid catalysts makes biodiesel production processes environmentally friendly. In this work, Mg,Al-mixed oxides derived from Mg,Al-hydrotalcite-like compound with an M 3+ /(M 2+ + M 3+ ) molar ratio of 0.25, in which Mg or Al was partially replaced by Co 2+ , Cu 2+ , Cr 3+ , or Fe 3+ , were prepared, characterized, and evaluated as catalysts for the transesterification of soybean oil with methanol. The results have indicated that the incorporation of transition metal influenced both textural and base properties. All the evaluated catalysts were active for the studied reaction. The catalytic activity followed the order Cr-MO < Co-MO < Cu-MO < Fe-MO < MO and could be explained by mesoporous volume.

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Effect of manganese substitution on the physicochemical properties and catalytic toluene oxidation activities of Mg–Al layered double hydroxides

Cited by 205 publications

References 32 publications

The improved reactivity of manganese catalysts by Ag in catalytic oxidation of toluene

The improved reactivity of manganese catalysts by Ag in catalytic oxidation of toluene

Catalizadores de manganeso sintetizados por autocombustión y coprecipitación y su empleo en la oxidación del 2-propanol

Influence of the Incorporation of Transition Metals on the Basicity of Mg,Al-Mixed Oxides and on Their Catalytic Properties for Transesterification of Vegetable Oils

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