Cr/SiO2 mesoporous catalysts: Effect of hydrothermal treatment and calcination temperature on the structure and catalytic activity in the gas phase dehydration and dehydrogenation of cyclohexanol

Zapata, Pablo Martín Cuesta; Nazzarro, M.; Gonzo, Elio Emilio; Parentis, Mónica Liliana; Bonini, Norberto Alejandro

doi:10.1016/j.cattod.2015.04.038

Cited by 14 publications

(9 citation statements)

References 30 publications

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“…From the above results and those reported in previous papers [25][26][27], we can conclude that Cr 3+ species were the . The spectra were determined after evacuation for 30 min at room temperature only one into the catalyst samples dried at 110 °C, whereas in samples treated at temperatures higher than 110 °C, both Cr 3+ and Cr 6+ species were present.…”

Section: Ftir Study Of 26-lutidine Adsorptionsupporting

confidence: 86%

“…The spectra were determined after evacuation for 30 min at room temperature only one into the catalyst samples dried at 110 °C, whereas in samples treated at temperatures higher than 110 °C, both Cr 3+ and Cr 6+ species were present. Similar results were obtained over Cr-MCM-41 materials on which the relative amount of both species was quantified by XPS [25,26].…”

Section: Ftir Study Of 26-lutidine Adsorptionsupporting

confidence: 76%

“…However, the stability of these metal ions is not enough to avoid leaching into the liquid phase [6,16,20]. Recently, our research group has reported the synthesis of Cr-SiO 2 catalysts by sol-gel technique followed by hydrothermal treatment [25][26][27] up to 220 °C. It was observed a progressive incorporation of Cr 3+ ions in the silica network as the hydrothermal temperature increases from 120 to 220 °C.…”

Section: Introductionmentioning

confidence: 99%

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Amorphous Cr/SiO2 Materials Hydrothermally Treated: Liquid Phase Cyclohexanol Oxidation

et al. 2018

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Amorphous Cr-SiO 2 materials were synthesized by the sol-gel method and hydrothermally treated at temperatures between 150 and 220 °C. These materials were used as catalysts for cyclohexanol oxidation with H 2 O 2 as oxidant and CH 3 CN as a solvent. They were responsible for the decomposition of H 2 O 2 , which triggers, by a free radical mechanism in the homogeneous phase, the oxidation or degradation of the hydrocarbon chain. Metal leaching causes a drop in catalytic activity when the material is recycled. Studies on the hydrothermal treatment effect on the leaching process have demonstrated that the higher the hydrothermal treatment temperature, the higher the metal/support interaction, leading to a diminution of the leaching process. Under mild reaction conditions, and using TBHP as oxidant, leaching was reduced, and improvements were obtained on the selectivity towards the formation of cyclohexanone. The use of these catalysts in the oxidation of verbenol, an allylic alcohol, showed a significant increase in the substrate conversion and in the selectivity to carbonyl derivative formation.

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Section: Ftir Study Of 26-lutidine Adsorptionsupporting

confidence: 86%

Section: Ftir Study Of 26-lutidine Adsorptionsupporting

confidence: 76%

Section: Introductionmentioning

confidence: 99%

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Amorphous Cr/SiO2 Materials Hydrothermally Treated: Liquid Phase Cyclohexanol Oxidation

et al. 2018

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“…Dehydration reactions of alcohols under laboratory conditions are of interest because they represent potential routes to the formation of ethylene, other alkenes, and ethers . As mentioned above, the historical method of using concentrated acids often results in low yields, and many different reagents/conditions to improve alcohol dehydration are described in the literature. − An important application for alcohol dehydration is the deoxygenation of biomass for bioproduct production (including fuels) . Again, many methods for affecting deoxygenation of alcohols and polyols have been described in the literature. − With these considerations, hydrothermal dehydration could find application in a wide range of processes, within the constraints imposed by the reaction mechanisms.…”

Section: Resultsmentioning

confidence: 99%

Kinetics and Mechanisms of Dehydration of Secondary Alcohols Under Hydrothermal Conditions

Bockisch

Lorance

Hartnett

et al. 2018

ACS Earth Space Chem.

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Alcohol dehydration by elimination of water is central to a series of functional group interconversions that have been proposed as a reaction pathway that connects hydrocarbons and carboxylic acids under geochemically relevant hydrothermal conditions such as in sedimentary basins. Hydrothermal dehydration of alcohols is an example of an organic reaction that is quite different from the corresponding chemistry under ambient laboratory conditions. In hydrothermal dehydration, water acts as the solvent and provides the catalyst, and no additional reagents are required. This stands in contrast to the same reaction at ambient conditions, where concentrated strong acids are required. Hydrothermal dehydration is thus of potential interest in the context of green chemistry. We investigated the mechanism of hydrothermal alcohol dehydration for a series of secondary alcohols using studies of kinetics and stereoelectronic effects to establish reaction mechanisms. The E1 elimination mechanism dominates over the corresponding E2 mechanism, with the E2 mechanism being competitive with E1 only for the most favorable stereoelectronically restricted alcohols included in the present study. These results are relevant to understanding the kinetics and product distributions of alcohol dehydration reactions in natural geologic systems and can guide the development of organic chemical reactions that mimic geologic organic reactions under laboratory green chemistry conditions.

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“…Por último, la banda a 962 cm -1 corresponde a vibraciones del enlace Si-OH y el pico a 800 cm -1 se asigna a las vibraciones de estiramiento simétrico de enlaces Si-O-Si [6].…”

Section: Figuraunclassified

Síntesis de sílice mesoestructurada: determinación de las condiciones óptimas de extracción del templato

Serrano¹,

Saracho

Acosta³

et al. 2018

Matéria (Rio J.)

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RESUMENSe sintetizó sílice mesoporosa a través del proceso sol-gel usando tetraetoxisilano (TEOS) como fuente de sílice y bromuro de n-hexadeciltrimetilamonio (CTAB) como agente director de la estructura. La eliminación del surfactante post-síntesis, se realizó mediante dos técnicas: calcinación con incrementos programados de temperatura hasta alcanzar los 550°C y extracción con solventes usando HCl/EtOH como solución extractora y modificando algunas variables experimentales, tales como la concentración del ácido, el volumen de solución extractora, la duración del tratamiento y el solvente empleado para realizar el lavado. Las muestras fueron caracterizadas por adsorción de nitrógeno, espectroscopia de IR y SEM. Tanto la técnica de síntesis empleada como los procedimientos para eliminar el surfactante conducen a un material del tipo MCM-41. Mediante calcinación se obtienen materiales con un área superficial de 1100 m 2 /g mientras que la extracción con HCl/EtOH conduce a disminuciones en el área superficial, atribuibles a la oclusión de los poros con material orgánico. La presencia de surfactante en las muestras fue determinada por FTIR.Palabras clave: Sílice mesoporosa, MCM-41, técnica sol-gel, TEOS, CTAB. ABSTRACTOrdered mesoporous silica was synthesized by the sol-gel process using tetraethoxysilane (TEOS) as silica source and hexadecyltrimethyl ammonium bromide (CTAB) as structure directing agent. Post-synthesis surfactant removal was conducted by two techniques: calcination, with progressive increases in temperature up to 550 ºC and solvent extraction using HCl /EtOH as extracting solution. In the last mentioned technique, a few experimental variables were changed such as the acid concentration, the volume of extracting solution, the reflux time and the solvent employed for washing. The samples were characterized by N 2 adsorption, FTIR spectroscopy and SEM. Both the synthesis technique used and the procedures to remove template lead to MCM-41 type material. Template extraction by calcination results in materials having a surface area of 1100 m 2 /g. On the other hand, extraction with HCl/EtOH leads to decreases in surface area, attributed to occlusion of the pores with organic material. In both cases, monitoring surfactant traces in the samples was performed using FTIR.

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Cr/SiO2 mesoporous catalysts: Effect of hydrothermal treatment and calcination temperature on the structure and catalytic activity in the gas phase dehydration and dehydrogenation of cyclohexanol

Cited by 14 publications

References 30 publications

Amorphous Cr/SiO2 Materials Hydrothermally Treated: Liquid Phase Cyclohexanol Oxidation

Amorphous Cr/SiO2 Materials Hydrothermally Treated: Liquid Phase Cyclohexanol Oxidation

Kinetics and Mechanisms of Dehydration of Secondary Alcohols Under Hydrothermal Conditions

Síntesis de sílice mesoestructurada: determinación de las condiciones óptimas de extracción del templato

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