Kinetics, in situ X-ray diffraction and environmental scanning electron microscopy of activated charcoal gasification catalyzed by vanadium oxide, molybdenum oxide and their eutectic alloy

I. M. Fonseca, C. Palma, M. Klimkiewicz, S. Eser

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Abstract

Mechanisms of carbon oxidation catalyzed by vanadium pentaoxide (V2O5) and molybdenum trioxide (MoO3) have been a subject of controversy. Two complementary in situ techniques, X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM), were used in this work to study the gasification of an activated charcoal catalyzed by the two metal oxides, their eutectic alloy and the binary mixture with the eutectic composition. Gasification experiments were carried out at relatively low temperatures (300-650°C) in an XRD cell (1 atm) and ESEM (2.2 Torr) to monitor phase transformations and morphological changes of oxide catalysts, respectively. The experimental results showed that MoO3 and V2O5 particles in contact with active carbon surfaces are reduced to oxides with lower oxidation states, e.g. MoO2 and V6O13, respectively. The reduction of MoO3 to MoO2 on the carbon surface prevents the sublimation of MoO3 which takes place readily on a quartz surface under the same conditions. The formation of V6O13, on the other hand, causes more extensive spreading of the catalyst on carbon surfaces, since V6O13 has a lower melting point than V2O5. Based on the XRD and ESEM observations, it is clear that phase transformations of metal oxides during gasification depend on their interactions with carbon surfaces. The phase transformations of the metal oxides, play, in turn, a significant role in carbon gasification, as evident from the kinetic data obtained for the catalytic gasification of the activated charcoal sample. The synergy observed between the components of the eutectic mixture is discussed, comparing the XRD and ESEM observations.

Original languageEnglish
Pages (from-to)861-868
Number of pages8
JournalCarbon
Volume36
Issue number7-8
DOIs
Publication statusPublished - 1998

Fingerprint

Molybdenum oxide
Vanadium
Charcoal
Gasification
Activated carbon
Eutectics
Carbon
Oxides
X ray diffraction
Scanning electron microscopy
Kinetics
Phase transitions
Metals
Oxidation
Catalysts
Quartz
Sublimation
Binary mixtures
Molybdenum
Melting point

Keywords

  • A. Carbon
  • B. gasification
  • C. scanning electron microscopy (SEM)
  • C. X-ray diffraction
  • D. catalytic properties

Cite this

@article{00464ac3e9124b20bf9209f0965d9921,
title = "Kinetics, in situ X-ray diffraction and environmental scanning electron microscopy of activated charcoal gasification catalyzed by vanadium oxide, molybdenum oxide and their eutectic alloy",
abstract = "Mechanisms of carbon oxidation catalyzed by vanadium pentaoxide (V2O5) and molybdenum trioxide (MoO3) have been a subject of controversy. Two complementary in situ techniques, X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM), were used in this work to study the gasification of an activated charcoal catalyzed by the two metal oxides, their eutectic alloy and the binary mixture with the eutectic composition. Gasification experiments were carried out at relatively low temperatures (300-650°C) in an XRD cell (1 atm) and ESEM (2.2 Torr) to monitor phase transformations and morphological changes of oxide catalysts, respectively. The experimental results showed that MoO3 and V2O5 particles in contact with active carbon surfaces are reduced to oxides with lower oxidation states, e.g. MoO2 and V6O13, respectively. The reduction of MoO3 to MoO2 on the carbon surface prevents the sublimation of MoO3 which takes place readily on a quartz surface under the same conditions. The formation of V6O13, on the other hand, causes more extensive spreading of the catalyst on carbon surfaces, since V6O13 has a lower melting point than V2O5. Based on the XRD and ESEM observations, it is clear that phase transformations of metal oxides during gasification depend on their interactions with carbon surfaces. The phase transformations of the metal oxides, play, in turn, a significant role in carbon gasification, as evident from the kinetic data obtained for the catalytic gasification of the activated charcoal sample. The synergy observed between the components of the eutectic mixture is discussed, comparing the XRD and ESEM observations.",
keywords = "A. Carbon, B. gasification, C. scanning electron microscopy (SEM), C. X-ray diffraction, D. catalytic properties",
author = "Fonseca, {I. M.} and C. Palma and M. Klimkiewicz and S. Eser",
year = "1998",
doi = "10.1016/S0008-6223(97)00174-7",
language = "English",
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T1 - Kinetics, in situ X-ray diffraction and environmental scanning electron microscopy of activated charcoal gasification catalyzed by vanadium oxide, molybdenum oxide and their eutectic alloy

AU - Fonseca, I. M.

AU - Palma, C.

AU - Klimkiewicz, M.

AU - Eser, S.

PY - 1998

Y1 - 1998

N2 - Mechanisms of carbon oxidation catalyzed by vanadium pentaoxide (V2O5) and molybdenum trioxide (MoO3) have been a subject of controversy. Two complementary in situ techniques, X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM), were used in this work to study the gasification of an activated charcoal catalyzed by the two metal oxides, their eutectic alloy and the binary mixture with the eutectic composition. Gasification experiments were carried out at relatively low temperatures (300-650°C) in an XRD cell (1 atm) and ESEM (2.2 Torr) to monitor phase transformations and morphological changes of oxide catalysts, respectively. The experimental results showed that MoO3 and V2O5 particles in contact with active carbon surfaces are reduced to oxides with lower oxidation states, e.g. MoO2 and V6O13, respectively. The reduction of MoO3 to MoO2 on the carbon surface prevents the sublimation of MoO3 which takes place readily on a quartz surface under the same conditions. The formation of V6O13, on the other hand, causes more extensive spreading of the catalyst on carbon surfaces, since V6O13 has a lower melting point than V2O5. Based on the XRD and ESEM observations, it is clear that phase transformations of metal oxides during gasification depend on their interactions with carbon surfaces. The phase transformations of the metal oxides, play, in turn, a significant role in carbon gasification, as evident from the kinetic data obtained for the catalytic gasification of the activated charcoal sample. The synergy observed between the components of the eutectic mixture is discussed, comparing the XRD and ESEM observations.

AB - Mechanisms of carbon oxidation catalyzed by vanadium pentaoxide (V2O5) and molybdenum trioxide (MoO3) have been a subject of controversy. Two complementary in situ techniques, X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM), were used in this work to study the gasification of an activated charcoal catalyzed by the two metal oxides, their eutectic alloy and the binary mixture with the eutectic composition. Gasification experiments were carried out at relatively low temperatures (300-650°C) in an XRD cell (1 atm) and ESEM (2.2 Torr) to monitor phase transformations and morphological changes of oxide catalysts, respectively. The experimental results showed that MoO3 and V2O5 particles in contact with active carbon surfaces are reduced to oxides with lower oxidation states, e.g. MoO2 and V6O13, respectively. The reduction of MoO3 to MoO2 on the carbon surface prevents the sublimation of MoO3 which takes place readily on a quartz surface under the same conditions. The formation of V6O13, on the other hand, causes more extensive spreading of the catalyst on carbon surfaces, since V6O13 has a lower melting point than V2O5. Based on the XRD and ESEM observations, it is clear that phase transformations of metal oxides during gasification depend on their interactions with carbon surfaces. The phase transformations of the metal oxides, play, in turn, a significant role in carbon gasification, as evident from the kinetic data obtained for the catalytic gasification of the activated charcoal sample. The synergy observed between the components of the eutectic mixture is discussed, comparing the XRD and ESEM observations.

KW - A. Carbon

KW - B. gasification

KW - C. scanning electron microscopy (SEM)

KW - C. X-ray diffraction

KW - D. catalytic properties

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EP - 868

JO - Carbon

JF - Carbon

SN - 0008-6223

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