Acetone Reactions over the Surfaces of Polycrystalline UO2: A Kinetic and Spectroscopic Study

Richard King, Hicham Idriss

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

The reaction of acetone is studied on the surfaces of polycrystalline UO2, prepared by hydrogen reduction of U3O8 at 770 K. The stud), is conducted by in situ Fourier transform infrared (FTIR) and temperature-programmed desorption (TPD). Acetone adsorption does not fit the simple Langmuir model, and adsorbate-adsorbate interactions are found to be significant. Acetone adsorbs molecularly on UO2 as evidenced by the nu C=O of the eta(1)(O) mode at 1686 cm(-1). Part of acetone is reduced to the isopropoxide species ((CH3)(2)HC-O-U4+) Upon heating (nu(CC), rho(CH3) at 1167 cm(-1) and nu(CO), rho(CH3) at 980 cm(-1)), and upon further heating, acetates (CH3COO(a), (a) for adsorbed) are observed. Detailed TPD studies indicated that the main reaction of acetone on UO2 is the deoxygenation to propene, driven by the oxophilic nature Of UO2. Other reactions were also observed to a lesser extent, and these included reductive coupling to 2,3-dimethylbutene and condensation to mesityl oxide. An attempt to extract kinetic parameters from TPD data was conducted. Three models were studied: variation of heating rate, leading edge analysis (Habenschaden-Kuppers method), and complete analysis. The complete analysis provided the most plausible results, in particular, at low coverage. With this method, at nearly zero coverage the activation energy, E-d, for desorption was found to be close to 140 kJ/mol with a prefactor of 10(13) s(-1). E-d dropped sharply with increasing coverage, theta, to ca. 35 kJ/mol at theta = 0.15 with a prefactor of 10(11) s(-1). The activation energy for the desorption of acetone on UO2(111) single crystals, at saturation coverage, was previously found to be equal to 65 kJ/mol using the leading edge analysis.

Original languageEnglish
Pages (from-to)4543-4555
Number of pages13
JournalLangmuir
Volume25
Issue number8
Early online date3 Mar 2009
DOIs
Publication statusPublished - 2009

Keywords

  • temperature-programmed desorption
  • uranium oxide catalysts
  • thermal-desorption
  • furan formation
  • single-crystal
  • FT-IR
  • ditungsten hexaalkoxides
  • heterogeneous catalysis
  • selective oxidation
  • organic-compounds

Cite this

Acetone Reactions over the Surfaces of Polycrystalline UO2 : A Kinetic and Spectroscopic Study. / King, Richard; Idriss, Hicham.

In: Langmuir, Vol. 25, No. 8, 2009, p. 4543-4555.

Research output: Contribution to journalArticle

King, Richard ; Idriss, Hicham. / Acetone Reactions over the Surfaces of Polycrystalline UO2 : A Kinetic and Spectroscopic Study. In: Langmuir. 2009 ; Vol. 25, No. 8. pp. 4543-4555.
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abstract = "The reaction of acetone is studied on the surfaces of polycrystalline UO2, prepared by hydrogen reduction of U3O8 at 770 K. The stud), is conducted by in situ Fourier transform infrared (FTIR) and temperature-programmed desorption (TPD). Acetone adsorption does not fit the simple Langmuir model, and adsorbate-adsorbate interactions are found to be significant. Acetone adsorbs molecularly on UO2 as evidenced by the nu C=O of the eta(1)(O) mode at 1686 cm(-1). Part of acetone is reduced to the isopropoxide species ((CH3)(2)HC-O-U4+) Upon heating (nu(CC), rho(CH3) at 1167 cm(-1) and nu(CO), rho(CH3) at 980 cm(-1)), and upon further heating, acetates (CH3COO(a), (a) for adsorbed) are observed. Detailed TPD studies indicated that the main reaction of acetone on UO2 is the deoxygenation to propene, driven by the oxophilic nature Of UO2. Other reactions were also observed to a lesser extent, and these included reductive coupling to 2,3-dimethylbutene and condensation to mesityl oxide. An attempt to extract kinetic parameters from TPD data was conducted. Three models were studied: variation of heating rate, leading edge analysis (Habenschaden-Kuppers method), and complete analysis. The complete analysis provided the most plausible results, in particular, at low coverage. With this method, at nearly zero coverage the activation energy, E-d, for desorption was found to be close to 140 kJ/mol with a prefactor of 10(13) s(-1). E-d dropped sharply with increasing coverage, theta, to ca. 35 kJ/mol at theta = 0.15 with a prefactor of 10(11) s(-1). The activation energy for the desorption of acetone on UO2(111) single crystals, at saturation coverage, was previously found to be equal to 65 kJ/mol using the leading edge analysis.",
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T1 - Acetone Reactions over the Surfaces of Polycrystalline UO2

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AU - King, Richard

AU - Idriss, Hicham

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N2 - The reaction of acetone is studied on the surfaces of polycrystalline UO2, prepared by hydrogen reduction of U3O8 at 770 K. The stud), is conducted by in situ Fourier transform infrared (FTIR) and temperature-programmed desorption (TPD). Acetone adsorption does not fit the simple Langmuir model, and adsorbate-adsorbate interactions are found to be significant. Acetone adsorbs molecularly on UO2 as evidenced by the nu C=O of the eta(1)(O) mode at 1686 cm(-1). Part of acetone is reduced to the isopropoxide species ((CH3)(2)HC-O-U4+) Upon heating (nu(CC), rho(CH3) at 1167 cm(-1) and nu(CO), rho(CH3) at 980 cm(-1)), and upon further heating, acetates (CH3COO(a), (a) for adsorbed) are observed. Detailed TPD studies indicated that the main reaction of acetone on UO2 is the deoxygenation to propene, driven by the oxophilic nature Of UO2. Other reactions were also observed to a lesser extent, and these included reductive coupling to 2,3-dimethylbutene and condensation to mesityl oxide. An attempt to extract kinetic parameters from TPD data was conducted. Three models were studied: variation of heating rate, leading edge analysis (Habenschaden-Kuppers method), and complete analysis. The complete analysis provided the most plausible results, in particular, at low coverage. With this method, at nearly zero coverage the activation energy, E-d, for desorption was found to be close to 140 kJ/mol with a prefactor of 10(13) s(-1). E-d dropped sharply with increasing coverage, theta, to ca. 35 kJ/mol at theta = 0.15 with a prefactor of 10(11) s(-1). The activation energy for the desorption of acetone on UO2(111) single crystals, at saturation coverage, was previously found to be equal to 65 kJ/mol using the leading edge analysis.

AB - The reaction of acetone is studied on the surfaces of polycrystalline UO2, prepared by hydrogen reduction of U3O8 at 770 K. The stud), is conducted by in situ Fourier transform infrared (FTIR) and temperature-programmed desorption (TPD). Acetone adsorption does not fit the simple Langmuir model, and adsorbate-adsorbate interactions are found to be significant. Acetone adsorbs molecularly on UO2 as evidenced by the nu C=O of the eta(1)(O) mode at 1686 cm(-1). Part of acetone is reduced to the isopropoxide species ((CH3)(2)HC-O-U4+) Upon heating (nu(CC), rho(CH3) at 1167 cm(-1) and nu(CO), rho(CH3) at 980 cm(-1)), and upon further heating, acetates (CH3COO(a), (a) for adsorbed) are observed. Detailed TPD studies indicated that the main reaction of acetone on UO2 is the deoxygenation to propene, driven by the oxophilic nature Of UO2. Other reactions were also observed to a lesser extent, and these included reductive coupling to 2,3-dimethylbutene and condensation to mesityl oxide. An attempt to extract kinetic parameters from TPD data was conducted. Three models were studied: variation of heating rate, leading edge analysis (Habenschaden-Kuppers method), and complete analysis. The complete analysis provided the most plausible results, in particular, at low coverage. With this method, at nearly zero coverage the activation energy, E-d, for desorption was found to be close to 140 kJ/mol with a prefactor of 10(13) s(-1). E-d dropped sharply with increasing coverage, theta, to ca. 35 kJ/mol at theta = 0.15 with a prefactor of 10(11) s(-1). The activation energy for the desorption of acetone on UO2(111) single crystals, at saturation coverage, was previously found to be equal to 65 kJ/mol using the leading edge analysis.

KW - temperature-programmed desorption

KW - uranium oxide catalysts

KW - thermal-desorption

KW - furan formation

KW - single-crystal

KW - FT-IR

KW - ditungsten hexaalkoxides

KW - heterogeneous catalysis

KW - selective oxidation

KW - organic-compounds

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DO - 10.1021/la803933t

M3 - Article

VL - 25

SP - 4543

EP - 4555

JO - Langmuir

JF - Langmuir

SN - 0743-7463

IS - 8

ER -