Study of the interaction between hydrogen and the MoO 3-ZrO 2 catalyst

Nurun Najwa Ruslan, Sugeng Triwahyono, Aishah Abdul Jalil, Timmiati Sharifah Najiha, Nur Hazirah Rozali Annuar

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

The interaction of molecular hydrogen with the surface of MoO 3-ZrO 2 was observed using infrared IR and electron spin resonance (ESR) spectroscopy, and the hydrogen adsorption was quantitatively evaluated in the temperature range of 323-573 K. The hydrogen adsorbed IR results confirmed the formation of a new broad band in the range of 3700-3400 cm -1, which corresponds to hydrogen-bonded OH groups. A decrease in the ESR signals indicated the formation of electrons that have been trapped by the electron-deficient metal cations and/or oxygen radicals. The hydrogen adsorbed IR and ESR results suggested that the protons and electrons were formed on the surface of MoO 3-ZrO 2 from molecular hydrogen enhancing the isomerization of n-heptane. A quantitative study of the hydrogen adsorption showed that the rate of hydrogen uptake was high for the first few minutes at 473 K and above, and the rate reached an equilibrium value within 10 h. At 423 K, different features of the hydrogen adsorption were observed on MoO 3-ZrO 2, where the hydrogen uptake increased slowly with time and did not reach equilibrium after 10 h. The rate of hydrogen adsorption increased slightly at 373 K and below. Hydrogen adsorption on MoO 3-ZrO 2 involves two successive steps. The first step involves hydrogen dissociation on a specific site on the MoO 3- ZrO 2 catalyst to form hydrogen atoms, and the second step involves the surface diffusion of the hydrogen atoms on the MoO 3-ZrO 2 surface. Then the hydrogen atom becomes a proton by donating an electron to an adjacent Lewis acid site. The rate-controlling step involves the surface diffusion of hydrogen atoms and has an activation energy of 62.8 kJ/mol. A comparison of the hydrogen adsorption on SO 4 2--ZrO 2, WO 3-ZrO 2 and MoO 3-ZrO 2 catalysts is discussed.

Original languageEnglish
Pages (from-to)176-182
Number of pages7
JournalApplied Catalysis A: General
Volume413-414
DOIs
Publication statusPublished - 31 Jan 2012
Externally publishedYes

Fingerprint

Hydrogen
Catalysts
Adsorption
Atoms
Surface diffusion
Electrons
Paramagnetic resonance
Protons
Electron spin resonance spectroscopy
Lewis Acids
Heptane
Isomerization
Cations
Reactive Oxygen Species
Activation energy

Keywords

  • Electron
  • MoO -ZrO
  • n-Heptane isomerization
  • Proton
  • Surface diffusion

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology

Cite this

Study of the interaction between hydrogen and the MoO 3-ZrO 2 catalyst. / Ruslan, Nurun Najwa; Triwahyono, Sugeng; Jalil, Aishah Abdul; Sharifah Najiha, Timmiati; Annuar, Nur Hazirah Rozali.

In: Applied Catalysis A: General, Vol. 413-414, 31.01.2012, p. 176-182.

Research output: Contribution to journalArticle

Ruslan, Nurun Najwa ; Triwahyono, Sugeng ; Jalil, Aishah Abdul ; Sharifah Najiha, Timmiati ; Annuar, Nur Hazirah Rozali. / Study of the interaction between hydrogen and the MoO 3-ZrO 2 catalyst. In: Applied Catalysis A: General. 2012 ; Vol. 413-414. pp. 176-182.
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AB - The interaction of molecular hydrogen with the surface of MoO 3-ZrO 2 was observed using infrared IR and electron spin resonance (ESR) spectroscopy, and the hydrogen adsorption was quantitatively evaluated in the temperature range of 323-573 K. The hydrogen adsorbed IR results confirmed the formation of a new broad band in the range of 3700-3400 cm -1, which corresponds to hydrogen-bonded OH groups. A decrease in the ESR signals indicated the formation of electrons that have been trapped by the electron-deficient metal cations and/or oxygen radicals. The hydrogen adsorbed IR and ESR results suggested that the protons and electrons were formed on the surface of MoO 3-ZrO 2 from molecular hydrogen enhancing the isomerization of n-heptane. A quantitative study of the hydrogen adsorption showed that the rate of hydrogen uptake was high for the first few minutes at 473 K and above, and the rate reached an equilibrium value within 10 h. At 423 K, different features of the hydrogen adsorption were observed on MoO 3-ZrO 2, where the hydrogen uptake increased slowly with time and did not reach equilibrium after 10 h. The rate of hydrogen adsorption increased slightly at 373 K and below. Hydrogen adsorption on MoO 3-ZrO 2 involves two successive steps. The first step involves hydrogen dissociation on a specific site on the MoO 3- ZrO 2 catalyst to form hydrogen atoms, and the second step involves the surface diffusion of the hydrogen atoms on the MoO 3-ZrO 2 surface. Then the hydrogen atom becomes a proton by donating an electron to an adjacent Lewis acid site. The rate-controlling step involves the surface diffusion of hydrogen atoms and has an activation energy of 62.8 kJ/mol. A comparison of the hydrogen adsorption on SO 4 2--ZrO 2, WO 3-ZrO 2 and MoO 3-ZrO 2 catalysts is discussed.

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