Redox Property of Transition Metal Oxides in Catalytic Oxidation

TPR/TPO 실험기법을 이용한 전이금속산화물의 산화-환원 특성 연구

  • Kim, Young-Ho (Department of Chemical Engineering, Kunsan National University) ;
  • Lee, Ho-In (School of Chemical Engineering, Seoul National University)
  • 김영호 (군산대학교 화학공학과) ;
  • 이호인 (서울대학교 응용화학부)
  • Received : 1999.08.04
  • Accepted : 1999.11.27
  • Published : 1999.12.10

Abstract

The redox property of oxide materials of the 3rd period transition metals(Cr~Zn), V, Mo, and W was studied with temperature-programmed reduction/temperature-programmed oxidation(TPR/TPO) experiment. The peak temperatures of TPO spectra were equal to or lower than those of TPR spectra. And the peak shapes of TPO spectra were broader than those of TPR ones. The activation energies of TPR/TPO for the oxides of the 3rd period transition metals showed in the range of 33~149 kJ/mol, while for the oxides of V, Mo, and W, they showed relatively higher values. The change of activation energies of TPR/TPO with various metal oxides showed a similar trend to the change of their metal-oxygen bond strengths. The change of activation energies of o-xylene oxidation for various metal oxides was proportional to the difference (${\Delta}E_a$) between the activation energy of TPR and that of TPO. From these results, we concluded that the oxidation of o-xylene over various metal oxide catalysts follows the Mars-van Krevelen mechanism including the surface reduction-oxidation of the metal oxide itself.

Keywords

temperature-programmed reduction(TPR);temperature-programmed oxidation(TPO);transition metal oxides;o-xylene oxidation

Acknowledgement

Supported by : 한국과학재단

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