Acta Phys. -Chim. Sin. ›› 1994, Vol. 10 ›› Issue (02): 164-167.doi: 10.3866/PKU.WHXB19940215

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Identification of γ-Fe2O3 in Ferrite-ferric Oxide Catalysts Using Second Derivative IR Spectra

Yang Li-Ying, Chen Shu, Xu Wen-Qing, Li Guo-Ying, YIN  Yuan-Gen   

  1. Department of Chemical Engineering, Beijing Institute of Chemical Fibre Technology, Beijing 100029
  • Received:1992-06-08 Revised:1992-12-12 Published:1994-02-15
  • Contact: Chen Shu


It is well known that γ-Fe_2O_3 is a very active and selective catalyst for okidative dehydrogenation ofbutene to butadiene. It is hard, however, to distingulsh between ferrite spinels and therefore to identify its existence in ferrite-ferric oxide catalysts using XRD. On the IR spectra γ-Fe_2O_3 has characteristic bands in the range of 600~800 cm~(-1), which do not exist for α-Fe_2O_3, Fe3O4, ZnFe_2O_4 and MgFe_2O_4. But these bands are too weak to deterAnne for the small amount of γ-Fe_2O_3, e g. less than 30% (mass fraction), in catalysts.
Usually using second derivative IR spectra can increase the analytical sensitivity substantially. The mechanical mixtures of γ-Fe_2O_3 and MgFe_2O_4 in different ratio were prepared and their second derivative IR spectra were taken. It was found that the bands 730 and 695 cm~(-1) were characteristic of γ-Fe_2O_3 and their intensities increased with the content of γ-Fe_2O_3 in the mixtures. A staight line with R=0.994 can describe the relation between γ-Fe_2O_3 content and the peak area of band 695 cm~(-1). The lowest detectable content of γ-Fe_2O_3 is about 1% (mass fraction). The existence of γ-Fe_2O_3 in the used B-02 comercial catalyst was identified by this method.

Key words: Second derivative IR spectrm, γ-Fe2O3, Ferrite, Spinel, Oxidative dehydrogenation of butenes