FTIR study of adsorption of CO, NO and C2H4 and reaction of CO+H-2 on the well-dispersed FeOx/gamma-Al2O3 and FeOx/TiO2(a) catalysts

Adsorption of CO, NO and C2H4 and reaction of CO + H-2 on the well-dispersed FeOx/TiO2(a) and FeOx/gamma-Al2O3 catalysts were studied combined with the pulse adsorption and temperature programmed desorption of NO. The results indicated that the adsorption properties on the well-dispersed FeOx are different from those on the bulk ferric oxide. For CO adsorption, the differences in the formation of surface CO complex and surface carbonates were observed. For NO adsorption, the types of the adsorbed NO species on FeOx/gamma-Al2O3 are different from those on the FeOx/TiO2(a) catalyst. The local electronic density of the well-dispersed Fe3+ is increased which enhanced the back donation of d electrons in the Fe-N bonding. The formation of NO3-(NO2-) complex on FeOx/gamma-Al2O3 is also different from that on FeOx/TiO2(a). For C2H4 adsorption, no pi bonded C2H4 species developed on the well-dispersed FeOx although it had been found on the bulk alpha-Fe2O3. The weakly adsorbed C2H4 species on the well-dispersed FeOx did not transform either at room temperature or at elevated temperature (up to 423 K). Surface carbonates are the major products while formate or methoxy species rarely formed on the FeOx/TiO2(a) during the CO + H-2 reaction. Small amount of the nondissociative CO complex may be developed in syngas. The alternations in the adsorption behaviors must be connected with the fact that the structural environment and the electronic property for the adsorption site are somewhat changed because of the various dispersion state and the support effect.