RAMAN SPECTROSCOPIC STUDY OF MoO3/TiO2-Al2O3 CATALYST

Raman spectrum was used to characterize the structure of Mo species supported on TiO2-modified Al2O3. For Mo/Al2O3 without TiO2 samples the bands at 325-350 cm(-1) aid 930-940 cm(-1) assigned as tetrahedral MoO2, and the bands at 215 and 959 cm(-1) as octahedral MoO6-6 can be observed at lower MoO3 loading, while Al-2(MoO4)(3) phase and crystalline MoO3 appeared respectively at 370, 1004 cm(-1) and 822,991cm(-1) when the amount of MoO3 was beyond one monolayer dispersion on Al2O3 surface. As for Mo/TiO2-Al2O3 samples, only octahedral MoO6-6 and crystalline MoO3, but no tetrahedral MoO4-2 and Al-2(MoO4)(3) phases had been detected at low or high MoO3 loadings, even calcination temperature of the samples raised to 973 K, which reveals that TiO2 covered on Al2O3 can weaken the interaction between MoO3 and Al2O3 and inhibits the formation of Al-2(MoO4)(3) phase. When a definite amount of CoO added into molybdena samples the bands of crystalline MoO3 disappeared, suggesting that CoO can effectively promote the dispersion of MoO3 on the carrier. The presence of CoMoO4 phase was observed in Al2O3 or TiO2-Al2O, carriers