物理化学学报 >> 1989, Vol. 5 >> Issue (03): 370-376.doi: 10.3866/PKU.WHXB19890323

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MoO3 / Al2O3、MoO3 / TiO2与NiO-MoO3 / TiO2催化剂上活性相还原行为的XPS考察

熊国兴; 谭长青; 王弘立   

  1. 中国科学院大连化学物理研究所
  • 收稿日期:1987-10-21 修回日期:1988-05-16 发布日期:1989-06-15
  • 通讯作者: 熊国兴

STUDY ON REDUCTION BEHAVIOURS OF MOLYBDENA ON MoO3 / Al2O3、MoO3 / TiO2 AND NiO-MoO3 / TiO2 SYSTEMS BY XPS

Xiong Guoxing*; Tan Changqing; Wang Hongli   

  1. Dalian Institute of Chemical Physics; Chinese Academy of Sciences; 129 Street; Dalian; China.
  • Received:1987-10-21 Revised:1988-05-16 Published:1989-06-15
  • Contact: Xiong Guoxing

Abstract: The H_2 reduction behaviours of MoO_3/Al_2O_3, MoO_3/TiO_2 and NiO-MoO_3/TiO_2 samples prepared by impregnation method were studied at various temperatures for different times by XPS technique. The recored XPS spectra of Mo3d from those samples were treated by computer curve fittingprogram to measure the distribution of various molybdenum oxide species with different valence states. The results of computer fitting shows that there areMo(Ⅵ), Mo(Ⅴ)and Mo(Ⅳ) on the all of reduced samples. However, after H_2 reductonin same way, the percentage of low valence species Mo(V) and Mo(IV) on the MoO_3/TiO_2 is much higher than on the MoO_3/Al_2O3 (Fig.2). For example, after H_2 treatment at 500 ℃ for 2 hrs., Mo(IV) species on the surface of MoO_3/TiO_2 sample is about 60% and it is three times higher than what is found on the MoO_3/Al_2O_3 sample. In addition, the reduction of molybdena on TiO_2 support is much easier and faster than on Al_2O_3 support (Fig.3). Addition of NiO further promotes the reduction of molybdena to cause the strting reduction temperature producing Mo(IV) and Mo(V) to be decreased about 100 ℃. and 80% of molyb dena on NiO-MoO_3/TiO_2 support could be reduced to Mo(IV) (Fig.2). A detail discussion about the interaction between molybdena and carries was presented. It was suggested that TiO_2 is certainly involved in the reduction and oxidation process of molybdenum oxide species on the surface of it.