【摘要】 测定了MoO₃/γ-Al₂O₃、MoO₃/TiO₂、MoO₃/SiO₂的激光Raman谱。通过MoO₃/γ-Al₂O₃、MoO₃/TiO₂在吡啶吸附前后、氨水提取前后的谱图对比说明,单层分散的MoO₃,即特征峰为～950cm^-1的“二维聚钼酸”中钼的配位状态不是单一的。其中一种表面含钼物种（Mo-1）不吸附吡啶,不溶于氨水,不显示较强的表面酸性;另一种表面含钼物种（Mo-2）可吸附吡啶,溶于氨水,与催化剂的表面酸位密切相关.我们认为Mo-1为四面体配位的钼;Mo-2为八面体配位的钼。MoO₃/SiO₂中的MoO₃能100％被氨水溶去,其酸位数与表面Mo⁶⁺数之比接近1,是由其中Mo-2的比例较高,载体与活性组分之间的相互作用较弱这两个因素所造成的。更多还原

【Abstract】 The Laser Raman Spectra of MoO₃/γ-Al₂O₃, MoO₃/TiO₂, and MoO₃/SiO₂ have been measured. The spectra of MoO₃/γ-Al₂O₃ and MoO₃/TiO₂ were compared with those after adsorption of pyridine and with those after treatment with aqueous ammoniasolution. It can be seen that coordination states of Mo in monolayer dispersed MoO₃ (i.e. the twodimensional polymeric surface molybdenum species with its typical bond at around 950 cm^-1) are not the same. One kind of the surface molybdtenum species Mo-1 can not adsorb pyridine, and is insoluble in aqueous ammonia solution, which means that it is not the acidic site. Whereas the other kind of surface molybdenum species Mo-2 can adsorb pyridine, and is soluble in aqueous ammonia solution. So, this species is closely related with the surface acidity of the catalysis. It has been supposed that Mo-1 is tetrahedrally coordinated surface species, and Mo-2 is octahedrally coordinated species. The fraction of Mo-2 in MoO₃/SiO₂ is larger than that in MoO₃/γ-Al₂O₃, and the interaction between MoO₃ and support SiO₂ is weaker than that in MoO₃/γ-Al₂O₃, so that all the molybdena in MoO₃/SiO₂ is soluble and the ratio between acidic sites and surface Mo⁶⁺ approaches unity.更多还原