摘要
应用XRD及BET方法研究了MoO3-Fe2O3,MoO3-V2O5,MoO3-TiO2(锐钛矿),MoO3-WO3和MoO3-ZrO2五种二元过渡金属氧化物界面上的相互作用及非晶相自发分散.这些二元氧化物均含有0～100%之间的十个不同掺杂配比的MoO3,经干混和适宜温度下焙烧而得.XRD晶相定量分析及外推法证明,每种组分氧化物都在界面上自发分散为非晶相,并具有各自的分散阈值.当配比大于分散阈值时,各组分氧化物焙烧后的剩余晶相量与加入晶相量之间为线性关系,其中MoO3和ZrO3的斜率显著小于1.BET测定证明,所有试样的比表面积(3.71～11.25m2/g)较常见载体如SiO2等小得多.MoO3在五种二元氧化物界面的分散阈值各不相同(0.33～1.43 g/100m2),远大于唐有祺等人根据O2-密置模型计算得的在高比表面载体上的单层饱和容量(0.117g/100m2).这预示着界面上可能存在非单层分散及表面化学反应,XRD晶相分析及后续文章中FT-IR等表征手段证实了此点.
The interaction and non-crystalline spontaneous dispersion at the interface of five transition metal binary oxide systems were studied by XRD and BET techniques. These systems, namely, MoO3-Fe2O3, MoO3-V2O5, MoO3-TiO2 (anatase), MoO3-WO3 and MoO3-ZrO2 containing 0~100wt% MoO3 were obtained by dry mixing and grinding up, then calcining at appropriate temperatures below melting points of the component oxides. XRD quantitative analysis and extrapolation indicated each component oxide disperses spontaneously to form a non - crystalline phase at interface and has a dispersed threshold value(maximum dispersion capacity). If the added component oxide exceed its threshold value, the relation beteen residual crystalline amount after calcining and added crystalline amount shows linearity, but the slopes are not the same for the different component oxides, the slopes of MoO3 and WO3 being obviously less than 1. These slopes are called 'crystalline residual ratio' for describing and explaining why the slopes are less than 1. BET measurements indicated the specific surface area of all samples are much smaller (3.71-11.25 m2/g) than that of the supports (γ-Al2O3, SiO2 and TiO2 gel etc.). The MoO3dispersed threshold values (0.33-1.43g/100m2) determined by XRD and BET in the present paper are far greater than the MoO3monolayer dispersion capacity (0.117g/100m2) calculated from TANG's O2- colse-packed monolayer dispersion model and also larger thn the MoO3 monolayer dispersion capacity (0.169 g/100m2) calculated from the spherical octahedron model suggested in our ensuring paper. Such large dispersed threshold values over the much smaller specific surface area values signifies the possibility of existence of non ?monolayer dispersion and surface chemical reaction at the interface.
出处
《黑龙江大学自然科学学报》
CAS
2002年第2期81-86,共6页
Journal of Natural Science of Heilongjiang University
基金
国家自然科学基金资助项目(2860018)
关键词
二元过渡金属氧化物
界面结构
非晶相分散
双边分散阈值
transiton metal binary oxides
interfacial dispersion structure
non-crystalline dispersion
both side dispersed threshold values
