通过固相热反应,以十种不同的配比和不同的焙烧制度,在MoO3中分别掺杂Fe2O3、V2O5、TiO2(锐钛矿型)、WO3和ZrO2,制得五种二元氧化物的系列试样.应用XRD、BET、FT-IR、DSC、半导体气敏特性和催化反应探针等表征技术,较系统地研究了这些组分氧化物形成二元氧化物时界面的非晶相分散结构及催化性能,并提出了相应的亚单层的非晶相分散模型.本文首先报道应用XRD,FT-IR和BET表征界面的非晶相分散.研究结果发现,各个组分氧化物的表面大小不同,但每一对组分氧化物在相互掺杂时,在界面上发生了组分氧化物的亚单分子层(meta-monolayer)的非晶相分散以及某些表面化学反应,前者的非晶相含量具有本征性的分散阈值,后者则生成新的化学物种.根据BET比表面积,求算了各组分氧化物在不同二元氧化物中每100m2的不同的非晶相分散阈值.XRD晶相定量分析和FT-IR差谱法(the differential spectra method)联合证明了非晶相新物种的存在,首次发现非晶相新物种的IR特征吸收峰与分子键价结构的关联.
The interaction and non-crystalline spontaneous dispersion at the interface of five systems of transition metal
binary oxide, namely, TiO2(anatase)-MoO3, MoO3-V2O5, Fe2O3-MoO3, WO3-MoO3 and ZrO2-MoO3 containing 0～100wt% MoO3 respectively,
were characterized by XRD, BET, FT-IR. The five systems were prepared by dry mixing and grinding up at room temperature, and then calcining at appropriate
temperatures below melting point of two component oxides(500℃/5h). XRD quantitative analysis and extrapolation of crystal phase content indicate
that each component oxide disperses spontaneously to form a non-crystalline phase at interface, and has a dispersed threshold value (the maximum dispersion
capacity). BET measurements show the specific surface area of all samples are much smaller(3.71～11.3m2/g) than that of the supports such as γ-Al2O3 SiO2 and TiO2 gel etc. The dispersed threshold
values of MoO2 (0.33～1.43g·10-2cm-2 determined by XRD and BET in the present paper are far greater than the monolayer dispersion capacity of MoO3
(0.117g·10-2cm-2) calculated from TANG’s model of O2- close-packed monolayer dispersion and also larger than MoO3 monolayer dispersion capacity(0.169g·10-2cm-2)
calculated from the spherical octahedron model suggested in our ensuing paper. Such larger dispersed threshold value in the much smaller specific surface area
signifies non-monolayer dispersion and/or chemical reaction at interface. By means of FT-IR spectra and its differential spectra, the new species of
non-crystalline phase at interface and its characteristic absorption bands are discovered for the first time, and these bands are correlated to molecular
structure, such as IR characteristic absorption bands of non-crystalline phase MoO3 appear at 960 and 826～828 cm-1.
参考文献
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