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用X光衍射研究了MoO_3/TiO_2,MoO_3/SiO_2和MoO_3/MgO等体系。结果表明,MoO_3在TiO_2胶表面呈密置单层分散,其最大分散量(阈值)与按密置单层模型计算的0.117克MoO_3/100米~2(即4.9 × 10~(18)Mo原子/米~2)相符。MoO_3在SiO_2胶表面呈单层分散但非密置单层,其分散阈值为 0.032克MoO_3/100米~2(即 1.4 × 10~(18)Mo原子/米~2)。MoO_3与MgO比较容易进行体相反应,在290℃即已有部分MgMoO_4形成,没有只形成表面单层分散的阶段,因此不存在表面分散阈值,还联系载体的酸碱性、化学键性质以及结构上的差异,对MoO_3/γ-Al_2O_3和上述体系进行了讨论和比较。
The structures of MoO 3 / TiO 2, MoO 3 / SiO 2 and MoO 3 / MgO were studied by X-ray diffraction. The results show that the MoO 3 is densely monolayer dispersed on the surface of TiO 2 gel with the maximum dispersion (threshold) of 0.117 g MoO 3/100 m 2 (ie 4.9 × 10 18 Mo atoms / M ~ 2) match. MoO 3 has a monolayer dispersed but non-dense monolayer on the surface of SiO 2 gel with a dispersion threshold of 0.032 g MoO 3/100 m 2 (ie 1.4 × 10 18 Mo atoms / m 2). MoO_3 and MgO are relatively easy to carry out the body phase reaction at 290 ℃ that part of the formation of MgMoO_4, there is no formation of surface monolayer dispersion stage, there is no surface dispersion threshold, but also linked to the carrier acid-base, chemical bond properties and structurally The differences between MoO_3 / γ-Al_2O_3 and the above systems were discussed and compared.