摘要
对Ｎａ２ＭｏＯ４·２Ｈ２Ｏ，ＭｏＯ３，（ＮＨ４）６Ｍｏ７Ｏ２４·４Ｈ２Ｏ等结构典型的含相化合物及氧化态Ｋ—ＭｏＯ３／γ－Ａｌ２Ｏ３催化剂样品进行了ＥＸＡＦＳ测试，并以Ｎａ２ＭｏＯ４·２Ｈ２Ｏ为标样进行多层拟合计算，以研究各样品相组分的配位结构。ＭｏＯ３和钼酸铵的配位状态复杂，无序度较高，富里埃变换谱上对应Ｍｏ—Ｏ配位的峰相互迭加后峰形宽化、不对称，单层拟合误差较大，多层拟合所得Ｍｏ－Ｏ配位结构参数与实际值较好地符合；氧化态催化剂样品中，不含钾样品的Ｍｏ－Ｏ键长较短，钼组分主要以高分散的ＭｏＯ３微粒形式存在，含钾样品的Ｍｏ—Ｏ键长较长，钼组分主要以多钼酸盐的形式存在。
Abstract EXAFS measurements were performed on Mo compounds of Na2MoO4. 2H2O, MoO3,(NH4)6Mo7O24. 4H2O and the oxidic K-MoO3/γ-Al2O3 catalyst samples with different K contents.Na2MoO4. 2H2O was used as reference compound in the process of EXAFS fit. For the oxidic Mo compounds of MoO3 or (NH4)6Mo7O24. 4H2O which have irregular structures, Mo-O coordinations are complex with different distances. By two or three layer fit, the EXAFS analysis shows reasonable results compared to crystallographic parameters.For the oxidic sample, Since several different Mo species are formed on the surface, the Mo-O coordination becomes more complex. By two layer fit, EXAFS analysis shows that for the sample without containing potassium, part of Mo ealsts as MoO3 crystullite with a short range order; for the samples with K/Mo=0. 8 and K/Mo=1. 5, Mo exists dominately as heptamolybdate ion (Mo7O), these are in accord with the results from XRD and LRS measurements
基金
国家自然科学基金
