在MoO_3／SiO_2及其添加体系上甲烷部分氧化制甲醛的研究

Partial Oxidation of Methane to Formaldehyde over MoO_3/SiO_2 Catalyst and Its Additive Systems

在常压下，以Ｏ２作氧化剂，评价了不同ＭｏＯ３／ＳｉＯ２（２─１５Ｍｏｗｔ％）催化剂对甲烷选择氧化为甲醛的反应性能，发现ＳｉＯ２上担载的活性组分有一个最佳值，对应最佳催化活性．分别考察了添加Ｖ、Ｆｅ、Ｎｉ、Ｃｒ、Ｃｕ氧化物对ＭｏＯ３／ＳｉＯ２催化剂甲烷选择氧化制甲醛的活性和选择性的调变作用．ＭｏＯ３／ＳｉＯ２添加体系使甲烷的转化率都有所提高，但甲醛选择性有不同程度的下降，其中比较好的是ＭｏＯ３·Ｖ２Ｏ５／ＳｉＯ２催化剂，并研究了不同Ｍｏ／（Ｍｏ＋Ｖ）（原子比）对反应活性和选择性的影响，发现Ｖ２Ｏ５添加量有最佳值．采用ＴＰＲ、ＸＲＤ、ＣＯ２─ＴＰＤ等技术对催化剂进行表征并关联反应性能进行了讨论．

The partial oxidation of methane to formaldehyde has been studied on molybdenum catalysts supported on silica of different Mo loading(2-15 wt%Mo ) at one atmosphere,with oxygen as the oxidant. Although all MoO3 catalysts have considerable selectivity for formaldehyde, there is an optimum content on silica which has the best catalytic activity.With MoO3/SiO2 as the main catalyst,to which metal oxides of V,Fe,Ni,Cr and Cu are added respectively, the modifying effects on the partial oxidation of methane to formaldehyde on MoO3/SiO2 catalyst have been investigated. Although the methane conversion increases in all cases, the selectivity of formaldehyde decreases to different extents.MoO3·V2O5/SiO2 is found to be the much better catalyst than MoO3/SiO2.The activity and selectivity of partial oxidation of methane are studied at different atomic ratios of Mo/( Mo+V). There is an optimum V2O5 additive quantity.The techniques of TPR(Temperature programmed reduction), XRD(X-ray diffraction)and CO2-TPD(CO2-Temlperature programmed desorption)have been used to characterize the catalysts,experimental findings are discussed relating to the catalytic activity.