Ruthenium-oxo species with high oxidation performance supported on nano-scale particles prepared by the solvothermal reaction

本研究旨在设计Ru=O基团高度分散在溶剂热反应制备的金属氧化物载体上的Ru物质。该钌料具有特殊的高活性氧化反应。首先，采用CeO_2作为支撑。金属铈在2-甲氧基乙醇中的溶剂热反应制备了平均直径为2nm的超细CeO_2胶体颗粒。将得到的CeO_2胶体溶液用不同的混凝剂进行混凝制备CeO_2粉体。混凝剂（NaOH、NH_4OH、Na_2CO_3、（NH_4）_2CO_3、NaHCO_3）不同，其孔结构也不同。用（NH_4）_2CO_3和NaHCO_3制备的CeO_2粉体具有宏观和介孔，而用NaOH和NH_4OH制备的CeO_2粉体具有较多的微孔。钌能以较好的分散状态被负载在前者的CeO_2上，而不能被负载在后者的微孔中；结果表明，前者对苯甲醇的氧化活性高于后者。比较了以aq. Ce(NO_3)_3为起始原料的普通沉淀法和以溶剂热法合成的CeO_2胶体溶液为起始原料制备的CeO_2样品的性质。溶剂热样品易于还原和再氧化；其表面流动氧含量高于沉淀样品。因此，Ru在溶剂热法CeO_2上的活性远大于沉淀法制备的CeO_2上的活性；表明溶剂热法制备高性能超细金属氧化物颗粒的优越性。考察了其他各种载体，得到了具有Ru=O键的Ru物质。得到Ru的目标载体为ZrO_2、TbO_2和Pr_6O_<11>。然而，他们都没有成功地生产出这种钌。本研究的结论是，钌与CeO_2的结合是产生具有Ru=O键的精细分散的钌的唯一体系。作者期望该催化剂在各种有机反应中具有很高的应用潜力。少

In this work, we aimed at designing Ru species with Ru=O group which is highly dispersed on metal oxide supports prepared by the solvothermal reaction. This Ru species is expected to have peculiar and high activity for oxidation reactions. First, CeO_2 was employed as a support. The solvothermal reaction of Ce metal in 2-methoxy ethanol produced ultra fine CeO_2 colloidal particles whose average diameter was 2nm. The obtained CeO_2 colloidal solution was coagulated by various coagulants to produce CeO_2 powders. Their pore structures varied with the kinds of coagulants (NaOH, NH_4OH, Na_2CO_3, (NH_4)_2CO_3, NaHCO_3). The CeO_2 powders produced by using (NH_4)_2CO_3 and NaHCO_3 had macro and meso pores while those obtained with NaOH and NH_4OH had much micro pores. Ruthenium could be supported on the former CeO_2 in a well dispersed state but could not be supported in the micro-pore of the latter; thus, the former catalysts had higher activity in the oxidation of benzyl alcohol than the … More latter.The natures of the CeO_2 sample prepared by an ordinary precipitation method starting from aq. Ce(NO_3)_3 and the one prepared by starting from CeO_2 colloidal solution synthesized by the solvothermal method were compared. The solvothermal sample could be easily reduced and re-oxidized; it had larger amount of surface mobile oxygen than the precipitation sample. Consequently, the activity of the Ru supported on the solvothermal CeO_2 was much larger than that on the CeO_2 prepared by the precipitation method; indicating the excellence of the solvothermal method to prepare high performance ultra fine metal oxide particles.Various other supports were examined to obtain Ru species with Ru=O bond. The target supports to obtain the Ru species were ZrO_2, TbO_2, and Pr_6O_<11>. However, none of them were successful to produce this kind of Ru species. Conclusion of the present research is that the combination of Ru with CeO_2 is the sole and unique system to produce the finely dispersed Ru species with the Ru=O bond. The author expects the high potential of this catalyst to be used in various organic reactions. Less