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

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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