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首页> 外文期刊>Applied Catalysis, B. Environmental: An International Journal Devoted to Catalytic Science and Its Applications >Synergistic hollow CoMo oxide dual catalysis for tandem oxygen transfer: Preferred aerobic epoxidation of cyclohexene to 1,2-epoxycyclohexane
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Synergistic hollow CoMo oxide dual catalysis for tandem oxygen transfer: Preferred aerobic epoxidation of cyclohexene to 1,2-epoxycyclohexane

机译：串联氧转移的协同空心Como氧化物双催化：优选的环己烯至1,2-环氧环己烷的好氧环氧化

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The CoMo hollow bimetallic oxide has been exploited in the aerobic epoxidation of cyclohexene containing labile allylic hydrogen atoms using ethylbenzene as a solvent. Cooperativity between Co(II) and Mo(VI) sites consisting of Co-O-Mo or Mo-O delta- ...Co delta+ unit on hollow oxide surfaces is investigated for controlling preferred epoxidation catalysis via tandem oxygen transfer. Various characterization techniques like XRD diffraction, N-2 physisorption, TEM, and Raman, XPS, Infrared, and UV-vis spectroscopies are employed to reveal the relationship between structure of active sites and catalytic performance. Together with these comprehensive experimental and computational studies, in this unique tandem catalytic process, Co(II) sites effectively mediate the first step of the overall oxidation cycle yielding a phenylethylperoxy radical by oxygen activation [Co(II) to Co(III) -O-2(-) to phenylethyl radical and finally to a phenylethylperoxy radical]. On the other hand, Mo(VI) sites are shown to be the excellent catalytic species for the subsequent epoxidation step by the transfer of oxygen atom of the phenylethylperoxy radical to cyclohexene. Hence, a 59% epoxidation selectivity with 33% cyclohexene conversion is accomplished through the required combination of Co(II) and Mo(VI) (2:1), allowing to tune epoxidation efficiency toward higher driving forces (relative to oxygenation of allylic hydrogen atom). This remarkably different catalytic performances between Co(II) and Mo(VI) can be attributed to the stronger overall polarization ability of Mo(VI) toward sigma(star) O-O orbital of the O-O unit derived from its d-type orbitals, which helps the donor -acceptor interactions with the double bond.
机译：使用乙苯作为溶剂，在含有乙苯的环己烯的有氧环氧化的环己烯的有氧环氧化中被利用。研究了由CO-O-Mo或MO-O Delta-... Co Delta +单元组成的CO（II）和MO（VI）位点的合作，以通过串联氧转移控制优选的环氧化催化。采用各种表征技术，如XRD衍射，N-2理由，TEM和拉曼，XPS，红外和UV-VIS光谱，揭示活性位点结构与催化性能之间的关系。与这些综合实验和计算研究一起，在这种独特的串联催化过程中，CO（II）位点有效地介导总氧化循环的第一步，得到苯基乙基哌氧基的氧激活[Co（II）至Co（III）-O -2（ - ）苯基乙基，最后将苯基乙基甲氧基自由基。另一方面，通过将苯基乙基甲氧基的氧原子转移到环己烯的氧原子转移，Mo（VI）位点显示出作为后续环氧化步骤的优异催化物质。因此，通过Co（II）和Mo（5i）（2：1）的所需组合来完成具有33％环己烯转化率的59％的环氧化选择性，允许将环氧化效率调节较高驱动力（相对于烯丙基氢的氧合原子）。 CO（II）和Mo（VI）之间的这种显着不同的催化性能可归因于莫（vi）朝向Sigma（星）OO轨道的莫（VI）的较强的整体偏振能力有助于供体 - 感染者与双键相互作用。

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