Ruthenium(0) Nanoclusters Stabilized by a Nanozeolite Framework: Isolable, Reusable, and Green Catalyst for the Hydrogenation of Neat Aromatics under Mild Conditions with the Unprecedented Catalytic A

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• 作者：Mehmet Zahmakı ; ran ; Yalı ; n Tonbul ; Saim zkar
• 刊名：Journal of the American Chemical Society
• 出版年：2010
• 出版时间：May 12, 2010
• 年：2010
• 卷：132
• 期：18
• 页码：6541-6549
• 全文大小：416K
• 年卷期：v.132,no.18(May 12, 2010)
• ISSN：1520-5126

文摘

The hydrogenation of aromatics is a ubiquitous chemical transformation used in both the petrochemical and specialty industry and is important for the generation of clean diesel fuels. Reported herein is the discovery of a superior heterogeneous catalyst, superior in terms of catalytic activity, selectivity, and lifetime in the hydrogenation of aromatics in the solvent-free system under mild conditions (at 25 °C and 42 ± 1 psig initial H₂ pressure). Ruthenium(0) nanoclusters stabilized by a nanozeolite framework as a new catalytic material is reproducibly prepared from the borohydride reduction of a colloidal solution of ruthenium(III)-exchanged nanozeolites at room temperature and characterized by using ICP-OES, XRD, XPS, DLS, TEM, HRTEM, TEM/EDX, mid-IR, far-IR, and Raman spectroscopy. The resultant ruthenium(0) nanoclusters hydrogenate neat benzene to cyclohexane with 100% conversion under mild conditions (at 25 °C and 42 ± 1 psig initial H₂ pressure) with record catalytic activity (initial TOF = 5430 h⁻¹) and lifetime (TTO = 177200). They provide exceptional catalytic activity not only in the hydrogenation of neat benzene but also in the solvent-free hydrogenation of methyl substituted aromatics such as toluene, o-xylene, and mesitylene under otherwise identical conditions. Moreover, they are an isolable, bottleable, and reusable catalyst in the hydrogenation of neat aromatics. When the isolated ruthenium(0) nanoclusters are reused, they retain 92% of their initial catalytic activity even for the third run in the hydrogenation of neat benzene under the same conditions as those of the first run. The work reported here also includes (i) far-infrared spectroscopic investigation of nanozeolite, ruthenium(III)-exchanged-nanozeolite, and ruthenium(0) nanoclusters stabilized by a nanozeolite framework, indicating that the host framework remains intact after the formation of a nanozeolite framework stabilized ruthenium(0) nanoclusters; (ii) the poisoning experiments performed by using tricyclohexylphosphine (P(C₆H₁₁)₃) and 4-ethyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane PC₆H₁₁O₃ to examine whether the ruthenium(0) nanoclusters are encapsulated in the cages or supported on the external surface of nanozeolite; (iii) a summary section detailing the main findings for the “green chemistry”; and (iv) a review of the extensive literature of benzene hydrogenation, which is also tabulated as part of the Supporting Information.