Novel Re-Cluster/HZSM-5 Catalyst for Highly Selective Phenol Synthesis from Benzene and O2: Performance and Reaction Mechanism

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• 作者：Mizuki Tada ; Rajaram Bal ; Takehiko Sasaki ; Yohei Uemura ; Yasuhiro Inada ; Satoka Tanaka ; Masaharu Nomura ; Yasuhiro Iwasawa
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：July 12, 2007
• 年：2007
• 卷：111
• 期：27
• 页码：10095 - 10104
• 全文大小：345K
• 年卷期：v.111,no.27(July 12, 2007)
• ISSN：1932-7455

文摘

This paper reports the catalytically active structure, its structural transformation and dynamics, and the reactionmechanism for direct phenol synthesis from benzene and molecular oxygen on a novel N-interstitial Re₁₀-cluster/HZSM-5 catalyst, which exhibited remarkable phenol selectivities of 91.6-93.9% at 1.7-9.9%conversions in pulse reactions and 82.4-87.7% at 0.8-5.8% conversions in steady-state reactions. The activeN-interstitial Re₁₀ cluster for the direct phenol synthesis with O₂ as an oxidant was produced by NH₃ at 553K and the phenol synthesis proceeded with the low activation energy of 24 kJ mol^-1. The active Re₁₀ clusterwas converted to inactive Re monomers, while NH₃ reproduced the active Re₁₀ cluster under the reactionconditions. It was found by means of in situ time-resolved XAFS and DFT calculations that the catalyticphenol synthesis proceeded in conjunction with the structural transformation between the Re₁₀ clusters andthe Re monomers. The isosbestic points in energy-dispersive XANES spectra indicated a direct conversionof the Re₁₀ cluster to the Re monomers without any unfavorable metastable intermediates. The benzene oxidationis proposed to proceed via oxygen addition to a C atom of benzene to form an oxygen-added intermediatewith a sp³ carbon atom in the benzene ring and subsequent insertion of the oxygen to the C-H bond on theRe₁₀ cluster.