Active Re-Cluster on HZSM-5 for the Phenol Synthesis

The Re monomer was completely inactive for the mixture of benzene and O2. NH3 treatment of the Re monomers at 553 K generated the catalyhc achvity. After around 30 min of the NH3 treatment, phenol synthesis activity appeared and the phenol formahon rate dramatically increased between 40 and 60 min of the NH3 treatment, followed by a gentle rate rise upon further treatment The reaction rate saturated at 3.75 x 10 s after 120min. Further NH3 treatment longer than 120 min did not improve the catalyhc activity. Notably, the phenol selechvity kept almost constant (90.1-93.9%) during the NH3 treatment at 553 K. 

All spectra were Fourier-transformed at fc = 30-160nm and fitted in an R space of R = 0.10-0.32nm. 

the CN (2.8) of the Re-Re bonds means that part of the Re species was clus-terized to a Re octahedron framework. Thus, the sharp increase in catalytic activity by the 40-60min NH3 treatment is suggested to be due to formation of a Re,5 cluster achve for the selechve oxidation [73]. 

Various structures involving the Re octahedral framework were examined by DFT structural ophmizahon. All ah initio calculations were performed using a commercially available density funchonal code (Material Studio Dmol3 ver3.0, Accelrys, US A), where exchange-correlation interaction was treated by the Perdew- 

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