REACTION MECHANISM OF DIRECT PHENOL SYNTHESIS FROM BENZENE AND MOLECULAR OXYGEN ON Re_(10)N2-Cluster/HZSM-5 CATALYSTS

摘要

We have found a novel N-interstitial Re_(10)-cluster catalyst supported on HZSM-5, which is active and highly selective for direct phenol synthesis from benzene using O2 as an oxidant. Phenol selectivity was tremendously high as 87.7-93.9% at 553 K with a maximum benzene conversion of 9.9%. NH3 produced the active Re cluster. In-situ time-resolved XAFS successfully characterized the dynamic structural changes between the active Re cluster and inactive Re monomers, the structural transformations balancing during the steady-state phenol synthesis. The structural behavior of the supported Re species and the pore-size effect of HZSM-5 are suggested to be the major issues for the high phenol selectivity on the Re/HZSM-5 catalyst.