The effect of partial Pt substitution by Ir on the catalytic response of bimetallic Pt-Ir/ZSM-5 (Pt/Ir = 1) catalyst in the liquid-phase hydrodeoxygenation (HDO) of phenol was investigated. To evaluate the catalyst intrinsic activity, the ZSM-5 supported Pt, Ir and Pt + Ir catalysts were prepared with similar total metal loading (ca. 3 wt. %) and acidity. The catalysts were characterized by several physical and chemical techniques and tested in the HDO of phenol reaction carried out in a batch reactor at T = 200 degrees C under H-2 pressure of 3.0 MPa. For all the catalysts, the phenol transformation mainly proceeds via hydrogenation + dehydration (HYD reaction route) leading to cyclohexane as the main product (selectivity 60-96%). Partial substitution of Pt by Ir in catalyst formulation (Pt50-1r50/ZSM-5) enhances both activity and selectivity toward O-free products. This was associated to Ir surface enrichment (from HRTEM). The Ir/ZMS-5 and Pt50-1t50/ZMS-5 catalysts having well dispersed Ir nanoparticles were more selective toward dehydration than Pt/ZSM-5 having Pt species with a broad size distribution range. The catalyst activity-structure correlation suggests that the dehydration of cyclohexanol (intermediate product) can occur at the interface between the metal and acid sites of the support..
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