Dehydrogenation of methylcyclohexane to toluene over partially reduced silica-supported Pt-Mo catalysts

• Dehydrogenation of methylcyclohexane on partially reduced Pt/MoO2-SiO2 catalysts.
• High active phase dispersion and acidity with lowest coke formation: best activity.
• High Mo content causes the formation of Pt(core)-Mo(shell) structure: low activity.

A series of bifunctional Pt/Mo(x)-SiO2 catalysts were investigated in the context of the hydrogen storage using the methylcyclohexane (MCH)-toluene-hydrogen cycle. The performance of partially reduced catalysts for hydrogen production was evaluated in the MCH dehydrogenation reaction carried out in a fixed-bed flow reactor at 673 K and total hydrogen pressure of 2.2 MPa. The catalysts with different acidity and Mo loading (4.1–12.7 wt.%) were prepared by impregnation of the calcined Mo(x)-SiO2 samples with Pt precursor. The oxide catalyst precursors were characterized by chemical analysis (ICP-AES), N2 physisorption at 77 K, X-ray diffraction (XRD), Raman spectroscopy and temperature-programmed reduction (H2-TPR) techniques whereas the partially reduced samples were characterized by temperature-programmed adsorption of ammonia (TPD-NH3), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The catalyst having optimized Mo loading (8.0 wt.%) was the most active and its best catalytic performance was attributed to the high dispersion of MoO2 and Pt° phases and its lowest deactivation by coke formation. The activity drop of the catalysts having larger Mo loading (10.6 and 12.7 wt.%) was linked with formation of MoOx-Pt core-shell nanoparticles, as confirmed by HRTEM.

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