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

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), N-2 physisorption at 77 K, X-ray diffraction (XRD), Raman spectroscopy and temperature programmed reduction (H-2-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 degrees 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. (C) 2016 Elsevier B.V. All rights reserved.