Dehydrogenation of methylcyclohexane to toluene over partially reduced Mo-SiO2 catalysts

Dehydrogenation of methylcyclohexane (MCH) has been carried out on a variety of partially reduced Mo(x) SiO2 (x: Mo/Si molar ratio x 100) catalysts differing by the molybdenum loading and which were prepared by sol-gel method. The objective was to maximize hydrogen production by monitoring the selectivity toward toluene formation. The MCH dehydrogenation was carried out in a down-flow reactor at 673 K and 2.2 MPa of total hydrogen pressure. The effect of Mo molar loading on the structure of the catalysts was studied by N-2 physisorption, TPR, XRD, UV vis DRS, NH3-TPD, XPS and TEM techniques. From the activity tests, it was concluded that Mo I 0 SiO2 catalyst, with Mo molar ratio of 10, exhibited the highest activity and the largest yield of toluene thanks to the existence of a good compromise between reduced Mo species and bulk MoO3. An increase of the molybdenum loading from 10 to 15 (molar ratio) led to: (i), the formation of non-active MoO3 phase; (ii), a low stable molybdenum species during on-stream operation; and (iii), a large coke formation due to an increase of the catalyst acidity. (C) 2015 Elsevier B.V. All rights reserved.