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

Abstract

Dehydrogenation of methylcyclohexane (MCH) has been carried out on a variety of partially reduced Mo(x)–SiO2 (x: Mo/Si molar ratio×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 673K and 2.2MPa of total hydrogen pressure. The effect of Mo molar loading on the structure of the catalysts was studied by N2 physisorption, TPR, XRD, UV–vis DRS, NH3-TPD, XPS and TEM techniques. From the activity tests, it was concluded that Mo10–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.