Reforming of cyclohexane and n-heptane on nanosized Mo2C and W2C obtained by the carbidization of WO3 and MoO3 activated by vibrationally excited molecules of hydrogen

Abstract

The catalytic activity of nanosized powders of hexagonal α-Mo2C and α-W2C with average particle size of 17 nm obtained by thermal carbidization of MoO3 and WO3 oxides in the flow of methane–hydrogen mixture, preliminarily activated by the vibrationally excited molecules of hydrogen was studied. Amorphous powders obtained by this method exhibit high activity associated with structural features. This was a crucial factor for the low-temperature synthesis of nanosized carbides (500 °C for Mo2C and 600 °C for W2C). It was shown that nanosized carbides exhibit high catalytic activity in cyclohexane dehydrogenation yielding benzene, and cyclodehydrogenation of n-heptane yielding toluene. The analysis of the obtained data allow to conclude that the observed drastic difference in activity and selectivity of the carbides with nano- and microsized particles is conditioned by the effect of nanocarbides particle size and defects of structure that have been formed during low-temperature synthesis. The synthesized carbide catalysts are stable in air and keep their catalytic activity over a long period.