Preparation and characterization of low-temperature nano-crystalline cubic molybdenum carbides and insights on their structures

Direct conversion of precursors formed by drying mixtures of ammonium heptamolybdate (AHM) and sucrose solutions to nano-crystalline cubic molybdenum carbides by temperature-programmed reaction (TPR) with H-2 has been studied at low temperature (673 K). The precursors prepared with AHM and sucrose were able to produce nano-crystalline domains of cubic molybdenum carbide which seemed to show carbon vacancies affecting the intensity of the signals (2 0 0) and (2 2 0) of the X-ray powder diffraction patterns. The number of carbon vacancies was affected by the time the precursor spent at 673 K; the longer the time at this temperature, the higher the carbon vacancies observed by reduction of the intensity of the (2 0 0) signal of the X-ray diffraction pattern. The nano-crystalline molybdenum carbides prepared showed activity for the hydrogenation of toluene at 473 K to selectively produce methyl-cyclohexane. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.