Publication Catalysis 2011
F. Cardenas-Lizana, S. Gomez-Quero, N. Perret, L. Kiwi-Minsker, M. A. Keane, Catal. Sci. Technol. 2011, 1, 118.
A temp. programmed treatment of MoO3 in flowing N2 + H2 has been employed to prep. Î²-phase molybdenum nitride (Î²-Mo2N) which has been used to promote, for the first time, the catalytic hydrogenation of p-chloronitrobenzene. The redn./nitridation synthesis steps have been monitored in situ and the starting oxide, reaction intermediates and nitride product have been identified and characterized by powder X-ray diffraction (XRD), diffuse reflectance UV-vis (DRS UV-Vis), elemental anal., SEM, and BET/pore vol. measurements.
Our results demonstrate that MoO3 Î²-Mo2N is a kinetically controlled process where an initial redn. stage generates (sequentially) MoO2 and Mo as reaction intermediates with a subsequent incorporation of N to produce Î²-Mo2N. SEM anal. has established that the transformation is non-topotactic with a disruption to the platelet morphol. that characterizes MoO3 and an increase in BET area (from 1 m2/g-1 to 17 m2/g-1). Moreover, temp. programmed desorption measurements have revealed a significant hydrogen uptake (0.71 Î¼mol m-2) on Î²-Mo2N.
This has been exploited in the hydrogenation of p-chloronitrobenzene where p-chloroaniline was generated as the sole product with an assocd. rate const. (k = 2.0 min-1) that is higher than values recorded for supported transition metals. Our study establishes the reaction mechanism involved in the synthesis of Î²-Mo2N and demonstrates its viability to promote selective -NO2 group redn. as an alternative sustainable, high throughput route to com. important haloamines.