Abstract
Ta3-xMxNy (M=Re, Fe, Co; x=0, 0.25, 0.5, 1) materials with different microstructural features (e.g. surface area) were successfully prepared using different synthesis techniques. The dependence of nitrogen transfer properties upon tantalum nitride microstructure and its chemical composition was evaluated using the ammonia synthesis with a H2/Ar feedstream (a reaction involving lattice nitrogen transfer). It was shown that nitrogen reactivity for tantalum nitride is more dominated by lattice nitrogen stability rather than microstructural properties. In the case of non-doped tantalum nitride, only a limited improvement of reactivity with enhanced surface area was observed which demonstrates the limited impact of microstructure upon reactivity. However, the nature of the transition metal dopant as well as its content was observed to play a key role in the nitrogen transfer properties of tantalum nitride and to impact strongly upon its reactivity. In fact, doping tantalum nitride with low levels of Co resulted in enhanced reactivity at lower temperature.
Highlights
Nitrogen is of central importance in many industrial processes with nitrogen containing compounds being used in numerous commercial products including synthetic fertilizers, dyes, explosives, and resins [1]
If the regeneration of nitrogen depleted phases during reaction was realisable using dinitrogen directly, materials operating through processes akin to the Mars-van Krevelen (MvK) mechanism could be considered as means to by-pass the use of activated nitrogen building blocks such as ammonia itself in multistage processes
In this work we have explored the possibility to alter the reactivity of Ta3N5 by: (i) modification of the structural and textural properties of Ta3N5, (ii) alteration of the reactivity of tantalum nitride lattice nitrogen by doping with transition metals
Summary
Nitrogen is of central importance in many industrial processes with nitrogen containing compounds being used in numerous commercial products including synthetic fertilizers, dyes, explosives, and resins [1]. If the regeneration of nitrogen depleted phases during reaction was realisable using dinitrogen directly, materials operating through processes akin to the MvK mechanism could be considered as means to by-pass the use of activated nitrogen building blocks such as ammonia itself in multistage processes. These routes would use the lattice nitrogen component as the source of pre-activated reactant.
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