Niobium oxynitride

Djega-Mariadassou and co-workers (67) reported that a long induction period preceded the simultaneous reduction and carburization steps in the synthesis of NbC from the TPRe of niobium oxide with CH4/4H2. To avoid the long induction period, different catalysts were incorporated into the initial Nb205 and were treated with CH4/4H2 mixtures at relatively low carburization temperatures. In the presence of catalysts of methane decomposition (Ni and Rh), they were able to eliminate the induction period and fee 5-NbC with superficial carbon contamination and surface areas of 11-18 m /g were obtained. When a NiMo catalyst was mixed with Nb205 and carburized with a CH4/4H2 mixture gas, 5-NbC with a surface area of 50 m /g and large amounts of carbon contamination was produced. They also synthesized 5-NbC with surface areas of 27-49 m /g from the carbonization of niobium oxynitrides, which were prepared from the nitridation of niobium oxide with pure ammonia at 923 K. 

Antonelli and co-workers have recently demonstrated that room temperature stoichiometric ammonia synthesis is possible with their mesoporous titanium and niobium oxide catalysts. In this study, they proposed that the ammonia species are formed via the reaction activated nitrogen with the underlying moisture of the support. Reversible, inter-conversion of and NH2 species via exposure to moist air for aluminophosphate oxynitride catalysts has been observed by FTIR and XPS by Marquez and co-workers. There has been a lot of interest in the literature in the development of novel routes for the low temperature stoichiometric conversion of nitrogen to ammonia, e.g.. However, in principle this could be realised by the nitridation of Li, followed by hydrolysis, although the kinetics would be very slow. 

Alkaline earth tantalum-niobium-titanium oxynitrides [22-25,39-42]... 

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