Three transition metal nitrides, viz. VN, Mo2N, and W 2N were synthesized and characterized; their catalytic activities for NO reduction with H2 were evaluated. The as-prepared nitrides were pure in phase and ionic binding in nature. Their activities for NO reduction with H2 ranked in the order of W2N > Mo2N > VN. Characterization by XRD, XPS, and H2-TPR revealed that oxygen generated during NO dissociation was entirely captured by VN, and that VN acted as a reactant rather than a catalyst for NO reduction. Catalytic cycles could be established over the Mo2N and W2N catalysts; the nitrides catalyzed the dissociation of NO, while the oxygen generated during NO dissociation was partly reduced by H2 and partly incorporated into the nitride lattice. Deactivation of the catalysts was due to the gradual oxidation of the nitrides. By regulating H2 concentration in the feed, one can retain the active Mo2N and W2N phases by minimizing the presence of surface oxygen.
Scopus Subject Areas
- Process Chemistry and Technology
- NO reduction