Structure and properties of molybdenum oxide nitrides as model systems for selective oxidation catalyst

<p>Abstract</p> <p>Molybdenum oxide nitride (denoted as Mo(O,N)₃) was obtained by ammonolysis of α-MoO₃with gaseous ammonia. Electronic and geometric structure, reducibility, and conductivity of Mo(O,N)₃were investigated by XRD, XAS, UV-Vis spectroscopy, and impedance measurements. Catalytic performance in selective propene oxidation was determined by online mass spectrometry und gas chromatography. Upon incorporation of nitrogen, Mo(O,N)₃maintained the characteristic layer structure of α-MoO₃. XRD analysis showed an increased structural disorder in the layers while nitrogen is removed from the lattice of Mo(O,N)₃at temperatures above ~600 K. Compared to regular α-MoO₃, Mo(O,N)₃exhibited a higher electronic and ionic conductivity and an onset of reduction in propene at lower temperatures. Surprisingly, α-MoO₃and Mo(O,N)₃exhibited no detectable differences in onset temperatures of propene oxidation and catalytic selectivity or activity. Apparently, the increased reducibility, oxygen mobility, and conductivity of Mo(O,N)₃compared to α-MoO₃had no effect on the catalytic behavior of the two catalysts. The results presented confirm the suitability of molybdenum oxide nitrides as model systems for studying bulk contributions to selective oxidation.</p