The role of support in formation of the manganese–bismuth oxide catalyst for synthesis of nitrous oxide through oxidation of ammonia with oxygen

Abstract

BET, XRD, XPS, and TPR by hydrogen were used for investigation of supported Mn–Bi oxide catalysts for ammonia oxidation into nitrous oxide. The catalysts were synthesized by impregnation of γ-, α-Al 2O 3 and SiO 2 with solutions of manganese and bismuth nitrates. The character of phase transformations, surface concentration, and state of the active component were shown to depend on the nature of the support. The sequence stabilization of active constituents of the Mn–Bi–O/ α-Al 2O 3 catalyst and types of the stabilized species were determined. The activity of the Mn–Bi–O supported catalysts calcined at 400 °C was established to equal 95–97% and to be practically independent of the support nature, while the activity decreased with elevation of the calcination temperature. The Mn–Bi–O/ α-Al 2O 3 catalysts exhibited the highest selectivity to N 2O (84.4%) under identical conditions. The correlation between the Mn 3+/Mn δ+ (2< δ<3) ratio in the catalyst and the selectivity to N 2O was revealed.