Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

The results of catalytic decomposition of N₂O over mixed oxide catalysts obtained by calcination of layered double hydroxides (LDHs) are summarized. Mixed oxides were prepared by thermal treatment (500 °C) of coprecipitated LDH precursors with general chemical composition of M^II_1-xM^III_x(OH)₂(CO₃)_x/2·yH₂O, where M^II was Ni, Co, Cu and/or Mg, M^III was Mn, Fe and/or Al, and the M^II/M^III molar ratio was adjusted to 2. The influence of chemical composition of the M^II-M^III mixed oxide catalysts on their activity and stability in N₂O decomposition was examined. The highest N₂O conversion was reached over Ni-Al (4:2) and Co-Mn-Al (4:1:1) catalysts. Their suitability for practical application was proved in simulated process stream in the presence of O₂, NO, NO₂ and H₂O. It was found that N₂O conversion decreased with increasing amount of oxygen in the feed. The presence of NO in the feed caused a slight decrease in N₂O conversion. A strong decrease in the reaction rate was observed over the Ni-Al catalyst in the presence of NO₂ while no N₂O conversion decrease was observed over the Co-Mn-Al catalyst. Water vapor inhibited the N₂O decomposition over all tested catalysts. The obtained kinetic data for N₂O decomposition in a simulated process stream over the Co-Mn-Al catalyst were used for a preliminary reactor design. The packed bed volume necessary for N₂O emission abatement in a HNO₃ production plant was calculated as 35 m³ for waste gas flow rate of 30 000 m³ h^-1.

Keywords: Nitrous oxide; Catalytic decomposition; Mixed oxides; Layered double hydroxides; Inhibition.

References: 52 live references.