The influence of modifiers on the activity of Fe2O3 catalyst for high temperature N2O decomposition (HT-deN2O)

High-Temperature Abatement of N2O over FeOx/CeO2-Al2O3 Catalysts: The Effects of Oxygen Mobility

CeO2-Al2O3 oxides prepared by co-precipitation (Ce+Al) or CeOx precipitation onto Al2O3 (Ce/Al) to obtain dispersed CeO2 and samples with further supported FeOx (2.5–9.9 weight% in terms of Fe) were characterized by XRD, XPS, DDPA and Raman. Fe/Ce/Al samples with lower surface concentrations of Fe3+ were substantially more active in N2O decomposition at 700–900 0C. It was related to higher oxygen mobility, as estimated from 16O/18O exchange experiments and provided by preferential exposing of (Fe-)Ce oxides. Stabilization of some Ce as isolated Ce3+ in Fe-Ce-Al mixed oxides dominating in the bulk and surface layers of Fe/(Ce + Al) samples retards the steps responsible for fast additional oxygen transfer to the sites of O2 desorption.

Two-Stage Catalytic Abatement of N2O Emission in Nitric Acid Plants

Different variants for abatement of N2O emission from nitric acid plants with the use of catalysts developed at Łukasiewicz-INS were analyzed. Activity tests on a pilot scale confirmed the high activity of the studied catalysts. A two-stage catalytic abatement of N2O emission in nitric acid plants was proposed: by high-temperature decomposition in the nitrous gases stream (HT-deN2O) and low-temperature decomposition in the tail gas stream (LT-deN2O). The selection of the optimal variant for abatement of N2O emission depends on the individual characteristics of the nitric acid plant: ammonia oxidation parameters, construction of ammonia oxidation reactor and temperature of the tail gas upstream of the expansion turbine. It was shown that the combination of both deN2O technologies, taking into account their technological constraints (dimensions of the catalyst bed), allows for a greater abatement of N2O emission, than the use of only one technology. This solution may be economically advantageous regarding the high prices of CO2 emission allowances.

FeOx/Al2O3 catalysts for high-temperature decomposition of N2O under conditions of NH3 oxidation in nitric acid production

The δ and θ Al₂O₃ phases well stabilized Fe(iii) in T_d or O_h coordination, which were identified as the active species in high temperature decomposition of N₂O in a complex gas mixture produced by oxidation of ammonia.

MeOx/Al2O3 and MeOx/CeO2 (Me = Fe, Co, Ni) catalysts for high temperature N2O decomposition and NH3 oxidation

Efficient oxygen transfer through Me–CeO₂ interface explains higher activity of MeO_x/CeO₂ (Me = Fe, Co, Ni) samples in deN₂O and NH₃ oxidation compared with MeO_x/Al₂O₃ ones.