Thermal stability and repartition of potassium promoter between the support and active phase in the K-Co2.6Zn0.4O4|α-Al2O3 catalyst for N2O decomposition: Crucial role of activation temperature on catalytic performance

Optimization of cesium and potassium promoter loading in alkali-doped Zn0.4Co2.6O4|Al2O3 catalysts for N2O abatement

“…This value is characteristic of Cs atom desorption from the cobalt spinel surface at low coverages as shown and discussed in our previous paper [12]. In the case of potassium the desorption process is more complex as the Arrhenius plot reveals two desorption energies of 2.6 and 1.2 eV (at low temperature, shown in [8]). They can be associated with potassium desorption from the cobalt spinel phase and the alumina support.…”

“…1, as an example. Apart from the dominant diffraction peaks due to the a-Al 2 O 3 support, several weaker diffraction lines at 2H = 31.3°; 36.9°; 44.9°; 55.7°; 59.5°; 65.4°, corresponding to the (220), (311), (400), (422), (511) and (440) reflection planes of the cobalt spinel phase, are clearly visible [8]. No apparent changes in the XRD patterns were observed upon alkali doping of the samples, indicating that the spinel active phase remains essentially intact upon the alkali promotion.…”

“…The obtained sample was dried at 120°C for 1 h, and then calcined at 500°C for 4 h. The catalyst was next doped with alkali (K or Cs) by incipient wetness impregnation with an aqueous solution of K 2 CO 3 (POCH, pure p.a.) or Cs 2 CO 3 (Aldrich) with concentrations corresponding to the surface loadings of potassium and cesium in the range of 0-10 atoms K/nm 2 and 0-6 atoms Cs/nm 2 [4,8,11,12]. Then, the cycle of drying and calcination was repeated.…”

“…However, since the alkali promoter loading is crucial for the deN 2 O performance of the catalyst, and both the under-and the over-doping lead to pronounced deterioration of the activity, the alkali promotion level must be carefully adjusted for a given catalyst. This problem is becoming more subtle in the case of supported catalysts, since the promoter may be dispersed not only on the active phase but also on the carrier surface [8]. To resolve this problem, a series of potassium and cesium doped supported Zn 0.4 Co 2.6 O 4 |Al 2 O 3 catalysts was prepared and tested in the N 2 O decomposition.…”

“…The catalytic performance of Co 3 O 4 can be modified by bulk doping with transition metal cations (such as Zn, Ni, Cu, Mn, Fe) [5][6][7][8][9][10] and surface doping with alkali dopants (Na, K, Cs) [3,8,[11][12][13]. Addition of alkali results in a substantial lowering of the reaction temperature window, making such catalytic system potentially suitable for the low temperature deN 2 O process [11].…”