Evaluation of the inhibiting effect of H2O, O2, and NO on the performance of laboratory and pilot K-ZnxCo3-xO4 catalysts supported on α-Al2O3 for low-temperature N2O decomposition

Abstract The K-ZnxCo3-xO4 catalyst supported on α-Al2O3 for N2O decomposition was investigated in terms of its resistance towards typical contaminants (O2, H2O, and NO) present in the nitric acid plant tail gases. The catalyst synthesized in laboratory-scale was thoroughly characterized by means of X-ray μ-tomography, XRF, XRD, and SEM/TEM/EDX. The impact of contaminants such as O2, H2O, and NO on the N2O conversion of the catalyst was examined and quantified by kinetic and thermodynamic modeling. The mechanism of inhibition involving local (active site blocking) and global (modification of the spinel electronic properties by electrophilic NOx adspecies) effects was proposed. The strongest inhibition of NO was associated with its facile reactivity with surface O intermediates produced during N2O decomposition. The resultant NO2 and NO3 surface adducts are stable at the catalyst surface up to 550 °C. For the pilot catalyst, the effect of contamination was the same in nature as for the laboratory sample, however, the observed quantitative differences were associated with the changes in the shape of the spinel nanocrystals constituting the catalyst active phase. The obtained results provide rationales for designing and preparation of the robust deN2O catalyst with enhanced resistivity to poisoning.