Cobalt Spinel Catalyst for N₂O Abatement in the Pilot Plant Operation–Long-Term Activity and Stability in Tail Gases

Abstract

The catalytic activity of a doubly promoted K/Zn–Co3O4 spinel catalyst in the deN2O reaction was tested for 10 weeks in a nitric acid pilot plant. A charge of 15 kg of the catalyst was synthesized via precipitation method, dried, calcined, and formed into 5 × 5 mm tablets. The catalytic tests were carried out in the wide range of process parameters: 320 < T < 425 °C; 80 < VRG < 180 N m3·h–1, 3 < p < 9.5 bar(a). During the operation the chemical composition of tail gases from ammonia oxidation reactor outlet varied within the following range: 300 < CN2O < 1500 ppm(v); 30 < CNOx < 3000 ppm(v); 10000 < CO2 < 50000 ppm(v); 1000 < CH2O < 18000 ppm(v); N2 – rest. In these conditions, the N2O conversion was above 70% at 400 °C and was stable in time. Fresh and used catalysts were compared through detailed structural and morphological characterization (XRD, Raman, BET, SEM, XPS, H2-TPR), and their deN2O performance was verified in laboratory conditions. Long-term catalytic tests proved persistent stability of the catalyst with respect to its high activity, composition, structure, and morphology.