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

The catalytic activity of a doubly promoted K/Zn-Co3O4 spinel catalyst in the deN(2)O 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 x 5 mm tablets. The catalytic tests were carried out in the wide range of process parameters: 320 < T < 425 degrees C; 80 < V-RG < 180 N m(3).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 < C-N2O < 1500 ppm(v); 30 < C-NOx < 3000 ppm(v); 10000 < C-O2 < 50000 ppm(v); 1000 < C-H2O < 18000 ppm(v); N-2 - rest. In these conditions, the N2O conversion was above 70% at 400 degrees C and was stable in time. Fresh and used catalysts were compared through detailed structural and morphological characterization (XRD, Raman, BET, SEM, XPS, H-2-TPR), and their deN(2)O 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.