Overcoming the Engineering Constraints for Scaling-Up the State-of-the-Art Catalyst for Tail-Gas N₂O Decomposition

Abstract

An efficient process is reported for preparing a state-of-the-art Fe-ferrierite catalyst for N₂O decomposition under industrial tail-gas conditions. In the synthesis procedure, we evaluate the very demanding constraints for scale-up; i.e. large reactor volumes are typically needed, and long processing times and considerable amounts of wastewater are generated. The proposed synthesis minimizes the amount of water used, and therefore, the amount of produced wastewater is minimal; in this approach there is no liquid residual water stream that would need intensive processing. This has remarkable benefits in terms of process design, since the volume of equipment is reduced and the energy-intensive filtration is eliminated. This route exemplifies the concept of process intensification, with the ambition to re-engineer an existing process to make the industrial catalyst manufacture more sustainable. The so-obtained catalyst is active, selective, and very stable under tail-gas conditions containing H₂O, NO, and O₂, together with N₂O, keeping a high conversion during 70 h time on stream at 700 K, with a decay of 0.01%/h, while the standard reference catalyst decays at 0.06%/h; hence, it deactivates 6 times more slowly, with ∼5% absolute points of higher conversion. The excellent catalytic performance is preliminarily ascribed to the differential speciation.